EPA-650/2-74-067
Hoy 1974
Environmental Protection Technology Series
DESIGN, DEVELOPMENT, AND FABRICATION
OF A PROTOTYPE HIGH-VOLUME
PARTICULATE MASS SAMPLING TRAIN
Of o p m e n t
US Agency
Washington, ' -60
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EfA-650/2-74-067
DESIGN, DEVELOPMENT, AND FABRICATION
OF A PROTOTYPE HIGH-VOLUME
PARTICULATE MASS SAMPLING TRAIN
by
W.F. Lapson and H.J. Dehne
Aerotherm/Acurex Corporation
485 Clyde Avenue
Mountain View, California 94042
Contract No. 68-02-1339
Program Element No. 1AB012
ROAPNo. 21 AD J-080
EPA Project Officer: D.B.Harris
Control Systems Laboratory
National Environmental Research Center
Research Triangle Park, North Carolina 27711
Prepared for
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D . C. 20460
May 1974
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This report has been reviewed by the Environmental Protection Agency
and approved for publication. Approval does not signify that the
contents necessarily reflect the views and policies of the Agency,
nor does mention of trade names or commercial products constitute
endorsement or recommendation for use.
11
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ACKNOWLEDGEMENTS
The project described in this report was conducted for the Environmental
Protection Agency, Control Systems Laboratory, Research Triangle Park, North
Carolina, under Contract 68-02-1339. The project was initiated by Mr. James
A- Dorsey, Chief of Process Measurements Section, with Mr. Bruce Harris as
Project Officer. The technical guidance of Mssrs. Dorsey and Harris is grate-
fully acknowledged.
The principal individuals involved at Aerotherm were Dr. W. F. Lapson,
Project Manager, Mr. Hans-Joachim Dehne, Project Engineer, and Mr. Richard Beer,
Designer. Appreciation is also acknowledged for those who participated in the
conception of the project; Mr. Ken Lambson, Mr. Nick Davis, and Dr. Larry Anderson
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TABLE OF CONTENTS
Section Page
1 INTRODUCTION 1-1
2 REVIEW OF THE DEVELOPMENT OF A PROTOTYPE HIGH-VOLUME
PARTICULATE MASS SAMPLING TRAIN 2-1
2.1 Control Unit 2-1
2.2 Oven 2-8
2.3 Probe 2-8
2.4 Impinger Train 2-14
2.5 Vacuum Pump 2-16
2.6 Umbilical Line 2-21
2.7 Traversing Stand 2-21
2.8 Comparison of Actual Sampling System to
Design Objectives 2-21
3 RECOMMENDATIONS FOR FUTURE WORK 3-1
APPENDIX A A-l
TECHNICAL DATA REPORT T-l
iii
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LIST OF FIGURES
Figure Page
2-1 High Volume Particulate Sampling Train 2-2
2-2 Control Unit 2-3
2-3 Control Unit, Back Cover Removed 2-6
2-4 Oven with Carrying Case 2-9
2-5 Oven with Cyclone Separator and Filter in
Position for Use 2-10
2-6 Details of Filter Housing and Cyclone Separator 2-11
2-7 Probe Mounting for Vertical or Horizontal Traverses 2-12
2-8 Rotation of Sampling Probe 2-13
2-9 Probe Details 2-15
2-10 Lexan Impingers with Combination Ice Bath/Carrying Case 2-17
2-11 Lexan Impinger Dimensions 2-18
2-12 Vacuum Pump Assembly 2-19
2-13 Traversing Stand Set Up for Horizontal or Vertical
Traverses 2-22
3-1 Automated Particulate Sampler 3-4
IV
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SECTION 1
INTRODUCTION
Currently available particulate mass sampling systems typically sample at
rates less than 1 cfm. One consequence of this low sampling rate is an exces-
sively long sampling period during which plant operating conditions may vary
widely.
Another shortcoming of most sampling trains is that the temperature of
the probe and filter oven is usually less than 300°F. This permits condensation
of such vapors as sulfur trioxide which interferes with the determination of par-
ticulate concentration.
The Control Systems Laboratory of the EPA has been using a high volume
(approximately 7 cfm) version of a Federal Register, Method 5 particulate sam-
pling train for several years. This sampling train was bulky, difficult to
transport, and in many respects lacked the refinement of a commercial product.
