EPA-600/2-75-027
November 1975
Environmental Protection Technology Series
Mr'THE-i
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EPA-600/2-75-027 c.
November 1975
SEWER FLOW MEASUREMENT - A STATE-OF-THE-ART ASSESSMENT
by
Philip E. Shelley
George A."Kirkpatrick
EG&G WASHINGTON ANALYTICAL SERVICES CENTER, INC.
Rockville, Maryland 20850
Contract No. 68-03-0426
Project Officer
David J. Cesareo
Storm and Combined Sewer Section (Edison, N.J.)
Wastewater Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
EERU-TIX
RECEIVED
APR 51989
EERU-TIX
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75-0*1
DISCLAIMER
This report has been reviewed by the Municipal Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for
publication. Approval does not signify that the contents necessarily
reflect the views and policies of the U.S. Environmental Protection
Agency, nor does mention of trade names or commercial products
constitute endorsement or recommendation for use. i
e&i 2
XIT-UH33
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FOREWORD
Man and his environment must be protected from the adverse effects
of pesticides, radiation, noise, and. other forms of pollution, and
the unwise management of solid waste. Efforts to protect the
environment require a focus that recognizes the interplay between
the components of our physical environment—air, water, and land.
The Municipal Environmental Research Laboratory contributes to this
multidisciplinary focus through programs engaged in
• studies on the effects of environmental contaminants
on the biosphere, and
• a search for ways to prevent contamination and to
recycle valuable resources.
The deleterious effects of storm and combined sewer overflows upon
the nation's waterways have become of increasing concern in recent
times. Efforts to alleviate the problem depend upon accurate
characterization of these flows in both a quantity and quality sense.
This report presents a state-of-the-art survey of flow measuring
devices and techniques that either are, or might be, appropriate for
the quantitative measurement of stormwater and combined sewer flows
as well as other wastewater discharges, and will be of interest to
those who have a requirement for the measurement of such flows.
iii
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ABSTRACT
A brief review of the characteristics of storm and combined sewer
flows is given, followed by a general discussion of the need for
such flow measurement, the types of flow data required, and the
time element in flow data. A discussion of desirable flow meas-
uring equipment characteristics presents both equipment requirements
as well as desirable features and includes an equipment evaluation
sheet that can be used for a particular application.
A compendium of over 70 different generic types of primary flow
measurement devices, arranged according to the fundamental physical
principles involved, is presented along with evaluations as to their
suitability for measurement of storm or combined sewer flows. To
illustrate the implementation of the physical principles, a number
of commercially-available devices for flow measurement are briefly
de'scribed.
A review of selected U.S. Environmental Protection Agency project
experience in flow measurement is presented along with a summary of
current and on-going research efforts. Some thoughts on future areas
of research and development are also given. This report was submitted
in fulfillment of Contract Number 68-03-0426 under the sponsorship of
the Office of Research and Development, U.S. Environmental Protection
Agency. Work was completed in December 1974.
IV
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CONTENTS
Section Page
I CONCLUSIONS ..... ............. . . 1
II RECOMMENDATIONS ... ..... . ......... 3
J . '
III INTRODUCTION . . . ........ . ...... . 5
Purpose and Scope ................. 6
General Nature of Storm and Combined
Sewer Flows ................... 7
Need for Flow Measurement ..... ..... ... 13
Types of Flow Data Required . . .......... 17
IV THE TIME ELEMENT IN FLOW DATA ..... ...... 19
Importance of the Time Element .......... 19
Continuous Recording of Flows ........... 20
Noncontinuous Flow Data .............. 21
V DESIRABLE EQUIPMENT CHARACTERISTICS ...... . . 23
Primary Design Goals ............... 23
Secondary Design Goals ..... . ........ 24
Evaluation Parameters ..... ..... ..... 25
VI METHODS OF FLOW DETERMINATION ...... ..... 28
General . ...... ... ......... ... 28
Site Selection .... ........ . ..... 29
Gravimetric .................... 32
Volumetric . . ................. . 32
Differential Pressure . . . . ........... 36
Variable Area ....... ..... ....... 52
Head - Area .......... . . ........ 53
Flow Velocity . . ................. 99
Force - Displacement ........ ..... . . 112
Force - Momentum . .......... ...... 121
Thermal ............... . ...... 123
Electromagnetic ..... ............. 128
Acoustic ................ ..... 132
Dilution ................. .... 138
Other ............... . . . ..... 141
Doppler ... ............ ....... 143
Optical ............. .........
v
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CONTENTS (Cont'd)
Section
VII
VIII
Page
Electrostatic 145
Nuclear Resonance 147
Miscellaneous 147
Secondary Devices 148
Discussion ...... 150
REVIEW OF COMMERICALLY AVAILABLE EQUIPMENT .... 154
Alphabetical List of Manufacturers 156
SELECTED PROJECT EXPERIENCE 376
Characterization and Treatment of Combined
Sewer Overflows 376
Stream Pollution and Abatement From Combined
Sewer Overflows - Bucyrus, Ohio 378
Engineering Investigation of Sewer Overflow
Problem - Roanoke, Virginia 379
Combined Sewer Overflow Abatement Alternatives -
Washington, D.C 380
Urban Runoff Characteristics .... 381
Storm and Combined Sewer Pollution Sources and
Abatement - Atlanta, Georgia 382
Stormwater Problems and Control in Sanitary
Sewers - Oakland and Berkeley, Calif 383
Dispatching System For Control of Combined
Sewer Losses 384
Preconstruction Evaluation of Combined Sewage
Detention Facilities 385
Urban Storm Runoff and Combined Sewer Overflow
Pollution - Sacramento, California 386
Storage and Treatment of Combined Sewer
Overflows 387
A Thermal Wave Flowmeter for Measuring Combined
Sewer Flows 388
Wastewater Flow Measurement In Sewers Using
Ultrasound 389
Biological Treatment of Combined Sewer Overflow at
Kenosha, Wisconsin 390
Flow Augmenting Effects of Additives on Open
Channel Flows 391
Surge Facility For Wet and Dry Weather Flow
Control 392
A Portable Device For Measuring Wastewater Flow
In Sewers 393
VI
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CONTENTS (Cont'd)
Section
Page
Joint Construction Sediment Control Project .... 394
Combined Sewer Overflow Abatement Plan,
Des Moines, Iowa . . * . . 395
Computer Management of a Combined Sewer
System 395
Characterization and Treatment of Urban
Land Runoff 397
Other USEPA Projects 398
Projects by Other Federal Agencies ......... 399
Projects Outside the United States .......... 401
IX FUTURE AREAS OF RESEARCH AND DEVELOPMENT ..... 402
General Research 403
Applications Research ... 405
Demonstration Research 406
X REFERENCES . 409
Cited References ...... .... 409
Supplemental References 415
vii
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LIST OF ILLUSTRATIONS
Figure
I
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
Typical Storm Hyetograph and Hydrograph 9
Typical Vertical Velocity Profiles 12
Herschel Standard (Long) Venturi Meter Tube .... 37
Ball Flow Tube 40
Typical Flow Nozzle Installation 43
Flow Nozzle Discharging to Atmosphere 44
Head Loss of Differential Pressure Meters 47
Pradtl-Pitot Impact Tube 51
Weir Terms and Their Relationships 56
Various Sharp-Crested Weir Profiles 58
Compound Weir 60
Examples of Broad-Crested Weir Shapes .64
Type I Flume - Critical Flow Contraction Obtained
by Small Width Reduction, Horizontal Bed .... 68
Type II Flume - Critical Flow Contraction Obtained
by Large Width Reduction, Horizontal Bed .... 68
Type III Flume - Subcritical Flow Contraction
Obtained By Small Increase In Bed Elevation,
Horizontal Bed 69
Type IV Flume - Supercritical Flow Contraction
Obtained by Width Reduction and Sloping Bed ... 70
Type V Flume - Supercritical Flow Contraction
Obtained by Width Reduction and Drop in Bed ... 70
Type VI Flume - Supercritical Flow Contraction
Obtained By Steepening Slope 72
Configuration and Standard Nomenclature for
Parshall Flumes 74
Various Cross-Section Shapes of Palmer-Bowlus
Flumes 79
Diskin Measuring Device 81
Rectangular Cutthroat Flume .... 84
San Dimas Flumes 87
Elements of a Trapezoidal Supercritical
Flow Flume 89
Type HS, H, and HL Flumes 92
Isometric View of Type HS, H, and HL Flumes .... 93
Open Flow Nozzle Discharge Profiles 96
California Pipe and Trajectory Methods 98
Assembly Drawing of a Price Type AA Current
Meter 11:L
Vane Meters • • • 115
Target Meter *•*•*
Typical Hot-Tip Element Configurations 125
Vlll
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LIST OF ILLUSTRATIONS (Cont'd)
Figure
33
34
35
36
37
Components of an Electromagnetic Pipe
Flowmeter
Components of an Electromagnetic Velocity
Probe . .
Physical Arrangements of Acoustic Depth
Sensors ...... .
Physical Arrangements of Acoustic Velocity
Sensors
Chemical Dilution Methods . .
130
131
135
13,6
140
ix
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LIST OF TABLES
Table Page
1 Flow Measurement Equipment Checklist . 27
2 Flow Meter Categorization 30
3 Gravimetric Meter Evaluation (All Types) 33
4 Volumetric Meter Evaluation (All Types) 35
5 Venturi Tube Meter Evaluation 39
6 Ball Tube Meter Evaluation 42
7 Flow Nozzle Meter Evaluation 45
8 Orifice Meter Evaluation 48
9 Elbow Meter Evaluation 50
10 Slope-Area Method Evaluation 55
•ll Sharp-Crested Weir Evaluation (All Profiles) ... 62
12 Broad-Crested Weir Evaluation 66
13 Subcritical (Venturi) Flume Evaluation 73
14 Standard Parshall Flume Dimensions
and Capacities . 76
15 Parshall Flume Evaluation 77
16 Palmer-Bowlus Flume Evaluation 80
17 Diskin Device Evaluation 83
18 Cutthroat Flume Evaluation 85
19 San Dimas Flume Evaluation 88
20 Trapezoidal Flume Evaluation 91
21 Type HS, H, and HL Flume Evaluation 94
22 Open Flow Nozzle Evaluation 97
23 Float Velocity Evaluation 103
24 Tracer Velocity Evaluation 105
25 Vortex-Velocity Meter Evaluation 106
26 Eddy-Shedding Meter Evaluation 108
27 Turbine Meter Evaluation 109
28 Rotating-Element Meter Evaluation 113
29 Vane Deflection Meter Evaluation 117
30 Hydrometric Pendulum Evaluation 118
31 Target Meter Evaluation 120
32 Force Momentum Meter Evaluation 124
33 Hot-Tip Meter Evaluation 127
34 Thermal Boundary Layer Meter Evaluation 129
35 'Electromagnetic Flowmeter Evaluation 133
36 Acoustic Meter Evaluation 139
37 Dilution Method Evaluation 142
38 Doppler Meter Evaluation 144
39 Optical Meter Evaluation 146
40 Flowmeter Evaluation Summary 151
41 Comparison of Most Popular Primary Devices
or Techniques 152
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ACKNOWLEDGMENTS
The cooperation and support of the commercial manufacturers and
suppliers of flow measuring equipment and their representatives
is acknowledged with sincere thanks. They supplied information
about their current products and proposed new developments, took
time to answer questions and provide operational insights, and
made the preparation bf Section VII of this report possible, All
equipment illustrations were provided by the respective manufacturers,
and apprectiation for their use in this report is hereby acknowledged.
Appreciation must also be expressed to all of the project engineers
and research workers who took time to discuss various aspects of
their work, to share insights and field experiences, and to offer
suggestions about the use of certain equipment. '
Finally, the support of this effort by the Storm and Combined
Sewer Section (Edison, New Jersey), Wastewater Research Division,
Municipal Environmental Research Laboratory, Cincinnati, Ohio,
and especially Mr. David J. Cesareo, Project Officer, and the
other manuscript reviewers is acknowledged with gratitude.
xi
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SECTION I
CONCLUSIONS
1. A flowmeter is one tool of several that must be employed for the
characterization of a wastewater stream. Its selection must be
based upon consideration of the overall flow measurement- program
to be undertaken, the nature of the flows to be measured, the
physical characteristics of the flow measurement sites, and the
degree of accuracy required, among other factors.
2. In view of the large number of highly variable parameters asso-
ciated with the storm and combined sewer application, no single
flowmeter can exist that is universally applicable with equal .
efficacy. Some requirements are conflicting, e.g., an open drain-
age ditch versus a closed conduit deep underground, and a careful
series of trade-off studies is required in order to arrive at a
"best" selection for a particular program and site.
3. There are over 70 generic devices and methods that can be used for
determining wastewater flows, and they were reviewed and discussed.
4. The proper selection of flow measurement sites can be as important
as the selection of methods and equipment. A clear understanding
'of the data requirements and ultimate use is necessary, as is a
familiarity-with the sewer system to be examined.
5. Of the over 120 prospective manufacturers of liquid flow measuring
equipment which were contacted, none has a flow measurement product
line that is specifically designed for the storm and combined sewer
application.
6. Where large flows are to be measured with fairly high accuracy,
considerable expense in terms of initial equipment cost, site
preparation and installation, and operator training and maintenance
is involved; fifty to one hundred thousand dollars should not be
considered atypical.
7. There are measurement sites where no presently available equipment
can operate unattended for long at a high degree of accuracy
(better than ±5% of full scale).
8. The most consistently reliable flow measurement data have been
taken at sites where the equipment has been calibrated in place
over the entire range of flows anticipated.
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9. Field experience in wastewater flow measurement was reviewed, and
in most instances errors of greater than 10% seem to be the rule.
It is not at all uncommon to find readings that differ from spot
field checks by from 50 to 200 percent. Some wastewater dis-
charge data are of such poor quality as to be virtually useless.
10. Flow measurement research efforts within the United States were
reviewed. Very few of those outside the USEPA are addressed to
the storm and combined sewer problem as presented here, and it
would appear that few, if any, that are not so oriented will pro-
duce technology fall-outs that will benefit the solution of the
problem at hand.
11. The technological state-of-the-art, especially in electronics,
is advancing very rapidly at the present time, and capabilities
are emerging that until now were either impossible or prohibi-
tively expensive. Examples include improved pressure sensors,
solid state and integrated circuitry advances (and price reduc-
tions) that facilitate control and computational functions,
quartz crystal timers that offer accuracy improvements measured
in orders of magnitude, improvements in electronic recorders,
etc. As a result, both new products and improvements to old
ones are continually appearing.
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SECTION II
RECOMMENDATIONS
1. It is recommended that flow measurement accuracy requirements be
very carefully considered with an eye to optimizing the accuracy
of determination of total pollutant discharge. Very high accura-
cies over very wide ranges may not be necessary for all purposes
and will certainly be expensive to achieve.
2. Where possible, it is recommended that flow measurement equipment
be calibrated in place at the site 'where the data are to be col-
lected. Maintenance should be performed such that conditions do
not deviate greatly from those at the time of calibration.
3. Use and maintenance of complex, sophisticated flow measurement
equipment should not be entrusted to well-meaning but untrained
personnel. Proper training of operator personnel is recommended
as it will produce long-term benefits.
4. It is recommended that the flow measurement site be chosen with
great care. It can be as poor an error in judgement to choose a
site that will not yield the desired data simply because of equip-
ment availability as it is to attempt to apply the wrong equipment
at a site that is truly important.
5. , In view of the immediate requirements for storm and combined sewer
discharge data for surveys, computer model calibration and veri-
fication, infiltration/inflow studies, and the like, the most
urgent need is for suitable portable devices that are capable of
unattended operation. It is strongly recommended that a program
to develop such devices be initiated with special emphasis on:
• Automated Chemical Dilution Devices
• Ultrasonic Devices
• Hybrid Flumes
6. There has been very little opportunity to evaluate, flow measure-
ment equipment suitable for storm and combined sewer applications
in a side-by-side fashion under somewhat controlled conditions.
It is strongly recommended that a suitable facility be identified
and used to gather comparative data with emphasis on the more
promising portable devices.
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8.
9.
There are a number of flow measurement devices that have either
recently become available or are about to be introduced and that
offer considerable promise in a storm and combined sewer applica-
tion. It is recommended that a program of demonstration testing
be initiated to include such devices as:
• Venturi Meter/Flumes
• Combination Thermal Flowmeters
• High Range Open Flow Nozzles
This study was essentially limited to developments and practices
within the United States. It is recommended that a survey of
foreign research and development activities and storm and combined
sewer flow measurement practices be conducted.
Because of the burgeoning nature of the present state of the art
and increasing concern over environmental contamination caused by
storm and combined sewer discharges, this report should not be
considered a final, enduring document. It is recommended that it
be expanded and updated within two years.
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SECTION III
INTRODUCTION
Since almost the beginning of civilization, man has recognized the need
to determine liquid flow rates, quantities, or stages, and his first
efforts'-were probably directed towards survival during floods and trans-
portation by water craft. Demands for water supply, irrigation, navi-
gation, and waterpower all accentuated the need for flow measurement.
It is known that the ancient Babylonians and Egyptians used some means
of water accounting to individual land holders from their extensive
irrigation systems. The procedures used were possibly taken from
methods used earlier in eastern Asia.
The River Nile of Egypt has probably been studied for a longer period
of time than any other river in the world. The crops of the Nile Valley
are dependent upon annual flooding by the river, and thus, annual yields
are proportional to fluctuation in stage. In view of this, taxes were
levied based upon -maximum flood height. An interesting compilation of
data concerning flood records of the Nile has been prepared by Jarvis (1)
Mention of the annual rises of the Nile date back to between 3000 and
3500 B.C., and known flood marks extend as far back as approximately
1800 B.C.
One of the most complete records of early flow measurement systems is
that by Sextus Julius Frontinus (2), who was the Water Commissioner of
Rome in the latter part of the first century. The quantity of water
delivered to each user in the Roman system was determined entirely on
the area of spouts through which the flow was discharged; thus, these
could be considered as early forms of flow nozzles.
The earliest attempts at flow velocity measurement were undoubtedly
made by timing the travel of floating debris over some measured dis-
tance. Hero of Alexandria's proposal, which was written about 62 A.D.,
called for using a sun dial for timing his operation. In the 15th Cen-
tury, Leonardo da Vinci offered an improvement by attaching an inflated
pig's bladder to one end of a pole and a stone to the other, thus
achieving an integrating float of sorts. Frazier (3) provides an in-
teresting account of a physician's plan for a deflection water current
meter, circa 1610. In the middle of the 17th Century, Evangelista
Torricelli developed the relation that the rate at which water was dis-
charged from an orifice varied with the square root of the height of
the water surface in the supply tank. Subsequent improvements in the
state of the art included Henri Pitot's impact tube developed in 1732,
Reinhard Woltman's propeller-type current meter invented around 1790,
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and the work of Giovanni Venturi on the relations between the velocities
and pressures of fluids flowing through converging and diverging tubes
reported in 1797.
The history of improvements in flow measurement devices/techniques is
far too extensive to be reported here. The reader interested in the
subject is referred to some of the selected additional references
listed in Section XI. It suffices to say that today we have a plethora
of liquid flow measurement devices and techniques available, and it is
to them that the remainder of this report will be directed.
PURPOSE AND SCOPE
Among man's first waterworks projects were aqueducts to convey water
into his cities for consumption and sewers to collect and dispose of
nuisance stormwater. As early urbanization continued, these first
storm drains also became the transport media for domestic wastewater-
and, in effect, the first combined sewers. For convenience and expe-
diency, these sewers simply emptied into the nearest natural water-
course. As urbanization continued, the dry-weather flow in these
sewers became a public nuisance, and wastewater treatment was born.
Sanitary engineering practices and procedures were developed, all
based upon characterizing and treating this dry-weather or sanitary
sewage flow. The construction of separate storm and sanitary sewer
systems in many cities was merely an extension of this trend. The
pollutional characteristics of stormwater were unrecognized, and it
continued to be simply discharged into the nearest natural stream.
The phenomenal growth of urban areas in recent times and the rapid ex-
pansion of industrial operations to meet society's ever increasing
demands for more goods, energy, etc., have heightened the pollutional
potential of man's existence and have contributed to his increasing
awareness of and concern for his environment. One of the impacts of
the population explosion is that sanitary engineering practices that
appeared tolerable even as recently as a few decades ago are no longer
acceptable today in many locales. The pollutional effects of storm-
water and combined sewer overflows on receiving water quality are be-
coming less and less tolerable and a research program to mitigate or
ameliorate the situation has been underway at the USEPA (and its
predecessor- agencies) for the last several years.
In order to characterize these stormwater and combined sewer overflows
and to facilitate the development, demonstration, and evaluation of
treatment and control systems for combating the problem, it is neces-
sary to have available accurate and reliable means of determining the
quantity and quality of the flows in question. Both the quantity1 and
quality of urban stormwater runoff are highly variable and transient
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in nature, being dependent upon meteorological and climatological fac-
tors, topography, hydraulic characteristics of the surface and sub-
surface conduits, the nature of the antecedent period, and the land use
activities and housekeeping practices employed. Conventional flow meas-
urement devices and techniques have been developed mainly for the rela-
tively steady-state flows as found in irrigation canals, sanitary sewers,
and large streams and not for the highly varying surges encountered in
storm and combined sewers.
This report is intended""1-to present a current review of the state of the
art and assessment of flow measurement devices and techniques,. These
are described and evaluated in terms of their suitability for use in
storm and combined sewer applications. However, a device or technique
which is suitable for such use will most likely suffice for any other
wastewater flow measurement application as well. By collecting and
presenting such a review, it is hoped that shortcomings and limitations
of some extant devices and techniques for storm and combined sewer ap-
plications can be overcome and that this report can serve as a spring-
board for improvements.
GENERAL NATURE OF STORM AND COMBINED SEWER FLOWS
Storm Sewer Flows
Although storm sewers are basically designed to carry storm runoff,
during periods of no rainfall they often carry a small but significant
flow (dry weather flow). This may be flow from ground water, or "base
flow", which gains access to the sewer from unpaved .stream courses.
Such base flow may appear as runoff from parks or from suburban areas
where there are open drains leading to the storm sewer. Unfortunately,
much of the dry weather flow in storm sewers is composed of domestic ....
sewage or industrial wastes or both. Where municipal ordinances con-
cerning connections to sewers are lax or are not rigidly enforced, it
appears reasonably certain that unauthorized connections to storm sew-
ers will appear. In some cases, the runoff from septic tanks is carried
to them. Connections for the discharge of swimming pools, foundation
drains, sump pumps, cooling water, and pretreated industrial process
water to storm sewers are permitted in many municipalities and con-
tribute ,to flow during periods of no rainfall. In some areas, sewers
classed as storm sewers are, in fact, sanitary or industrial waste
sewers due to the unauthorized or inappropriate connections made to
them. This may become so aggravated that a continuous flow of sanitary
or industrial wastes, or both, flows into the receiving stream.
The "dry-weather" portion of storm sewer flow may vary significantly
with time. Probably the most steady flow, and constant character of
pollutants therein, occurs in storm sewers when all flow is base flow
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derived from ground water. Because of the slow movement of water
through the ground, changes in flow and concentration of pollutants
occur only during relatively long time periods. Where unauthorized
connections of domestic sewage and industrial waste lines to storm sew-
ers are found, rapid fluctuations with time may occur. The domestic
sewage constituent varies with time of day, with season of year, and
probably over long-term periods. Industrial wastes vary with specific
processes and industries. Very rapid changes may occur with plant
shift changes and with process dynamics. Conditions on weekends and
holidays may be very different from those on regular work days.
Storm runoff is the excess rainfall which runs off the ground surface
after losses resulting from infiltration to ground water, evaporation,
transpiration by vegetation, and ponding occur. A small portion of
the rainfall is held in depression storage, resulting from small ir-
regularities in the land surface. The quantity, or rate of flow, of
storm runoff varies with intensity, duration, and areal distribution
of rainfall; character of Jihe'soil and plant life; season of the year;
size, shape and slope of the drainage basin; and other factors. Ground
seepage loss varies during the storm, becoming less as the ground ab-
sorbs the water. The period of time since the previous, or antecedent,
rainfall significantly affects the storm runoff.
In general, storm runoff is intermittent in accordance with the rain-
fall pattern for the area. It is also highly variable from storm to
storm and during a. particular storm. The time-discharge relationship,
or hydrograph, of a typical storm, with its synchronous time-
precipitation relationship, or hyetograph, is illustrated in Figure 1.
The meanings of various parameters given in the figure are:
R
av
- Rainfall retained on the permeable portion of the
drainage basin, and not available for runoff.
- Precipitation in excess of that infiltrated into
the ground, plus that retained on the surface.
Equals the volume of flood runoff.
- Average infiltration of the ground during the
storm. Infiltration capacity decreases as the
storm progresses.
- Period of rise from the beginning of storm runoff
to peak of the hydrograph.
- Time from center of gravity of rainfall excess
to the hydrograph peak (lag time).
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b.,b- - Base line separating groundwater discharge from
surface runoff.
The total volume of runoff for a particular storm is represented by the
areas between the base line and the hydrograph.
To illustrate some of the problems in measuring storm runoff in small
basins, peak flows exceeding 85 cubic meters per second per 260 hectares
(3,000 cfs per square mile) have been observed. Lag times (t ), for
example, of 15 minutes to a hydrograph peak of about 28 cubic meters per
second (1000 cfs) from a 600-hectare (2.3 sq mi) area are not uncommon.
With rapid changes in the flow such as this, only those flow measure-
ment methods which are responsive to such changes can be used. The
high rates of flow, with accompanying high velocities, further limit
the usable flow measuring equipment methods.
The maximum rate of flow in an underground storm sewer is governed by
its design capacity. This capacity is based on the flow due to a storm
occurring, on the average, once in a selected number of years (recur-
rence interval). Usually, a recurrence interval not greater than
10 years is selected for the design of underground storm sewers. As
a result, the design capacity of the sewer is sometimes exceeded, re-
sulting in surcharging and flooding of the overlying surface. Under
these conditions, measurement of surface flow must be added to meas-
urement of surcharged flow in the sewer to obtain total flow.
The poor quality of stormwater draining from the urban environment has
a significant effect on the choice of suitable flow measurement equip-
ment and methods. Washings from the sidewalks, streets, alleys, and
catch basins are a part of the runoff and include significant amounts
of human and animal refuse. In industrial areas, chemicals, fertilizers,
coal, ores, and other products are stockpiled exposed to rainfall, so
that a significant quantity of these materials appears in the runoff.
Extreme quantities of organic materials such as leaves and grass cut-
tings often appear in storm sewers. Often during storms large boards,
limbs, rocks, and every imaginable kind of debris appear in the sewers,
probably as a result of breaks in the sewers or accessory equipment
designed to screen out the larger items.
Observation and experience have demonstrated that the heaviest con-
centration of suspended solids during periods of storm runoff usually
occurs during the early part of the storm. At this time, the stage
is rising, and accumulated dry-weather solid residue is being flushed
from the sewers and washed and eroded from the tributary land areas.
As runoff recedes, the sewer and land area surfaces exposed to flow
are reduced; the flow velocities which serve to flush and erode are
decreased; and the more easily dislodged solids have been acted upon.
10
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This pattern of variation may not occur during a period of storm run-
off which, immediately follows a previous storm runoff period because
the land surface and sewer lines are. relatively clean.
Pollutants which may be injurious to equipment, and are derived from
point sources such as those from stockpile drainage, vary at the
sampling location with time of travel from the source to the point of
observation. Maximum concentration may occur after the peak of storm
runoff. It is conceivable that there would be no contribution from
some point sources during a specific storm because of areal variation
of rainfall in the basin.
Both velocity and the concentration of suspended solids in storm sew-
ers vary with position in the sewer cross-section. The manner in which
velocity is distributed in the sewer section seriously affects those
flow measurement methods which require independent determination of
average velocity. Some typical velocity profiles are shown in Figure 2.
With open-channel flow, higher velocities are usually found near the
surface and lower velocities near the bottom. Average velocity in the
vertical is at about 0.6 depth. Velocities are higher near the center
of the pipe or conduit than near the outer boundaries. When the conduit
is surcharged and is flowing full, lines of equal velocity tend to be
concentric, with the higher velocity near the center. On horizontal
curves, higher velocities are on the outside of the curve due to the
centrifugal inertia force. Because the effect of curvature on flow
often continues downstream for a considerable distance, a normal dis-
tribution of velocity is not found on a curve, or downstream for a
distance of several sewer widths.
Suspended solids heavier than water have their lowest concentration
near the surface, and the concentration increases with depth. A "bed
load", composed almost entirely of heavier solids, may occur near the
bottom of the sewer. This may "slide" along the bottom or, with in-
sufficient flow velocity, may rest on the bottom. As the velocity and
turbulence increase, the "bed load" may be,picked up and suspended in
the sewage. At the beginning of storm runoff, as water picks up solids
which have accumulated in the sewer upstream during periods of no rain-
fall, the flow may be composed largely of sewage solids, or bed load,
which appears to be pushed ahead by the water.
Suspended materials lighter than water, such as oils and grease, float
on the surface - as do leaves, limbs, boards, and some cloth and paper
materials. Other small, light particles are moved randomly within the
flow by turbulence. Larger, heavier suspended and floating solids
tend to move to the outside of a horizontal curve, following the stream
line's of higher velocity.
11
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if""- -*•- .*• r-y:
LAMINAR
TURBULENT
a) FULL PIPE FLOWING UNDER PRESSURE
7/7
b) SOME OPEN CHANNEL FLOW PROFILES
Figure 2. Typical Vertical Velocity Profiles
12
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Combined Sewer Flows
Combined sewers are designed to carry both stormwater and sanitary
sewage and/or industrial wastes. Therefore, except for their sanitary
and industrial sewage components (dry-weather flow]), they have the same
flow characteristics as storm sewers. As indicated earlier, where mu-
nicipal ordinances are lax or not enforced with respect to sanitary or
industrial sewer connections to them, storm sewers are little different
from combined sewers. As combined sewers are designed, dry-weather
flow generally includes only a small portion of the total sewer flow.
However, due to overloading in many rapidly developing areas, the dry-
weather flow sometimes requires a much larger percentage of total
capacity. Furthermore, stormwater runoff usually increases dramatically
with urbanization.
Because the design, or available, capacity of combined sewers for car-
rying stormwater is probably less than is usually provided in storm
sewers, they either become surcharged more frequently, or the excess
flow is diverted to overflow lines.
NEED FOR FLOW MEASUREMENT '
Measurements of quantity of flow, usually in conjunction with sampling
for flow quality, are essential to nearly all aspects of water pollu-
tion control. Research, planning, design, operation and maintenance,
and enforcement of pertinent laws - all are activities which rely on
flow measurement for their effective conduct. For some activities,
very precise, time synchronized, continuous flow records are needed.
With others, occasional, fairly rough estimates of flow may suffice.
Research
A principal research activity is the development of an extensive backlog
of data to characterize the various types of wastewater - e.g., sanitary
and industrial wastes, stormwater, combined sewage, and effluents from
treatment plants. The quantity and rate of sanitary sewage flow from
individual homes, apartments, and commercial buildings, as found in
various cities and geographic locations, provide data useful for many .
purposes. Similarly, measurement of the flow of wastes from specific
industrial processes provides general information concerning the char-
acter of such industrial wastes. Characterization of stormwater and
combined sewage with respect to geographic location, population density,
land use, and other parameters, makes reasonably accurate estimation for
unmeasured areas possible. Similarly, flow records from a network of
natural streams throughout the country, such as those maintained by the
U.S. Geological Survey, make possible the characterization of ungaged
streams which may be required to receive wastewaters.
13
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Mathematical models of the relationships between rainfall, runoff, basin
characteristics, and concentration of pollutants in the runoff, such as
the Storm Water Management Model of the TJSEPA, are being developed.
The principal limiting factor-in the development and testing of such
models has been the scarcity of satisfactory data on the quantity and
quality of runoff in urban areas. Although these models can perform a
very useful function in synthesizing flow records, they do not fully
substitute for actual flow measurements and records. For example, ap-
plication of a model to an unfamiliar area needs verification by actual
records, and adjustments to the model are often indicated.
Planning
The availability of reasonably accurate and long-term records of flow
is a basic requirement for planning new or expanded systems of sewers,
o'r systems for the control and/or treatment of stormwater and combined
sewage. Such records, with records of water quality, are required to
define the scope of the problem to be solved, and to make necessary
decisions concerning the type, size, number, and location of facilities
required.
A knowledge of existing flow conditions, plus knowledge of existing
pollutant concentrations, is indicative of conditions to be expected
in the future, and thus serves to define the problem. For example, in-
filtration into sewers is a common problem which must be addressed to
avoid excessive construction and operational costs. Flow measurements
can serve to locate the approximate source and quantity of such
infiltration.
For storm and combined sewer systems, knowledge of the number, fre-
quency, and pollutant loadings (the product of quantity and concentra-
tion) of overflows is necessary to evaluate their impact on the
receiving stream. Thus, the extent and seriousness of .the problem can
be determined.
,In many cases, the sources and movement of stormwater pollutants are not
obvious. They may originate partly through rain and snowfall over a
city; from the surfaces of buildings, streets, vacant land, construc-
tion sites, parking lots, and yards in urban runoff; and in the sewer
system. Often the sources and movements of such pollutants can be
determine^ through a systematic program of flow measurement and sam-
pling, thus outlining the necessary extent of a pollution control
system or program.
A significant number of procedures and facility types are available to
management for the control of pollution due to stormwater and combined
sewage. In general, these include methods for controlling the quantity
of flow, and those for treating, or improving the quality, of wastewater.
14
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Quantity of stormwater can be controlled at the source by increasing
infiltration to groundwater, and can be controlled in the sewer system
itself by reducing infiltration to the system, by using the maximum
capacity of the system itself for storage, and by other procedures.
Facilities for temporary storage of wastewater outside of the sewer
system can be provided.
A number of physical, chemical, combinations of physical-chemical, and
biological methods have been considered in the Storm and Combined Sewer
Pollution Control Program of the USEPA for treatment of stormwater and
combined sewage. In most cases, some type of control such as reduction
of instantaneous peak flows is essential for practical application of
treatment methods. Selection of suitable facilities and procedures
for control of peak flows depends upon the availability of storm hydro-
graph records.
Character of storm runoff as influenced by geographic differences in
storm patterns, intensity, and frequency is defined by records of
flow and is the basis for decision on the type of pollution control
system to be used. As stated by Lager and Smith (5), "Stofim 0$ high.
•inte.m>wt> a £ tow
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and size of units, the quantity of chemicals, and the design of equip-
ment for chemical handling must be based on records of peak flow and
volume of flow, as modified by storage.
Operation and Maintenance
Although operational guides and maintenance procedures are often based
on historical records of flow, flow records obtained on a "real-time"
basis may be more useful for operational purposes. Where temporary
storage within an extensive system of sewers is controlled by computer,
flows at remote locations may be sensed and telemetered to the com-
puter. The system can thus be regulated to more fully utilize its
total capacity. If temporary offline storage is to be utilized within
a combined sewer system, a preselected rate of flow, or stage, in the
sewer could serve to initiate diversion to storage. Efficient operation
of systems for wastewater pollution control must depend upon measure-
ment and sampling of flows. In fact, operation of the large-scale,
high-rate systems that may often be required for control and treatment
of stormwater and combined sewage will not be possible without coordi-
nated systems of flow measurement and sampling.
Permits and Enforcement
Section 402 of the Federal Water Pollution Control Act Amendments of
1972 (6), "...creates a National Pollutant Discharge. Elimination System
under which the. Administrator o& the. Environmental Protection Age.nc.ij
mag, a^ter opportunity fior public hearings, issue, permute &or the. dis-
charge. o£ any pollutant on. combination oft pollutants, upon condition
that such discharge, will me.e£ all applicable. Jie.qulsiwe.ntf> o& the. Act
relating to e.^luent limitation*, water quatlty standards and imple.-
mewtation plant,, new source, performance, standards, i.nspe.ction, moni-
toring and entry provisions, and guideline* establishing ocean
discharge, csiit&ftia."
The Act requires that the Administrator of the USEPA prepare, and make
public, a fact sheet for every permit application having a total dis-
charge volume of more than 500,000 gallons on any day of the year.
(The Administrator may prepare fact sheets for smaller discharges.)
Included in the fact sheet must be: "A quantitative, description 0&
the. discharge. describe.d in the. NPPES application which tncludes^ the,
rate, or £ke.quency ofi .tke. propose.d discharge.;
-------
TYPES OF FLOW DATA REQUIRED
Basic flow data can be classified in accordance with their probable
accuracy, time continuity or discontinuity, and their general quantity
level - such as high, medium, or low. All flow data must be synchro-
nized with time, at least on a watch time basis, to have any useful
meaning. For some purposes, such as certain research or operation
functions, very precise time synchronization is necessary. To in-
crease their usefulness, various statistical parameters such-as totals,
means, extremes, variability, and frequency are derived by analysis of
the basic flow data.
Continuous records of flow for the time period of interest probably
are most commonly required. For planning and design of pollution con-
trol facilities, or for determining the effects of pollution on the
receiving stream, many years of continuous record of flow may be use-
ful. Continuous "real-time" data for operation of facilities may be
needed for an indefinite time period.
In many storm sewers, flow outside the periods of storm runoff is
negligible. Therefore, the need is for continuous record of flow
during periods of storm runoff only. Flow measurement equipment can
be activated automatically by the onset of rainfall, or by preselected
water surface elevation, and can be deactivated in a similar manner.
There may be situations where the magnitude and frequency of peak flows
only would be required. These data could, for example, be required for
determination of the maximum required size of sewers or other facilities.
In this case, crest-stage measurements only can be obtained by various
simple devices such as a vertical pipe stilling well with a graduated
rod left in it. Maximum stage is recorded by a line of ground cork,
or other floatable material, left on the stick during a period of
storm runoff. A calibrated primary device, such as a culvert, flume,
or rated channel, must be used with the crest-stage measuring equipment.
On the other hand, measurements of low flow only can be useful. This
would be true in cases where low flow augmentation of the receiving
stream could be an acceptable measure for reducing the concentration
of pollutants in the stream. Because of the usual slow change in
streamflow during periods of dry weather, comparatively few measure-
ments are needed to define such low flows.
Another type of flow measurement, often known as a miscellaneous meas-
urement, is made only at rather infrequent intervals of time. The time
interval may ,be regular, or it may be simply at the convenience of the
hydrographer. Such measurements are useful where flow is known to be
relatively steady. Flows of effluent from treatment plants, effluent
17
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from selected types of industrial plants, sanitary sewage, or storm
sewers during periods of dry weather may be satisfactorily defined by
miscellaneous measurements.
Often, flow measurements are made for the purpose of calibrating
another, possibly continuous type, flow measurement device. For ex-
ample, a series of current meter measurements may be made over a range
of stages to calibrate a measuring flume which may not be precalibrated
satisfactorily.
The probable accuracy of flow data is determined by a number of factors.
Each type of flow measurement equipment has an inherent maximum capa-
bility for accuracy. Care with which certain types of equipment are
installed affects the accuracy of the flow data. Conditions under which
the equipment is used influence the accuracy of the data collected.
The harsh conditions found in many sewers can be detrimental to meas-
uring equipment, and makes the work of the hydrographer difficult. Use
of certain types of equipment necessitates considerable training and
experience if accurate records are to result. Estimates of probable
accuracy of the data should always be furnished by field personnel as
a guide to the user, who otherwise has little means of knowing if they
should be rated as excellent, good, fair, or poor.
18
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SECTION IV
THE TIME ELEMENT IN FLOW DATA
Measurements of flow are useful only with respect to the relationship
of the measured flow with other phenomena. An assignment of time of
occurrence to flow data makes possible a determination of its relation-
ship to other parameters whose times of occurrence are known. The
other parameters of interest may or may not be synchronous with the flow
data. In some cases, definition of the time interval between events is
sufficient but, generally, the true clock time, preferably standard time,
of the concerned flow is required.
IMPORTANCE OF THE TIME ELEMENT
The required accuracy of the time element in flow data is very different
from requirement to requirement. An example is the use of peak flows
for each year to determine their frequency. On the other hand, flows
at intervals as short as one minute have been collected to define the
discharge hydrograph from small urban areas.
A particular need for improved accuracy in the time element occurs in
the measurement of flows from small urban storm sewers in order to de-
fine the hydrograph and to provide data for development and verifica-
tion of rainfall-runoff-quality models. Accurate definition of both
the time and discharge elements of the hydrograph makes possible the
computation of total volume of runoff during the storm by computing the
area under the hydrograph, exclusive of base flow. By selecting a num-
ber of well defined hydrographs resulting from storms of similar rain-
fall characteristics, a typical hydrograph for the basin can be defined.
When the hydrograph is so adjusted that its runoff volume is 2.54 cm
(1.00 in.) of rainfall excess, it is called a "unit hydrograph", and it
can be conveniently used to define hydrographs resulting from similar
rainfalls of any volume of rainfall excess. Shape of the unit hydro-
graph is determined by accurate timing as well as by dischargef although
it is independent of clock time. The hydrograph as defined by clock
time and discharge is often used to route flows along a stream channel
or through a reservoir.
Peak flows, storm runoff volumes, daily flows, or other flow parameters
are often correlated with similar flows at other points on a storm sewer
or stream, or with flows of other storm sewers or streams, to provide a
means for flow estimation. Also, correlations may be made with various
physical characteristics of a basin, such as area, slope, population
density, etc. Correlations with temperature, soil moisture, or ante-
cedent precipitation may be made at times. In most cases, it is
19
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essential that the correlated variables be synchronous, so accurate
timing of the data is often required.
Timing of measured flows and collection of quality samples can be use-
ful in determining sources of pollution. For example, they can be
related to time of release of pollutants from industrial plants, or
to the time of accidental spills of pollutants. The time of travel of
pollutants along a stream or storm sewer can be estimated from the time
of travel of small rises or other flow changes in the channel.
In many situations where flow measurement is used for operation of pol-
lution control facilities, accurate timing of the flows may be required.
This is particularly true where upstream flow data are transmitted
electronically for automatic control of gates, pumps, and other devices
for the relief of stormwater flows.
CONTINUOUS RECORDING OF FLOWS
Many different kinds of equipment are available for the continuous
recording of flow data. In general, they consist of a clock, or timer,
which drives or regulates the rate of motion of a strip chart or tape,
or a circular chart. Discharge may be recorded directly on the chart
by pen, pencil, or digital punch; or, stage only may be recorded for
later conversion to discharge by means of known relationships of stage
to discharge. This conversion may be made manually, with the aid of a
discharge integrator, or by means of a computer where digital punched
tape is available.
Adjustments, or corrections, to the record are usually required. The
clocks or timers in general use do not maintain fully accurate chart
time. Sliding time corrections are made for the periods between visits
when the chart position of the pen is compared with watch time of the
hydrographer. Small errors in discharge or stage are similarly cor-
rected for the periods between visits. Careful review of the charts
may reveal periods of clock stoppage, temporary backwater conditions,
or instrument malfunctions for which corrections may be made.
When the relationship between stage and discharge is nonlinear, rapidly
changing stages must be subdivided into relatively short periods before
converting to discharge. Due to intermittent use of daylight saving
time, and' inconsistent use of such time from place to place, all flow
records should be adjusted to standard time.
Clock Drives and Timers
Clock drives commonly used on flow recorders include spring wound,
suspended weight, battery powered motor, and synchronous motor (alter-
nating current). Except for those driven by synchronous motor through
20
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a power system of regulated frequency, significant time errors can be
expected. Errors of one or two hours per week are common with recorders
of the 8-day type. Without careful clock adjustment, errors of several
hours per month in continuous-type recorders are to be expected. Timers
on the digital paper punches now widely used in the field by the U.S.
Geological Survey are said to provide correct timing within about
15 minutes per month. Where required, more accurate timers are avail-
able to substitute for those in more general use. Extremely accurate
time can be maintained with quartz crystal timers, for example. The
cost of such solid state timers is not high, except for those having
refinements such as compensation for error due to temperature change.
Synchronous data recording is often achieved by the tracing of more
than one data parameter on a single chart controlled by a single timer.
Thus, flow data may be traced together with rainfall data to provide a
better relationship between rainfall and runoff. On one existing
project, flow data from several sites are being transmitted to a central
location and traced on a single chart. Although the data thus recorded
are synchronous, they are not necessarily plotted to correct clock time.
In several systems of combined sewers, "real-time" rainfall, quality,
and flow data are transmitted to a central computer, which analyzes the
data to provide control of gates, pumps, and regulators for optimum sys-
tem operation.
Recorder Charts and Tapes
Difficulty in recording the correct time.of flow data arises not only
from error of timers, but also from mechanical inaccuracies in the
recorders, and from nonconstant dimensions of the recorder paper.
Under moist, humid conditions, most paper charts expand a significant
amount. Expansion of more than 0.5 percent is to be expected at times.
Error due to expansion of a strip chart could thus be one hour (or more)
in 10 days of operation. A recorder with an auxiliary pen that marks
the paper at uniform intervals of clock time, rather than relying upon
preprinted time divisions on the chart, serves as a basis for correction
due to humidity effects.
Timing of digital paper tape punch recorders is not affected by changes
in the paper tape length because the punches occur at uniform intervals
.of clock time.
NONCONTINUOUS FLOW DATA
Other flow measurements, such as the miscellaneous type, are usually
made directly by the hydrographer and are timed by his watch. It is
important that he maintain his watch as accurately as possible, and
that he note the time as standard or daylight saving, whichever it
may be.
21
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It is neither possible, nor necessary, to determine the precise time
for crest~stage measurements of peak flows obtained as described above.
Usually, the time can be established closely enough for the purpose by
comparison with the corresponding peak stage at a nearby flow recording
site.
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SECTION V
DESIRABLE EQUIPMENT CHARACTERISTICS
From the brief review of the severe conditions and vagaries of storm
and combined sewer flow and discussions given in the preceding sections,
it is intuitively obvious that a number of very stringent design re-
quirements must be placed on flow measurement devices if they are to
function satisfactorily in such an application. It should also be ap-
parent that no single design can be considered ideal for all flow meas-
urement activities in all storm and combined sewer flows of interest.
Characteristics of the available sites, as well as the particular flows
in question, make a device that might be acceptable for one location
totally unsuitable for another. Despite this, one can set forth some
equipment "requirements" in the form of primary design goals and some
desirable equipment features in the form of secondary design goals.
PRIMARY DESIGN GOALS
The following are considered to be primary design goals for equipment
that is to be used to measure storm and combined sewer flows:
Range - Since flow velocities may range from 0.03 to 9 meters per second
(0.1 to 30 fps), it is desirable that the unit have either a very wide
range of operation; be able to automatically shift scales; or otherwise
cover at least a 100 to 1 range.
Accuracy - For most purposes, an accuracy of ±10% of the reading at the
readout point is necessary, and there will be many applications where
an accuracy of ±5% is highly desirable. Repeatability of better than
±2% is desired in almost all instances.
Flow Effects on Accuracy - The unit should be capable of maintaining its
accuracy when exposed to rapid changes in flow; e.g., depth" and velocity
changes in an open channel flow situation. There are instances where
the flows of interest may accelerate from minimum to maximum in as short
a time period as five minutes.
Gravity and Pressurized Flow Operation - Because of the conditions that
exist at many measuring sites, it is very desirable that the unit have
the capability (within a closed conduit) of measuring over the full
range of open channel flow as well as with the conduit flowing full and
under pressure.
Sensitivity to Submergence or Backwater Effects - Because of the pos-
sibility of changes in flow resistance downstream of the measuring site
23
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due to blockages, rising river stages including possible reverse flow,
etc., it is highly advantageous that the unit be able to continue to
function under such conditions or, at a minimum, be able to sense the
existence of such conditions which would lead to erroneous readings.
Effect of Solids Movement - The unit should not be seriously affected
by the movement of solids such as sand, gravel, debris, etc. within
the fluid flow.
Flow Obstruction - The unit should be as nonintrusive as possible to
avoid obstruction or other interference with the flow which could lead
to flow blockage or physical damage to some portion of the device.
Head Loss - To be usable at a maximum number of measurement sites, the
unit should induce as little head loss as possible.
Manhole Operation - To allow maximum flexibility in utilization, the
unit should have the capability of being installed in confined and
moisture-laden spaces such as sewer manholes.
Power Requirements - The unit should require minimum power at the meas-
uring site to operate; the ability to operate on batteries is a definite
asset for many installations.
SECONDARY DESIGN GOALS
The following are desirable features for flow measuring equipment,
especially for use in a storm or combined sewer application:
Site Requirements - Unit design should be such as to minimize site re-
quirements, such as the need for a fresh water supply, a vertical drop,
excessive physical space, etc.
Installation Restrictions or Limitations - The unit should impose a
minimum of restrictions or limitations on its installation and be
capable of use on or within sewers of varying size.
Simplicity and Reliability - To maximize reliability of results and
operation, the design of the* unit should be as simple as possible, with
a minimum of moving parts, etc.
Unattended Operation - For the majority of applications, it is highly
desirable that the equipment be capable of unattended operation.
Maintenance Requirements - The design of the equipment should be such
that routine maintenance is minimal and troubleshooting and repair can
be effected with relative ease, even in the field.
24
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Adverse Ambient Effects - The unit should be unaffected by adverse
ambient conditions such as high humidity, freezing temperatures, hydro-
gen sulphide or corrosive gases, etc.
Submersion Proof - The unit should be capable of withstanding total
immersion without significant damage.
Ruggedness - The unit should be of rugged construction and as vandal
and theft proof as possible.
Self Contained - The unit should be self contained insofar as possible
in view of the physical principles involved.
Precalibration - In order to maximize the flexibility of using the
equipment in different settings it is desirable that it be capable of
precalibration; i.e., it should not be necessary to calibrate the sys-
tem at each location and for each application.
Ease of Calibration - Calibration of the unit should be a simple,
straightforward process requiring a minimum amount of time and
ancillary equipment.
Maintenance of Calibration - The unit should operate accurately for
extended periods of time without requiring recalibration.
Adaptability - The system should be capable of: indicating and
recording instantaneous flow rates and totalized flows; providing flow
signals to associated equipment (e.g., an automatic sampler); imple-
mentation of remote sensing techniques or incorporation into a com-
puterized urban data system, including a multisensor single readout
capability.
Cost - The unit should be affordable both in terms of acquisition and
installation costs as well as operating costs, including repair and
maintenance.
EVALUATION PARAMETERS
It iSj of course, not necessary that all of the primary and secondary
design goals be achieved for all flow measurement requirements. For
example, "spot" measurements of all flow rather than continuous records
are sufficient at times. Flow measurement devices used to calibrate
others need not necessarily be self contained, nor would unattended
operations be required. Furthermore, meeting all of the listed design
goals for all installations and settings would be difficult, if not
impossible, to achieve in a single design.
25
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Nonetheless, the primary and secondary design goals can be used to
formulate a set of evaluation parameters against which a given design
or piece of equipment can be judged. Since application details may
make certain parameters more or less important in one instance or
another, no attempt has been made to apply weighting factors or assign
numerical rank. It is hoped that the evaluation factors will prove
useful, as a check list among other things, for the potential user
who has a flow measurement requirement and who may require assistance
in the selection of his equipment.
The evaluation parameters, together with qualitative scales, are presented
in the form of a flow measurement equipment checklist in Table 1.
26
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TABLE 1. FLOW MEASUREMENT EQUIPMENT CHECKLIST
Designation:
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or' Backwater
Effects
Effect of Solids Movement
Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Advers'e Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precal ibration
Ease of Calibration
Maintenance of Calibration
Adaptability
Cost
Portability
Scale
D Poor D Fair DGood
D Poor D Fair Q Good
DHigh D Moderate D Slight
D No D Yes
.D High D Moderate D Low
DHigh Q Moderate D Slight
QHigh D Moderate D Slight
.DHigh D Medium D Low
D P.oor D Fair D Good
DHigh D Medium D Low
DHigh .D Moderate D Slight
DHigh D Moderate D Slight
D Poor D Fair D Good
D No D Yes
DHigh D Medium D Low
DHigh D Moderate D Slight
D No D Yes
O Poor D Fair D Good
D No D Yes
D No D Yes
D Poor D Fair D Good
D Poor D Fair D Good
D Poor D Fair DGood
D High D Medium D Low
D No . D Yes
Weight and Score
Comments:
.27
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SECTION VI
METHODS OF FLOW DETERMINATION
GENERAL
This section is intended to provide the reader with an overview of the
physical principles that have been utilized in the design of equipment
for the quantitative measurement of flows. It presents a discussion,
in generic terms, that may help the reader to better follow the treat-
ment of commercially available equipment given in Section VII. There
are a number of excellent references on the subject and the reader is
referred to them for a more in-depth presentation. Noteworthy among
these are the ASME monograph on fluid meters (7) which was used as a
guide for the organization of this section as well as much of its Con-
tent, Replogle (8) and McMahon (9) which were also liberally used as
resource material; the USDI Bureau of Reclamation's water measurement
manual (10), the Leupold and Stevens water resources data book (11),
and the many standard texts on hydraulics, fluid mechanics, etc.
Any flow measurement system can be considered to consist of two dis-
tinct parts, each of which has a separate function to perform. The
first, or primary element, is that part of the system which is in con-
tact with the fluid, resulting in some type of interaction. The sec-
ondary element is that part of the system which translates this
interaction into the desired readout or recording. While there is al-
most an endless variety of secondary elements, primary elements are
related to a more limited number of physical principles, being depend-
ent upon some property of the fluid other than, or in addition to, its
volume or mass such as kinetic energy, inertia, specific heat, or the
like. Thus the primary elements, or rather their physical principles,
form a natural classification system for flow measuring devices and
are so used in this discussion.
Flow measurement systems may be thought of as belonging to one of two
rather broad divisions, quantity and rate. In quantity meters, the
primary element measures isolated (i.e., separately counted) quanti-
ties of fluid either in terms of mass or volume. Usually a container
or cavity of known capacity is alternately filled and emptied, per-
mitting an essentially continuous flow of the metered supply. The
secondary element counts the number of these quantities and indicates
or records them, often against time. In rate meters, by contrast, the
fluid passes in a continuous, uninterrupted stream, which interacts
with the primary element in a certain way, the interaction being depend-
ent upon one or more physical properties of the fluid. In the second-
ary element, the quantity of flow per unit time is derived from this
interaction by known physical laws supplemented by empirical relations.
A general categorization of flow meters by division, classification,
28
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type, and sub-type is presented in Table 2. Each classification is dis-
cussed briefly in the following sub-sections.
A slightly modified form of the flow measurement equipment checklist
given in Table 1 has been used to evaluate the various flow measuring
devices and techniques in tabular form, and a matrix summary is given
at the end of this section. It must be re-emphasized that these eval-
uations are made with a storm or combined sewer flow measurement ap-
plication in mind and will not necessarily be applicable for other
types of flows. They are necessarily somewhat subjective, and the
writers apologize in advance to the clever reader who has made a partic-
ular device work satisfactorily in such an application and, hence,
feels that it has been treated unfairly.
Only a few of the evaluation parameters normally have numbers associated
with them. To assist the reader in interpreting the ratings, the fol-
lowing general guidelines were used. If the normal range of a partic-
ular device was considered to be less than about 10:1, it was termed
poor; if it was considered to be greater than around 100:1, it was
termed good. The intermediate ranges were termed fair. The accuracy
that might reasonably by anticipated in measuring storm or combined
sewer flows was considered rather than the best accuracy achievable by
a particular device. For example, although a sharp-crested weir may be
capable of achieving accuracies of ±1.5%Nor better in clear irrigation
water flows, accuracies of much better than ±4-7% should not necessarily
be anticipated for a sharp-crested weir measuring stormwater or com-
bined sewer discharges. If the accuracy of a particular flow measur-
ing device or method was considered to be better than around ±1-2%, it
was termed good; if it was considered to be worse than around ±10%, it
was termed poor. The intermediate accuracies were termed fair.
The flow measuring devices and techniques were not rated on two evalua-
tion parameters, submersion proof and adaptability, because these fac-
tors are so dependent upon the design details of the secondary element
selected by the user.
SITE SELECTION
The success or failure of selected flow measurement equipment or methods,
with respect to accuracy and completeness of data collected as well as
reasonableness of cost, depends very much on the care and effort exe-
cised in selecting the gaging site. Except for a few basic require-
ments which are applicable to all types of equipment and methods which
will be discussed at this point, there are significant differences in
site needs for various flow measurement devices. Particular site re-
quirements will be addressed in the discussion of each equipment type.
A requirement which appears to be obvious, but which is frequently not
sufficiently considered, is that the site selected be located to give
the desired flow measurement. Does flow at the site provide information
29
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TABLE 2. FLOW METER CATEGORIZATION
DIVISION CLASSIFICATION
QUANTITY GRAVIMETRIC
QUANTITY GRAVIMETRIC
QUANTITY GRAVIMETRIC
QUANTITY VOLUMETRIC
QUANTITY VOLUMETRIC
QUANTITY VOLUMETRIC
QUANTITY VOLUMETRIC
QUANTITY VOLUMETRIC
QUANTITY VOLUMETRIC
QUANTITY VOLUMETRIC
QUANTITY VOLUMETRIC
RATE DIFFERENTIAL PRESSURE
RATE DIFFERENTIAL PRESSURE
RATE DIFFERENTIAL PRESSURE
RATE DIFFERENTIAL PRESSURE
RATE DIFFERENTIAL PRESSURE
RATE DIFFERENTIAL PRESSURE
RATE DIFFERENTIAL PRESSURE
RATE DIFFERENTIAL PRESSURE
RATE DIFFERENTIAL PRESSURE
RATE DIFFERENTIAL PRESSURE
RATE DIFFERENTIAL PRESSURE
RATE DIFFERENTIAL PRESSURE
RATE DIFFERENTIAL PRESSURE
RATE DIFFERENTIAL PRESSURE
RATE DIFFERENTIAL PRESSURE
RATE DIFFERENTIAL PRESSURE
RATE VARIABLE AREA
RATE VARIABLE AREA
RATE VARIABLE AREA
RATE HEAD-AREA
RATE HEAD-AREA
RATE HEAD-AREA
RATE HEAD-AREA
RATE HEAD-AREA
RATE HEAD-AREA
RATE HEAD-AREA
RATE HEAD-AREA
RATE HEAD-AREA
RATE HEAD-AREA
RATE HEAD-AREA
RATE FLOW VELOCITY
RATE FLOW VELOCITY
RATE FLOW VELOCITY
RATE FLOW VELOCITY
RATE FLOW VELOCITY
RATE FLOW VELOCITY
RATE FLOW VELOCITY
RATE FLOW VELOCITY
RATE FORCE-DISPLACEMENT
RATE FORCE-DISPLACEMENT
RATE FORCE-DISPLACEMENT
RATE FORCE-DISPLACEMENT
RATE FORCE-DISPLACEMENT
RATE FORCE-MOMENTUM
RATE FORCE-MOMENTUM
RATE FORCE-MOMENTUM
RATE FORCE-MOMENTUM
RATE THERMAL
RATE THERMAL
RATE THERMAL
RATE OTHER
RATE OTHER
RATE OTHER
RATE OTHER
RATE OTHER
RATE OTHER
RATE OTHER
TYPE
WEIGHER
TILTING TRAP
WEIGH DUMP
METERING TANK
RECIPROCATING PISTON
OSCILLATING OR RING PISTON
NUTATING DISC
SLIDING VANE
ROTATING VANE
GEAR OR LOBED IMPELLER
DETHRIDGE WHEEL
VENTURI
DALL TUBE
FLOW NOZZLE
ROUNDED EDGE ORIFICE
SQUARE EDGE ORIFICE
SQUARE EDGE ORIFICE
SQUARE EDGE ORIFICE
SQUARE EDGE ORIFICE
CENTRIFUGAL
CENTRIFUGAL
CENTRIFUGAL
IMPACT TUBE
IMPACT TUBE
LINEAR RESISTANCE
LINEAR RESISTANCE
LINEAR RESISTANCE
GATE
CONE AND FLOAT
SLOTTED CYLINDER AND PISTON
WEIR
WEIR
FLUME
FLUME
FLUME
FLUME
FLUME
FLUME
FLUME
FLUME
OPEN FLOW NOZZLE
FLOAT
FLOAT
TRACER
VORTEX
VORTEX
TURBINE
ROTATING ELEMENT
ROTATING ELEMENT
VANE
HYDROMETRIC PENDULUM
TARGET
JET DEFLECTION
BALL AND TUBE
AXIAL FLOW MASS
RADIAL MASS
GYROSCOPIC
MANGUS EFFECT
HOT TIP
COLD TIP
BOUNDARY LAYER
ELECTROMAGNETIC
ACOUSTIC
DOPPLER
OPTICAL
DILUTION
ELECTROSTATIC
NUCLEAR RESONANCE
SUBTYPE
CONCENTRIC
ECCENTRIC
SEGMENTED
GATE OR VARIABLE AREA
ELBOW OR LONG RADIUS BEND
TURBINE SCROLL CASE
GUIDE VANE SPEED RING
PITOT-STATIC
PITOT VENTURI
PIPE SECTION
CAPILLARY TUBE
POROUS PLUG
SHARP CRESTED
BROAD CRESTED
VENTURI
PARSHALL
PALMER-BOWLUS
DISKIN DEVICE
CUTTHROAT
SAN DIMAS
TRAPEZOIDAL
TYPE HS, H, AND HL
SIMPLE
INTEGRATING
VORTEX-VELOCITY
EDDY-SHEDDING
HORIZONTAL AXIS
VERTICAL AXIS
30
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actually needed to fulfill project needs? Sometimes influent flows
diversions, or storage upstream or downstream from the selected site
would bias the data in a manner not understood without a thorough study
of the proposed site. Such study would include reference to surface
maps and to sewerage maps and plans. Sometimes groundwater infiltra-
tion or unrecorded connections may exist. For these reasons, a thorough
field investigation should be made before establishing 'a flow measure-
ment site. .
There are some situations where there is no choice of sites. Only a
single site may be available where the desired flow measurement can be
made. In this case, the problem is one of selecting the most suitable
flow measurement equipment and methods for the available site.
A basic consideration in site selection is the possible availability of
flow measurements or records collected by others. At times, data being
collected by the U.S. Geological Survey, by the State, or by other pub-
Ixc agencies can be used. There are locations where useful data, al-
though not currently being collected, may have been collected in prior
years. Additional data to supplement those earlier records may be more
useful than new data collected at a different site. Other general site
considerations include any history of surcharging, entry and backwater
conditions, and intrusion from receiving waters.
Requirements which apply to all flow measurement sites are accessibil-
ity, personnel and equipment safety, and freedom from vandalism. If a
car or other vehicle can be driven directly to the site at all times
the cost in time required for installation, operation, and maintenance
of the equipment will be less, and it is possible that less expensive
equipment can be selected. Consideration should be given to access
during periods of adverse weather conditions and during periods of
flood stage. Sites on bridges or at manholes where heavy traffic oc-
curs should be avoided unless suitable protection for men and equipment
is provided. If entry to sewers is required, the more shallow locations
should be selected where possible. Manhole steps and other facilities
for sewer access must be carefully inspected, and any needed repairs
made. Possible danger from harmful gases, chemicals, or explosion
should be investigated. With respect to sites at or near streams, his-
torical flood marks should be determined and used for placement of ac-
cess facilities and measurement equipment above flood level where this
is possible. Areas of known frequent vandalism should be avoided.
Selection of sites in open, rather than secluded, areas may help to re-
duce vandalism. Often, the only solution to prevent destruction of fa-
cilities is to place them in solid concrete or steel shelters, and to
surround them with heavy fencing. Erection of warning signs is futile,
as they often serve only to provide targets.
31
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In development of a system or network of flow measurement stations,
primary consideration must be given to cost if the maximum benefit is
to result from available funds. Therefore, cost must be considered in
selection of each gaging site., Cost reduction can result from selec-
tion of sites where the less expensive types of equipment, which will
fulfill project requirements of accuracy and completeness, can be in-
stalled. For example, if a site is selected where conditions are such
that satisfactory records can be obtained with a weir installation,
this would be preferable to selecting a site where the head loss re-
quired by a weir would not be available, and the expense of installing
a Parshall flume must be met.
GRAVIMETRIC
As indicated in Table 2, gravimetric meters include weighers, tilting
trap and weigh dump meters. Weighing the fluid is a primary standard
and, since the accuracy of weighing devices is routinely considered to
be better than ±0.1%, they are frequently used to calibrate other me-
ters as, for example, at the new National Bureau of Standards flowmeter
calibration facility. In its simplest form, a gravimetric meter in-
volves determining the weight of a quantity of fluid in a tank mounted
on beam scales, load cells, or some other mass or force measuring de-
vice. Where flow is uniform, an indication of flow rate can be obtained
by measuring the time over which the measured weight of fluid is gath-
ered. The tipping bucket rain gage is probably one of the most common
meters of this type in field use. Another field application, used
where a scale or some other weighing device is available, is the sim-
ple "bucket and stopwatch" technique. Practical considerations limit
the use of this technique to fairly low flow rates, however. Gravi-
metric meters may often have a useful range of up to 100:1, and accu-
racies of ±1% of the reading or better are routine.
All types of gravimetric meters as a class are evaluated in Table 3.
Since they are generally not well suited for storm or combined sewer
flow measurement, no further discussion will be given.
VOLUMETRIC
Whenever the fluid density can be assumed to be reasonably constant, a
volumetric measure of flow is adequate. Because of their simplicity
and lower "cost as compared to gravimetric meters, most quantity meters
found on the market today are volumetric devices. A representative,
but not inclusive, listing of types of volumetric meters is given in
Table 2. As with gravimetric devices, rates of flow can be indicated
with many volumetric meters by using appropriate secondary elements.
Probably the most elementary type of volumetric device is the metering
tank. An open tank is repeatedly filled to a fixed depth and emptied.
32.
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TABLE 3. GRAVIMETRIC METER EVALUATION (ALL TYPES)
Evaluation Parameter
Seal e
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flov\
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precalibration
Ease of Calibration
Maintenance of Calibration
Adaptabi1ity
Cost
Portability
D Poor D Fair E3 Good
D Poor n Fair £3 Good
S High D Moderate D Slight
D No & yes
D High D Moderate g] LOW
K High D Moderate D Slight
KjHigh D Moderate D Slight
IE High Q Medium Q Low
OS Poor D Fair D Good
O High C3 Medium D Low
§8 High D Moderate D Slight
13 High D Moderate D Slight
SI Poor D Fair D Good
D No 63 Yes
53 High D Medium D Low
DHigh E3 Moderate D SIight
D No Q Yes
D Poor 53 Fair D Good
P No G3 Yes
D No SI Yes
D Poor D Fair 63 Good
D Poor SI Fair D Good
D Poor D Fair Q Good
81 High O Medium D Low
8! No D Yes
33
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Although potentially not as accurate as weighing, since both the fluid
and tank are subject to temperature effects, accuracies of about ±1% of
reading are routinely achieved. The usable range of a metering tank
device is a function of its design, but 10:1 is commonly achieved.
There have been a few instances where existing structures have been
used as volumetric flow measuring devices for stormwater or combined
sewage. For example, in at least one location wet wells have been
utilized in a "fill and draw" fashion in order to provide an indication
of flow. The monitoring of pump operations at lift stations in general
has been used in a number of cases to obtain flow information. Such
techniques rely upon the use of existing equipment and structures, how-
ever, and flow measurement was not their original purpose. For this
reason, they must be considered as techniques of opportunity rather
than as candidates for flow measurement equipment per se; consequently,
they will not be included in the evaluation table.
Many of the flow measuring devices in the volumetric classification are
positive displacement meters. Such units may be considered to be fluid
motors operating with a very high volumetric efficiency under a very
light load. This load is made up of two parts; the internal load due
to friction within the primary element, and the external load imposed
by the secondary element or register. As in all fluid motors, work
done against a load results in a pressure drop. The main factors in-
fluencing the magnitude of this pressure drop are the type of seal re-
quired, the power required to drive the register, the viscosity of the
liquid, and the rate of flow.
Various ingenious mechanical implementations of such meters include
such types as the reciprocating piston, oscillating or ring piston,
nutating disc, sliding and rotating vane, and gear or lobed impeller.
Several of these have seen application in water meter designs for resi-
dential and commercial use. They are seldom found in large sizes and
are obviously poorly suited for measuring storm or combined sewer flows.
A special adaptation of a vane type meter is the Dethridge Wheel. These
devices are widely used in Australia and New Zealand to measure irriga-
tion water flows, but are almost unknown in the United States. Accura-
cies of ±3.5% are reported for free discharge conditions for discharge
rates between 0.042 and 0.14 cm/s (1.5 and 5.0 cfs). Maximum ranges of
5:1 have been achieved in smaller sizes.
All types of volumetric meters as a class are evaluated in Table 4.
Since they are generally not well suited for storm or combined sewer
flow measurement, no further discussion will be given. Complete de-
scriptions and discussions can be found in the references - especially
ASME (7), Replogle (8), and McMahon (9).
34
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TABLE 4. VOLUMETRIC METER .EVALUATION (ALL TYPES)
Evaluation Parameter
Scale
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precalibration
Ease of Calibration
Maintenance of Calibration
Adaptabi1ity
Cost
Portability
8 Poor QFair DGood
D Poor D Fair K Good
53 High Q Moderate D Slight
D No 63 Yes
D High D Moderate K LOW
8 High D Moderate D Slight
63Hign D Moderate D Slight
DHigh 8 Medium Q Low
63 Poor D Fair D Good
DHigh D Medium 63 Low
8 High Q Moderate D Slight
83 High D Moderate D Slight
D Poor S! Fair D Good
D No & Yes
S3 High D Medium D Low
D High K Moderate Q Slight
D No D Yes
D Poor 53 Fair D Good
D No B Yes
D No |g Yes
D Poor D Fair Bl Good
D Poor 63 Fair DGood
D Poor D Fair DGood
H High D Medium D Low
K No .Q Yes
35
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DIFFERENTIAL PRESSURE
Flow measuring devices that fall in the differential pressure classifi-
cation operate by converting energy from one form to another. For ex-
ample, in those primary devices that have a reduced cross-section,
potential energy is converted into kinetic energy to produce a differ-
ential pressure, while in the impact type devices the reverse is true.
Centrifugal type devices utilize the acceleration of the flow around a
bend, while linear resistance type devices are based on frictional
losses. In many designs a combination of velocity head, frictional
losses, or stream-line bending is employed. An important feature of
all flow measuring devices in the differential pressure classification
used here is that they can only be used in a closed conduit flowing full
and under pressure.
Venturi
As noted above, when a fluid flows through a conduit of varying cross-
section its velocity varies from point to point along the conduit or
passage. If the velocity increases, the passage is called a nozzle,
and the kinetic energy increases at the expense of internal energy. If
the velocity decreases, the passage is called a diffuser, and the in-
ternal energy increases at the expense of kinetic energy. If the_cross-
section of a nozzle decreases continuously from entrance to exit it is
called converging, and if it increases continuously it is called di-
verging. The cross-section of a diffuser may either increase or de-
crease depending on whether the flow is supersonic or subsonic. A
venturi is a converging nozzle followed by a subsonic diffuser. The
region of minimum cross-section is called the throat. A number of dif-
ferent venturi geometries have been developed over the years, one of
the more common being the standard (long-type) Herschel Venturi meter
tube (Figure 3).
The venturi meter is one of the most accurate devices for measuring
liquid flow rates in pipes, but it is not in common use for waste flow
measurement for a number of reasons, not the least of which is its cost.
The venturi causes a very low pressure loss and, with proper precau-
tions, is good for use in liquids with high solids concentrations. For
example, A!TM Standard D 2458 states (12) "(Wwn a vejfcifce. *abe * to be.
txed to*, meters -fcuzuufc c-ontatning to*ae. concentfiattonA (^Apended
&oLu& on AJLudQZ, the. annual >vinQ te e^inu.nate.d and ftep£aced by
hole, tap* at tke. Met and throat and tke*e. vie. itu&kid
VlJUtk CJLVW MOteJi." It is further recommended that the flushing water
pressure should exceed the maximum line pressure by at least 0.7 kgf/sq
cm (10 psi). The flushing water flows should be equal and continuous,
and held to a small quantity to prevent any measurable pressure differ-
ential which would be reflected in the metering instrument.
36
-------
0)
•§
H
0)
I
-
I
00
g
I-J
•g
cd
1
0)
•s
CQ
CO
E
•H
37
-------
It is essential that the flow entering a venturi tube be of uniform
turbulence, free from helical flow and from high or low pressure areas.
Therefore, long uninterrupted runs of straight pipe upstream from the
venturi location are desirable .for accurate fluid metering. Straighten-
ing vanes can often be used to reduce the upstream straight pipe run re-
quirement when the Sisturbing device produces spiral flows, but they do
little to reduce the effects of elbows and partly opened gate valves.