The Control Systems Laboratory therefore sponsored a program for the development
of a high volume sampling train having the following features:
• Sampling rate of 5-10 cfm
• Modular assembly
• Portability
• Probe and oven temperatures up to 500°F
• Conformance to basic requirements of Method 5, Standards of Performance
for New Stationary Sources, Federal Register (December 23, 1971) , Vol-
ume 36, No. 247.
Aerotherm has delivered two high volume sampler trains to the EPA satisfy-
ing the above requirements. The new samplers are not much larger than the common
samplers operating at 1 cfm.
One of the objectives of this program was to study the overall requirements
of stack sampling instrumentation. The study concludes with recommendations for
sampling systems which are more portable, easier to use, and effective over a wide
range of sampling rates. It appears that the greatest advance in sampling trains
will result from automation based on the use of a small, dedicated digital compu-
ter. The flowrate adjustments for isokinetic conditions would be established by
this computer. In an automated system, all of the parameters important to the
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stack sampling procedure would exist as electrical signals and therefore can be
recorded easily. By relying on electronic rather than mechanical instrumentation,
many bulky components can be eliminated, thus resulting in a lighter system. One
of the most important advantages of the automated sampler would be its capability
for rapidly adjusting to changes in stack velocity or temperature. This is
especially important when sampling at high flowrates.
1-2
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SECTION 2
REVIEW OF THE DEVELOPMENT OF A PROTOTYPE HIGH-VOLUME
PARTICULATE MASS SAMPLING TRAIN
The high volume sampling train delivered to the EPA samples at nearly ten
times the rate of ordinary sampling systems while remaining nearly as compact
(Figure 2-1), The system is very rugged. The principal features are summarized
below:
• Sampling rates up to 6 cfm
• Oven and probe temperatures up to 500°F
• System breaks down into easily carried modules
• Fiberglass, cushioned cases for carrying and shipment of each piece
of equipment
• Oil-less vane pump modified for low leakage
• Two Magnehelic gages for accurate readout over the pitot tube range
of 0-4 inches of water
• Round probe body for ease in sealing the sampling port
• Probe can be rotated for sampling horizontal ducts located at same
level or below the sampling train
• Impinger train and ice bath separable from oven
• All glassware eliminated to avoid breakage problems - stainless steel,
Lexan, or teflon are used instead of glass
• Enlarged impinger bottles with demisters to prevent water carry-over
at flowrates up to 8 cfm
• Stable uni-rail traversing stand for guiding probe in horizontal or
vertical directions
• Circuit breakers instead of fuses
• Separate power lines for heaters and pump to assure obtainability
of required power.
In the following discussion, the sampling train will be described in
greater detail with comments regarding the basis of design decisions.
2.1 CONTROL UNIT
The control unit contains all of the instruments required for measuring
stack velocity, sampling flowrate and cumulative flow, and temperatures at var-
ious points in the sampling system (Figure 2-2). All of the controls for the
sampling system are located in the control unit with the exception of the valves
for controlling sample flowrate. The valves are mounted on the vacuum pump,
which is placed adjacent to the control unit when using the sampling system.
Thus all of the controls and measurement displays are centered about the control
unit.
Each of the items seen on the face of the control unit are described
below.
2-1
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I
•-
Figure 2-1. High Volume Particulate Sampling Train
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-
AEROTHERM
ACUREX Corporation
Figure 2-2. Control Unit
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Switches
There are five electrical switches with the following functions:
• Main power (with pilot light and circuit breaker)
• Probe heater (with pilot light and circuit breaker)
• Oven heater (with pilot light and circuit breaker)
• Fan power
• Elapsed time indicator start/stop switch
Circuit breakers have been used instead of fuses to avoid the problem of
running short of fuses. The oven circulation fan has been connected so that dur-
ing heating the fan is in operation regardless of the position of the fan control
switch. When the oven heater is "off", the fan may be turned "on" with the oven
door open to hasten cooling of the oven, cyclone, and filter.
Ej.apsed Time Indicator
An elapsed time indicator is used to determine when to move from one
traverse point to the next. The indicator has a resolution of one-hundredth
of a minute. The indicator can be re-set to zero, and started or stopped with
pushbuttons located near the indicator.
Oven and Probe Heater Temperature Controls
Power to the oven and probe heating elements is modulated with adjustable
temperature controllers. These controllers use thermocouples for temperature
sensing. Each controller has the following features:
• Actual temperature continuously displayed
• Maximum set-point is limited to 500°F by a mechanical stop
• Power "on" or "off" is indicated by red and green lights.