The required run depends upon the nature of the upstream element; e.g.,
elbow, gate and globe valve, decreaser, increaser, etc., and the ratio
of the throat diameter to the pipe diameter. Typically, the minimum de-
sirable straight run will be from 5 to 20 pipe diameters. Conditions
downstream from the venturi tube have little effect on its performance.
The pressure differential of a venturi tube can be measured using mer-
cury columns, electrically, pneumatically, or by incorporating a water
level sensing device (e.g., a float operated instrument) and water col-
umns. Although manufacturers typically supply rating curves with their
instruments, ASTM (12) recommends that each venturi be calibrated in
place to meet accuracy standards. Accuracy is affected by changes in
density, temperature, pressure, viscosity, and by pulsating flow. Under
ideal conditions a venturi can yield accuracies of around ±0.5/ of the
reading, but more typical accuracies achieved are about ±1 or 24. Most
installations are usable over a range of 5:1 or so. Venturi tube meters
are evaluated in Table 5.
Flow Tubes
Following the development of the Herschel venturi tube in 1887, a num-
ber of variations such as the short-coned venturi were developed. Among
the more recently introduced venturi-type primary devices is the Dall
flow tube (13), which was developed in England. The Dall tube consists
of a flanged cylindrical body designed with a short straight inlet sec-
tion which terminates abruptly with a decrease in diameter, thus form-
ing a shoulder. This is followed by a conical reducer and diverging
outlet separated by a narrow throat. In effect, the Dall tube uses
stream-line bending as well as velocity head to obtain a differential
pressure larger than that produced by a standard venturi meter. Single
hole pressure taps are located at the inlet shoulder and the throat
(Figure 4). Both pressure taps can be continuously flushed with clean
water to prevent plugging from solids in the flow as done with the ven-
turi tube.'
The Dall tube is almost as accurate as the standard venturi and has a
higher head recovery, being one of the lowest permanent head loss de-
vices known. It is more sensitive to system disturbances than the ven-
turi, and straight upstream pipe runs of 40 pipe diameters or more may
be required. Although somewhat cheaper than the venturi, the Dall tube
must still be considered expensive. It is much shorter than either
38
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TABLE 5. VENTURI TUBE METER EVALUATION
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
- Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
S i rnp 1 i c i ty a nd Re 1 i ab i 1 i ty
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precal ibration
Ease of Calibration
Maintenance -of Calibration
Adaptability
Cost
Portabi 1 i ty
Scale
E3 Poor
D Poor
D High
K No
D High
D High
D High
D High
53 Poor
D High
& High
K High
D Poor
D No
D High
D High
D No
D Poor
D No
D No
D Poor
D Poor
D Poor
BHigh
52 No
D Fair Q Good
D Fair S3 Good
D Moderate 83 Slight
D Yes!
D Moderate 6i Low
D Moderate K Slight
D Moderate Eg Slight
D Medium g| Low
D Fair D Good
D Medium S! Low
D Moderate D Slight
D Moderate D Slight
D Fair SJ Good
B Yes
S3 Medi urn D Low
53 Moderate n Slight
D Yes
D Fair |g Good
IS Yes
8 Yes
D Fai r 53 Good
D Fai r 53 Good
CH Fair Q Good
D Medium D Low
D Yes
39
-------
Q_
-------
1VG^U tU^S' and thus has less of an installation re-
The throat of the Ball tube can foul, and it is not gener-
in ?aWeT extremely dirty fluids. Dall tubes are evaluated
There have also been a number of recent American proprietary develoo-
atntne S?^:1 °f/hi,C\1S the "L°-Loss" tube. ll senses the vl±£
a curte ^r^^- d ^ ^ CentrifuSal action of the liquid rounding
a curve and the impact pressure at the inlet. It is also a high head
recovery device but, unlike the Dall tube, can generally be successfully
ments VSS ^ ^^ ™* *** excePtion> the evaluation com- 7
ments of Table 6 can be assumed applicable to the "Lo-Loss" tube also.
The Gentile tube is a somewhat different venturi-type differential pres-
sure producer, in which there is a slight constricSon in tS line/
Pressure ports exist in the wall of the constriction. These ports face
in opposite directions and the effect is somewhat similar to the
nlifv^r^f P±t0t tUbe< In effeCt theSS Pit0t tubes are us*d to am-
of fL nn^ ^ PfS!fUre; Because of the type of construction and size
?L2J«P ? £ dev"e has limitations for the measurement of flow of
liquids which carry solid matter in suspension. It also suffers from
an extremely limited range (less than half that of a Dall tube) a
greater sensitivity to upstream disturbances, and less head recovery
consequently, this device will not be discussed further. ecovery»
Flow Nozzle
Various designs have been developed for flow nozzles, resulting in
characteristics that approach those of a venturi tube in one extreme
(venturi insert nozzle) and those of an orifice meter in the other fASME
long radius nozzle). More typically, a flow nozzle has an entrance
f£!fuslfr°S- aS ^ * VentUr± tUb6' bUt lacks the recovery cone
A ™fSr^;f session essentially affects the head recovery only.
A major difference (and advantage over the venturi tube) in installa-
Son^VS £at ? W n°Zzle °an be installed in pipe flanges (see Fig-
ure 5). Nozzles are less expensive than venturi tubes, but cost more
than orifice meters. In general they are more sensitive to upstream
disturbances and 20 or more pipe diameters of straight run upstream of
the flow nozzle are required for successful operation. While some de-
signs, (e.g., ASME nozzle) are quite well suited (with proper precau-
tions) for measuring liquids high in suspended solids, other (e.g.
venturi insert nozzle) are not recommended for use in such flows! due
to some aspect of their particular design that would tend to promote
plugging or clogging. Flow nozzle accuracies can approach those of
venturi tubes, especially when calibrated in place. It is also possi-
ble to use a flow nozzle in cases where a pipe (flowing full) discharges'
fSSl. ^e atmosphere. In such cases only the high pressure tap is
needed; see Figure 6. Flow nozzles as a group are evaluated in Table 7
41
-------
TABLE 6. BALL TUBE METER EVALUATION
Evaluation Parameter
Scale
1 Range
2 Accuracy
3 Flow Effects on Accuracy
4 Gravity & Pressurized Flow
Operati on
Submergence or Backwater
Effects
6 Effect of Solids Movement
7 -Flow Obstruction
8 Head Loss
9 Manhole Operation
10 Power Requirements
11 Site Requirements
12 Installation Restrictions
or Limitations
13 Simplicity and Reliability
14 Unattended Operation
15 Maintenance Requirements
16 Adverse Ambient Effects
17 Submersion Proof
18 Ruggedness
19 Self Contained
20 Precalibration
21 Ease of Calibration
22 Maintenance of Calibration
23 Adaptability
24 Cost
25 Portability
53 Poor QFair D Good
Q Poor QFair SI Good
D High Q Moderate IS Slight
K No D Yes
Q High Q Moderate IS Low
D High
D High
DHigh
SI Poor
D High
Si High
D High
Q Poor
D No
D High
D High
D No
D Poor
D No
D No
Q Poor
Q Poor
Q Poor
SI High
SI No
Si Moderate Q Slight
D Moderate SI Slight
D Medium SI Low
Q Fair D Good
Q Medium St Low
D Moderate D Slight
B) Moderate D Slight
Q Fair Sj Good
Si Yes
S! Medium Q Low
K Moderate Q Slight
D Yes
D Fair K Good
Si Yes
D Fair
SI Fai r
D Fair
Q Medi urn
SJ Good
D Good
Q Good
Q Low
D Yes
42
-------
LU
or
g
•H
•U
rt
4J
to
(U
i-H
N
N
&
I
o
•H
10
0)
t-t
60
•H
LU
o:
=3
co
Z 00
CJ3 LU
43
-------
P4
CO
I
o
•u
$
60
O
CO
cu
H
N
N
O
123
I
00
•H
44
-------
TABLE 7. FLOW NOZZLE METER EVALUATION
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
-Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precal ibration
Ease of Calibration
Maintenance -of Calibration
Adaptability
Cost
Portabi 1 i ty
Scale
£3 Poor
D Poor
D High
"H No
D High
D High
D High
D High
E9 Poor
D High
K High
D High
D Poor
D No
D High
D High
D No
D Poor
D No
D No
D Poor
D Poor
D Poor
D High
& No
D Fair DGood
D Fair gj Good
D Moderate 83 Slight
D Yes
D Moderate 53 Low
D Moderate & Slight
D Moderate C3 Slight
•"18 Medium D Low
D Fair D Good
Q Medi urn 53 Low
D Moderate D Slight
C3 Moderate D Slight
D Fair 53 Good
B Yes
D Medi urn S3 Low
63 Moderate Q Slight
D Yes
D Fair 53 Good
53 Yes
g Yes
D Fair E3 Good
D Fair SI Good
D Fair D Good
. C§) Medium D Low
D Yes
45
-------
Orifice Meters
The orifice meter is one of the oldest flow measuring devices in exist-
ence. Its differential pressure is due to a combination of velocity
head, frictional losses, and stream-line bending (acceleration). The
relative contribution is determined by whether pipe taps, vena contracta
taps, or flange taps are used. The thin plate orifice meter is the most
commonly used flow measuring device in pipes. The orifice is a round
hole in a thin flat plate that is clamped between a pair of flanges at
a point in the pipe. Although some designs have a rounded edge facing
into the direction of the flow and perhaps a short tube with the same
inside diameter as the orifice diameter extending downstream, it is
more common to use a sharp 90-degree corner on the upstream edge. The
pressure taps are located upstream and downstream of the orifice Plate.
An orifice plate can also be used at the end of a pipe flowing full and
discharging to atmosphere, in which case only a single pressure tap is
required.
Orifice meters work well with clean fluids but are not applicable, ex-
cept in a limited sense, to flows high in suspended solids due to the
tendency of solids to accumulate upstream of the orifice plate and
thereby change its calibration. There are two designs that will accom-
modate limited amounts of suspended solids. The eccentric orifice
plate has a hole which is bored off-center, usually tangent to the bot-
tom of the flow line. The segmental orifice plate has a segment removed
from the lower half of the orifice plate. In addition, there are many
special-purpose devices that are really combinations of flow nozzles
and orifice plates. These have arisen due to requirements to minimize
viscosity effects in heavy fluids, etc.
Orifice plates are the most sensitive of all the differential pressure
devices to effects of upstream disturbances, and it is not uncommon to
need 40 to 60 pipe diameters of straight run upstream of the installa-
tion. Orifice plates also produce the greatest head loss as can be
seen by the comparison curves of Figure 7. Orifice meters can be quite
accurate, with ±0.5% or better achievable when calibrated in place.
They are lowest in cost of all the differential pressure producers. Be-
cause of nonlinear flow effects, their usable range is small (on the
order of 5:1) unless rated in place. Orifice meters are evaluated as a
group in Table 8.
Centrifugal Meters
Flow acceleration induced in a fluid going around a bend (such as an
elbow) produces a differential pressure that can be used to indicate
flow. The pressure on the outside of an elbow is greater than on the
inside, and pressure taps located mid-way around the bend (i-e., 45 de-
grees from either flange) can be connected to a suitable secondary
46
-------
PERMANENT HEAD LOSS
(PERCENT OF MEASURED DIFFERENTIAL)
— ' ro co .p. en cr> ^i oo UDC
o o o o o o o o o o c
-^
X
FLOW
\
LONG CONE V
— -.
XN
S
NO;
^
ENTU
— ~
ORIFICE
s^FLANGE
S>
"RT*
**i
S
\
-siio
•*--. .
WITH
TAPS
s
V.
\
\
RT..CONE
VENT
DALL TUBE
--H -h
•URI
.1 .2 .3 .4 .5.6-7.8 .9 1
DIAMETER RATIO
Figure 7. Head Loss of Differential Pressure Meters
47
-------
TABLE 8. ORIFICE METER EVALUATION
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precal ibration
Ease of Calibration
Maintenance of Calibration
Adaptability
Cost
Portability
Scale
E3 Poor D Fair CD Good
n Poor 55 Fair D Good
D High D Moderate S3 Slight
B No D Yes
D High D Moderate 63 Low
81 High D Moderate D Slight
KJHigh D Moderate D Slight
K High D Medium D Low
53 Poor DFair D Good
D High D Medium 81 Low
S3 High D Moderate D Slight
D High D Moderate 53 Slight
D Poor D Fair SI Good
D No » Yes
81 High D Medium D Low
DHigh 8) Moderate Q SI i ght
D No D Yes
D Poor 81 Fair D Good
D No 81 Yes
D No 8! Yes
D Poor DFair Kl Good
SI Poor D Fair D Good
D Poor D Fair D Good
DHigh D Medium 81 Low
D No H Yes
48
-------
element for indicating or recording. Cortelyou (14), Taylor and
McPherson (15), and Replogle, et. al. (16) provide fuller discussions
of centrifugal meters. The turbine scroll case and guide vane speed
ring do not appear at all well suited for storm or combined sewer ap-
plications, and so will not be discussed.
The elbow meter may have some application,,^ .existing pipe systems. It
should not be considered as a candidate for accurate flow measurement
in new construction, however. It is inexpensive, offers no additional
head loss, can tolerate solids, if the pressure taps are flushed (see
venturi discussion), and is not especially subject to calibration
shifts. If calibrated in place, accuracies of about ±1 or 2% (or bet-
ter in some cases) may be achieved. More typically, accuracies of 3 to
10% are encountered. Unless calibrated in place, straight pipe runs of
at least 20 pipe diameters should be provided both upstream and down-
stream of the elbow.. The usual rangeability is around 3:1. Elbow me-
ters are evaluated in Table 9.
Impact Tube
In the impact tube, kinetic energy (due to fluid velocity) is converted
into potential energy (stagnation pressure) and the differential pres-
sure (as compared with static pressure in the pipe) is related to flow
velocity at the point of measurement. Figure 8 depicts the two essen-
tial ingredients and a particular construction known as the Prandtl-
Pitot tube. Alternate designs consist of essentially the same two basic
ingredients (impact tube and pressure tube) and differ only in the de-
tails of their construction. H. Pitot's original design (1732) had two
tubes, one of which was bent through 90 degrees at its lower end and
positioned facing into the flow. H. Darcy's design (1852) had each
tube bent through 90 degrees, with one facing upstream (impact) and the
other facing downstream. In addition to the Prantdl design (with its
hemispherical head) which is popular today, especially in Europe, is the
Brabbe design with a conical head, which is popular in the United States
and United Kingdom. In another design, two parallel small-diameter
tubes are beveled at their open ends, one pointing upstream (impact)
and one pointing downstream (static).
It must be emphasized that impact tubes measure point velocity only.
Flow is calculated by multiplying the mean velocity of the fluid by the
area of the pipe cross-section. For pipes flowing full and under pres-
sure it has been determined that the mean velocity of flow is about 83%
of the velocity in the center of the pipe and it occurs at a point ap-
proximately one-fourth the radius from the wall to the center. Velocity
close to the pipe wall is only about one-half the velocity at the cen-
ter. To avoid upset of such normal velocity distributions it is neces-
sary to have a straight pipe run of some 15 to 50 pipe diameters in
length upstream of the measuring point. Alternately, velocity traverses
49
-------
TABLE 9. ELBOW METER EVALUATION
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site .Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precal ibration
Ease of Calibration
Maintenance of Calibration
Adaptabi 1 i ty
Cost
Portabi 1 ity
Scale
53 Poor DFair D Good
D Poor 53 Fair D Good
D High D Moderate 53 Slight
53 No D Yes
D High D Moderate 53 Low
D High D Moderate 53 Slight
fj High D Moderate 53 Slight
D High D Medium 53 Low
53 Poor D Fair D Good
D High D Medium 58 Low
53 High D Moderate D SI i ght
D High D Moderate 53 Slight
D Poor DFair 53 Good
D No SI Yes
D High D Medium gj Low
DHigh 53 Moderate D SI i ght
D No D Yes
D Poor D Fair 53 Good
D No 53 Yes
63 No D Yes
D Poor K Fair D Good
D Poor D Fair 53 Good
D Poor D Fair D Good
DHigh D Medium 53 Low
S3 No D Yes
50
-------
"0.
H-
LU
CQ
o_
I
ai
I
o
4->
•H
H
3
OO
0)
60
•H
51
-------
can be run to determine the point of mean velocity. Such an approach
also allows the pitot tube to be used in conduits of noncircular cross-
section and under open channel flow conditions.
With very high velocities dynamic instability may occur, and erroneous
readings result from the tube vibrations. However, the chief disadvan-
tage of most pitot tube designs is that rather sophisticated secondary
devices are required to accurately determine the pressure differential
which may be quite small at low velocities, e.g., less than 0.3 m/s
(1 fps). This makes continuous flushing secondary devices more diffi-
cult to employ and, to the writers' knowledge, no such attempt has yet
been made.
Therefore, impact tube type devices are generally not satisfactory for
measuring wastes containing appreciable quantities of suspended solids
because of the possibility of plugging of the small openings in the
tubes. In view of this, the vulnerability to damage arising from their
intrusive nature, and the difficulties in applying them in open chan-
nel flows of varying depths, no further discussion will be given.
Linear Resistance
Linear resistance meters use friction losses to create a differential
pressure that can be related to flow rate. The resistance of a long
pipe section may be used, but one or more fine tubes in parallel (cap-
illary tube) or a section of pipe packed with steel wool, granular ma-
terials, or the like (porous plug) are more typical, Fleming and
Binder (17), Greef and Hackman (18), and Severs and Binder (19) discuss
various approaches and designs. Accuracies to 1% of the reading and
ranges of 10:1 may be achieved. There is no pressure recovery. Be-
cause of the impracticality of utilizing such devices for measuring
storm or combined sewer flows, they will not be discussed further.
VARIABLE AREA
Whereas differential pressure flow measuring devices are characterized
by the invariability of the area ratio, in variable area meters the
magnitude of the varying cross-sectional area is the measure of the
rate of flow. A differential pressure does exist, but it is relatively
constant. Variable area flowmeters may be divided into two main groups,
valve type (e.g., hinged or sliding gate) and float type (e.g., cone-
and-float). Variable area devices were invented by E. A. Chameroy, who
patented an instrument constituting a prototype of the rotameter in
1868, and G. F. Deacon, who was given a patent for a cone-and-disc
flowmeter in 1875. Sir J. A. Ewing was the first to apply a tapered
glass tube in a liquid rotameter in 1876, and in 1910 K. Kupper intro-
duced inclined slots on the upper rim of the float and first used the
term rotameter for this type of device, because of the rotary motion of
52
-------
the float. Discussions of such devices are given by Kehat (20) and
Gilmont and Roccanova (21). Accuracies to ±1% of full scale and ranges
to 10:1 may be achieved. However, to maintain accuracy in a rotameter
it is absolutely essential that both the tube and the float be kept
clean. Thus, a storm or combined sewer application would be inappro-
priate and, consequently, they will not be discussed further.
HEAD - AREA
Flow measurement devices in this classification are characterized by a
simultaneous variation of both flow cross-sectional area and head.
These parameters do not vary indpendently, however, and it is the func-
tion of the primary device to produce a flow that is characterized by a
known relationship (usually nonlinear) between a liquid level measure-
ment (head) at some location and the overall discharge. This relation-
ship or head-discharge curve is called the rating for the particular
structure or device. Since these devices implicitly require a free
surface, they are only suitable for open channel flows.
The change in elevation of the free surface is measured by the secondary
device which may also convert stage to discharge automatically. Still-
ing wells are often used, being connected by suitable taps to the loca-
tion in the primary device where knowledge of the flow depth is desired.
The secondary device then monitors the relatively stable surface level
of the fluid in the stilling well. To avoid the necessity of frequent
cleaning of the stilling well and to help prevent plugging of the tap,
fresh water is frequently trickled into the well at a rate sufficient
to ensure that sewage isn't likely to enter. An overpressure of at
least 0.003 meter (0.01 ft) is usually required to keep the well and tap
clear, but in some cases greater cleaning flows along with frequent
flushing will be necessary.
Slope-Area Method
In this technique, the flow conduit itself serves as the primary device.
Historically, it has been used to obtain instantaneous discharges rather
than continuous records. Some discharge relationship such as the
Manning•formula is used to relate depth to flow rate. For best results,
a straight course of channel of at least 61 meters (200 ft) and prefer-
ably up to 305 meters (1000 ft) in length is required. It should be
nearly uniform in slope, cross-section, and roughness and free of rap-
ids, abrupt falls (dips), sudden contractions or expansions, and tribu-
tary inflows.
The Manning formula requires knowledge of the channel cross-section and
liquid depth so that the flow cross-section and hydraulic radius can be
calculated. It also requires knowledge of the slope of the water sur-
face (not the conduit invert). This slope may be determined by dividing
53
-------
the difference in the water surface elevations at the two ends of the
course, as determined by secondary devices carefully referenced to a
common datum level, by the length of the course. Also required in the
Maiming formula is a roughness factor which depends upon the character
of the conduit lining and the depth of flow (i.e., it is not constant
for a given channel). Because the proper selection of the roughness
factor is at best an estimate, the discharge determined by the slope-
area method is only an approximation, and it should be used only where
accuracy requirements are low.
All too often, the slope-area method is applied by measuring the flow
depth at a single point and using the slope of the conduit invert in
the Manning formula. For nonuniform or unsteady flow, the water sur-
face slope will be changing and will certainly not be equal to the
channel slope. The Manning formula was not intended for use under such
conditions. It is preferable to perform calibration in place and de-
velop an empirical rating curve for each measuring site. The slope-
area method is evaluated in Table 10.
Weirs
A weir is essentially an overflow structure or dam built across the
flow conduit to measure the rate of flow. For a weir of a given size
and shape with free-flow, steady-state conditions and proper weir-to-
pool relationships, only one depth of liquid can exist in the upstream
pool for a given discharge. Discharge rates are computed by measuring
the vertical distance from the crest of the overflow part of the weir
to the water surface in the pool upstream of the crest and referring to
the rating curve for the particular weir or class of weirs at hand.
Thus, a weir may be thought of as a device for shaping the flow of the
liquid in a definite way such as to allow a single depth reading to be
uniquely related to a discharge rate. Weirs may be further categorized
as being either sharp-crested or broad-crested; each will be discussed
in turn.
Sharp-Crested Weirs - When the top edge of the weir is thin or beveled
with a sharp upstream corner (similar to a thin plate orifice) so that
the water does not contact any part of the weir structure downstream
but, rather, springs past it, the weir is called a sharp-crested weir.
Figure 9 depicts some common weir terms and their relationships. As
noted, the minimum height of the weir crest should be at least two, and
preferably three, times the maximum head expected over the weir. The
contraction of the nappe (overfalling stream) after springing clear of
the sharp crest is termed crest contraction. If the bottom of the ap-
proach channel is not far enough below the crest of the weir, the crest
contraction is partially suppressed, and standard weir tables cannot be
used. The slight drop in the liquid surface which begins upstream from
the weir a distance of at least twice the head on the crest is called
54
-------
TABLE 10. SLOPE-AREA METHOD EVALUATION
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
- Fl ow Obstruction
.Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precal ibration
Ease of Calibration
Maintenance of Calibration
Adaptabi 1 i ty
Cost
Portability
Scale
D Poor
& Poor
G3 High
& No
K High
D High
D High
D High
D Poor
D High
D High
D High
D Poor
D No
D High
D High
D No
Q Poor
D No
53 No
D Poor
D Poor
D Poor
K High
^ No
SI Fair ID Good
D Fair Q Good
D Moderate D Slight
DYes
ICO
D Moderate Q Low
D Moderate 53 Slight
D Moderate SI Slioht
D Medi urn 53 Low
D Fair 58 Good
D Medi urn 53 Low
53. Moderate Q S]ight
D Moderate 63 Slight
D Fair K Good
K Yes
D Medi urn S3 Low
gj Moderate Q Slight
DYes
D Fair j§3 Good
& Yes
D Yes
K Fair D Good
D Fair S3 Good
D Fair Q Good
D Medium D Low
D Yes
55 ,
-------
o
a.
to
-------
surface contraction or drawdown. To avoid sensing the effects of draw-
down, the gaging point should be located upstream of the weir crest a
distance of at least three, and preferably four, times the maximum head
expected over the weir.
When the water level in the downstream channel is sufficiently below
the crest to allow free access to the area beneath the nappe, say at
least 15 cm (6 in.), the flow is said to be free (critical). When the
water level under the nappe rises above the crest elevation, the flow
may be considered submerged. This may or may not affect the discharge,
and there is some question whether dependable measurements can be ex-
pected in this range. As the water level downstream rises appreciably
over half of the head on the crest, the degree of submergence will ap-
preciably affect the rate of flow. To determine the rate of flow under
such submerged (sub-critical) conditions, both the upstream and down-
stream heads must be measured and reference made to submerged flow ta-
bles. A very good treatment of submerged weirs is given by Skogerboe,
et al (22).
Many different geometries have been used for the notch in the weir
plate that shapes the nappe and thereby allows the rating curve to be
developed. Some sharp-crested weir profiles are depicted in Figure 10.
Rectangular Weirs - One of the oldest and most common is the rectangular
weir, which is used in one of two configurations. When the distances
from the sides of the weir notch to the sides of the channel (weir pool)
are great enough (at least two or three times the head on the crest) to
allow the liquid a free, unconstrained lateral approach to the crest,
the liquid will flow uniformly and relatively slowly toward the weir
sides. As the flow nears the notch it accelerates, and as it turns to
pass through the opening, it springs free laterally with a resulting
contraction that results in a jet narrower than the weir opening. Under
such conditions the weir is called a contracted weir. If a rectangular
weir is placed in a channel whose sides also act as the sides of the
weir, there can be no lateral contractions and the weir is called a
suppressed weir. Special care must be taken with these weirs to assure
proper aeration beneath the nappe. This is usually accomplished by
placing vents on both sides of the weir box under the nappe.
V-Notch Weirs - The triangular or V-notch sharp-crested weir was devel-
oped to allow accurate measurement of small flows. The angle (2a) most
commonly used is 90 degrees. Because a V-notch weir has no crest
length, the head required for a small flow through it is greater than
that required for other common types of weirs. This is an advantage
for small discharges in that the nappe will spring free of the crest,
whereas it might cling to the crest of another type of profile and make
the measurement worthless. The V-notch weir is the best profile for
measuring discharges less than 28 t/s (1 cfs) and is as accurate as any
57
-------
"Vv X"
RECTANGULAR
2a
TRIANGULAR OR V-NOTCH
2a
TRAPEZOIDAL (INCLUDING
CIPOLLETTI)
2a
INVERTED TRAPEZOIDAL
POEBING
APPROXIMATE EXPONENTIAL
APPROXIMATE LINEAR
PROPORTIONAL OR SUTRO
Figure 10. Various Sharp-Crested Weir Profiles
58
-------
other profile for flows up to 283 l/s (10 cfs). Sufficient head for
these higher flow rates may pose a limitation for many sites, however,
and in practice 113 l/s (4 cfs) is often a more realistic upper bound.
Trapezoidal Weirs - Trapezoidal weirs of varying side angles have been
used to measure liquid flows, but the most common one by far is the
Cipolletti, whose sides incline outwardly at a slope of one horizontal
•to four vertical. Although the Cipolletti weir is a contracted weir,
its discharge occurs essentially as though its end contractions were
suppressed; thus the width of the crest can be used for flow calcula-
tions. It offers a wider range than either the rectangular or V-notch
weir.
Other Weirs - Other weir profiles, as indicated in Figure 10, have been
developed to achieve certain head-discharge relationships or to achieve
some benefit peculiar to a particular type of site. None of these has
been used or investigated as extensively as those discussed above, and
consequently will not be dealt with here. There is one class of spe-
cial profiles, however, that at least deserves passing mention. For
situations where the normal range of discharges at a site might be
easily handled by a V-notch weir but occasional larger flows would re-
quire, for example, a rectangular weir, the two profiles have been com-
bined to form what is termed a compound weir, Figure 11.
Such a weir has a disadvantage, however. While flows may be measured
rather accurately when the weir is essentially behaving as a V-notch
weir, Figure lla, or as a rectangular (either suppressed or contracted)
weir, Figure lib, there will be a transition zone where accurate read-
ings will be difficult to achieve. When the discharge begins to exceed
the capacity of the V-notch, thin sheets of liquid will begin to pass
over the wide horizontal crests in a less than predictable fashion.
This causes a discontinuity in the discharge curve. The size of the
V-notch and the size of the rectangular notch should be selected so
that discharge measurements in the transition range will be those of
minimum importance.
Discussion - In order to have a satisfactorily-operating sharp-crested
weir, the following general requirements should be considered:
a.
b.
...upstream face of the structure should be smooth and
perpendicular to the axis of the channel in both hori-
zontal and vertical directions.
The crest should be level, with a sharp right-angled edge
on its upstream face; its thickness (in the direction of
the flow) should not exceed 3 mm (1/8 in.) and should
preferably be between 1 to 2 mm (0.04 to 0.08 in.).
Knife edges should be avoided as they are too difficult
to maintain.
59
-------
Ca)
\/
Cb)
Figure 11. Compound Weir
60
-------
c. The height of the crest above the approach channel bottom
should never be less than 0.3m (1 ft); the minimum head
should be at least 0.06m (0.2 ft). For- a contracted
rectangular weir, the distance from the sides of the
weir to the sides of the approach channel should never
be less than 0.3m (1 ft).
d. The cross-sectional area of the approach channel should
be at least 8 times that of the nappe at the crest for a
distance upstream of 15 to 20 times the height on the
crest. If the weir pool is smaller than this, the veloc-
ity of approach may be too high and the gage readings too
low; necessitating head corrections for velocity of
approach.
e. The connection between the weir and the channel must be
waterproof; i.e., all flow must pass over the weir, not
around or under it.
In general, the sharp-crested weir is an inexpensive, accurate primary
flow measuring device that is fairly easy to install. Laboratory accu-
racies approaching 1% of full scale have been achieved, but 5% is more
typical of most good field installations. The operating range of a
sharp-crested weir depends upon its profile, but 20:1 may be considered
typical for many installations. The sharp-crested weir suffers from
several deficiencies when considered for a storm or combined sewer ap-
plication, however. It may well require construction of a weir box to
obtain the proper flow approach to the weir. Sufficient head may not
be available at the desired measuring site, and the head loss will be
at least equal to the head measured. The crest of the weir must be
kept clean. Fibers, stringy materials, and larger particles tend to
cling to the crest and must be removed periodically.
Finally, because of its damming action, the sharp-crested weir will
suffer from settling and accumulation of suspended solids in the ap-
proach channel behind the upstream face. This will lead to inaccurate
readings. Some weirs have been constructed with a watertight door in
the face on the channel bottom. When the door is opened the flow will
go through this passage and tend to scour away collected sediment.
However, most attempts to use charp-crested weirs in extremely dirty
flows have been less than fully successful. Sharp-crested weirs are
evaluated as a group in Table 11.
Submerged Orifices - The use of thin-plate orifice meters in pressur-
ized conduit flow has already been discussed. In open channel flow, an
orifice operates as a head-area device; in fact, if the water level
drops below the top of the opening, it behaves like a weir and has been
included here for that reason. Basically; it consists of a predeter-
mined, sharp-edged opening in a plate affixed to a wall or other
61
-------
TABLE 11. SHARP-CRESTED WEIR EVALUATION (ALL
PROFILES)
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operati on
Submergence or Backwater
Effects
Effect of Solids Movement
Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precal i bration
Ease of Calibration
Maintenance of Calibration
Adaptabi 1 i ty
Cost
Portability
Seal e
D Poor
C3 Poor
D High
KJ No
D High
B High
63 High
18 H i g h
D Poor
D High
D High
D High
D Poor
D No
63 High
D High
D No
D Poor
D No
D No
D Poor
53 Poor
D Poor
D High
D No
63 Fair
63 Fai r
8! Moderate
53 Moderate
D Moderate
D Moderate
D Medi urn
53 Fair
D Medi urn
S! Moderate
53 Moderate
D Fair
D Medi urn
SI Moderate
D Fair
D Fair
D Fair
D Fair
D Medi urn
D Good
D Good
D Slight
D Yes
D Low
D Slight
D SI ight
D Low
D Good
53 Low
D Slight
D S 1 i g h t
SIxGood
63 Yes
D Low
D Slight
D Yes
63 Good
63 Yes
63 Yes
53 Good
D Good
D Good
63 Low
Kl Yes
62
-------
structure and through which flow may occur. Although any shape hole
can be used, the most common are either circular or rectangular. Know-
ledge of the size and shape of the hole, the head acting on it, and the
discharge condition (i.e., freely into air or under water) allows de-
termination of the flow rate. Early orifices often discharged freely
into air, but were practically abandoned as weirs become more common
(and more extensively studied) because of the considerable head loss
necessitated by their use.
The fall requirement is reduced if the orifice is lowered in the struc-
ture and discharges in the submerged condition. The submerged orifice
is used where the head loss of a weir cannot be tolerated and a flume
cannot be justified because of cost or some special conditions. Like
the weir, a submerged orifice may be either contracted or suppressed.
Suppression may occur on part (e.g., the bottom of a rectangular orifice
flush with the channel flow) or all of the perimeter.
In selecting a channel site for use of a submerged orifice meter the
distance from the edges of the orifice to the bounding surfaces of the
channel, both on the upstream and downstream sides, should be greater
than twice the least dimension of the orifice if contraction is to be
assured. Also, the cross-sectional area of the water prism 6 to 9 m
(20 to 30 ft) upstream from the orifice should be at least 8 times the
cross-sectional area of the orifice. Velocity of approach to the ori-
fice should be negligible, or correction must be made for velocity head.
An orifice should not be used in situations where weeds and trash are
prevalent, as accumulation of submerged debris or of sand and sediment
upstream may prevent accurate measurements. A clogged condition of an
orifice is less visible than that of a weir and, so, may go undetected.
Because of these factors and the small data base as compared to weirs
and flumes, an orifice is not generally recommended for measurement of
stormwater or combined sewage, even though its limited range of flow
can be increased with the use of a metergate, which basically is a
modified submerged orifice arranged so that the orifice is adjustable
in cross-sectional area. Consequently, no further discussion or evalu-
ation will be given.
Broad-Crested Weirs - If the weir notch is mounted in a wall too thick
for the water to spring past, the weir is called broad-crested. A wide
variety of shapes can be included under broad-crested weirs, and a wide
variety of discharge coefficients will be encountered. A few such
shapes are depicted in Figure 12. Broad-crested weirs, in practice,
are usually pre-existing structures, such as dams, levees, diversion
structures, etc. Discharge coefficients and discharge tables are usu-
ally obtained by calibrating the weir in place or by model studies.
Broad-crested weirs are sometimes used where the sharp-crested weir
causes undue maintenance problems. For example, problems with impact,
63
-------
t\
11
o
_I
u_
64
-------
abrasion, silting, etc. might indicate the need for a broad-crested
weir. Broad-crested weirs are usually made of concrete or similar ma-
terial and are not considered portable. In actuality, the notion of a
broad-crested weir, which simply denotes a channel contraction made by
a sill on the channel bottom, merges into that of a critical-depth
flume. When properly designed and constructed, the broad-crested weir
is governed by the same basic flow equations. Broad-crested weirs are
evaluated in Table 12.
Flumes
Although the term "broad-crested weir" is widely used to denote a chan-
nel constriction made by some sort of a sill on the channel bottom,
other open channel constrictions, generally called flumes, have been
used to measure discharges since the beginning of the century. Most
flumes in common use today can be traced to one of three early design
sources: rectangular English flumes based upon early work in India
around 1908-1914 and the writings of F. V. A. E. Engal (23); the
Parshall flume whose forerunner, a venturi flume developed by Cone (24),
was extensively modified and tested by Parshall (25, 26); and flumes of
the type first developed by Palmer and Bowlus (27).
Flumes can be categorized as belonging to one of three general families
depending upon the state of flow induced - subcritical, critical, or
supercritical. By definition the critical flow state is that for which
the-Froude number is unity. This is the state of flow at which the spe-
cific energy is minimum for a given discharge. When critical depth
occurs in a channel (either at a constriction or in a regular cross-
section) , one head measurement can indicate discharge rate if it is
made far enough upstream so that the flow depth is not affected by the
drawdown of the water surface as it heads to achieve the critical state
of flow.
Kilpatrick (28) identifies six approaches employed in various flume de-
signs, and these will be briefly treated below following his discussion.
Type I, tranquil-flow, small-width reduction flumes are typical of the
earliest measuring flumes and are depicted in Figure 13. Subcritical
flow enters the flume, and the side contractions reduce the width, re-
sulting in an increase in unit discharge. Because there is no change
in bed elevation, and minor energy loss, the specific energy in the
throat is about the same as in the approach. With constant specific
energy, the effect of a small width contraction is a lowering of the
water surface in the throat but, owing to the small degree of contrac-
tion, critical depth is not accomplished. It is necessary in this type
of flume to measure the head in both the approach section and in the
throat.
65
-------
TABLE 12. BROAD-CRESTED WEIR EVALUATION
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precal ibration
Ease of Calibration
Maintenance of Calibration
Adaptabi 1 i ty
Cost
Portabi 1 i ty
Scale
D Poor
n Poor
D High
Si No
E9 High
8) High
D High
D H i g h
D Poor
D High
D High
D High
D Poor
D No
D High
D High
D No
D Poor
D No
8J No
D Poor
D Poor
D Poor
D High
SI No
8j Fair D Good
81 Fair D Good
D Moderate Si Slight
D Yes
D Moderate Q Low
D Moderate D Slight
63 Moderate D Slight
81 Medi urn D Low
D Fair 8! Good
D Medi urn SI Low
8! Moderate D Slight
81 Moderate D Slight
D Fair 62 Good
8l Yes
D Medium SI Low
81 Moderate D Slight
D Yes
D Fair 81 Good
81 Yes
D Yes
SI Fair D Good
SI Fair D Good
D Fair D Good
D Medi urn 8] Low
D Yes
66
-------
Type II, critical-flow, large-width reduction flumes are illustrated in
Figure 14 and differ from Type I flumes only in that the throat contrac-
tion is sufficient to ensure that critical flow is achieved. This gives
the advantage of requiring measurement at only one location, which may
be either in the immediate approach to the flume or in the throat.
Measurement in the approach will yield a more sensitive stage-discharge
relationship because changes in discharge will result in greater changes
in depth in subcritical flow than would like changes in discharges in
critical flow. Unfortunately, the stage-discharge relationship in the
approach may be unstable due to approach conditions such as scour and
fill. Consequently, stage is usually measured in the throat to allevi-
ate influence from either upstream or downstream. Approach conditions
can have some effect on flow in the throat, but it is generally insig-
nificant. The site at which critical depth is first reached may shift
further downstream into the throat as a result of excessive deposition
in the approach. For this reason, and to avoid possible flow separa-
tions near the entrance, stage measurements in the throat should not be
too close to the entrance. Flow close to critical is very unstable,
constantly attempting to become either subcritical or supercritical.
Therefore, this type of flume is seldom encountered in practice.
Type III, tranquil-flow, small-increase-in-bed elevation flumes are
shown in Figure 15. Because of the requirement for dual gaging points
and the partial barrier to the approaching flow, which will encourage
deposition of suspended solids, such designs are not commonly used.
Type IV, supercritical-flow, width-reduction, steep-slope flumes are
illustrated in Figure 16. For flumes that have bed slopes of near zero,
critical depth is the minimum depth possible in the flume. Further con-
traction, £either at the sides or bottom, will not produce supercritical
flow. This can be accomplished only by increasing the available spe-
cific energy from the approach into the throat. For Type IV flumes,
the bed is placed on a slope sufficient to cause the required increase
in specific energy to produce supercritical flow in the throat. It may
be thought of as a Type II flume tilted in the downstream direction.
Only a single gaging point is required.
Type V, supercritical-flow, width-reduction, drop-in-bed flumes are
depicted in Figure 17. Here the increase in specific energy required
to achieve supercritical flow is provided by a sudden drop in the bed.
Measurement of head is made either in the throat or the approach. A
discharge rating based upon measurements in the region of supercritical
flow, while not as sensitive as compared with measurements in subcriti-
cal flow, is the least influenced by disturbances either upstream or
downstream, and hence is apt to be the most stable. Similarly, such
flumes are the most capable of stable operation up to high submergences.
67
-------
FLOW
DUAL GAGING
POINTS
PLAN VIEW
ENERGY LINE
WATER SURFACE
ELEVATION
CRITICAL
DEPTH LINE
Figure 13. Type I Flume - Critical Flow Contraction Obtained by
Small Width Reduction, Horizontal Bed
Y/////////////////S
FLOW
ELEVATION
ALTERNATE
GAGING POINTS
PLAN VIEW
ENERGY LINE
WATER SURFACE
CRITICAL
DEPTH LINE
Figure 14. Type II Flume - Critical Flow Contraction Obtained by
Large Width Reduction, Horizontal Bed
68
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Figure 16. Type IV Flume - Supercritical Flow Contraction Obtained
by Width Reduction and Sloping Bed
FLOW'
ELEVATION,
PLAN VIEW
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GAGING POINTS
ENERGY LINE
WATER SURFACE
CRITICAL
DEPTH LINE
y////////////////////'
Figure 17. Type V Flume - Supercritical Flow Contraction Obtained
by Width Reduction and Drop in Bed
70
-------
Type VI, supercritical-flow, steep-slope flumes are illustrated in Fig-
ure 18. Here there is no contraction, the increase in specific energy
necessary for achieving supercritical flow being produced simply by
producing sufficient downstream slope. Although a slope of one degree
is usually sufficient to produce critical depth in the vicinity of the
upstream edge of the apron, waves and disturbances are apt to be numer-
ous downstream. For this reason slopes on ordinary concrete aprons
will more typically range from 2 to 5%.
Site Selection - A few recommendations for the selection of gaging sites
apply in general to all types of commonly-encountered flumes. The
flumes should be located in a straight section of channel without bends
immediately upstream. The approaching flow should be well distributed
across the channel, and relatively free of turbulence, eddies, and
waves. Generally, a site with high velocity of approach should not be
selected. But, if the water surface just upstream is smooth with no
surface boils, waves, or high-velocity current concentrations, accuracy
may not be greatly affected by velocity of approach.
Consideration should be given to the height of upstream banks, noting
their ability to sustain the increased depth caused by the flume in-
stallation. Although less head is lost through flumes than over weirs,
particularly if flat-bottomed flumes are used, losses may be signifi-
cant with large installations. The possibility of submergence of the
flume due to backwater from downstream must also be investigated, al-
though the effect of submergence upon the accuracy of most flumes is
much less than is the case with weirs.
Subcritical (Venturi) Flumes - Subcritical flumes are called true ven-
turi type flumes by some researchers, e.g.,"Replogle (8), probably be-
cause of their requirement for the measurement of flow levels at two
positions. The Type I and III flumes discussed earlier are examples of
designs of such devices. Because of their advantage of requiring only a
single measurement, supercritical^flumes are generally preferred design
approaches and, consequently, Subcritical flumes are not often installed
today. They are evaluated in Table 13. ,
Parshall Flume - The development of many early flumes arose from the
need to measure irrigation flows, and the Parshall flume is no excep-
tion. The earlier designs were Types I, II, and III flumes, and the
essential change introduced by Parshall was a drop in the floor which
produced supercritical flow through the throat (Type V). Today the
Parshall flume is the most widely used primary device in the head-area
classification for the measurement of sewage and other wastewater. The
configuration and standard nomenclature for Parshall flumes is given in
Figure 19. For a given throat width (W), all other dimensions are rig-
idly prescribed. Since the rating tables for Parshall flumes are based
upon extensive and meticulous research, faithful adherence to all dimen-
sions is necessary to achieve accuracy.
71
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72
-------
TABLE 13. SUBCRITICAL (VENTURI) FLUME EVALUATION
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects,
Submersion Proof
Ruggedness
Self Contained
Precal ibration
Ease of Calibration
Maintenance of Calibration
Adaptability
Cost
Portabi 1 ity
Scale
D Poor
D Poor
D High
81 No
D High
D High
D High
DHigh
D Poor
D High
D High
D High
D Poor
D No
D High
D High
D No
D Poor
D No
D No
D Poor
O Poor
D Poor
D High
&! No
SI Fair D Good
SI Fair D Good
D Moderate S3 Slight
D Yes
D Moderate O Low
D Moderate Bl Slight
D Moderate SI Slight
D Medi urn S) Low
S3 Fair D Good
D Medi urn 81 Low
SI Moderate D Slight
D Moderate H Slight
D Fair 8! Good
81 Yes
D Medium 63 Low
18 Moderate Q Slight
D Yes
D Fair E) Good
SI Yes
K Yes
D Fair Sj Good
D Fa.i r SI Good
D Fair D Good
SJ Medi urn Q Low
D Yes
73
-------
NOTE: 7.6cm (3in) TO 2.4m (8ft) FLUMES HAVE
ROUNDED APPROACH WINGWALLS
ANGLE
. SECTION L-L
ANGLE
LEGEND: .
W Size'of flume, In inches or feet.
A Length of side wall of converging section.
2/3A Distance back from end of crest to gage point.
B Axial length of converging section.
C Width of downstream end of flume.
D Width of upstream end of flume.
E Depth of flume.
F Length of throat.
G Length of diverging section.
K Difference in elevation between lower end of flume and crest.
H Depth of depression in throat below crest.
R Radius of curved wing wall.
H Length of approach floor.
P Width between ends of curved wing walls.
X Horizontal'distance to Hfa gage point from low point in throat.
Y Vertical distance to Hb gage point from low point in throat.
Figure 19. Configuration and Standard Nomenclature for
Parshall Flumes
74
-------
The earlier Parshall flumes were developed in sizes (throat widths)
ranging from 7.6 cm (3 in.) to 2.4m (8 ft). More recently, Robinson
(29) has calibrated Parshall flumes of 2.5 cm (1 in.) and 5.1 cm (2 in.)
in size. Flumes with throat widths of 3 to 15m (10 to 50 ft) have been
constructed and field calibrated. Head-discharge ratings are thus
available for a large range in throat width. Table 14 is presented to
give the reader a "feel" for the dimensions and capacities of all sizes
of standard Parshall flumes.
Flow through a Parshall flume may be either free or submerged. In free
flow, only the upstream head (Ha) need be measured, and this condition
is favored for accurate measurement. Where free-fall conditions exist
for all flows, the downstream (Hb) may be omitted and the entire di-
verging section left off if desired, assuming channel erosion is no
problem. This simplification has been used in the design of small port-
able Parshall flumes.
Submerged flow exists when the water surface elevation downstream of
the flume is high enough to affect the head and retard the rate of dis-
charge. The degree of submergence is indicated by the ratio of the
downstream head to the upstream head (Hb/Ha). If the ratio is greater
than 0.6 for flumes under 0.3m (1 ft) or 0.7 for flumes in the 0.3 to (
2.4m (1 to 8 ft) range, flow must be considered to be submerged and
corrections must be made according to the degree of submergence. A
complete treatment of the subject is given by Skogerboe, et al (30, 31).
Small solids in suspension are readily carried through Parshall flumes
and do not affect the measurement accuracy, which should range between
1.5 percent (virtually the best obtainable) to 5 percent (more typical
of good field installations). Errors greater than this are frequently
found, the chief causes being either dimensional inaccuracies or im-
proper flow conditions. Although Parshall flumes are self-cleaning,
large rocks and other debris in the flow may cause problems. Kilpatrick
(28) notes that, "it& uAe. on filaAhy, co66£e-4^ewn .a-tteama ha* be.e,n n.oJL-
Otlvely u^uccei^ae." Another problem with the use of a Parshall flume
in measuring dirty flows such as sewage is that sometimes the installa-
tion must differ from the standard so as to prevent deposition of mate-
rial upstream from the flume. Such non-standard entrance transitions
can result in discharges that are quite different from standard values
as pointed out by Chen, et al (32).
The head loss required for flow measurement with a Parshall flume is
quite small. There must be a way to achieve the required drop in the
floor, however, and this will eliminate some sites from consideration.
Parshall flumes are evaluated in Table 15.
Palmer-Bowlus Flume - Flumes of the type first suggested and developed
by Palmer and Bowlus (27) are a form of Type IV flume, being dependent
75
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£ SSSSo 000000000000-0 0,0 00
£ 0 ' " 1-^ i-^ tMCMCMCJCMtMCJC^tMtOmTUJtOlOUJ^O
t; p:ss§s . 5 s s s s ss s s- s o o i°'~a>0'^:^^S°SSSg
2 4JOWOOOOOOO
•g ,-cvjw^o. S ^^~"«1»«''^'»12~!2Sa°*S
(U O)
3
0) O
+J -O
O) (O
a) s-
3 3-0
r- O rtJ
U- S- t-
76
-------
TABLE 15. PARSHALL FLUME EVALUATION
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects ,
Effect of Solids Movement
Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precal i brati on
Ease of Calibration
Maintenance of Calibration
Adaptability
Cost
Portability
Scale
D Poor
D Poor
D High
59 No
D High
D High
D High
D High
D Poor
D High
D High
D High
D Poor
D No
O High
D High
D No
D Poor
D No
n NO
D Poor
D Poor
D Poor
n High
D No
D Fair 53 Good
53 Fair Q Good
D Moderate 51 Slight
D Yes
59 Moderate Q Low
D Moderate 59, Slight
D Moderate 59 Slight
D Medium 58 Low
S) Fair D Good
D Medium 69 Low
59 Moderate D Slight
59 Moderate DSliciht
D Fai r 59 Good
53 Yes
D Medi urn 53 Low
59 Moderate Q Slight
D Yes
D Fair 53 Good
53 Yes
69 Yes
D Fair 59 Good
D Fai r 59 Good
D Fair D Good
S3 Medi urn D Low
59 Yes
77
-------
upon existing conduit slope and a channel contraction (provided by the
flume) to produce supercritical flow. Ludwig and Ludwig (33) and Wells
and Gotaas (34) have discussed various design aspects of such flumes.
Such flumes arose out of a desire to have a measurement device that
could be inserted into an existing conduit with minimal site require-
ments other than sufficient slope. A number of different cross-section
shapes have been used over the years. Typical shapes for round and
rectangular conduits are depicted in Figure 20. A proprietary flume,
the Leopold-Lagco, which was introduced in 1965, is a Palmer-Bowlus
type flume with a rectangular cross-section and is designed for use
with circular pipes.
In the detailed laboratory studies conducted by Wells and Gotaas (34),
they found that accuracies within ±3% of the theoretical rating curve
could be obtained at depths as great as 90% of the pipe diameter. No
effect of downstream depth on calibration was found for submergence
ratios less than 0.85. Various geometric effects were investigated, and
it was found that a minimum throat length of at least 60 percent of -the
pipe diameter was required, that the base height and exit transitions
had no effect on the calibration, that a variation of entrance transi-
tion slope from 1:3 to 1:2 had a negligible effect, and that the point
of upstream depth measurement should be no more than half of the pipe
diameter upstream from the entrance to the flume.
In some designs, e.g., Figure 20c, the bottom slab or base is omitted
entirely. It is more often included, however, both to help distrxbute
the overall channel contraction and to provide structural integrity, an
important feature for portable devices especially.
The chief advantage of Palmer-Bowlus flumes over Parshall flumes is
their ease of installation in existing conduits. They may also offer
somewhat lower head loss. They share all of the benefits listed in the
discussion of Parshall flumes. In ordinary designs operating under low
flow conditions, the bottom slab acts as a broad-crested weir, whose
characteristics were discussed earlier. A disadvantage of Palmer-Bowlus
flumes is that they have a smaller range, with 20:1 being seldom ex-
ceeded. Standard Palmer-Bowlus flumes are available to fit pipe sizes
from 15.2 cm (6 in.) to 2.4m (8 ft). Palmer-Bowlus flumes are evaluated
in Table 16.
As stated'by Palmer and Bowlus (27), "The. Important facto* ^Ln the. con-
&&w.c£Lon and ^Ln&taUation o& any &om o$ ve.ntu^L devx.ce *J> tlnat a con-
Atniction 06 &om the.y meet the.
•ipecac pfiobtm at hand Jin a practical manned." Diskin (35) has in-
troduced an unconventional sort of a Palmer-Bowlus flume, Figure 21.
He achieved channel contraction by wedging a pier-shaped element in
78
-------
END VIEW
(a)
LONGITUDINAL MID SECTIONS
VERTICAL HORIZONTAL
c
(b) J
0
c
Cc)
-fILf—*~-~-f:-tftI_
(d)
'•
rf
•A. \»\A A^
Figure 20. Various Cross-Section Shapes
of Palmer-Bowlus Flumes
79
-------
TABLE 16. PALMER-BOWLUS FLUME EVALUATION
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precal i brati on
Ease of Calibration
Maintenance of Calibration
Adaptability
Cost
Portabi 1 ity
Scale
D Poor
Q Poor
D High
Si No
D High
D High
n High
DHigh
D Poor
D High
D High
D High
D Poor
D No
D High
D High
D No
D Poor
D No
D No
D Poor
D Poor
D Poor
D High
D No
Si Fair
SI Fair
n Moderate
SI Moderate
D Moderate
D Moderate
D Medium
D Fair
D Medium
O Moderate
D Moderate
D Fair
D Medium
SI Moderate
D Fair
D Fair
D Fair
D Fair
D Medi urn
D Good
D Good
18 Slight
D Yes
n LOW
8 Slight
SI Slight
SI Low
SI Good
SI Low
SI Slight
SI Slight
SI Good
SI Yes
SI Low
D Slight
D Yes
SI Good
SI Yes
SI Yes
SI Good
S) Good
D Good
SI Low
SJ Yes
80
-------
WATER SURFACE
VERTICAL CROSS-SECTION
7
r OPENING
/ (ABOVE)
END VIEW
-WEDGE
(ABOVE) ^PRECAST ELEMENT
MEASURING POINT
TOP VIEW
Figure 21. Diskin Measuring Device
81
-------
the pipe between the crown and the invert. Experimental observations
confirmed the theoretical rating curve determined under the same as-
sumptions as for a standard Palmer-Bowlus flume. Limiting submergence
was found to be between 0.75 and 0.85.
The chief drawback to such a metering device is that it poses a severe
obstruction to the flow and, if applied to trashy or debris-laden flows,
it almost surely invites, in time, either its own destruction or block-
age of the conduit. As a portable device, however, it can be installed
quickly and may have some use. The Diskin device is evaluated in
Table 17.
Cutthroat Flume - The cutthroat flume was developed for use in flat
gradient channels where a flume which could operate satisfactorily
under both free (critical) flow and submerged flow conditions might be
desired. It operates as either a Type I or Type II flume. The advan-
tages of a flume with a level floor are that it is easy to construct
and can be placed inside an existing channel without requiring excava-
tion, simply by placing it on the channel bed. Studies reported by
Skogerboe, et al (30) showed that flow depths measured in the exit sec-
tion of the flume resulted in more accurate submerged flow calibration
curves than calibrations employing flow depths measured in the throat
section. Since the upstream depth measurement is made near the en-.
trance, there is no need for a throat section in such a flume; in fact,
removing the throat section was found to improve flow conditions in the
exit section. Skogerboe, et al (36), who performed the development work
on these flumes, have given the name "Cutthroat" to any such flume that
has no throat section (i.e., zero throat length). A rectangular cut-
throat flume is illustrated in Figure 22.
One of the benefits of a cutthroat flume is economy, since fabrication
is facilitated by the flat bottom and removal of the throat section.
Another fabrication advantage is that every flume size has the same wall
lengths, which allows the same forms or patterns to be used for every
flume size. Rectangular cutthroat flume sizes of 0.3, 0.6, 0.9, 1.2,
and 1.8m (1, 2, 3, 4, and 6 ft) have been studied extensively by
Skogerboe, et al (36). Transition submergences were found to vary
smoothly from 79% to 88% over this range. Above these values, the flow
is subcritical (submerged) and the submerged flow calibration curves
must be used.
Similar cutthroat flumes of a trapezoidal shape with sides sloping out-
ward at 45 degrees were also investigated by Skogerboe, et al (36) in
small sizes, i.e., throat widths of 0, 15, and 30 cm (0, 6, and 12 in.).
Development of intermediate and larger sizes was not attempted because
of the variety of possible geometries that could be used. Cutthroat
flumes are evaluated in Table 18.
82
-------
TABLE 17. DISKIN DEVICE EVALUATION
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
.Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
- Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precal ibration
Ease of Calibration
Maintenance of Calibration
Adaptability
Cost
Portabi 1 i ty
Scale
D Poor
D Poor
D High
8 No
D High
D High
E High
DHigh
D Poor
D High
D High
D High
D Poor
& No
K High
Si High
D No
D Poor;
D No
D No
D Poor
D Poor
D Poor
13 High
D No
K Fair DGood
58 Fair Q Good
D Moderate S) Slight
D Yes
53 Moderate Q Low
$3 Moderate D Slight
D Moderate D Slight
D Medium 53 Low
D Fai r SI Good
D Medium SI Low
D Moderate 58 Slight
D Moderate S! Slight
D Fair SI Good
D Yes
D Medium D Low
D Moderate Q Slight
D Yes
S3 Fair Q Good
& Yes
85 Yes
81 Fair Q Good
E3 Fair D'Good
D Fair D Good
D Medium S3 Low
» Yes
83
-------
6.081
STILLING WELL
STILLING WELL
FOR H.
CM
+
SUBMERGED
FLOW
TRANSITION
FREE FLOW
ELEVATION
Figure 22. Rectangular Cutthroat Flume
84
-------
TABLE 18. CUTTHROAT FLUME EVALUATION
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
- Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
orL imitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precal ibration
Ease of Calibration
Maintenance of Calibration
Adaptability
Cost
Portabi 1 ity
Scale
D Poor
D Poor
D-High
& No
D High
D High
D High
DHigh
KJ Poor
D High
D High
D High
D Poor
D No
D High
D High
D No ,
D Poor
D No
D N.o
D Poor
D Poor
D Poor
D High
Si No
D Fair
53 Fair
D Moderate
D Moderate
D Moderate
D Moderate
D Med i urn
D Fair
D Medium
D Moderate
D Moderate
D Fair
D Medi urn
SI Moderate
D Fair
D Fair
D Fair
D Fair
CD Medi urn
S3 Good
D Good
Kl Slight
D Yes
S3 Low
K Slight
Kl Slight
S3 Low
D Good
^ Low
S Slight
K Slight
S) Good
8 Yes
81 Low
D Slight
D Yes
£3 Good
S Yes
SI Yes
SI Good
SI Good
D Good
SI Low
D Yes
85
-------
Other Flumes - Several other flume designs have been used to solve spe<-
ciflc problems. These flumes may: (a) be easier to construct for cer-
tain types of sites; (b) pass sediment-laden flows more readily;
(c) handle a wider range of flows under certain conditions; (d) have
increased sensitivity in a particular flow range; etc. As a general
rule, they have not been as extensively investigated as the Parshall
or Patoer-Bowlus flumes, and less is known about their behavior over
a wide range of conditions.
San Dimas Flumes - As an example, the San Dimas flume was developed to
measure debris-laden flows in the San Dimas Experimental forest in 1938.
It is a modified Type IV flume in that it uses lateral contraction plus
a 3% slope in its floor to create a supercritical flow. In the entry,
the floor rises quickly to the crest, after which it falls as indicated
in Figure 23a. Because head measurements are made in supercritical
flow in the throat and critical depth occurs upstream, the discharge
ratings should be independent of upstream and downstream distubances.
Variation in approach conditions also should have little effect on the
ratings. Because of its rectangular cross-section, the San Dimas flume
is not sensitive or accurate at low flows. Results of tests on modified
San Dimas flumes were reported by Bermel (37), who reduced the degree of
contraction of the flume relative to the natural channel, provided a
less abrupt entrance, and measured the head at the midpoint of the flume
regardless of length. The modified San Dimas flume is depicted in Fig-
ure 23b. San Dimas flumes are evaluated in Table 19.
Trapezoidal Flumes - In attempts to obtain wider ranges of discharge
than those that can be obtained with Parshall or San Dimas flumes, sev-
eral investigators have considered supercritical trapezoidal flumes.
These generally operate as Type IV flumes. The outward sloping of the
flume walls provides increased sensitivity to lower discharge rates for
a given size and, hence, increased range. The possible elements of a
trapezoidal flume are indicated in the isometric sketch in Figure 24.
All of these elements need not be included in a particular design, how-
ever. In the trapezoidal cutthroat flume discussed earlier, for exam-
ple, the throat section is absent. Other designs eliminate the
diverging and exit sections where channel erosion is not a problem, and
so on.
Serious investigations of trapezoidal flumes began to be reported in
increasing numbers in the late 1950s. Geometric variations are so nu-
merous that no attempt will be made here to describe them all. Robinson
(38) has extensively investigated a trapezoidal flume with a flat floor
throughout the flume that conforms to the general slope of the channel.
Other designs, such as the one reported by Gwinn (39), have^the floor
sloping slightly towards the center to form a.very shallow "V".
86
-------
R=W
FLOOR ON
3% SLOPE
\STILLING WELL
INTAKE: HOLE OR SLOT
ZERO DATUM'
SIDE VIEW
FREE FALL
a. Original San Dimas Flume
PLAN
STILLING WELL INTAKE:
HOLE OR SLOT
FLOOR ON
3% SLOPE
SIDE VIEW
ZERO DATUM
b. Modified San Dimas Flume
Figure 23. San Dimas Flumes
87
-------
TABLE 19. SAN DIMAS FLUME EVALUATION
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
*
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operati on
Submergence or Backwater
Effects
Effect of Solids Movement
Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precal ibration
Ease of Calibration
Maintenance of Calibration
Adaptabi 1 i ty
Cost
Portability
Scale
D Poor
D Poor
D High
63 No
D High
D High
D High
D High
D Poor
D High
D High
D High
D Poor
D No
D High
D High
D No
D Poor
D No
D No
D Poor
D Poor
D Poor
D High
63 No
D Fair 63 Good
63 Fair D Good
D Moderate 63 Slight
D Yes
D Moderate 63 Low
D Moderate 63 Sli'ght
D Moderate 63 Slight
D Medium 63 Low
53 Fair D Good
D Medium 63 Low
D Moderate 63 Slight
D Moderate 63 Slight
D Fair 63 Good
53 Yes
D Medium 63 Low
63 Moderate Q Slight
D Yes
D Fair 63 Good
63 Yes
63 Yes
D Fair 63 Good
D Fair 53 Good
D Fair D Good
D Medium 63 Low
D Yes
88
-------
89
-------
Sizes and maximum discharge capacities for trapezoidal flumes vary
widely. Some are capable of measuring flows under 28 £/s (1 cfs),
while one of the largest known to the writers (located near Tombstone,
Arizona) has a throat width of 36.6m (120 ft) and is rated to a maximum
discharge of 736,000 £/s (26,000 cfs).
When the throat width is reduced to zero, such flumes are more properly
termed triangular flumes. Distinct advantages of a triangular flume
are its ability to measure accurately over a wide range of flows and
its high tolerance for submergence. Some designs can tolerate sub-
mergences as high as 90%, as opposed to the 60% noted earlier for the
Parshall flume. Trapezoidal flumes will lie between these two values
depending on their individual geometries. Trapezoidal flumes, including
triangular, are evaluated in Table 20.
Type HS, H. and HL Flumes - The U.S. Department of Agriculture (USDA)
Soil Conservation Service has HS, H, and HL type flumes in use in many
small watersheds. These USDA (40) flumes are illustrated in Figures 25
and 26. It is pointed out that all dimensions are proportional to the
total depth (height) of a given flume. These flumes have the advantage
of simple construction and reasonably good accuracy over a wide range
of flows. A variety of sizes are available to measure flows ranging
from 0.006 l/s (0.0002 cfs) to 3,400 £/s (120 cfs).
These flumes differ from the flume types discussed earlier because they
are, in fact, more weir than flume. They are more properly termed open
channel flow nozzles but are included here because of historical prece-
dent. Their design attempts to combine the sensitivity and accuracy of
the sharp-crested weir and the self-cleaning features of the flume. The
result is a compromise in both. The flat, unobstructed bottom allows
the passing of silt better than a weir. Like the weir, flow control is
achieved by discharging through a sharp-edged opening. However, the
flow is contracted gently from the sides only, much like the converging
section of ordinary flumes. The plane of the exit tilts backward toward
the incoming flow. Like weirs, these flumes should be used in free out-
fall situations, and the minimum head loss will be the measured head.
Head is measured upstream in subcritical but accelerating flow, and
critical flow occurs over the crest as with an ordinary weir.
These devices are capable of measuring quite wide ranges of flow in some
instances. For example, Soil Conservation Service rating tables for
H flumes indicate possible ranges of 175:1 for a 0.15m (0.5 ft) flume
and 5633:1 for a 1.38m (4.5 ft) flume. Type HS, H, and HL flumes are
evaluated as a group in Table 21.
Open Flow Nozzles
As mentioned in the discussion of Type HS, H, and HL flumes, the open
(channel) flow nozzle is a combination of flume and sharp-crested weir.
90
-------
TABLE 20. TRAPEZOIDAL FLUME EVALUATION
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Evaluation Parameter
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
- Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects •
Submersion Proof
Ruggedness
Self Contained
Precal ibration
Ease of Calibration
Maintenance of Calibration
Adaptabi 1 i ty
Cost.
Portabil ity
Scale
D Poor D Fair 81 Good
D Poor SI Fair D Good
D High O Moderate Kl Slight
53 No D Yes
D High D Moderate 63 Low
D High D Moderate H Slight
Q High D Moderate SI Slight
DHigh D Medium SI Low
D Poor 8) Fair D Good
SO High D Medium SI Low
DHigh D Moderate 63 Slight
D High D Moderate E§ Slight
D Poor D Fair S3 Good
D No SI Yes
DHigh D Medium S3 Low
DHigh 53 Moderate D SI i ght
D No ' D Yes
D Poor D Fair 53 Good
D No SI Yes
D No .-..-. SI Yes
D Poor D Fair SI Good
D Poor D Fair SI Good
D Poor D Fair Q Good
DHigh D Medium SI Low
SI No D Yes
91
-------
a
in
o
a
t—i
in
LU
_J
LU
(N
60
•H
92
-------
HS FLUME
H FLUME
HL FLUME
Figure 26. Isometric View of Type HS, H, and HL Flumes
93
-------
TABLE 21. TYPE HS, H, AND HL FLUME EVALUATION
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained .
Precal ibration
Ease of Calibration
Maintenance of Calibration
Adaptabi 1 i ty
Cost
Portabi 1 i ty
Scale
D Poor D Fair & Good
n Poor 63 Fair D Good
D High D Moderate 81 Slight
8 No D Yes
63 High D Moderate D Low
QHigh 63 Moderate D SI ight
D High D Moderate H Slight
63 High D Medium D Low
D Poor D Fair 53 Good
D High D Medium 63 Low
DHigh 63 Moderate D Slight
D High B Moderate D Slight
D Poor D Fair 63 Good
D No 63 Yes
D High 53 Medium D Low
D High 63 Moderate D Slight
D No D Yes
D Poor D Fair 63 Good
D No 63 Yes
D No 63 Yes
D Poor DFair 63 Good
D Poor 63 Fair D Good
D Poor D Fair D Good
DHigh D Medium 63 Low
D No 53 Yes
-------
Unlike the conventional weir, it can handle suspended solids rather ef-
fectively, as a self-scouring action exists, and relatively large solids
will pass without clogging. Use of open flow nozzles for heavy sludge
however, is not recommended unless calibration is for such use. Any de-
position will alter the contour of the nozzle and, hence, its flow
characteristics. For this reason the top of the nozzle is open in most
designs to allow for ready inspection and cleaning.
Conversely, the open flow nozzle does not have the good head recovery
characteristics of the flume. The loss of head through the device will
be at least one pipe diameter. Open flow nozzles are designed to be
attached to the end of a conduit flowing partially full and must dis-
charge to a free fall.
As with all head-area meters, the design is such that a predetermined
relationship exists between the depth of the liquid within the nozzle
and the rate of flow. In one design (the Kennison nozzle), the cross-
section is shaped so that this relationship is linear. In another de-
sign (the parabolic nozzle), the relationship is a parabola so that each
unit increase in flow produces a smaller incremental increase in head.
ine discharge profiles of these two nozzles .are depicted in Figure 27.
Open flow nozzles are factory calibrated and offer reasonable accuracy
(often better than ±5% of the reading) even under rather severe field
conditions. Standard sizes are available from 15 to 91 cm (6 to 36 in )
in diameter, with maximum capacities up to 850 Us (30 cfs). These de-
vices are capable of ranges of 20:1 or better and, for a given site,
will exceed the range of either a Parshall flume or a sharp-crested
weir. Parabolic nozzle lengths are roughly four times the diameter,
.while Kennison nozzle lengths are twice the diameter. Open flow noz-
zoles require a length of straight pipe immediately upstream of the
nozzle, and the slope of the approach pipe must not exceed certain lim-
its^ (depending upon nozzle size and profile) or else the calibration
will be in error. Open flow nozzles are evaluated in Table 22.
The open flow nozzles discussed above were characterized by a cross-
sectional profile shaped to give a better depth-discharge relationship
than the ordinary circular pipe cross-section. The latter can be used
for^indicating flow, but high accuracies are not normally achieved,
±10% or worse being typical. The method, developed by Vanleer (41), is
commonly referred to as the California pipe method, and uses as the pri-
mary device a straight, level (zero slope) section of pipe at least six
diameters in length (see Figure 28a). The pipe, which cannot be flowing
full, must be located so that there is free fall for the liquid at its
exit, i.e., it must discharge freely into air. Also the velocity of ap-
proach must be at a minimum. The measurement taken is the distance from
the crown of the pipe to the free water surface at the exit. An
empirically-developed rating formula (or set of tables) is used, knowing
95
-------
a. Linear (Kennison) Nozzle Profile (Q « H)
b. Parabolic Nozzle Profile (Q « H )
Figure 27. Open Flow Nozzle Discharge Profiles
96
-------
TABLE 22. OPEN FLOW NOZZLE EVALUATION
Evaluation Parameter
1
2
3
4
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
- Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precalibration
Ease of Calibration
Maintenance of Calibration
Adaptability
Cost
Portability
D Poor
D Poor
D High
81 No
D High
D High
8! High
D Ppor
D High
D High
D High
D Poor
D No
D High
D High
O No
D Poor
D N.o
D No
D Poor
D Poor
D Poor
D High
D No
Good
D Good
D Moderate 81 Slight
D Yes
High D Moderate Q L
OW
8! Moderate D Slight
D Moderate 81 Slight
D Medium D Low
D Fair 81 Good
D Medium 81 Low
81 Moderate D Slight
81 Moderate D Slight
D Fair gj Good
81 Yes
81 Medium D Low
81 Moderate D Slight
D Fair
D Fair
81 Fair
D Fair
D Medium
81 Good
53 Yes
B3 Yes
81 Good
D Good
D Good
81 Low
Yes
97
-------
ZERO SLOPE
1_
t ;
•6d OR GREATER
a. CALIFORNIA PIPE METHOD
MID-DEPTH
TO CENTER OF
STREAM
b. TRAJECTORY METHODS
Figure 28. California Pipe and Trajectory Methods
98
-------
diameter
the foula Wp K- ' The exPerl^ntal data used to develop
in if T7 laje obtained on steel pipes from 7.6 to 25.4 cm (3 to
10 in.) in diameter, but tables can be found extending up to 0 9m f3 ft)
consequently, will not be separately evaluated. nozzles a*d,
Trajectory Methods
The California pipe method, although discussed under open flow nozzles
may also be considered as a trajectory method. Trajectory methods a"te'
*"***• ?* T"* ^ fit in ^ ^scusSon at this
°f techni
-------
this seemingly simple procedure is that the velocity Profile of a £1 ow
is dependent upon many factors, and frequently a series of velocxty
measurements will be necessary in order to arrive at the average veloc-
?ty ^ss a section. The following quotation from the USDI Bureau of
Reclamation (10) is given to illustrate some of the vagaries and methods
for toplementation! "The. {at****, method* OJUL u*e.d to dete^ne, me.an
velocities Jin. a. vertical tine, with a. current mete*,'.
(1 } Two-point method.
(2) Stx.-tewtfa-de.pth method.
(3) Vertical ve£oOsity-c.ustve, method.
(4) Subsurface. method.
(5) Integration method.
(6) Two- tenth* method.
(7) Thre.e,-point method.
(B) Ones-point continuous method.
The. Mo-point method consist* of, metsurind the. velocity at 0 ^ ^ th in
ato B of, the. de.pth £rom the. wateJi 4u/Lrfac.e, and uA^n9 the. ave/uzae o^ the,
too mL^Sen*6. The. accuracy obtainable. uUktiU* ytfcod "^™i
j$i Sf JLA^aLauUd. The, method thouM not be, aAerf Mheu th*. depth
Jti> JieA& than 2 fcet..