Some sampling trains use oven and probe heater controls located at the
oven. Frequently these controls are only simple adjustments to the input power
and do not involve any thermostatic control. The oven and probe heater controls
were located on the control unit because under some conditions the oven is
inaccessible for adjustment. This occurs while sampling large stacks when the
oven may be located beyond the edge of the sampling platform. Feedback control
of the temperature is used because the ambient conditions under which stack sam-
pling is performed are highly variable. The concern for accurate temperature
control is based on the fact that many of the effluents sampled have condensible
components. These components, e.g., water and sulfur trioxide, must be maintain!
as vapor prior to filtering out the particulates.
2-4
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The actual switching of power to the heating elements in the probe and
oven is done by heavy duty relays (lower right corner, Figure 2-3). This
greatly increases the capacity for the system to use longer probes or hotter
ovens, both requiring greater power.
Temperature Display
A digital temperature indicator is used together with an eight-point
selector switch. The selector switch permits monitoring the temperature by
means of thermocouples at each of the following locations:
• Stack
• Probe
• Oven
• Impinger train outlet
• Gas meter outlet
• Gas meter inlet
• Two "spare" locations.
The temperature range is 0° to 2000°F with an accuracy of ± 4°F.
Gas Flow
The cumulative sample gas flow is measured by a Rockwell Model 415 gas
meter. This is a high accuracy meter used for testing purposes. The measure-
ment is displayed by a digital counter and pointer with a resolution of 0.005 ft3.
Pressure Gages
Three Magnehelic pressure gages can be seen on the face of the control
unit. One is used for monitoring the pressure drop across the orifice meter
(see discussion on orifice meter below). The other two gages are connected
in parallel and indicate the pressure differential of the pitot tube used for
measuring stack velocity. One of the gages has a range from 0 to 0.5 inches of
water, the other, 0 to 4 inches of water. Thus the pitot tube pressure differ-
ential can be determined with high accuracy over the full range of 0 to 4 inches
of water.
Instead of Magnehelic gages, inclined/vertical manometers were con-
sidered. This type of manometer has increased resolution at low pressures,
the same as the two-gage system described above. Manometers are often used as
a primary standard and the readings obtained with them are usually trustworthy in
2-5
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!
r.
Figure 2-3. Control Unit, Back Cover Removed
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contrast to gages which require calibration. However, manometers contain liquid
which could spill during shipment or handling of the control unit, or inadver-
tently be blown into the pressure sampling lines. For these reasons Magnehelic
gages were used.
Umbilical Line Connections
The umbilical line between the control unit, oven, and probe makes the
following connections with the control unit:
• Multi-point connector with a.c. power leads to oven, fan, and
probe;
• Five dual-pin thermocouple connectors for the stack, probe, oven,
and impinger thermocouples;
• Two Swagelok connectors for the pitot tube.
The umbilical line also connects to the vacuum pump. The outlet of the
pump is connected to the "inlet" fitting located on the Control Unit. The sample
gas then passes through the gas and orifice meter in the manner of the typical
Method 5 sampling train.
A quick-disconnect fitting is provided at the sample "exhaust" outlet.
A length of tubing can be connected at this point for leading noxious sample
gases away from the control unit area.
Power Inlet Connectors
Two power connectors are shown. One provides the power for operating
all equipment located in the control unit and the fan. The other connector pro-
vides power for the probe and oven heaters. The vacuum pump has a separate
power line and power switch.
The power lines were divided in this fashion to assure that the system
could be connected to several separately fused lines to obtain the necessary
three kilowatts of power.
The control unit has a removable back cover. This feature provides ease
of access for assembly or repairs, and for setting the orifice size on the three-
position orifice meter (right side, Figure 2-3). Three orifices are used for
high accuracy measurements over the following flow ranges:
• 0.5-1.9 cfm
• 1.4-4 cfm
• 2.2-6 cfm
2-7
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The pressure drop for each of the above ranges is typically 0.5 to 4 inches of
water at the specified flow rates.
2.2 OVEN
The oven contains the cyclone and filter and supports the probe and im-
pinger train (Figures 2-1, 2-4, 2-5, 2-6). It is a sturdy, double-walled box
with two inches of fiberglass insulation. When the oven interior is at 500°F,
the exterior is safe to touch.