The. ^-tenths-depth method con^tA o$
the, depth turn the. wte* AutfacA, *nd 4*
wheJte. the. two-point method ii> not appJUaabJie..
&ati& factory
od
The, method
The.
method c.on*O>t* o
of, 0.5 £oot 01 mou and
mean, a* tindina the. mean vatoe
but i& time, con&iming and c.o&tty.
The. AutouMfux. method invotoe* meMuMng the. velocity nem the. uateti
l^aee and then muttiplyina it by a. <»&<^ "**%*.
0.95, de.pendina on the. depth o£ wtex., the, veto c*ty, ,and
£L AtoSm o* canal bed. The. WtifWot ^^^d
e.Uicie.nt Unutt> the, uAe method.
The. integration method it> pui&med by obAWbte
l^caltine. by Atnoly and unitoxmty to^e^n and
tiwughout the. lanse, o£ wtui depth Mo or
not accuMte. and should be aied only fax. compasuAon* on.
rough
100
-------
and- om-point co^nuou* method*
For conduits flowing full and under pressure, the velocity profile will
wall J±£r ^ ^T^ nUmber> the cross- Bectlonal^Lpe, LTSe
wall roughness, among other factors. As in the case for open channel
flow some prior knowledge of the flow characteristics is necesslry in
order to use a single velocity reading to compute discharge.
comments in the following
Floats
Saced £°S me?°d °f determininS flow velocity, one or more floats are
t*™f A ™ J^V and the±r t±me to travel a measured distance is de-
termined The simple use of surface f loats , floats immersed less than
f,the.fiow ^epth, is the least desirable of all as they Sy
W- SCtS ln addition to cu"ent effects. Since the
Tol* 8Jrter than,the meaU velocity> a correction must be
For reasonably smooth flows in regular conduits, the correction
°'7 " °'9 deendi w depth,
aped
applied.
worf fairlvwna?eS,re f °ranges» whlch float »BtIy submerged and
work fairly well in the shallow flows found in many sewers. Somewhat
more sophisticated are the rod floats, which consist of a square or
thaf it°wiSSft I ^°°den); '^ r°d ±S deSlgned W±th a wei^ted end so
that it will float in a vertical position with the length of the im-
mersed portion approximately 0.9 times the depth of the flow. The rea-
soning here is that the velocity of a rod float which extends from
A further improvement in accuracy is known as the integrating float
method, which is discussed by Lin (43). Here, buoyant spherL are
101
-------
released from the channel floor and are displaced downstream as they
rise to the surface. The time from the moment of release to the moment
of surfacing is measured as is the distance traveled downstream. The
proper selection of size and specific gravity of the spheres for a par-
ticular flow depth minimizes the error caused by initial ascent accel-
eration and permits a flow measurement method that automatically
compensates for velocity distributions in a channel. The method is
best suited for fairly low velocities.
These methods should only be used for making rough estimates and are
not well suited for many storm or combined sewer applications, espe-
cially the integrating floats. They are evaluated in Table 23.
Tracers
In an attempt to improve upon the accuracy of float velocity methods,
many investigators turned to the use of liquid tracers to measure veloc-
ity. Dye, salt, and radioactive tracer substances have been used. In
principle, a slug of tracer is instantaneously introduced into the flow
at an upstream station, and the time of travel to a downstream station
a known distance away is measured. The technique should not be confused
with dilution techniques which will be discussed later.
When dyes are used, the technique is sometimes referred to as the color-
velocity method. Potassium permanganate, fluorescein, uranine, sodium
dichromate, and rhodamine dyes have been commonly used. In application,
the downstream time should be noted when the center of the mass of col-
ored liquid passes. Considerable judgment is required to determine the
center of mass of the dye pattern and, consequently, the accuracy of .
timing is limited. In actuality, the peak concentration is often used.
In high velocity flows, air entrained near the surface and spray above
the surface can further degrade the measurement. Also, it may be un-
certain whether the observed dyecloud velocity is the mean velocity of
the stream or just the velocity of the surface. Careful use of a fluo-
rometer can help eliminate part of the uncertainties, but high accura-
cies should not be expected as a rule.
A more precise method uses salt as the tracer and is oftenDeferred to
as the Allen salt velocity method. It is based on the fact that salt
in solution increases the electrical conductivity of water. In appli-
cation, a quantity of salt solution is forced into the stream under
pressure through quick-closing valves. In determining the average ve-
locity of the salt solution, two pairs of electrodes are installed in
the stream a known distance apart. The electrodes are energized by an
electrical current, and the resistivity of the water path is measured.
The greater conductivity of the salt solution will appear as a decrease
in resistance and, hence, an increase in current flow. If the elec-
trodes are connected to a control recording galvanometer, the graph ot
102
-------
TABLE 23. FLOAT VELOCITY .EVALUATION •
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flov
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
- Flow Obstruction
Head Loss
Manhole Operation
Power Requi rements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Sel f Contained
Precal ibration
Ease of Calibration
Maintenance of Calibration
Adaptability
Cost
Portabi 1 i ty
Scale
D Poor
53 Poor
K) High
& No
D High
D High
D High
DHigh
D Poor
D High
D Hi gh
D High
D Poor
M No
D High
S High
D No
D Poor
S! No
D No
D Poor
D Poor
D Poor
D High
D No
D Fair S3 Good
D Fair rj Good ;
D Moderate D SI ight
D Yes
D Moderate §3 LOW
D Moderate SD SI ight
D Moderate US Slight
n Medium M Low
D Fai r Kl Good
D Medium 81 Low
D Moderate E3-..S1 ight
D Moderate K Slight
D Fair ^ Good .
D Yes
D Medi um K Low
D Moderate n Slight
D Yes
D Fair 63 Good
D Yes
D Yes
. D Fair D Good
D Fair Q Good
D Fair Q Good
D Medi um 8 Low
^ Yes •
103
-------
current strength will have two humps that indicate the passing of the
salt slug past each pair of electrodes. The distance on the chart be-
tween these two humps (or peaks) is a measure of the time of travel,
and from this and the electrode spacing the flow velocity can be ob-
tained. Salt-velocity methods are more amenable to automation than
color-velocity methods. However, this requires rather special equip-
ment not familiar to average personnel, and its use is relatively ex-
pensive. With care, accuracies of better than ±2% can be achieved.
This method is sometimes used to calibrate other flow measurement de-
vices in place.
Radioisotopes can also be used as velocity tracers much as in the salt-
velocity method. The sensors here are scintillation counters or geiger
counters, but the application is essentially as described above. The
requirements for Federal licensing, expensive equipment, and highly ^
trained personnel together with the reluctance on the part of the public
to accept deliberate introduction of radioactive substances into their
water tend to limit the application of this technique. Tracer velocity
methods as a group are evaluated in Table 24.
Vortex
There are two major sub-types of vortex meters, the difference being in
whether vortex rotation or vortex generation is measured.
Vortex-Velocity - The'vortex-velocity meter has been discussed by Henke
(44) and McVeigh (45). It is designed to be used in pipes flowing full
and under pressure. Essentially the meter is a conduit having a bulge
on one side. Flow through the conduit results in a vortex pool in the
enlarged section of the conduit. A vortex cage located in the pool
counts its revolutions, which are related to the flow velocity. These
meters can be quite accurate (to ±0.5% of the reading) in certain flows
and have a usual rangeability of around 10:1. They are sensitive and
have very low pressure loss. However, solids in the flow and potential
fouling problems make the device appear generally unsuitable for sewage
applications. Vortex-velocity meters, are evaluated in Table 25.
Closely related to the operating principle of the vortex-velocity meter
is a rotorless current meter developed in Russia. As described by
" Replogle (8): "The. mvten. c.on&Ute o& a. tu.be. u)ht.o.h &ha.pe.d wto a.
Sole! siac.i-tMuLk-thape.d ovoJL tilth *» pa^JieJL tength*. In one. at
*£. Ifetfefct ling***, 'wwJUto* pajuMft to ***.<%* ^
the. tu.be? A baJUL uho&e. de.n*Uy U e^uaJL to that o^the, gagzd
Jin the. tubi. The. mete*, to Placed In the. **MO*U> that the.
t the. *to& cvbcM* Mi $*. ******** oj> th<> <***%*•
In thl tube. ^ &vt-*n motion by the. xu^aou* ^o/tee tumwuttzd
the. &lot&, and the. baU move* astound the. cto&juL oval at a
i the. *tx.e.am veJtoc^y. Advantage* crooned {ox. the. meteA
-------
TABLE 24... TRACER VELOCITY;,EVALUATION
— —
Evaluation Parameter
1 Range
2
3
4
5
6
7
8
9
10
1 1
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flou
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
- Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
o r L i m i t a t i o n s
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precalibration
Ease of Calibration
Maintenance of Calibration
Adaptabi 1 i ty
Cost
Portability
— j — — : __
1 Scale ]
D Poor K Fair DGood
D Poor S) Fair Q Good
D High 8 Moderate D Slight
' DNo; : 81 Yes"
D High D Moderate gj LOW
D High: D Moderate 8 Slight
j * ' «
Q High D Moderate 8 Slight
DHigh D Medium & Low
D Poor D Fair 8 Good
D High 81 Medium Q Low
DHigh D Moderate 8! Sliqht
d
D High ... Q Moderate 53 Sliciht
D Poor ' & Fair Q Good
D No |g yes
D High K Medium Q Low
DHigh D Moderate ^ Slight
D No D Yes
D Poor & Fair Q Good
£1 No Q Yes
K No D Yes
D Poor D Fair Kl Good
D Poor D Fair 81 Good
D Poor D Fair D Good
81 High D Medium Q Low
D No gj Yes
105
-------
TABLE 25. VORTEX-VELOCITY METER.EVALUATION
Evaluation Parameter
Scale
1 Range
2 Accuracy
3 Flow Effects on Accuracy
4 Gravity & Pressurized Flow
Operati on
Submergence or Backwater
Effects
6 Effect of Solids Movement
7 -Flow Obstruction
8 Head Loss
9 Manhole Operation
10 Power Requirements
11 Site Requirements
12 Installation Restrictions
or Limitations
13 Simplicity and Reliability
14 Unattended Operation
15 Maintenance Requirements
16 Adverse Ambient Effects
17 Submersion Proof
18 Ruggedness
19 Self Contained
20 Precalibration
21 Ease of Calibration
22 Maintenance of Calibration
23 Adaptability
24 Cost
25 Portability
SI Poor DFair DGood
n Poor 63 Fair D Good
QHigh D Moderate H Slight
IS No D Yes
D High D Moderate 69 Low
53 High
63 High
DHigh
53 Poor
D High
63 High
53 High
D Poor
D No
53 H i g h
D High
D No
63 Poor
D No
D No
D Poor
D Poor
D Poor
S3 High
63 No
D Moderate D Slight
D Moderate D Slight
O Medium 53 Low
D Fair D Good
D Med-ium 63 Low
D Moderate D Slight
D Moderate D Slight
53 Fair D Good
SI Yes
D Medium D Low
D Moderate 63 Slight
D Yes
D Fair D Good
SI Yes
SI Fai r
53 Fai r
D Fair
D Medi urn
D Good
D Good
D Good
D Low
D Yes
106
-------
threshold values are around 0.03 to 0.06 m/s (0 1 to n
Turbine Meters
The turbine meter, discussed by Artz (47) and Yard as « «
Rotating-Element Meters
=
f
o o
.
107
-------
TABLE 26. EDDY-SHEDDING METER EVALUATION
Evaluation Parameter J
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
• Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precal ibration
Ease of Calibration
Maintenance of Calibration
Adaptability
Cost
Portabil i ty
D Poor
fj Poor
D High
D No
D High
D High
D Hi9h
DHigh
D Poor
D High
D High
D High
D Poor
D No
D High
D High
D No
D Poor
D No
D No
D Poor
D Poor
D Poor
D High
D No
Scale
S3 Fai r
SI Fair
D Moderate
D Moderate
SI Moderate
C3 Moderate
D Medi urn
D Fair
D Medium
D Moderate
D Moderate
SI Fair
SI Medi urn
fj Moderate
SI Fair
D Fair
SI Fair
D Fair
SI Medium
D Good
D Good
SI Slight
SI Yes
SI Low
D Slight
D Slight
SI Low
SI Good
SI Low
SI Slight
SI Slight
D Good
SI Yes
D Low
SI Slight
D Yes
D Good
SI Yes,
K Yes
53 Good
D Good
D Good
D Low
SI Yes
108
-------
TABLE 27. TURBINE METER EVALUATION
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operati on
Submergence or Backwater
Effects
Effect of Solids Movement
- Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precal ibration
Ease of' Call brat ion
Maintenance of Calibration
Adaptabi 1 i ty
Cost
Portability
Scale
& Poor
D Poor
D High
& No
D High
81 High
B High
D High
£3 Poor
D High
•H High
D High
D Poor
D No
8 High
D High
D No
D Poor
D No
D No
D Poor
D Poor
D Poor
Bl High
S3 No
DFair DGood
H Fair Q Good
D Moderate 03 Slight
D Yes
D Moderate gj Low
D Moderate D Slight
D Moderate D Slight
HI Medium D Low
D Fair D Good
D Medium . 63 Low
D Moderate D Slight
SI Moderate D Slight
81 Fair Q Good
8) Yes
D Medium Q Low
D Moderate {g| Slight
D Yes
8) Fai r Q Good
8] Yes
B Yes
D Fair BJ Good
8! Fai r D Good
D Fair D Good
D Medium D Low
D Yes
109
-------
Both, have proper applications with both advantages and disadvantages.
Horizontal-axis meters have found wide use in pipe lines, water mains,
and high-flow applications that require a low permanent pressure drop.
They can handle higher flow rates than volumetric (positive displace-
ment) flowmeters, but not as high as turbine meters. Along with
vertical-axis meters, they are also used to measure open channel flows.
A thorough treatment of the use of current meters for open channel flow
measurement is given by Buchanan and Somers (49) and the USD! Bureau of
Reclamation (10).
Vertical-Axis Meters - The most common vertical-axis meters are those
with either the S-shaped (or Savonius) rotor or with a bucket wheel
made up of a number of conical or hemispherical cups. In general, the
bearing systems in the vertical-axis meters are simpler in design, more
rugged, better protected from silty water, and consequently, easier to
maintain than those of horizontal-axis meters. Bearing adjustment is
usually less sensitive, and their calibration at lower velocities
(where frictional effects are higher) is more stable. Vertical-axis
meters operate in lower velocities than horizontal-axis meters, gener-
ally having lower threshold velocities of around 0.03 meters per second
(0.1 fps) or less. Finally, a single cup rotor serves for the entire
range of velocities, and the rotor is repairable in the field without
adversely affecting the rating.
The type AA Price current meter is probably the most common type of
vertical-axis meter. This device has a rotor 12.7 cm (5 in.) in diam-
eter and 5 cm (2 in.) high with six cone-shaped cups mounted on a stain-
less steel shaft. It also has a vane to keep the rotor headed into the
flow, an electrical device to signal the number of revolutions, and pro-
visions for handling the meter. An assembly drawing of a Price type AA
current meter is given in Figure 29. There is also a Price type BTA
current meter which differs from the type AA only in its mounting yoke,
contact chamber, and the absence of the tailpiece. For smaller flows
there is a pygmy meter that is similar to the Price meter but only about
two-fifths its size. The rotational speed of the pygmy rotor is more
than twice that of the Price meters, and consequently its use is limited
to velocities up to 0*9 or 1.2 m/s (3 or 4 fps).
Horizontal-axis meters - This class of current meter is less sensitive
to vertical velocity components than is the vertical-axis meter, which
will over-register in most such instances. Vertical-axis meters cannot
correct for oblique flow, whereas some of the helical rotors of
horizontal-axis meters are designed to act as nearly perfect cosine
meters. The horizontal-axis rotor disturbs the flow less because of
its axial symmetry with flow direction. They also present a clearer
view to the flow than vertical-axis meters and, consequently, are
slightly less susceptible to fouling. Bearing friction, especially at
higher velocities, is less than for vertical-axis meters because bending
110
-------
ca
=3
n:
UJ LU 1— H-I
UJ UJ => CC
3C = Z «I
33 UJ
• I • .1 'CO CO
I- 1- Z
f- -Ul Ul i-l
< CJ O
et:
O
1— I— Ul »-i UJ
o o o a. or
«S
co a o:
a. o. a.
o
rs
co
i— r— r— i— CMCNJ
a:
Cu
LL.
O
I-
to
a:
LU
CO
CO
S
O CO
d_ O
o.
CO
Z CD
d I-l
z a
i-« z •
CO I-l
CO
CJ I—
< o
I— f
Z 1— CH CO
o z CD I— 1—
«c
or
CJ
•a:
o
4-1
4-1
g
!-l
S-
-------
moments on the shaft are eliminated. Finally, although the horizontal-
axis meter has a higher velocity threshold of around 0.08 m/s (0.25 fps) ,
it, is capable of measuring higher flow velocities, with some designs
capable of measuring in excess of 9 m/s (30 fps).
The types of horizontal-axis meters in common use today are the Ott,
Neyrpic (Dumas), Haskell, and Hoff. The Ott meter was developed in
Germany, the Neyrpic meter in France, and the Haskell and Hoff in the
United States. All are precision instruments that can cover a wide
range of flow velocities by using propellers with a variety of screw
pitches.
Townsend and Blust (50) give a comparison of stream velocity meters, and
the reader who is further interested is referred to their discussion.
No rotating-element current meter is ideal for any extended period of
unattended operation, but they can be used to give excellent results in
the hands of a skilled operator. Generally they are inexpensive, simple
in design, and rugged in construction. A major shortcoming of all
rotating-element current meters is that their accuracy is so closely
coupled with the operator. In general, it requires much experience and
great care to select gaging sites and apply techniques in such a way as
to obtain results that approach the basic accuracy of the instrument
itself (often ±1%). Typically, it is difficult to achieve better than
±2 or 3% accuracy in the field. Carter and Anderson (51) and Smoot and
Novak (52) discuss accuracy of current meter measurements further.
Their obstruction to the flow and susceptibility to fouling limit their
use in storm and combined sewers. Rotating-element velocity meters are
evaluated in Table 28.
Other Devices
Other devices are available to measure the velocity of open channel flow
at a point within the stream. They include pitot tube, electromagnetxc,
venturi, thermal, optical» and other fundamental principles. They are
discussed in the subsections of this report that address their particu-
lar principles of operation, and will not be covered again here. In
this use (as current meters) they all require attended operation.
Otherwise they function as described in their individual discussions.
FORCE-DISPLACEMENT
This class of flowmeters is related to the variable area class discussed
earlier in that both operate by a force due to the flow displacing an
obstruction (primary element) that is immersed in the fluid. In effect,
the drag of the obstruction is being measured, and this is related to
the square of the fluid velocity, among other parameters which include
the drag coefficient. Being proportional to the velocity squared means
that force-displacement meters will tend to be insensitive at very low
112
-------
TABLE 28. ROTATING-ELEMENT METER EVALUATION
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Evaluation Parameter
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
- Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Li mi tat ions
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precal i brat ion
Ease of Calibration
Maintenance of Calibration
Adaptability
Cost
Portability
Scale
D Poor B Fair D'Good
D Poor SI Fair Q Good
DHigh D Moderate K) Slight
D No 53 VP<;
lUl 'ICO
D High D Moderate ® Low
S3 High Q Moderate D Slight
QHigh S3 Moderate D Slight
D Hi.gh D Medium gj Low
D Poor SI Fai r D Good
DHigh D Medium SI Low
D High D Moderate SI Slight
D High D Moderate 53 Slight
D Poor D Fair SI Good
K No D Yes
81 High . D Medium D Low
SI High D Moderate D Slight
0 No D Yes
D Poor DFair H Good
SI No n Yes
D No SI Yes
D Poor D Fair SI Good
D Poor D Fair SJ Good
D Poor D Fair Q Good
DHigh D Medium SI Low
D No SI Yes
113
-------
velocities. The dependency on drag coefficient means that calibration
will shift if the primary element becomes fouled by buildup or debris.
The secondary device measures the displacement of the primary element
and converts this into velocity or actual discharge.
Vane Meters
The vane meter is simply a vane hinged along either a vertical or hori-
zontal axis and placed in the flow (Figure 30). The flowing fluid pro-
duces an angular displacement which is related to velocity and read by
the secondary element.
The vertical-axis vane meter is one of the most common. As indicated in
Figure 30a, the vane may be quite short as compared with the flow depth
or, for flows whose levels do not change greatly, the vane may extend
over almost the entire flow depth in an attempt to average the velocity.
The advantages of the vertical axis arrangement are that the counter-
balancing weight can be easily changed to alter flow ranges; it can be
made to integrate velocities over a great portion of the vertical; and
its mechanical output can be recorded and indicated visually. Its dis-
advantages include its tendency to collect debris; the high degree of
bearing friction (resulting from its typically heavy weight) that adds
to the low flow insensitivity problem of this class; and the fact that
removal for service or repair is difficult.
The horizontal-axis vane meter (see Figure 30b) overcomes many of the
disadvantages of the vertical-axis type. Among its advantages are the
ease of changing the weight at the bottom in order to change ranges;
its capability for being installed totally submerged to avoid fouling
by floating debris; its light weight and simplified design to reduce
bearing friction; and the fact that its output is usually electrical.
On the other hand, despite its relatively small size and weight, it may
not be convenient for some installations, and there is no visual readout
of deflection. Both types of vane meters will be affected by wind on
the exposed portion of the vane.
Robinson (53) has described a somewhat different form of the horizontal-
axis vane meter that is sometimes referred to as the pendvane meter. It
is designed for use in open channel flow, usually for small channels
less than 0.9m (3 ft) deep and 1.8m (6 ft) wide. In the pendvane meter,
the vane is shaped to match a particular channel cross-section so that
its displacement is the same for a particular discharge rate irrespec-
tive of the velocity profile (within certain specified depth limits).
Thus the pendvane meter indicates discharge rate directly. Errors of
±10% are possible, and flow range is low.
Two percent might be considered an accuracy limit for vane meters and
accuracies of ±5% or more should be considered more typical. For a
114
-------
ROTATION AXIS DOTATION AXIS
VANE
CHANNEL BOTTOM-
HE:
1 — *-* v — i
u
ROTATION
AXIS
JL
WATER SURFACE
VANE
(a) Vertical Axis Meters
Figure 30. Vane Meters
(b) Horizontal Axis
Meter
115
-------
given weight (i.e., range setting), 5:1 or so should be considered a
typical flow range that these devices can handle. Vane meters are
evaluated in Table 29.
Hydrometric Pendulum
The hydrometric pendulum is sometimes used in open channels as a current
meter. In its most elemental form, it consists of a ball (heavier than
the fluid) suspended by a string (or light cable). The angular deflec-
tion of the ball and string is proportional to the flow velocity in the
vicinity of the ball. Accuracies are poor because stream fluctuations
make determination of the deflection angle difficult. These are partly
due to the vortex shedding phenomenon discussed earlier. Also, there is
usually no method for recording the output, and the device must be man-
ually operated. Accuracy is further degraded by the complex and some-
what uncertain corrections for drag on the line that are required.
Drag on the line is increased greatly by floating debris, such as moss
or grass, catching on it. Good features are that the drag element can
be very easily changed to alter the ranges, and the line can easily be
lengthened or shortened to measure velocity at various depths. The hy-
drometric pendulum is evaluated in Table 30.
Target Meter
The target meter, discussed by Stapler (54), is a more sophisticated
force-displacement device for measuring flows. The primary element
(or target) is shaped similarly to the sharp-edged annular orifice. It
mounts on a support that passes through the conduit wall via a sealed,
flexible closure, and the displacement of the primary device is meas-
ured by a strain gage or some other suitable displacement measuring
secondary device (Figure 31). This meter has relatively high accura-
cies,, approaching those of the orifice meter under certain conditions.
Strictly speaking, although the target meter is a point velocity meas-
uring device, the point may be rather large so that an integrating ef-
fect is achieved. Replogle (55) reports that analytical and experimental
studies have indicated that target meters can be designed for open chan-
nels of any cross-sectional shape and can indicate discharge rate di-
rectly to better than ±3%, independent of flow depth. Such meters are
limited in discharge measurement primarily by the ability to predict
the general type of velocity profile existing in the flow. Typical
ranges are around 5:1. They do not appear especially suitable for use
in flows containing suspended material such as sewage. Target meters
are evaluated in Table 31.
Other
Brief mention will be made here of a few other force-displacement type
flowmeters. They do not appear well suited for storm or combined sewer
flow measurement at this time, but are included since special adapta-
tions may be possible in some situations.
116
-------
TABLE 29. VANE DEFLECTION METER EVALUATION
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
-Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precal ibration
Ease of Cal ibration
Maintenance of Calibration
Adaptabi li ty
Cost
Portability
Scale
53 Poor
Q Poor
D High
SI No
D High
D High
& High
DHigh
D Poor
D High
D-High
D High
Q Poor
D No
D High
D High
D No
D Poor
D No
D No
D Poor
D Poor
D Poor
D High
Si No
D Fair DGood
SI Fair Q Good
D Moderate Si Slight
D Yes
D Moderate SI Lov/
SI Moderate D Slight
D Moderate D Slight
D Medi um S) Low
SI Fai r D Good
D Medi um SI Low
D Moderate SI Slight
Si Moderate D Slight
D Fair SI Good
S3 Yes
Si Medium Q Low
SI Moderate Q Slight
D Yes
D Fair SI Good
SI Yes
SI Yes
SI Fair Q Good
SI .Fair D Good
D Fair D Good
D Medium SI Low
D Yes
117
-------
TABLE 30. HYDROMETRIC PENDULUM EVALUATION
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precal ibration
Ease of Calibration
Maintenance of Calibration
Adaptabi 1 i ty
Cost
Portability
Scale
53 Poor
53 Poor
D High
53 No
D High
D High
D Hi9h
DHigh
D Poor
D High
D High
D High
D Poor
53 No
D High
53 High
D No
O Poor
63 No
D No
D Poor
D Poor
D Poor
D High
D No
D Fai r
D Fair
D Moderate
D Moderate
69 Moderate
53 Moderate
D Medi urn
D Fair
D Medium
D Moderate
D Moderate
D Fair
D Medium
n Moderate
D Fair
69 Fai r
$3 Fair
D Fair
D Medi urn
D Good
D Good
59 Slight
D Yes
63 Low
D Slight
D Slight
69 Low
53 Good
59 Low
59 Slight
59 Slight
59 Good
D Yes
53 Low
D Slight
D Yes
59 Good
D Yes
53 Yes
D Good
D Good
D Good
63 Low
53 Yes
118
-------
FLEXIBLE
CLOSURE
FLOW
STRAIN GAGE
(FORCE TRANSDUCER)
LEVER ARM
CONDUIT
DISC
Figure 31. Target Meter
119
-------
TABLE 31. TARGET METER EVALUATION
Evaluation Parameter
Scale
1 Range
2 Accuracy
3 Flow Effects on Accuracy
4 Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
6 Effect of Solids Movement
7 -Flow Obstruction
8 Head Loss
9 Manhole Operation
10 Power Requirements
11 Site Requirements
12 Installation Restrictions
or Limitations
13 Simplicity and Reliability
14 Unattended Operation
15 Maintenance Requirements
16 Adverse Ambient Effects
17 Submersion Proof
18 Ruggedness
19 Self Contained ,
20 Precalibration
21 Ease of Calibration
22 Maintenance of Calibration
23 Adaptability
24 Cost
25 Portability
53 Poor D Fair D Good
n Poor 81 Fair D Good
QHigh D Moderate 53 Slight
53 NO D Yes
O High D Moderate EJLow
D High
E3 High
D High
SI Poor
D High
D High
D High
D Poor
D No
81 High
D High
D No
69 Poor
D No
D No
D Poor
D Poor
D Poor
81 High
£9 No
8! Moderate Lp Slight
D Moderate D Slight
81 Medium D Low
D Fair D Good
8! Medium D Low
D Moderate 81 Slight
63 Moderate D Slight
81 Fair Q Good
SI Yes
D Medium D Low
Q Moderate SI Slight
D Yes
Q Fair D Good
81 Yes
H Yes
D Fair SI Good
SI Fair D Good
D Fair D Good
D Medium D Low
D Yes
120
-------
The jet deflection meter is a development reported by Stanney (56) in
which a fluid jet is directed across the flow stream towards two impact
tubes on the opposite side. The flow stream displaces the jet an amount
proportional to the flow rate, thereby creating a differential pressure
between the two impact tubes that is a linear function of the flow ve-
locity of the measured fluid. Like many so-called fluidic devices for
measuring flow, it is primarily suitable for gas flows. It has been
used for clean water flow velocities from 0.03 to 0.3 m/s (0.1 to
1 fps). Accuracies of ±1% have been obtained over flow ranges of 5:1.
The device does not appear at all suitable for dirty liquids and,
consequently, will not be discussed further.
The ball and tube flowmeter consists of a tube (usually transparent)
bent through 180 degrees into some shape of an arc, semicircular being
the original design. The tube is placed in a vertical plane concave
upward, and a ball (primary element) of density greater than the liquid
and diameter smaller than the tube is placed inside. The flow creates
drag forces on the ball, and it rises in the tube until they are bal-
anced by the gravity forces; thus, the position of the ball along the
tube is admeasure of the flow rate. The device should not be confused
with the rbtameter which uses a taper so that the area varies as the
float is displaced. Of course, ball and tube flowmeters are only suit-
able for pressurized flow. They are not obtainable commercially (to
the writers' knowledge), but can be easily fabricated in the laboratory.
Accuracies of around ±2-5% can be achieved over flow ranges'of up to
5il. When maximum design flow rates have been appreciably exceeded, the
ball will be lost unless provision is made for capturing it at some
point.
Another interesting force-displacement type of flowmeter utilizes a var-
iable weight principle. It consists of a vertical section of pipe (us-
ually transparent) containing a float of density slightly less than that
of the fluid to be measured. A chain is fastened to the bottom of the
float. The device operates under pressurized flow conditions with flow
in the upward direction. As the flow rate increases, the float rises
and in so doing picks up a larger portion of the chain, thus effectively
varying its weight. The height of the float in the tube is a measure
of the flow rate. This device is also not commercially available to the
writers' knowledge.
FORCE - MOMENTUM
Force-momentum flowmeters measure the mass flow rate of the fluid as
opposed to its volumetric flow rate. Several instruments for which the
measured variable is directly related to mass flow will be discussed
below. Those that add mechanical energy to the system, such as the
transverse momentum devices, generally require a constant speed drive
and rotating seals.
121
-------
Axial Flow Mass Meter
The axial flow mass meter uses a turbine driven at constant speed to
induce a constant angular velocity to the fluid and a complementary
spring-retained rotor to measure the force required to overcome the an-
gular momentum. The angular displacement of the retained rotor is di-
rectly related to the mass flow of the fluid. The axial-flow,
transverse-momentum device is the most common of this type and is^avail-
able in several configurations. They can be quite accurate (±0.5% of
reading) over ranges, typically, of 10:1. They clearly are suited only
for pressurized flows and clean fluids.
Radial Mass Meter
This device, often referred to as a Coriolis mass flowmeter, has a pri-
mary element resembling a centrifugal pump. The-fluid is accelerated •
radially, and the torque required to accomplish this is proportional to
the mass flow of the fluid. These devices have been discussed by
Halsell (57). They produce a pressure rise, rather than drop, and have
been successfully used with liquids, foams, and slurries. Accuracies
of ±1% over of 10:1 range have been achieved.
Gyroscopic Mass Meter
This meter consists of a circular pipe loop, the fluid flowing through
it constituting a gyroscope. If a gyroscope is rotated about a perpen-
dicular axis, a torque is created due to precession effects. Like the
other mass flowmeters, a constant-speed motor and rotating seals are
required (in one design the gyro is vibrated rather than rotated, and
flexible couplings replace the rotating seals). The meter is an unob-
structed pipe so it is suitable for handling troublesome liquids and
flows high in solids. Pressure losses are low, but external power is
required and the meter is quite expensive. Its range and accuracy are
similar to the other mass meters.
Magnus Effect Mass Meters
The Magnus effect, discussed by Schlitchting (46) and others, is the
phenomenon that produces a differential force on a body spinning in a
flow field. (It allows golfers to slice and baseball pitchers to throw
curves, for example.) The force is proportional to the fluid velocity
and density and to the surface speed of the rotating body among other
factors. In the Magnus-effect mass meter, a rotating cylinder is im-
mersed with its axis at right angles to the flowing stream. Since the
cross-section of the conduit and the surface speed of the cylinder are
constant, the mass flow is a direct function of the "lift" on the cyl-
inder, which is measured with suitable transducers. Again, the meter
requires a constant speed drive and rotating seals. The spinning cyl-
inder poses a rather severe flow obstruction, and the device is not
suitable for dirty flows.
122
-------
Force-momentum meters as a group are evaluated in Table 32.
THERMAL
Thermal flowmeters were originally developed for the measurement of gas
flows but have also found application in liquid flows in recent times.
In view of the extremely rapid response times that are achievable with
some designs, they have been especially useful in the study of turbu-
lent boundary layer structures and the like. Fundamentally, they all
work on the principle that heat transferred between a body and a flow-
ing stream is related to the rate of flow.
Hot Tip Meters
When an electrically heated (bead, wire, film, etc.) is placed in a
flowing fluid, heat will be transferred from the element to the fluid
at a rate that'is a function of: (a) the velocity of the flow; (b) the
temperature, density, viscosity, and thermal conductivity of the fluid;
and (c) the temperature, geometry, and properties of the element. If
all but one of the fluid^flow and element variables are kept constant,
the heated element is a transducer for measuring the remaining variable.
A few typical hot-tip element configurations are depicted in Figure 32.
Two methods are used in flow measurement. The first technique employs
a constant current passing through the sensing element. Variation in
flow results in changed element temperature; hence, changed resistance,
which thereby becomes a measure of flow. The major drawback of the
constant current system is that the frequency response of a sensor de-
pends not only on sensor characteristics, but also on flow characteris-
tics. The response depends on both the thermal capacity of the sensor
and the heat transfer coefficient between the sensor and its environ-
ment. Since the sensor response varies with changes in flow (changing
the heat transfer coefficient), the frequency compensation of the am-
plifier must be readjusted whenever the mean flow changes.
The constant temperature type of compensating circuitry overcomes the
primary disadvantage just mentioned in the constant current system by
using a feedback loop. As the velocity past the sensor increases, the
sensor will tend to cool with a resulting decrease in the resistance.
This resistance decrease will cause the voltage to decrease, thus chang-
ing the input to the amplifier. The phase of the amplifier is such that
this decrease in voltage will cause an increase in the output of the
amplifier in order to increase the current through the sensor. The
output of the constant temperature system is the voltage output of the
amplifier, which in turn is the voltage required to drive the necessary
current through the sensor.
123
-------
TABLE 32. FORCE-MOMENTUM METER EVALUATION
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precal ibration
Ease of Calibration
Mai-ntenance of Calibration
Adaptabi 1 i ty
Cost
Portabi 1 ity
Scale
53 Poor
Q Poor
D High
S! No
D High
D High
D High
D High
13 Poor
& High
K) High
53 High
53 Poor
D No
53 High
D High
D No
53 Poor
D No
D No
D Poor
D Poor
D Poor
58 High
E3 No
D Fair
O Fair
D Moderate
D Moderate
53 Moderate
53 Moderate
D Medi urn
D Fair
D Medium
D Moderate
D Moderate
D Fair
D Medi urn
n Moderate
D Fair
D Fair
D Fair
D Fair
D Medi urn
D Good
81 Good
SI Slight
D Yes
,?
53 Low
D Slight
D Slight
53 Low
D Good
D Low
D Slight
D Slight
D Good
53 Yes
D Low
53 Slight
D Yes
D Good
53 Yes
53 Yes
53 Good
53'Good
D Good
D Low
D Yes
124
-------
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125
-------
Ling (58) introduced the hot-film probe for use in liquid flows in 1955.
Since then, a number of investigations have been carried out in liquids
with only a few being successful. In most of these, the film was placed
away from the wall since its size can interfere with the detailed meas-
urements required in the sub-layer region. Indeed, different configura-
tions of film probes have produced very different results within the
same experiment even for the simple case of measuring velocity profiles
in turbulent flows. The one type of film probe that holds promise of
being applied to sewer flow is the flush-mounted probe, because the
backing material does not interfere with the flow field and has the best
chances of physical survival in the sewer environment. Very little re-
search has been done to determine the feasibility of using flush-
mounted, hot-film sensors for quantitative measurements in water because
the electrolysis problem has only recently been solved through the use
of quartz coatings. Runstadler, et al (59) give a very concise summary
of the factors that significantly affect the stable non-drift operation
of hot-film probes in water. Hot-tip probes are evaluated in Table 33.
Cold-tip Meters
Harris (60) has described a sort of inverse of the hot-tip meters. The
operating principle of his device involves the use of a thermoelectric
cooling unit to provide a cold surface in contact with the stream flow.
The temperature of the cold surface is then, of course, a function of
stream velocity and the other factors noted in the discussion of hot-
tip devices. This approach would offer advantages when applied to a
fluid containing dissolved gases which tend to come out of solution when
heated by a hot-tip type element. The temperature difference between
the probe and the fluid must be even smaller than with the hot-tip de-
vices, however, because most storm and combined sewer flows are closer
to their freezing temperatures than their boiling points. The ice for-
mations will affect calibration. Although interesting, it is not felt
that cold-tip devices are ready, as yet, for application as sewage flow
measuring devices. Most of the evaluation comments of Table 33 hold for
cold-tip devices also.
Boundary Layer Meter
Laub (61, 62) and Barlow (63) describe a boundary layer meter wherein
the heater and temperature measuring elements are on the outside of the
conduit. With this design, only the layer of fluid immediately adja-
cent to the inner wall of the conduit is heated. Response times of
under a second are possible as is temperature compensation. There is
no obstruction to the flow in such a design, so the meter introduces
no additional head loss. Errors can result from changes in fluid com-
position which would change the parameters affecting thermal devices
(e.g., viscosity, specific heat, thermal conductivity, etc.). The de-
vice would appear to overcome many of the other objectionable features
of the hot-tip designs, however. Good ranges (50:1) and accuracies
(±1%) are achievable under ideal circumstances, but should not be ex-
pected in a sewage measurement application.
126
-------
TABLE 33. HOT-TIP METER EVALUATION
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
1,8
19
20
21
22
23
24
25
Range
•-Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
-Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precal i brati on
Ease of Calibration
Maintenance of Calibration
Adaptabi 1 i ty
Cost
Portability
Scale .
D Poor
S3 Poor
D High
D-No
D High
S High
D High
D High
D Poor
D High
D High
D High
D Poor
D No
SI.High
D High
D No
D Poor
D No
D No
D Poor
D Poor
D Poor
S) High
SI No
^ Fair D Good -
D Fair D Good
D Moderate SI SI ight
53 Yes
D Moderate E3 Low
$
D Moderate D Slight
SI Moderate Q Slight
D Medi urn S3 Low
Si Fair D Good
S) Medium D Low
SI Moderate D Slight
IE Moderate D Slight
SI Fair Q Good
SI Yes ,
D Medi urn D Low
SI Moderate Q SI ight
D Yes
SI Fair D Good
53 Yes
SI Yes
D Fai r SI Good
SI Fair D Good
D Fair D Good
D Medi urn Q Low
D Yes
127
-------
As in the case of thermal probes, it is possible to locate a number of
sensors along the vertical (here, around the periphery of the conduit
if. round) and thereby measure depth as well as velocity under open chan-
nel flow conditions. Such designs have recently become available, but
experience with them is limited as yet.
Eshleman and Blase (64) describe a related device which is more properly
termed a thermal time-of-flight flowmeter. It is actually a tracer
technique, but here the tracer is energy in the form of heat. A heater
element is used to introduce a slug o.f heat (a thermal wave) into the
boundary layer flow. Temperature compensated thermistors, located a
known distance downstream, were used to detect the heat pulse (extremely
complex electronics were required) and its time of flight was deter-
mined. This velocity could be related, through calibration, to mean
flow velocity, but accuracy and repeatibility were poor in the device
as designed. Thermal boundary layer meters are evaluated in Table 34.
ELECTROMAGNETIC
In 1839, Michael Faraday attempted to measure flow by lowering large
electrodes into the Thames River near the Waterloo bridge. This experi-
ment did not succeed. Faraday's Law states that if a conductor/'^(in this
case the flowing fluid) is passed through a magnetic field, a voltage
will be inducted across the conductor at right angles to both the lines
of flux and the direction of motion and will be proportional to the
velocity of the conductor and the strength of the magnetic field.
Today, there are a number of successful designs of electromagnetic flow-
meters, all based upon Faraday's Law. All share the same fundamental
components, but they differ in their design of implementation,,ranging
from meters for measuring pressurized flow in pipes to point velocity
sensors. Their earliest successful adaptations were in sea-water ap-
plications such as oceanographic current meters and logs for indicating
ships' speed. When applied to a pipe flowmeter, the fundamental com-
ponents are a piece of straight pipe, electrical coils to produce a
magnetic field perpendicular to the axis of the pipe, and a pair of
diametrically-opposed electrodes orthogonal to the magnetic field and
the pipe axis (Figure 33). For a velocity probe (Figure 34) the same
fundamental components are involved, but they are in a sort of "inside
out" arrangement as compared to the pipe meter. The theory of elec-
tromagnetic flow measurement is treated in the monograph by Shercliff
(65).
There are a number of parameters of the flowing stream that must be
considered in the application of electromagnetic flowmeters. These in-
clude: corrosion levels, abrasion levels, possible magnetic content,
presence of entrained gases, and the ability to coat electrodes. The
devices can tolerate low fluid conductivity, e.g., some work with dis-
tilled water, and design features can be incorporated to overcome most
problems posed by undesirable fluid characteristics.
128
-------
TABLE 34. THERMAL BOUNDARY LAYER METER EVALUATION
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
- Fl ow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precal ibration
Ease of Calibration
Maintenance of Calibration
Adaptabi 1 i ty
Cost
Portability
Scale
Q Poor
O Poor
D High
D No
D High
D High
D High
D H i g h
53. Poor
D High
D High
D High
D Poor
D No
' Q High
D High
D No
D Poor
D No
D No
D Poor
D Poor
D Poo r
53 Hi gh
& No
D Fair 8! Good
D Fair 53 Good
D Moderate 53 Slight
53 Yes
D Moderate §3 Low
D Moderate 53 Slight
D Moderate Kl Slight
D Medi urn 53 Low
D Fair D Good
53 Medi urn D Low
52 Moderate D Slight
53 Moderate D Slight
59 Fair Q Good
53 Yes
53 Medi urn D Low
D Moderate 53 Slight
D Yes
D Fair 53 Good
53 Yes
H Yes
D Fair 53 Good
D Fair 53 Good
D Fair Q Good
D Medi urn D Low
D Yes
129
-------
FLOW
ELECTRODE
ASSEMBLY
MAGNET COILS
Figure 33. Components of an Electromagnetic Pipe Flowmeter
130
-------
PROBE
MAGNETIC FIELD
ELECTRODES
FLOW
ELECTROMAGNET
Figure 34. Components of an Elec.tromagnetic
Velocity Probe
131
-------
An alternating polarity magnetic field (ordinarily or at near 60 Hz) is
usually generated to avoid thermoelectric effects, electro-chemical ef-
fects, and DC detection problems. A difficulty is that the alternating
magnetic field can cause a quadrature voltage (induced noise) problem
resulting in an offset in the zero point (thus indicating flow when
there is none). Quadrature is not constant, but can change due to elec-
trode fouling (5-10 percent output zero shifts are not uncommon when
electrode coating occurs). The problem is reduced by using self-
cleaning electrodes and superimposing a signal equal in amplitude but
180 degrees out of phase (null adjustment). One design uses a quadra-
ture rejection circuit to virtually eliminate zero shifts. Although
normally used only under full pipe flow conditions, an electromagnetic
pipe flowmeter will work if the pipe is less than full (e.g., down to
about half), but an additional measurement, the fluid depth, is required
to determine flow rate. It is also possible to mount a number of sen-
sors up the wall of the conduit to measure both velocity and depth.
Such an arrangement should be capable of measuring both open channel
and pressurized flows. Except in attended use as a current meter, the
probe configuration, because of its necessary obstruction to the flow,
is not as desirable for measuring storm or combined sewer flows.
These devices have only relatively minor disadvantages (fouling of
electrodes in some designs, susceptibility to the presence of stray
electrical and magnetic fields) except for their relatively high power
consumption, which makes battery operation for extended periods im-
practical. Electromagnetic flowmeters have a number of inherent ad-
vantages. They are capable of very high accuracies (better than ±1% of
full scale) over fairly wide ranges (20:1 or more in many standard de-
signs, and higher in configurations mentioned above) and can measure
flow in either direction. They introduce very little pressure loss,
have no moving parts, their response time is rapid (less than one sec-
ond), and output is linear. The devices are fairly expensive, however.
Electromagnetic flowmeters are evaluated in Table 35.
ACOUSTIC
The scientific use of acoustic principles in instrumentation today has
its roots in the SOund Navigation And Ranging (SONAR) equipment devel-
oped during the Second World War. The fundamental principles were
known, of-course, before that time, and the depth of wells has long
been measured by discharging a blank shell from a gun and using a stop-
watch to determine the echo return time. Because most equipment in
use today operates at frequencies above the audio range, the term ul-
trasonic is used by many writers when referring to this class of de-
vices. A very recent article by Liptak and Kaminski (66) provides a
comprehensive survey of the field.
Acoustic meters have two classes of application in flow measurement
today; as secondary devices to continuously monitor liquid level (or
stage) and as primary devices to measure actual flow velocity. Common
132
-------
TABLE 35. ELECTROMAGNETIC FLOWMETER EVALUATION
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
Flow Obstruct ion
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
o r L i m i t a t i o n s
S i m p 1 i c i ty and Re 1 i a b i 1 i ty
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
'Precal ibration
Ease of Cal ibrati on
Maintenance of Calibration
Adaptabi 1 i ty
Cost
Portability
Scale
D Poor
D Poor
D High
D No
D High
D High
D High
DHigh
£3 Poor
SI High
D High
D High
D Poor
D No
D High
D High
D No
D Poor
D No
D No
D Poor
D Poor
D Poor
m High
gl No
81 Fair D Good
D Fair S3 Good .
D Moderate £3 Slight
& Yes
D Moderate Eg Low
O Moderate K Slight
D Moderate S Slight
D Medi urn Eg Low
DFair D Good
D Med-i urn D Low
SI Moderate D Slight
S) Moderate D Slight
53 Fair D Good
S! Yes
ESI Medium Q Low
D Moderate K Slight
D Yes
Kl Fair D Good
SI Yes
83 Yes
D Fair HI Good
D Fair SI Good
D Fair D Good
D Medium D Low
D Yes
133
-------
to both is the measurement of the travel time of acoustic pulses between
a transmitter and receiver. The two applications will be discussed in
turn.
Continuous measurement of liquid depths is accomplished by measuring
the time required for an acoustic pulse to travel to the liquid-air in-
terface (where it is reflected) and return. The transmitter and re-
ceiver may be separate physical entities or may be combined. There are
two fundamental physical arrangements as depicted in Figure 35. One
uses air path measurement and the other uses liquid path measurement.
Although better short-term accuracy can be achieved with liquid path
arrangements, for wastewater applications the air path arrangement is
more common since it simplifies installation, is independent of fluid
velocity, and avoids any contact with the flow.
When flow (velocity) measurement is to be accomplished, it is not the
velocity of sound that is measured but, rather, the differential veloc-
ity between travel in the upstream and downstream directions. Since the
acoustic devices are actually velocity sensors, the area and vertical
velocity profile across the flow must be known. For open-channel flow,
the depth must also be determined and, understandably, manufacturers
generally use acoustic level sensors for this purpose. For widely vary-
ing flow depths, sensor placement is critical, and more than one pair
of sensors may be required.
As noted by Liptak and Kaminski (66), acoustic flow sensing or measuring
equipment (like sonar) falls into one of two rather broad categories,
passive and active. In passive operation, the transducer does not emit
any acoustic energy but simply acts as a receiver. Flow switches (on/
off state indicators) usually sense the noise generated by the flowing
stream and provide indication that some predetermined threshold value
has been exceeded. Passive flowmeters are either immersed in the flow-
ing stream or, as in the case of open-channel flow, can be located in
air. Fundamentally, they operate on the ide,a that, as the flow in the
conduit increases, the sound level also increases in some direct and
repeatable manner. Only two commercial firms offer such equipment, and
considerable work would be required before they could be reliably used
in a storm or combined sewer flow measurement application. This is dis-
cussed further in Section VIII.
There are a number of active acoustic flowmeter designs available today.
They all use at least one pair of transducer sets (transmitter/receiver),
so located that one operates against the direction of flow and the other
operates with the flow. A few physical arrangements are indicated in
Figure 36. Differences occur in the details of implementation; e.g.,
sensor geometry, sensors immersed in the flow or fastened to the outside
of the conduit, sensors projecting into the flow, flush mounted, or re-
cessed in wells, etc. There are also three fundamental approaches to
determining the velocity of the flow in present equipment designs -
differential time circuits, total travel time circuits, and "sing-
.around" circuits.
134
-------
Separate Transmitter
and Receiver
Combined Transmitter
and'Receiver
a. Air Path Measurement
b. Liquid Path Measurement
Figure 35. Physical Arrangements of:Acoustic Depth Sensors
135
-------
a. WETTED
TRANSDUCERS
SINGLE PAIR
^J^^
FLOW
XX / / /
DOUBLE PAIR
b. CLAMP-ON
TRANSDUCERS
XXXXX
FLOW
XXXXX
Figure 36. Physical Arrangements of Acoustic Velocity Sensors
136
-------
In the differential time circuit, the difference in the time of arrival
of acoustic pulses, which are triggered simultaneously at each end of a
diagonal path across the stream, is measured directly. When the two
transmitters send signals simultaneously toward each other, the flow
of water will increase the effective speed of one and decrease that of
the other. The signal transmitted in the downstream direction arrives
first, and is used to start a timer, which runs until the signal trans-
mitted in upstream direction arrives. This time increment is thus the
differential between the total travel times involved and is linearly
proportional to the fluid velocity. The average total travel time must
also be recorded to compensate for changes in the speed of sound of the
fluid. This technique is not well suited for small conduits with low
velocities because the time differences may be on the order of
nanoseconds.
In the total travel time circuit, the flow velocity is computed by re-
solving the velocity component in the flow direction as computed from
the sequential travel times required for pulses to travel; e.g., first
from the downstream sensor to the upstream sensor and then from the up-
stream sensor to the downstream sensor. Since the total travel times
are used, changes in the speed of sound in the fluid are automatically
compensated for. Errors in indicated velocity are a linear function of
timing errors in either direction.
The sing-around circuit technique is sometimes referred to as a pulse-
repetition frequency technique. In it, cumulative measurements of
travel times are made by using the received pulse at the far end of an
acoustic path to immediately trigger a second pulse from the originating
transmitter. Arrival of the second pulse triggers a third, and so on.
Either the total time required for completion of a fixed number of cy-
cles is measured or the cycling rate is reduced to a continuous, pulse-
repetition frequency. Where a single pair of transducers is employed,
measurements are made in one direction for a given period and then in
the other. Sometimes two pairs of transducers are used (tuned to dif-
ferent frequencies) and operated simultaneously. By using the differ-
ence in the upstream and downstream frequencies to determine the flow
velocity, the dependence upon the sound velocity of the fluid is
eliminated.
From the foregoing discussion it can be seen that one of the most im-
portant factors in any acoustic flow measuring device is the accurate
measurement of time (or its inverse, frequency). As noted by Smoot
(42), four different signal-recognition methods have been used in vari-
ous designs on the market today - the leading-edge detection method;
a method that utilizes the differential of the voltage time pulse train;
the zero-crossover method; and the phase difference method. There are
advantages and disadvantages to each, and competing claims have been
made by proponents of one method or another.
In summary, acoustic liquid velocity sensors have not yet reached the
state of the art where they can be considered as simple, off-the-shelf
137
-------
items for wastewater flow application. They offer many advantages, but
tend to be relatively expensive for some installations and require
highly trained technicians for their repair and maintenance. Accura-
cies to ±0.5% of full scale are achievable, but numbers as high as ±5%
must often be considered more typical, especially for a wastewater
application. Ranges from 20:1 to 1000:1 are possible, depending upon
design details discussed earlier. Acoustic meters are evaluated in
Table 36.
DILUTION
The dilution method can be used to measure discharge directly without
experiencing many of the difficulties of other devices. It can be used
in any shape of conduit flowing either partially full or under pressure
and does not involve the stream dimensions or measurement of fluid prop-
erties such as pressure, temperature, or even level. It produces no
pressure loss, requires no drop in hydraulic grade line, offers no ob-
struction to the flow, and indicates flow rate directly by simple theo-
retical formulas.
Basically, the measurement of discharge by dilution methods depends
upon determining the degree of dilution of an added tracer solution by
the flowing water. Spencer and Tudhope (67) have noted that dilution
methods have been known since at least 1863. Although the earliest
tracers were brine, radioactive and fluorescent dye tracers are more
commonly used today. They have greatly reduced the quantities of tracer
substance required and increased the accuracies achievable in many in-
stances. For example, the fluorescent dye Rhodamine WT can be quanti-
tatively detected with an accuracy of ±1% in concentrations of less
than 10 parts per billion.
There are two general techniques used in dilution flow measurement:
the constant-rate injection method and the total-recovery method (called
the slug-injection method by some writers). These are depicted in Fig-
ure 37. As its name implies, the constant-rate injection method re-
quires that the tracer solution be injected into the flow stream to be
measured at a constant flow rate for a given period of time. The dis-
charge is determined by the simple formula given in Figure 37a involv-
ing the background concentration in the stream (if any), the tracer
concentration and injection rate (both presumably controlled and known),
and the measured plateau of the concentration-time curve at the measure-
ment site. In the total-recovery method, a known quantity, of the tracer
solution is introduced into the stream in any one of a number of ways,
and a continuous sample is removed at a uniform rate for the entire
time needed for the tracer wave to pass, in effect integrating the con-
centration-time curve. This integral is sometimes approximated by using
a series of successive discrete samples. The discharge is simply re-
lated to the total quantity of tracer injected and the integral of the
concentration-time curve as indicated in Figure 37b. This latter method
requires that the total volume of the tracer be accounted for at the
measurement site.
138
-------
TABLE 36. ACOUSTIC METER EVALUATION
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
- Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precal ibration
Ease of Calibration
Maintenance of Calibration
Adaptability
Cost
Portability
Scale
D Poor
D Poor
D High
D No,
D High
D High
D High
D High
Q Poor
D High
D, Hi gh
D High
D Poor
D No
D High
D High
D No
D Poor
D No
D No
D Poor
D^Poor
D Poor
Kl High
& No
D Fai r 18 Good
D Fair .- g) Good
D Moderate 63 Slight
K Yes ,;
D Moderate gj Low
S! Moderate D Slight
D Moderate SI Slight
D Medi urn Si Low
81 Fair D Good .
SI Medium D Low
18 Moderate D Slight
SI Moderate Q Slight
SI Fair D Good
18 Yes
SI Medium Q Low
D Moderate gj Slight
D Yes
S3 Fair D Good
18 Yes
K Yes
D Fair S Good
D Fair SI Good
D Fair Q Good
D Medium Q Low
D Yes
139
-------
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Although each of these dilution methods has its advantages and limita-
tions, they are basically similar. A fluorometer, geiger counter, or
some other appropriate instrument is required for determining sample
concentration, a method of extracting a sample for analysis is needed,
and a device to either inject tracer at a steady known rate or withdraw
sample at a steady (but not necessarily known) rate is required. Both
methods require complete vertical and lateral mixing at the measurement
site. ..Since vertical mixing usually occurs rather rapidly as compared
to lateral mixing, the latter usually controls the distance required
for complete mixing, and hence, the distance between the injection and
measurement sites, Cobb and Bailey (68) provided a thorough discussion
of dye-dilution methods, in which they recommend calibration of the
measurement reach (the length between injection point and measurement
point) to ascertain the required mixing length and to determine rela-
tive tracer losses (due to adsorption by pipe walls or solids for
example).
The effect of inflow or outflow in the measurement reach will cause the
point of flow determination to shift for a dilution-type measurement.
Where there is no inflow or outflow in the measurement reach, the mea-
sured flow will be the flow occurring at any point in the reach. If
there is inflow within the measurement reach and it is totally mixed
with the stream at the measurement point, the flow measured will be that
at the measurement point, not the injection point. If there is outflow
from the measurement reach but after complete mixing of the tracer has
occurred, the.flow measured will be that at the injection point, not
the .measurement point.
Replogle, et al (69) report achieving accuracies of better than ±1% in
laboratory flume measurements using dye dilution techniques and
Kilpatrick (70), making dye-dilution discharge measurements on the
Laramie River under total ice cover, obtained agreement of better than
+2% (+0.6% in one case) as compared with current meter measurements.
Shuster (71) reports obtaining accuracies better than ±3% using radio-
isotopes as a tracer. He found that, in the concrete-lined trapezoidal
channel used in his study, the length required for almost complete mix-
ing was 250 to 300 times the flow depth. Ranges of 1000:1 or better
can be achieved. One popular use of the technique is to calibrate other
primary devices. The main disadvantages of dilution techniques are the
cost associated with the instrumentation required for determining tracer
concentrations, the lack of ruggedness in some of their designs, and the
required training for operator personnel. The dilution method is eval-
uated in Table 37.
OTHER
There are a number of less widely used flow measurements that do not
fit well under any of the more traditional classifications discussed
so far. They will be discussed here.
141
-------
TABLE 37. DILUTION METHOD EVALUATION
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
Effect o'f Solids Movement
Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precal ibration
Ease of Calibration
Maintenance of Calibration
Adaptability
Cost
Portability
Scale
D Poor
n Poor
D High
D No
D High
D High
D High
D High
D Poor
D High
D High
D High
D Poor
D No
D High
D High
D No
D Poor
81 No
81 No
D Poor
D Poor
D Poor
£) High
D No
D Fair
D Fair
SI Moderate
D Moderate
D Moderate
D Moderate
D Medi urn
D Fair
8! Medi urn
D Moderate
D Moderate
81 Fair
81 Medi urn
Q Moderate
8) Fair
D Fair
D Fair
D Fair
D Medi urn
81 Good
81 Good
D Slight
81 Yes
81 Low
81 Slight
BB s 1 1 g h t
SI Low
8! Good
D Low
8! Slight
83 S 1 i g h t
D Good
81 Yes
D Low
81 Slight
D Yes
D Good
D Yes
D Yes
81 Good
81 Good
D Good
D Low
81 Yes
142
-------
Doppler
A fairly recent technique for measuring the velocity of flow in a
liquid stream makes use of the doppler effect. Such devices, called
scatter frequency shift devices by some writers, may utilize any
one of a number of forms of radiated energy, including ultrasonic
wavelengths, infrared, ultraviolet, laser, etc. They operate on
the principle that when a beam of energy is projected into a non-
homogeneous liquid, it is scattered by suspended particulate matter
in the fluid, and some of it is reflected back to a receiver. Owing
to the doppler effect, the frequency of the return signal reflected
from the scatterers in the fluid differs from that of the trans-
mitted signal provided there is a net movement of the nonhomogeneities
with respect to the transmitter or receiver. This frequency shift
is directly related to the velocity of the scatterers (among other
factors) and, if they are stationary with respect to the liquid to
the flow velocity itself. The scatterers can range from solid parti-
cles to gas bubbles, the only requirement being that they move at
the same velocity as the flow transporting them.
It is pointed out that such devices usually sense velocity only in a
very small region (where the transmitter and receiver signals cross)
and, hence, knowledge about the velocity profile is normally necessary
in order to infer total flow quantities. For example, at acoustic
frequencies of 5-10 MHz, the reverberation volume is on the order
of 0.003m (0.01 ft) in diameter. This has been used to advantage
in laboratory studies of boundary layer development using laser-
doppler devices.
Acoustic-doppler devices have been investigated by the U.S. Geological
Survey over a period of several years. As noted by Smoot (42), their
experience has been less than totally successful. Under good con-
ditions, i.e., size and concentration of suspended particulate mat-
ter, the meter functions very well, but when concentrations are too
low (or particle sizes too small) or too high, there is either
sporadic or no signal return. A further limitation of such devices
is the need for temperature and composition compensation. Under
ideal conditions, Doppler meters can yield accuracies of ±0.5% over
ranges of 10:1 or higher. They are expensive, however, and little
SPP,C^±0nS data are availal>le. Doppler meters are evaluated in
Table 38.
Optical
The U.S. Geological Survey and the California Department of Water
Resources have developed a meter which uses optical methods to
determine surface velocities of streams; see Buchanan and Somers
(49) or Smoot (42). The meter is a stroboscopic device and essentially
143
-------
TABLE 38. DOPPLER METER EVALUATION
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operati on
Submergence or Backwater
Effects
Effect of Solids Movement
- Flow, Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precal ibration
Ease of Calibration
Maintenance of Calibratio
Adaptabi lity
Cost
Portabil ity
Scale
SI Poor DFair D Good
n Poor Q Fair S3 Goad
D High D Moderate Si Slight
D No 63 Yes
D High D Moderate H Low
ED High Q Moderate D SI ight
D High D Moderate 63 Slight
D High D Medium 63 Low
CD Poor S3 Fair D Good
D High S3 Medium D Low
DHigh E3 Moderate D SI ight
D High SI Moderate D Slight
D Poor SI Fair D Good
D No E9 Yes
D High SI Medium D Low
D High D Moderate SI Slight
D No D Yes
D Poor SI Fair D Good
D No 81 Yes
D No BYes
D Poor D Fair SI Good
D Poor D Fair SI Good
D Poor D Fair D Good
SI High D Medium D Low
SI No D Yes
144
-------
consists of a low-power telescope, a set of mirrors on the periphery
of a drum, a variable-speed motor that rotates the drum at precisely-
controlled speeds, and a tachometer for determining drum rotational
speed. Velocity measurements are made from an observation point
above the stream. Light coming from the water surface is reflected
by the mirrors into the lens system and eyepiece. By adjusting the
rotational speed of the drum, the apparent motion of the water sur-
face images reflected by the mirrors slows down and stops, appearing
as if the surface of the water was being viewed while moving along
exactly in pace with it. The velocity can be determined by knowing
this null speed of rotation and the vertical distance from the
water surface to the optical axis of the meter.
The meter is a light-weight, battery-powered unit that has no parts
in contact with the flowing stream. It can be used for quite high
velocity streams and for flows heavily laden with debris and sedi-
ment (it was developed for flood use). It is not useful for low-
velocity, tranquil flows, but has been used successfully to measure
velocities ranging from 1.5 to 15.2m/s (5 to 50 fps). The optical
meter is evaluated in Table 39.
Electrostatic
A Very recent development by Alger (72) is the electrostatic flow
meter. The concept arose from the observation that a stream of water
discharging from a pipe into air appeared to possess a surrounding
electrical field or charge. Experimental tests have been run using
water as the flowing medium. The voltage between two dissimilar
metal pipe sections (electrically insulated from each other) was
measured at different controlled rates of flow, most of which were
within the laminar range. •
It is well established that a potential difference exists between
two different metals immersed in a fluid containing ions of the metals.
This is observed in the experimental set-up just described when there
is no flow. Increasing the flow rate was found to produce an imme-
diate decrease, in the voltage. Decreasing the flow rate, however,
caused an increase in the voltage which required some time before
it would steady out. The voltage levels were also functions of
certain elements of the system geometry (e.g., length of insulation
between the two pipe sections), the type of metal pipe sections
(steel and copper were used), and perhaps of the nature of the fluid
(e.g., conductivity) as well. The method at present requires that
the pipe be flowing full and under pressure. It offers no obstruc-
tion to the flow, head loss, etc., and could be rather inexpensive
it it utilizes the natural elements of a fluid-pipe system. It is
presently the subject of continuing research and cannot be considered
as fully understood or suitable for practical use at this time. There-
fore, no further discussion will be given.
145
-------
TABLE 39. OPTICAL METER EVALUATION
Evaluation Parameter
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Range
Accuracy
Flow Effects on Accuracy
Gravity & Pressurized Flow
Operation
Submergence or Backwater
Effects
Effect of Solids Movement
Flow Obstruction
Head Loss
Manhole Operation
Power Requirements
Site Requirements
Installation Restrictions
or Limitations
Simplicity and Reliability
Unattended Operation
Maintenance Requirements
Adverse Ambient Effects
Submersion Proof
Ruggedness
Self Contained
Precal ibration
Ease of Calibration
Maintenance of Calibration
Adaptabi 1 i ty
Cost
Portabil i ty
Scale
D Poor 81 Fair DGood
SI Poor D Fair D Good
D High D Moderate 68 Slight
81 Mo D Yes
D High D Moderate 81 Low
D High D Moderate 53 Slight
QHigh D Moderate 8! Slight
DHigh D Medium S3 Low
D Poor 81 Fair D Good
D High D Medium 81 Low
DHigh D Moderate EJ Slight
D High D Moderate 53 Slight
D Poor D Fair 81 Good
81 No D Yes
D High D Medium 81 Low
8! High D Moderate D SI ight
D No D Yes
D Poor D Fair 81 Good
8! No DYes
D No B Yes
D Poor DFair 8) Good
D Poor D Fair 81 Good
D Poor D Fair D Good
D High D Medium 81 Low
D No 81 Yes
146
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Nuclear Resonance
Nuclear resonance flowmeters, as described by Replogle (8) exploit
a property of molecular nuclei. In nuclear resonance, the nucleus
is disturbed by precessional motions, which have a negligible effect
upon molecular or chemical reactions. Essentially, nuclear resonance
consists of observing the absorption of radio waves at a frequency
determined by the ratio of the nuclear magnetic moment to its spin
(called the gyromagrietic ratio) and the value of an applied magnetic
field. In water molecules, it is particularly easy to observe nuclear
resonance since hydrogen protons provide a very strong absorption
signal. Resonance is observed by using a receiver to detect the
rf energy lost from a transmitter. No resonance signal can then be
detected until the transmitter power is reduced and sufficient time
has e34psed so that the nuclei can relax to their normal distribution
This /relaxation time is a characteristic of the nuclei and their
environment and may be used to indicate the velocity of flowing
fluids. e
•f . •
,fn the /somewhat limited work that has been done, accuracies of ±0.5%
of full scale have been achieved over a 10:1 range under full pipe
flow^onditions. This technique does not appear suitable for storm
or combined sewer application at this time and, consequently, will
not be discussed further.
Mis
cellaneous
suf°^ed.thf the foregoing discussion has exhausted
of physical principles or design adaptations for
such r.,OWS', TherS are nUmer° US "ther^evices or Methods
such as: the Gibson (or water hammer) technique that requires the
screws wSch f ^^ " f^ ** '«""**«* **** ^ ^ersson
nn IM^ ^ require a reach of very regular channel and a track
on which the screen car can travel; Danaides devices, in which flow
discharJ ^ fcVhendei>th °f the 1±quid in a ^ntkner which is
that coSSt f°U? h/^ib^ted offices; fixed measuring palisades
creating H'^ airf?^-sha.Ped vanes extending across the flow and
creating a differential pressure that is related to discharge- the
° Palisades' in whi^ the flow is deSSned
the Palis^ ^ tilting from
of them
147
-------
SECONDARY DEVICES
A, review of all of the secondary devices used in flow measurement
is outside the scope of the present writing. There do exist however,
a number of devices that are called flowmeters by their manufacturers
but which, in actuality, are secondary devices for measuring stage
They must be used with some form of primary device before true flow
measurements can be made. A brief discussion of these devices wxll
be given along generic lines.
As is the case with all secondary devices, there are three basic types
of information that can be provided, either separately or in combx-
nation These are an indication of flow rate (typxcal units are cf s
gpn, mgd, etc.; such devices are sometimes referred to as indicators);
frunnfng total of flow to the observed moment (typxcal unxts are
=^?r r f
not del with these topics, but will focus upon the method used to
sense or measure water level or stage.
Float-in-Well This is probably the oldest type of secondary device
insistence It is applied in a stilling well connected to the gage
poinf of ?ne primary device (weir, flume, etc.). The f^-in-well
essentially consists of a float of some suitable shape (sxzed for
"mpatiblSty with the dimensions of the well) «^*«*c£"™*
to a wheel and counterbalanced in some fashion so that the cable
remains taut. As the float rises or falls with charges ^ water
levtl the cable rotates the wheel, which is connected exther mechan-
ically or electronically to the readout, recorder, or whatever.
Discharge is determined by the use of cams, electronic circuits.
etc., that are characterized for the primary device involved.
Float-in-Flow. In this type of secondary device, the float rides
on the actual surface of the flow, directly sensing its level rather
than Indirectly sensing it as with a stilling well. Float shapes
range ?rom spherical, to scow or ski shaped, the latter being desxgned
rSnimiL disturbances of the liquid surface fouling by trash or
debris, oscillations in the instrument, etc. The float xs Attached
to a hinged arm that is directly or indirectly (e.g., by cable) con-
nected to the main body of the instrument. Directly-connected designs
should be immersion proof if they are to be used in storm or combxned
148
-------
sewers with any history of surcharging. In indirectly-connected de-
signs, where the main body of the instrument can be located above the
high water level, it heed not necessarily be immersion proof, but this
feature never hurts.
Advantages of float-in-flow devices include: freedom from the require-
ment for a stilling well and purge system; direct (rather than indirect)
sensing of the liquid level; and avoidance (in some designs) of cables,
counterweights, etc., typical of float-in-well devices. Disadvantages
include: possible fouling by trash or-debris (which can result in er-
roneous readings or even physical damage); broad chart records in some
instances due to the lack of damping of water surface oscillations
that some stilling wells provide; and a more limited range due to the
restrictions on arm length necessary at some installations.
Bubbler. In this type secondary device, a pressure transducer senses
the back-pressure experienced by a gas which is bubbled at a constant
flow rate through a tube anchored at an appropriate point with respect
to the primary device. This back-pressure can be translated into water
depth and subsequently related to discharge. Advantages include a lack
of moving parts or mechanisms, a sort of self-cleaning action arising
from the gas flow, and virtually no obstruction to the flow. One of
its main disadvantages is that if the exit end base of the bubble tube
becomes appreciably reduced due to build-up of contaminants from the
flow, erroneous readings will result even though the instrument may
appear to be functioning normally. Aspiration effects due to the ve-
locity of the flow may also present problems.
1
Electrical. These secondary devices make use of some sort of change in
electric circuit characteristics in order to indicate the liquid level.
Most designs utilize a probe or some similar sensor which is immersed
in the flow at the gage point. This sensor is a part of an electrical
circuit, and its behavior in the circuit is a function of its degree of
immersion. For example, the sensor could basically be an admittance-
to-current transducer, providing a measure of depth based on the small
current flowing from the sensor to the grounded stream. Changes in any
electrical property (capacitance, resistance, etc.) can be used to
sense liquid depth. Advantages are the absence of any moving parts,
floats, cables, stilling wells, gas supplies, purge requirements and
the fact that they cannot plug and are usually unaffected by build-up
of sludge, algae, slime, mud, etc. The major disadvantage is the re-
quirement for the sensing element to physically be in the flow. The
presence of appreciable foam or floating oil and grease can cause er-
rors in most designs.
In a somewhat different design belonging to this class, the probe is
not actually in the stream but is periodically lowered, via a motor-
pulley-cable arrangement, until it makes contact with the water surface,
which completes a microampere circuit through the liquid to a ground
return.
149
-------
This signal reverses the motor, raising the probe above the surface of
the liquid. As in the case with a float, the amount of cable paid out
is the measure of stage. Although this design does not require immer-
sion of the sensor in the flow, it does involve mechanical complexities
and moving parts not characteristic of the other electrical secondary
devices.
Acoustic. This type of secondary device is growing in popularity as
prices decrease. Requiring no physical contact with the liquid, they
enjoy all of the advantages listed for electronic designs. They were
covered in the discussion of acoustic primary devices and will not be
redescribed here. However, a few precautionary words will be given.
For applications where space is restricted as in some manholes and small
meter vaults, problems due to false echos may be encountered. This
problem may be overcome at some sites by shielding the transducer, but
accurate readings (at low flows at least) should not be expected for
flows in round pipes or deep, narrow channels from most designs. Also,
good results should not be expected if the surface of the flow is highly
turbulent or foam covered as the reduced return signal may not be prop-
erly detected.
DISCUSSION
The evaluation tables of the various flow measuring devices and tech-
niques are summarized in matrix form in Table 40. It is re-emphasized
that these evaluations are made with a storm or combined sewer applica-
tion in mind and will not necessarily be applicable for other types of
flows.
Table 41 offers a different (and even more subjective) comparison of
some of the primary devices or techniques that are currently being
used to measure storm and combined sewer discharges. Each method is
numerically evaluated in terms of its percent of achievement of several
desirable characteristics. Dilution techniques as a class appear to be
the most promising of all. In view of the current state of the art,
however, their usefulness is probably greatest as a tool for in-place
calibration of other primary devices. They have also been extremely
useful for general survey purposes and have found some application as
an adjunct to other primary devices during periods of extreme flow such
as pressurized flow in a conduit that is normally open channel.
Acoustic open channel devices are also quite promising; but, because of
their dependency upon the velocity profile and the frequently resulting
requirement for several sets of transducers, they are presently only
justifiable for very large flows in view of the expense involved. The
usefulness of the Parshall flume is evidenced by its extreme popularity.
The requirement for a drop in the flow is a disadvantage, and submerged
operation may present problems at some sites. Known uncertainties in
the headrdischarge relations (possibly up to 5%) together with possible
geometric deviations make calibration in place a vital necessity if
high accuracy is required. Palmer-Bowlus type flumes are very popular
150
-------
TABLE 40. FLOWMETER EVALUATION SUMMARY
Gravimetric-all types
Volumetric-all types
Venturi Tube
Dall Tube
Flow Nozzle
Orifice Plate
Elbow Meter
Slope Area
Sharp-Crested Weir
Broad-Crested Weir
Subcritical Flume
Parshall Flume
Palmer-Bowl us Flume
Diskin Device
Cutthroat Flume
San Dimas Flume
Trapezoidal Flume
Type HS, H S HL Flume
Open Flow Nozzle
Float Velocity
Tracer Velocity
Vortex Velocity
Eddy-Shedding
Turbine Meter
Rotating-Elemeh't Meter
Vane Meter
Hydrometr.ic Pendulum
Target Meter
Force-Momentum
Hot-Tip Meter
Boundary Layer Meter
Electromagnetic Meter
Acoustic Meter
Doppler Meter
Optical Meter
Dilution
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overall. They can be used as portable as well as fixed devices in many
instances, are relatively inexpensive, and lean handle solids in the flow
without great difficulty.
All point velocity measuring devices have been lumped together in the
current meter category. In the hands of a highly experienced operator,
good results can be obtained (the converse is also true, unfortunately),
and they are often used to calibrate primary devices in place or for
general survey work. They are generally not suited for unattended op-
eration in storm and combined sewer flows, however.
Electromagnetic flowmeters show considerable promise where pressurized
flow is assured as do closed pipe acoustic devices. Neither can be
considered portable if one requires that the acoustic sensors be
wetted, a recommended practice for most wastewater applications.
Open flow nozzles and sharp-crested weirs are often used where the re-
quired head drop is available. Weirs will require frequent cleaning
and are best used as temporary installations for calibration purposes.
Flow tubes and Venturis are only suitable for pressurized flow sites
such as might be encountered, for example,, at the entrance to a treat-
ment plant. '
Trajectory coordinate techniques, such as,the California pipe or Purdue
methods, require a pipe discharging freely into the atmosphere with
sufficient drop to allow a reasonably accurate vertical measurement to
be made, a situation not often encountered in storm or combined sewers.
Slope area methods, as explained earlier, must generally be considered
as producing estimates only and, consequently should be considered as
the choice of last resort (despite their apparent popularity).
15;3
-------
SECTION VII
REVIEW OF COMMERCIALLY AVAILABLE EQUIPMENT
The number of commercial firms that offer flow measuring or related
equipment in the market place today is astoundingly large. Even when
attention is limited to devices intended for liquid flowmetering, the
number is still extremely large, probably well in excess of two hundred.
Many manufacturers offer more than one type of primary device (and- these
typically in numerous models), and when combined with secondary device
choices, the possible number is virtually overwhelming. Thus, complete
coverage in a document of this sort is impossible.
The intent of this section is not, therefore, to provide a complete
catalog which lists all manufacturers and discusses all their offer-
ings. Rather an attempt has been made to select a large enough sam-
pling of firms and product's and describe each of these briefly but in
enough detail to allow the reader to appreciate the actual implementa-
tion of the generic flow measurement methods discussed in Section VI.
In accomplishing this, well over 120 manufacturers were contacted
regarding product lines which might be recommended for application to
the measurement of sewer flows. These firms ranged from very large,
well known manufacturers that have offered a wide range of flow -meas-
uring equipment for over a century to relatively small organizations
with a limited product line which has only recently been introduced.
Devices were included which either illustrated one of the generic flow
measurement methods or appeared to embody some novel or interesting
implementation or variation. Even at that, there have undoubtedly
been omissions, and some manufacturers of applicable equipment may have
been overlooked. For this the writers wish to apologize and urge any
firm that feels it has equipment suitable for sewer flow measurement
(or has refined or improved its products) to communicate this informa-
tion to them so that it might be included in any possible future update
of this work.
The common format that has been followed in describing the commercially
available equipment is straightforward and needs no explanation. How-
ever, a few comments on the information presented are needed. All in-
formation for a particular piece of equipment, including specifications,
special claims for it, etc., has been taken from material supplied by
its manufacturer in the form of descriptive brochures, specification
sheets, technical writeups, user manuals, private correspondence, etc.
It was not possible for the writers to verify or authenticate any of
this information, so it must be accepted as manufacturer's claims only.
A comment on prices must also be made. Many manufacturers prefer to
quote on an application basis. In view, of this and the general economic
154
-------
conditions at the time of this writing (Fall 1974), prices where given
should be considered approximations and should be verified with the
particular manufacturer before using, even for general budgetary pur-
poses. For example, one manufacturer who was contacted had just re-
ceived a 25 percent increase from his forging contractor and could not
tell what overall effect this would have on his prices; many suppliers
are quoting prices on a delivery basis; etc. Because of this situ-
ation, attempts to obtain pricing information were curtailed; thus,
some manufacturer's products have no prices given.
All illustrations in this section were taken from photographs, bro-
chures, or other material provided by the respective manufacturers,
and deep appreciation for permission to use them in this report is
hereby acknowledged.
155
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ALPHABETICAL LIST OF MANUFACTURERS
Page
American Chain and Cable Company, Inc ............ 159
•I r o
Astro Dynamics Inc'. ................ ... J-DJ
Badger Meter, Inc.
(Instrument Division) .................. 165
Badger Meter, Inc.
(Precision Products Division) .............. 173
BIF (Division of General Signal) ............. 177
Braincon Corporation . • •> •' ............. : •L8'*
Brooks Instrument Division
(Emerson Electric Company) ................ lbb
Controlotron Corporation ......... • ......
Cox Instrument
(Division of Lynch Corporation) .............. iy°
90?
Gushing Engineering Inc .......... • ....... ^"^
Daniel Industries, Inc .................. 2°4
Drexelbrook Engineering Company .............. 209
Eastech Incorporated ..................
Edo Corporation ................. •
Environmental Measurement Systems
(A Division of WESMAR) .................. 222
Epic Inc. ...................... 224
Fischer &"Porter Co ................... 234
Carl Fisher and Company ................. 2^6
Flow Technology, Inc ...................
251
Flumet Co. ......................
253
The Foxboro Company ..... .............
156
-------
GM Mfg. and Instrument Corporation . . . -. . 256
Hinde Engineering Company of California . 259
Howell Instruments 263
InterOcean Systems, Inc. 267
J-TEC Associates, Inc. . 270
Kahl Scientific Instrument Corporation .... 272
F. B. Leopold Company 275
Leupold & Stevens, Inc. . . 278
Manning Environmental Corporation .. 282
Martig BUB-L-AIR 286
MARV TEC, Inc. . 287
Mead Instruments Corporation 289
Meriam Instrument
(Division of the Scott & Fetzer Company) 291
Metritape, Inc 293
Moore Products Company 299
Muesco, Inc. 3Q^
NB Products, Inc 303
R. M. Nikkei Company 308
NUSonics, Inc. 309
Ocean Research Equipment, Inc 312
The Permutit Company
(Division of Sybron Corporation) 313
Plasti-Fab, Inc. 321
POLCON, Inc.
(An Affiliate of Carl F. Buettner & Associates, Inc.) .... 322
PORTAC
(Min-Ell Company, Inc.) 325
157
-------
RAMAPO Instrument Company 331
Robertshaw Controls Company 335
Saratoga Systems, Inc. 338
Scarpa Laboratories, Inc 342
Sigmamotor, Inc. 345
Singer - American Meter Division 347
Sparling Division
(Envirotech Corporation) • 350
Taylor
Sybron Corporation
Taylor Instrument Process Control Division 353
Thermal Instrument Company 357
Tri-Aid Sciences, Inc. 36°
Universal Engineered Systems, Inc. 362
Vicfcery - Simms, Inc. • • 367
Wallace - Murray Corporation
(Carolina Fiberglass Plant) .-•• 369
WESMAR Industrial Systems Division 370
¥estinghouse Electric Corporation 373
158
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MANUFACTURER: AMERICAN CHAIN AND CABLE COMPANY, INC.
ACCO BRISTOL DIVISION
WATERBURY, CONNECTICUT 06720
TELEPHONE (203) 756-4451
PRODUCT LINE: FLOWMETERING SYSTEM
DESCRIPTION:
The Bristol Series 840 L/V Monitoring System is designed to measure the
level and velocity of sewer flow in larger (over 1m) sewer conduits.
It is^engineered primarily for manhole installation, can be positioned
at existing manholes, and can be moved from one manhole to another for
the purpose of making surveys of a sewage system. The monitoring sys-
tem, shown in Figure A, consists of three major subassemblies: monitor
assembly, probe controls, and a probe operator or hoist assembly. A
single, self-cleaning probe is used for both velocity and flow level
measurement. It is designed to withstand the corrosive environment of
a sewer system and the impact of heavy objects.
The velocity of the flowing liquid is determined by a drag-type primary
element which is located within the probe assembly. A hermetically-
sealed flexure assembly is fastened to a cylindrical "target" area and
contains a four-arm strain gage bridge together with the necessary com-
pensating networks. As the moving stream impinges on the target area,
an impact force is developed which is proportional to the square of the
velocity of the stream. The impact force causes a linear deflection of
the flexure, which is detected by the strain gage bridge. An excita-
tion voltage from the strain gage power supply feeds the velocity
sensor. Calibration is such that velocity of 0 to 3 m/s (0 to 10 fps)
corresponds to an output signal of 0 to 20 mV. Thus, the force exerted
on the target.area is converted to an electrical output signal from the
strain gage sensor. This millivolt signal is then amplified (in the
Probe Controls cabinet) to 0 to 10V which, in turn, becomes the input
signal to an electronic solid-state square root extractor. The square
root extractor (also in the Probe Controls cabinet) converts the signal
to a voltage signal linear with velocity.
The level sensing device in the probe ensures that the probe is always
at a predetermined level of submersion in order to accurately measure
the stream velocity .at a reference level. It also detects the need for
probe cleaning. An air bubbler arrangement is used for determining
the level of probe submersion. This is done by sensing the bubbler
backpressure. The bubbler outlet hole is located at the lower end of
the probe adjacent to the target 'area of the velocity measuring device,
in a position where it is not affected by the velocity of the flowing
liquid. Should debris cause clogging, the probe has the capability of
cleaning itself. This is accomplished by using the pneumatic cylinder
159
-------
Figure A
160
-------
to retract the probe through a tight-fitting wiper sleeve and then re-
positioning it. Simultaneously, a high-pressure air purge is directed
at,the velocity target area and also through the bubbler outlet hole.
Normally the self-cleaning cycle is acfuated at 15-minute intervals.
SPECIFICATIONS:
Size, Weight and Other
Physical Facts:
Power Requirements:
Sewer Conduit Sizes:
Liquid Level Ranges:
Velocity Measurement
Range:
Air Supply:
Sensitivity:
Typical Accuracy:
Repeatability:
Readout:
Installation Hardware:
Telemetry Output.:
Size and weight of the Monitor assembly
can vary with the installation site
requirements* A typical assembly for a
1.52m (5 ft) sewer conduit weighs ap-
proximately 136 kg (300 Ibs.) and re-
quires a trolley of 2.44m (8 ft) in
length.
120V, 60 Hz, single phase, 30 ampere
service.
1.22 to 6.1m (4 to 20 ft) (standard).
20.32 cm (8 in.) to full conduit
0 to 3 m/s: (0 to 10 fps)
Included in Probe Controls cabinet.
±0.64 cm (1/4 in.) change in liquid
level.
Velocity, ±5%
Level, ±0.64 cm (1/4 in,)
No measurable changes in velocity and
level over a period of one year.
Analog-type panel meters included in
Probe Controls cabinet.
OPTIONS
As required.
Two channels; one for velocity, one for
liquid level. Either solid-state pulse
duration or variable frequency may be
considered. (Plug-in space is reserved
161
-------
in the Probe Controls cabinet for either
type of telemetry circuit boards, and
for optional audio tone equipment.)
PRICE:
Prices are quoted at time of order based upon details of specifications-
e.g. size, construction materials, etc.
COMMENTS:
Since this unit only provides the flow depth and velocity at about
15.2 cm (6 in.) below the free surface, calibration of the site would
appear necessary in order to relate these two parameters to total dis-
charge. The unit was not designed for smaller pipe sizes, i.e. under
1.22m (4 ft), and does not appear suitable for such applications.
162
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MANUFACTURER: ASTRO DYNAMICS INC.
SECOND AVENUE
NORTHWEST INDUSTRIAL PARK
BURLINGTON, MASSACHUSETTS 01803
TELEPHONE (617) 272-3900
PRODUCT LINE: VOLUMETRIC-FLOWMETERS
DESCRIPTION:
This company has developed a somewhat unique (patent pending) volumetric
flowmeter. Its primary element essentially consists of a positive dis-
placement (gear type) pump that is driven by a variable speed motor so
as to maintain a zero pressure drop across the flowmeter. The secondary
element is a counter that reads pump speed which is directly related to
flow. A simplified block diagram of the unit is shown in Figure A.
FLUID
FLOW
AP
TRANSDUCER
'
>K
METERING PUMP
H— i
^-r-1
ARTARI P
TACH
GEN
DIGITAL
INDICATOR
FLOW RATE
SPEED
D.C. MOTOR
CONTROLLER
Figure A
163
-------
The chief advantage of this approach would seem to arise from the fact
that the slip factor, which is inherent in all such types of volumetric
flowmeters, is greatly reduced with a nearly zero pressure differential.
At the present time these flowmeters have only been built in rather
small sizes, i.e., up to 577 &ph (150 gph), but this is not an inherent
limitation of the basic design. The unit was developed to meet a re-
quirement for accuracies of ±0.2% of reading and repeatability of ±0.1%
of reading; these have apparently been met. Ranges of up to 100:1 are
possible, but 15:1 is more typical.
Units are available with either analog (0-10 VDC proportional to flow
rates) or digital (pulse rate proportional to flow rate) outputs.
Digital panel meters to read totalized flow (counter) or flow rate
(digital voltmeter calibrated in gph) are optional at extra cost.
SPECIFICATIONS:
Characteristics
Range, Iph (gph)
Power
Dimensions (W,H,L),
era (1n)
Tubing Connections,
cm (in)
Max. System
Temperature, C (F)
Model
LFH - 1.5 (A) or (D)
0.39-5.68 (0.1-1.5)
115 VAC, 10, 60 Hz
17.8x17.8x25.4
(7"x7"xlO")
0.64 (1/4")
(150°F)
LFH - 15 (A) or (D)
3.79-56.77 - (1-15)
Same
17.8x17.8x25.4
(7"x7"xlO")
0.64 (1/4")
Same
LFM - 150 (A) or (D)
37.85-567.75
(10-150)
Same
30x30x35
(12"xl2"xl4")
0.3
1 .23 (1/2")
Same
PRICE: $1,000 (approx.) and up.
COMMENTS:
This is a very ingenious device, but its application to wastewater
flows must be considered limited due to its small capacity and poten-
tial problems with suspended solids, among other reasons.
164
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MANUFACTURER:
BADGER METER, INC.
INSTRUMENT DIVISION
4545 WEST BROWN DEER ROAD
MILWAUKEE, WISCONSIN 53223
TELEPHONE (414) 355-0400
PRODUCT LINE:
PRIMARY DEVICES - FLOW TUBES, NOZZLES, PARSHALL FLUMES
SECONDARY DEVICES - METER TRANSMITTER, ELECTRONIC RECEIVERS
DESCRIPTION:
The Water Meter Division of Badger has manufactured nutating disc type
water meters for a number of years. However, because of the total un-
suitability of such devices for raw sewage, they will not be included
in this discussion.
Pr-imary Devices
Flow Tubes - The Instrument Division offers, as primary elements, the
proprietory "Lo-Loss" flow tubes. These tubes are available in a wide
choice of designs, materials, and sizes and may find some application
in wastewater flow measurement. Figure A shows typical "Lo-Loss"
designs.
PLASTIC CAST IRON
Figure A
165
-------
The chief advantage of the "Lo-Loss" design is its extremely low head
loss (claimed to be the lowest of•any primary element) even as compared
to a long form Venturi tube. Unrecovered pressure loss as a percent of
differential seldom exceeds 6%, and values of 3% are quite common. The
available models include both full flanged and insert designs. Types
PMT and PMT-U have manual vent cleaners for measuring sewage or
slurries. Type PMT-S is a single-tap, full-flanged model design for
sewage, sludge, or fluid high in suspended solids. Available designs
are shown in Figure B.
Open Flow Nozzles. Parshall Flumes - Badger Meter Inc. also offers open
flow nozzles and Parshall flumes as primary devices.
Secondary Devices
Transmitter - The ML-MN transmitter (Figure C) is a secondary device
designed for open channel flow head measurement. As flow varies, the
transmitter's in-stream float senses the changing liquid level in the _
primary flow device. Through a single link from a stainless steel main
shaft, the float's motion is relayed directly to core which moves ver-
tically within the transmitting coil. The coil emits a signal voltage
in direct relation to the core position. This signal is transmitted to
the electronic receiver as discussed in the description of the elec-
tronic receiver.
Advantages of this device, when compared to float-cable instruments
which require stilling wells, are reported to be as the following:
• INSTALLATION ECONOMY...Excavation and concrete pouring for
meter chambers are minimized. Stilling well and complex
piping eliminated.
• MAINTENANCE ECONOMY..Clear water purge, routine cleanouts,
cables, and counter weights also eliminated.
• ACCURACY CHECK...A mechanical position reference is furnished
as standard equipment to provide a quick, positive calibra-
tion check.
• APPLICATION VERSATILITY...ML-MN transmitter and electronic
receiver can be used with Badger Meter open flow nozzles,
Parshall flumes, and weirs. Accurate response is also
assured with Palmer-Bowlus flumes, standing wave flumes,
and any other device for which the head-discharge relation-
ship has been established up to a float travel of 0.8m
(32 in.).
166
-------
TYPE PMT: FULL FLANGED CAST IRON
This cast iron tube has a bronze-lined throat in which the
averaging annulus is accurately machined with the body.
Stainless steel throat also available. Manual vent
cleaners provided for sewage, slurries or other fluids
with suspended solids.
TYPE PMM: PLASTIC INSERT
the pqlyester-fibreglass body, .tapped holding flange,
and throat with internal annulus are molded as an in-
tegral unit. Throat and mounting flange are available in
a variety of materials. Suitable for liquids and gases up
to 200° F. Minimum operating temperature minus 20° F.
TYPE PMT-C: "CONTROLLER" TUBE
This model is similar to Type PMT except that it will
accommodate a valve immediately downstream for rate-
of-flow control. Outlet flange may be smaller than line
size to permit a smaller valve. A standard increasing
elbow or increaser is used to return to full line size.
TYPE PMT-S: SINGLE TAP, FULL FLANGED
Designed for sewage, sludge or fluids with suspended
solids. This tube has single taps for the high pressure and
for the low pressure connections. Each tap is equipped
with manual vent cleaner to permit periodic cleaning.
TYPE PMT-IF: FABRICATED INSERT
Designed primarily for clear fluids, Type PMT-IF is
available in a variety of materials to suit specific applica-
tions. Can be supplied in carbon or stainless steel,
aluminum, chrome-moly and other metals. Pressure con-
nections are conveniently located in mounting flange.
TYPE PMT-U: FABRICATED FULL FLANGED
This Lo-Loss tube offers wide flexibility in materials and
design. An economical buy, particularly in the larger
sizes. Can be supplied with single or multiple taps.
Also available.with manual vent cleaners for measuring
sewage or slurries.
Figure B
167
-------
MOUNTING BRACKET f
(ALTERNATE POSITION)1-^)
(WATER-TIGHT SEAL)
TRANSMISSION
LEADS
WATER-TIGHT
SEAL
NEOPRENE
BOOT .
MOUNTING
.^BRACKET
INDUCTANCE
COIL
CORE
LINKAGE
SHAFT
Figure C
168
-------
Electronic Receiver - The Badger Meter Inc. 2700 Series electronic re-
ceiver (Figure D) is connected to the transmitter (Figure C) by three
transmission lines (Figure E), and power (110 VAC, 60 Hz) is applied
only to the receiver. An actuating signal or error voltage is pro-
duced by the movement of the transmitting corerwithin its coil which
unbalances the electrical bridge. This signal is amplified to drive
a two-phase, reversible servo motor which runs at a speed proportional
to the error signal and in a direction established by the phase. Rota-
tion of the motor repositions the core in the receiving coil and
reduces the error signal to zero. As a result, the electrical bridge
is restored to a null-balance condition. The pen, indicator pointer,
and_totalizer mechanisms are positioned simultaneously when the system
is in balance; thus there is no time delay for recycling.
Receiver Style 2701 serves the combined functions of a recording, in-
dicating, and totalizing instrument; Style 2705 is used as a remote
indicator only.
As reported by Badger Meter Inc., the 2700 series electronic receiver
can be used with a variety of transmitters for the measurement of flow,
level, pressure, or temperature. For the convenience of the operator,
the receiver can be located up to 5000 feet away from the transmitter
without impairing calibrated accuracy (±1% of actual value being meas-
ured over the range specified for the transmitter) or speed of response.
A selection of 30.5 cm (12 in.) diameter charts, with either 24-hour or
/-day rotation, can be made from more than 500 standards available.
SPECIFICATIONS:
jPrimary Devices
• The laying length of a typical "Lo-Loss" flow tube is
roughly 2.5 times the pipe diameter. Stock units are avail-
able for pipe diameters ranging from 7.6 to 121.9 cm (3 to
48 in.), and other sizes can be obtained upon request.
• Bronze, carbon or stainless steel, aluminum, chrome-moly,
and polyester-fiberglass are among the available construc-
.tion materials.
• Standard accuracies of ±1% are claimed (or ±0.25% when
laboratory calibrated).
- Ranges (see comparative rangeability of Figure F) of
20:1 are common, and even at 50:1, the meter coefficient
deviation is only 2%.
169
-------
•COIL
i IhCCRE
TRANSMITTER
Figure D
nov.
60 CYCLE AC
SUPPLY
CALIBRATED
CAM
SERVO
MOTOR
ELECTRONIC
AMPLIFIER
RECEIVER
Figure E.
170
-------
I £.
ul + 1
UJ
O
0
Z 0
O
< - 1
111
Q -2
X
I I
. LO - LOS
/
^
X
•MMMBiHI
^Vl
^*
•0MM
^
EN-
S
ruRi (A. !
5. M. E.)
4 5
10 9 4 6 8 m 9 /ic
: c
••
> 11
(RD) PIPE REYNOLDS NUMBER
Figure F
Secondary Devices
Range
Dimens-ions,
(W, H, L)
Power
Response Time
HL-MN Transmitter
10:1 {20:1 available for
extra cost)
25.8cra x. 25.4cm x 32.4cm
,(10-3/16in x lOin x 12-ll/16in)
N/A
N/A
2700 Series
Receiver
N/A
22.2cm x 39.1cm x 48.9cm
(8-13/16in x 15-5/8in'x 19-3/16in)
110 VAC, 60 Hz
8 sec. (0 to Full Scale)
PRICE:
Primary Devices
"Lo-Loss" Flow Tubes
3 in. - $ 716.00
48 in. - 11,700.00
171
-------
Open Flow Nozzles
Parshall Flumes
6 in.
24 in.
3 in.
24 in.
$ 640.00
3,900.00
280.00
1,565.00
Secondary Devices
ML-MN Transmitter/2700 Series
Electronic Receiver $ 1,150,00
COMMENTS:
Primary Devices
Where pressurized flow is always present, the »Lo-Loss» flow tube could
prove to be a useful primary device for measuring storm or combined
sewer flows at fixed installations, if proper attention is paid to the
secondary element to avoid clogging problems.
The other primary devices offered by Badger (open flow nozzles and
Parshall flumes) were thoroughly discussed in Section VI and will not
be commented upon further here.
Secondary Devices
The ML-MN transmitter will withstand submergence, even though it will
no longer operate because the float is off scale. Its 0.8-meter ^
(32-inch) float travel allows it to be used with many primary devices.
As with any float-in-flow secondary device, it suffers from the pos-
sibility of fouling (or even physical damage) from floating debris.
The electronic sensing system offers advantages over more cumbersome
cable and counterweight designs.
172
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MANUFACTURER:
PRODUCT LINE:
DESCRIPTION:
BADGER METER, INC.
PRECISION PRODUCTS DIVISION
6116 EAST 15TH STREET
TULSA, OKLAHOMA 74115
TELEPHONE (918) 836-4631
ULTRASONIC FLOWMETER;
ULTRASONIC TRANSMITTER
Badger Meter, Inc. has entered into a cooperative agreement with Tokyo
Keiki Seizosho Company, LTD. of Japan to market (within the United
States) the ultrasonic flowmeter developed by the latter company.
There are essentially three devices offered, and sales are through the
•Precision Products Division. A typical ultrasonic meter installation
for full pipe flow is shown in Figure A.
REMOTE
INDICATION
ELECTRONIC UNIT
UF-100 Unidirectional
UF-110 Bidirectional
PROBECABLES
TYPICAL INSTALLATION
OF ULTRASONIC METER
Just Strap Around the Pipe
No Installation Delays
No Interruption of Flow
No Parts in the Stream
Figure A
173
-------
Ihe ultrasonic flowmeter uses the propagation of ultrasonic energy
across a fluid stream to determine flow velocity. These devices are
designed for -metering raw and treated sewage and wastewaters; also,
many industrial fluids can be metered.
Model UF-100 (Unidirectional) and UF-110 (Bidirectional) Flowmeters -
These are complete ultrasonic flowmeters for measuring full flow in
pipe sizes of 0.3m (1 ft) and larger. These devices employ a pair of
ultrasonic velocity probes that are strapped to the outside of the pipe
wall. A clearance area measuring at least 1.2m (4 ft) greater than the
pipe diameter in each dimension is required. The device can be in-
stalled in existing as well as new construction and produces no head
loss since there is nothing inside the pipeline. The velocity probes
utilize the "sing-around" principle* to measure average fluid velocity
within the pipe which is combined with pipe cross-sectional area to
produce an output signal (4-20 mADC) proportional to flow. A wide
selection of 30.5 cm (12 in.) diameter charts is available with either
24-hour or 7-day rotation. A totalizer option is also available.
Model UF 310A Flowmeter - This model is a complete open channel ultra-
sonic flowmeter that does not require the use of a weir, flume, or other
pre-rated structure. It employs a pair of ultrasonic velocity probes
and combines their output with flow depth as measured by an ultrasonic
depth probe (essentially the probe of Model UH 200) and channel cross-
section to produce an output signal (4-20 mADC) proportional to flow.
The device can be installed in existing as well as new construction
and will produce little or no head loss since, at most, only the small
velocity probes need be in the flow. As with the Models UF-100 and
UF-110, the velocity probes operate using the "sing-around" principle.
Channel shapes can be either circular, rectangular, trapezoidal, or
elliptical. As shown in Figure B, the velocity probes are generally
mounted in, or attached to, the channel walls at about 25% of maximum
depth. A wide selection of charts (identical to those for Models UF-100/
110) is available, as is a totalizer option and bidirectional capability.
The three probes, which together weigh 38.6 kg (85 Ibs), may be located
up to 305m (1000 ft) from the electronics box, which is a small wall-
mounted unit weighing 68 kg (150 Ibs).
Each received sonic pulse triggers the transmission of another pulse
across the flow stream in a "sing-around" fashion. The number of
such pulses occurring in a one-second period is called the sing-
around frequency.
174
-------
Electronics
Output 4-20 MADC
Figure B
Model UH 200 or UH 210 Ultrasonic Flow Transmitter - This equipment has
an output signal proportional to level (UH 200) or flow (UH 210) and
serves as a secondary element for level and flow indicating, recording,
and totalizing measurements in flumes, weirs, or other open channel
primary elements. The device employs an ultrasonic probe set in a com-
mon head. The acoustic signal is transmitted to the fluid surface
(see Figure C), and the elapsed travel time for the reflected signals'
return is converted into fluid depth. As the level of the fluid
Iv
J2
INSTALLATION
A. Transmitter shall be placed at least 6" above
maximum level not to exceed the Ah above
maximum level (i.e. Ah min. = 6")
B. Total transmission length shall not exceed
10' 6"
C. The horizontal plane across the face of the
probe shall be level to within ± 2°
Figure C
175
-------
surfaces changes, the TJH. 200 produces a proportional signal (4-20 mADC).
Model UH 210 incorporates a digital function generator which allows
direct and continuous conversion of the fluid level signal to any
specified depth-discharge relationship. This can be changed in the
field to allow use with different primary elements. A wide variety of
30.5 cm (12 in.) diameter charts is available with either 24-hour or
7-day rotation.
SPECIFICATIONS:
Characteristic
Resolution
Accuracy
Output
Analog
Time Pulse
Digital '
Probe Cable Length
Power
Dimensions
Electronics
Junction Box
Probe(s)
Height
Electronics
Junction Box
Probe
Model
UF-100 and 110
±1% of Full Scale
±1% of Full Scale
4-20 mADC Into lOOOn
3-9-3 (15 sec. period)
48V Pulse (Train Scaled)
Up to 305 meters (1000 ft)
115 VAC, 60 Hz, 3A
57 x 64 x 30 cm
(22.44x25.20x11.81 In)
8.4 x 18 x 20 cm
(3.3x7.1x7.9 In)
12.4 x 15.0 x 18.3 cm)
(4.9x5.9x7.2 1n)
54 kg (119 Ibs).
2.5 kg (6 Ibs)
16.8 kg (37 lbs)(2)
UH-200 and 210
±1/4% of Full Scale •
±2% of
Same
H/A
N/A
Same
Same
Full Scale
22.7 x 13.7 x 34.3 cm
(10-1/2x5-3/8x13-1/2 1n)
N/A
8.9 cm
6.4 cm
7.3 kg
N/A
1.8 kg
(3.5 In) D1a. X
(2.5 in) High
(16 Ibs)
(4 lbs)(l)
UF-310A
±1% of Full
±3% of Full
Same
N/A
N/A
Same
Same
N/A
N/A
38.6 kg (85
Scale
Scale
lbs)(3)
PRICE: Models UF-100 and TJH-110 start at about $1,000
Model UF-310A starts at about $3,000
Models TJH 200 and UH-210 start at about $3,000
COMMENTS:
These ultrasonic flow measurement devices have performed fairly well
in their somewhat limited (up until now) use in this country. Mod-
els UF-310A and the UH series are especially well suited for storm and
combined sewer flow measurement. There have been some reports of prob-
lems due to echos or false returns from the TJH series probes. Some
field workers have put a short piece of plastic pipe over the head and
obtained improved results.
176
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MANUFACTURER: BIF - A UNIT OF GENERAL SIGNAL
1600 DIVISION ROAD
WEST WARWICK, R.I. 02893
TELEPHONE (401) 885-1000
PRODUCT LINE:
PRIMARY DEVICES - PARSHALL FLUME LINERS, VENTURI TUBES AND NOZZLES,
DALL FLOW TUBES, KENNISON OPEN FLOW NOZZLES
SECONDARY DEVICES - "CHRONOFLO" TRANSMITTER AND RECEIVER UNITS, PRESSURE
SENSORS, TOTALIZERS, AND INDICATORS
DESCRIPTION:
BIF, a unit of General Signal Corporation, has been active in the water
flow measuring field for over 100 years. Their primary flow measuring
products include such devices as Parshall flume liners, the recently
developed Universal venturi tube which has largely replaced their Dall
flow tubes, and Kennison open flow nozzles. BIF also offers the Solids
Bearing Fluids (SBF) Flowmetering System, which is reported to provide
precise, highly sensitive detection of differential pressures created
by Universal Venturi Tubes when the measured fluid is high in suspended
solids.
BIF's secondary units are represented by several Chronoflo transmitter
and receiver units for indicating flow depths in primary devices.
Parshall Flume Liners - BIF's precision-molded, one-piece plastic
Parshall flume liner, Model 141, is said to accurately duplicate Parshall
flume proportions. It is light-weight and can be easily installed with-
out the aid of a crane or special tools; there are also no seams re-
quiring special cements or sealing compounds. BIF plastic Parshall
flume liner Model 141 is available in throat width sizes ranging from
7.62 cm (3 in.) to 2.44m (8 ft) to accommodate flow rates ranging from
75.7 kid (.02 mgd) to 341,255 kid (90.16 mgd). Parshall flumes were
throughly treated in Section VI and will not be discussed further here.
Universal Venturi Tube - BIF has developed a proprietary, differential-
pressure primary device that combines the metering performance of the
classical venturi tube with some of the more desirable features of dif-
ferential pressure devices such as the Dall flow tube. It offers ex-
tremely short laying lengths (less than half that of a short form
classical venturi tube), a great magnification of the differential
pressure signal (about twice that of classical Venturis), and low per-
manent head loss (almost as little as a Dall tube). The advantages
offered by the Universal Venturi Tube are due to its unique hydraulic
design, especially from the inlet to the throat tap (see Figure A),
177
-------
that "conditions" the flow by creating a consistent artificial tur-
bulence in the throat flow pattern so that readings are stable and
predictable. No blending radii are used, so flow separation and
stream-line bending are employed as in the Ball tube.
-t M—W .'
..t^CORNBt INLET UP
JU4
Figure A
The Universal Venturi Tube is available in line sizes from 2.5cm (1 in.)
to 1.2m (4 ft) as stock and up to 2.4m (8 ft) on special order. Even
larger units can be made on request. Series 180 Universal Venturi Tubes
are available as insert types or flanged types. Standard tubes have
cast iron bodies and bronze throats with the cast iron surfaces (both
interior and exterior) finished with tar or Bitumastic paint. A large
variety of other materials are available in weldment form, and fiber-
glass reinforced plastic insert types are also standard construction.
The tube coefficient is virtually independent of the Beta ratio (ratio
between throat and inlet diameters), the pipe Reynolds number (above
about 50,000), and line sizes. There is virtually no installation
effect caused by upstream piping configurations, and downstream piping
causes no effect whatsoever. As a result, uncalibrated accuracies of
±0.75% can be guaranteed and, with calibration, ±0.25% is achievable.
Standard ranges are around 5:1.
Kennison Open Flow Nozzle - This open flow nozzle is a simple device for
measuring flows through partially filled pipes. The nozzle handles low
flow and wide flow ranges with ease. Because of its high accuracy,
non-clogging design and excellent head versus flow characteristics, the
Kennison nozzle is well suited for the measurement of raw sewage, raw
178
-------
and digested sludge, final effluent, and trade wastes. The Kennison
Nozzle is constructed of high tensile cast iron. The piezometer vent
opening is bushed in brass and is equipped with a bronze-mounted manual
vent cleaner. Hydraulically-operated vent cleaning can also be used
where the nozzle is installed in inaccessible places. The nozzle is
available in inlet diameters of 15.2 to 91.4 cm (6 to 36 in.) and will
accommodate flows of 340 to 53,000 £pm (90 to 14,000 gpm).
Uncalibrated accuracies of ±2% for a range of 10:1, ±3% for a range of
15:1, and ±5% for a range of 20:1 have been demonstrated. Special
laboratory calibration will assure accuracy within ±1% of actual flow
for a range of 20:1. A Kenniflo rate.indicator is available for use
with the nozzle to provide visual evidence of instantaneous rate of
flow. This indicator can be graduated in gpd, gpm, or mgd as well as
inches of head.
Solids Bearing Fluid Flowmetering System (SBF) - As shown in Figure B,
the SBF system is built around a combination of components — the
primary element, a Universal Venturi Tube Model 185 (UVT) (center); two
pressure sensing probes (upper right); and a differential pressure
transmitter (lower left). All of these components may be purchased .
individually. Claims made for this system include:
• No electrical components are in contact with line fluid.'
• Water purging is eliminated.
• No circuit fouling or drift occurs.
Instrumentation lines cannot be fouled by solids or
entrained gases.
• System is unaffected by changes in static line pressure.
• Sensors can be removed while line is in service.
• System provides highly sensitive detection of flow signals
produced by the venturi tube.
• All readings can be verified by a simple manometer.
The above is accomplished by the direct one-to-one transfer of pressure
through a limp diaphragm which is held at a precise null position,
regardless of the magnitude of the measured pressure, by a pure silicon
fluid pressurized by a miniature hydraulic gear pump. The liquid is
delivered continuously through a filter to the probes at a pressure
consistent with line pressure, and exhaust fluid is fed back to the
179
-------
Manometer connection
New SBF Flowmetering System has no electrical probes...
eliminates open type pressure taps subject to clogging. SBF
uses 'live" liquid filled null sensors that fit flush to the
flowmeter wall to transmit differential pressure signals
to instruments.
Figure B
180
-------
pump reservoir. Due to the reset action provided by the supply-exhaust
regulator unit associated with each probe, sensing diaphragm movement
is limited to less than 0.03 mm (0.001 in.). The center button of the
diaphragm carries one end of an armature, the other end of which is
supported and centered by a spiral-spring bearing. The end of the
armature acts as a baffle and floats close to the nozzle, regulating
exhaust of the fluid from the probe to the exhaust pressure regulator.
This probe system is highly responsive to rapid pressure changes,
essentially behaving like a filled-and-sealed system.
Transmitter Units - BIF manufactures several secondary transmitter
units. The Model 231-08 is a float actuated, free-standing, weather-
proof Chronoflo transmitter-indicator mounted in a waterproof stand
for level indication at its location. It also transmits readings to
Chronoflo receivers for remote indicating and recording. The remote
signal line requirements can be met by leased .signal facilities equi-
valent to low frequency telegraph channel capable of repeating time-
duration impulse closures or a private metallic pair with a maximum
loop resistance not to exceed 2500 ohms.
The BIF Chronoflo Model 231-09, used for flow rate determination, is
identical to the Model 231-08 in appearance, weight, and signal line
and power requirements. Both are designed for stilling well operation.
The BIF Chronoflo Model 231-34 is an in-stream, float-operated elec-
trical transmitter designed especially for use with head-area primary
flow measuring elements such as Parshall flumes, Kennison nozzles,
weirs, and other open flow primary devices. This transmitter operates
with equal facility over telephone or teletype lines, telegraph cir-
cuits, private signal lines, tone or microwave links. The unit con-
sists of the transmitter, indicator (optional extra), a spherical,
truncated float manufactured of ABS plastic, and a nylon-coated,
stainless steel float cable.
The Model 251-08 electronic differential pressure transmitter is a
compact transducer designed to translate a differential pressure into
a DC current signal and is designed to work with the SBF flow metering
tubes only.
Miscellaneous - BIF also manufactures a line of pressure sensors and
Chronoflo receivers, recorders, and summator/subtractor totalizer units
for use with the primary and secondary units described above.
The SBF system's recording device is BIF's electronic receiver and is
available in either strip or round chart, compact or full case models.
The electronic receiver will accept both 4-20 mA and 1-5 volt signals.
181
-------
SPECIFICATIONS:
Typical specifications for the BIF line of secondary flowmetering
devices are as follows:
Accuracy:
Dimensions:
Model 231-08 Transmitter
±0.5% for a range of 100:1
143.5 cm (56-1/2 in.) height with a
base dimension of 48-1/4 by 31 cm
(19 x 12-1/4 in.).
Weight: 136 kg (300 Ib).
Power: 115 VAC, 60 Hz @ 6 watts
Model 231-09 Transmitter
Standard Accuracy: ±0.5% of maximum rate.
Extended Accuracy: ±1% of actual reading.
Range:
10:1 for a maximum float travel of
12.7 cm (5 in.) to 30.48 cm (12 in.).
20:1 for maximum float travel of
30.48 cm (12 in.) to 76.2 cm (30 in.).
Model 231-34 Transmitter
Standard/Extended Accuracy: ±2%/0.5% of maximum instrument reading.
Range:
10:1 for maximum float travels from
12.7 to 30.5 cm (5 to 12 in.);
Dimensions:
20:1 for maximum float travels over
30.5 cm (12 in.), except on applica-
tions with Parshall flumes or Kennison
nozzles where head at maximum rate is
less than 2.54 cm (1 in.) for maximum
float travels up to 45.7 cm (18 in.),
or 3.81 cm (1.5 in.) for maximum float
travels over 45.7 cm (18 in.).
Float - 15.24 cm (6 in.) dia.
Float Cable - 0.09 cm (0.035 in.) dia.
182
-------
p°wer: 115 VAC, 60 Hz, Single Phase
PRICES: ......
Standard prices not available at the time of this writing.
COMMENTS:
Parshall flumes and Kennison open flow nozzles were discussed fully in
Section VI and will not be commented upon further here. The Universal
Venturi Tube would appear to be one of the better differential-pressure
type primary devices for use with sewage. Its requirements for full
pipe flow and. small range (5:1) may limit its. application, however.
The pressure probes used in the SBS would seem useful for other
differential-pressure devices and can be purchased separately. They
could be used with existing'differential pressure devices where line
plugging or other problems have been high and maintenance troublesome.
183
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MANUFACTURER: BRAINCON CORPORATION
A COMPANY OF TALLEY INDUSTRIES, INC.
MARION, MASSACHUSETTS 02738
TELEPHONE (617) 748-1085
PRODUCT LINE: CURRENT METERS
DESCRIPTION:
The Braincon Corporation produces two basic types of primary current
meters. The type 381 and 1381 Histogram current meters utilize 2/3 and
full size Savonius rotors, respectively, and record current rates on
16 mm film by taking time exposures of radio-luminous sensor indicators.
Braincon maintains complete processing and data translation facilities.
These current meters will not be discussed further since application in
the measurement of wastewater flow rates is inappropriate.
Braincon has developed a Model 720 electromagnetic current meter that
is capable of monitoring flows between 0 to 2 m/s (6.6 fps). It uses
an orthogonal array of four electrodes in the sensor head to present
instantaneous readings of the N-S, E-W components of the flow. The
output voltage varies linearly with the velocity of the fluid flow over
the sensor head. The Model 720 meter utilizes an oblate ellipsoidal
form (discus) probe that efficiently preserves laminar flow over a
generous range of adverse conditions. Of interest is its superior per-
formance improvement over historically accepted mechanical transducers
such as the Savonius rotor. Also noteworthy are the total freedom from
any mechanical designs; the use of a solid state fluxgate magnetometer
rather than a conventional compass; its high resistance to fouling;
lower meaningful measuring thresholds; the use of Cartesian coordinates
rather than polar; instantaneous readout of N-S, E-W vector components;
high sensitivity to the physical environment; a faithful cosine response;
and less application dependency in critical wave-zone effect areas.
The 720 current meter can be used with a variety of readout devices if
the proper interface is provided. Lengths of electrical cable up to
approximately 30m (100 ft) are provided as standard equipment with the
Model 720, with additional lengths available.
SPECIFICATIONS:
Output:
Accuracy:
Threshold:
±2 VDC full scale (other ranges
available)
±1.5 cm (0.6 in.)/sec or 2% of full
scale
< 2 cm (0.78 in.)/sec
184
-------
Resolution:
Power:
Operating Temperature:
Length:
Diameter:
Weight":
0.5 cm (0.2 in.)/sec
24 ± 4 VDC
-2°C (28°F) to 40°C (104°F)
107.6 cm (42.35 in.)
20.3 cm (8 in.), maximum
23 kg (50 Ib)
PRICE: Standard surface readout model: $5,000
Deep-water, long-term implant model: $8,000
COMMENTS: '
This electromagnetic current meter was designed for oceanographic ap-
plications, but may find some use as a portable current meter for
attended operation in measuring wastewater flows. Its low upper veloc-
ity limit will severely restrict its use, however.
185 .
-------
MANUFACTURER:
PRODUCT LINE:
DESCRIPTION:
BROOKS INSTRUMENT DIVISION
EMERSON ELECTRIC COMPANY
407 WEST VINE STREET
HATFIELD, PENNSYLVANIA 19440
TELEPHONE (215) 247-2366
VARIABLE-AREA FLOWMETERS, TURBINE FLOWMETERS, POSITIVE
DISPLACEMENT FLOWMETERS PROPELLER METERS, LIQUID LEVEL
INSTRUMENTS, ELECTROMAGNETIC FLOWMETERS, ETC.
Brooks manufactures a complete line of glass and metal metering tube
variable-area flowmeters (rotameters) in sizes to 12,000 &/m (3,200 gpm)
and priced from $50 to $6,000. A number of pneumatic or electric trans-
mitters, receivers, alarms, etc., are available as accessories. Noae of
these is considered suitable for wastewater flow measurement and,
consequently, no further discussion of them will be given.
Primary Devices
Brooks turbine flowmeters are manufactured in six different series for
use in various types of service, including chemical, cryogenic, air-
craft fueling, and petroleum pipelines, etc. Ranges of 10:1 are stand-
ard, and accuracies as great as ±0.15% (with repeatability within
0.015%) are available with the Series M viscosity-compensated turbine
meters. Prices range from $340 to $13,800. Brooks also offers a com-
plete line of accessories including indicators, totalizers, printers,
etc.
Brooks manufactures nutating disc, oval gear, oscillating piston, and
bi-rotor type positive displacement meters in various models and sizes,
all of which are designed for clean fluid service only. The same is
true of their bulk water propeller meters. Since their application to
wastewater flows is not recommended, they will not be described
further.
The Series 7100-7200 electromagnetic flow transmitters manufactured by
Brooks are solid state flow rate sensing elements. A typical unit is
depicted in Figure A. They are designed to withstand tough service
applications such as corrosive, humid and dirty environmental condi-
tions, wide variations in temperatures, and high vibration loads. All
adjustments are precise and are made externally; once set, there is no
change. The three-electrode design is immune to changes in conduc-
tivity of the metered liquid. The transmitter utilizes an integral
FET type preamplifier (impedance converter) to provide a low impedance
output signal to permit long lengths of interconnecting cables without
186
-------
>, Figure A
regard to liquid conductivity or adverse effects of noise pickup.
Brooks-Mag transmitters, in conjunction with Brooks-Mag signal convert-
ers, provide output signals which are compatible with almost any manu-
facturer's secondary equipment. Electromagnetic transmitters and
signal converters are fully interchangeable and are adjusted and cali-
brated independently of each other. The transmitter uses a potentiom-
eter to adjust a reference voltage whose ratio to the signal voltage
is constant in all transmitters regardless of size, materials of con-
struction, and liquid being metered. Signal converters are always
adjusted to identical input values.
Standard meter sizes are from 0.25 cm (0.1 in.) to 1.2m (4 ft), and
units up to 2.4m (8 ft) are available on special order. Normal veloc-
ity ranges are 0 to 9 m/s (30 fps), and standard accuracy is ±0.5% of
full scale over the entire flow range. The design features a short
laying length; e.g., a 61-cm (24-in.) diameter meter is only 76 cm •
(30 in.) long. Type 304 stainless steel is the standard metering tube
187
-------
material, and various line materials such, as neoprene, gum rubber,
polyurethane, etc., are available. Among the units other design
features are:
• LOW POWER CONSUMPTION - yet has high signal-to-noise
ratio; can operate.empty with power on.
• LOW INSTALLATION COST - only a single conduit between
transmitter and signal converter.
• SEALED METER HOUSING - weather resistant-protects coils
which are mounted (for easy serviceability) on outside
of flow tube. Meets NEMA 4 specifications. Submersible
design optional.
• POSITIVE ZERO RETURN - optional zero level locking circuit
actuated by remote contact. Holds output signal at zero
flow rate value.
• UNAFFECTED BY CHANGES - in conductivity, temperature,
pressure, density, and viscosity.
• ADJUSTABLE FLOW RANGES - full scale deflection can be
easily set for any flow rate within the limits of the
transmitter.
• IMMUNITY TO STRAY VOLTAGES DUE TO UNIQUE ELECTRODE
BALANCE SYSTEM - eliminates the need for adjustments.
• LONG CABLE LENGTH - distance between transmitter and
signal converter is not limited by the conductivity of
the liquid.
• ELECTRODE CLEANERS - optional ultrasonic, or mechanical
scraper in only complete line of cleaners available.
Cleaners prevent accumulation of matter on transmitter
electrodes which could affect metering accuracy.
• PROTECTIVE SHIELD/GROUNDING RING - (optional) prevents
damage to meter lining materials when handling abrasive
and solids-bearing liquids.
Where it is not desired to time-share one signal converter with several
electromagnetic flow transmitters, Models 7700-7800 are available.
These models are essentially a Model 7100-7200 flow transmitter with
an integrally-mounted signal converter. Figure B depicts typical
configurations.
188
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189
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Secondary Devices
Signal Converters - Series 7300 Signal Converters are all solid state
instruments which, receive the electrical output signals that are
linear with flow rate. There are no servo motors, balancing slidewire,
or other components that can wear out. The Brooks Model 7300 Series
Signal Converter amplifies and converts the AC output signal from the
flowhead into a DC signal. Since the DC signal is directly propor-
tional to the liquid flow rate, it is used to drive a meter on the
signal converter that indicates percent of maximum flow. The DC signal
can be adjusted for various operating ranges, and can be used with in-
dicators, controllers, recorders, and systems that require direct
current inputs for operation.
The AC flow rate signal from the flowhead is coupled into an impedance
converter having an input impedance of- approximately 2000 Mohms. The
signal is amplified, converted to DC, and coupled to a divider. Simi-
larly, the reference voltage from the flowhead is converted to DC, ,
amplified, and coupled, in the proper sense, to the divider. A con-
stant DC multiplier signal (factory pre-set) is coupled to the divider
for scaling purposes. The specific function of the dividing feature
is to produce a ratio between the signal and reference voltages for
all specified flow rates. Fluctuations of primary power causes pro-
portional fluctuations of both signal and reference voltages. !There-
fore, by maintaining the ratio constant for a given flow rate, the
primary power fluctuations are ignored. The computed output signal is
then conditioned as required and transmitted to the users receiving
devices.
Series 7400 Signal Converters are all solid state devices which receive
the electrical outputs from Brooks electromagnetic flowmeters and con-
vert these outputs to useable electrical output signals that are linear
with flow rate. The signal converters are integrated units of modular
design capable of high system accuracy with a minimum of components.
The Brooks Model 7400 Series Signal Converter amplifies and converts
the AC output signal from the flowhead into a DC signal, or a pneumatic
signal. Since the signal is directly proportional to the liquid flow
rate, the meter on the signal converter directly indicates percent of
maximum flow. The output signal can be adjusted for various operating
ranges and can be used with indicators, controllers, recorders, and
systems that require DC or pneumatic inputs for operation.
The electrical output from the electrodes in the flowmeter is amplified
by a high impedance preamplifier. This signal is combined with a
reference signal and then fed to a servo,-amplifier which, in turn,
powers a servo-motor. The servo-motor drives a totally enclosed slide-
wire to achieve a "true null-balance by balancing a reference voltage
190
-------
(fed through the slidewire) against the signal voltage. In addition,
the servo-motor operates the pointer which indicates flow rate, and
also rotates the cam which actuates the pneumatic transmitter or
integrator.
Design features common to both the Series 7300 and 7400 signal con-
verters include:
• HIGH ACCURACY - Standard accuracy is ±0.5% full scale
output.
• COMPLETE INTERCHANGEABILITY - All units interchangeable
with each other and with other signal converters from
Brooks.
SUMMARY OF 7400-SERIES SIGNAL CONVERTERS
Model
Number
7410
7411*
7430
7431
7450
7460
7470
7475
7490
7495
Flowrate
Indicator Dial
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
READOUT
7-Digit '
Counter
-
-
Yes
-
-
-
Yes
Yes
'
Yes
Pneumatic
Signal Output •
-
-
-
-
Yes
- ,
Yes
-
-
-
Current
Voltage
Output
- -
-
-
-
-
Yes
-
Yes
-
-
Output
Resistance
: -
-
-
. - .
-
-
- •
-
Yes .
Yes
Telemetry
-
-
- •' '
Yes
-
-
-
-•'
::
-
8-1/2 inch 'indicator dial
LINE VOLTAGE COMPENSATION - Inherent compensation for line
voltage variations.
EMPTY PIPE ZERO - Output goes below zero when flowmeter
electrodes are not exposed to conductive liquid (standard).
191
-------
• MULTIPLEXING - One signal converter can be time shared with
several flowmeters.
• LEAD LENGTH - Signal is not affected by lead length.
• MINIMUM INSTALLATION COST - Only one conduit is required
between flowmeter and signal converter.
• MULTIPLE RANGE - Front-of-panel range selection available,
or ten-turn potentiometer mounted on printed circuit
board (optional).
• SERVICEABILITY - Chassis may be pulled out for inspection
without shutting down flow or interrupting output.
• MOUNTING - Cases available for flush panel, wall or pipe-
stand mounting. Cases available in standard, weather-
proof, or explosion proof construction.
Continuous Level Measurement and Control Systems - The Brooks "Maglink"
liquid level system was specially designed for use in pressurized tanks
or in open vessels in chemical service, where severe conditions of
corrosion, temperature, and pressure may occur. All parts in contact
with the liquid are made from stainless steel, plastic, or special
materials, thus enabling the equipment to be used for most applica-
tions in the chemical, food, and allied industries such as liquified
gases, acids, etc: The "Maglink" magnetic system has a sufficiently
strong coupling to withstand even the most severe fluctuations in
liquid level within the tank. The unit is schematically illustrated
in Figure C.
Any change in liquid level moves the float, which contains an annular
magnet. The float traverses a sealed guide tube. The flux linkage
between the float magnet and the tape magnet- within the tube transmits
the movement via the tape, to the indicating mechanism in the head.
Backlash in the indicator mechanism is completely eliminated by means
of a constant torque spring, which also serves as a take-up device for
the tape and compensates for the weight of the magnet. The density of
the liquid is accomodated by the range of floats available. Design
features of the unit include:
• Sealed system - for pressure or vacuum service
• Materials of construction for corrosive service
• High accuracy
• No calibration required
192
-------
Figure G
Remote transmission, pneumatic or electric
Good readability - 25.4 cm (10 in.) direct reading dial
Mechanical operation, inherently explosion proof
Unaffected by foam
Simple to operate and maintain
Operates on any liquid specific gravity
Interface measurement
Weatherproof case (standard for 25.4 cm dial only)
193
-------
• Typical float designs are as follows:
Dlomi
Inches
ter •
mm
Height
Inches 1 mm
Mln. Liquid
Density
in gm/cm^
Max
pre
PSIG
oper.
ssure
kg/cm2
Max.
tempe
°C
oper.
rature
°F
Float
Identification
Float Application
Floors in Stainless Steel
9-1/2
5-1/2
7-1/2
8-1/2
10-1/2
241
144
190
216
266
3
5
Floats in Polypropylene,
9-1/2
7-1/2
4-3/4
3-1/2
241
190
121
89
3
2-1/2
5-1/2
7
76
127
0.55
0.85
0.55
0.45
0.28
50
150
350
250
120
3.5
10.5
22.5
17.5
8.5
250
250
250
250
250
480
480
480
480
480
0
B
C
C
C
for standard use
for small branch entry
for medium pressures
same
same, and for low density liquids
Polyethylene, PVC
76
64
140
178
0.55
1.1
0.85
1.1
15
300
100
100
1.0
21.0
7
7
100
100
100
100
220
220
220
220
0
E
F
F
for standard u5_
solid-for high pressure applications
for small branch entry
same
Glow Float (Pyrex)
5-3/4
'146
7
178
0.68
Interface floats
6
7-1/2
152
190
2-3/4
2-1/2
70
64
See
note
45
200
300
3.2
250
480
14.0
21.0
100
100
220
220
G
E*
E**
For highly corrosive applications
for interface measurement with
adjustable weights
Minimum difference in liquid density 0.2 gm/cm^
• Stainless Steel ** Polypropylene, PVC, Polyethylene
I I Recommended float desii
gn
Standard floats are illustrated - special floats can be designed to suit more difficult applications.
194
-------
• Materials of Construction include:
316 SS, Polypropylene, PVC
Teflon-covered SS
316 SS, Polypropylene, PVC
Glass, Mbnel
Guide Tubes and
Mounting Flange - Std.:
Optional:
Floats - Std.:
Optional:
Cases - Die-cast Alum, (with transmitter or switch)
Rigid pplyurethane cover & fiberglass housing
(std.)
Ranges:
Dials - Any range from 0 to 2 ft (min.) to 0 to 36 ft (max.)
Tapehead - Any range from 0 to 2 ft (min.) to 0 to 16 ft (max.)
Scales:
Standard Graduated in ft., in., or mm.
Special Graduated in units of weight or volume
of material
Performance:
Sensitivity -
All units below 5.5m (18 ft) - float movement ±1.6 mm (1/16 in.)
All units 5.5 to 10.9m (18 to 36 ft) - float movement ±3.2 mm
(1/8 in.)
Accuracy -
±0.5% of max. indicated depth
PRICES: "-.'..;
"Brooks-Mag" Flowheads '
"Brooks-Mag" Signal Converters
"Maglink" Liquid Level Systems
COMMENTS:
$800-$17,000
$600-$12,000
$200-$1,200
Electromagnetic flowmeters were discussed generically in Section VI and
no further comment will be made here. The "Maglink" liquid level system
could find some application as a secondary device in conjunction with
flumes and weirs, especially in difficult sites. All Brooks equipment
outputs are computer-compatible either as standard design or srvailable
option.
195
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MANUFACTURER: CONTROLOTRON CORPORATION
176 CONTROL AVENUE
FARMENGDALE, L.I., NEW YORK 11735
TELEPHONE (516) 249-4400
PRODUCT LINE: ULTRASONIC FLOWMETERS
DESCRIPTION:
Controlotron Corporation manufactures the Series 240 clamp-on ultra-
sonic flowmeter consisting of both a primary clamp-on unit and a
secondary flow display computer and readout unit for use with pipe
sizes from 2.54 to 152.4 cm (1 to 60 in.) in diameter. The acoustic
technique employed is independent of liquid temperature, viscosity,
turbulence, etc. The simple clamp-on installation requires no calibra-
tion or cutting of metal and can be performed by non-technical person-
nel. The Series 240 transducer consists of a transmitter and receiver
unit positioned on opposite sides of the pipe. The transmitter, con-
trolled by the flow display computer, injects an ultrasonic sound beam
into the liquid through the pipe wall. The sound beam impinges on the
receiver after passing through the liquid and the pipe wall adjacent
to the receiver. If the liquid is flowing in the direction of the
sound beam, the apparent speed of sound in the liquid is increased
(or decreased if flowing opposite to the sound beam).
The pipe construction and the type liquid within determine whether or
not the Series 240 ultrasonic flowmeter is suitable for a particular
application. Controlotron will test 0.24& (8 oz) samples of the liquid
and samples of the pipe at no cost to the user to determine suitability.
Applications for which clamp-on models are not recommended by
Controlotron include pipes made of cast iron or any other material with
an irregular exterior or on pipes with linings that would attenuate
the acoustic signal. Insert transducers are used for this type of
service. These are similar to the transducers that are used for open
stream or channel measurement, and are made to order based upon the
application specifications. Controlotron does not recommend use of
ultrasonic velocity measurement devices in liquids that are high in
undissolved solids or gases, e.g., slurries of sand-like particles,
foams, or other aerated liquids, etc. Very rapid (less than 60 seconds)
changes in liquid characteristics (that would change its sonic velocity)
will result in temporary self-calibration failure and erroneous
readings.
SPECIFICATIONS:
Flow Range:
Resolution:
0-9.1 m/s (0-30 fps)
0.0015 m/s (0.005 fps)
196
-------
Accuracy:
Repeatibility:
Indication:
Outputs:
Power:
Dimensions:
Transducer -
Flow Display
Counter - 20.
PRICE:
COMMENTS:
From ±0,25% to ±2%, with ±1% of Full
Scale Reading nominal. Larger sizes
are more accurate, and Controlotron
will quote expected accuracy for a
given application.
±0.05%
Standard 3-1/2 Digits
Digital - BCD
Optional - Analog 0-10V, 4-20 mADC
Totalizer - 6 Digits ,
Alarm - Settable Hi and Lo Flow Alarms
115/230 VAC, 50-60 Hz, 75 watts'
L = Pipe O.D. + 15.24 cm (6 in.) (Approx)
- 25.4x33.0x38.1 cm (10x13x15 in.)
3x30.4x35.6 cm (8x12x14 in.)
Starts at approximately $2,000 for a
25.4 cm (1 in.) pipe. • -
The equipment is factory calibrated either with water or the intended
liquid, as appropriate. This is for fully developed flows with Reynolds
numbers exceeding 10,000. It can be calibrated for any flow including
laminar, and Controlotron reports that models with settable flow range
factors and tracking of flow profile through the laminar flow region
will soon be available. A zero offset adjustment may be required upon
installation. Experience in metering raw sewage with this equipment is
limited at this time and no definite statements about its suitability
can be made. The manufacturer is expanding its product line and adding
new features that may well increase the likelihood of their successful
use as flowmeters for storm and combined sewer discharges (but not in
the clamp-on configuration for most installations). An acoustic level
gage that could be used with a number of primary devices such as weirs
and flumes is also under development.
197
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MANUFACTURER:
PRODUCT LINE:
DESCRIPTION:
COX INSTRUMENT
DIVISION OF LYNCH CORPORATION
15300 FULLERTON
DETROIT, MICHIGAN 48227
TELEPHONE (313) 838-5780
VARIABLE AREA FLOWMETERS; TURBINE FLOWMETERS;
FLOW NOZZLES; FLOW INDICATORS
Devices
Cox Instrument has long been recognized as a manufacturer of preci-
sion flow measuring equipment, especially as related to fuel, oil,
gas, and industrial process fluid flows. The company proudly claims
that "over 95% of the world's commercially-built liquid flowmeter
calibrators now in use were designed and fabricated by Cox Instrument."
This includes one presently being used by the National Bureau of
Standards. Cox has also produced custom designs and systems for
special applications.
The company offers a wide line of variable-area flowmeters. Such de-
vices are not considered at all suitable for storm or combined sewer
applications and, hence, will not be discussed. Cox also has a very
wide line of turbine meters; capacities range from 0.00044 to 1770 £/s
(0.000016 to 62 cfs), with accuracies to 0.05% of reading available
and response times better than 50 milliseconds. One of these typical
turbine meters is shown in Figure A, which also indicates some of the
distinguishing features of a Cox turbine. Turbine flowmeters are not
considered suitable for most sewer flows and will not be discussed,
further.
Cox also makes a flowmeter called the VR-30 which, it is claimed,
presents a new concept to the field of industrial flow measurement.
It uses the principle of variable reluctance: a spring— loaded, force-
balance spool is displaced in a magnetic field by the force of fluid
flow. This changes the coupling in an external circuit. Because the
spool is displaced in a contoured cross— section, the square root is
extracted automatically, resulting in a linear output. The advantages
to this approach are bi-directional output; unrestricted mounting posi-
tion; in-line installation; and low maintenance operation. The VR-30
is said to handle corrosive, toxic, contaminated, or volatile fluids
or slurries, at pressures to 3,000 psi and temperatures to 121°C
(250°F). It is accurate to ±2% of full scale. Prices start at under
$300, complete with remote indicator. The VR-30 may also be purchased
with a more sophisticated readout device for analog and pulse output,
providing for continuous process control or direct computer input.
198
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Flow straightening design so
precise that additional
straightening is rarely necessary.
Pressure loss is insignificant.
Configuration of ro'tor blades is
designed to meet exactly the
requirements of meter and its
application ... providing high
response, accuracy, and linearity.
Hermetically sealed pickoff
provides a strong, high-frequency
output signal.
The lightweight rotor is the only
Amoving part... no register .
drives, no magnets. This design
provides faster response, more
accurate measurement,
and longer life.
Precision ball bearings allow the
'rotor to move freely and respond
quickly to flow variations.
Bearings are field replaceable
... no need to return entire
unit to factory. Different types
of ball bearings are used to
match the requirements of the
meter. Special sleeve bearings
of a variety of materials are
also available for heavy-duty
industrial applications.
Figure A
199
-------
This device may have some wastewater applications, but is not considered
well suited for most storm or combined sewer flow measurements. It
will not be discussed further.
Cox manufactures twenty standard sizes of flow nozzles (Figure B) in
two series with bore diameters ranging from 0.3 to 22.9 cm (0.128 to
9 in.). The standard approach to bore diameter ratio is 3:1, but the
—A-3
Figure B
larger sizes are available on request in a 2:1 ratio. Cox nozzles are
available either calibrated or uncalibrated. Nozzles are calibrated
by using a positive displacement prover tank, a standard "Master"
orifice, or both. Pressure differential across the nozzle is deter-
mined by using a micromanometer accurate to 0.005 cm (0.002 in.) of
water. Standard calibration is to within ±1<.0%. With calibrated
nozzles, a curve of "Differential Pressure versus Flow Rate" (based
on 14.7 psia and 70°F) is supplied with a copy of actual calibration
data and correction factor determinations. Calibration at other than
the standard condition noted can be obtained on special order. Flow
nozzles were thoroughly discussed in Section VI and will not be com-
mented on again here.
Secondary Devices
In addition to turbine meter signal conditions and displays, Cox manu-
factures a number of basic electronic modules for signal conditioning,
conversion, display, etc., that could be used as "building blocks" in
assembling a custom system. One such unit will be described as an
example, but such basic components lie outside the general scope of
this writing.
200
-------
Cox Variable Time Base FIB - Using integrated circuit (1C) techniques,
the P1B module provides signal conditioning of low level AC signals
for input to counters. The P1B may be used to increase the flexibility
of almost any counter currently made. It is not limited to Cox-built
equipment, and will interface with most major manufacturers' counters.
In addition to signal amplification and conditioning,' the P1B module
provides gate, reset, and display control of ancillary counters. The
variable time base (gate control) is a direct setting digital selector.
A four digit time base selector permits selection of 0.000-10.000 sec-
onds gating time in steps of 0.001 seconds. The time base affords an
easy means of displaying the frequency output of a transducer in direct
reading units (e.g., GPM, RPM) . The P1B may be used with Cox PSA coun
counter for the direct display of a frequency signal in engineering
units. Turbine meters produce a frequency proportional to flow-rate.
By preselecting appropriate gate time, the display is in GPM units.
Design features include:
• Advanced 1C design employed.
• TTL (transistor-transistor logic) assures superior noise
immunity.
• Designed for compatibility with pulse transducers present
or future.
• Standard high sensitivity (3 mV) eliminates need for inter-
mediate transducer amplification.
• Short circuit protection against both installation error
and ancillary equipment failure.
201
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MANUFACTURER: GUSHING ENGINEERING INC.
3364 COMMERCIAL AVENUE
NORTHBROOK, ILLINOIS 60062
TELEPHONE (312) 564-0500
PRODUCT LINE: ELECTROMAGNETIC WATER CURRENT METER
DESCRIPTION:
The Series 600 VELMETER, an electromagnetic water current device, is
designed to measure flow velocity in oceans, streams, rivers, estuaries,
aqueducts, sewers, etc. Operational features include no moving parts,
zero threshold, fast response times, cosine response, special noise
rejection circuitry, linear output, and anti-fouling coating.
The meter consists of a flow sensor connected to a signal converter by
means of a cable and is offered in several configurations. These in-
clude an explosion-proof housing, NEMA 4 (weatherproof) housing, port-
able housing, rack-mounted panel, and kit form for the converter unit;
60-Hz or battery power; flange connection (with No-Foul protection)
type sensor; or streamlined type sensor (for use when flow direction
is known).
The VELMETER sensor produces a flow-generated voltage of approximately
20 MV per 0.3 m/s (1 fps) of flow velocity. The sensor's electro-
magnet requires a (rms) constant current drive, which is provided by
the signal converter. The converter accepts the flow-generated voltage
from the sensor, amplifies it, and conditions it to produce a final
analog voltage output of ±5 volts for ± full scale flow. The converter
also conditions the signal to provide optimal filtering of spurious
wideband noise that is picked by the sensor (such as 60-Hz noises gen-
erated in waters near urban and industrial areas).
There are several sensors that can be used with this metering device.
The Series 501 sensor incorporates one pair of detection electrodes
and provides an output voltage proportional to the vector component of
flow perpendicular to both the line connecting the two electrodes and
to the axis of the sensor. The series 502 incorporates two pairs of
detection electrodes and provides two output voltages, measuring two
vector components of water flow. The series 81/82 sensors are,
respectively, single-component and two-component devices which produce
approximately six times the flow signal power of the Series 500 sensor;
this sensor is said to perform within specifications for flow velocity
up to 15.2 m/s (50 fps).
202
-------
SPECIFICATIONS:
Range:
Output Time Constant:
Maximum Error Band:
Span or linearity
Zero Offset
Random Noise, rms*
Series 500 sensor
Series 80 sensor
Series 80 sensor
with Magpower option
Full Scale, adjustable to 0.09, 0.30,
0.9, 3.0, or 9.14 m/s (0.3, 1, 3, 10,
or 30 fps)
Adjustable to 0.1, 0.3, 1, 3, or
10 seconds
CONVERTER MODEL NO.
611/612 631/632
±1 ±2
±0.01 ±0.05
0.006//T"
0.002//T"
0.001//T"
0.030//T"
0.010//T"
0.005//T"
UNITS
Percent of Full Scale
Feet per sec.ond
Feet per second
where T is the output
time constant in
seconds
* Apparent peak-to-peak noise on a recorder depends largely on chart speed; but
approximately, apparent peak-to-peak noise is 6 times rms. value.
PRICE: $2,000 - $3,000 depending upon configuration.
COMMENTS:
This device should find some use as an attended survey unit in its
portable configuration. Because of the obstruction to the flow
offered by the standard probe configuration, some ingenuity would
haveito be exercised in mounting if damage from debris in the flow
is to be avoided.
203
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MANUFACTURER: DANIEL INDUSTRIES, INC.
P.O. BOX 19097
HOUSTON, TEXAS 77024
TELEPHONE (713) 467-6000
PRODUCT LINE:
PRIMARY DEVICES - ORIFICE PLATES AND METERS, TURBINE METERS, FLOW
NOZZLES
SECONDARY DEVICES - DIFFERENTIAL PRESSURE TRANSDUCERS, TRANSMITTERS,
AND CONVERTERS, INDICATORS, AND TOTALIZERS (CALLED FLOW COMPUTERS)
DESCRIPTION:
%
Primary Devices
Daniel Industries, Inc. manufactures a full line of orifice plates and
flanges, orifice metering tubes, bored orifice flow sections, and
orifice fittings for line sizes varying from 0.6 cm (1/4 in.) to 1.5m
(4 ft) in diameter. Their "Senior" orifice fittings have a dual cham-
ber design (Figure A) that permits the orifice plate to be removed
from pressure lines safely and quickly; this facilitates regular in-
spection and maintenance. "Junior" orifice fittings and "Simplex"
orifice plate holders are made for application where line by-pass or
pressure shut-down is permitted. A large range of orifice flanges for
use where it is not necessary to make regular plate inspections is also
offered, as are orifice meter tubes and bored orifice flow sections for
use where greater accuracy is required.
Daniel manufactures a "PT" line of liquid turbine meters (Figure B) in
sizes from 1.3 cm (1/2 in.) to 61 cm (24 in.). These meters are
intended for use where highly accurate measurement of large liquid
volumes is required, e.g., custody transfer. Each meter can be fitted
for bi-directional flow. Normal (linear) flow ranges are around 10:1
and extended flow ranges are from around 15:1 to 40:1, depending upon
size.
Daniel also manufactures a full line of precision flow nozzles (ASME
long radius and ASME throat top) including flanged, weld-in, and
holding ring types in a wide variety of materials (Figure C). For
highest metering accuracy, a fully assembled flow nozzle and meter tube
is offered. Large volume custom meter stations and proving systems are
supplied in virtually any size and capacity.
204 '
-------
SIDE SECTIONAL VIEW
CLAMPING BAR
SEAL.NGBAR
T°P
UPPER CHAMBER
BLEED VALVE
UPPER PLATE CARRIER SHAFT
GREASE FITTING
EQUALIZER VALVE (NOT SHOWN)
SLIDE VALVE
LOWER PLATE CARRIER SHAFT
SLIDE VALVE OPERATING SHAFT
PLATE CARRIER (REMOVABLE)
PLATE SEAL
ORIFICE PLATE
TAPS & LOWER CHAMBER
Figure A
205
-------
FT" METERS
RIM
ROTOR
BLADE
ROTOR
Figure B
206
-------
FLANGED
FLOW NOZZLE
This type of nozzle has a flange on its upstream
end which is installed between pipe flanges to
hold the nozzle concentric with the inside of the
pipe. The nozzle flange can be furnished in any
series of facing (raised, ring-joint, etc.) specified.
WELD-IN
FLOW NOZZLE
.This nozzle has a machined tongue around its
greatest diameter which fits between beveled
ends of both an inlet and outlet pipe section.
The sections, with the nozzle in place, are firmly
clamped and/or tack-welded together in perfect
alignment before the finish weld is applied.
HOLDING RING
FLOW NOZZLE
This nozzle is another welding type for instal-
lation in pipe without flanges. The nozzle is
installed in a section of carefully selected and
internally bored pipe with the curved nozzle
inlet facing upstream. . .
Figure C
207
-------
Secondary Devices
Daniel supplies a wide range of differential pressure transducers,
transmitters, counters, and indicators and totalizers (called flow com-
puters) for use with all of its primary elements., A typical differen-
tial pressure flow computer might take a 4-20 mADC signal that is
proportional to pressure difference and convert this into: a visual
indication of flow rate on a front panel meter; a 4-20 mADC electrical
output that is proportional to flow rate; a visual, six-digit indica-
tion of totalized flow; and an electrical dry contact closure per each
totalizer advance. Flow rate recordings are not normally supplied,
but could be on special order. Similar outputs are available from
secondary elements for use with turbine meters.
COMMENTS:
Much of the Daniel product line was developed for the oil and gas
industry and is more typically suited for this application than for
measuring storm and combined sewer flows. There might be some uses
for their flow nozzles and orifice meters in measuring sewage flow,
but the turbine meter is not at all suitable. For this reason no
detailed specifications or prices will be given.
208
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MANUFACTURER:
DREXELBROOK ENGINEERING COMPANY
205 KEITH VALLEY ROAD
HORSHAM, PENNSYLVANIA 19044
TELEPHONE (215) 674-1234
PRODUCT LINE: LEVEL GAGES
DESCRIPTION:
Drexelbrook manufactures a wide line of secondary flow measuring and
indicating systems in their Series 508 (see Figure A). The Drexelbrook
"Cote Shield" flowmeters provide reliable and accurate measurement of
the flow of clean or dirty liquids through virtually any head-area
primary device such as flumes, weirs, etc. The flowmeters contain no
moving parts, floats, or air purge tubes; they cannot plug, and are
unaffected by coating of solids such as slush, mud, algae or slime,
build-up, paper, sludge, etc. The sensing element is static and can
be installed either directly in the moving stream or in a stilling
well.j.
The sensing element is basically a precision admittance-to-current
transducer. It will provide an output current directly proportional
to the input admittance presented by the sensing element. Each meas-
ured flow rate corresponds to a specific level in the weir or other
primary device. This variation in level will cause minute amounts of
current to flow from the sensing probe to the grounded stream. A com-
pensated bridge circuit is used to accurately measure the change in
current. The output of the bridge circuit is a DC voltage which is a
measure of the true flow rate. The output voltage is amplified in a
feedback amplifier to provide an output current directly proportional
to flow and unaffected by the output resistance. The output current
can be used to operate a variety of accessories such as remote meters,
recorders, alarm circuits, and electro-pneumatic transducers.
Drexelbrook has a number of the Series 508 models available both with
and without "cote-shield" action for clean or dirty liquids that vary
in calibrated immersion depth of the sensor probe from 30.5 to 91.5 cm
(12 to 36 in.). Standard systems are available for use with any 3/2-
or 5/2-power low head-area device (most commonly used with weirs and
flumes). Linear systems (e.g., for use with a sutro weir or Kennison
nozzle) are routinely made to order, and virtually any depth-discharge
characterization can be provided on special request. Both internally
and externally (shaped) characterized probes are available. For direct,
in-stream applications where damage due to large debris (floating logs,
rocks, etc.) is a possibility, Drexelbrook offers an optional tilt-away
mounting in which the probe is held in the flow by an adjustable counter-
weight but is free to pivot up out of the way when struck by an object
in the flow. This mounting is also recommended when extreme build-up
209
-------
EXTERNALLY
CHARACTERIZED
(SHAPED)
SENSING PROBE
INTERNALLY
CHARACTERIZED
SENSING PROBE
-6 1/4 *1
\i> 6| I—T
OPTIONAL REMOTE
OUTPUT
CURRENT
117 VOLTS
50/60 CYCLES
SERIES 508 FLOWFIETER
Figure A
210
-------
of fibrous materials such as rags and paper are expected.. As large
build-ups occur, the increased drag on the probe will cause it to tilt
up and allow the fibrous materials to wash away.
Optional integrators (totalizers), batch counters, remote readouts,
etc., are available as are such extras as lighted meter case, explosion
proof housings, special mountings including extra-long probes, etc.
SPECIFICATIONS;
Accuracy:
Standard Output Current Ranges:
Load Resistance Effect:
Power!
Direct function of primary device.
Flowmeter output is linear within
±0.5%.
4-20 mA thru 0 to 1500 ohms
1-5 mA thru 0 to 6000 ohms
10-50 mA thru 0 to 600 ohms
0.1% from 0 to maximum resistance
95 to 145V, 50/60 Hz with a ±0.5%
effect on accuracy for input voltage
changes ranging from 95 to 135 VAC.
DC operation optional.
PRICES:
Basic Series 508 Systems range from $553.00 to $1,371.00
COMMENTS:
These devices appear very well suited for use with various primary de-
vices to measure storm and combined sewer flows at many sites. They
are essentially factory calibrated, and only a few field adjustments
are necessary. It should be noted that the entire calibrated length
of the sensor is not available for accurate measurement of flow. For
example, for 3/2 power law probes, the liquid level should always lie
between 1/3 and 3/3 of the calibrated length. Thus, a 51-cm (20-in.)
maximum calibrated length sensor should not be used for heads greater
than 51 cm (20 in.) nor less than 15 cm (6 in.). An additional in-
teresting feature is that, based upon an application description,
Drexelbrook will quote on a guaranteed performance basis. If the
equipment does not perform within the quoted specifications, it may
be returned for free repair, replacement, or credit.
211
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MANUFACTURER:
EASTECH. INCORPORATED
2381 SOUTH CLINTON AVE.
SOUTH PLAINFIELD, NEW JERSEY
TELEPHONE: (201) 561-1000
07080
PRODUCT LINE: EDDY-SHEDDING PRIMARY DEVICES; TRANSMITTERS, FLOW
CONVERTERS, INDICATORS, TOTALIZERS
DESCRIPTION:
Eastech Incorporated makes the VS-21 series vortex shedding element for
the measurement of flows of gases, liquids, and slurries. Also offered
is a selection of secondary instrumentation including transmitters for
various applications, several flow converters, a digital rate indicator,
and a totalizer.
Flowmeters
The VS-21 digital flowmeter (patented under the trade name of VS-21 Flow
Transmitter) is the primary flow measuring device, and forms an inte-
gral part of various flow transmitters in the manufacturer's product
line - both "full pipe flow" type and insertion flow variety. In con-
junction with the transmitter and sensor elements, this device utilizes
the principle (or effect) of vortex eddy-shedding to measure the flow
velocity. The VS-21 generates pulse signals over very wide flow ranges
(up to 200:1) at a frequency proportional to the flow rate. It cur-
rently utilizes any one of four sensing techniques to measure flow.
Three of these techniques employ thermistors; the other makes use of a
"shuttle-ball" concept, in which a "captive" hollow nickel ball is
driven by the effect of vortex shedding.
In the thermistor techniques, an electrical current is passed through
the thermistor, heating it and making it responsive to the cooling ef-
fects of flew. The changes in flow velocity across the thermistor due
to vortex shedding result in changes in its temperature, thus resulting
in corresponding changes in its resistence. In the front face thermis-
tor technique (Figure A), two coated thermistors are bonded into the
front face of the flow element and operated differentially.
Figure A
212
-------
The vortex shedding behind the flow element affects the direction of
flow impinging on the front face, causing out-of-phase velocity vari-
ations at the two thermistors. This is the approach used by Eastech
for wastewater and slurry flow measurement applications.
The "central" thermistor technique (Figure B) utilizes a passage drilled
through the flow element. The generation of the vortices alternately on
either., side of the passage causes flow to move back and forth in the
passage and across a single, removable thermistor sensor assembly which
is mounted through one end of the flow element.
B.
xxxxxxxxxxxxxxxxx
THERMISTOR
SENSOR
^xxxxxxxx xxxx/xx/
Figure B
The external thermistor technique is similar to that of the central
sensor except that it is located in a passage external to the meter.
Figure C shows this arrangement.
Figure C
The shuttle-ball method (Figure D) employs vortex shedding to drive a
hollow nickel ball back and forth along the axis of the flow element.
The motion of the ball is detected by a magnetic pickup. The calibra-
tion factor of the meter depends only on the dimensions of the flow
element and the pipeline.
213
-------
^xxxxxxxxxxxx
NICKEL
SHUTTIE
BAIL
Figure D
Flow Transmitters
As indicated by Eastech, the transmitter models discussed below are the
ones recommended for wastewater and slurry applications.
The Model 2210 and 2220 flow transmitters have flanged, spool style
bodies and removable VS-21 flow elements. These devices feature two
front face thermistor sensors and an explosion-proof, close-coupled
solid-state amplifier. This amplifier (also incorporated in the
Model 2500/2600 series) is provided to increase signal amplitude prior
to its transmission to a flow converter which way be remotely located
up to 762m (2500 ft) away. As noted previously, the VS-21 generates
output pulse signals at frequencies linear with volumetric flow rate
over ranges up to 100:1 (200:1 optional). Basic line sizes are from
3.8 to 15.2 cm (1.5 to 6 in.). Other sizes are optional.
The Model 2510 flow transmitter also employs the front face thermistor
technique (Figure A) and has two wet-tap thermistors that can be re-
moved for inspection without interfering with the flow through the
device. The thermistors are mounted on removable shafts flush with
the face of the flow element. The transmitter may be connected with
flow converter instrumentation at distances up to 762m (2500 ft).
This model, especially recommended for use on slurries and liquids
containing significant amounts of clogging solids, is offered in line
sizes ranging from 20.3 to 91.4 cm (8 to 36 in.).
Models 2610, 2620, and 2630 are called "insertion flow" transmitters
but are actually velocity probes. These devices have a shrouded flow
element with front face thermistor sensors (see Figure A) mounted on
the end of a shaft passing through a sealed mounting flange. The fixed
model 2610* (Figure E) is used where the line pressure can be relieved
* Also offered is the adjustable model 2640. It is similar to the
2610 except insertion depth can be adjusted with the flow trans-
mitter installed.
214
-------
te
stated
rt £he fl°" transmitter from the line.
the manufacturer, the Insertion depth cannot be altered
c
the use of full pipeline meters, or where it is ecessary
remove the metering device for inspection or pipeline "paging"
transmitters may also be used to traverse across a pipeSnf ?o det2
mxne velocity profile and are suitable for use in
uSdTi^h fl W±th the fUU P±Pe fl°W transmitter^,
used with flow converters located up to 762m (2500
27-fcm
MODEL 2620
HOT TAP STYLE
away from the
MODEL 2610
FIXED STYLE
DIAMETER OF
HOLE OUT INTO
PIPELINE4 MAX,
" MIN,
METER C/L.
Figure E
215
-------
Flow Converters/Indicators
Eastech offers several flow converters for use with the VS-21 flow-
meter. These include Models 4100 and 4200 and the Model 44 digital
flow rate indicator. The 4100 is designed for stationary or over-the-
road applications, accepts signals from a VS-21 flow transmitter, and
provides a conditioned pulse output. Optional features include scaling
to engineering units, totalizers, and analog rate indicators.
Model 4200 is similar to the 4100 except that it provides field adjust-
able scaling to engineering units and can be panel mounted.
The Model 4400 displays flow rate in digital form. It has a small plug-
in module which permits direct reading in any desired engineering units,
SPECIFICATIONS:
Model 2210 and 2510 Transmitters
Repeatability:
Linearity:
Calibration Accuracy:
Pressure Loss:
Response Time:
Minimum Measurable Flow:
Flow Capacity:
Turn-Down Ratio:
Model 2600 Series Transmitters
Repeatability
Linearity:
±0.1% of reading, or better
±0.5% of reading (at pipe Reynolds
numbers of 10,000 and above)
±0.25%
0.4 atm at m/s (20 fps)
1 msec @ 500-Hz signal frequency
Corresponding to pipe Reynolds number
of 5,000
2.54 cm (1 in.)* - 302.8 &/s (80 gpm)
91.44 cm (36 in.)* - 340,650 A/s
(90,000 gpm)
10:1 & 100:1 (standard); up to
200:1 (optional)
±0.1% of reading or better
±2% of reading (at Reynolds" numbers
10,000 and above based on flow element
dimension of 5.1 or 10.2 cm (2 or
4 in.)
* Meter Size
216
-------
±1%
Negligible
Same as Models 2200/2500 series
Same as Models 2200/2500 series
Same as Models 2200/2500 series
5.1 and 10.2 cm (2 and - 4 in.)
diameter
Calibration Accuracy:
Pressure Loss:
Response Time:
Minimum Measurable Flow:
Turn-Down Ratio:
Element Size
PRICES:
Standard prices not available at the time of this writing.
COMMENTS:
There is necessarily an obstruction to the flow with all of these de-
vices, so their use does not seem appropriate where large trash and
debris are present in the flow. A well-conditioned flow is necessary
for accurate readings, and a minimum of 20 to 40 pipe diameters in
length of straight pipe (15 to 20 diameters if straightening vanes
are used) is required upstream of the meter and at least two pipe
diameters of straight pipe downstream. Gaskets upstream and near the
meter must not protrude into the flow.
217
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MANUFACTURER:
EDO CORPORATION
13-10 111TH STREET
COLLEGE POINT, NEW YORK 11356
TELEPHONE: (212) 445-6000
PRODUCT LINE: ACOUSTIC-DOPPLER FLOWMETERS; PROBES, RECORDERS
DESCRIPTION:
The EDO sonic flowmeter operates on the doppler shift principle and is
a further development of EDO's line of doppler current meters. The
basic parts of the flowmeter (acoustic prohe and receiver indicator)
are depicted in Figure A.
INDICATING
RECEIVER
^
DIRECTION
OF
FLOW
Figure A
An acoustic probe, containing two transducers, is positioned in the
flow. It is normally oriented to point upstream, although the probe
is actually bi-directional. One transducer projects an acoustic
signal, which is reflected by waterborne particles and disturbances.
The reflected signal, frequency shifted proportionally to the velocity
of the fluid, is received by the other transducer. An electrical
signal proportional to fluid velocity is converted to flow rate by
means of processing circuits contained in the indicating receiver.
The actual point of intersection of the two beams is one foot up-
stream from the probe, so that measurements are made in an undisturbed
region of the flow field. Because the processing circuits are not
218
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sensitive to amplitude variations, the flowmeter is immune to changes
in impurity concentration and peripheral noise.
Significant claims have been made for this device with respect to its
use in wastewater applications. These are:
•• The probe does not clog due to sediment or silt as, for
.. example, the pressure ports of various flowtubes;
• The probe does not accumulate undue grease on the sensors,
since they are located in a high-velocity region of the
flow;
• The probe can be easily wiped free of grease, rags, and
other materials because, of its cylindrical shape.
In addition to its applications to flow measurements in pipes, the EDO
flowmeter can be used for open-channel velocity measurements. The flow-
meter has been used in fresh water, salt water, raw sewage and sludge.
EDO provides flowmeters and accessory equipment for both portable use
and fixed installation. The model 763F is designed for fixed applica-
tions and model 763P is offered for portable uses.
Model 763F - The fixed flowmeter, with its automatic cleaning assembly,
is installed at a specific point in the flow system. The cost of an
EDO fixed flowmeter installation is essentially constant, regardless
of the pipe-diameter, whereas the cost of magmeters, Venturis, and
similar in-line meters tends to increase dramatically with pipe diam-
eter. Due to its ease of installation, the meter is particularly
suited to retrofit applications. If user requirements dictate, it can
be used in the interim period while an in-line meter is being repaired.
Fixed flowmeter configurations can be altered to meet specific plant
requirements. For example, receivers for two or more probes can be
packaged in a single receiver unit, and local indicators or totalizers
may be installed on the receiver panel.
An automatic wiping mechanism cleans the probe periodically by with-
drawing and reinserting it through wiping glands. The period .between
cleaning cycles is controllable and is set according to existing con-
ditions. The cleaning can be remotely actuated from a control panel,
if chart-recorded flow readings indicate the necessity.
The mechanism provides unattended operation and requires only routine
preventive maintenance every 6 months. No purging is required.
219
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Model 763P - The portable flowmeter is general plant instrumentation,
inserted and removed as required, for plant flow surveys, trouble-
shooting, evaluation of equipment, etc. Installation and insertion can
be made without interruption of flow. Except for physical dimensions
and weight, differences in the respective receiver/indicator configura-
tions, and the fact that it is not equipped with automatic wiping
mechanism, the portable flowmeter operates essentially the same as the
fixed unit.
SPECIFICATIONS:
Ins trumentat ion
Flow Range
Pipe Size
Accuracy
Acoustic Probe
Frequency
Power Output
Transducer Spacing
Transducer Angle
Length of Cable Probe
Size of Probes
Small
Large
PRICE:
0.03 - 4.57 m/s (0.1-15 fps)
15.24 - 243.84m (6-96 in.) dia
±1.5%
3.0 MHz ± .005%
1.3 watts
1.9 cm (0.75 in.)
20°
up to 152m (500 ft)
1.9x91.4 cm (3/4x36 in.)
5.1x182.8 cm (2x72 in.)
3.048m (120 in.) (with probe extended)
Model 763F (Probe, Wiper Assembly, Receiver, Chart Recorder, Totalizer)
. $ 9,345
$10,300
With Small Probe
With Large Probe
Model 763P (Indicating Receiver, one Large or Small Probe,
Cables) " ™ *
COMMENTS:
2,930
These devices are essentially velocity probes and, hence, knowledge of
flow velocity profiles is necessary in order to obtain flow discharge.
They would appear suitable for open channel as well as full pipe flow
220
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given certain constraints. The sensing probe necessarily presents an
obstacle to the flow and, in flows containing large trash or debris,
it might be physically damaged. Hence, its -use would seem inappropri-
ate in this case. Otherwise, the self-cleaning feature would appear
to be attractive and could allow its use in troublesome flows. These
units are fairly new on the market, and wastewater application data
are scant.
221
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MANUFACTURER: ENVIRONMENTAL MEASUREMENT SYSTEMS
A DIVISION OF WESMAR
905 DEXTER AVENUE NORTH
SEATTLE, WASHINGTON 98109
TELEPHONE (206) 285-1621
PRODUCT LINE: ULTRASONIC FLOW MONITOR
DESCRIPTION: s
Environmental Measurement Systems, a division of WESMAR (Western
Marine Electronics, Inc.), is now in production with their Ultrasonic
Flow Monitor, UFM-200, a completely packaged secondary device that
"ultrasonically" measures and records continuous liquid flow. The
UFM-200 (Figure A) is calibrated, prior to shipment, to the customer s
ULTRASONIC FLOW MONITOR
UFM-200
MEASURES AND RECORDS CONTINUOUS LIQUID FLOW
Figure A
flume or weir. There is no contact with material being measured (i.e.,
transducer is mounted over the weir or flume), since the system operates
on the "sonar-in-air" (echo-sounding) principle. The sonar beam gives
a constant transmission of the distance from the top level of the flow.
This interval is converted to a voltage which is converted to flow
rate and recorded, totalized, and displayed. The UFM-200 is a complete
system with electronics, total flow counter, water sample rate counter
(adjustable), recorder (strip chart), timer (duty cycle), and visual
linear readout meter.
The system has built-in circuitry that allows remote or portable in-
stallation through battery-powered operation. The total flow counter
222
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continuously displays the total amount of flow, in six digits, up to
1 billion gallons (3,785 billion liters); the permanent recorder records
the converted and calibrated flow output in gallons per minute on a
6.35-cm (2.5-in.) inkless strip chart at a speed of 2.5 cm (1 in.) per
hour.
SPECIFICATIONS:
Range:
Resolution:
Repeatability:
Linearity:
Output Signals:
Pulse Proportional to Flow:
Sensor Beam Pattern:
Remote Operation
(Electronics to Sensor
Separation):
Input Power:
Dimensions
Enclosure:
(JIG)
Weight:
Electronics:
Sensor:
PRICE:
Not available at time of writing. ,
COMMENTS: "
Some users have encountered difficulty due to echos (false signal re-
turns) when using these devices in manholes. Putting a plastic shield
around the transducer seems to solve the problem.
3m (10 ft) (maximum)
41 cm (16 in.) (minimum)
within 1%
within 1% .
within 1%
0 to 5 VDC (proportional to head)
0 to 5 VDC or 0 - 1 MADC (proportional
to flow)
1 pulse every 1,000 gallons
7° conical included angle
Up to 91.4m (300 ft)
110/220 VAC, 50 to 60 Hz,
10 watts (or ±12 VDC)
36x31x15 cm (14x12x6 in.)
15 kg (3 Ib)
1 Kg (2 Ib)
223
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MANUFACTURER:
PRODUCT LINE:
EPIC INC.
150 NASSAU STREET
SUITE 1430
NEW YORK, NEW YORK 10038
TELEPHONE: (212) 349-2470
CURRENT METERS, COUNTERS/INDICATORS, STAGE
MEASUREMENT DEVICES
DESCRIPTION:
Eoic Inc. is the U.S.-based outlet for precision instruments and ma-
chinery manufactured by the West German firm of A. Ott Kempten. Epic
and Ott offer a line of current (velocity) meters and a varied selec-
tion of secondary flow measurement devices, including counters,
recorders, and indicators and several stage measurement devices (e.g.,
water level recorders, point gage, and a "flowmeter"). Most of these
devices are designed primarily for measurement of water flows, but
several have found application in the wastewater field.
fluent (Velocity) Meters - Typical current meters in the Epic/Ott line
Include the Universal types 10.002 (C31), 10.200, and 10.300 Types
10 002 and 10.200 are similar in that they both produce signals gen-
erated by an impulse device actuated by a permanent magnet so that the
rotation of the propeller is not slowed down by a contact system; the
signals are totalized by an electromagnetic counter connected by cable
to a magnetic switch, mounted in the meter body. It has been reported
that the Type 10.002 (C31), shown in Figure A, has been used success-
fully (in conjunction with a specially-designed flow tube) by at least
one large municipal government in the measurement of effluent flows.
Types 10.002 (C31) and 10.200 are portable, battery-powered devices.
Type 10.300 is a permanent hydrometric flow measurement device. Unlike
the 10.002 and 10.200, this instrument permits a direct determination
of flow velocity and can be permanently installed. As do the other two
current meters, the 10.300 produces a signal voltage that is propor-
tional to water speed; this voltage can be read from an indicator in
m/s. Telemetry of the measurements is possible.
The type propeller used, and its diameter and pitch, is determined by
maximum flow velocity of the fluid into which it is placed. As shown
in the following table, there is a variety of propellers for several
applications ~ including oblique flows as well as straight flows.
A variety of methods for indicating and recording flow velocities is
available: direct Indication via a servo system (for precision remote
indication); four-digit digital readouts by a converter and readout
224
-------
Figure A
Propeller
Ref. No. for
ordering
10.001.030.4.4
10.001.027.4.4
10.001.028.4.4
10.001.029.4.4
10.001.031.4.2
Component propeller
up to 45° oblique flow
10.001.032.4.4
Component propeller
up to 15° oblique flow
Type No.
engravec
4
1
2
3
A
R
Propeller diameter
mm in.
80 3 5/32
125 4 59/64
125 4 59/64
125 4 59/64
100 3 121/128
100 3 121/128
Propeller pitch
m. . in.
0.125 '.4 59/64
0.250 9 54/64
0.500 19 11/16
1.000 39 3/8
0.120 4 29/40
0.240 9 9/20
Max. flow velocity of water
m/sec ft./sec
1.25 4.1
2.50 8.2
5.00 16.4
10.00 32.8
2.50 8.2
5.00 16.4
Starting
speed
m/sec
0.04
0.03
0.04
0.05
0.04
0.05
225
-------
device; continuous recording of flow velocity on a compensating recorder
Cespecially suitable for permanently installed velocity meters); and
recording of the measured value by a portable, battery-powered mini-
recorder (basically used with non-permanent meter installations).
Flowmeters - Epic offers the Type 22.001 "flowmeter" for indicating,
recording, and counting the discharge at measuring weirs or open chan-
nels and in unpressurized pipe lines. A venturi flume can be provided
with this -unit. A water level-recorder with an electrical output (0-
10 volts) is used as the measuring transmitter for the water level.
Various systems of level meters can be employed -- e.g., pressure level
gage, tube level gage, pressure level gage with transmitter-amplifier,
float-type level gage, etc. Figures B through F show some typical
applications of this meter. The Model 22.001 combines a direct read-
ing indicator, counter, and strip recorder within a single cabinet.
1. Metering with the pressure level gage
A pressure transmitter is fastened on the bottom of the measuring chan-
nel. The device operates as an inductive measuring value sender. The
mechanical part of the measuring value sender is a metal membrane.
The deformation of the metal membrane resulting from the pressure of
the water column standing over the sender is a function of the water
height H. This deformation which lies for the nominal range in the
magnitude of less than 0.2 mm is measured with an inductive measuring
transformer and, over corresponding electronics, converted into a
voltage of 5 volts for the nominal range.
Figure B
2. Tube level gage (.1)
In very muddy channels it is occasionally necessary, to clean the
pressure level gage. In this case, the tube level gage is especially
suitable. Here the inductive pressure transmitter is in the lower part
of a tube. The sender is designed in such a way as not to touch the
liquid of the measuring channel. For cleaning, the tube level gage is
simply taken out of the liquid. The measuring amplifier can be fixed
226
-------
directly at the tuba tn order to have available at the measuring point
a voltage for the level value of 0-10 volts. This tube level gage
design offers the advantage that the installation can be made in the
specific measuring channel without constructional modifications
Measuring
amplifier
10 V(H)
Transmitter.
Figure c
3. Tube level gage (II)
In this configuration, the pressure transmitter is mounted to a metal
foot which is anchored in the bottom of'the measuring channel. In this
way the transmitter is always flowed around by the liquid, thus avoiding
the risk of getting polluted by deposition of mud, etc. This level
TSi ^l^^einounted on a tube, which is arranged in the side wall
of the channel, (By bedding the tube into the side wall, any dis-
turbing effect to the flow conditions in the channel will be excluded.)
227
-------
; Measuring
amplifier
o —10V
T^
Transmitter
Figure D
4. Pressure level gage with transmitter amplifier
This gage is similar to the instrument described under item 1, but in
this cafe, the amplifier is directly attached to the transmitter At
the output, a voltage of 0 to 10V is released which corresponds to the
height of'the water level. This transmitter can serve as level meter
for the flowmeter, but it is also especially suited as a transmitter
for the level indication in large tanks.
228
-------
Transmitter -t-
amplifier
0 —10V(H)
i Figure E
5. Float-type level gage
In case where there is a float well existing at the measuring point,
the measurement of the water level H can also be effected by means of
a float-operated level gage. A potentiometer converts the water level
into an electrical signal and applies it to a measuring amplifier.
The output of this amplifier is a voltage proportional to the water
height H which is led on to a function print for the calculation of
the discharge quantity Q. The function print consists of electronic
units, so that a mechanical cam is not necessary for the determination
of the discharge volume.
Transmission line
0-*-10 V(H)
Measuring amplifier
Figure F
229
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Counters - Epic markets a variety of counters ranging from simple,
electromechanical devices to fairly complex digital counters and in-
dicators. Typical are the Type 12.000 (F4) Revolution Counter, the
Type Z100 counter, and the 12.150 Revolution Indicator. The three-
digit F4 counter (Ott 12.000) counts a maximum of 10 pulses per sec-
ond and is suited for operation with the Ott 10.002 (C31) current
meter, which generates a signal pulse at each revolution of its pro-
peller. Two 1.5-volt "D" size batteries serve as the power source and
allow up to 48 hours of continuous operation without battery replace-
ment. A stopwatch is used with this device.
The Z100 five-digit counter is capable of measuring the length of pulse
cycles from voltage-free transmitters (e.g., current meters), up to a
maximum of 20 pulses per second. It is powered by six 1.5-volt single
cell batteries, sufficient for about 30 hours of operation, at a rate
of eight hours of daily operation.
The 12.150 (F10) revolution indicator provides direct reading of pro-
peller revolutions per second. It features three measuring ranges and
has a built-in accumulator with battery charger which can be plugged
into a 110/220 VAC power source. The counter is suitable only for
measurements where propeller revolutions are at least 1 per second.
Water Level Recorders '- Epic offers several water level recorders for
use with the Type 22.001 flowmeter as well as with other types of^meas-
uring devices. Following is a description of several typical devices.
The Model 20.100(X) is a horizontal water level recorder for continuous
recording of water levels in still and flowing waters. Drum rotation
periods are 24 hours, 8 days, and 32 days.
The Model 21.001 transmitter and 21.356 receiver are remote-controlled
water level recorders. The transmitter has an impulse sequencing relay
action for telemetering water level data over short and long distances.
The receiver is for use with two transmitters, with indication of the
water levels and their difference as well as recording of two water
levels.
Other models include a 20.250 (R16) vertical water level recorder
especially suitable for ground water measurements, and a 20.300(XX)
strip chart water level recorder for continuous recording.
Gages - Gages include the Model 24.000 point gage which comes with or
without an optical indicator. This device provides exact determination
of water levels by means of a pinpoint with reading accuracies of
1/10 mm, 1/1000 ft, or 1/100 inch.
230
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SPECIFICATIONS:
Current Meter (Typical) - Model 10.300
Starting Speed:
Measurement Accuracy:
Propeller Speed, Maximum:
Remote Transmission of
Measured Values:
Dimensions:
Body
Length (complete with
propeller)
Weight:
0.035 and 0.045 m/sec
(.114 and .148 fps)
±1.5% (from start of meter up to
0.2 m/s)
±0.5% (0.2 m/s and more linearity
error)
720 rpm . "..
possible up to 10km
4 cm (1.57 in.)
22.2 cm (8.74 in.)
No data on 10.300. Weights of other
models range from 2.7 to 9.1 kg (6 to
20 Ib).
Counter (Typical) - Z100 Counter
Input:
Measuring Range:
Longitudinal line resistance of meas-
uring cable: 200 ohms (max.)
Cross resistance of measuring cable:
1.5 kphm (min.)
Load of signal transmitter: 10 mA
(max.)
Input pulse recurrence frequency:
20 pulses/sec (max.)
(a) Preset time. The. measuring time
can be preset 0.1 sec ...999.9 sec
adjustable in steps of 0.1 sec
(b) Preset count. The number of
pulses can be preset 1 ... 9.999
Range of time measuring
0.1 sec ... 99.999.9 sec
231
-------
Measuring Accuracy:
Dimensions:
Weight:
(a) Preset time. Measuring time
inaccuracy: +0.1 sec (max.).
Error caused by measuring proce-
dure: max. -1 pulse
(b) Preset count. Error in length of
time: ±0.1 sec (max.). Error
caused by measuring procedure: 0
14x12.7x16 cm (5.5x5.0x6.3 in.)
(without operating elements and plugs)
2.9 kg (6.38 Ibs)
T?1 n«mieter/Water Level Meters (Typical!
Measuring Range of Water Level:
Relative Error for Water Level:
Possible Shapes of Measuring
Channel:
Error of the Water
Level (H) - Discharge
Quantity (Q) Function
(in Transmitter):
Total Error for Discharge
Quantity Output:
Output Voltage for Water Level:
Output Voltage for Q-Output:
Output Current for Q-Output:
Power:
PRICES:
Current Meters
0-30 cm (11.8 in.)
0-100 cm (39.4 in.)
0-150 cm (59.1 in.)
0-300 cm (118.1 in.)
0.5%
rectangular; triangular; round;
venturi-channel
±0.3%
0-10V (nominal range)
0-10V (nominal range)
0-10V (nominal range)
0-20 mA (0-500 ohms)
220 VAC, 40-60 Hz
10.002-
10.200-
10.300-
$1,350-1,600
$825.00
$870.00
232
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Counters
Z100--
COMMENTS
— $200.00
— $925.00
element current meters were thoroughly discussed in Section VI
not be commented upon here.
233
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MANUFACTURER:
FISCHER & PORTER CO.
WARMINISTER, PENNSYLVANIA 18974
TELEPHONE (215) 675-6000
PRODUCT LINE:
PRIMARY DEVICES - MAGNETIC FLOWMETERS, FLOW TUBES, FLOAT-ACTUATED
FLOWMETERS, PITOT TYPE MAGNETIC FLOWMETERS, PARSHALL FLUMES, AND
SLUDGE FLOWMETERING SYSTEMS
SECONDARY DEVICES - ELECTRONIC TRANSMITTERS (BELLOWS AND MERCURY-
ACTUATED) , SIGNAL CONVERTERS, ELECTRONIC RECORDERS, AND INDICATORS.
DESCRIPTION:
The Fischer and Porter Company offers a broad and diversified line of
products for use in various flow measurement applications in the water
and wastewater field. The company manufactures a number of different
types of flowmeters and flow tubes, as well as a plastic Parshall flume
and various signal converters. The company also markets a flowmeterxng
system specifically designed and constructed to continuously measure
the flow of sludge. Figure A depicts some typical installations ot
primary flow measuring devices.
Flowmeters - The type 10F1272 stilling well, float-actuated flowmeter
measures flow rate in terms of the stage in flumes, weirs, and other
head-area devices. The flowmeter converts vertical changes ot ±loat
position into corresponding units of liquid flow. The float cable
from which the float is suspended is wound on a drum inside the instru-
ment As the float rises and falls with changes in the liquid level,
the float cable winds or unwinds from the drum, causing the drum to
rotate. The position of the drum reflects the measurement of the liquid
level. The measurement is translated into the desired functxonal motion
for recording, indicating, or integrating through mechanical linkages
to a characterized cam attached to the drum. When the flowmeter xs
equipped with an electric vacuum, or pneumatic transmitter, the measured
value can be transmitted as a linear or non-linear signal for remote xn-
dicating, recording, or integrating.
The Types 10F1275 and 10F1276 are in-stream, float-actuated instruments
that measure the flow rate in terms of the head produced by Parshall
flumes, rectangular weirs, or other flumes where head to the 3/2 power
is proportional to flow (Type 10F1275), or by triangular weirs
(Type 10F1276). The flowmeters transmit an electric txme-pulse or UL
milliamp signal proportional to the flow to receivers that indicate,
record, or integrate the value. These flowmeters are of submersxble
construction and can be equipped with specially-constructed transmitters
for operation in hazardous locations.
234
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TYPICAL INSTALLATION WITH TRIANGULAR WEIR
TYPICAL INSTALLATION WITH PARSHALL FLUME
Figure A
235
-------
The Pitot-type (probe) magnetic flowmeter (10F1430 serxes) , shown in
Fiaure B, is designed especially for use in water and sewage. It
SSSes the Fischer & Porter unique, characterized field princxple of
electromagnetic induction to produce an AC signal directly proportxoned
S^TSS rate. Using this device, liquid flows can be measured xn
large rectangular, circular, or irregularly shaped pipes. It is to be
noted that 1? is strictly a velocity-sensing device, and measures only
SLe^S^^
i* S.^£-i^Ti23rS &1¥j
the end of a support suspension. The smallest recommended pipe line
size^or the insertion of the flowmeter is slightly less than one meter
(36 in?). In optional feature of this flowmeter is its bi-directional
flow measurement capability.
Another flowmeter in the Fischer & Porter line is the Short Form
Saracterized Coil (SFCC) Design Model 10D1430A (Figure C) . This
electromagnetic measuring device operates on the same prxncxple as the
Pitot-type Model 10F1430. The SFCC meter differs from conventxonal
electromagnetic flowmeters in that it uses a light weight coil encased
within the liner of a metering tube instead of a heavy external field
coil. Meter sizes range from 7.62 to 243 cm (3 to 96 in.) and ^xgh
from 43 to 2,268 kg (95 to 5000 Ibs) . Designed for Ixquxds, the meter
is reported to be unaffected by density or viscosity or by normal up-
stream or downstream piping configurations. In addition, electrode
cleaning is available upon request for both standard and accidental
submersed ("splashproof") designs. The meter can be mounted in any
aSude (although vertical is recommended) in the pipeline. The manu-
facturer slates categorically that full pipe flow conditions must exxst
in order for the meter to obtain accurate measurements.
Fischer and Porter also manufacture long form magnetic flowmeters
(Type 10D1416A), which have been in produttion for almost 20 years.
The? are available in sizes from 15 to 61 cm (6 to 24 in.) as standard
and may \Hrdered in sizes up to 198 cm (78 in.), but the SFCC desxgn
is recommended for the larger sizes. This type has been in servxce so
long that it serves as a dimensional standard in many plant-layout
specifications and guides.
Common features of all Fischer and Porter magnetic flowmeters
very high accuracy, very stable operation, extremely sensitive operation
Tc2 measure liquid flow with conductivities as low as 0.1 mxcromho per
centimeter), and direct digital computer compatibility. Electrodes
are field replaceable- with no loss in accuracy and no need for
r ecalib rat ion .
236
-------
Figure B
237
-------
METER TERMINAL BOX
CALIBRATION COMPONENTS
(EPOXY POTTED)
SIGNAL INTERCONNECTION
TERMINAL BLOCK
CONDUIT SEAL
ASSEMBLY (3)
INSULATING PIPE LINER
METER ELECTRODE (2)
-MAGNET COILS
-EPOXY POTTING COMPOUND
-METAL METER BODY
G! 1312
c
Figure C
238
-------
Parshall Plastic Flume - The Type 10F1940 Parshall flume is a one-piece
plastic -unit designed for the metering of liquids in open channels.
Because of its unbroken flow lines which present no obstructions to
cause build-ups of debris, the flume is particularly well suited to the
measurement of liquids containing settleable solids. The F&P flume is
available in various standard throat widths ranging from 2.54* cm (1 in.)
to 3m (10 ft). The flume is constructed of corrosion-resistant, light-
weight molded fiberglass reinforced polyester with integral stiffening
ribs to make the unit self-supporting and eliminate external bracing.
Options include integral stilling wells and staff gages.
, Flow Tubes - Fischer and Porter Series 10F1070 cast iron flanged flow
tubes (Figure D) are differential-pressure producing, primary metering
devices of a proprietary design which, it is claimed, produce a high
differential with minimum head loss (2-4%). Tubes are available for
nominal line sizes from 10.2 to 61.0 cm (4 to 24 in.). Four standard
throat sizes can be provided in each line size. The tubes are con-
structed of high tensile cast iron with the throat sections available
in bronze or s.tainless steel.
The 10F1060 plastic insert type flow tubes (Figure E) contain outlet
cones constructed of polyester plastic, reinforced with 30 percent
fiberglass by weight and throats of either bronze or stainless steel.
Tubes are available for nominal line sizes from 10.2 to 91.4 cm (4 to
36 in.). Four standard throat sizes can be provided in each line size.
Sludge Flowmetering Systems - The patented Fischer & Porter Model
10D1416/18C(s) Magnetic Flowmeter is designed to continuously measure
the flow of sludge. This design uses the electromagnetic induction
field of the flowmeter coils to produce an eddy current effect in the
aluminum metering tube. The eddy currents produce continuous heating
within the tube while. _simultaneously transferring the heat through a
"process-wetted" liner to prevent sludge and grease buildup. To com-
plement this capability and provide greater accuracy of measurements,
the manufacturer recommends the use of an optional feature - an ultra-
sonic electrode cleaning device. The output signal from the
Model 10D1416/18C flowmeter, representing sludge flowrate, can be re-
ceived by either a 51-1100DC series circular chart electronic recorder
or indicator, or a 50ED4000 or 50SF2000 series signal converter.
Flow Transmitters - The Fischer and Porter flow transmitters,
Types 1451RB and 1453RB, are bellows-actuated instruments designed to
produce a 4 to 20 mADC linear signal proportional to changes in rate
of flow through differential producers. The differential pressure is
detected at the metallic bellows pf the transmitter which uses mineral
oil as a fill fluid. A torque tube assembly within the meter housing
responds to differential pressure changes and its movement is trans-
mitted by an operating spindle to a linear variable differential
239
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Figure D
HIGH PRESSURE TAP
PRESSURE TAP
Figure E
240
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transformer (LVDT). The output of the LVDT is received by solid state
electronic circuitry for extraction of the square root function of the
differential to produce an instrument output signal proportional to
flow. ..
The Type 1451RE and 1453 flow transmitters are mercury manometer-
operated instruments which produce a signal similar to that of the
bellows-operated transmitter. However, the differential pressure is
detected at the mercury-filled wells of the transmitter. A float in
the low pressure well responds to the mercury level changes and its
movement is transmitted by an operating spindle to a LVDT as is done
in the bellows-actuated transmitter.
Signal Converters - The 50SF2000 Series magnetic flowmeter signal con-
verter is a completely solid-state unit with integrated circuitry.
The Converter is capable of receiving a low level AC signal either
directly from an F&P magnetic flowmeter or indirectly via an F&P low
conductivity preamplifier. This signal can be converted into an analog
DC current, a high-frequency pulse, or a low-frequency scaled pulse.
The converter is suitable for pipe or wall mounting, and as such, can
be provided with a flow rate meter and seven digit counter. Features
include automatic dual range, adjustable damping, and continuous and
automatic quadrature rejection.
Circular-Chart Electronic Recorder or Indicator - The Type 51-1102DC
circular chart recorder or the 51-1101DC segmental indicator complete
with an in-case "Mag/I" Converter is designed to receive the flow signal
from various Fischer and Porter magnetic flowmeters or from the F&P low
conductivity preamplifier. The instrument is a solid-state, null-
balance, servo-operated potentiometer that uses a unique driving motor
called a "TORQ-ER" and a contactless feedback element called a "flux
bridge". Either instrument is capable of receiving one or two process
variable inputs. Optional controllers, integrators, or transmitters
can be included within the instrument case., Fischer and Porter also
manufacture many other primary devices (e.g., turbine meters) and sec-
ondary devices (transmitters, receivers, transducers, relays) in both
pneumatic and electronic form.
SPECIFICATIONS:
Type 10F1272 Float Actuated Flowmeter
Operating Limits;
Accuracy:
Between 10.16 cm (4 in.) and 76.2 cm
(30 in.) of head at maximum travel
Float travel is within ±0.15 cm
(1/16 in.) of actual liquid travel
241
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Power:
Dimensions:
Weight:
Range:
120 VAC, 60 Hz, Single Phase
Varies according to configuration used
and customer requirements
40.5 kg (90 Ibs)
Types 10F1275 and 10F1276 In-Stream Flowmeters
Output:
Accuracy:
Power:
Dimensions:
Weight:
Type 101*1275: Can be used on flumes
7.62-305 cm (3-120 in.) wide and on
rectangular weirs 30.5-305 cm (12-
120 in.) wide.
Type 10F1275A; Can be used for head
ranges from 0-15.24 cm (0-6 in.) and
0-40.1 cm (0-15 in.).
Type 10F1275B: For head ranges from
0-30.5 cm (0-12 in.) and 0-76.2 cm
(0-30 in.).
Type 10F1276: For triangular weirs,
Type 10F76A covers head ranges from
0- to 25.40 cm (0-10 in.) and 0 to
45.7 cm (0-18 in.).
Electric Time Pulse - DC pulses on
leased or private pair.
Electric DC Milliamp Signal - 4 to
20 mADC over two-wire line.
±20% over 2:1 range (standard)
120 VAC, 60 Hz, Single Phase
Varies according to configuration used
and customer requirements
13.5 kg (30 Ibs)
10F1430 Series Pitot-Type Magnetic Flowmeter
Accuracy:
Repeatability:
Output:
Signal
±1% for max flow velocity of 0.91 to
9.42 m/s (3 to 31 fps) or ±2% for max
flow velocity of 0.30 to 0.91 m/s
(1 to 3 fps) ?
0.5% of full scale
50 or 60 Hz AC, approx 0.2 millivolts
(rms) per foot (30 cm) per second.
242
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Reference
Power:
Dimensions:
50 or 60 Hz AC, approx 5 to 6V rms
117 VAC, ±10%, 50 or 60 Hz
Meter - 25.4 cm (10 in.) nominal
inside diameter
Support Suspension Length:
4.5m (15 ft) maximum; 0.3m (1 ft)
minimum
SFCC Model 10D1430A Flowmeter
Accuracy (including readout):
Repeatability: ...
Power:
Dimensions and Weight:
±1% Full Scale, 0.91 - 9.37 m/s (3-
31 fps)
±2% Full Scale, 0.30 - 0.91 m/s (1-
3 fps)
±0.5% of Full Scale
117 VAC ±10%, 50 or 60 Hz, 17-910 watts
(depending on meter size).
Refer to preceding description of this
flowmeter
Type 1011940 Plastic Parshall Flume
Free Flow Discharge:
Max Head:
0.38 to 130 MLD (0.1 to 494 MGD)
20.3, 25.4, 45.7, 63.5 and 76.2 cm
(8,10,18,25, and 30 in.)
Weight: 11.25 to 1350 kg (25 to 3000 Ibs).
10F1060 Series Plastic Insert Flow Tubes
Accuracy: -Within 1% of rate (uncalibrated tubes)
Within ±0.5% of rate (calibrated tubes)
Types 1451RB and 1453KB Bellows-Actuated
Electronic Flow Transmitter,
Range: ( 5:1 (20% to 100% of max flow rate)
Accuracy: ±0.50% of max flow rate (Standard);
±1.0% of actual flow rate (optional)
Input: Differential pressure from flow through
a differential producer. Bellows
sensing element available in ranges of
0.5m (20 in.)
243
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Output:
Power:
Temperature:
Power:
4-20 mADC into 0-750 ohms.
120 VAC ±10%, 50/60 Hz or 24 VDC
4° to 52°C (40° to 125°F)
120 VAC ±10%, 50/60 Hz or 24 VDC
Series 50SF2000 Signal Converter for
Magnetic Fldwmeters
Input Signal:
Output:
Electric Analog
Dual Range Selection
Accuracies:
Repeatability;
Response Time:
Power:
From any F&P Magnetic Flowmeter.
4-20 mADC into 0-1000 ohms (0-16 mADC
optional)
10-50 mADC into 0-400 ohms (0-40 mADC
optional)
Ranges are fixed for ratios of 2:1,
4:1, 6:1, 8:1 and 10:1. Range is to
be specified when ordering. Lowest
full scale value is 0.9 m/s (3 fps).
(including flow transmitter); Analog
and/or pulse - ±1/2% full scale 0.9 to
9.3 m/s (3 to 31 fps); ±1% of full
scale from .03 to 0.9 m/s (0.1 to
3 fps).
0.25% of full scale.
Digital: 1 second
Analog: 1 to 80 seconds, adjustable.
(10 seconds standard)
117 VAC ±10%, 50 or 60 Hz ±5%,
12 watts (max) @15 VA
Type 51-1100DC Circular Chart Electronic
Recorder or Indicator for Magnetic
Flowmeters
Inputs:
Output:
Analog
Unsealed Pulse
Accepts signals from all F&P Magnetic
Flowmeters
4-20 mADC into 750 ohms or 10
10-50 mADC into 300 ohms external load,
10 kHz, 15 VDC, 8 microsec pulse width
into 2000 ohms or greater.
244
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Accuracy:
Repeatability:
Temperature:
Power:
Weight:
±0,5% of full scale for analog and
pulse outputs on all models including
single and dual ranges.
0.2% of span
4° to 52°C (40° to 125°F)
120 VAC ±10%, 50-60 Hz ±5%, 45 watts
Approximately 18,6 kg (40 Ibs) for
single pen unit.
245
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MANUFACTURER: CARL FISHER AND COMPANY
DIVISION OF FOKMULABS, INC.
529 WEST FOURTH AVENUE
P. 0. BOX 1056
ESCONDIDO, CALIFORNIA 92025
TELEPHONE (714) 745-6423
PRODUCT LINE: FLUORESCENT DYES
DESCRIPTION:
This company has long been active in the chemistry of color and produces
a number of fluorescent dyes that can be used as tracers in either color-
velocity or chemical dilution flow studies. Two colors are standard;
fluorescent red (maximum absorbance point on a spectrophotometer is ap-
proximately 558 my) which is more commonly used, especially if the water
contains some yellow, and fluorescent yellow/green (maximum absorbance
point on a spectrophotometer is approximately 494 my) which is recom-
mended for use when the water contains large quantities of silt.
The dyes appear to be non-toxic in the levels used for flow measurement.
For example, the FDA has established a level of daily ingestion of
0.75 mg per day for fluorescent red. Considering the normal human daily
consumption of water this would equal approximately 370 parts per bil-
lion, at which concentration the water would have a bright fluorescent
red color. Instrumental detection limits are around 1 part per billion.
The fluorescent dyes are available in a number of solid forms including
tablets (2.5 gm), cakes (55 gm), donuts (0.33-1,17 kg), and logs 7.6 cm
(3 in.) diameter and up to 1.2m (4 ft) long (8.6 kg).
PRICES:
Tablets
cakes
donuts (small)
donuts (large)
logs
$0.07 each (2,600 quantity orders)
0.90 each (5,000 quantity orders)
4.75 each
10.00 each
24.00 per foot
COMMENTS:
These dyes appear suitable for a number of storm or combined sewer flow
studies. The manufacturer will offer specific information on such
applications upon request.
246
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MANUFACTURER:
PRODUCT LINE:
DESCRIPTION:
TECHNOLOGY, INC, . ' .,
4250 EAST BROADWAY ROAD
PHOENIX, ARIZONA 85040
TELEPHONE (602) 268-8776
TURBINE FLOWMETERS OF VARIOUS CONFIGURATIONS PLUS A
COMPLETE LINE OF SECONDARY INSTRUMENTATION INCLUDING
SIGNAL CONDITIONERS, PULSE RATE CONVERTERS, FLOW RATE
MONITORS, ETC.
Flow Technology, Inc. manufactures "standard line" axial-turbine flow-
meters in sizes from* 0.6 cm (1/4 in.) to 0.6m (2 ft) with standard
ranges of 10:1 which can be extended to as much as 250:1 in some cases.
They also manufacture a tangentially-driven turbine, the "omniflow"
which is capable of measuring extremely low flow rates. Neither of
these appears suitable for wastewater applications, and they will not
be described further..•'....
Flow Technology manufactures point velocity sensing elements called
"Turbo-Probes". The "Turbo-Probe" family of turbine flow transducers
utilizes a small axial-flow turbine sensing element positioned in the
flow stream of a large duct, pipe, or channel by means of a strut.
The sensing element is a small, freely-suspended turbine flowmeter
unit within its own open-ended cylindrical capsule. As this turbine
turns under the force of the flowing fluids, its rotation produces a
series of electrical pulses in a pickoff located in the strut. The
pulse rate or frequency of this electrical signal is directly pro-
portional to the velocity of the fluid passing through the'capsule.
This pulse output can be fed to appropriate electronics to count,
totalize, or display the flow velocity of rate in various engineering
terms - feet per minute, gallons per minute, meters per second, cubic
meters per hour, etc. This output can also interface with industrial
process control systems or on-line computers. This family of flow-
meters has found applications both as portable insertion probes and as
permanently-instailed units. Figure A depicts a typical configuration.
An outstanding feature of the "Turbo-Probe" series is the economy
achieved when it is necessary to make flow measurements in pipes,:ducts,
or channels of very large size. The exorbitant cost of full-bore tur-
bine flowmeters far outweigh their favorable high-accuracy charac-
teristics in such applications. The response of such large
turbines can be low because of the high mass of the rotors. However,
in such applications, a "Turbo-Probe" installation with its small tur-
bine can result in considerable cost savings at little sacrifice of
accuracy and considerable gain in response. If the velocity profile
in the flow channel is known, the fluid velocity data can be directly
247
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related to flow volume. Absolute volumetric flow accuracies of
+0.5 percent have been achieved. The accuracy of velocity measure-
ments are on the order of ±0.25% under field conditions.
Figure A
"Turbo-Probe" units can be fabricated from a wide variety of materials
capable of withstanding the most difficult industrial environments. A^
retractable version of this flow velocity sensor called "Retracto-Line"
is also offered for use in large diameter pipelines.
Secondary Elements - Model LFP-200 is a low flow, offset signal condi-
tioner. Turbine flowmeters designed for low flow rates exhibit a linear
frequency output as a function of flow rate, but also exhibit a zero
offset that appears as a non-linearity with a standard flow rate monitor
or flow totalizer. Flowmeters designed for higher flow rates also
exhibit this zero offset characteristic when there is an increase in
the viscosity of the fluid being measured or when the flow range is
extended below the normal minimum for the particular design.
The LFO-200 is designed to correct this zero offset by injecting into
the flowmeter output pulse signal a predetermined frequency - dependent
upon the design of the flowmeter - that allows the flow-versus-frequency
characteristic curve to intersect the zero point, thus eliminating the
zero offset. Because turbine flowmeters have a minimum flow rate and
do not respond down to zero flow rate - there is a point where flow
248
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exists hut the turbine rotor stops or becomes highly non-linear in its
rotation - the LFO-200 incorporates a circuit to cut off the frequency
output at a predetermined minimum output frequency. Because of the cut-
off feature, there is no output from the LFO-200 when the rotor is
turning below a given rate or when the rotor is stopped. The LFO-200
therefore increases the accuracy of low flow indications and permits
the use of less-expensive frequency-to-analog flow rate monitors and
flow totalizers. The LFO-200 is a solid-state unit normally packaged
in a heavy-duty steel JIG box with input, output, and power supply con-
nections made through MS.-type connectors. Other types of enclosures
and connectors are available on special order.
Model LFA-300 is a range extending amplifier. Turbine flowmeters with
normal pickoffs experience a magnetically-induced drag on the turbine
rotor. This drag force causes severe non-linearity at very low flow
rates. To eliminate this low-flow rotor drag, an "active" pickoff coil
must be used. The Range Extending Amplifier LFA-300 is the necessary
electronic unit for use with such an active pickoff and supplies an
amplified pulse output with the same frequency as the input signal.
The LFA-300 can extend the operational range of turbine flowmeters from
their normal 10:1 ratio up to a ratio of as much as 250:1. In the low
flow ranges, because of the zero offset phenomenon, the output will be
non-linear; however, it will be a repeatable non-linearity. The
LFA-300 is a solid-state unit normally packaged in a heavy-duty steel
JIG box with input, output, and power connections made through MS-type
connectors.
SPECIFICATIONS:
"Turbo-Probe"
Model FTP-A
Velocity range span 1.5-30.5 m/s (5-100 fps)
Velocity range ratio
Turbine head dimensions
Linearity
Repeatability
10:1 standard
1.9 cm (3/4 in.) dia &
length
±0.5%
up to ±0.1%
Model LFO-200
Model FTP-B
0.09-30.5 m/s (0.3-
100 fps)
10:1 standard
3.2 cm (1.25 in.)
dia & length
±0.5%
up to ±0.1%
Signal Input:
Signal Output:
Frequency range - 1 to 3000 Hz. Input
level - 5 to 20V pulse
Frequency - Input frequency from flow-
meter plus injection frequency
249
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Internal Adjustments:
Power Requirements:
Dimensions:
Input:
Output:
Power:
Dimensions:
COMMENTS:
Output level - .5V peak-to-peak
pulse
Offset Frequency Range - 0.5 to 25 Hz.
Cutoff Frequency Range - 1 to 25 Hz.
115V 60 Hz. Less than 5 watts
15.4x10.2x7.6 cm (6x4x3 in.)
Model KFA-300
1 to 3000 Hz from turbine flowmeter
active pickoff
10V peak-to-peak pulse into 10K load,
frequency identical to input frequency
24 VDC 50 mA, 115V 60 Hz optional
15.4x10.2x7.6 cm (6x4x3 in.)
These turbine point velocity sensors may find some application in
attended use in wastewater flow surveys. The range-extending option
appears attractive, and their sensitivity should allow velocity pro-
filing and the like to be accomplished fairly well. They do not appear
suitable for unattended use or fixed installations, however.
250
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(212) 227-6668
MANUFACTURER: FLUMET CO.
P.O. BOX 575
WESTFIELD, NEW JERSEY
N.Y. OFFICE: TELEPHONE
PRODUCT LINE: PALMER-BOWLUS FLUMES
DESCRIPTION:
FLUMET manufactures a "trapezoidal throat venturi weir" that has evolved
from the Palmer Bowlus flume. It is comparable to a Parshall flume in
accuracy and in minimum restriction to flow, but the throat area design
avoids the necessity for the rectangular approach section. The trape-
zoidal section is hydraulically like circular channel flow and
establishes a usable energy head. The Flumet units are three-piece
flumes designed for installation where through-type manholes exist on
normally sloped lines. All Flumet flumes will pass solids up to
7.62 cm (3 in.) spherical equivalents.
Where sewers exist, and to permit surveys, the standard hexagonal units
can be placed under flows of 50 percent depth. The flume is placed near
the manhole out-fall. The channel should be "U" shaped, with side walls
up to 90 percent of the line diameter; if too shallow, temporary walls
can be created. To install, the base (or sill casting) is dropped in
place, and then the side walls are locked in and dropped back against
the walls at a controlled angle; a template is provided for checking.
Grouting is seldom'required, and small leaks are often quickly sealed
by the fibrous particles of waste flow, due to the ribbed back design.
Use of a stilling well and large area float will produce maximum head
accuracy. The flume is compatible with various secondary metering
instrumentation.
Flumet's eccentric flume reducer is designed for large conduits (waste
collector lines) whose diameter is based on future flows, but where,
initially, lower-volume flows must be metered. The Flumet split ec-
centric reducer can be installed, then dismantled and removed later,
under flow. These modules are molded of acid-resisting, glass resin
and fiber laminates, made in 68.6 centimeter (27 inch) lengths to pass
through manhole frames. Field installations can be made in 1-1/2 to
2 hours.
SPECIFICATIONS:
Accuracy:
Sizes:
3% (optimum)
15.2 to 76.2 cm (6 to 30 in.) for
standard sewer piping.
251
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Flow Capacities:
Length:
Weight:
From 1.32 MLD (0.350 MGD) for 15.2 cm
size to 53.0 MLD (14 MGD) for 68.6 cm
sizes
27.9 to 132 cm (11 to 52 in.)
5.4 to 79.4 kg (12 to 175 Ibs)
PRICES.: Approximately $200-$500 for a basic insert flume.
COMMENTS:
Palmer-Bowlus type insert flumes were thoroughly discussed in Section VI
and no further comments will be made.
252
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MANUFACTURER:
PRODUCT LINE:
THE FOXBORO COMPANY
FOXBORO, MASSACHUSETTS 02035
TELEPHONE (617) 543-8750
PRIMARY DEVICES - TARGET, ELECTROMAGNETIC, AND TURBINE FLOWMETERS.
SECONDARY DEVICES - DIFFERENTIAL PRESSURE TRANSMITTER, MERCURY-TYPE
FLOWMETERS, LIQUID LEVEL TRANSMITTERS, AND VARIOUS FLOW INTEGRATORS,
RECORDERS, ETC.
DESCRIPTION:
Foxboro is a leading, worldwide supplier of instruments and systems for
process management and control. It has more than 60 years of specialized
experience in the production of measurement, recording, and control de-
vices and systems designed to measure, handle, and control liquid flows,
liquid levels, pressure, etc. This varied line of instrumentation
ranges from meters, recorders, and indicators to complex digital con-
trol systems fully equipped with computers and other data processing
equipment.
Primary Devices
Target Flowmeters - Foxboro manufactures both pneumatic and electronic
target flow transmitters. These transmitters produce repeatable force-
balance measurement and transmission of both clean fluids and fluids
of a heavy, conductive and non-conductive viscous nature (such liquids
include slurries up to 1500 psi, even in high viscosity regions where
pipe Reynolds numbers are 2000 or less). Because target-type devices
are generally unsuitable for storm or combined sewer flows, they will
not be discussed further.
Electromagnetic Flowmeters - Based on more than 16 years of experience
in magnetic flow measurement, Foxboro has recently introduced completely
redesigned electromagnetic flow instruments. Nearly any electrically
conductive liquid (up to 160°C) can be accurately metered (e.g.: dirty,
viscous, corrosive, or abrasive slurries; solids bearing; turbulent;
etc.). Both industrial and municipal water and waste treatment plants
utilize Foxboro magnetic flow systems. Typical applications include
plant-effluent, activated sludge, raw sewage, etc.
Representative of this product line is the Series 2800 flow transmitter,
which operates at line sizes of 2.54 to 30,5 cm (1 to 12 in.)*. The
* Other transmitters are available for line sizes up to 122 cm (48 in.)
253
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magnetic flow transmitter responds to liquid velocity only. It gen-
erates an AC voltage directly proportional to fluid velocity and, hence,
volumetric-flow rate. The transmitter is unaffected by process varia-
tions in density, viscosity, line pressure, vibration, or temperature.
The transmitter is accurate with liquids as low in conductivity as
2 micromhos per centimeter. System accuracy to ±0.5% of full scale can
be achieved. The unit operates in horizontal, vertical, or any angular
position as long as the electrodes are in the same horizontal plane.
Transmitters are available with flow tubes of fiberglass or stainless
steel lined with TFE or polyurethane. Coils are external to the flow
tube for accessibility and protection from process and environmental
conditions.
The 2800 Series transmitter contains no converter-type circuitry but can
be equipped with the Foxboro 696A Series converter to obtain direct
totalization of liquid flow.
Turbine Flow Transmitters - These devices measure volumetric flow. The
liquid stream passes through a rotating multi-blade rotor. As the rotor
turns, a pickup coil induces a pulse of voltage (as each blade passes).
The pulse rate is proportional to volumetric flow rate, each pulse being
a measure of a discrete volume of liquid. Because it is generally con-
sidered to be unsuitable for sewage and waste-water applications, the
turbine meter will not be discussed further.
Secondary Devices
Force-Balance Transmitters - This device uses the Foxboro-developed
differential pressure cell transmitter mechanism to measure the pressure
differential produced by any one of a variety of primary devices (e.g.,
venturi tubes, orifices, etc.) and transmits to remote receivers
(pneumatic or electronic) any variable which is a function of pressure,
flow, liquid level, density, or temperature.
Mercury-Type Flow Meter - This device gives precise metering of liquid,
steam, and gas flows at pressures up to 2500 psi, and is suitable for
use with a number of differential-pressure type primary devices. They
are normally equipped with 30.5 cm (12 in.) circular chart recorders.
Flow Integrators - These devices indicate the number of gallons or other
units of fluids passing through a specific point in a given time period.
The quantity is shown on a 6- or 8-digit counter. They are available
for simple integration, remote integration in both electronic and
pneumatic systems, pulse duration, and continuous integration. They
also have provisions for batching, switching, etc.
254
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Electromagnetic Flow-To-Current Converter - The 696A Series converter
accepts the generated voltage from the electromagnetic flow transmitter
and transmits a standard DC signal to electronic receivers. Outputs
can be either 10 to 50 mA or 4 to 20 mA. The signal is directly pro-
portional to (linear with) flow rate. A scaled pulsed output is also
available for direct flow totalization in engineering units.
Other Electromagnetic Flow Measurement Instruments - Other Foxboro
instrumentation in this product line includes the 9650 Series Dynalog
Recorder, which receives and records the generated voltage output of
the transmitter on a 30.5 cm (12 in.) circular chart or provides large
dial indications. Foxboro also manufactures a wide line of pneumatic
and electronic controllers, recorders, integrators, and counters.
Liquid Level, Density, and Interface Instruments - Foxboro instrumenta-.
tion provides various approaches to liquid level measurement. Included
are air bubble systems, submerged diaphragm boxes, float and cable sys-
tems, direct-connected static head systems, diaphragm and mercury •• .
manometer elements, etc.
COMMENTS:
The devices offered by Foxboro have been thoroughly discussed elsewhere
and will not be further described here.
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MANUFACTURER: GM MFG. AND INSTRUMENT CORPORATION
2417 THIRD AVENUE
NEW YORK, NEW YORK 10451
TELEPHONE (212) 665-1601
PRODUCT LINE: CURRENT METERS AND ACCESSORIES
DESCRIPTION:
This firm manufactures a number of hydrographic current meters and
accessories, a few of which will be described here. "GEMWARE" current
meters are supplied with light-weight propellers, specially shaped to
operate at all rated water flows with a minimum of friction, to ensure
highest registration accuracy. Their hydrodynamic forms were developed
after many towing tank trials. They are electrical switch-type meters,
producing either a -mechanical contact by a gear or a frictionless con-
tact by a magnet. The contacts may be registered by earphones, buzzers,
blinking lights, digital counters, digital printers, strip chart event
recorders, etc.
For deep or fast water, the current meter is usually suspended by its
electrical cable with a hydrodynamic weight at the end. For shallow
water operation, it may be attached to a wading rod. When using current
meters for measuring water flow in conduits or pipes, etc., adjustable
holders for mounting can be furnished. Differently pitched, hydro-
dynaraically shaped, and vane type propellers have been specifically
developed for measurements of slow, medium, and fast currents. They
are of lightweight metal alloys, surface treated to better withstand
corrosive action, and are carefully hand finished and polished. Each
is individually tested with its current meter and furnished with a
calibration certificate; with a graph, an accuracy of 0.025% may be
expected. The propeller shafts rotate on precision bearings and almost
all meters are sealed or protected against water entrance, either
mechanically or by an oil bath. "GEMWARE" current meters are shipped
in sturdy, compartmented, wooden carrying cases with accessories, spare
parts, and tools.
The No. 232WA060 "GEMWARE" Mechanical Contact Current Meter, with a
25 cm (10 in.) pitch x 12 cm (4.7 in.) diameter contoured propeller
can measure flow rates .over a range of 0.2 to 5 m/s (0.6 to 17 fps).
Exchangeable gears provide electrical contact for either 10 or 20 turns
of the propeller. On special order, other gears can be supplied to
make contact for each 5 propeller revolutions or to indicate reversal
of flow direction. The meter may be affixed to a wading rod or may be
cable suspended with a self-aligning, hydrodynamic-shaped weight and
tail vane.
256
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The N0.232WA240. "GEMWARE" Magnetic Contact Current Meter (Figure A)
is the modern concept of a hydrodynamically constructed meter which is
reliable for water speed measurements in rivers, dams, reservoirs, etc.
It is streamlined and watertight and has a hermetically-sealed,
magnetically-attached switch electrically connected to a watertight
jack for the plug-in electrical cable. There are no exposed gears or
components to wear or corrode nor can the electrical contacts become
fouled, as with the Price current meter. It may be used in silt-laden
waters without damage as all the components, except the propeller, are
Figure A
sealed within the one-piece, machined housing. The propeller can be
supplied with a special coating to improve its hydrodynamic efficiency
and resist the possibility of corrosion. This meter is extremely
sensitive to waters flowing at all speeds and accurately measures flow
over a range of 0.2 to 5 m/s; its 25-cm pitch, lightweight propeller
is supplied with an individual calibration to assure accuracy for flow
calculations. It is reliable and is unconditionally guaranteed as to
quality and workmanship. The meter is furnished in a sturdy, hinged-
cover, wooden case with compartments for the current meter, spare
parts, 10m (33 ft) long reinforced lowering cable, lubricating oil,
and tools. The complete apparatus with accessories and storage case
weighs 6 kg (13 Ibs); the case dimensions are 35x21x14 cm (14x8.5x
6 inches).
The No. 231WA300 "GEMWARE" Current Meter is an improved Ekman type
meter. This is a mechanical instrument and is operable at any depth
by the use of messengers. The patented split bearing system allows
fastening of one or more meters at any point on the wire. As it is
messenger operated, it can even be placed on the wire between water
bottles or other messenger-actuated instruments. Accidental damage
is minimized by rugged construction and the use of metal guards to
protect moving parts. All materials used are non-magnetic and the
entire instrument is silver plated. A spring-loaded, flared, split
257
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tube is provided to lock the propeller until ready to start the meas-
urement. At that time, a messenger is dropped down the wire to actuate
the split tube release which rotates, horizontally, about 45 degrees,
giving the propeller a short push to overcome any starting inertia
when measuring very low speed currents. After a predetermined time
period elapses, a second messenger is dropped to release a spring-
tensioned short rod, which then also rotates on a horizontal plane
and passes between the propeller blades to stop further rotation.
With every 33 revolutions of the propeller one metal ball falls through
a tube in the dial counter gear box and into a trough on a freely-
moving, pivotally-mounted, plastic coated, permanent magnet. The ball
rolls down the trough and drops into one of the compass box compartments,
numbered from 0 to 35. Compartments 0 and 18 are fixed parallel to the
axis of the propeller shaft; the magnet always orients to the North.
The ball storage tube has a reservoir at the top, closed by a screw cap.
Generally 50 percent of its capacity is filled with balls of one color
and the balance filled with differently colored balls. Using balls of
two different colors assists in determining the approximate time a
major underwater directional current change may take place during the
measuring cycle. One can readily ascertain the mean current direction,
and its variations, by noting the number and locations of the metal
balls in their respective compartments. The meter is 30 cm (12 in.)
high and 61 cm (24 in.) long with tail fin attached.
The No. 232WA080 Shallow Water Current Meter, Price Pattern, is made
to the specifications of the U.S. Geological Survey. Most of the com-
ponents are fabricated from brass and nickel-plated for protection and
good appearance. This instrument is also made in a pygmy size for use
in shallow waters or restricted areas.
PRICE:
Prices range from around $275 for a Price meter to $520 for a magnetic
contact current meter.
COMMENTS:
The use of current meters was thoroughly covered in Section VI and will
not be commented on here.
258
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MANUFACTURER: HINDE ENGINEERING COMPANY OF CALIFORNIA
P.O. BOX 56
SARATOGA, CALIFORNIA 95070
TELEPHONE (408) 378-4112
PRODUCT LINE: PALMER-BOWLUS S.UMES
DESCRIPTION:
The Hinde Engineering Company manufactures "Accura-Flow" insert flumes,
which are generally of the Palmer-Bowlus type. These flumes are adapt-
able to many unpressurized flow measuring applications, including
sewage and industrial wastes in open channels or in certain cases, pipe-
lines. Some can also be installed on a temporary basis to verify flow
trends. Some of its most important characteristics are reasonable
measurement accuracy, low energy loss, minimum restriction to flow, and
ease of installation in existing conduits, operation, and maintenance.
The flume is installed in either a "U" channel or circular conduit sec-
tion with the flume set level at the proper location such that flow
through the flume will be laminar, with a slight "ponding" effect just
ahead of the flume. If it is desired to measure low flows in a large
channel or conduit, this may be accomplished by setting the Palmer
Bowlus flume in a channel liner. This arrangement permits accurate
measurements where the system flow will gradually increase over a long
period of time. Initially, with a small flow rate, the proper size of
flume is selected and set in a liner of correct size. Then, as the flow
range increases up to the maximum design of the particular size of
Palmer Bowlus flume, the next appropriate size is selected and installed.
This series of flume modifications permit proper flow measurement up to
the design limit of the channel or conduit. Any abnormal flows such as
storm water will overtop the flume insert and liner without detrimental
effect. ,
Either on-site or remote registering secondary devices may be used with
these flumes to give permanent records of flow rates and totalized vol-
ume. Stilling wells, scow floats, and bubbler systems have been success-
fully used when employing on-site recorders.
The basic Accura-Flow flume (without modifications) is constructed of
stainless'steel and is a one-piece integral unit. Some examples of the
various configurations and applications of this flume are as follows:
• A typical manhole installation (Figure A).
• A flat-bottom flume for measurement in an open trapezoidal
channel (Figure B).
259
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2 D,
Z.5D2
MIN
— is.
FLOW \
N!
—
^
L/
7
k
r
D,
02
ORIGINAL PIPE OR U-SHAPED
CHANNEL DIAMETER
ACCURA-FLO CHANNEL
REDUCER DIAMETER
PROVIDE ANCHORS
— TO SIDEWALL.IF
/REQUIRED
0.5 Dz
METERING ZONE 0.5DZ
FILL WITH LOW
STRENGTH CONCRETE
ACCURA-FLO
PALMER BOWLUS
METERING
FLUME
ACCURA-FLO
CHANNEL REDUCER
PROVIDE MIN
SLOPE REQUIRED
FOR RUN-OFF
ALTERNATE VIEW
FOR MANHOLE
Figure A
260
-------
Figure B
Figure C
Figure D
261
-------
A flume built into a channel liner fitted with end plate
adaptors. This design is intended for use in measuring
low flows in an existing channel (Figure C).
A dual channel assembly, each having a flume of different
capacity. The two channels measure seasonal flows on a
selective basis (Figure D).
SPECIFICATIONS:
Accuracy:
Submergence
Maximum Recommended Slopes and
Maximum Discharge Capacities:
Comparable to that of Parshall or other
types of venturi flumes. Experiments
have indicated that, within the normal
range of flows (from less than 10% to
90% of pipe capacity), the errors are
less than 3%.
Less than 0.85 D (pipe diameter or
channel width).
Diameter
15.2
20.
25.
30.
38.
45,
53.3
60.0
68.8
,3
.4
,5
.1
,7
in.
6
8
10
12
15
18
21
24
27
Max. Slope
2.2
2.0
1.8
1.6
1.5
1.4
1.4
1.3
1.3
Max. Flow Capacity
&/s cfs
9.9
19.8
35.4
55.2
96.1
151
219
338
416
0.35
0.70
1.25
1.95
3.40
5.35
7.75
11.95
14.70
262
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MANUFACTURER:
PRODUCT LINE:
DESCRIPTION:
HOWELL INSTRUMENTS
3479 WEST VICKERY BLVD.
FORT WORTH, TEXAS 76107
TELEPHONE (817) 336-7411
SOLID STATE DIGITAL INDICATORS, COUNTERS, TOTALIZERS,
RECORDERS, ETC.
Howell Instruments manufactures a number of precision instruments that
might be used as secondary devices in a total flow measuring system.
H600 Digital Indicator - The H600 Digital Indicator is a compact, ac-
curate, and reliable instrument that displays outputs in engineering
units from flow meters (square root), frequency transducers, linear
signal sources, or signal transmitters (10-50 ma, 1-5 volts, etc.).
The display, which uses ,0.65-inch characters, includes four digits .of
data, an out-of-range caption, and an engineering units identification
caption. This panel-mounted instrument has a low power requirement,
over 120,000 hours MTBF (does not include readout lamps), and low cali-
bration drift. Options include BCD output, analog output, 12- or
28-volt DC power, alarm limit and an alternate case.
H2300 Portable Digital Indicator - The H2300-1 Portable Indicator uses
a rechargeable power pack with the H600 Digital Indicator to provide
a completely self-contained instrument. The H2300 can be operated as
a bench-type instrument from the AC power line even when the power pack
has been completely discharged. In addition, the H2300 can be charged
indefinitely without harming the power pack.
Multipoint Digital Indicator - The Multipoint Digital Indicator is an
enclosed, portable unit that accepts up to 12 two-wire inputs using
Howell's H600 Digital Indicator. The indicator uses either pushbutton
or toggle switches to select a single input. Switches are identified
either by an engraved number on the pushbutton or switch identification
cards. Options include 12- or 28-volt DC power and adjustable alarm
limits.
H603B Totalizer and H603E Batch Counter - Adjustable scaling (meter
factor) is featured in this new series of totalizers and batch counters.
Both the totalizers and batch counters count from switch closures,
pulses, AC inputs, and voltage transitions; they also include adjust-
able scaling for a direct engineering unit readout. Plug-in components
permit field modification to change the type of input accepted. The
totalizer and counter accept input levels as low as 10 millivolts rms
and frequencies up to 50 KHz. A seven-segment, half-inch high, gas
discharge module provides the display. The H603B and H603C (only
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difference is in case) totalizers include a six-digit display with
movable decimal point. The H603D and H603E batch counters (only dif-
ference is in case) have a five- or six-digit display with movable
decimal point and include thumb-wheel switches that present the desired
batch count. When the displayed number reaches this preset count, a
lamp and relay both operate.
The totalizers and batch counters include as standard equipment a
counter reset button and a "run" lamp that lights during a counting
operation. The totalizers and counters can also be started and stop-
ped by a remote switch closure or TTL signal having a minimum duration
of 50 msec. The meter factor is set using binary rocker arm switches.
These switches divide the input by any whole number from 1 through 4095
before display. Options are available to expand the division feature
(through 65,535) to double the readout to count both positive and nega-
tive voltage transitions, and to multiply the input by 1.0000 to 1.9999
which, when combined with the divider switches, can adjust the input to
read out input/display ratios that are not whole numbers.
The H603B totalizer and H603D batch counter are housed in a panel-
mounted case that permits the chassis to slide out the front of the
case for removal or adjustment of meter-factor switches. No tools
are necessary. The H603C totalizer and H603E batch counter are also
housed in a panel mounted case; however, their chassis are not mounted
on slides. The front bezel snaps on, covering the chassis mounting
screws. Top and bottom covers are removable to obtain access to all
components. A separate temperature compensator module, compatible
with the totalizers and batch counters, is available to compensate for
specific gravity changes in flow measuring applications.
H490 Digital Data System - The H490 Digital Data System is a flexible,
compact system that measures inputs from signal conditioners or trans-
mitters, and other linear sources. Data are displayed and printed
directly in engineering units. The H490 System can operate from two
different sensors and can monitor from 10 to 100 points. Scanning
modes include (a) continuous monitoring of either one or all points
and (b) manually initiated scanning of all points one time. Points can
be omitted from the scanning sequence in groups of ten. A timed-start
feature permits unattended system operation by automatically initiating
a print sequence at every 10, 20, 30, or 60 minute interval. The
standard printout consists of a six-digit time group, two digits of
point identification, and four or five digits of data together with
appropriate range identification. As an optional feature, up to two
limits are available. They can be programmed as high or low and
adjusted to operate an alarm relay at any point in the readout range.
H4200 Digital Data System - The H4200 Digital Data System is a fast-
reading, high-input capacity system that measures signals from signal
conditioners or transmitters, and other linear sources. Data are
264
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displayed and printed directly in engineering units. Catalog modules
are combined in-the H4200 to provide (a) four recording options,
(b) speeds of up to 20 points per second, (c) up to 1000 inputs,
(d) either one Or two individual limits per point, (e) up to four dif-
ferent ranges, and (f) point omission either singly or in groups of
10. The H4200 system generates output data that are recorded on a
line printer, an electric typewriter, or a teletype unit. Two types
of out-of-limit detection and alarm devices are available. One type
provides one limit, either high or low, for each point. The other
type offers two limits - high and low, high and higher, or low and
lower - for each point. Limits are digital, can be either positive
or negative, and are adjustable throughout the range of the system.
Scanning modes include (a) continuous monitoring of one point, (b) con-
tinuous scanning of all points, or (c) manually or automatically ini-
tiated single scan of all points. Any of these modes can be initiated
either locally or remotely by an external switch closure. Points can
also be manually selected and printed one point at a time.
H4500 Digital Data System - The H4500 Digital Data System uses a digital
processor (computer) to control the system. Ability to readily produce
a custom software, package has enabled Howell to design standard hard-
ware that can be tailored to a great variety of customer needs. Opera-
tional modes, types of signals measured, the display and printout
format, and any computational arid correctional operations performed in
the computer can be designed to customer requirements.
The H4500 System measures and records data in applications where a
number of points and/or parameters must be accurately recorded in engi-
neering units. This system is ideally suited to applications involving
measurement of nonlinear signals or measurements requiring corrections
and computations dependent on other parameters. The H4500 can measure
inputs directly from all industrial type sensors including speed and
flow types (frequency), transducers, strain gages (pressure, torque,
load, displacement, etc.), and other transducers having a voltage,
resistance, or frequency output. The H4500 can also accept signals
from signal conditioning transmitters (10-50 ma, 4-20 ma, 1-5V, etc.)
or provide state indications of contact closures. A typical H4500
System consists of a freestanding equipment cabinet, which includes a
digital processor; a teletype terminal; and one or more display modules.
The system can accommodate up to 1024 inputs, scan up to 50 points per
second, and detect out-of-limit points. The remote digital display
reads out both measured and computed data. While the Teletype is not
the only input-output device available with the H4500 System, it offers
a satisfactory compromise between versatility and economy in most ap-
plications. The teletype terminals*s function is two-fold. First, it
operates as a printer to record data in any of the various operational
modes. Second, keyboard commands to the digital processor initiate the
265
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operational modes, omit points from scanning, change limits, store point
messages, and even change scaling and zero offset of points on an
individual basis.
Optional features include alarm limits, printed English language
messages to simplify point identification, computed and corrected values
(square roots, logs, differential measurements, etc.) based on input sig-
nal measurements, and remote readout(s). Other options include a CRT
display with or without an input keyboard, a high speed line printer,
separate alarm message printer, analog outputs for trend recording,
timed start for unattended installations, computer interface, and mag-
netic tape recording equipment.
266
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MANUFACTURER: INTEROCEAN SYSTEMS, INC.
3510 KURTZ STREET
SAN DIEGO, CALIFORNIA 92110
TELEPHONE (714) 299-4500
PRODUCT LINE: CURRENT METERS^, WAVE AND TIDE GAGES
DESCRIPTION:.
As its name implies, InterOceah Systems offers a wide line of sensors
and instrumentation initially designed for oceanographic applications.
Several of the products they market could find use in the wastewater
area, however. Their current meters include the Ekman-Merz, ducted
Impeller, Savonious rotor, and electromagnetic types. These meters are
available as self contained units with analog or digital self-recording
'or as remote units with real-time readout. Of the current meters just
mentioned, only the electromagnetic self-recording Model 195 will be
described.
Model 195 Current Meter - The Model 195 Current Meter incorporates the
inherent advantages of a solid-state, no-moving-parts sensor with many
optional sensors for environmental monitoring as well as automated
instrument recovery. A unique data preprocessing circuit and flexible
data formatting are combined with a computer-compatible digital cas-
sette data recording system.
The entire instrument may be installed below the water surface on any
structure or it may be implanted on the bottom. Being out of sight
drastically reduces its vulnerability to vandalism and accidental
mishaps. The current speed, direction, time and optional parameters
may be recorded for periods up to 90 days (or one year, optional).
At the end of the monitoring period, when the operator replaces the
digital tape cassette and batteries and cleans the sensor head, the
instrument is ready to be deployed again. The data recorded on the cas-
sette are ready for transcription or direct computer data processing.
The current sensor consists of an electromagnet and two electrodes en-
capsulated in a rugged, waterproof anti-fouling neoprene assembly. The
electromagnet produces a magnetic field. When the water passes through
the magnetic field, a potential gradient is produced which is sensed by
the electrodes. The voltage representing the magnitude of the water
current is fed into the solid state signal processing electronics,
digitized, and recorded on the internal digital cassette magnetic tape
recorder.
STG/100 Wave and Tide Gages - These gages are used to monitor waves and
tides over wide ranges with extremely high precision. The instrument
can be used to sense rapid or gradual level fluctuations in lakes,
267
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rivers", estuaries, harbors, and ocean coastal zones. The basic instru-
ment contains a sensitive, temperature-compensated, multi-turn Bourdon
tube pressure element. A patented optical.system senses the pressure
signal, eliminates hysteresis and provides a wide dynamic operating
range with no sacrifice in high precision. Both remote and self-
contained models are available. The remote model has a cable connected
to a remote power supply, data display, and recording station. The self-
contained recording model is available with either a miniature strip
chart recorder or a digital magnetic tape cassette. The response time
of the instrument is adjustable by using one of a variety of filters
available. This feature permits optimum use of the basic instrument
for the study of phenomena ranging from short period wind waves through
tides.
A light beam focused through a unique grid system is used to sense very
small changes in rotation of the freely suspended Bourdon tube. An
electronic servo network nulls the light beam signal to provide a highly
accurate and linear output over a single small scale. The grid system
also provides for multiple scale nulls so the dynamic range of the in-
strument is greatly extended without affecting the accuracy. The
instrument can be attached to existing or specially provided structures,
or lowered directly to the bottom. Since the instrument functions as a
multiple null detector, it is ready for use without any adjustments
independent of the water depth into which it has been placed. Accuracy
is independent of water depth.
SPECIFICATIONS:
Model 195 Current Meter
Sensor
Type:
Range:
Accuracy:
Resolution:
Compass
Type:
Range:
Precision:
Recorder
Type:
Capacity:
Electromagnetic
0.03 to 3 m/s (0.08 to 10 fps)
±2% Full Scale
0.03 m/s (0.08 fps)
Permanent Magnet
0 to 360°
±5°
Digital, Cassette
2.7 x 106 Bits
268
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Precision:
Record:
Format:
Clock
Type:
Accuracy:
Dimensions
Sensor:
Pressure Case:
Weight:
Model ST6/100 Wave and Tide Gage
Range:
Precision:
Wave Filter:
Clock:
Data Interval:
Operating Time:
Operating Depth:
Power:
Pressure Case:
12 Bit Words
Identification Word-Time-Speed-
Directiori-Options
Programmable| Instantaneous, High/
Low/Mean, High Density • ' •
Digital, Solid State
±0.01%
2.5 cm (1 in.) OD x 18.5 cm (7.25 iri.)L
16.5 cm (6.5 in.) OD x 84 cm (33 in.) L
10 kg (22 Ibs) in air
30m (98 ft)
±3 mm (0.01 ft)
None for short period waves; as re-
quired for longer period waves.
Bulova Accutron with hourly event
marker.
Continuous, once per min., or others
optional.
20 days minimum on self contained tide
models or up to one year optional.
200 meters maximum; others available.
Internal mercury batteries; optional
rechargeable batteries or external
supply.
i.
Hard Anodized Aluminum 20 cm (8 in.)
diameter by 38 cm (15 in.) long.
PRICES: Not available
COMMENTS:
at time of writing.
The electromagnetic current meter may find some use as a portable de-
vice for, survey work. The rather novel wave gage is essentially a head
sensing device, and would appear promising as a secondary element for
use with head-area type primary devices for certain specialized
applications.
269
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MANUFACTURER: J-TEC ASSOCIATES, INC.
317 7TH AVENUE
CEDAR RAPIDS, IOWA 52401
TELEPHONE (319) 366-7511
PRODUCT LINE: LIQUID FLOWMETERS, CURRENT METERS
DESCRIPTION:
J-TEC Associates Inc., a recently established firm (1968), has devel-
oped a sonic vortex flow measurement technique which they believe "will
advance the state-of-the-art in the water and wastewater fields". The
company has patented a technique for the measurement of the vortex or
eddy shedding frequency behind an obstruction or strut in a fluid flow
stream by using an ultrasonic beam. The company's liquid flowmeters,
similar to their VF-500 gas flowmeters, are designed to measure liquid
flow in full pipes; their Model CM-1106B current meter is suitable for
the measurement of open channel fluid flows.
In the J-TEC ultrasonic vortex-sensing device, an ultrasonic beam is
passed through the vortex path and, in effect, counts the number formed
per second to determine velocity. An ultrasonic signal is received
from a transducer across the flow path and is modulated both in ampli-
tude and phase at the vortex shedding velocity. The signal is processed
so that output pulses are a direct, linear measure of flow velocity.
Liquid Flowmeters - The detected modulation frequency is used as the
primary output of the flowmeter. This frequency can be counted for a
direct digital display of flow rate or applied to a frequency converter
for a voltage or current output. Although this flowmeter uses the same
technique as the VF-500 series gas flowmeters, usable ranges for this
meter will be (as stated by J-TEC) approximately ten times lower than
listed for each gaseous model, respectively. Flowmeters utilizing the
J-TEC technique have been used over a strut Reynolds number range of
100 to 36,000; in terms of pipe Reynolds number, a value of 900 is nec-
essary to achieve sufficiently turbulent flow to support vortex forma-
tion. There are no moving parts associated with this device. Liquid
flowmeters are available only on a special order basis.
Current Meter - The CM-1106B is a true fluid speed (current) indicator
for use in open channel flows. As in the case of the liquid flowmeter,
this device uses the J-TEC ultrasonic technique for flow speed measure-
ment. An electronic processor provides the user with a choice of out-
puts - pulse frequency proportional to fluid velocity or analog voltage
corresponding to fluid velocity.
270
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SPECIFICATIONS:
Current Meter
Accuracy:
Speed Range:
Power:
Size:
±1%
0.1-5 m/s (0.3-15 fps) (standard)
12 VDC, 50 mA
12.7 cm (5 in.) High X 5.08 cm (2in.)
Diameter
PRICE: Flowmeters - Available on special order basis only
Current Meter (CM-1106 Serires) - $1,090.00 up (depending .
upon model, display, and accessories used)
COMMENTS:
As long as the Strouhal number remains constant, the number of vortices
generated per unit time is directly proportional to the flow velocity
of the medium involved. Any change in the diameter of the strut, e.g.,
due to build-up or debris entanglement, will change the sensor's cali-
bration constant and its accuracy. Therefore, unattended operation in
wastewater flows does not appear attractive.
271
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MANUFACTURER:
PRODUCT LINE:
KAHL SCIENTIFIC INSTRUMENT CORPORATION
P. 0. BOX 1166
EL CAJON, CALIFORNIA 92022
TELEPHONE: (714) 444-2158
CURRENT METERS, ACCESSORIES, FLOATS, AND
FLUORESCENT DYES
DESCRIPTION:
"KAHLSICO" markets a wide range of hydrological and oceanographic in-
strumentation, including the products of GM Manufacturing and Instrument
Corporation discussed earlier. A few of their offerings will be
described.
Integrating Remote Water Current Motor (No. 231WA550) - This meter uses
a Savonius type rotor for measurement of liquid flows. The rotor uses
two balanced Savonius sections, one above the other and displaced
90 degrees around their circumference to assure actuation omnidirec-
tionally about the horizontal plane of the sensor. The rotor has
14 magnets aligned in its base to inductively activate (14 times per
revolution) the electrical switch in the sensor's housing. The opening
and closing of the electrical circuits, which is directly proportional
to the speed of the water current, is monitored by a pulse-shaping
network, the 0 to 20 mA output of which goes into a counter, fast inte-
grator, and finally to the indicator meter (and, optionally, a recorder
or other readout). The response time of the circuit is practically
instantaneous; it readily follows any changes in the turning rate of
the sensor. The system does not saturate and is said to be able to
discriminate and count the actuations of the sensor, even when it is
exposed to a fast current of 3 m/s (6 kn).
Fluorescent Dyes - Fluorescent colors are available in either red or
yellow/green. Unless otherwise specified, red color is supplied on
orders. Yellow/green provides a stronger color when testing silty
waters as the grains of silt absorb the fluorescent red. When used in
a closed system such as a sewer conduit, the dye will last for several
days. Depending upon the clarity of the water, 2 to 5 tablets will
provide a visibility of 1 part per million. The tablets are 2.9 centi-
meters (3/4 inch) in diameter and packed 100 per plastic envelope.
Maximum absorbance is 550 my. Dye cubes are generally used for oceano-
graphic studies or where large masses have to be traced. Kahl also
markets an in-situ opto-electronic fluorometer (VARIOSENS).
Current Drifters and Drogues - KAHLSICO offers a number of current
drifters and drogues in three basic types. The surface drifter is
essentially two sealed, heavy-gauge, clear plastic envelopes sized
7.5 x 12.5 cm (3x5 in.). A drift envelope is a similar waterproof
272
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envelope measuring 15 3.23 ess, (6x9 in.) with a 34 grams (1.2 oz) weight
at the Bottom to provide vertical floatation. Since only a small por-
tion of the envelope is exposed to the wind, the major drift force is
the surface water current.
The ball-shaped Tri-Planar Surface Drogue is molded from brightly-
colored, buoyant, polyethylene plastic, with a 53 cm (21 in.) long
flexible, weighted stem. This 15 cm (6 in.) diameter drifter has two
vertical discs, 180 degrees apart, bisected by a horizontal disc at
their center. The flexible stem has a tubular weight crimped at its
lower end which keeps the drogue floating just below the water surface,
to eliminate the effect of wind. The horizontal disc prevents undue
motion in the vertical direction while the vertical discs have the
effect of presenting the same surface area to water currents from any
side.
The Surface Current Drogue has a large floatation cork at the top of
the 53 cm (21 in.) long, flexible stem and a 20 cm (8 in.) diameter
saucer at the weighted bottom end.
Also offered is the Woodhead sea-bed drifter which has been in suc-
cessful use for over two decades for surveying bottom currents. The
brightly colored, 20 cm (8 in.) diameter, plastic dish has a series of
holes to facilitate vertical descent to the sea-bed. To assure rapid
passage through deep waters, several drifters are usually attached to
a salt block which dissolves in from 20 to 30 minutes to release the
drifters which are then jogged along the bottom by the water current.
SPECIFICATIONS:
No. 231WA550 Integrating Remote Water Current Meter
Speed Range:
Meter Scale:
Threshold and Sensitivity:
Distance Constant:
Recorder Output (Optional):
0.05 to 3 m/sec. (0.1 to 6 knots)
0 to 6 knots in 0.1 knot and 0 to
10 ft/sec in 0.2 ft/sec (m/sec scales,
as well as expanded scale ranges of
0 to 1 knot and 0 to 6 knots, are
available on special order).
0.05 m/sec; 0.1 knot, 0.17 ft/sec
0.74 revolution = 30.48 cm (1 ft) of
linear water movement.
A recorder connector provides 0 to
20 mA maximum output to operate a
250 ohm minimum internal impedance
circuit for a recorder, data logger,
etc. (Other outputs available on
special order.)
273
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Optional External Power Supply:
Built-in Power Supply:
Battery Life:
Dimensions:
Weight:
PRICES:
12 to 30 VDC, 6 mA consumption at
18 VDC, available on special order.
Four Alkaline Batteries, each 4.5V,
connected in series (18V total).
Approximately 150 hours.
Sensor Control Box
20x20x26 cm
(8x8x10 in.)
3 kg (6 Ibs)
21x16x14 cm
(8.3x6.5x5.5 in.)
2 kg (4 Ibs, with
batteries)
No. 231WA550 - Integrating Remote Water
Current Meter
COMMENTS:
$763.00
Items offered by Kahl were discussed in Section VI and will not be
commented on further.
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MANUFACTURER:
F. B. LEOPOLD COMPANY
DIVISION OF SYBRON CORPORATION
227 S. DIVISION ST.
ZELIENOPLE, PENNSYLVANIA 16063
TELEPHONE (412) 452-6300
PRODUCT LINE:
PRIMARY DEVICES - FLUMES, OPEN FLOW NOZZLES
SECONDARY DEVICES - TRANSMITTERS, RECEIVERS
DESCRIPTION:
Flumes ~ Leopold-Lagco fiberglass flumes are Palmer-Bowlus type primary
measuring devices with a rectangular cross-section. They are molded of
LEO-LITE, a patented plastic resin material reinforced with glass fi-
bers. Installation is directly in the sewer line, normally at a stand-
ard straight-through manhole. Flume construction is claimed to be
sturdy enough to permit direct use as a concrete form in permanent in-
stallations, and do not require maintenance.
Leopold-Lagco flumes are available in three standard types - fixed, in-
sert, and cutback. The fixed type is generally used in new construc-
tions where the flume is installed in place of an equivalent length of
straight pipe. The insert type is designed for use in those installa-
tions where the flume can be inserted into an existing half section of
sewer pipe; it is particularly well suited for flow "spot checks" where
a more permanent installation is not required. A modification of the
insert model, the cutback, is used where space is critical. Inserting
the cutback" into a manhole or vault outlet provides more room upstream
for metering, sampling, or other devices. Design capabilities of this
flume include the following:
Demonstrated measurement of low flows in near-zero range.
* Can be equipped with a pointer gage mounted on it for in-
termittent flow readings.
• Can be used with all of the better-known float-actuated
meters, including those with telemetering capabilities.
Some installations have successfully incorporated air
bubbler systems. However, provisions have to be made to
eliminate the aspirating effect caused by flow past the
bubbler orifice.
F. B. Leopold also manufactures a complete line of LEO-LITE Parshall
flumes and Parshall flume liners in throat widths from 7.6 cm (3 in.)
to 2.4m (8 ft). Complete LEO-LITE Parshall flumes have stiffeners and
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spacers for immediate field installation. Leopold also offers cast
iron parabolic flumes (open flow nozzles) in a variety of sizes.
Float in Flume Transmitter - Leopold float-in-flume transmitters are
designed to continuously indicate the flow of sediment-laden liquids as
they pass through Lagco or Parshall flumes or parabolic open flow noz-
zles under gravity conditions. Liquid flow is indicated by the direct
sensing of the level of the liquids within the flume or nozzle; flow
data are transmitted either electrically or pneumatically to a remotely
located flowmeter.
The transmitter is either mounted directly on the wall of the Parshall
flume or on the parabolic nozzle itself. A corrosion-resistant "ski"
type sensor (float) rides directly on the surface of the liquid flow
stream; it does not cause disturbance on the surface of the liquid or
excessive oscillation in recording instrument. As the surface of the
liquid rises or falls, depending upon the flow through the flume or
nozzle, the sensor changes its position accordingly. This movement
produces proportional angular movement of the sensor arm and shaft on
which it is supported.
For electric transmissions, the shaft arm angular movement is trans-
ferred to a stylus riding over a characterized cam which is corrected
for non-linearity and furnishes a linear signal proportional to flow
which is transmitted every 15 seconds, with a pulse duration varying
from a fraction of a second to approximately 12 seconds. Three sec-
onds of each 15-second period are required for the receiver to reset
for the reception of the next signal.
For pneumatic operation, the shaft arm angular movement is transferred
to a shaft carrying a cam characterized to the head quantity relation-
ship of the flume. A pneumatic tracing device senses the profile of
this cam and transmits a linear, 3 to 15 psig pneumatic signal through
an amplifying relay to the receiver.
Advantages of this device include the following:
• Reduces installation space
• Faster responses to flow changes
• Reduces material costs - eliminates stilling wells, con-
necting piping and fittings, large float and cable, back
purge system, etc.
Recorders - The Leopold Type "K" electric receiver/integrator (total-
izer) is adaptable for installation at locations remote from the trans-
mitter and will operate over private two or three wire systems or a
pair of leased telephone wires. Designed to operate with an accompany-
ing time impulse transmitter, this receiver can be applied to the meas-
urement and control of flow, level, pressure, and temperature. The
unit features a 30-centimeter (12-inch), 24-hour chart and nonremovable
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chart hub; indicator, which operates over standard scale - 0 to
100 percent of chart range; and a continuous reading, seven-digit type
totalizer.
SPECIFICATIONS:
Leopold-Lagco Flumes
Accuracy:
Flume Sizes:
Flow Capacity:
PRICES:
up to ±2%
15.2 to 183 cm (6 to 72 in.)
7.25 to 3,313 Si/s (0.25 to 118 cfs)
Leopold-Lagco flume prices range from around $300 to over $3,000 depend-
ing upon material (i.e., LEO-LITE 87 or 82) and additional features such
as integral stilling well, scale, etc.
COMMENTS: . . • .
These products have been discussed in Section VI andawill not be com-
mented upon here.
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MANUFACTURER: LEUPOLD & STEVENS, INC.
P.O. BOX 688
600 N.W. MEADOW DRIVE
BEAVERTON, OREGON 97005
TELEPHONE (503) 646-9171
PRODUCT LINE: FLOWMETERS, RECORDERS, GAGES
DESCRIPTION:
Leupold & Stevens is an old-line company whose products probably need
little introduction. It is to be noted that they have recently dis-
continued their Model 561R, a float-in-flow transmitter arid remote reg-
istering total flowmeter, and Model G161R, a bubbler-type remote
registering total flowmeter. This company currently offers, in addition
to staff gages, devices for measuring flow rates and totalizing volume
in open channels for industrial wastes and municipal sewage. These in-
clude the Stevens Model 61 series total flowmeters and the Type F
recorder.
Flowmeters - Stevens total flowmeters are designed for on-site measur-
ing of open channel flows. They are available in either English or
metric units, and-can be used with any type and size of weir or flume.
With appropriate cam, gears, and scale, flows up to approximately
800,000,000 liters (several hundred million gallons) per day can be
measured through large sizes of Parshall and other types of flumes.
Conversely, a full scale range as small as 0-53,200 Upd (0-14,000 gpd)
through a 22-1/2-degree V-notch weir is available. An AC synchronous
motor drive powers a 7-digit totalizer (for indicating volume) and
chart drive. For applications where commercial power is not available,
an 8-day, spring-drive clock can be obtained. Figure A shows a typical
manhole flow measuring installation.
The Model 61M provides visual indication only. The indicator plate is
graduated to show instantaneous flow rate as noted by the indicator
pointer. A red clip on the indicator plate is positioned by the pointer
to indicate peak flow.
The Model 61R uses a strip chart to provide a permanent record of flow.
A standard 15m by 10.1 cm (50 ft by 4 in.) strip chart is printed on
humidity-resistant tracing paper. Curvilinear time graduations compen-
sate for arc swing of the marking pen, with six minor divisions between
major divisions. Charts are time overprinted every 2, 3, 6 or 12 hours,
depending upon time scale. The chart has uniform divisions for flow,
consisting of 7 major and 5 minor divisions.
Available time scales are 8.5, 12.7, 25.4, or 50.8 cm (3-1/3, 5, 10 or
20 in.) of chart travel per day giving 180, 120, 60, or 30 days of con-
tinuous records, respectively.
Up to 180 days of unattended operation is claimed for these devices.
278
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Figure A
279
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It is recommended by the manufacturer that a stilling well installation
and standard cylindrical float be used whenever possible in order to
obtain better accuracy and chart record (a properly designed stilling
well dampens out surface undulations and wave action). For some appli-
cations, however, a scow float installation can be used to good advan-
tage. Figure B shows two such installations.
Stilling Well
Installation
Scow Float
Installation
Figure B
Recorder - It has been claimed that the Stevens Type F recorder is the
lowest price instrument of its kind for recording open-channel flows
through Parshall flumes or 90-degree V-notch weirs. In operation, a
horizontally supported chart drum is turned by a float (resting on the
water being measured) proportional to changes in water level. A pulley
drive mechanism, controlled by an 8-day clock, moves the pen across the
chart at a constant speed. The combined movement of the drum and pen
produces a graphic record of changing water levels.
SPECIFICATIONS:
Operating features and characteristics are discussed in the preceding
equipment descriptions.
PRICE:
Standard prices were not available at the time of this writing.
280
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COMMENTS:
Leupold & Stevens equipment has proven to be rugged and reliable in
many types of wastewater measurements. They have also provided custom
application telemetering equipment ("telemark") for more complex sys-
tems use.
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MANUFACTURER: MANNING ENVIRONMENTAL CORP.
120 DU BOIS STREET
P.O. BOX 1356
SANTA CRUZ, CALIFORNIA 95061
TELEPHONE (408) 427-0230
PRODUCT LINE: LIQUID LEVEL MONITOR
DESCRIPTION:
The Manning F-3000 Dipper flowmeter series technique is basically a
method of detecting liquid level in open channel flow by sensing the
surface of the water. The control electronics are included in a
modular package, which is mounted, for example, on a portable bracket
at the top of a manhole. A thin, non-corrosive probe is lowered on a
wire controlled by a small precision motor. When the metal probe
makes contact with the liquid surface, a microampere circuit is made
through the conductive liquid to a ground return. This signal reverses
the motor, raising the probe slightly above the surface. After 5
seconds, the probe is lowered to the surface again, and again retracts.
This "dipping" action continues with the probe just above the surface of
the liquid. These changes in cable length are translated to a rotation
of a measuring wheel. See the electromechanical schematic in Figure A.
The flowmeter converts the height signal into a flow rate recording,
a total flow recording, and sampler switch to provide flow proportional
sampling. It can convert from height to flow measurement for many types
of pipes, flumes, and weirs. The rotation of the height measuring wheel
controls an electronic servo system to change to an output which is
proportional to flow. A channel selector allows easy selection of proper
channel shapes — round pipes, weirs, flumes. The flow proportional
output (1) positions a pen indicating instantaneous flow rate on a
recording chart or (2) provides an indicator showing instantaneous flow
rate and (3) rotates a potentiometer which provides an input to the
totalizing circuit. This circuit generates a pulse stream proportional
to the flow and the accumulated count is shown on a total flow counter
on the front panel.
Advantages claimed for the Manning portable flowmeter include:
• Quick installation at street level — The Dipper Flowmeter
allows one man to install this meter at street level in less
than 10 minutes.
Sensor not affected by floating debris — No floats, scows,
tubes, capacitive plates for debris to hang on. No stilling
wells to clog. The Dipper sensor never enters the flow.
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• Direct reading accuracy — Direct mechanical coupling to the
surface level gives better than .003m (0.01 ft) level accuracy
over the total range. Servo-controlled, electronic conversion
provides extremely high accuracy for flow rate and total flow.
• Easy-to-read flow chart — Switch selectable (7 day or 24 hour)
circular chart gives easy to read indication of changes in
flow rate with time, peak flow, etc. Operates with a spring
driven, 8-day clock drive.
• Digital Total Flow Counter ~ A non-volatile counter records
total flow over the given time period. Records with digital
accuracy.
• Battery Operation — Operates on small 12-volt rechargeable
battery.
SPECIFICATIONS:
Maximum Height of Flow Range:
6-24 in. (F-3024)
12-48 in. (F-3048)
15-60 cm (F-3060)
30-120 cm (F-3120)
Channel Shapes Included (Switch Selectable):
Round pipe
V-Notch Weir
Palmer-Bowlus Flume
Parshall Flume
Leopold Lagco Flume
Cipolletti Weirs
(Others available on special request).
Maximum Total Flow Recording:
Up to 999,999 times maximum flow per minute in channel.
(For example: If maximum flow is 1000 gallons per minute —
maximum recording 999,999,000 gallons.)
Size: 23x36x20 cm (9x14x7.75 in.)
Weight: 5.5 kg (12 Ibs)
Flow Rate Indication: 0 to 100% in 5% divisions
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PRICE: Approximately $1,000 and up, depending upon options.
COMMENTS: -.-'..
This portable liquid level monitor and flow converter has a lot to
recommend it as a secondary device for translating depth into flow rate
in many storms or combined sewer applications. The range is less than
might be desired for some sites, and collision with surface debris could
cause an oscillation of the pendulum-like dipper probe resulting in some
inaccuracy until the swinging motion subsides. It also might be pos-
sible for the probe to become coated after extended periods of use,
which could result in a zero-offset. Otherwise, the unit appears quite
promising and merits serious attention as a new technique for measuring
liquid levels.
285
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MANUFACTURER: MARTIG BUB-L-AIR
2116 LAKEMOOR DRIVE
OLYMPIA, WASHINGTON 98502
TELEPHONE (206) 943-2390
PRODUCT LINE: PORTABLE LIQUID LEVEL RECORDER
DESCRIPTION:
This unit is a very recently introduced (Spring 1974) device for meas-
uring and recording depths of wastewater flows. It is expressly de-
signed for manhole use. The equipment package for an installation
consists of a recorder; compressed air bottle; regulators, connecting
hose, and fittings; sensing probes for sewer pipe; and miscellaneous
slings and straps for mounting in a manhole. The device measures flow
depth only, and the user must apply conversion factors as appropriate
for the primary device employed.
SPECIFICATIONS:
The spring-wound recorder has two settings for either 24 hour or 7 day
operation and uses 20.3 cm (8 in.) diameter charts graduated from 0 to
30 inches. The pen has a fine tip for use in humid environments and
uses three drops of ink for a fill. One and two pen models are avail-
able and are housed in a weatherproof case.
The compressed air bottle is lightweight aluminum with a 1,260,000 kgf/
sq m (1,800 psi) working pressure. Various sizes are offered for fill
lifes from 3 to 8 weeks. The primary regulator is a single stage unit
which reduces bottle pressure to about 24,600 kgf/sq m (35 psi). The
secondary regulator is used to adjust air flow rates to bubbles per sec-
ond as visually observed through a mineral oil reservoir. Stainless
steel sensing probes are available in standard sizes from 15.2 to
76.2 cm (6 to 30 in.), and other sizes can be supplied on special order.
PRICES:
Complete packages start at $1,149. These packages include a one-pen
recorder, three sensing probes, and all equipment necessary for instal-
lation and use.
COMMENTS:
These devices are sold direct from the factory only, on a thirty-day,
free-trial basis. The manufacturer is pleased that in the nine months
that this offer has been in effect, not one unit has been returned, and
ninety percent of their customers have placed orders for additional
equipment.
286
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MANUFACTURER: MARY TEC, INC,
C/0 HARRY H. BARNES
613 EAST BAYVTEW, HILLSMERE '
ANNAPOLIS, MARYLAND 21403
TELEPHONE (301) 261-2987
PRODUCT LINE: ACOUSTIC LIQUID LEVEL MEASURING SYSTEM '
DESCRIPTION:
The Aquarius Model 2001 or 2002 Liquid Level Measuring
System is a very recenlty developed (patent pending)
instrumentation system which employs acoustic ranging
techniques to measure liquid levels to within 0.03 cm
(0.001 ft) over a range of 0 to 30m (0 to 100 ft). Con-
tinuous calibration is employed to automatically com-
pensate for ambient changes of temperature, humidity,
and pressure of the gaseous medium above the liquid.
This technique entails monitoring a coincident return
signal from a known distance within the sensor head as-
sembly, mathematical circuitry manipulation, 'and appli-
cation of the resultant factor to the signal of interest
for Determination of the unknown distance.
Advantages of this system are that it has no moving parts,
does not contact the liquid being monitored, and report-
edly can be used in extreme environmental conditions to
monitor corrosive liquids in corrosive atmospheres.
A complete system, shown in Figure A consists of (a) sensor
head assembly, (b) stilling well, and (c) remote electronic
package and control panel for one or more sensor head
assemblies.
The function of the stilling well is to support the sensor
head assembly and contain the transmitted and return
acoustic signals. It consists of plain pipe of appropriate
material, the type of material used being dependent upon
the liquid being monitored.
The Model 2001 and Model 2002 are similar in outward ap-
pearance, except that the Model 2001 is continuously
energized whereas the Model 2002 can be interrogated at
specific intervals and will respond within 50 milliseconds,
no power being consumed during the quiescent period.
K-
Figure A
287
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SPECIFICATIONS:
Accuracy*:
Power:
Output:
0.3 cm throughout 30.3m range
(0.01 ft throughout 100 ft range)
0.03 cm throughout 3.03m range
(0.001 ft throughout 10 ft range)
Model 2001, 1 amp @ 5 VDC
Model 2002, 3 amps @ 5 VDC (only during
interrogation period)
16 line, 4 bits per digit, 4 decimal
BCD (Other outputs optional - e.g.,
binary, ASCII, or analog)
PRICE: $1,400 and up depending upon output desired (e.g., sample .
depth, totalized flow, etc.), materials of construction, etc.
COMMENTS:
The Aquarius is a secondary device that shows great promise for meas-
uring liquid levels in storm or combined sewer flows. The stilling
well pipe can act as a damper to surges in liquid level by using a
small hole to restrict flow to it. This could present plugging
problems, and a configuration with many small holes, e.g., about
0.3 cm (1/8 in.) in diameter, will be preferred. In addition, the
stilling well acts as a sort of acoustic waveguide, eliminating the
echo problems that have plagued attempts to use many other types of
acoustic level sensors in manholes, meter vaults, etc.
The unit must be considered still in the prototype stage. Only one
has been delivered (to the U.S. Geological Survey) at the time of this
writing. Advanced integrated circuit technology (CMOS) has been in-
corporated in the electronics design, and power requirements are low.
Based on preliminary tests, battery life on Model 2002 should exceed
one year. The device is all digital and so is immediately computer
compatible.
* Greater accuracies are optional*
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MANUFACTURER: MEAD INSTRUMENTS CORPORATION
ONE DEY LANE
RIVERDALE, NEW JERSEY 07457
TELEPHONE (201) 835-5988
PRODUCT LINE: OPEN STREAM VELOCITY PROBE (TURBINE)
DESCRIPTION:
•*
The Model HP-301 Open Stream Velocity Probe was designed for use in
pollution control applications requiring the measurement of open stream
water velocities*. Readings are reported to be instantaneous and ac-
curate with no counters, timers, or lengthy test periods required. All
readings are direct and may be made by untrained personnel. The adjust-
able head of the probe allows its insertion into pipe ends and vertical
velocity measurements. The unit consists of a hand held probe
(Model PT-301) and a portable indicator (FI012P).
The PT-301 Probe consists of a low inertia Delrin turbine mounted in a
protective shroud at the end of an aluminum handle. The turbine, when
immersed in a flowing stream, rotates at a speed in direct linear
relationship to the fluid velocity. A small magnet sealed within the
turbine hub produces an electrical pulse in an adjacent induction trans-
ducer for each rotation. The frequency of these pulses is thus also a
direct measure of the fluid velocity. The FI-12P indicator is actually
a portable frequency meter or frequency-to-DC converter. It amplifies
and conditions the pulses to drive a meter indicator in a direct rela-^
tionship to their frequency. The indicator scale is calibrated to read
in the desired units of fluid velocity. The electronic system is stable,
accurate, and all solid state. It is drift-free and requires no opera-
tional adjustments. All power is obtained from a set of eight standard
•C" size flashlight batteries. The current drain is less than that of
a normal flashlight bulb.
SPECIFICATIONS:
Various single or dual ranges are available up to 4.57 m/s (15 fps)
water velocity, with 3 m/s (10 fps) being standard. The threshold of
operation is approximately 0.08 m/s (0.25 fps) for all ranges.
Indicator:
Probe:
250°, 5.6 inch long scale; weight
2.04 kg (4.5 Ibs)
Adjustable handle; weight 0.76 kg
(20 oz)
Includes measurement of industrial or municipal pollution entering
streams or rivers and flow out of large pipes or ducts.
289
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PRICES:
HP-301-A
OPEN STREAM "VELOCITY PROBE, portable,
battery operated. Complete with indicator,
probe, and case. Ready to use. Single
HP-301-A2 As above except dual range
COMMENTS:
---$420.00
$445.00
The lack of any recording provisions will be a handicap in all but
brief survey work. The unit is designed for attended operation, so
fouling should not present too great a problem except in the dirtiest
flows.
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MANUFACTURER:
PRODUCT LINE:
DESCRIPTION:
MERIAM INSTRUMENT
DIVISION OF THE SCOTT & FETZER COMPANY
10920 MADISON AVENUE
CLEVELAND, OHIO 44102
TELEPHONE (216) 281-1100
ORIFICE PLATES AND METER TUBES: PITOT TUBES: LAMINAR
FLOW ELEMENTS: DIFFERENTIAL PRESSURE READOUT AND
RECORDING INSTRUMENTS
Meriam manufactures three differential-pressure type primary elements.
Their standard orifice plates are 0.3 cm (1/8 in.) thick 304 stainless
steel, but can also be fabricated from monel brass or other materials
on special order. Raised-face orifice flanges are offered for line
sizes from 1.3 to 58 cm (0.5 to 24 in.); standard orifice meter tubes
range from 2.5 to 30.5 cm (1 to 12 in.). Other sizes may be available
on special order. Meriam also manufactures simple impact tubes of
stainless steel in lengths from 25.4 to 101.6 cm (10 to 40 in.) and
produces a wide variety of laminar flow elements, which are differential
pressure producers operating on capillary flow principles and are nor-
mally used to measure gas volume rates of flow. None of the foregoing
is deemed suitable for measuring typical storm or combined sewer flows,
and they will not be discussed further.
Meriam manufactures a very wide line of U-type, well-type, and inverted
manometers together with a complete range of scales for many applica-
Iw£nc* -°f 85*ater ^terest in the wastewater field is their bellows
D/P Series 1100 line of differential pressure indicators which are
schematically illustrated in Figure A. Operation of the Meriam
-LOW PRESSURE CONN.
Figure A
291
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Hydraulically Connected Differential Pressure Unit is based on the
interaction of two opposed bellows attached to a machined center plate.
All space enclosed by the two bellows is completely evacuated and fluid
filled The low pressure bellows shaft is connected by a linkage to
transmit bellows motion to the output shaft. Pressures from the
actuating source are introduced to both sides of the bellows system
through either set of taps in the high and low pressure housings. When
pressures on both high and low pressure bellows are equalized, the unit
remains at zero. As differential pressure increases, the high pressure
bellows contracts, forcing fill fluid through the pulsation dampener
passage around the overrange valves into the low pressure bellows.
This causes the low pressure bellows to expand and the attached shaft
to move outward. Through linkage, the linear motion of the bellows
shaft is translated into angular rotation of the output shaft. _Move-
ment of fluid from high pressure into low pressure bellows continues
until the force created by the differential is equalled by the tension
on the range springs. This unit is designed for sustained measurement
and fast response speed. Overrange protection helps assure long periods
of trouble free service. Temperature compensation assures accuracy
under various adverse operating conditions. The bellows are fabricated
of stainless steel, steel, monel, aluminum and others. They require no
lubrication for life and include an externally adjustable pulsation
damper.
Meriam Series 1300 recording flow meters are designed to work with the
D/P bellows units. Spring-wound or electric chart drives in a variety
of chart rotations are available. Also available are integrators, as
well as pressure and temperature pens.
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MANUFACTURER: METRITAPE,. INC.
77 COMMONWEALTH AVENUE
WEST CONCORD, MASSACHUSETTS 01742
TELEPHONE (617) 369-7500
PRODUCT LINE: LIQUID LEVEL MONITORS AND ACCESSORIES
DESCRIPTION:
The unique and patented METRITAPE level sensor, schematically depicted
in Figure A, consists of precision-wound linear, resistive helix held
away from high-strength conducting base strip by thin and stable insu-
lation layer along edges and back. A composite outer jacket encloses
and protects the inner winding system, and acts as a diaphragm to
receive the pressure of surrounding material. Positive or negative
pressures are balanced by pressure-equalizing breather mounted at sensor
top. The resultant continuous METRITAPE sensor is suspended from above
throughout the full liquid height (see Figure B). As the liquid rises,
the length of unshorted resistance helix, extending from the top to
the liquid surface, decreases. The resulting uniform resistance change
with level change may be read, locally or transmitted thousands of feet
over a simple leadwire pair, for remote level indication, alarms, and
controls.
METRITAPE claims a number of advantages for its gaging systems
including: '
• The sensor produces highly accurate readings of material
levels, generally to better than ±0.1% (in liquids) and
independent of depth; long term stability of output is that
of a precision wirewound resistor.
• The transducer essentially has no moving parts, generates
its electrical signal directly at the point of measurement
(the air/liquid interface), and eliminates the need for
moving floats, pulleys, guy wires, linkages, compressors,
air dryers, mercury columns, etc.
• Level measurements are substantially independent of material
specific gravity, product or air temperature, and gas
pressure or vacuum above the material surface.
• Sensors can transmit their electrical outputs directly,
without preamplifiers or electromechanical converters,
for distances of several thousands of feet, at low impedance
level and via low-cost signal-wire pairs, without signifi-
cant accuracy loss.
293
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294
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• The sensor electrical output is suited for real-time computer
monitoring and automatic control.
• Metritape systems can provide local analog level readout at
the top, as well as analog or digital display at one or
several remote locations.
• For highly critical automation systems, two sensors (having
small cross-sectional area) can be mounted back-to-back to
provide continuous and automatic self-checking.
• Frequency response of the sensor is sufficiently fast to
allow oceanographic wave motions to be accurately measured
and recorded.
A METRITAPE level system (see Figure C) generally consists of the fol-
lowing parts: (1) Metritape sensor and capillary breather assembly;
(2) Electrical signal-conditioning and alarm circuitry, usually in
NEMA-style panel box; and (3) Level readout display (analog and/or
digital), plus adjustable level alarms with indicator lights and an-
nunciator flasher and horn. For remote signal transmission, signal
conditioning circuits are used to drive encoding and telemetry equip-
ment, or may drive an analog strip-chart recorder or digital printer
for permanent recording.
The styles of Metritape liquid-level sensors most commonly used in
water, wastewater, and sewage applications are described below. These
include general-purpose, corrosion-resistant, and ruggedized sensor
constructions, and two basic sensor resolutions, general-purpose and
moderate precision. The company expects in the near future to introduce
precision liquid sensor Types PLS and PLS/S, having increased resolution
for average deviations in the 0.003-0.006m (0.01-0.02 ft) range.
Type LS General-Purpose - Useful in water, petroleum, municipal sewage,
and industrial wastewater not having high concentrations of chemical
solvents or corrosives. The outer wetted jacket is adhered Mylar
polyester, and the sensor is protected on three sides by an extruded
bumper-strip of chlorinated vinyl (CPVC). Nominal sensor outer dimen-
sions are 3.6 x 0.3 cm (1.4x0.25 in.), with OD of the upper cap being
3.8 cm (1.5 in.). Resistance helix has nominal 1.3 cm (0.5 in.) winding
pitch, 30 ohms per foot, and temperature coefficient of 0.0001 ohm/
ohm/°C. Available in lengths from -1.2 to 305m (4 to 100 ft), sensor
average deviation is ±0.1 ft) or better, substantially independent of
sensor length. The stabilized Type LS/S provides accuracy upgrading.
The type LS sensor is designed for an outdoor ambient temperature range
of approximately -30° to +60°C (-20° to +140°F), unheated product, 0 to
±10 psi maximum pressure of vacuum. The sensor is supplied with capil-
lary breather assembly and cast aluminum mounting box 15x15x10 cm
295
-------
LOCAL
RECORDER
OR
INDICATOR
TO
REMOTE
DATA
SYSTEM
METRIP1PE
LIQUID
LEVEL
SENSOR
5-100 FT
CONT1NOUS
GAUGING
RANGE
w if $
t •* ;:/•)
M ,:;
-,!i
TM
SIGCON
SIGNAL CONDITIONER
(0-1 VDC, 4-20 MA,...OUTPUT)
SEWER, POND STREAM, WELL OR OCEAN
LIQUID-LEVEL GAUGING SYSTEM
WITH CLAMPED OR MOUNTED
METRIPIPE™ SENSING ELEMENT
Figure C
296
-------
(6x6x4 in.)- The type LS sensor can also be provided with flurocarbon
outer jacket surface for non-stick release finish, designated Type LS(F);
and for fast-response dynamic wave gaging, as Type LS-FR.
Type LS-CR Corrosion-Resistant - Has heat-sealed outer jacket to resist
highly corrosive liquids and chemical solvents. Wetted jacket material
is generally flurocarbon, but can be polypropylene; and protective CPVC
channel holder is used whenever this material is compatible with mate-
rials to be gaged. Electric winding system is as defined above,
resulting in comparable accuracy. Available in lengths from 1.2 to
152m (4 to 50 ft), and supplied with capillary breather assembly and
stainless-steel or fiberglass mounting box.
.Type MPLS Moderate Precision - For increased resolution and repeat-
abxlity, the MPLS sensor has nominal 0.6 cm (0.25 in) winding pitch;
low-temperature-coefficient helix material (0.00003 ohm/ohm/°C);
30 ohms per foot nominal helix resistance; compliant jacketing system,
wxth outer wetted jacket adhered thermoplastic. Other characteristics
essentially as in Type LS above.
Type LSR Ruggedized - For demanding liquid and slurry applications, in-
cluding high head pressures, high-velocity impacting, turbulent slurries,
and stream containing potentially damaging foreign matter. The sensor
utilxzes toughened and ruggedized outer jacket surface, and may require
a perforated or slotted pipe mounting for effective stilling action,
without interrupting the flow to the sensor face. This is included in
"METRIPIPE" systems.
The SigCon 700 series signal-converter instruments convert the
2-terminal resistance output of Metritape or Metritemp sensor to any one
of a number of standard voltage or current forms, such as 0-1 VDC,
VDC, 4-20 mA, etc. These instruments are normally line-powered, but
can be battery-powered for special remote operation. Output of the sis-
nal converter can be used to drive analog or digital indicating meters,
strip-chart recorders, pulse-code transmitters, or central readout and
alarm consoles.
SPECIFICATIONS:
Metritape
Sensor Type
Standard LS
Stabilized LS/S
Standard MPLS
Stabilized MPLS/S
Norn. Pitch
(turns/foot)
24
24
43
48
Active
Lengths
10-110 ft
5-15 ft
5-110 ft
3-15 ft
Norn. AD*
(feet)
0.4-0.6**
0.3
0.3-0.5**
0.25
Avg. Devi a.
(feet).
±0.1
±0.06
±0.05
±0.03
Repeatability
(feet)
±0.05
±0.03
±0.025
±0.015
** AD is governed by sensor length; increased to accommodate max. static head of longer sensors,
297
-------
PRICES:
Prices vary depending upon system specifications. As an example, a
MP/MPLS-10 "METRIPIPE" with a 3m (10 ft) operating range, a Signal
Converter 701A signal converter, and dry-writing strip-chart recorder
costs around $1,200.
COMMENTS:
The Metritape system may well find application in large, open-channel
flow measurements as a secondary device in conjunction with suitable
head-area primary devices. Its rather high activation depth precludes
its use in smaller flows. It has apparently worked well in a number
of combined sewer installations.
298
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MANUFACTURER: MOORE PRODUCTS.COMPANY
SPRING HOUSE, PENNSYLVANIA 19477
.TELEPHONE (215) 646-7400
PRODUCT LINE: FLUIDIC FLOWMETER AND ACCESSORIES
DESCRIPTION:
Flowmeter - The SSPH fluidic flowmeter is a unique flowmeter consisting
of a meter body, sensor, and a Q/I converter. The meter body is a
fluidic oscillator whose frequency is linear-with volume flow rate
The oscillations are detected by a flush-mounted sensor and are ampli-
fied and conditioned by the electronics to provide a digital pulse out-
put for totalizing and an analog output linear with flow rate The
geometric shape of the meter body is such that, when flow is initiated,
the flowing stream attaches itself to one of the side walls by means of
the Coanda effect. A small portion of the flow is diverted through a
feedback passage to a control port (Figure A). This feedback flow,
acting on the main flow, diverts the main flow to the opposite side wall
where the same feedback action is repeated (Figure B). The result is a -
continuous self-induced oscillation of the flow between the sidewalls
of the meter body. The frequency of this oscillation is linearly
related to the fluid velocity and, hence, volume flow rate.
side wall
control port
, feedback passage
Figure A
Figure B
299
-------
As the main flow oscillates between the sidewalls, the velocity of the
flow in the feedback passages cycles between zero and maximum. The
feedback passages thereby provide a region with a substantial f1owrate
change in which to sense the frequency of the oscillating fluid in the
meter body. This substantial variation in feedback flow xs easily and
reliably detected and results in a relatively noise-free sensor signal
which is very strong (several hundred millivolts before amplification).
The ruggedized, totally metal enclosed sensor (thermister) is further
proteSS by being located in this region which is out of the main flow
path. The flow and no-flow conditions at the sensor tip create cor-
responding high and low heat transfer conditions between the thermistor
and ?he fluid which, in turn, cause the self-heated thermistor to tend
to vary its resistance.
COMMENTS:
This interesting device is rather new on the market place and is avail-
able only in small sizes, up to 10 cm (4 in.), as yet. Its good ac-
curacy30:1 rangeability, low pressure loss, and other advantages make
it attractiveTor measuring pressurized flows in pipes No information
is available on coating effects of sewage on the thermal sensor, but
they could be minimal. Clogging or plugging of the feedback passages
could be a severe problem and, for this reason, no further descrxption
will be given.
300
-------
MANUFACTURER: HUESCO, INC.
WESTERN DIVISION
674 N. BATAVIA STREET
ORANGE, CALIFORNIA 92668
TELEPHONE (714) 997-5860
PRODUCT LINE: PROPELLER METERS AND ACCESSORIES
DESCRIPTION:
Muesco offers a complete line of magnetic drive propeller meters under
the "Rate A Flow" trade name. Included are Model TTM main line threaded
tube meters, Model FHM fire hydrant meters, Model FTM flanged tube
meters, Models GIFT and FST main line meters, Model SSC saddle meters,
and Model ISM insertion meters. All of the foregoing were designed for
use with water (or relatively clean liquids) and do not appear suitable
for measuring wastewater flows.
Model OFM is an open flow propeller meter designed for open channel or
submerged pipe outlet use. Available in 25.4 to 91.4 cm (10 to 36 in.)
sizes, it features a three-bladed, non-fouling propeller molded from
polyethelene plastic, a magnetic coupling, and bronze gear box. The
meter transmission is completely sealed and permanently lubricated.
Accuracy may be within ±2% if meter is used properly.
Model RC100 is an instrument that combines all features of a 30.5 cm
(12 in.) diameter recording chart, full size indicator scale, and
totalizer. A hermetically-sealed switch in the meter register-
transmitter completes a pulse rate proportional to the rate of flow
through the meter. This signal can be transmitted, for example, over
leased telephone pairs, and is suitable for multiplexing. Chart drive
is either 24 hour or 7 day rotation.
SPECIFICATIONS:
Model RC100
Accuracy:
Range:
Power:
Output:
PRICES: Model OFM
Model RC-100
±1% of full scale
24 to 1
11 VAC ±10%, 60 Hz
Optional 4 to 20 mA through 150 ohms
$340 - $425
$925
301
-------
COMMENTS:
The open flow meter may find some application as a current meter for
measuring storm or combined sewer flows. It does not appear suitable
for unattended operation over appreciable periods of time.
302
-------
MANUFACTURER:
NB PRODUCTS, INC.
35 BEULAH ROAD
NEW BRITAIN, PENNSYLVANIA
TELEPHONE (215) 345-1879
18901
PRODUCT LINE: PORTABLE MANHOLE FLOWMETERS; V-NOTCH WEIRS; ROD GAGES'
DESCRIPTION:
NB offers a line of portable float-in-flow flowmeters, portable V-notch
weirs, and a^rod meter (termed the FLO-ROD) for manual measurements of
volumetric flow. Figure A shows a typical meter (Model H) installed
in a manhole.
Figure A
303
-------
flowmeters
Series F Manhole Meter - This portable device consists of two basic
parts - a transducer (Figure B), equipped with a telescoping support
and ball float, and an instrument case containing a control box and
strip chart recorder. A sensing unit inside the transducer determines
changes in the water level in the channel by measuring the angle of
Inclination of the float arm (the ball float contacts the water in the
channel). This information is then transmitted over an electrical cable
to the recorder in the instrument case. Here, a continuous record of
the elevation of flow passing through the manhole is made on pressure-
sensitive chart paper. The recording, which runs at a uniform rate for
up to 30 days, is unaffected by changes in temperatire, grease, etc.
Longitudinal lines on the tape are used to show elevation of flow in
percentage of pipe size, and cross lines indicate elapsed time in
15-minute intervals. In order to translate the tape recordings into
—---Trim"
Telescoping support
. L" ihapecl «tid« fit?J
1 against top of ontwring.
1
•4
?p^™^
• VI
Electrical cable to
ihsturment box
THE TRANSDUCER
Figure B
gallons per 24 hours passing through the manhole, it is necessary to
first determine the slope of the pipe. Available with each meter is
a set of tables that can be used to convert elevation into rate of
flow.
304
-------
These meters are normally available for use in pipe sizes ranging from
20.3 to 111.9 cm (8 to 48 in). Since adjustment to various pipe sizes
is accomplished by different length float arms, one.basic unit can be
used. Arms for pipes up to 1.8m (6 ft) are also available. The unit
can be installed by one person in about 15 minutes.i A Series G meter
is offered at the same price and is virtually identical to the Series F
except that the ball float is replaced by the scow float used in the
Series H meter.
The power pack consists of four 7-1/2 volt rechargeable batteries that
will power the meter for approximately 9 days on a single charge.
Weekly charging is recommended, and a spare set. of, batteries and a
charger are included with each meter.
Series-H Manhole Meter - This device uses a float-in-flow transducer
similar to the Series-G flowmeter. One of the chief differences is
that this model is programmed to account for the well-known variation
in "n" (the Manning roughness coefficient) with flow depth in a circular
pipe. This is especially important for low flows (under 25% of pipe
diameter) and can result in accuracy improvements on the order of
20-30%. A solid state totalizer with L.E.D. display features no moving
parts. The total maximum flow rate for the pipe at the site of interest
is determined from NB tables and entered via a digital thumbwheel switch
at the time of installation. All electronics are contained in a stain-
less steel submersion proof case. Two gel-cell batteries and a charger
are also included with each unit. Battery life is 9 days on a single
charge. A strip chart recorder is also provided as in the Series-G
meters. S^iap-in function boards adopt the Series-H meters for use with
a variety of weirs and flumes as well as circular pipes.
Weirs
NB produces portable V-notch weirs in several sizes specifically designed
to measure the amount of actual infiltration in newly constructed sewers
and for measuring small discharges. Figure C shows a typical weir in-
stallation in a pipe.
V-notch weirs produced by NB are so designed that they can be installed
by one person without the use of any tools in any pipe (vitrified,
asbestos cement, concrete, or cast iron). Installation can be made in
less than one minute. The V-notch weirs are cast from weather resistant
aluminum alloy. The dial face is cut from transparent plastic and is
calibrated for direct reading in gallons per 24 hours. Individual weirs
are offered for six pipe sizes up to 38 cm (15 in). For larger standard
sizes to 106 cm (42 in), adaptors can be purchased to be used in con-
junction with the 38 cm weir (see Figure C).
305
-------
- i'i ^ ^ « - " 1 1
=; %•:, «• a as as
iiili1:i," 'ill,, i" /'i" ' ,jiii" i .iijri .iii'ipA,,1!!' ' iiiii'1'1' "»"" "imp
- :::: •••. • ::: :::: • - .-,••
Figure C
Rod Meter
The FLO-ROD is a four-sided measuring device of 2.5 cm (1 in) square
aluminum tubing calibrated on each side with a series of multipliers
for approximate flow determination. Inserted into the center of the
flow channel, a reading is taken at the water's surface. The volume
of flow is then calculated from a special set of tables provided.
Three FLO-RODs cover twelve pipe sizes, from 20.2 to 121.9 cm (8 to
48 in). Applications include: periodic checks of flows in sewers under
construction; quick checks for leaks and other troubles; and infiltration-
inflow studies.
SPECIFICATIONS:
Series-H Manhole Meter
Level Accuracy:
Total Flow Recording:
±0.0015m (±0.005 ft.)
999.999 units maximum
306
-------
Flow Rate Indicator:
Flow Rate Recorder
Size-Electronics Case:
Total Shipping Weight:
PRICES:
0-100% in 5% increments
0-100% in 2% increments
30.5x30.5x22.9 cm (12x12x9 in)
30.8 kg (68 Ibs)
Series-F & G Meters -
Series-H Meters - - - - -
Individual Weirs - - - -
Weirs Adapters - - - - -
Complete Weir Kit & Case
FLO-ROD
$2,100
$3,000
$20 - $44
$22 - $85
$400
$30 - $50
COMMENTS:
The NB manhole meters would appear to be useful for measuring sewer
flows at manholes over a limited range (many manholes will not allow
accurate measurement with the pipe over about half full); however,
these meters seem best suited for use with some better characterized
primary device such as a flume, open flow nozzle, or weir. The portable
V-'notch weirs may be suitable for their intended purpose, but lack the
range necessary for most flows of interest. The rod meters should only
be used for making rough flow estimates.
307
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MANUFACTURER: R. M. NIKKEL COMPANY
ROUTE 1, BOX B233
LIVE OAK AVENUE
OAKLEY, CALIFORNIA 94561
TELEPHONE (415) 625-3820
PRODUCT LINE: FLOW RATE TRANSDUCER
DESCRIPTION:
The BPN "FOTOFLOW" Series 800 flow rate transducer is a recently intro-
duced insertion type device for fluid monitoring in the water industry.
Although described by the manufacturer as an optical sensing type
transducer, the primary element is a freely rotating flow sensing
wheel. The wheel rotation is monitored by an optical sensor that of-
fers no impedance to the flow sensing wheel and is easily removable
from the line. A bi-directional capability is claimed over a nom- ^
inal 100:1 range; accuracy of ±1% of rate and repeatability of ±0.5%
are also claimed. Prices range from approximately $130 to $350 for the
basic transducer without accessories.
COMMENTS:
Manufacturer recommends unit for use in "reasonably clear" liquids. It
may find some use as a portable device for attended use in conducting
wastewater surveys, but does not appear at all sutiable for unattended
use in monitoring storm or combined sewer flows.
308
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MANUFACTURER:
NUSONICS, INC.
9 KEYSTONE PLACE ,
PARAMUS, NEW JERSEY 07652
TELEPHONE (201) 265-2400
PRODUCT LINE: SONIC FLOWMETERS
DESCRIPTION:
The NUSonics sonic flowmeter is a frequency difference type device de-
signed for full pipe flow. Typically, it consists of two transducer
assemblies, two mounting bosses, a transmitter and 15 feet of cable
from each transducer assembly to the transmitter. At the customer's
option, transducer assemblies may be supplied fully mounted in a flow
tube or supplied in kit form for purchaser to install in his own flow
'tube. The transmitter enclosure may be NEMA 12, NEMA 4, or explosion-
proof, at purchaser's discretion. An optional heater/thermostat for
the transmitter permits cold weather operation.
Transducer assemblies are mounted through the pipe in such a way that
they squarely face each other (Figure A) and are "wetted" by the liquid
to be metered. Thus, the sonic pulse is not distorted by a pipe wall
and is not subject to any refraction as it enters the liquid. It is
claimed that this provides the most reproducible "received pulse" wave
shape for best flowmeter performance. The transducers themselves are
piezoelectric ceramic disks, which are protected by a cover fabricated
from titanium or from an 8 to 10 mil Teflon coating over aluminum.
The sonic pulse can be successfully transmitted and received through a
surprising amount of organic or Inorganic build-up on the transducers.
Thus the NUSonics sonic flowmeter can function long after fouling has
incapacitated a meter with moving parts (e.g., turbine meter) or a
meter requiring electrical contact with the liquid (e.g., magnetic
flowmeter).
T6 further minimize the potential effects of fouling and/or corrosion,
the transducer assemblies may be provided with flushing ports (Fig-
ure B). Combined with Teflon-coated transducers, a periodic or con-
tinuous flush is particularly advisable for metering waste treatment
streams and solids-laden plant effluent. The manufacturer notes that
the NUSonics sonic flowmeter applies only to liquids or, in some cases,
liquids with solids in suspension. Entrained gas bubbles may inter-
fere. In general, the liquid must not excessively absorb and/or scat-
ter sound.
NUSonics sonic flowmeters are available in sizes from 7.6 to 122 cm
(3 to 48 in.) in fully assembled carbon steel, stainless and fiberglass
flow tubes. Also available is a sonic flowmeter kit from which pur-
chaser may convert his own pipe section into a sonic flowmeter in sizes
up to 1.8m (6 ft).
309
-------
FLOW
DIRECTION
Figure A
Figure B
310
-------
NUSonics sonic flowmeters use similar electronics for all sizes. Thus,
price increases relatively little with"size. NUSonics sonic flowmeters
are assigned meter factors based on precise transducer spacing measure-
ments which will yield an absolute accuracy within ±1%. Where re-
quired, NUSonics will assist in actual calibration at an independent
facility to achieve greater accuracy. Meter perforrnan.ee is independent
of the inherent speed of sound of the liquid being metered but does
vary with the shape and stability of the flow profile ia the pipe.
Variability for a given flow condition (repeatability)ris ±0.2 percent
of reading above a flow rate of 0.3 m/s (1 fps). Even better repeata-
bility can be achieved with flow straighteners. Variability due, to
changes in meter factor with flow conditions (linearity) will be only
±0.75 percent over any practical flow range (up to cavitation) for
Reynolds numbers over 100,000. Ranges of up to 100:1 may be achieved.
The NUSonics sonic flowmeter must be installed in straight pipe for
best performance. For turbulent flow, the above performance is based
on installations with the sonic flowmeter placed at least 20 pipe dia-
meters downstream and at least 5 diameters upstream of any elbow, tee,
or obstruction. Within shorter lengths, the device will yield cor-
respondingly wider errors.
Various flow totalizers, rate meters, and chart recorders are available
to receive the transmitter outputs (0-10 VDC; 4-20 or 10-50 mA.
PRICE: '.-•••
Prices vary with specifications, but an explosion-proof unit for a
20.3 cm (8 in.) pipe with remote readout costs under $3,000.
COMMENTS:
A major disadvantage of this unit for many wastewater installations is
the necessity for the transmitter to be less than 4.6m (15 ft) from the
flow tube.
311
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MANUFACTURER:
OCEAN RESEARCH EQUIPMENT, INC.
FALMOUTH, MASSACHUSETTS 02541
TELEPHONE (617) 548-5800
PRODUCT LINE: ULTRASONIC FLOWMETERS
DESCRIPTION:
O.R.E. Model 7000 ultrasonic flowmeters are custom designed to meet
each customer's application, and no standard product data sheets or
brochures can be prepared. However, O.R.E. feels that it has delivered
more of these devices for open channel flow measurement than any other
U.S. manufacturer. The following information was obtained by private
letter and telephone communication.
Basically, the. Model 7000 ultrasonic flowmeter can be used either to
measure line velocities along a single acoustic path or to measure
total flow in either open or closed conduits over four or more acoustic
paths and integrating the line velocities. The basic electronics pack-
age can handle a wide range of transducer frequencies (depending upon
path length) and can sequentially compute total flow for up to four
separate meter sections.
Most of the open-channel systems have been applied to rather large
flows, e.g., Columbia River at Grand Coulee Dam, Willametta River at
Portland, Oregon, etc. A typical installation near Hemet, California
measures an inlet canal to Lake Skinner. This system gives the volume
of flow directly by integrating the velocities from up to nine pairs
of sensors (depending upon depth).
Systems can be provided for use in-manholes, but 110V power is re-
quired. Unattended operation of two weeks is typical, at which time
a paper tape is changed. Very little maintenance is required, and it
will be about one year before any failures occur that would require
significant repair. The electronics package is designed, to withstand
and operate over a 0°-50°C (32°-122°F) temperature range.
Some error (10-15%) can be expected at very low velocities, e.g.,
0.03 m/s (0.1 fps), but the systems are quite accurate over the veloc-
ity range of 0.15-15 m/s (0.5-50 fps). Meters have been tested in
0.6m (2 ft) and 1.2m (4 ft) pipes in the Alden Research Laboratories
of Worcester Polytechnic Institute with accuracies of better than 1%.
PRICES:
Pricing of systems is based upon the particular design for a given
application, but a four-path system flowmeter would cost between
$20,000 and $40,000.
312
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MANUFACTURER: THE PERMUTIT COMPANY ......
DIVISION OF SYBRON CORPORATION
E49 MIDLAND AVENUE
PARAMUS, NEW JERSEY 07652
TELEPHONE (201) 262-8900
PRODUCT LINE:
PRIMARY DEVICES -VENTURI TUBES, FLOW TUBES, PARSHALL;FLUMES, PARABOLIC
OPEN FLOW NOZZLES
SECONDARY DEVICES - TRANSMITTERS, RECORDERS, TOTALIZERS
DESCRIPTION:
Permutit, a division of Sybron Corporation, manufactures a line of both
primary and secondary devices for flow measurement. The primary de-
vices include both standard and inexpensive venturi tubes, fiberglass
Parshall flumes, parabolic open flow nozzles, and a patented flow tube
known as the Permatube. Permutit also offers a variety of secondary
instruments such as the float-in-flume transmitter used with Parshall
flumes, electronic and telemeter transmitters, recorders, and
totalizers.
Venturi Tubes - Tubes specifically designed for sewage, sludge, and
trade wastes are the types VS, VTJ, and CTJ. These tubes are differ-
ential pressure metering devices for installation in closed piping
systems. Types VS and VTJ have low head loss - less than 22.4 cm
(9 in.) of water at maximum flow when used with a 10:1 range meter.
A claim made for the types VS and VTJ is that metering by these devices
is the least affected by upstream disturbances than by any other
differential-pressure device. The simplex type CTJ Venturi tube is a
one piece construction device of cast iron which minimizes manufactur-
ing costs and comes in a variety of sizes to meet most flow require-
ments.
The Type VS and VTJ tubes (Figure A) are similar in construction to
the type VT (cast iron with bronze throat liner) but have special
design features which make them suitable for sludge and sewage. The
type VS design includes a clear water flushing disconnector, four
manual cleaning valves at both the main and throat sections (which may
also be operated pneumatically or hydraulically), and cleanout holes
at top and bottom of each annular pressure belt. This protects
against fluids containing sediment or substances which may tend to
clog the piezometer openings. Continuous backflushing is available as
an option. This single-tap, type VTJ has pressure belts at the main
and throat which contain a bushing which permits the use of only one
piezometer tap and cleaning valve at each of these locations; thus,
313
-------
uisr
TYPE VS -r- FOR SEWAGE
TYPE VTJ - FOR SLUDGE
CTJ TUBE
PLAN VIEW
Figure A
314
-------
anti-clogging protection is provided against sludge or floating
particles.
The less expensive CTJ design provides for single taps at the main and
throat connections, and a bronze throat liner. A hand-operated bronze
cleaning valve is located at each pressure connection.
Flow Tubes - Perinutit has developed the Permutube, (patent pending), a
flow tube which has many performance advantages claimed for it. Among
these are:
• Greater accuracy over wide operating range, achieved by
greater pressure differential at lower velocity, without
adversely affecting overall head loss.
Low overall head loss, measured as a percentage of
pressure differential.
Stable coefficient over wider operating range of veloc-
ities and pipe Reynolds numbers lower than that obtained
with any conventional venturi tube.
• Minimum laying length assures easier installation and
provides greater flexibility of location.
The key to this proprietary design is the ramp and throat design as
indicated in Figure B. It is available as an insert type, or with
flanged ends in a choice of materials and complete range of sizes.
Flanged end Permutubes are made of close-grained, high tensile
strength cast iron with a bronze throat liner. An annulus averaging
ring in the throat section ensures an accurate reading with only a
single tap in the main. Tube ends are standard 56.7-kg (125-lb.) or
113.4-kg (250-Ib.) flanges. Insert Type Permutubes are available
with reinforced polyester fiberglass tube body and cast iron holding
flange or body and flange of integral cast iron. Both types feature
a bronze throat liner, annular ring in the throat, and a single tap
at the main. Holding flange is made to fit virtually every style
pipe flange.
For sewage handling, the addition of cleaning and flushing valve may
not be necessary on the Permutube due to the self-cleansing effect of
the flow over the ramps on the Pitot openings. Where severe sludge
build-up is a possibility, cleaning and flushing valves can be
supplied.
Parshall Flumes - The Simplex Parshall flume (Figure C) is constructed
of polyester resin bonded glass fiber with reinforcing ribs to prevent
315
-------
Insert Type; Fiberglass; Cast Iron
Holding Flange, Bronze Lined
Throat
Insert Type; Cast Iron, Bronze
Lined Throat
I i . -I
Flanted End Type; Cast Iron
Bronze Lined Throat
ACCURACY' f
.I1'"
°-12 -
05 8
"06-
tn
£ * ~
5 n «
S-
w»M
..*•• tf-'T
lofce^-T Jr^~
*•* »Si5-*7£.
vj-^5
^^0<
P
-D
\
\
(V \
"V
Brand '
X" Tube
\ (From published data)
^ \,
ERMUTUBE^^ 2" ->-
ata base
*•
4 on tests using E
I
^-~ ^
' Permul
4 .5 .6 .7
BETA RATIO
.7
.7'
F
o
0
O
u'bes —
.8
FLOW COEFFICIENT
A
Beta rat
8" PERMUT
-I—
o - 51389
JBE
'
0.1 0.2 0.3
Pipe Reynolds Number-Millions
, 1 1 1 .!_
46 8 10 12 14 16 1B
THROAT VELOCITY FEET PER SECOND
Figure B
316
-------
DIRECTION
OF
REINFORCING
RIBS
CONCRETE
CHANNEL
REIN-FORCING
RIBS
GLASS FIBER PARSHALL
FLUME
Figure C
317
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warping, twisting, or buckling out of shape. The polyester resins
are very resistant to erosion from the passage of solids or abrasives,
making this flume suitable for sewage or industrial wastes flow. The
flume is manufactured in integral units.
Parabolic Open Flow Nozzles - Permutit also markets two types of
parabolic open flow nozzles, Types S and SFF. The Type SFF has largely
superseded the Type S, which featured its own integrally cast sediment
chamber, a gauge glass and setting scale (for calibration), and a
manual cleaning valve assembly at the tap location. The Type SFF
eliminates these features since its metering float arm rides directly
on the flow stream. Most installations are now constructed with a
transmitter in the pit, with the meter receiver located above the
metering site or at some distance away in a more protected location.
Both types are of cast iron construction and utilize the same principle
of operation. The interior presents a smooth transition from circular
to parabolic form, with no obstructions or pockets, straight inverts.
This permits a gradually increasing velocity through the nozzle, thereby
tending to provide a self-scouring action.
Float-in-Flume Transmitter - The Simplex float-in-flume transmitter
is designed to continuously indicate the flow of sediment-laden
liquids as it passes through a Parshall flume under gravity conditions.
A similar device is available for parabolic open flow nozzles. Liquid
flow is indicated by the direct sensing of the level of the liquids
within the flume; flow data are transmitted either electrically or
pneumatically to a remotely-located flowmeter.
The transmitter (Figure D) is mounted directly on the wall of the
Parshall flume. A corrosion-resistant "ski" type sensor (float) rides
directly on the surface of the liquid flow stream; it does not cause
disturbance on the surface of the liquid or excessive oscillation in
recording instrument. As the surface of the. liquid rises or falls,
depending upon the flow through the flume, the sensor changes its
position accordingly. This movement produces proportional angular
movement of the sensor arm and shaft on which it is supported.
For electric transmissions, the shaft arm angular movement is trans-
ferred to a stylus riding over a characterized cam which is corrected
for non-linearity. The resultant linear signal, proportional to flow,
is transmitted every 15 seconds, with a pulse duration varying from a
fraction of a second to approximately 12 seconds. Three seconds of
each 15-second period are required for the receiver to reset for the
reception of the next signal.
For pneumatic operation, the shaft arm angular movement is transferred
to a. shaft carrying a cam, characterized tojzhe head quantity relationship
318
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• • i'«
:•.**•!.
Figure D
o£ the flume. A pneumatic tracing device senses the profile of
this cam and transmits a linear, 3-15 psig pneumatic signal through
an amplifying relay to the receiver.
Advantages of this device include the following:
• Reduces installation space
Faster responses to flow changes
• Reduces material costs - eliminates stilling wells,
connecting piping and fittings, large float and
cable, back purge system, etc.
Other Transmitters - Several other types of transmitters are offered.
These include the Type K telemeter transmitter, which transmits an
electrical signal through a two-or four-wire system to one or more
systems, and the Type STRR transistorized, force-balance differential-
pressure instrument with a 4 to 20 mADC transmission signal for liquid
flow applications.
Recorders/Totalizers - These include a compact recorder which indicates
and records fluid flow on a rectilinear strip*chart and is actuated
319
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either mechanically, electrically, or pneumatically. Also offered
is the Type STR-3 electronic recorder (solid state receiver) which can
remotely record and indicate flow loss of head, pressure, etc. The
totalizer can receive differential signals (electrical, mechanical,
etc.) from the primary element.
SPECIFICATIONS:
Type CTJ Venturi Tube:
Flow capacities ranging from .2456 MLD
(.0649 MGD) to 37.6179 MLD (9.9968 MGD)
depending upon dimensions and type
meters used.
Weights ranging from 16.3 to 247 kg
(36 to 544 Ibs.)
Flow Tube's (Permutube): Refer to graphs in Figure B for
a comparison of accuracies, head loss,
and flow coefficients.
Parshall Flumes:
Parabolic Open Flow
Nozzles:
Throat sizes ranging from 7.62 to
121.92 cm (3 to 48 in.); lengths ranging
from 0.91 m to 3.27 m (36 to 131 in!.);
flexual strength of up to 21,000 psi.
Inlet Diameters (Type S) - 15.2 cm to
106.7 cm (6 to 42 in.)
Flow capacities (Type S) - to 10.295 MLD
(2.72 MGD) for 106.7 cm size.
PRICES:
Prices not available at the time of this writing.
COMMENTS:
These devices were thoroughly discussed in Section VI and will not be
commented upon here.
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MANUFACTURER:
PRODUCT LINE:
DESCRIPTION:
PLASTI-FAB, INC.
11650 S.¥. RIDGEVIEW TERRACE
BEAVERTON, OREGON 97005
TELEPHONE (503) 644-1428
FIBERGLASS PALMER-BOWLUS FLUMES, V-NOTCH
WEIR BOXES, AND PARSHALL FLUMES
Plasti-Fab manufactures several primary devices in a variety of sizes.
For example, Parshall flumes are available from 2.5 cm (1 in.) to
1.2 m (4 ft.) and with either 20.3 cm (8 in.) or 30.5 cm (12 in.)
floatwells attached to either side as provisions for remote stilling
wells. A head gage is molded into the side of all Plasti-Fab
Parshall flumes for visual checking of flows. A 2.5 cm (1 in.)
blow-out connection is also provided on the floatwell. All Plasti-
Fab Parshall flumes are heavily ribbed for free-standing installation,
and they may also be installed as liners in concrete. They feature
5 cm (2 in.) flanges on ends and top, with heavy angle bracing across
the top flanges. These basic devices were discussed thoroughly in
Section VI and will not be described further here.
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MANUFACTURER: POLCON, INC.
AN AFFILIATE OF CARL F. BUETTNER ^
& ASSOCIATES, INC.
5106 HAMPTON AVENUE
ST. LOUIS, MISSOURI 63109
TELEPHONE (314) 353-5993
PRODUCT LINE: FLOW TUBE
DESCRIPTION:
The POLCON flow tube is a primary metering element designed for the
measurement of wastewater flows in partially filled circular conduits.
The tube is furnished in segments for insertion into existing piping
systems through a manhole or other opening in the piping system. Fig-
ure A shows a typical flow tube installation.
1/4 MAYON TUBING
FURNISHED BY POLCON
TO AIR SUPPLY AND
INSTRUMENTATION
LOCAL OR
'REMOTE
READOUT
PERMANENT OR
PORTABLE
INSTALLATION
••PRECISION ORIFICE
Figure A
The POLCON technique of measuring flow is based on the establishment of
a fixed relationship between the depth of liquid flowing in a smooth
straight conduit and the rate of flow. In effect, it allows the
Manning friction factor "n" to be factory determined, and the "POLCON"
conversion tables account for its variability with flow depth. A uni-
form slope is also established. A precision orifice embedded in one
segment of the flow tube permits the depth of liquid flowing to be
measured by determining the air pressure required to overcome the
height of fluid.
"POLCON" flow tubes provide a smooth, continuous liner inside an
existing pipe and are sufficiently long to permit the bubbler to be
located downstream from the manhole at a point where the flow tube and
322
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hydraulic slope are normally parallel. They are fabricated and machined
in 30.5 cm (12 in.) long segments, eight of which are used in a normal
installation. For troublesome installations, only four segments can be
used, and at a sacrifice in accuracy. The entire tube is fabricated of
PVC. plastic, and "0" rings are placed on the exterior surface to prevent
short circuitry of flow.
"POLCON" portable flow tubes are supplied in sizes to fit 15.2 to
45.7 cm (6 to 18 in.) diameter sewer pipes as standard. Larger or non-
standard diameters can be supplied on request. On installations where
the nominal size "POLCON" wastewater flow tubes will not pass through
the standard manhole cover, "POLCON" offers large diameter tubes which
are installed as an integral part of the sewer. Large diameter tubes
are furnished in steel or ductile iron, epoxy lined for lasting service,
and fabricated as a single unit with no decrease in sewer diameter or
carrying capacity. These are used for new construction or where low-
cost wastewater flow measurements are required in existing large
circular sewers.
"POLCON" also offers a complete line of instruments compatible for use
with their wastewater flow tubes in both portable and permanent con-
figurations. All portable units are built with rugged, lightweight
fiberglass cabinets measuring 58.4 cm (23 in.) in diameter and 81.3 cm
(32 in.) high. Model PIP-100 is powered by an external air supply con-
nected to the built-in air control system. The cabinet contains a
rota/purge meter, a 15.2 cm (6 in.) spring-wound recorder covering
0-38 cm (0-15 in.) of water range. Model PIP-101 differs only by the
addition of a 14-day gas bottle that is locally refillable. Model PIP-
102 features an air compressor and electrically-driven recorder, arid
also requires a 110-VAC external power source. Model PIP-112 combines
the air compressor with a gas bottle back-up to avoid power failure
effects. Options include a 20.3 cm (8 in.) recorder and a 7 day or
24 hour recorder.
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SPECIFICATIONS:
Accuracy:
Flow Capacities:
Up to ±4%
POLCON
Model #
SFT/PFT - 6
SFT/PFT - 8
SFT/PFT - 10
SFT/PFT - 12
SFT/PFT - 15
SFT/PFT - 18
Sewer*
Dia.
6"
8"
10"
12"
15"
18"
Quantity in GPM*
Slope
1%
178
254
531
977
1575
3358
2%
251
360
751
1382
2227
4749
3%
308
440
920
1693
2728
5817
4%
356
509
1063
1955
3150
6717
4%
398
569
1188
2186
3522
7510
Metric Conversion Factors:
Inches x 2.54 s Dia. in centimeters (cm)
GPM x 3.785 = Liters per minute (LPM)
PRICES:
A total POLCON package (including an 8 to 10 inch-tube, sensor, and
liquid level recorder) costs approximately $2,000 - $800 for tube and
$1200 for sensor).
COMMENTS:
This device essentially provides a controlled flow section within the
sewer in which (hopefully) the Manning formula can be applied with
greater accuracy. Since slope-area methods such as this are not well-
suited for flow determinations in many storm or combined sewers, its
benefit would seem marginal at best.
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MANUFACTURER: PORTAC
MIN-ELL COMPANY, INC.
1689 BLUE JAY LANE
CHERRY HILL, NEW JERSEY 08003
TELEHPONE (609) 429-0421
PRODUCT LINE: CURRENT METER FLOW TUBES
DESCRIPTION:
PORTAC Flow Tube - The PORTAG Portable Sewer Conduit Flowmeter is a
patented device (Figure A) that has been used successfully by New York
City's Department of Water Resources Industrial Wastes Control Section
for sewer flow measurement. The meter, shown in the plan view of Fig-
ure B, is designed to create full pipe flow in the sewer conduit, thus
making the area of flow constant. (A self-damming flap gate, also
shown in Figure B, is provided for this purpose.) The only other
variable is velocity and this is measured with an OTT .current (velocity)
meter (shown installed in Figure C). The number of revolutions made by
the meter's propeller are totalized on a digital counter. By applying
the specific formula supplied with a particular system, flow totals
can then be calculated.
As shown in Figure B, suspended deflectors, which are removable, are
constructed immediately upstream of the current meter's propeller.
This is done to reduce or eliminate the possibility of damage to the
propeller by hard, fast-moving objects such as wood. The deflectors
also generally redirect pliable suspended materials, normally en-
countered in sewer wastes, away from the area around the propeller's
rotation. • .
Easily mounted on and suspended with a placement rod, the device can
be installed (or removed) by only two sewer workers, regardless of
manhole invert contours. Some of the hydraulic and physical advan-
tages claimed for the PORTAC flowmeter are:
• Velocity of approach is not a factor if a high velocity
propeller is used on the current meter;
Sewer grade may be any value;
• The system is as good or better than a flume or weir in
terms of ease of installation; the tube can also be easily
sealed to ensure that all flow is being gaged;
• The system is unaffected by surcharging or submersion;
and
325
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326
-------
BEFORE AND
DURING
INSTALLATION
METER IN
OPERATION
Figure B
327
-------
o
0)
-------
• The system does not need compressed air or AC power to
operate, and thus is truly portable.
The flowmeter is fully adaptable for analog metering as well as strip
chart recording. The standard metering package consists of: the flow
tube; an OTT Model 10.002 current meter; and a three-digit, battery-
operated counter model (F4). A five-digit counter (also battery
operated), Model Z100, with other monitoring features* is also avail-
able, at additional cost. An optional current meter for use with
PORTAC is the OTT Model 10.300 which has provisions for analogue strip
recording.
Current Meters - In the OTT 10.002 standard unit shown in Figure D,
signals are generated by means of a permanent magnet mounted on a worm
sleeve which completes the circuit by way of an impulse device embodied
in the meter following each revolution of the propeller. The device is
r
112.01
Figure D
* e.g., audible indication of input pulses by a loud buzzer.
329
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largely free of restoring forces and may be said to operate virtually
without power. The diameter and pitch of the propeller to be used is
determined by the maximum flow velocity of the water to be encountered.
A special table is provided to enable proper selection.
Counters - the three-digit F4 counter (type 12.000) counts a maximum of
10 pulses per second and is suited for operation with the OTT 10.002
(C31) current meter, which generates a signal pulse at each revolution
of its propeller. Two 1.5-volt "D" size batteries serve as the power
source and allow up to 48 hours of continuous operation without battery
replacement. A stopwatch is used in conjunction with this instrument.
The Z100 five-digit counter is capable of measuring the length of pulse
cycles from voltage-free transmitters (e.g., current meters), up to a
maximum of 20 pulses per second. It is powered by six 1.5-volt single-
cell batteries sufficient for about 30 hours of operation, assuming
8 hours of operation each day.
SPECIFICATIONS:
PORTAC Flowmeter (Less Current Meter and Counter)
Accuracy:
Line Sizes:
PRICES:
±3%, when velocity flow exceeds
.027 m/s (0.09 fps)
15.2 to 45.7 cm (6 to 18 in.)
Nominal I.D.
PORTAC (Less Current Meter and Counter)
PORTAC Complete with Current Meter and
Counter
Optional 5-Digit Counter (Z100)
COMMENTS:
$815-$915
$1150.00
$950.00
Although this unit has been used in some sewers, it does not appear
well suited for general storm or combined sewer applications, since it
must suffer all the deficiencies of a current meter and is available
only in small sizes.
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MANUFACTURER: RAMAPO INSTRUMENT COMPANY
MACOPIN ROAD
BLOOMINGDALE, NEW JERSEY 07403
TELEPHONE (201) 838-2300
PRODUCT LINE: TARGET-TYPE FLOWMETERS, RECORDERS, INDICATORS
DESCRIPTION:
The RAMAPO Instrument Company manufactures a flow meter probe (the
Mark V) which is reported to be widely used for measuring industrial
wastewater flows. The company also offers several other flowmeters,
including the newly-developed Mark VI target flowmeters, and a variety
of recording and indicating devices.
Mark V Flowmeter Probe - This device will>measure most process fluids
in pipelines. This is done by installing a flanged fitting into an
existing pipeline (see Figure A). The strain gage force sensing ele-
ment of this device has no bearings or other rotating parts. The
electrical signal can be transmitted to remote locations or used for
indicating, recording, controlling, and totalizing. The Mark V Flow -
meter measures flow in terms of the dynamic forces acting on a fixed
body in the flow stream. Bonded strain gages in a bridge circuit out-
side the fluid stream and shielded by stainless steel, translate this
force into an electrical output proportional to the flow rate squared.
A modification of the standard Mark V Flowmeter Probe, a retractable
probe, is also available for pipeline applications. This particular
device can be installed in or removed from pressurized systems without
causing a shutdown. The probe can be moved from line to line - even
for widely varying line sizes - for sampling or spot checking of flows.
Materials and specifications are generally the same as those for the
standard probe.
Other Flowmeters - Less suitable for effluent flow measurements is the
Mark V flowmeter for tube end and pipe connection applications. They
are usable with slurries and some types of abrasive fluids, however.
Accuracy is reported to exceed ±0.5 percent in flow ranges of approxi-
mately 10:1. Line sizes available are from 1.3 to 15.2 cm (0.5 to 6 in.)
with any standard end fitting, with special sizes supplied upon request.
The Mark VI Target Flowmeter is a new product which has been developed
for measuring flows of dirty liquids, slurries, etc. This flowmeter
has no moving parts and no cavities to collect particles or entrap
materials that can harden. Available in a wide variety of line sizes
and configurations, it has operational performance characteristics
similar to the Ramapo Mark V Target Flowmeter.
331
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Figure A
332
-------
Secondary Flowmeasuring Devices - Ramapo markets several recently-
developed recorders and digital flowmeters compatible with the Mark V
and Mark VI.
One type records flow on an inkless, 5.1 cm (2 in.) wide chart. Sig-
nals accepted are typically 0-1 volt or 4-20 mA. The scale and chart
use square root ruling so that the flow rate signals originating at
target meters, orifices, and other differential pressure devices can
be read directly in percent of flow. One chart lasts "30 days. Absolute
accuracy is ±2 percent.
Digital-reading flow indicators, with BCD output if desired, are avail-
able for reading in engineering units such as GPM, CFM, and H/s.
Depending upon the application, the display can present readings to a
maximum of 1999, 3999, or 19999.
SPECIFICATIONS:
Line Size*:
Calibration*:
Accuracy:
Range:
Materials*:
Pressure Loss*:
Input:
Output:
Connections*:
10.16 to 152.4 cm (4 to 60 in.)
±1%; 2%
±1% full flow (Bi-directional)
Any 10:1 range up to a line velocity
of 4.57 m/s (15 fps) maximum
Stainless steel sensing element;
Mounting flange as specified
Usually less than 10 cm (4 in.)
of water
5 to 10 VDC
Up to 20 mVDC maximum or 2.0 mVDC input
for full range flow rate. Semi-
conductor gages available for higher
output
Terminal strip in explosion-proof
enclosure, or submersion-proof head
and cable
Mark V Flowmeter Probe Only.
333
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PRICES:
Mark V Flowmeter Probes (Standard)
$745 to $1,195 (2% Calibration)
$960 to $2,300 (1% Calibration)
COMMENTS:
Although useful for some types of wastewater flows, these target-type
devices do not appear suitable for extended use in the storm or com-
bined sewer application. Their limited range and vulnerability to
impact by debris make all but attended, short-time use appear unfeasible.
334
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MANUFACTURER: ROBERTSHAW CONTROLS COMPANY
P.O. BOX 3523
KNOXVILLE, TENNESSEE 37917
TELEPHONE (615) 546-0524
PRODUCT LINE: PARSHALL FLUMES; CAPACITANCE TRANSMITTERS; RECORDERS;
INTEGRATORS; TOTALIZERS; ETC.
DESCRIPTION:
Robertshaw markets a variety of analytical and measurement devices,
many of which are designed for use with water and wastewater instrument
systems. Typical of these is the Series F-Flume Flow Measurement
System, which incorporates a circular chart recorder with optional in-
tegrator, or a panel-mounted recorder/totalizer.
Flume - The system (Figure A) utilizes as its primary measurement
device a Parshall "Free Flow" flume, constructed of polyester reinforced
fiberglass with Sanitary Satin finish. The flume is equipped with a
molded-in capacitance sensing probe that is characterized to provide a
linear output signal directly proportional to flow. The flume is a one-
piece, completely self-supporting unit ready for installation in con-
crete. A ruggedized model may be installed in conduits above the ground.
The flume and its associated instrumentation are suitable for many open
channel applications.
Transmitter - A capacitance sensing transmitter (Figure A) can be
installed directly on the flume probe (Model 157), or mounted in a loca-
tion remote from the flume. No stilling well is required. Because there
are no floats, moving parts, or mechanical linkages, performance is
enhanced.
Flow Recorders and Integration/Totalization - Flow recording and inte-
grating/totalization may be provided with the Series F system using the
Model 241 circular chart recorder with optional integrator, or the
Model 225/534 recorder/totalizer for front panel flush mounting.
The Model 241 electronic circular chart recorder is available in single
or two pen versions in a weathertight enclosure for surface or panel
mounting. Optional features include built-in integrator-totalizer and/
or square-root extractors.
The Model 534 Integrator-Totalizer provides continuous integration and
totalization of process signals with respect to time. Ratio adjust-
ment is by means of a long-scale, thumbwheel dial, calibrated for
linear or square-root signals. A vertical scale meter displays input/
output signals.
335
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MODEL 157
Free Flow* Flume
Figure A
336
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The Models 157/158 Level Tels (transmitters) are capacitance sensing
instruments producing standard output current signals and are used
for continuous level indication or control.
SPECIFICATIONS:
Output-. Signal:
Linearity:
Repeatability:
Power:
Input Signals:
Accuracy:
Repeatability:
Pen Response:
Power:
Input Signals:
Accuracy:
Repeatability:
Count Rate:
Power:
PRICES:
Model 157/158 Transmitters
1 to 5, 4 to 20, 10 to 50 mADC
±0.25% of full scale
±0.1% of full scale
117/230 VAC or 26 VDC
Model 241 Circular Recorder
1 to 5, 4 to 20, 10 to 50 mADC
±1.0% of full scale
±0.2% of full scale
2 to 20 sec., adjustable
117/230 VAC, 50-60 Hz
Model 534 Integrator-Totalizer
1 to 5, 4 to 20, 10 to 50 mADC
±0.375% of full scale
±0.1% of full scale
1000 to 20,000 CPH
117/230 VAC or 26 VDC
Not available at time of writing.
COMMENTS:
The capacitance gage molded into the Parshall flume offers advantages
for some applications. Parshall flumes were thoroughly discussed in
Section VI and will not be commented on further here.
337
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MANUFACTURER:
SARATOGA SYSTEMS, INC.
10601 SOUTH SARATOGA-SUNNYVALE ROAD
CUPERTINO, CALIFORNIA 95014
TELEPHONE (408) 257-7120
PRODUCT LINE: ULTRASONIC FLOWMETERS
DESCRIPTION:
Saratoga Systems Inc., under licensing agreement with Lockheed Aircraft
Corporation, has patented and is producing the "ULTRAMETER", a fre-
quency difference type "ultrasonic" flowmeter which combines sonar and
advanced micro-electronic concepts to measure the flow of any medium
capable of providing a uniform flow profile and propagation sound
waves in an undistorted manner. This device has a number of applica-
tions in the wastewater field.
The Model 201 Ultrameter provides either an analog output, or a digital
output that is directly proportional to the average speed of a fluid
flowing in a pipeline and which can be related to volume flow rate. The
measurement system, which employs a pair of non-intrusive diagonally-
opposed transducers mounted directly on the pipe itself (see Figure A),
is independent of the sound speed in the fluid as well as fluid density,
composition, viscosity, and temperature.
Sound "bursts" are propagated alternately in opposite directions between
the two transistors. Because the upstream signal is delayed and the
downstream signal is speeded up by the moving fluid, the alternate
bursts yield a frequency difference which is a highly accurate measure-
ment of the flow (to 0.2%). The measurement also provides linearity
even at very low flow rates.
Analog current or digital pulse trains are both simultaneously avail-
able from the "ULTRAMETER", and can feed directly to recording and
computing equipment. These data signals can be scaled to any desired
output dimensions, such as GPM or cubic feet per minute.
Features include:
• Bi-directional flow measurement capability
• No head loss or obstruction to flow
• No moving parts
• No recalibration after initial factory or inplace
calibration
338
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Axial flow section, useful for pipe sizes from
1/e inside diameter to 3" inside diameter.
Ultrameter transducer receives and emits sound waves.
Figure A
100 percent Solid State electronics including replaceable,
interchangeable modules and an automatic failure•alarm
system
The flowmeter may be employed in pipelines ranging from 7^62 cm (3 in.)
diameter pipes to open channels.
339
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SPECIFICATIONS:
A,typical 9 cm (4 in.) meter flowing 757 Jl/m (200 gpm) has the fol-
lowing performance and operational characteristics:
Accuracy:
Resolution:
Ranges:
Tipper Flow Limit
Lower Flow Limit
Data Format Options:
Digital
Analog
Power:
Size:
Standard Meter Bodies
w/ Transducers
Weld-on Transducer
Installations
Weight:
Instrument Package
Transducers (depending
on installation)
±0.5% (full scale error with
calibration)
±0.2% (full scale)
100 x Full Scale
0.1 x Full Scale
Positive true logic, TTL compatible
pulse train proportional to flow.
0.5% D/A conversion
Current Source 0-1, 4-20 or 10-50 mA
(Full Scale)
Voltage Source ±1 or 0-5 volts
(Full Scale)
117 VAC, 50-60 Hz @ 1 amp
0.32 to 46 cm (0.125 to 18 in.)
10 cm (4 in.) up
27.2 kg (60 Ibs)
42.5 g to 9 kg (1.5 oz to 20 Ibs)
PRICE:
Typical price in 20 cm (8 in.) size with remote read-out is $3,680.
COMMENTS:
A large quantity of particulate matter (as can be found in raw or un-
treated sewage) or heavy concentration of air bubbles can affect the
system, although it is reported that up to 50 percent concentrations
of solids have been handled. These factors have to be determined in
advance consultations with the manufacturer.
340
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There is no restriction on the transducers, but the line has to be full
of liquid. The electronic control box can be mounted in any orientation
except upside down, but must be within 15m (50 ft) of the transducers.
This distance can be extended to 30m (100 ft) under special circumstances.
Overall accuracy of this ultrasonic device depends to a certain degree
on the stability and definition of the fluid velocity within the meter
path. In some circumstances (e.g., in large diameter pipes and open
channels), the flow velocity profile is unstable. Several statistical
averaging techniques, such as the Gaussian integration method, can be
used with the "ULTRAMETER" to improve accuracy. However, these tech-
niques are complex and involve additional expense.
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MANUFACTURER: SCARPA LABORATORIES, INC.
46 LIBERTY STREET, BRAINY BORO STATION
METUCHIN, NEW JERSEY 08840
TELEPHONE (201) 549-4260
PRODUCT LINE: ACTIVE AND PASSIVE ACOUSTIC FLOWMETERS ^
DESCRIPTION:
Scarpa Laboratories currently manufactures a line of ultrasonic flow-
metering and sensing instruments which cover a wide range of liquid
and gas applications. Those meters appearing to be best suited for
wastewater applications are the non-contacting, clamp-on passive
acoustic SFM/SFS Series (2, 3, 4, 5) meters (these are the least ex-
pensive) and several more expensive models (e.g., Type II SDL-10,
Type IV SDL-8, etc.) that utilize the time difference principle and
digital computer technology.
Passive Flowmeters - These clamp-on flow indicators utilize the acoustic
emission principal and appear to be usable for liquids, solids, gases,
and slurries. All models in this series read relative velocity for
liquids and gases and relative mass flow for slurries and solids. The
"SCARPA-SONIC" device responds, through a microphone, to broadband noise
generated by the moving medium - noises which range from the audible to
the high ultrasonic spectrum. Filters are provided to eliminate
spurious sounds from sources other than the flowing material. In the
cases of liquids and gases, the signal produced is an analog output
which is a function of flow velocity; for slurries and powders, it is
a function of mass velocity. The sensor element clamps or bonds to the
outside of the pipe wall, and the manufacturer states that their best
sensing locations are at elbows or flanges. It is further recommended
that they should be located at least 3m (10 ft) away, and preferably as
far away as possible, from pumps or compressors as they may introduce
spurious signals that could pass through the receiver band-pass filters.
Very low flow velocities (e.g., slurries) may be sensed by imposing some
form of "flow spoiler" in the stream such as an orifice, pipe constric-
tions, or even any small projection which does not have to have
rotational symmetry.
This meter may be used for any pipe size, ranging from 0.31 cm (1/8 in.)
O.D. copper tubing to 305 cm (120 in.) or larger pipe diameters. Milli-
volt, milliampere, and relay contact closure outputs are available. The
meter must be calibrated at the site of installation.
Active Flowmeters - The Scarpa active ultrasonic liquid (called
"doppler") flowmeter indicates flow by means of two transducers either
clamped on the opposite outside walls or inserted through the walls of
342 '
-------
any pipe size from 7.61 to 152.4 cm (3 to 60 in.). The instrument
transmits and receives ultrasonic signals through the pipe wall and
across the flow stream at an angle to the flow. The actual measurement
is of velocity and is transformed to volumetric flow by means of con-
version tables that correct for pipe wall thickness and internal
diameter. Units for a specific pipe size can be factory calibrated
to read directly in GPM.
Applications range from non-intrusive flow surveys to flow measurement
and control where the non-liquid contact feature is essential. The
electronics are housed in an industrial grade Nema 4 gasketed box with
hinged door.
The doppler type units all employ digital computer technology in
processing the information obtained from the ultrasonic "front end.*'
BCD or binary outputs can be provided, as well as 0 to 10 volts, 4 to
20 mA or 10 to 50 mA analog outputs. Digital flow rate displays are
also available as standard equipment.
All transducers are metal encased and transmit and receive through
resonant metal "windows." As such they can withstand high pressures
and most corrosive environments. Materials of construction may be
aluminum, titanium, monel or stainless steel. Explosion proof housings
are available at additional cost.
SPECIFICATIONS:
Range:
Accuracy:
Reproducibility:
Power:
Temperature Range:
Series SF-( ) Flowmeters
0.3-1.5 m/s (1-5 fps) to sonic
velocities*
Calibrated in place
±1%
117 VAC, 1/10 Amp, 50/60 Hz
9-V Battery Power available some models
-40° to + 150°C (Sensor)
-40" to + 80°C (Receiver)
"Ultrasonic Liquid Doppler Flowmeters (Typical)
Range: (Flow velocity) 0.3 to > 9 m/s (1 to > 30 fps)
Accuracy: ±2%
0-100 yA meter indicates relative flow velocity.
on site to indicate actual flow rate.
May be calibrated
343
-------
Repeatability
PRICES:
SFS-2-RPS
SFM-3-BP
SFM-4-RPS
SFSM-5-RPS
TSL-2-( )
Type SDL-10
Type SDL-8
COMMENTS:
±2%
SF- Series Flowmeters
Ultrasonic Clamp-On Flow Switch,
with Regulated Power Supply.
Ultrasonic Clamp-On Flow Meter,
Battery Powered
Batteries - $2.75 each extra
(2 required)
Ultrasonic Clamp-On Flow Meter,
with Regulated Power Supply.
Flow Switch, Flow Meter Combination
with Regulated Power Supply
Clamp-On Flow Sensors-Transmitters
(Note: At least one TSL-2-( )
sensor is required with each
receiver)
Ultrasonic Liquid floppier Flowmeters
(Clamp on unit)
("Wetted" sensors)
, $181.50
$330.00
$341.00
$467.50
$ 93.50
to
$165.00
$3,500-$5,000
$3,500-$10,000
Scarpa offers the only passive acoustic flowmeters on the market today,
but little is known about their use in a storm or combined sewer
application.
344
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MANUFACTURER: SIGMAMOTOR, INC.
. 14 ELIZABETH STREET
MIDDLEPORT, NEW YORK 14105
TELEPHONE (716) 735-3616
PRODUCT LINE: BUBBLER-TYPE SECONDARY FLOWMETER
DESCRIPTION:
Sigmamotor has recently introduced their LMS-400 battery operated,
open channel flowmeter. It is a bubbler-type secondary device in which
a pressure transducer senses the back-pressure experienced by an inert
gas which is bubbled at a constant flow rate through a tube anchored
at an appropriate point with respect to the primary device (weir,
flume, etc.). The flow depth is thus determined and electronically
integrated into the appropriate flow equation. Appropriate numeric
values for the rest of the flow equation are set with two dials on
the front of the meter.
The device appears to be extremely simple to set up and put into opera-
tion. It can operate up to 122m (400 ft) from the measurement site.
This unit, which is claimed to be one of the smallest and most accurate
flowmeters available, is equipped with a 31-day pressure sensitive strip
chart recorder for a continuous record of flow rate and a six digit
totalizer reading in gallons to indicate total flow over time. Besides
the flow rate readouts in CFS or MGD, the LMS-400 can be set to simply
give depth readouts in either feet or inches. It is also designed to
supply a flow-proportional signal for an automatic sampler and will
indicate at what time each individual aliquot was taken.
SPECIFICATIONS:
Accuracy:
Power:
Battery Life:
Bubbler Cylinders:
Dimensions:
Weight:
±2% from the theory curve of the
primary device
AC units, 115V
DC units, 12V Lead Acid Type Battery
30 Amp-Hour - 10 days
15 Amp-Hour - 5 days
0.9 kg (2 Ib) Freon R-12 gas cylinders
(two) last for approximately 3 to
4 weeks
34.3x36.8x25.4 cm (13.5x14.5x10 in.)
15.9 kg (35 Ib) with 30 Amp-Hour
Battery
11.8 kg (26 Ib) with 15 Amp-Hour
Battery
8.2 kg (18 Ib) AC model
345
-------
PRICES: $1,750 for AC-DC Unit
COMMENTS:
This small, versatile unit appears to be well suited, in conjunction
with appropriate primary devices (linear, 3/2 or 5/2 power), for many
wastewater flow surveys. Its complete portability makes it especially
attractive for such use. Wide range requirements could pose a problem;
although the unit has four range settings, they must be set manually.
346
-------
MANUFACTURER: SINGER-AMERICAN METER DIVISION
13500 PHILMONT AVENUE
PHILADELPHIA, PENNSYLVANIA 19116
TELEPHONE (215) 673-2100
PRODUCT LINE: PARSHALL AND PALMER-BOWLUS FLUMES; LIQUID LEVEL GAGES
DESCRIPTION:
The American Meter Division of Singer offers,Parshall flumes in sizes
from 7.6 to 30.5 cm (3 to 12 in.) as standard and up to 2.4m (8 ft) on
special order. The flumes are heavily ribbed for free-standing instal-
lations and may also be used as liners in concrete. They are fabricated
in one piece from polyester plastic resin, reinforced by glass mat not
; less than 30 percent by weight, and have a smooth white -surface. A con-
nection is available on either side for a bubbler pipe, and a head gage
is molded into the side of the flume. For installation in pipelines,
American also offers Parshall flume end adaptors to make the transition
from round pipe to rectangular flume and back to round (Figure A).
Short-section flumes (i.e., no diverging section), are available for use
where space is restricted and the additional head loss is tolerable.
The Palmer-Bowlus flumes offered by American feature a trapezoidal sec-
tion with a flat bottom. Recommended installation techniques include
grouting or adhesive bonding. They are also molded from fiberglass-
reinforced isophthalic polyester resin with a white gel coat interior
surface. The outside surface has clips for anchoring to concrete. The
flume includes a built-in stainless steel bubbler tube.
American offers a number of secondary elements (Figure B) for use with
V-notch weirs, rectangular weirs, Parshall flumes, and Palmer-Bowlus
flumes. Spring-wound, battery, or electrical (110 VAC) chart drive
speeds can be either 24 hours or 7 days per revolution. Integrating
instruments use electrical drive charts.
The American bubbler tube level system utilizes an air pump to pressur-
ize a capsular pressure element. A tee is incorporated in the line
leading to the capsular pressure element to bleed off a continuous flow
of air (back pressure at the capsular pressure element) to the dip tube.
The dip tube is open at one end and submerged, for example in a weir
with the open end on a plane with the bottom of the weir notch. The
air escaping from the open end of the dip tube produces bubbles (air
pump is adjusted to produce approximately 30 to 90 bubbles per minute);
thus, the air pressure in the dip tube corresponds to the hydraulic head
of the liquid. As the liquid head varies, the pressure in the tube
changes. This tube pressure is proportional to the pressure variation
at the capsular pressure element. Here the movement of the capsular
pressure element is transmitted to an integrating stylus and recording
pen arm which accurately records a pattern of liquid flow. The inte-
grating instrument totalizes the actual volume measured. The integrat-
ing mechanism is a rotating cylindrical cam with a surface corresponding
to the weir notch characteristic. Depending upon the position of the
pressure stylus, the cam actuates the counter drive for a portion of
each revolution. Since all functions are performed by special gearing,
there are no-clutches to cause backlash or slippage.
347
-------
CAULKING
SLEEVE
Adapters Bolt To Each
« End Of The Flume With
Stainless Steel Bolts.
• Slope With Grout
After Installation
EXISTING PIPE LINES
Usually Require The Pipe Invert
To Be Below The Flume Entrance.
ON NEW PIPELINES
The Inlet Pipe Invert Should
Be At Same Elev. As The Flume.
CAULKING COLLARS
Sized 1 "-2" Larger Than
The Pipe To Allow Movement
For Leveling Flume.
[—OUTLET PIPE
Must Be At
Same Elev. As
Flume Outlet
Or Lower.
STANDARD INLET AND OUTLET ADAPTERS
FOR PARSHALL FLUMES
INLET
End Connections, such as caulking collars, are not shown as size and type may vary.
Fi$f
3"
6*
9*
12*
18*
24"
A
l'-6"
2'-0*
2'-8*
3'-9*
4'-4"
5'-0*
B
12"
l'-6"
l'-9»
2MT
2MT
2'-6"
C
9"
r
8"
10"
10"
7"
D
r-6"
2'-0"
2'-0"
2'-9"
3'-4"
4'-8?
E
• 9"
7"
8"
8"
8"
l'-4"
F
12"
l'-6"
l'-9» -
2'-0"
2'-0"
2'-6"
G
3'-0"
5'-0"
5'-4"
9'-4%"
9'-7%"
9'-10J4"
H
5"
6"
6"
.7"
8"
8"
1
4"
3"
4"
4"
5"
5"
Figure A
348
-------
r
-RECORDING ONLY
-RECORDING & INTEGRATING
r-RECORDING & INTEGRATING
WITH TELEMIKE TO OPERATE
REMOTE COUNTER
[-INDICATING TELEMETER
TRANSMITTER !
J r—™^=
SUBUERGE001PTUBE
IS LEVEL WITH THE
BOnOM OF WEIR NOTCH
TELEMETER RECEIVER
RECORDING ONLY
Figure B
349
-------
MANUFACTURER: SPARLING DIVISION
ENVIRONTECH CORPORATION
4097 NO. TEMPLE CITY BLVD.
EL MONTE, CALIFORNIA 91731
TELEPHONE (213) 444-0571
PRODUCT LINE: PROPELLER FLOWMETERS; TRANSMITTERS, RECORDERS, AND
INDICATORS/TOTALIZERS
DESCRIPTION:
Sparling Manufactures a variety of propeller-type meters, electromecha-
nical devices and controls, solid state instruments, and telemetering
equipment. Some of these are suitable, or are potentially acceptable,
for some wastewater and/or sewer flow applications. Of particular
interest are the Series 100 meters (Masterflow wastewater meters) and a
variety of electrical flow rate transmitters for use with flumes or
weirs or for mounting on meterheads to operate remote recorders, in-
dicators, and/or totalizers.
Sparling offers two styles of wastewater meters - the flanged Masterflow
tube type and the Masterflow Open Flow type (see Figure A) . For both
models, application in measuring waste flows is recommended only after
primary treatment, including waste or return activated sludge. These
meters are not recommended for raw sewage or primary sludge flows.
Therefore they will not be described further.
Secondary Measurement Devices - Secondary devices offered by Sparling
include the following:
. Pulse-Rate Transmitters - These designs utilize an optical
pulse-rate generator to provide a 0 to 20 PPS signal directly
proportional to flow rate.
. Electronic Transmitters - Measure and transmit level, pressure,
or other variables.Output signal accuracy is ±1%. Pulse
frequency; DC voltage, or current output modes.
. Miniature Strip-Chart Recorders - Indicate and continuously
record flow, pressure, level, or other variables. Can accom-
modate solid state or relay-contact output switches for
alarm, status indication, etc.
. Circular-Chart Recorders - Feature 30.4 cm (12 in.) linear
charts designed for either 24-hour or 7-day recording;
25.4 cm (10 in.) indicator scale; and six-digit direct-
reading totalizer.
350
-------
•PUROE CONNECTION
3 STRAIGHTENING VANES REC-
OMMENDED WHERE LESS THAN
8 DIAMETERS OF STRAIGHT PIPE
PRECEDE THE METER.
3-BLADED CONICAL
'POLYETHYLENE PROPELLER
STRAIGHTENING VANES SPACED
. . EQUIDISTANT APART
PURGE CONNECTION
AND REGISTER HOUSING
ON TOP OF DROP PIPE
(not shown)
PURGE LINE
RETAINER RING
SUPPORT ARM
DROP PIPE
SHIELD
PROPELLER CAP,
Figure A
351
-------
COMMENTS:
Propeller meters are not recommended by Sparling for use in raw sewage
and are unsuitable for a storm or combined sewer application.
352
-------
MANUFACTURER: TAYLOR
SYBRON CORPORATION
TAYLOR INSTRUMENT PROCESS CONTROL DIVISION
TELEPHONE (716) 235-5000
PRODUCT LINE: ELECTROMAGNETIC FLOWMETERS, SUBMERSIBLE PROBES
DESCRIPTION:
Flowmeters - The "MAG-PIPE" 1100/1200 Series electromagnetic flow-
meters measure flow by Faraday's Law of Magnetic Induction. A low-
level, AC signal generated by the movement of a conductive fluid in a
magnetic field is amplified by a solid-state transmitter which may be
used directly with Taylor receiving instruments such as controllers
Recorders, integrators, etc. Figure A shows a typical installation.
The HOOT or 1101T transmitters are used with Taylor 1100L, 1101L
1200L, 1210L, 1211L, 1240L, and 1241L sensing heads. The HOOT is the
remote unit and can be mounted up to 366 meters (1200 feet) from the
sensing head. The 1101T is the integral form and is mounted directly
on the sensing head; it produces a 4 to 20 mA DC signal which is linear
with flow. The transmitters are completely solid state and incorporate
thick film hybrid integrated circuits and an automatic quadrature
rejection (or null adjustment) feature which eliminates costly and time-
consuming start-up. If pneumatic output is required, the 1100L can be
coupled to a Taylor 737 transmitter. Teflon is the standard liner mate-
rxal used in the "MAG-PIPE" 1100L sensing head, although a variety of
other liner materials are offered.
The recently introduced Taylor 1210L series uses self-cleaning electrodes
to eliminate the measurement problems caused by severe coating buildup.
The electrode material used is Carpenter 20cb-3 stainless steel, which*
is ceramic coated for this application. Only a conductive "eye" (Fig-
ure B) for signal pickup is untreated; the eye protrudes into the higher
velocity portion of the process stream which is said to have a cleansing
action on the eye caused by the eye's unique geometric construction.
Submersible Probes - Taylor also manufactures a submersible probe for
measuring flow in large process pipes of 50,8 cm (20 in.) I.D. or over.
The probe, is a 15.24 cm (6 in.) magnetic flowmeter consisting of
platinum foil electrodes fired into a ceramic tube. The probe can be
used with either a remote or integrally mounted transmitter. The
assembly is welded to a mast which is fastened to a flange. When
inserted into the process piping, the ±2% accuracies may be achieved
when a symmetrical velocity profile exists at velocities above 0.6 m/s
(2 fps). In addition, compensation can be made for non-symmetrical
velocity profiles by field calibration techniques such as pitot
traverses, dye dilution, or other acceptable methods.
353
-------
Figure A
354
-------
Self-Cleaning Electrodes
Figure B
355
-------
SPECIFICATIONS:
1100/1200 Series Flowmeters (Typical)
Accuracy (including Sensing
Head and Transmitter):
Repeatability (including
Sensing Head and Transmitter:
Flow Range:
Sensitivity (Approx)*:
Output Signal**:
Minimum Process Conductivity:
Power:
Power Consumption**:
Pipe Sizes:
Weight:
±1% of flow (Sensing Head and
Transmitter calibrated separately)
±0.5% of flow (Integral Mounting
or Sensing Head and Transmitter cali-
brated together)
±0.25% of flow between 0.91 and
4.57 m/s (3 and 15 EPS) (optimum
calibration)
±0.2% of flow
0-0.9 to 0-9.0 m/s (0-3 to 0-30 fps)
300 microvolts rms/ft/sec
4-20 mA, DC
Down to 1 micromho/cm
Il7 VAC, 50/60 Hz or
117 VAC/234 VAC, 50 Hz
12 VA, 11.8 watts
2.54 cm (1 in.) to 30.48 cm (12 in.)
6 kg (13 Ib) - Transmitter; 20.4 kg
(45 Ib) to 109.0 kg (240 Ig) -
Sensing Head
PRICES: Sensing Heads, from $935.00 to approximately $5,000
(MAG-PIPE 1100 Series only)
Transmitters, Remote Mounted — $810.00
Transmitters, Integrally Mounted on Sensing Head — $791.00
COMMENTS:
The Taylor line of electromagnetic flowmeters features a number of what
are claimed to be unique features that extend the utility of their
devices. Electromagnetic flowmeters were discussed thoroughly in
Section VI and will not be discussed further here.
* Sensing Head only
** Transmitter only
356
-------
MANUFACTURER: THERMAL INSTRUMENT COMPANY
41 TERRY DRIVE
TREVOSE, PENNSYLVANIA 19047
TELEPHONE (215) 355-8400
PRODUCT LINE: THERMAL FLOWMETERS AND FLOW PROBES
DESCRIPTION:
The Thermal Instrument Company offers the Model 60 and 60-L thermal
flowmeters which could be applicable to the measurement of combined
sewage and stormwater; however, their Model 62-L thermal mass flow
probe and thermal flow probe (no model number) do not appear to be
suitable for this application because of the vulnerability of such
probes to damage when inserted in effluent and stormwater flows
having large quantities of suspended materials.
Model 60 Thermal Flowmeter - This device consists of a single,
unobstructed flow tube having no moving parts. The meter utilizes
the thermal boundary layer principle in which the sensing elements
(i.e., temperature and flow) are located on the outer surface of the
tube and never contact the flowing medium. The flow sensor is ener-
gized with a small amount of electrical energy (less than one watt);
the heat conducted off this element, by the flow stream, is directly
proportional to the mass flow rate of the fluid. Additional sensing
elements are located on the tube to compensate and correct for the
effects of fluid and ambient temperature. It is reported that any
fluid can be metered, no matter how corrosive or abrasive. The meter
is said to be not attitude sensitive and therefore can be mounted
vertically to prevent the buildup of solid particles in slurries. The
meter can be used with a variety of standard potentiometric recorder
or control devices, standard industrial and military transducers, and
digital readouts.
Model 60-L Thermal Flowmeter - The Model 60-L is a "spool piece" type
meter and is similar to the Model 60 in basic operation, with one
fundamental difference. The Model 60-L also has acquired level sen-
sors on the outside diameter of the flow tube. Figure A is a diagram
showing the location of the level and velocity elements in this combin-
ation meter body. The product of the readouts provided by the velocity
and liquid level measuring sensors will give total instantaneous flow
in a partially filled effluent duct, which usually is so designed that
it will never operate completely full except under emergency conditions.
357
-------
LTZ
•«•• • •
LEVEL
SENSORS
AMAMMflBWM*M"MMM!lKA*
....„_
_/yw\ ^2fa
///
/ 1
TEMPERATURE SENSORS *
\
FLC
x
^
W SENSORS
_.. .
=H
Figure A
SPECIFICATIONS:
Output:
Model 60 Thermal Flowmeter
Flow Rate:
Accuracy:
Repeatability:
Response Time:
Pipe Sizes:
Power:
0 to 10 mVDC signal to operate any
standard potentiometric recorder or
control device (standard)
1 to 5, 4 to 20, 10 to 50 mA or 1 to
5 VDC for recording and control purposes
(optional)
3 to 15 psig or 3 to 30 psig pneumatic
signals (optional)
Digital readout with BCD (optional)
1 cc/min. (minimum); no upper limit
'±1%
> ±0.2% of reading
1/2 sec.
up to 50.8 cm (20 in.)
115 VAC, 60 Hz, < 20 watts
358
-------
Model 60-L Thermal Flowmeter
Accuracy: Velocity - 1%
Level - 1%
Overall -2% .."-
Other attributes are similar to Model 60. , \
PRICE:
Prices vary with size and particular specification details; a complete
Model 60-L in a 61 cm (24 in.) size costs around $15,000.
COMMENTS:
The Thermal Instrument Company's products appear very suitable for
measuring storm and combined sewer flows if all the manufacturer's
claims are valid. No applications data on these fairly new devices
are available for such services.
359
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MANUFACTURER:
TRI-AID SCIENCES, INC.
161 NORRIS DRIVE
ROCHESTER, NEW YORK 14610
TELEPHONE (716) 461-1660
PRODUCT LINE: ULTRASONIC FLOWMETER
DESCRIPTION:
The Tri-Aid Sciences temperature-compensating, ultrasonic flow measure-
ment and transmitter system is designed for use with open channel
flumes or weirs having a 3/2 power flow characteristics. The model
FC-3-SW ultrasonic transmitter, when correctly installed and calibrated,
will measure the water depth in front of the flume or weir.
This system consists of two basic components. The first is an enclo-
sure housing the electronic control, integrated circuit flow character-
izer, and transmitter. The second is an ultrasonic transducer head
for bracket mounting above the water flow at the flume or weir. The
transmitter and "head" are connected with a coaxial cable for the meas-
uring signal and two wires for air temperature compensation. The sys-
tem generates a high frequency sound pulse from the "head" mounted
above the water flow. When the sonic pulse is reflected from the wa-
ter's surface and received back, the control interprets the time delay
period into water depth and the integrated circuit function module .
characterizes the signal into a linear 4 to 20 MADC flow signal output.
The transmitter is enclosed in a 40,6 X 35.6 X 15.2 cm (16X14X6 in.)
oil- and dust-tight fiberglass enclosure for wall mounting. The
explosion-proof "head" is encapsulated in Kynar to protect it from the
effects of liquids and most industrial operating environments. The
output signal from the FC-3-SW may be used to provide a remote input to
a Tri-Aid integrator system for flow totalizing and sampling control.
It may also be used with indicators, recorders, controllers, and/or
computers to meet the customer's system requirements. The transmitter
enclosure can be located up to 91m (300 ft) from the weir or flume.
Typical installation details are shown in Figure A. Power requirements
for the system are: 115 VAC, single phase, 10 amps, 60 Hz ±10%.
PRICE:
Not available at time of writing.
COMMENTS:
The 0.9m (3 ft) maximum distance from the face of the transducer head
to the zero flow datum is for standard calibration. For special appli-
cations, this distance can be. increased up to 6m (20 ft) to meet re-
quirements for many storm or combined sewer applications.
360
-------
STN.STL. OR RUSTPROOF
MATL. REQ'D. (SHIM AS
NECESSARY TO LEVEL
TRANSDUCER "HEAD")-
PREFERRED LOCATION!
OF REMOVABLE
FASTENERS
TYPICAL .ULTRASONIC
TRANSDUCER (HEAD>
MOUNTlNGr
RIGID CONDUIT TO TRANSMITTER ENCLOSURE
LIQUID-TIGHT COklKJECTOR
5'TO 10' FLEXIBLE COKJDUIT
LI QUID.-TIGHT CONDULET
HUB,3/4" N.RT. FOR
SPLICE OF COAXIAL
CABLE 4 (2}*IS WIRES.
LOCATION! OF-!
FASTENER FOR
FIRM SUPPORT
TO PREVENT -
VIBRATION OR
SOUND TRAMS-
MISSION.
ULTRASONIC
TRANSDUCER "HEAD"
\€f MINI
CAT
FLOW)
LOCATE PER
FLUME OR WEIR
FLOW MEASUREMENT
POINT (SEE FLUME
DATA PROVIDED
WITH FLUME").
* NOTE:
BOTTOM SURFACE. OF TRANSDUCER WHEADW
BE PARALLEL. TO LIQUID SURFACE.
36" MAX.
CAT ZERO
/ FLOW)
Figure A
361
-------
MANUFACTURER: UNIVERSAL ENGINEERED SYSTEMS, INC.
7071 COMMERCE CIRCLE
PLEASANTON, CALIFORNIA 94566
TELEPHONE (415) 462-1543
PRODUCT LINE: FLOWMETERING SYSTEMS (CONTROL CABINET,
RECORDER, TOTALIZER, READOUTS)
DESCRIPTION:
UES offers its electronic FLO/Monitor flow measurement system in several
different configurations - i.e., for permanent installations, remote or
temporary locations, and intrinsically safe installations for "hazardous"
area applications. Specifically designed for measuring wastewater flow
in manholes, in effluent and influent lines, etc., this completely elec-
tronic system, which utilizes a Palmer-Bowlus flume for its primary
element, does not employ floats, probes, mechanical linkages, or bub-
blers. The basic unit consists of a control cabinet and the measuring
flume. The control cabinet contains the electronic circuits, flow
recorder, flow totalizer, power supply, etc. The measuring flume
carries an embedded sensor element which provides the electronic infor-
mation relating water depth to flow. Figure A shows a typical temporary
manhole installation.
Measuring Flume - The physical configuration and dimensions of this
primary measuring device (Figure B) follow the standard Palmer-Bowlus
concepts. Its smooth, acrylic-PVC plastic construction is rugged and
causes little, if any, disturbance or restriction to water flow. Sizes
to 30.5 cm (12 in.) are stock items; larger sizes may be obtained by
special order.
Flow Rate Recorder - This secondary device provides a 30-day, continu-
ous strip chart for recording a permanent record of flow variations
(rate vs time) in the sensing flume at all times. Special pressure-
sensitive chart paper is used.
Flow Totalizer - This six-digit counter displays total flow volume
through the flume in units from one thousand to one billion gallons.
Telemetering - Via a special operational plug provided with each moni-
tor, flow rate and total flow information can be sent to central office
terminals. Built-in logic circuits are provided for this purpose.
Remote Display - Up to 1525m (5000 ft) of 6-conductor, No. 20 gauge
shielded wire can be provided as interconnecting cable between an
optional remote display and the low-voltage FLO/Monitor computer
(Model 8092 only). The remote display contains a flow rate recorder .
and a flow totalizer and an alarm to signal excessively high or low
flow rate.
362
-------
Temporary Location
Model 8091
Permanent Installation
Model 8090
Figure A
363
-------
Figure B
364
-------
SPECIFICATIONS:
Flume
Pipe Size - cm (in.)
10.2(4)
15.2(6)
20.3(8)
25.4(10)
30.5(12)
f 4 1
Length - cm (in.)
26.4(14)
50.8(20)
68.6(27)
81.3(32)
96.5(38)
Max Flow - MLPD (MGD)
.475 (.125)
•95(.25)
1.90(.50)
3.42(.90)
5.32(1.40)
FLO/Monitor (All Models unless otherwise indicated)
Accuracy:
Power:
Size:
Control Cabinet
Remote Display Unit
(8092 only)
FLO/Computer (8092 only):
Weight:
Control Cabinet
(8090/8091)
Power Supply (8091 only)
Remote Display Unit
(8092 only) ,
FLO/Computer (8092 only)
Temperature Range:
Price:
.±4% full scale
120V 60 HZ
12V (Rechargeable gel-
battery for 8091 FLO/
Monitor)
30.4x35.6x15.2 Cm
(12x14x6 in.) .
2p.;3x25.4xl0.2 cm
(8x10x4 in.)
20.3x25.4x10.2 cm'
(8x10x4' In.)
•9.p7:kg (20! Ib)
11.34 kg (25 Ib)
-4.54 kg (~10 Ib)
~2.27 kg (~5 Ib)
-1° to +49°C (30°/to 120°F)
Not available at time of
writing.
365
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COMMENTS:
Using a characterized electronic probe embedded in the wall of the
Palmer-Bowlus flume offers many advantages for storm or combined
sewer application. However, the one-piece design will present size
restrictions due to manhole entry dimensions.
366
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MANUFACTURER:
PRODUCT LINE:
DESCRIPTION:
VICKERY-SIMMS, INC.
P.O. BOX 459
ARLINGTON, TEXAS 76010 , .-
TELEPHONE (817) 261-4446 :
ORIFICE PLATES, FLANGES, FITTINGS, AND METERING
TUBES; ASME AND SHORT-FORM VENTURI TUBES; FLOW
NOZZLES; PARSHALL FLUMES; TURBINE FLOWMETERS
Vickery-Simms is a long-established manufacturer of primary flow meas-
urement devices. Each of their product lines will be discussed briefly.
Orifice Plates and Accessories - Vickery-Simms (VSI) maintains an
environmentally-controlled atmosphere where concentric, eccentric,
segmental, and quadrant edge orifice plates are bored to precision
tolerances in conformance with AGA, ISA, and ASME recommendations
(unless otherwise specified by the customer). Each plate is stamped
with line size, ASA rating, material, and exact orifice bore. All
plates which are beveled are stamped "inlet" on the square-edged side.
Sizes available for line diameters are from 1.3 to 229 cm (0.5 to
90 in.) in virtually any machinable material to suit the application.
Types 302, 304, and 316 stainless steel, hastelloy, and monel are
stocked for immediate delivery. Orifice flange unions, fittings to
allow removal without interrupting service, straightening vanes, and
meter runs for highest accuracy are also offered by VSI.
Flow Nozzles - VSI manufactures flow nozzles for critical and sub-
critical flow in accordance with ASME standards. These are available
in carbon steel, chromo moly, and stainless steel in sizes from 2.5 to
76 cm (1 to 30 in.). For guaranteed accuracy, flow-calibrated meter
runs are also manufactured.
Venturi Tubes - VSI manufactures a number of venturi tubes including a
fabricated type (welded, not cast) ASME, a short form, and a low
pressure loss venturi. The fabricated, long-form (ASME) venturi is
lighter in weight and more durable than cast or forged Venturis. The
short-form venturi, while offering standard venturi accuracy (±0.75%
uncalibrated), requires less laying length (four times the pipe diam-
eter) and produces only slightly greater unrecovered pressure loss.
The low pressure loss venturi or flow tube is a special design that
maintains good uncalibrated accuracy (±1%) but offers only about one-
fourth the pressure loss of a standard venturi (typically 3% with a
beta ratio of 0.75).
367
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All VSI venturi tiihes are available in a wide range of standard sizes
from 7.6 to 122 cm (3 to 48 in.) and four beta ratios (0.375, 0.490,
0.630, 0.750). Other sizes and ratios can be manufactured for special
situations. A partial list of standard materials includes carbon steel,
various stainless steels, cast iron, PVC, and fiberglass. Interior
coatings of nickel plating, tungsten carbide, or glass lining are avail-
able to suit special applications. Insert types are offered as well as
flanged and weld-in designs. Both single pressure tap designs as well
as multiple taps with an interval annulus are offered.
Parshall Flumes - VSI manufactures Parshall flumes, in all sizes, made
of fiberglass, steel, or prestressed concrete. They are available with
or without a built-in electronic flow element (liquid height gage); rate
indicators, recorders, and totalizers are also available.
Turbine Flowmeters - VSI manufactures insertion-type turbine flowmeters
for use with or without a check valve. In-line types with threaded or
flanged ends are also available. They are offered for use in pipe sizes
from 7.6 to 244 cm (3 to 96 in.).
PRICES:
Prices were not available at time of writing.
COMMENTS:
VSI manufactures a wide line of primary flow measurement devices and
will assist customers in assembling complete flow measurement systems.
All of these devices were discussed in Section VI and will not be com-
mented upon further here.
368
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MANUFACTURER: WALLACE-MURRAY CORPORATION > .
CAROLINA FIBERGLASS PLANT
P.O. BOX 580
510 EAST JONES STREET
WILSON, NORTH CAROLINA 27893
TELEPHONE (919) 237-5371
PRODUCT LINE: PARSHALL FLUMES
DESCRIPTION:
Wallace-Murray manufactures a variety of products made of fiberglass
reinforced plastics, including a line of standard Parshall,flumes.
These flumes feature maximum chemical and corrosion resistance, under
normal conditions, through their use of polyester resins. Wallace-
Murray offers flumes of varying depths and several optional features.
Throat widths are available from 7.6 to 121.9 cm (3 to 48 in.); lengths
range from 0.3 to approximately 3.35m (3 to 11 ft).
A standard feature of the Wallace-Murray flume is a head gage molded
into the side of the flume at its lower end for the measurement of free
flow discharges and flows under partially-submerged conditions. A free
flow discharge graph is used in conjunction with the gage to determine
flows under these conditions. Under submerged conditions, head flow
must be measured at both upper and lower locations. By using flow cor-
rection curves, a determination of the flow loss due to submerged con-
ditions can be made. Head gages at the second location are optioanl
and will be supplied upon customer request.
Optional features of the Wallace-Murray devices include the incorpora-
tion, on some models, of a 30.5-cm (12-in.)-diameter floatwell (may be
mounted on either side of the flume) or a 5-cm (2 in.) tap for the in-
stallation of a remote floatwell or bubbler system. A sanitary white
gelcoat interior surface is also available. . Installation design fea-
tures of the flume includes the provision for free standing installa-
tion with additional reinforcing ribs or stiffeners optional for maximum
stability instead of the standard loops for anchoring when used as
liners in concrete.
PRICES:
Prices not available at time of writing.
COMMENTS:
Parshall flumes were discussed thoroughly in Section VI and will not be
commented upon further here.
369
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MANUFACTURER: WESMAR INDUSTRIAL SYSTEMS DIVISION
905 DEXTER AVENUE NORTH
SEATTLE, WASHINGTON 98109
TELEPHONE (206) 285-2420
PRODUCT LINE: ULTRASONIC MEASURING DEVICES
DESCRIPTION:
The Industrial Systems Division of WESMAR (Western Marine Electronics,
Inc.) manufacturers several secondary liquid measurement devices
utilizing the techniques of ultrasonic (sonar in air) ranging. These
are the FM 9, a noncontact ultrasonic liquid level "flowmeter" for
flumes and weirs, and SLM 9 and SLM 15 ultrasonic devices for the
measurement of liquid levels. These devices are all readily adaptable
to water and sewage applications.
FM 9 Flow Meter - Actually an echo-sounding instrument, the FM 9
represents a new concept of noncontact weir/flume flow measurement
(actually level monitoring) involving no moving parts or mechanical
linkage. An all solid-state device, the FM 9 (Figure A) consists
basically of an electronics unit (control box), PVC-encapsulated sensor,
a meter, and a junction box (JIG enclosure).
FOR:
RECTANGULAR WEIRS • CIPPOLETTI WEIRS • TRAPEZOIDAL WEIRS • "V NOTCH" WEIRS
PARABOLIC FLUMES • PARSHALL FLUMES • LEOPOLD-LAGCO FLUMES
Figure A
This device employs a sensor, which is placed above the liquid level.
A repetition rate generator in the electronics unit triggers an oscil-
lator that sends a signal through a driver and power amplifier to the
370
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sensor which converts these pulses into high frequency sound waves.
The sensor directs these acoustic signals downward to the material.
The sensor detects the returning sound wave (echo) and converts it to
an electrical signal. Precision timing circuits are used to measure
the time delay for the echo to return. Processing of the electrical
signals converts the pulse transmit time to an analog voltage or current
proportional to the measurement distance. Output is available which
represents height or flow. Temperature compensation circuitry neutral-
izes any temperature variations.
SLM 9/SLM 15 Level Monitor - These are short-range liquid level monitors
which are entirely self-contained and are designed to interface with
standard industrial meters, recorders, and equipment of all types.
Solid state techniques, including the use of integrated circuits, have
been employed.
A basic system consists ,pf an electronics board (power supply, trans-
mitter, receiver) and totally encapsulated PyC sensor. The SLM 9 pro-
vides noncontact level measurement for distances up to 3m (10 ft) from
the sensor. Proportional 0-5 volt and 0-1 mA outputs are standard.
Options include: 4 to 20 mA current output; various meters and enclo-
sures ; and five independently adjustable set points that may be set at
desired level points for pump control, alarm indicators, or annunciators.
Operating principles for liquid measurements are similar, from an
electronic and acoustic standpoint, to those of the model EM 9 flow
meter.
SPECIFICATIONS:
Range (minimum) :
Range (maximum)
Resolution:
Repeatability:
Linearity:
Output Signals:
FM 9/SLM 9 - 41 cm (16 in.)
SLM 15 - 46 cm (18 in.)
FM 9 - 3m (10 ft)
SLM 9 - 3m (10 ft) (liquids)
SLM 15 - 7m (20 ft) (liquids)
within 1%
within 1%
within 1%
FM 9/SLM 9
0 to 5 VDC
0 to 1 mADC
Sensor Beam Pattern:
SLM 15 - 0 to 5 VDC
0 to 1 mADC (1 to 5, 4 to 20,
10 -50 mADC)
7° conical included angle
371
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Input Power:
Electronics to
Sensor Remote
Operation:
Dimensions (Enclosure)
Weight:
Electronics
Sensors
PRICES:
110/220 VAC, 50-60 Hz, 10 watts
FM 9/SLM 9 - up to 91.4m (300 ft)*
SLM 15 - up to 152.4m (500 ft)*
30.4x25.4x12.7 cm
(12x10x5 in.)
0.91 kg (2 Ib)
0.45 kg (1 Ib)
Only general cost guidelines can be provided due to the many variables.
Complete systems range from $1,500 to $2,500. Sensors cost from $125
to $150 and control boards are from $500 to $800. Enclosures (junction
boxes) are available from $25 to $500, depending upon size and NEMA
rating.
COMMENTS:
Ultrasonic liquid height gages were discussed in Section VI and will
not be commented on further here.
* Using Coaxial Cable RG620.
372
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MANUFACTURER: WESTINGHOUSE ELECTRIC CORPORATION
OCEANIC DIVISION
P.O. BOX 1488, MAIL STOP 9R3Q
ANNAPOLIS, MARYLAND 21404
TELEPHONE (301) 765-5658
PRODUCT LINE: ACOUSTIC FLOWMETER
DESCRIPTION:
More than 10 years of research in the flow measurement field by
Westinghouse has gone into the development of this acoustic measuring
system. The Model L. E. (leading Edge) Flowmeter is so named because
it uses only the leading edge of an acoustic pulse as a basis for
determining liquid velocity and volume flow rate. While this flow-
metering system was designed to measure water flows, the basic principle
applies to most other liquids as well, including raw sewage.
Two ultrasonic transducers are installed in opposite walls of a conduit,
with the line between them at an angle (45°, for example) with the
conduit axis. The two transducers simultaneously transmit pulses of
sound energy through the moving fluid. The pulse moving with the flow
travels the distance between transducers in less time than the pulse
moving against the flow. The system measures the transit time of the
faster pulse and the difference between the transit times of the faster'
pulse and the slower pulse. Using these two time measurements, it
solves two simultaneous equations in two unknowns - the sound velocity
and the fluid velocity. Sound velocity can vary with changes in fluid
temperature, salinity, and other properties. By measuring sound veloc-
ity and correcting for it, the system automatically maintains its
accuracy for varying fluid conditions. Volumetric flow through a con-
duit is computed by integrating the local fluid velocity over the con-
duit cross section. The system does this by measuring local velocities
along several paths, scaling these velocities for path geometry, and
summing. A pair of transducers is required for each path. Four trans-
ducer pairs (four paths) will achieve better than 1% accuracy with any
practical velocity profile. Volumetric flow in an open stream is com-
puted in a like manner, except that water stage is measured and
accounted for as it varies.
Figure A sh9ws a basic acoustic configuration arrangement. Two probes
are shown in the diagram, each with separate transducers and trans-
mitters; however, in actual practice only one transducer is generally
used in each probe, and both probes are energized by a common trans-
mitter. The probes provide an unobstructed flow path without head
loss.
373
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PROBE 2
figure A
The basic L.E. system consists of the transducers and transducer fit-
tings, cabling, and a console housing the electronic circuitry and
readouts. Four pairs of transducers are provided for flow in conduits;
in open channel applications, the number of transducer pairs must be
determined by the installation geometry.
374
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SPECIFICATIONS:
Accuracies:
Operating Range:
Power (Console):
Flow Rate:
to 0.1% (demonstrated) in pipes from
0.3 to 9.14m (1 to 30 ft)
10,000 to 1 (typical)
115 VAC, 60 ±2 Hz, 3 amps, <500 watts
No upper limit. Flows approaching
16,990,000 £/s (600,000 cfs) have been
measured. Liquid velocities to
>0.5 percent of full scale.
Dimensions (Console): 198x63.5x63.5 cm (78x25x25 in.)
Weight (Console): 136 kg (300 Ib)
PRICE: $40,000 up
COMMENTS:
Section VI discusses the advantages and disadvantages of this type flow-
meter. Cost, size, and complexity of this system mitigate against its
use for many storm and combined sewer applications.
375
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SECTION VIII
SELECTED PROJECT EXPERIENCE
In order to evaluate both standard, commercially available flow meas-
urement; equipment and custom engineered equipment in actual field use,
a survey of recent USEPA projects in the storm and combined sewer pol-
lution control area was conducted. Several USEPA projects designed
solely to develop improved flow measurement equipment were included in
the survey. Final reports were obtained where available, but for some
projects only interim reports existed and, in a few instances, tele-
phone conversations had to be relied on. The projects are discussed in
general chronological order, starting with earlier efforts and finish-
ing with current, on-going activities.
A survey of recent activities of several other Federal agencies in re-
search and development of improved flow measuring devices and methods
is also included herein. The responsibilities of these agencies include
measurement of water, so they are familiar with flow measurement needs to
fulfill their own objectives. In a few cases, these needs include measure-
ment of stormwater and combined sewage. Contacts with key personnel of the
agencies were made by personal interview, by telephone, and by letter.
CHARACTERIZATION AND TREATMENT OF COMBINED SEWER OVERFLOWS
Reference (73) describes a study whose general objectives were: (a) to
develop workable systems to manage overflows from the combined sewers
of San Francisco, thereby alleviating pollution and protecting bene-
ficial uses of local receiving waters, and (b) to provide the rationale
and methodology for controlling pollution from combined sewer overflows
in other metropolitan areas of the United States.
Data collection for the project included measurement of dry weather
flows of the Selby Street and Laguna Street trunk sewers and measure-
ment of storm overflows from the two sewers. Eight storm overflows
were monitored at the Selby Street outfall and two were monitored in the
Laguna Street outfall. Monitoring included measurement of rainfall and
discharge.as well as the quality characteristics of the overflows.
The tracer dilution method was selected for use in measurement of dry
weather flows. Pontacyl Brilliant Pink B fluorescent dye was used for
the tracer, and quantitative analyses for the tracer were made with a
Turner Model 110 Fluorometer. Selection of the tracer was based on the
following advantages:
a. Only small quantities of dye are required because precise
determination of the dye concentration is possible at
10~3 mg/£. Thus cost and quantity requirements are reduced.
376
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b. In most sewage flows the "background" of this particular
dye is not significant. The amount of tracer does not
have to be materially increased in order to eliminate
spurious background effects.
c. The tracer is not significantly affected by the presence
of materials normally found in sewage.
Use of the dilution method did not prove satisfactory for measurement
of the Selby Street overflow. Uneven distribution of the tracer when
injected resulted from exposed sludge banks, and there was insufficient
turbulence for adequate mixing of the dye. Because of the resulting
lack of reliable data, a Palmer-Bowlus flume with a 1.22m (4 ft) throat
and 15 cm (6 in.) invert slab, constructed from 16 gauge galvanized
sheet metal was installed. A continuous record of the upstream water
level was obtained by mounting a Stevens water level recorder, operated
by float, in a stilling well constructed of sandbags.
"Because ofi adequate. nti.XA.ng betow the. pote.nt
othesi method w&6 uubed faofi fitou)
dye. -cn/eatum, the.
at Laguna S&ie.et and no
Because of generally unsatisfactory conditions, several methods were
used for the measurement of storm flow in the Selby Street outfall
structure. These were: ,
a. Velocity determination with current meters at a point 15m
(50 ft) above the outfall structure. Not considered to
yield reliable data as the meters were immediately fouled
with rags and other debris.
b . Differential head measurements over the broadcrested weirs
of the outfall structure. Because of expected interfer-
ence by tide gates, the theoretical, head-discharge rela-
tionship for a broad-crested weir of similar shape was
used for comparison purposes only.
c. Measurement of surface velocities in the outfall structure
by timing the traverse of styrofoam floats across a meas-
ured control section. A factor of 0.64 was applied to
. surface velocities to convert to average velocity, thus
accounting for both horizontal and vertical velocity
distributions. ,
d. Measurement of vertical velocity profiles in the outfall
structure with an especially designed current meter having
low velocity sensitivity. This was to establish discharge
values under low head conditions and to check the results
of the surface velocity determinations.
377
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Water levels in the outfall structure were continuously measured by
means of a "bubbler" gage. A rating curve was developed from the re-
sults of the surface velocity determinations and the current meter
measurements in the outfall structure. A theoretical curve computed
from the broadcrested weir formula was approximately 10% larger than
this developed curve.
Flow determinations in the Laguna Street overflow were made by meas-
uring the depth of flow at the outfall sewer and calculating the dis-
charge by means of the Manning equation. Use of the Manning equation
was said to be justified because the slope of the outfall.sewer is
known, and a uniform reach extends about 210m (700 ft) upstream from
the point at which depths of flow were determined.
STREAM POLLUTION AND ABATEMENT FROM COMBINED SEWER OVERFLOWS - BUCYRUS,
OHIO
Reference (74) contains the results of a detailed engineering investi-
gation and comprehensive technical study to evaluate the pollutional
effects from combined sewer overflows on the Sandusky River at Bucyrus,
Ohio, and to evaluate the benefits, economics and feasibility of alter-
nate plans for pollution abatement from the combined sewer overflows.
A year-long detailed sampling and laboratory analysis program was con-
ducted on the combined sewer overflows in which the overflows were meas-
ured and sampled at three locations, comprising 64% of the city's
sewered area, and the river flow was measured and sampled above and be-
low Bucyrus. >
Dry weather wastewater flow measurements were taken of the discharge
from three sewer districts, the influent and effluent of the wastewater
treatment plant, and the Sandusky River at upstream and downstream
gages. A weir was installed in each of the three trunk sewers, a
90° V-notch weir, a 61 cm (24 in.) rectangular weir, and a 46 cm
(18 in.) rectangular weir. For two days of the investigation, flows at
the weirs were measured and sampled at 15-minute intervals for 24 hours.
The Sandusky River, upstream and downstream, was measured and sampled
at one-hour intervals for 24 hours. Also, the wastewater treatment
plant influent and effluent were sampled at one-hour intervals and flow
measurements taken from the plan records. No problems with equipment
for measurement of dry weather flows were indicated.
To measure overflow during rainfall, rectangular weirs were built at
each of three overflow points. The weirs were constructed of one-inch
plywood, which was bolted onto (steel) angles imbedded in concrete.
The weir plates were 2.4, 4.9, and 3.0 meters (8, 16, and 10 ft) long
for Numbers 8, 17 and 23 overflows, respectively.
Water level recorders were mounted in instrument shelters 107 cm
(42 in.) behind the weirs. The recorders were Stevens Type F Recorder,
Model 68, with a 24 cm (9.6 in.) per day time scale and a 1:2 gage
378
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scale. All recorders were equipped with automatic starters which would
start the clocks at predetermined water levels.
A continuous record of flow in the Sandusky River above and below
Bucyrus was obtained for the study period. An existing recording gage
operated by the U.S. Geological Survey located at the first bridge be-
low the wastewater treatment plant was utilized for downstream flow
measurements. A new gaging station was installed on the river 91m
(300 ft) upstream from the first overflow point of the combined sewer
system. A rating curve for the gage was plotted using standard gaging
techniques. The recorders used at both gaging stations were the
Stevens A35, with 1:6 gage scales. The time scales for the gages were
12.2 and 6 cm (4.8 and 2.4 in.) per day, for the upstream and down-
stream gages, respectively.
No specific problems with flow measurement equipment were reported.
However, a tabulation of overflows indicates that no record was ob-
tained at Numbers 8 and 23 overflows during some periods. Reasons for
this loss of record were not given. No check on the accuracy of the
records was made available.
ENGINEERING INVESTIGATION OF SEWER OVERFLOW PROBLEM - ROANOKE, VIRIGINA
Reference (75) reports on the results of investigations of 25% of
Roanoke, Virginia's separate sanitary sewer system, on the amounts of
infiltration for various storm intensities and durations, and on the
amounts of sewage overflow from the system.
Flows in three sanitary sewer interceptors, and streams draining the
corresponding basins, were gaged during storm events to measure infil-
tration and runoff quantities and to establish their relation to rain-
fall intensities and durations. After significant variation in dry
weather flows was observed, continuous monitoring of flows in the in-
terceptors was maintained. Overflows bypassing the Water Pollution
Control Plant were measured during rainfall events.
Sharp-crested weirs were used to measure flows in two of the streams.
In the third stream, a stage-discharge curve was developed from the
Manning formula using the measured hydraulic characteristics of the
stream. In two of the interceptor sewers, and in the Water Pollution
Control Plant overflow, a stage-discharge curve based on the Manning
formula and the measured hydraulic characteristics of the sewer were
used to convert depth measurements to flow estimates. In the third
interceptor sewer, dry weather flows were estimated using the Manning
formula, but during rainfall events the sewer became surcharged and
overflow was measured by means of a weir installed in the side of the
manhole wall.
No problems with use of the streamflow measurement devices and methods
were noted. However, accuracy of measurements with use of the Manning
379
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formula in the natural stream channel photographed must be considered
very poor. A photograph of one of the weirs used for streamflow meas-
urement shows a significant accumulation of trash and debris on the
weir. Under this condition, accuracy must be considered poor. Hydro-
graphs indicated that two of the interceptor sewers were surcharged
during many of the storms, and a record of discharge was not obtained
during those periods.
Water levels at the gaging sites were recorded by means of six float-
actuated, continuous water-level recorders manufactured by the Instru-
ments Corporation (now a part of Selfort Instrument Company), and one
pressure type recorder manufactured by the Bristol Company. After the
float-actuated recorders were serviced and supplied with an expanded
time scale, they performed satisfactorily for the duration of the pro-
gram. During dry-weather periods, the bubbler pipe in the Bristol re-
corder collected debris and required frequent cleaning. Because of
this maintenance problem, it was replaced with a float-actuated, con-
tinuous water-stage recorder.
COMBINED SEWER OVERFLOW ABATEMENT ALTERNATIVES - WASHINGTON, B.C.
Reference (76) reports on a project whose objectives were to: (a) de-
fine the characteristics of urban runoff in the subject area; (b) in-
vestigate the feasibility of high-rate filtration for treatment of
combined sewer overflow; and (c) develop and evaluate alternative meth-
ods of solution.
Investigative activities included field monitoring of combined sewer
overflows at two sites, and of separated stormwater discharges at one
site. The monitoring program was conducted over a period of about
six months, April 1 to September 23, 1969.
Selection of a satisfactory technique for flow measurement presented a
problem. Weirs were not used because backwater elevations would have
caused surcharging and flooding at the expected high flow rates.
Depth of flow measurements with the use of a steady state empirical
equation such as the Manning equation for calculating flow was not used
because flow conditions were not steady state during periods of storm
runoff. The method selected was use of lithium chloride as a tracer
in a procedure similar to that of the salt dilution method (continuous
injection type). Use of a lithium salt is said to improve the techni-
que because the background of lithium in wastewater is usually low, and
because lithium concentrations at fractional parts per million levels
can be accurately and conveniently determined by atomic absorption or
flame emission spectroscopy. The slope-area method was used as a check.
A number of difficulties experienced in use of the equipment resulted
in loss of flow record during several major storms. Greatest trouble
380
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was in clogging or damage to the submersible pump used to collect sam-
ples of wastewater required for measuring lithium chloride concentra-
tion. Flooding of one of the lithium chloride release stations caused
damage to the bubbler instruments used to measure water stage, to the
lithium chloride release system, and to other equipment.
Flow rate estimates based on depth-of-flow measurements and the Manning
formula were compared with results of the tracer method. Only a very
general correlation with significant spread resulted. Large differ-
ences in flow were attributed to inaccurate measurement of depth of
flow and the assumption of steady-state conditions inherent in Man-
ning's formula.
URBAN RUNOFF CHARACTERISTICS „
Reference (77) is an interim report on investigations for the refine-
ment of the comprehensive EPA Storm Water Management Model.
: - , "•> l. . ' ' ' - •
"Vetaile.d information on the. watestAhe.d chatacteAi&tic& and data on >um-
ofifi quantity and quality have. been compiled faiom a one. ye.ax. Atudy oft a
combined &eweji wateA&heJd oft apptioxAmateJly 2380 a&teA -in Cincinnati.,
Ohio. Collection oft the&e. data i* planned to continue, oven. a thfiee.
period."
Flows at three sites in the sewer watershed were monitored. At two of
the sites, flow was actually measured in two tributary sewers immedi-
ately upstream from their junction. The third site was at the outlet
of the watershed; thus, five sets of flow measuring equipment were
used.
"The. i&ow mejOAutung appanatu& comi&t& o£ a comptieAAon., a manometesi,
and a Taylox. pn.eAt>un.e.-type. necoJideA. Thl& n.e.do^dnfi operate* by me.as>~
u>u.ng tke. pti&A&uJKi. due. to the. de.pth and veZoc^ty o£ wateA £lou)j.ng -into
the. pipe, by bubbting OAJL through a tong tube. JMAeAted tnto the. wateJi.
The. gage..sie£ejaAeA cuJt at a constant pieAAute. and a& the. de.pth and the.
veZoc^ity o£ fitow change* , the. pJieAAute. dsL^esizntial AJ> tie.conde.d on a '
cAJicjuZcvi chaJit wi sincheA ofi waiesi. ThiA ptieA&uJie. di.6fieAe.ntLal *A act-
ually the. £pe,cA,{i
-------
Apparently, the value of slope used in the Manning formula was that of
the sewer line at each of the five measuring sites. A photograph in
the report shows a heavy, metal, top-hanging gate at the outlet of the
sewer watershed. The outlet flow monitoring site is described as about
6m (20 ft) upstream from this gate. If this is the case, flow past the
site probably would not be uniform, and the Manning formula would not
be applicable.
Flows in the two pairs of sewers just upstream from'their junction with
the two sewers to be monitored would be controlled by the slopes of
each of the two monitored sewers rather than the slopes of the four
tributary sewers immediately upstream, which were the slopes in the
Manning formula to compute flow. In any case, water surface slope is
more properly used with the Manning formula than is the sewer slope.
Plotting of storm hydrographs for the measured sites discloses a number
of serious inconsistencies in the data.
STORM AND COMBINED SEWER POLLUTION SOURCES AND ABATEMENT
GEORGIA
ATLANTA
Reference (78) reports on a study of six urban drainage basins within
the City of Atlanta, Georgia, served by combined and separate sewers,
to determine the major pollution sources during storm events. Rain-
fall frequency analysis and simulation techniques were utilized to ob-
tain design criteria for alternative pollution abatement schemes.
Measurements of flow were made of three major overflows, as well as of
the interceptor sewers originating at these points of overflow. Three
branches of South River were measured, as was the South River main
stream at four points. A bypass at the interceptor entering one of the
wastewater treatment plants was measured.
Data were collected from January 1969 until April 1970. Continuous
flow monitoring was maintained at the river and its tributary stations,
and in the interceptors where dry weather flow characteristics were of
interest. Event monitoring only was conducted of overflows and of the
bypass to the treatment plant.
Rating curves for all gaging stations were developed by stage-discharge
measurements with current meters. Either Price Type AA or Pigmy Type
current meters were used. Some discharge measurements were verified
by alternate methods or formulas, but results of these verifications
are not given.
Stevens Type F water level recorders were used throughout. Gaging sta-
tions were reported to be constructed in accordance with established
U.S. Geological Survey practice. For flow level recording at intercep-
tors, scow floats were installed at manholes a short distance downstream
from regulators.
382
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Although probable accuracy of the records collected was not reported,
an indication of their accuracy is available, based on one of the gag-
ing stations in the project which was operated by the U.S. Geological
Survey. This station, having a drainage area of 3.86 sq km (1.49 sq
mi), had been operated since October 1963, or for more than six years.
The greatest flow measured by current meter during the period was
5947 1/s (210 cfs), but the rating curve was extended to 23,220 1/s
(820 cfs) by computation of flow through a culvert. Records at the
station are stated by the USGS as poor, with no qualification.
STORMWATER PROBLEMS AND CONTROL IN SANITARY SEWERS - OAKLAND AND
BERKELEY, CALIF.
Reference (79) describes an engineering investigation conducted on
stormwater infiltration into sanitary sewers and associated problems in
the East Bay Municipal Utility District, Special District No. 1, with
assistance from the cities of Oakland and Berkeley, California. Rain-
fall and sewer flow data were obtained in selected study sub-areas that
characterized the land used patterns predominant in the study area.
Results obtained were extrapolated over large areas.
Palmer-Bowlus flumes were installed at three of the ten metering sta-
tions established specifically for the study. These flumes were con-
structed of stainless steel and were designed to fit the respective
sizes and shapes of the sewers. They were mounted in the outlet sewer
from the manholes so that head measurements could be made at the proper
distances upstream from the throats. Wooden channel extensions through
the manholes were installed to prevent water spreading out in the manhole
as depth in the sewer increased.
At seven of the new metering stations, 90-degree, V-notch weirs were
installed. These were constructed of marine plywood and covered for
additional water resistance with two coats of polyurethane finish.
For ease of installation, a channel closure was provided.so that it
could be easily slipped down into the flowing sewage and quickly bolted
in position after installing and sealing the actual weir plate.
Stevens type 2A35 water stage recorders were used at three weir loca-
tions where submergence of the weir was anticipated. These recorders
were selected for the ability to record two liquid levels simultaneously,
upstream and downstream from the weir.
Taylor pressure recorders were installed at the other seven new meter-
ing stations. With these recorders, liquid level sensing consists of
measuring the back pressure from a continuously purging nitrogen gas
bubble system.
383
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In several cases, equipment was installed in manholes near the centers
of streets, thus complicating the installation and use of equipment.
Otherwise, no problems were noted with the use of the equipment at the
newly established stations.
The flow rate at two pumping stations was determined by means of a
system-head curve for the station which gives the discharge rate for
each pump or combination of pumps. A recording ammeter was attached to
the pump electrical leads to indicate the total number of pumps running
at any given time. Relief overflow at one of these pumping stations
was measured by means of a broad-crested weir and a wet-well liquid
level recorder.
A third pumping station was equipped with both a wet-well liquid level
recorder and a flow recorder. The primary device for the flow recorder
was a venturi flow tube mounted on the discharge manifold of the pumps.
Jiir
The influent pumping station at the water pollution control plant was
equipped with individual flowmeters on each pump discharge which were
connected to a combined flow recorder. The primary devices for the
flow recorder were the discharge weirs in the grit chambers which re-
flect the respective pump discharge rates.
A pumping station relief overflow structure was provided with a flow
measuring device for measuring the volume of water that overflowed.
The 'flow measuring arrangement consisted of measuring the liquid levels
on both sides of a rectangular tide gate and extracting the flows from
the manufacturers rating curve. Because of difficulties in installa-
tion and operation, no usable flow measurements were obtained during
periods of overflow.
DISPATCHING SYSTEM FOR CONTROL OF COMBINED SEWER LOSSES
Reference (80) describes a regulator control system which is said to
demonstrate impressive reductions in combined sewer overflow pollution
of the Mississippi River in Minneapolis and Saint Paul.
A mathematical model has been prepared that will, using rain gage data
for inputs, (a) perform rainfall runoff analysis; (b) divert combined
sewer runoff hydrographs at the regulators; and (c) route the diverted
hydrographs through the interceptor system. This model will assist in
operation of the system to retain combined sewer flows and utilize the
maximum flow capacity of the existing interceptor sewer system.
The project includes a computer-based data acquisition and control sys-
tem that permits remote control of modified combined sewer regulators.
Data from rain gages, regulator control devices, trunk sewers and in-
terceptors, and river quality monitors provide real-time operating
information.
384
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Water surface elevations in the system were monitored at about
48 points by the installation of bubbler gages employing a pressure-
carrying tube installed in the sewer, an air-supply cylinder, a bub-
bler, a pressure transducer, and a telemetry unit for transmitting data
to a central location. This equipment provided information on the fre-
quency and duration of overflows. Because flow rate was not measured,
data on the volume of overflows were not thus determined.
Flow in each of the three Minneapolis interceptors at the
Minneapolis-St. Paul city line> was metered by dual venturi meters in
each interceptor. This equipment, which was in use prior to the sub-
ject study, provides information on the effectiveness of the program to
use the interceptors for temporary storage of combined sewage. Flow
data in the interceptors served to provide a check on the accuracy of
rainfall runoff modeling. Probable error of flow measurement by the
venturi-meters was not discussed.
PRECONSTRUCTION EVALUATION OF COMBINED SEWAGE DETENTION FACILITIES
Reference (81) presents the result of a lengthy study of combined sewer
flows in Somersworth, New Hampshire prior to construction of detention
facilities. "In o&deA to gat /ie.a&onabty ac-cufiate. and sieZlabte. fitow
mea&u>ieme.nti> i£ wa& n.e.c.eAt>any to >tep£o.ce a Auction ofi the. outfall witin
a. weAA pit taAge. e.nough to provide, a. &CUA amount ofi &tWUing behind the.
weJA." This weir pit was 1.8 x 1.8 x 7.5m (6x6x24.75 ft), and the weir
was located 5.6m (18.33 ft) from the inlet.
Three different 0.63 cm (1/4 in.) thick steel plate rectangular weirs
with crest lengths of 0.3, 1.2, and 1.7m (1, 4, and 5.6 ft) were used,
the 1.2m (4 ft) one being employed for all but three months of the
year-long study. The design was such that the different weirs could be
changed easily in several minutes. The main difference in the 1.2m
(4 ft) weir was that its crest was elevated 1.2m (4 ft) above the floor
of the weir pit as opposed to 0.76m (2.5 ft) for the other two. This
weir was constructed after initial operation with the 0.3 and 1.7m
(1 and 5.6 ft) weirs, and "observation of high flow rates using the
5.6' weir indicated that it was desirable to increase the stilling in
the weir pit by raising the crest height."
"Head me£U>uAeme.nt& oveA the. 12" and 5.6' weAA& weAe. made. u&tng an ain
operated FiAzheA and PotteA n.e.c.ofideA. A &toat 'operated. ttvanAmitteA and
Ae.c.oAdeA manufiactuAe.d by the. Pe.nn/Mea&usie.-JlLte. fl-tv/ci-ton o£ Badge*.
Manufacturing Company WA u&e.d &OA hzad mea&ust.emewti> ovesi the. 4' umJi
Both n.e.o.o>ideA& weAe. &et up to u&e. 24 houA, 12" d^LameteA chant*. The.
FiAaheA and ?ofiteA ie.c.oft.deA c.hants> had a Jiang e. oft 0 to 20 Inches ofa
head, and the. Pe.nn/Me.a&uAe.-'ftite. Re.c.ofideA chasttA had a Aange. ofi 0 to
30
385
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"F£ow Junto the. w&it pit UXM> &uch that &omz tun.buJte.nce. wo6 cueate-d
the, weAJi pit. Thi& caused the. &low Jie.coKdesiA to paint out he.ad
uM.ement& Jin &hont vertical Atx.ok.eA i.nt>tead oft a. smooth Lena. ThiA con-
dition wa& cowie.cted 06 much a& po&Aibte. by the. addition oft the. 4' weJji
which had a, csiz&t 18" higher than. the. 12" and 5.6' taeMu>. The. added
depth o& ttoateA -in the. weAJi p did not appeal to upA&t the. hydraulic
chaiajcteAi&tic& ofi the. taeAJU>. However, be.£osie. any sampling paogaanu>
we/ie undertaken, the. kludge, buuitd-ap wa& totaJULy amoved fyiom behind
the, weJJtA in ondesi to obtain accunate. c.hemic.at and bio£ogic.al chafiao.-
ojj the. combined sewage, ^£ow. The. actual Aludge. baiid-ap
occuA within a couple. o£ day* afateJi the. i.n&tatiati.on o£ a weAJi.
The. majo/tity o& Aludge. Jbn. thiA combined Aewage. faJLow c.om>i&ted oft Q>iit
with a &malt percentage. o& ofiganic matte*.."
Head measurements were "... converted to flows using appropriate for-
mulae for the rectangular weirs used in the weir pit." By this it is
assumed that the Kindsvater-Carter equation was used rather than the
Francis formula, which would require corrections for both less than
standard contraction and velocity of approach much of the time. For
example, at the maximum head of 0.6m (2 ft) on the 1.2m (4 ft) weir
(any greater head would overflow the 1.8m deep weir pit) the Kindsvater-
Carter equation indicates a discharge of around 91 MLD (24 MGD), whereas
th.e uncorrected Francis formula yields approximately 83 MLD (22 MGD), a
10% difference. The maximum discharge for the 1.7m (5.6 ft), as com-
puted assuming the recorder's full 51 cm (20 in.) of head was used, is
approximately 98 MLD (26 MGD). Maximum flow rates recorded with the
1.2m (4 ft) weir of from 99 to 148 MLD (26.2 to 39.0 MGD) are reported
but not explained. It is possible that the 148 MLD (39.0 MGD) dis-
charge was estimated but not so indicated. The point is that high ac-
curacies should not necessarily be expected with the given installation
at the higher flow rates.
URBAN STORM RUNOFF AND COMBINED SEWER OVERFLOW POLLUTION - SACRAMENTO,
CALIFORNIA
Reference (82) contains the results of a program to develop a general
method for determining the extent of pollution resulting from storm-
water runoff and combined sewer overflows occurring in an urban area,
and the application of this method to the City of Sacramento, California.
Combined sewage and stormwater in the system were characterized by col-
lecting samples and measuring flows at each of 19 sampling locations
during six wet weather periods. The intention was to collect, as nearly
as practical, at the commencement of rainfall, three hours thereafter,
and approximately 12 to 18 hours after the commencement of sampling.
386
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However, comparison with rainfall records indicates that the first data
of each storm period were not collected until the time of maximum rain-
fall intensity, or later.
The wastewater flows were established at manhole sampling stations by
use of the Manning formula. The coefficient of roughness was assumed
to be 0.013, a design value used by the City of • Sacramento Engineering
Department. The value of S used was the measured slope of either the
water surface or the invert. Because of difficulties in making the
required measurements for determination of slope, flow data at three of
the stormwater,runoff sites are not considered to be reliable. None of
the computed wastewater flows at manhole sampling stations were checked
by means of flow measurement equipment. ;
For design purposes, the peak stormwater runoff flow in each of the in-
dividual pipes comprising the Sacramento collection and conveyance sys-
tem was estimated from rainfall records by use of the rational method.
These estimated flows for a full pipe condition can be checked at three
locations with computed flows at the manhole sampling stations. They
differ with the computed flows by -6, +4, and -32 percent. This agree-
ment is exceptional, particularly as these are the three locations where
the computed flows are not considered to be reliable.
STORAGE AND TREATMENT OF COMBINED SEWER OVERFLOWS
Reference (83) describes a project to demonstrate the feasibility and
economic effectiveness of a combined wastewater overflow detention basin.
"A paved asphalt detention ba&in with, a AtoJiage. volume. o& S.66 acA.e.-6e.e£
wat> con&tfiacte.d at Chippewa fall*, Wi&con*in to Jie.ceA.ve. avzufilou) £tom a
90-acJie. combined &WQJI onea Including all o{> the. central ba&ine** di&-
&uct. The. AyAtem wa& designed *o that the. &ton.e.d combined Aewage. could
be. pumpe.d to the. wa&tewateA treatment plant when precipitation *ab*ide.d.
Vusiing 1969, due. to dty weather, the. pond x.e.c&ive.d only *ixte.en di&-
chasigeA, but completely filled twice, and ov&tfilou} to the. fiive*. occuflAed.
Voting 1970, theAe. weae. 46 di&change* and the. pond \JUUL
-------
and a rating curve for the flume, which was approximated in four linear
sections. Discharges indicated by rainfalls on eleven different occa-
sions were missed due to the recorder being out of order. Thus, eleven
percent of the runoff events were missed.
Overflow from the 'pond to the river was measured by a 6.7m (22 ft) long
sharp crested weir located in the overflow structure. The weir head was
measured by a Stevens Type A35 water-level recorder with a cylindrical
float.•• The chart time scale was 24.4 cm (9.6 in.) per day and the gage
scale was 1:6. The recorder was out of order during one of the three
overflow events which occurred during the period of project operation.
Flows to the wastewater treatment plant'were measured by a meter in the
plant which was not described. Apparently, this record is complete.
A THERMAL WAVE FLOWMETER FOR MEASURING COMBINED SEWER FLOWS
Reference (64) is a final report for a project to study the application
of thermal techniques to the measurement of flow rates in combined sew-
ers. The volume flow rate was to be computed as the product of average
flow velocity in the sewer, and cross-sectional area of flow as deter-
mined from a stage measurement.
The use of flush-mounted hot wire or hot film anemometers in a direct
reading mode for measurement of average flow velocity was extensively
investigated. It was concluded that application of hot film anemometry
techniques to commercial application of measuring sewer effluent for ex-
tended periods of time was not feasible. Major reasons for this con-
clusion are: (a) changes in calibration occur due to contamination
film build-up; (b) breakdown of protective coatings over long periods of
time; (c) change in calibration that occurs due to dissolved gases
coming out of solution and depositing on the film element as bubbles;
and (d) the physical vulnerability of available probe configurations
combined with the difficulty of continuously measuring average velocity.
The thermal wave flow measurement system as developed incorporates five
thermal sensors mounted on the inside periphery of the pipe. Measure-
ment of the average flow velocity in the pipe is obtained by averaging
the longitudinal propagation velocities of the five thermal waves gener-
ated at the five symmetric peripheral positions. Tests of a prototype
unit indicated that this configuration does not provide signals which
have adequate precision to measure fluid flow with the desired accuracy.
The dissipation of heat was determined to be quite large, as was the
ratio of the average stream velocity to the apparent boundary layer
velocity.
The stage measuring system utilizes an electronic liquid level gage
which consists of two solid rods formed to fit the inside curvature of
the sewer pipe. One rod is- driven by an electrical signal, and the
other rod acts as a variable tap whose output varies as a function of
388
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water level. The instrument is capable of accuracies better than 1 per-
cent of full scale. This is a commercially available system manufac-
tured by Marsh and McBirney, Inc.
WASTEWATER FLOW MEASUREMENT IN SEWERS USING ULTRASOUND
Reference (84) describes the use of newly developed ultrasonic velocity
measurement equipment in conjunction with ultrasonic level measurement
equipment for the measurement of sewage flow.
"Each ofi two exl&ting (combined] sewets in the. MUuxiukee (Wisconsin)
Sewage. System, one. 12-1/2 fit and the, other 5 fat Jin diameter, were
.#106 equipped initiaJUly. Subsequent discovety oft an excessive amount
ofi entrained air at the. 12-1/2 fit diameter. A ewe*. site necessitated the.
transfierral^ofi that equipment to a mono, favorable location upstream In
a 12-fioot diameter sewer. 'Performance o^ the. ultrasonic metens was
compared with other metering de.vlc.eA at each ofi the. location*. Rela-
tionships between average volume filow, wateA level, and average. veJtoc.-
£ty along Aele.cted horizontal chondx, ofi the. AeweA. C/WAA Ae.ctiom> W&UL
deteJtmtne.d. A continuous fLe.c.ofui o£ filow wa& di&played and x.e.c.oftd.e.d.
The. unit tn& tolled in the. 5-fioot dlameteA. A ewe*, hat, operated fan. a pe-
fiiod ofi 18 month* without fiailuA.e. and ha& tuLqyJbuLd. only routine, maln-
te.nance.. SimWvtly the. x.elocate.d unit tm>talle.d at the. 12-fioot diame.-
teJt AeweA Atte. ha& opeAate.d without fiailu/te. A-ince. it* installation. Wo
deterioration oft the. ul&ia&onic. t^an&duceA probes ha& been detected to
date -indicating tkeAjt suitability fiox. use -in the sewefi environment. The
electronics ofi the ultrasonic, velocity metering, unit were modifited to
Include peak protection, automatic gain control, and automatic, trigger
control to minimize the ejects ofi variations In the. solids loading."
Further observations concerning use of the ultrasonic equipment are as
follows:
a. Similar equipment has been used in Japan to successfully
measure full pipe flow of return sludge with high solids
loadings. For practical line diameters, say from 0.2 to
5m (0.5 to 16 ft), no operational limitations due to sus-
pended solids would be expected.
b. Entrained air bubbles were found to cause operational
problems because of dissipation of the ultrasonic pulse
due to scattering by the bubbles. Therefore, it is
recommended that measurement sites be selected which are
reasonably free of severe upstream agitation which would
cause air entrainment.
c. Difficulties with level gage performance resulted from
standing ripples in the sewage surface which interfered
with echo returns. This was alleviated by moving the
level sensor a few feet to a point where the sewage sur-
face was more still.
389
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d. Comparative figures of flow as measured by the ultrasonic
equipment with those measured by other metering devices
are not given for the demonstration sites described.
e. Total system cost for each site was about $15,000. Fu-
ture simplifications of the ultrasonic circuitry made
possible through more extensive use of integrated cir-
cuits have the promise of reducing this system cost by
a factor of two or three.
BIOLOGICAL TREATMENT OF COMBINED SEWER OVERFLOW AT KENOSHA, WISCONSIN
Reference (85) describes the design, construction, operation and two
year evaluation of a biological process used for the treatment of po-
tential combined sewer overflow. A 76 MLD (20 MGD) modified contact
stabilization process plant was constructed on the grounds of the city's
existing 87 MLD (23 MGD) conventional activated sludge plant at a total
cost of 1.1 million dollars.
"Vu/ung 1970 while. design and con&tnuction o& the. demonstration sys-
tem fiacilitieA WA occuwing, a pJiogiam to determine. the, quality o&
the. combined &&aesi OUCA^OMW in K.e.no&ha wa& carwied out. ThL& include.d
meaAusieme.nt o{ nainfiall, combined &eweti oveJifilow quantity and quality,
and influent quatlty to the, WPCP (wateA pollution control plant) dating
Flow measurement equipment was installed in the outfall lines of three
overflows, known as the 57th Street, 59th Street, and 67th Street over-
flows. Depth recorders installed were operated on a differential pres-
sure basis.
"Inert nitrogen ga& wa& inttLodu.c.e.d into tubing which ftan betu)e.e.n the.
Aeco/tdeA. and the. bottom o& the. outfall &eif)eJt. M the, &toM (ke.ad] in
the. &eM&L i.ncJte.a&e.d, ptwpofitianat to the, depth. o& £Ccw>, causing
the. pfLeA&u/Le. within the. tube, to in&ieaAe.. Thi& incJieaAe. *.n pJieAAufie.
wat> c.onveJtted to depth fiejading& and fte.c,onded on a cinculat chant. The.
chant wa& dividzd into 24 e.qu.at &e.ction& and dfiive.n by an 8 day clock."
Depth-discharge relationships were developed for the three overflow
lines by means of dye tests. However, no details of the test proce-
dures were given.
As a result of an unsuccessful attempt to correlate rainfall volumes
with overflow volumes, it was disclosed that the overflow measuring
devices were of questionable accuracy. In some cases, the volume of
overflow measured exceeded the volume of rainfall over the combined
sewer area. Apparently, the depth-discharge relationships were not
accurate and so the overflow data were not used.
390
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Measuring sites at the 57th Street and 59th Street overflows were aban-
doned in 1972. The depth recorder at the 67th Street site was moved
upstream above the weir diverting flow to the interceptor sewer. The
end of the bubble tube was placed just upstream from the overflow
mechanism, and a formula for broad-crested weirs was used to convert
level over the weir into flow rates and volumes. Flows computed in
this manner were used to estimate the total volume of overflow to the
demonstration treatment plant.
FLOW AUGMENTING EFFECTS OF ADDITIVES ON OPEN CHANNEL FLOWS
Reference (86) describes some laboratory experiments conducted to study
the effects of polymer additives on open channel flows. Two sheet
steel channels 18m (60 ft) long and painted initially with epoxy paint
(n=0.009) and later with a sand and paint mixture (n=0.013) were used
in the tests. One channel was rectangular with a bottom width of 15 cm
(6 in.) and a side length of 15.2 cm (6 in.) while the other was trape-
zoidal with a bottom width of 12.7 cm (5 in.), a 60° interior angle,
and a side length of 15.2 cm (6 in.). Slopes could be adjusted to 0,
1, 2, 3, and 4%.
A series of tests was conducted to determine the effects of a polymer
additive on four types of flow measurement devices. A Parshall flume,
90° V-notch weir, and suppressed rectangular weir were adapted to the
smooth-wall rectangular channel and tested at a 1% slope, while a
Leopold-Lagco flume and a 90° V-notch weir were tested in the smooth-
wall trapezoidal channel at a 2% slope. No sizes are given for any of
the flow measurement devices, nor can they be estimated from a photo-
graph in the report except to note that the crest height of the rec-
rangular weir is low (perhaps 20% or less of the channel depth) as is
that of the V-notch weir for use in the trapezoidal channel. Con-
versely, the V-notch in the weir used in the rectangular channel appears
to "run out" at the top of the channel.
The general procedure followed was to calibrate each device in place
using tap water, and then to inject the polymer to yield a predeter-
mined concentration and develop a new calibration curve. Head was
measured using a pointer gage ."usually at the inlet to the device".
A stop watch, 19£ (5 gal) bucket, and scale were used to determine
flow rates under 570 t/m (150 gpm) (where most of the data were taken),
while an orifice meter was used for higher flow rates.
Calibration of all devices was affected by the addition of polymers.
The Parshall flume was least affected, while the V-notch weir suffered
a greater calibration curve shift (e.g., discharge could be understated
by over 50% of all but the lower flows). The Leopold-Lagco flume and
the rectangular weir ceased to be effected as flow measurement devices
above a transition flow rate. The data are inconclusive, but indicate
that polymer additives can affect primary flow measuring devices and
point out the need for careful research in this area.
391
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SURGE FACILITY FOR WET AND DRY WEATHER FLOW CONTROL
Reference (87) represents the culmination of a 3-year demonstration
project which encompassed the design, construction, operation, testing
and evaluation of a surge facility designed to provide flow equaliza-
tion and some degree of treatment to all storm flows and to provide
rate control of all wet weather and dry weather wastewater flows to
interceptor sewers.
The principal elements of the facility are a sedimentation-equalization
basin, a clarifier, a storage pond, a chlorine contact basin, and a
sludge digester. Flow and hydraulic measurements include: (a) influ-
ent to the sedimentation-equalization basin; (b) underflow from the
sedimentation-equalization basin to the clarifier and the storage pond;
(c) overflow from the sedimentation-equalization basin directly to the
storage pond; (d) water surface elevation of the sedimentation-
equalization basin; and (e) effluent to the chlorine contact basin and
the receiving stream.
The influent metering structure is a Parshall flume with a 0.30m (1 ft)
throat width having a maximum capacity of approximately 30 MLD (8 MGD) .
The influent flow transmitter to the control building can be used to
control a flow proportional sampler of the influent.
Underflow from the sedimentation-equalization basin is measured with a
15*2 cm (6 in.) magnetic flowmeter. The underflow can be set at any
desired rate up to 8.7 MLD (2.3 MGD).
Overflows from the basin are measured by four sharp-crested rectangular
weirs, totaling 2.54m (100 in.). Head on the weirs, and the water sur-
face fluctuations in the sedimentation-equalization basin, are monitored
with a Stevens Type F water-stage recorder. Time gears were selected to
give an 8-day chart, and stage gears were selected to give an indication
of 0.06m/cm (0.5 ft/in.) of chart or 0.012m/cm (0.1 ft/in.) of chart,
depending on the depth variation expected during any particular testing
period.
Effluent from the facility is measured with a combination of a 15.2 cm
(6 in.) Parshall flume and a 137 cm (54 in.) sharp-crested rectangular
weir. The two flow measuring devices are set to give a combined capac-
ity of 22.7 MLD (6 MGD). The effluent flow transmitter can be used to
control a flow proportional sampler of the effluent.
No discussion of problems with flow measurement equipment is given in
the report. Flow data presented in the report appear to be complete
and accurate. "O&tfe. the, 4M.iZu.un£ and andeA^loia meie^ed and the. wateM.
monAtoft.e.d c.ont*niwu&ly , -it WOA JieZativzly e&5£/ to produce, a
nat
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A PORTABLE DEVICE FOR MEASURING WASTEWATER FLOW IN SEWERS
Reference (88) is a final report of a program to develop a portable
device capable of measuring wastewater flow in sewers. The work con-
sisted of: an investigation of the theoretical approach to be used;
laboratory investigations and experiments to develop design criteria;
design and fabrication of two prototype units; 'and field testing and'
evaluation of these units .
Methods investigated for determination of velocity in the sewer, prior
to selection of the heat pulse method for development, are as follows:
a. Capacitance - Air Bubble Method
This method depends upon the electrical capacitance of
the wastewater flow cross-section and the effect on this
capacitance of the displacement of air bubble tracers as
they rise and are swept downstream past a capacitor
plate. This approach failed due to "background noise"
and, at low velocities, due to too rapid rise of bubbles
in the flowing water.
b. Inductive Method
a dsu-ve. coll zxA.vun.aJi to the. pipe. to cneate. an
audio fyie.qu.ency magnetic. fileld. The. magnetic {leld, Jin
tuxn, Induce* an. eddy cjjjuuunt in any neanby conductor,
Auch 06 the. watex. In the. pipe.. Thl& eddy cuAA.e.nt can be.
detected by Aentltlve. pickup collb located neMi the. pipe.
wwesit. Ifi the. wateA li> moving, the. signal dete.cte.d wWL
be. out oi phate. with the. &&LongesL ttgnal x.eAu&Ung faom
d, the. amount
oi tki& pha&'e. Ahifit being cowie&ated mJth elective
velocity."
Failure of this method was attributed largely to the ex-
treme smallness of the signal to be detected.
c. Electromagnetic Flowmeter
This included the rather commonly used electromagnetic
flowmeter approach for measurement in a full pipe. How-
ever, it was decided that bulkiness of the equipment
precluded its use for a portable, easily installed
instrument.
d. Electric Current Method
A voltage was applied across a dynamic test section, be-
tween two electrodes in direct contact with the water. A
393
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change in d-c voltage was observed as velocity changed.
An increase in current was observed as velocity de-
creased, with the filled cross-section remaining the
same. Problems encountered were random changes due to
d-c signal "drift", and plating by the direct current on
the exposed electrodes. .
The method finally selected for more detailed investigation involved
the timing of a heat pulse as it traveled down the pipe. Thermocouples
were used to sense the travel of heat induced by the injection of steam
into the flowing water. Measurement of the cross-sectional area of
flow was done by the use of capacitor plates to sense the change in wa-
ter level in the sewer pipe.
"Jwo phototype, gage* WVUL ^ab^Ldat&d. Tke. ov&tatt ac.c.unac.y oi tke. i, at bz&t, ±75 peAc.e.nt."
JOINT CONSTRUCTION SEDIMENT CONTROL PROJECT
Reference (89) describes a demonstration project which consists of:
(a) the implementation, demonstration, and evaluation of erosion con-
trol practices; (b) the construction, operation, and demonstration of
the use of a stormwater retention pond for the control of stormwater
pollution; and (c) the construction, operation, and maintenance of
methods for handling, drying, conditioning, and disposing of sediment.
As part of the project, a gaging and sampling program was conducted to
determine the effects of urbanization on storm runoff and water quality
of natural areas.
Four automatic flow gaging and water sampling stations were installed
on small streams of the study area. Two of the stations were installed
adjacent to each other on streams just upstream from their junction.
One of these streams drains an experimental watershed and the other
drains an adjacent reference watershed. Two other gaging and sampling
stations were established immediately upstream and immediately down-
stream from a 1.6 Hectare (4 acre) pond.
At three of the gaging sites, precalibrated, broad-crested, V-notch
weirs developed and tested by the U.S. Department of Agriculture were
installed.. At two sites, the concrete weir caps have 2:1 side slopes;
at the third site, side slopes of the weir cap are at 3:1. At the
gaging site downstream from the four-acre pond, a sharp-crested, com-
pound, 90°, V-notch and rectangular weir was installed.
A Stevens Duplex Water-Level Recorder Type 2A35 was used to simultane-
ously record water levels at the two adjacent stream sites. A Stevens
Type A35 water level recorder was used upstream from the pond, and a
Belfort liquid level recorder was used at the downstream site.
394
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A Gurley pygmy current meter was available to perform additional stream
gaging, but was used primarily to check the calibration of the perma-
nently installed weirs. v
The weirs and level recording devices used are said to "have proven to
be accurate, reliable, and easy to maintain". However, it was found
necessary to clean out sediment above the three U.S.D^A. weirs "—aAtefi.
(MchAtcwn and AomeMme* undvi ba&e. {tow c.ondJiAJLon& to maintain the.
caO,bfUVUan and ac.CMM.zy ofi th
-------
Because of the extended period of high river stage, flow measurements
during wet weather were generally not obtained in the sewers or over-
flow points. During this period, most of the flow measuring sites were
either submerged or at least intermittently affected by high water.
Overflows at one point were estimated by use of the Manning formula,
and at another point by use of a current meter.
Stormwater runoff was measured at four gaging sites on storm sewers.
At three sites, flow was measured by means of weirs and bubbler re-
corders. During periods of high river stage, one of these sites was
submerged or affected by backwater, when no record was obtained. Run-
off at the fourth site was determined from a stage-discharge relation-
ship established by current meter measurements. A concrete sewer line
crossing the channel provided a permanent type control. The rating
curve was extended an undisclosed amount above the highest current me-
ter measurement.
COMPUTER MANAGEMENT OF A COMBINED SEWER SYSTEM
Reference (91) describes a computer-controlled "total systems manage-
ment" complex, which affects much of the combined sewer system of
Seattle, Washington. Computer-augmented treatment .and disposal (CATAD)
takes advantage of storage in the sewers to limit overflows, and se-
lects overflow points based on water quality data.
...... ..... ' ' '
Development of the control system included the installation of 36 re-
mote sensor stations and the construction of 15 gate-driven regulator
stations. Work continues on a fully automatic optimizing model to
program decisions so the system can maintain an 80% overflow reduction.
"Wat&i le.\>eJL& at many location* ate. pft.oba.bly the. mo&t important tingle.
category o£ information r.e^uir.ed to calculate, filom and trigger. certain
type* 0|J alarm*. fty incorporating Manning'* equation*, variou* otifiice.
and vioir. formulae. and pump e.Uiciency curve*, -it i& po**ible. to calcu-
late. ilow at almo&t any location In. the. *y*tem. The. compute*, check*
wtvt eZevation* wutti n.e.ivience. to ovesifilou} weir* to generate. pre.-
alatm& be.6ofi.e- oveA^low* take, place, and/oft, actual alarm* a£teA the. over.-
Aeow had begun. Monitoring , control and modeling a& the. entitle. &y£>tw
depend upon &lou) information, faon many location*, &ome. oi which cannot
be. obtaine.d ^m wateSi level me.aAufi.eme.nt!> alone.. In the. CATAt? &y&tw,
additional on-line. £low meoAuAing te.chniqueA one. employed'.
1. flow meja&uAing
ate. in&taHe.d at vaniouA location*.
2. A catlbstjated pfiopetleA. type. filoimzteA. it> monitofied at the.
Point treatment plant &ite..
3. lFon.ce. main. pieAAusie. calibration method* ate. u&ed at pump
AtationA whesie. theJie. ii> Au^icient friction head lo£>& to
calibrate, the. fiotce. main at vaniou& &low range*."
396
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In addition, more than 100 Palmer-Bowlus flumes are installed in man-
hole locations. A computer program has_been applied for rating these
measuring flumes, using data including sewer diameter, shelf height,
flume side slopes, and elevation of vertical side slopes.
Level sensors used in the system are generally pneumatic bubblers with
back pressure read by a differential pressure transmitter. The accu-
racy of measurements was checked by direct level measurements to bring
instrument calibration of the various stations into agreement with the
system datum. It was determined that the overall accuracy probably ap-
proaches about 2% of the full scale measurement.
Project experience demonstrated that manufacturer's pump unit perform-
ance curves may be used to calculate reliable flows provided that crit-
ical analog sensors, particularly pump speed sensors, are reliable;
Because flows calculated using performance curves had been considered
dubious, force main pressure sensors were installed at many pump sta-
tions to provide alternative means of calculating station discharge.
As a result of checking the pressure gages using the salt velocity
method, it was found that flows thus calculated are not entirely'reli-
able due to rapid fluctuation of analog pressure values.
Deficiencies in the flow calculation procedures for regulator stations
were revealed. No allowance had been made for the effect of intercep-
tor backwater affecting the tailwater at a regulator gate and no tran-
sition had been provided between fully-submerged and free .discharge
conditions. A backwater allowance was added, and a method of calculat-
ing the degree of gate submergence was developed.
CHARACTERIZATION AND TREATMENT OF URBAN LAND RUNOFF
Reference (92) describes a project to characterize the runoff from a
4.3 sq km (1.67 sq mi) urban watershed in Durham, North Carolina with
respect to annual pollutant yield. The U.S. Geological Survey operates
a continuous stage recorder and two digital punch tape precipitation
recorders within the basin. Stream-flow control is provided by a
shallow V-notch weir located on Third .Fork Creek some 21m (70 ft) down-
stream from a bridge culvert and 11.3 km (7 mi) upstream from the mouth
of Third Fork Creek. Water quality samples were taken from the center
of the stream approximately 1.5m (5 ft) below the weir. Thus, rainfall,
runoff, and water quality data were gathered for the basin and analyzed.
The USEPA Storm Water Management Model (SWMM) was also evaluated with
respect to actual conditions as measured in the field and "was judged
to predict peak hydrograph flows and total hydrograph volumes with rea-
sonable accuracy; however it was not judged effective for predicting
pollutant concentrations".
In order to assess the impact of varying types of land use. within the
basin on urban runoff quality, 5 storms were manually sampled at sub-
basin discharge locations. A control section, usually a pipe or box
397
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culvert, was utilized with Manning's equation to arrive at stage-
discharge relationships for each basin sampled. The stage was manually
read when a sample was taken. No accuracy estimates are available.
OTHER USEPA PROJECTS
Among USEPA projects for which final reports are not available is a
project (EPA S-802400) to demonstrate disinfection and flash treatment
of combined sewer overflows at Syracuse, New York. Disinfection is ap-
plied for one minute after solids removal by high rate screening. Flow
of combined sewage is measured from three pumping stations to installa-
tions of fine mesh and micro screens. Also, flow in solids return
lines from the screens is measured and used to control backwash of the
screens. Flow from the three pumping stations is measured by Brooks
electromagnetic flowmeters. Solids return from the screens is measured
with a weir and a Badger Meter, Inc. float level indicator. Problems
were experienced in printed circuits of the signal converters used with
the Brooks electromagnetic flowmeters. Initially, other problems
necessitated that adjustments be made by Brooks' representatives.
A USEPA grant project (EPA Y-005141) with the Monroe County Pure Waters
Authority is to develop a master plan for treatment, conveyance, or
holding alternatives to effectively handle the combined sewer overflows
from the Rochester, New York, sewer system. Flow quantity and quality
data collected for the project are to be used in calibrating the USEPA
Stormwater Management Model. The master plan is to be so developed to
provide guidelines for use in preparing such plans for other cities.
Measurements of thirteen combined sewer overflows, and at four loca-
tions in interceptor sewers, are being made. At five of these loca-
tions, Badger Meter, Inc. ultrasonic flowmeters are used in conjunction
with Badger ultrasonic .water surface level indicators. At eleven loca-
tions, Badger ultrasonic level indicators only are used to record head
over weirs or to provide data for use with the Manning formula. A
Fischer-Porter bubbler gage above a combination weir-orifice is used
for flow measurement at one site. All data are transmitted to a cen-
tral computer. Redesign of the ultrasonic head probes was found neces-
sary due to echoing in the sewers, but they are now reported to be
operating satisfactorily. Problems of interfacing with the computer
were experienced, but very good operation has been obtained after six
to eight months' experience.
A project (EPA No. 11024 FIU) was for the design, fabrication, and
testing of a prototype 30.5 cm (12 in.) vibratory sewer flowmeter. The
flowmeter to be developed was to operate on the principle that the re-
action of flowing material to a mechanical vibration applied to the
stream boundary in a direction transverse to the direction of flow is a
direct measure of mass flow rate. The essential elements are an actu-
ator to impart a vibratory force or motion to the flowing material and
a sensor to measure the reaction. This type of device has been used
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successfully for measuring very small flows, but the mechanical prob-
lems with equipment for use in a sewer were not successfully solved
with the time and funds available. '.:., . .
A project (Contract No. EPA 68-03-0341) with Gushing Engineering is for
the "Development of an Electromagnetic Flowmeter for Combined Sewers",
which may result in a device capable of measuring flow under -open-
channel conditions as well as in a full, pressurized pipe is in prog-
ress. The open channel electromagnetic'flowmeter will have a primary
unit or transducer (i.e., the portion through which the fluid flows)
that is not considered to be appreciably more-• complicated than the con-
ventional instrument; however, it does require more sophistication in
its secondary unit (i.e., in its signal conditioning unit). The pri-
mary unit is very similar to standard electromagnetic flowmeters ex-
cept that in this case a manifold of detection electrodes (as opposed
to a single pair) are employed so that measurement can be made through-
out the varying depth of the liquid. The outputs of the detection
electrodes are fed into an adder network which totals the voltage ; ;
sensed in accordance with height of flow. ,; '
The EPA has contracted (Contract No. 68-03^2121) with Grumman Ecosystems
Corporation for the development of a new,non-intrusive, low cost, pas-
sive measurement system capable of monitoring flow in storm, combined,
and sanitary sewers. The system's concept involves a proprietary tech-
nique of utilizing the sound emission resulting from the interaction of
fluid flow with a discontinuity of a solid surface. In the application
to sewer flow, a discontinuity is any inherent change in the sewer
cross-section, slope, or direction that can significantly affect the
flow area or direction. Laboratory investigations directed to optimize
system design details for sewer installations, and analyses which will
relate theory and test data to measurement system design objectives and
applications are currently underway. By proper signal processing, the
acoustic emission flowmeter can be made to differentiate between sound
that is indicative of and generated by the quantity of flow and noise
caused by noncorrelatable secondary flow processes and general back-
ground noise. Several factors may affect sound production and transmis-
sion in wastes such as a suspension of bubbles, temperature gradients
and stratification, etc. These areas must be investigated and either
avoided or compensated for by selection of sound pickup locations.
PROJECTS BY OTHER FEDERAL AGENCIES
Federal agencies which have been active in development of improved flow
measurmenet equipment and methods, with a brief description of their
work, are given below. Other Federal agencies have carried on similar
useful projects in past years, but have been omitted where -information
on possible recent work was not available. The information presented
here was obtained either by telephone or personal interview. ;
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Agricultural Research Service
Work on improved designs of trapezoidal-type measuring flumes to over-
come sediment problems is being conducted in Phoenix, Arizona.
Bureau of Reclamation
Radioisotope Flow Measurement - Equipment and methods for measuring
flows in canals, pipelines, and turbines-with radioisotope tracers have
been developed by the Bureau during the past ten years. Public resist-
ance to injection of radioisotopes into water supplies has minimized
their use.
Ultrasonic Flowmeter - Ultrasonic flowmeter equipment furnished by^the
Badger Meter Company was tested in a 61 cm (24 in.) diameter pipeline
and in a 76 cm (30 in.) wide channel. A measurement accuracy of ±2%
was obtained in the pipeline. A significant conclusion was that the
flowmeter transducers should be installed in direct contact with the
water rather than on the outside of the pipe.
Rotameter-tvpe Flowmeter - Combined rotameter-type flowmeter and flow
controllers of 25.4, 30.5, and 35.6 cm (10, 12, and 14 in.) sizes were
studied in the laboratory. These devices totalize flow, indicate flow
rate, control flow to preset rates, and provide shutoff. Further field
operation and experience is necessary to fully evaluate the devices.
The Bureau of Reclamation conducts a continuing research program in
the fields of water system automation and flow control. Studies in the
use of electromagnetic and ultrasonic methods of flow control are in
progress.
Corps of Engineers
Recently, Westinghouse ultrasonic flow measurement equipment has been
installed on the Columbia River to provide improved information on
powerplant operation. This work was performed by the personnel of the
Portland District in cooperation with the U.S. Geological Survey.
Satellite transmission of data is being investigated in the New England
Division. Telemark data transmission systems are being discontinued
and are being replaced by radio transmission. It is expected that data
transmission in the future will be tied to the National Oceanic and
Atmospheric Administration System of Automation of Field Operation and
Services.
Geological Survey
The Water Resources Division of the Geological Survey maintains a con-
tinuing program to improve water measurement devices and procedures.
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Recently, a flow measurement device for measurement of storm runoff in
sewers has been developed, and a number of them are being installed in-
several sewered catchment basins. The device functions within the
sewer under both open-channel and pressure flow conditions, and is said
to cause only an insignificant amount of head loss. Undfer open-channel
conditions, the meter functions as a venturi flume. Fpr pressure
flows, the device operates like a modified venturi meter. This flowme-
ter is very similar to that developed by Dr. Harry G. Wenzel of the
University of Illinois. A significant difference is that the upper po-
sition of the pipe is unconstricted, reducing discontinuity between the
open-channel flow rating and the pressure flow rating.
PROJECTS OUTSIDE THE UNITED STATES
The reader is cautioned not to assume that all the flow measurement •
research today is being .conducted in the United States. Most industri-
alxzed countries are active in this area, and new or improved flow
measuring devices and techniques are being reported by foreign investi-
gators. Coverage of all foreign research simply was outside the scope
of the present effort, but would be a fit subject for a future study. '
However, mention will be made of one Canadian development recently re-
ported by Marsalek (93) because of its promise for application at sites
troubled by surcharging. It is essentially a flume-dilution combina-
tion for sewer flow measurement. The equipment involved is all porta-
ble and suitable for manhole operation. At the primary wastewater
characterization site a Palmer-Bowlus type flume, a water level re-
corder (a capacitance-type probe was used In this case), and an auto-
matic discrete sampler were installed. At a manhole sufficiently
upstream to assure that complete mixing would occur a tracer supply and
metering feed pump were installed. •
Under ordinary (open channel) flow conditions only the equipment at the
primary site is in operation. When the water level, as measured by the
capacitance probe, reached a pre-determined value indicating that sub-
mersion effects would be seriously degrading discharge values as meas-
ured by the flume, an alarm relay activates the tracer feeding pump at '.
the upstream site. The chemical dilution technique is applied for the
high flow periods by analyzing the samples collected by the automatic
sampler to determine tracer concentrations.
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SECTION IX
11 ,,„„,::", ' ' &
FUTURE AEEAS OF RESEARCH AND DEVELOPMENT
Although the general state of the art of flow measurement has come a
long way since the days of Sextus Julius Frontinus (e.g., we can accu-
rately measure cryogenic flows, liquid sodium flows, mixed gas and
vapor flows, etc.), the most common flow measurement devices and tech-
niques used in sanitary engineering are but modest improvements upon
nineteenth century (or earlier) developments. This is not surprising
in view of the National priorities that have been given to space and
nuclear energy programs, and the concomitant application of resources
to the development of technologies directed toward, the solution of
problems in these areas. As was pointed out earlier in this report, we
are now becoming more and more aware of the importance of accurate
sewer flow measurement and, in recent times, have begun to devote in-
creasing attention to it. Storm and combined sewer flows, as noted,
are among the most difficult to measure well, and much remains to be
done before we can claim that the state of the art, as being practiced,
is equal to the task.
As a result of the activities conducted during the course of this
study, including the review of older research and development projects
as well as current and on-going,ones, it appears that there are several
promising research areas that could produce improvements within a
short-term time frame. They have been divided into three categories:
general research, which is more basic or fundamental and applicable to
a number of different classes of flowmeters; applications research,
which deals with the engineering required to adopt already-developed
building blocks into flow measurement systems suitable for the storm
and combined sewer application; and demonstration research, which is
the actual field use and evaluation of existing equipment that either
has not been tried before or about which there is presently insuffi-
cient information.
Several promising activities within each area will be discussed. No
attempt to be exhaustive or all-inclusive has been made. Rather, the
activities suggested have been selected because of a critical need, the
promise of a high probability of positive results, and/or the immediacy
with which results could be obtained. The selections are necessarily
somewhat subjective, and doubtless some readers will be concerned that
one of their "pet" areas has not been included. The writers can only
hope that any such criticism will be tempered by the realization that a
complete coverage of all possible contributory research could more than
double the size of this already somewhat lengthy report.
Two general recommendations will be treated outside the just mentioned
categories because they tend to overlap and are a bit more policy/
priority than specific task oriented. First, there is a need for a
402
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facility where controlled flows of wastewater can be maintained so that
varxous alternative devices and techniques can be tested in a side-by-
side fashion. It is imperative that this facility be capable of opera-
tion with actual sewage as well as water in view of possible
interference effects to some flow measurement equipment that might be
caused by the former. A facility was developed as a part of a USEPA
funded study and evaluation of a periodic flushing system for combined
sewer cleansing by FMC Corporation. It,has variable slope test sewers
of 30.5 and 45.7 cm (12 and 18 in.) diameters and can utilize actual
sewage. It is recommended that this facility be evaluated for the pur-
pose of side-by-side flow measurement device testing and so utilized if
indicated. ,
The second general recommendation arises from the very nature of the
storm and combined sewer application itself. It is strongly recom-
mended thatpriority be given to the development of portable flow meas-
urement devices that could be used for overall survey work, for
gathering field data for use in the development of computer stormwater
management models, for conducting infiltration/inflow studies, and the
like. The importance of a portable flowmeter for each of the cited
uses is well known and will not be belabored here. The problem is that
the need is still largely un-met. Of the following research recommen-
dations, it is recommended that those activities that will be contrib-
utory, to the development of portable devices be undertaken first.
GENERAL RESEARCH
Much remains to be learned about -the physics of complex flows such as
stormwater or combined sewage. They are multi-phase mixtures contain-
ing solids, liquids, and gases and are unstable, with constituents go-
aag into and out of solution as the flow progresses. .When combined
with the problems introduced by nonuniform, unsteady turbulent flow
the research possibilities are mind-boggling. Only three, which the
^^elS ^ are °th °f immediate concern and reasonable tractibility,
will be discussed.
Effects of Entrained Air and Solids
Entrained air and solids in the flow can have an effect on several dif-
ferent types of flow-measuring equipment. One of the most recent and
promising methods of flow measurement utilizes ultrasonic equipment
which is known to be adversely affected by these elements. Experience
to date has shown that the presence of heavily concentrated air bubbles
in the flow interferes with operation of ultrasonic flowmetering equip-
ment. This is true even when the bubbles are so small that they are
hardly, visible. The only solution thus far proposed is to install the
flowmeter where such bubbles do not form; that is, to avoid locations
403
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below drops, chutes, and hydraulic machinery which cause air entrain-
ment in the flow. A method for overcoming this restriction of meter
applicability is needed, and should be investigated further.
A similar interference by solids suspended in the flow has been noted.
Although methods for overcoming the effects of larger, more widely
spaced suspended solids have been developed, fine silts remain a prob-
lem. Further study to better understand and overcome such effects on
ultrasonic velocity measuring devices is recommended.
Polymer Effects
The introduction of selected polymers to pipe flows has been demon-
strated to significantly increase the pipe carrying capacity. Flow
increases of as much as 240% at a constant head have been achieved.
Field tests reported by The Western Company (94) on a 61 cm (24 in.)
line demonstrated that surcharges of greater than 1.8m (6 ft) could be
eliminated by polymer additives. Similarly, the capacity of open chan-
nels has been increased through use of friction-reducing additives,
although to a lesser extent, as noted by Derick and Logie (86).
The addition of polymers to the flow can have a significant effect on
the calibration of certain types of flow measuring equipment, as also
reported by Derick and Logie (86). Although they only tested flumes
and weirs, effects could be even more pronounced in those devices that
presuppose velocity distributions in the flow. Ultrasonic flowmeters
are a particular case in point. For example, little is known about the
effect of changing the viscosity of the water on the character of the
ultrasonic pulse through the water, or about the reduction of turbu-
lence causing a change in velocity distribution in the cross-section.
Because of the potential for increased use of polymers for flow control,
study of their effects, especially on ultrasonic flow measurement
equipment, is recommended.
Velocity Distribution
Although a significant effort has been made to define the relationship
between average velocity along a horizontal chord or traverse, eleva-
tion of the chord or traverse, and the average velocity in the cross-
section, much more work would be helpful in reducing the cost of flow
measurements. Theoretical computations and laboratory and field obser-
vations have been made in the past, but a consolidation of known infor-
mation, reinforced with selected additional data, would be quite useful,
since many of the flow measuring devices infer average velocity from
point or chordal measurements. This is particularly true with respect
to ultrasonic flow measurements, where the average velocity along a
chord or traverse between two meter probes is measured. Further knowl-
edge of these relationships would also be useful with other flow meas-
urement devices where flow is computed from the product of average
velocity in the cross-section and the cross-sectional area.
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APPLICATIONS RESEARCH '
The state of the art and technologies are now at hand to allow the de-
velopment, based on already established building blocks, of improved
flow measuring devices for application to the storm and combined sewer
problem. A few examples will be discussed.
Automated Dye-Dilution Devices
As discussed in Section VI, dilution techniques are very promising for
application to the measurement of storm or combined sewer flows, espe-
cially in view of the new fluorescent dyes now available. Suitable
ifavS?Lr l^ controlled-rate °r ^ug injection of dye solutions
is available. Automatic sampling equipment to allow reliable gathering
of representative samples and fluorometers for automatically measurin-
dye concentrations are also available. There has even been work done°
on laser stimulation of fluorescence which could allow remote observa-
tion _ of dye concentrations without direct contact with the flow. Pres-
ent integrated circuit technology would allow automatic conversion of
dye concentrations to flow rates, in digital form, for indicating and
recording and transmitting to central locations. It is even possible
to develop a portable, battery-powered version that could be used for
field calibration of existing flow measurement devices. It is recom-
mended that a project to integrate these building blocks into an auto-
matic flow measurement device be established, with emphasis on
portability.
Portable Ultrasonic Devices
Sufficient field experience is now available to demonstrate the utility
of ultrasonic equipment for the measurement of sewage flow, including
stormwater and combined sewage. Development of portable equipment could
expand the usefulness"of this kind of flow measurement device to meas-
urements of the miscellaneous type, such as in infiltration studies, to
check the effluent from industrial plants, and for many other purposes.
Basically, ultrasonic-flow measurement equipment is adaptable to com-
pact packaging, as no large, heavy parts are required, even-for measure-
ments of large flows. Three separate packages might be developed - a
level gage, several sets of meter probes, and associated electronic
instrumentation. Provision should be made for installing the probes
either inside or outside of closed conduits. Again, the fundamental
building blocks are at hand, and it is recommended that such a proiect
be initiated as soon as possible.
New Flumes
As noted in Section VI, there has been extensive research work performed
on a variety of new flume configurations, with resulting designs that
offer wider ranges, greater self-scouring charaeteristics, better
405
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submerged performance capabilities, etc., as compared to the more tra-
ditional designs, especially the Parshall flume. It is recommended
that a project be established to consolidate the existing information
on these efforts and, based upon this, to develop a flume possessing
the most advantageous attributes in light of present day technologies
and the storm and combined sewer application. For example, it mxght
happen that a trapezoidal cutthroat 'flume with an automatic, electronic
dual head comparison (Hb/Ha) and critical/submerged/pressurized flow
algorithm shift integrated circuit card would offer great promise.
Such a design is totally within the present state of the.art and could
be effected at a reasonable cost.
/
Ultrasonic Level Gages
As secondary elements in flow measurement devices, ultrasonic level
gages show considerable promise-for the storm and combined sewer appli-
cation. They obviate the self-cleaning requirements of many secondary
elements, offering the advantage of no requirement for contact with the
flow stream whatsoever. Their use has been fraught with difficulty,
however, especially in settings such as a manhole application. The
problems, from discussions with various field and applications engi-
neers, would appear to stem mostly from spurious or false signal returns
due to echoing from the installation structure. The problem has been
encountered in many applications, e.g., the Rochester project, and has
been independently solved (or apparently so) almost as many times. *or
example, the USEPA National Field Investigation Center, Cincinnati, has
experienced such problems with different makes of equipment and has de-
veloped an inexpensive modification that apparently corrects the prob-
lem. It is recommended that a project to review the history of such
experiences, including problem and solution descriptions, be prepared
and procedures developed for the use of ultrasonic level gages in such
applications.
DEMONSTRATION RESEARCH
There are several flow measuring devices, either presently available or
virtually ready to be introduced, that offer considerable promise in
the storm and combined sewer application. However, information about
their use in such a setting is lacking, but could be gained from test-
ing in a suitable facility as discussed earlier or from other field use
such as a-demonstration as an adjunct to an on-going project; thus,
definite recommendations as to their suitability or fitness as storm or
combined sewer flow measurement devices can be made. Some of these
Will be briefly discussed.
Venturi Meter/Flume
These flow measuring devices are designed to operate under both open-
channel flow and full-conduit flow under pressure. Under open-channel
406
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aCt aS suPercritical flumes, but when completely
and under pressure, they behave more like modified venturi me-
ters. For open-channel flow, only the depth at a single (usually up-
stream) measuring section is required. When the pipe is flowing full,
and is under pressure, the flow is a function of the difference in the
upstream head and the head at, say, the meter throat or an exit head;
Two such devices have been recently developed - one by Dr. Harry G
oHhi'u I' f f^ UVf S±ty °f Illin°iS» 'and °- ^George
oi the U.S. Geological Survey.
ffiM (i8 Jn'} diameter test meter designed by Dr. Wenzel has been
sufficiently laboratory tested, but has not undergone field experience
to evaluate its self-cleaning characteristics and its hydraulS per?orm-
on a'61 L^rrr^ '""V PrOtOtype meter of larger' elze, at least
In VfS ?J n° diameter llne> be tested in an actual combined sewer
in line with an accurately calibrated meter of another type.
Several similar flumes designed by George F. Smoot for the U.S. Geolog-
JSJ r^7 b!en installed in storm or combined sewers. However!
there has not yet been sufficient field experience to allow adequate
%S?frT, I ^ ^It: ±S recommended that a flume of this design be
installed (preferably) in line with the meter designed by Dr. WeSel
a Calibrated meter of Bother type for further
Combination Thermal Flowmeter
Two thermal flow tube meters are manufactured by the Thermal Instrument
Company, one for measurement of flow in pipes that are flowing full and
another for flow measurement in partially filled pipe. Although dis-
°f theSe mSterS - Ascribed
the.
<**.*»<**** otthe. tabz to compete and
and cmblznt
. ' level.sensor
on the outside of the unobstructed pipe, in addition to the
velocity measuring sensors.
Very little experience has been gained with this type of flowmeter in
measurement of sewage. Meters are now in operation on 50.8 cm (20 in )
pipes carrying recycled pulp wastes. There is said to be no upper limit
on the size or range of these meters.
407
-------
Because of the obvious potential advantages of such nonobstructing me-
ters, it is recommended that they be evaluated in a line of moderate
size, but under conditions of both open-channel flow and full flow un-
der pressure. The test meter would be placed in line with a flow meas-
uring device of another type with proven accuracy.
Self-Calibrating Acoustic Level Gage
The "Aquarius" acoustic level gage described in Section VII offers
many apparent advantages over more traditional ultrasonic level gages
as a secondary element in a flow measurement system. These include:
complete independence from all environmental effects; almost an order
of magnitude greater accuracy than presently available; a low produc-
tion cost; portability, which includes the promise of outstanding bat-
tery life (up to one year); and immediate computer compatibility, owing
to its advanced, all-digital electronic design. At this time, however,
the device is so new that virtually no data (outside the laboratory)
are available to substantiate these promises in a field setting. It is
recommended that one of these devices be procured and installed, at a
site with a suitable primary device, alongside a proven head sensor in
order to demonstrate its real capabilities in a field setting.
High Range Open Flow Nozzle
The H-series flumes (or open-channel flow nozzles), that were developed
by the U.S. Department of Agriculture, hold considerable promise as
primary devices for successfully measuring storm and combined sewer
flows at many sites, as discussed in Section VI. In view of their low
cost and very wide measurement range, it is recommended that a project
be initiated to: (a) gather available information on the various flumes
of this type and other open flow nozzle designs; (b) analyze this de-
sign; and (c) fabricate and test such a primary device.
408
-------
SECTION X
REFERENCES
CITED REFERENCES
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411
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/2-75-027
I. RECIPIENT'S ACCESSIOWNO.
4. TITLE AND SUBTITLE
SEWER FLOW MEASUREMENT - A STATE-OF-THE-ART
ASSESSMENT
5. REPORT DATE
November 1975 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
', AUTHOR(S)
Philip E. Shelley and George A. Kirkpatrick
8. PERFORMING ORGANIZATION REPORT NO.
9, PERFORMING ORGANIZATION NAME AND ADDRESS.
EG&G Washington Analytical Services Center, Inc.
2150 -Fields Road
Rockville, Maryland 20850
10. PROGRAM ELEMENT NO.
1BB034;ROAP 21ASY;Task 034
11.
68-03-0426
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA-ORD
18. SUPPLEMENTARY NOTES
18. ABSTRACT
A brief review of the characteristics of storm and combined sewer flows is given,
followed by a general discussion of the need for such flow measurement, the types
of flow data required, and the time element in flow data. A discussion of desirable
flow measuring equipment characteristics presents both equipment requirements as
well as desirable features and includes an equipment evaluation sheet that can be
used for a particular application. A compendium of over 70 different generic types
of primary flow measurement devices, arranged according to the fundamental physical
principles involved, is presented along with evaluations as to their suitability
for measurement of storm or combined sewer flows. To illustrate the implementation
of the physical principles, a number of commercially-available devices for flow
measurement are briefly described. A review of project experience in flow measure-
ment is presented along with a summary of current and on-going research efforts.
Some thoughts on future areas of research and development are also given.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
*Flow measurement, *Flowmeters, *Liquid
flow, *0pen channel flow, *Pipe flow,
Stream flow, Storm sewers, *Combined
sewers, Overflows, Manholes, Outfall
sewers, Sanitary engineering, Urban areas,
*Water pollution, Water quality, Reviews
Water pollution control,
*State-of-the-art assess'
ment, On-going research,
*Equipment evaluation .
13B
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (ThisReport)'
Unclassified
21. NO. OF PAGES
436
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
424
GOVERNMENT PRINTING OFFICE: 1975-657-695/5342 REGION NO. 5-II
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