The maximum power dissipation of the single sheathed heating element is
1200 watts. This is sufficient to bring the oven up to 500°F in less than fifteef
minutes. A circulation fan increases the heat transfer rate to the cyclone sep-
arator and filter so that these too are heated within the fifteen minute warm-up
period. The fan can also hasten cooldown when the heater is off and oven door
is left open.
A cyclone separator is used when the sample stream contains particles
larger than 3.5 microns in diameter. The filter attaches to the cyclone or di-
rectly to the end of the sampling probe in the event the cyclone is not used.
Both the filter and cyclone are constructed of stainless steel. The interior
of the filter housing is coated with teflon to prevent the filter from sticking
to the housing. The filter has a standard 142 mm diameter which can be purchased
ready-cut from several filter manufacturers.
While the oven can easily be heated to 500°F, it is intended that the max'
imum temperature be limited to 450°F. This is to assure a long life for the
silicone rubber gaskets on the door jamb.
A rack is provided beneath the installed filter for placing a second fil-
ter. The second filter is thus preheated and ready for quick replacement of the
first filter if the latter becomes excessively clogged.
2.3 PROBE
The probe can be mounted on the oven in any of the following configura-
tions:
• Probe body horizontal (usual position)
• Probe body vertical (Figure 2-7)
• Probe tip assembly rotatable through 360° (Figure 2-8)
With this flexibility in probe orientation, nearly any sampling situation can
be accommodated.
2-8
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-
-
I
Figure 2-4. Oven with Carrying Case
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Figure 2-5. Oven with Cyclone Separator and Filter in
Position for Use
2-10
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Figure 2-6. Details of Filter Housing and Cyclone Separator
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HORIZONTAL
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Figure 2-7. Probe Mounting for Vertical or Horizontal Traverses
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THROUGH
Figure 2-8. Rotation of Sampling Probe
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The principal probe details (Figure 2-9) are as follows:
• Stainless steel sampling tube
• Fiberglass insulated strip heater
• Round probe body
• Strain relief for all electrical, thermocouple, and pitot line con-
nections
• Interchangeable probe tips with diameters from 1/4 to 3/4 inch.
The round probe body is an important feature not usually found on sam-
pling equipment. Because the body is round, the sampling port can be sealed
very easily. A good seal is necessary as part of proper sampling practice and
for the safety of nearby personnel.
2.4 IMPINGER TRAIN
The impinger train has several functions listed below in order of impor-
tance:
• Cooling the sampled gas to a temperature level safe for the pump
and gas meter
• Condensing for the purpose of determining water concentration
• Collection of particulates too fine to be trapped by the filter
• Chemical analysis
The above ranking is not arbitrary. Cooling the sampled gas stream is
an essential feature of the impinger train. Moisture concentration must be de-
termined as part of Method 5. The impinger train method is a convenient way
for determining moisture concentration. The use of impingers for the collec-
tion of very fine particles is presently being argued. Some specialists claim
that fine particulates may be formed as chemical precipitates or by condensation
in the impinger liquid. Thus the fine particulates collected may not actually
be present in the gas stream being sampled.
Chemical analysis by means of impingers has been ranked last because
chemical analysis is not always performed concurrently with particulate sampling.
The impinger method is useful, however, when searching for trace metals and a
wide variety of other chemical compounds. In this case, however, the virtues
of isokinetic sampling at high flowrate are not important and a smaller impinger
train for the exclusive purpose of chemical analysis is more useful.
2-14
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to
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PROBS TEMP
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HEATER POVMEE
Figure 2-9. Probe Details
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The familiar all-glass Smith-Greenberg impingers could not be used above
3/4 cfm because of water carry-over. The glass parts were also too fragile
for the rough environment in which stack sampling is performed. The impingers
were therefore increased in size, demisters added, and the glass parts were
replaced by Lexan plastic or stainless steel parts (Figures 2-10, 2-11). The
impingers can be used at flowrates up to 8 cfm.
The interconnections between the impingers are made with stainless steel
tubing and Swagelok fittings. This is a rugged, neat method for connecting
the impingers as compared to glass tubing and ground-glass spherical joints
with clamps.
The impingers are sealed with large diameter caps using "0" rings. Thus
the interior of the impinger is completely accessible for flushing or cleaning.
The "0" rings make better joints than the more common ground glass joint used
on impingers. The "O" rings do not require a layer of grease for sealing and
they do not seize as ground glass joints can.
The Lexan plastic is inert to most commonly encountered gases and sol-
vents. In the rare case when Lexan can't be used, the simple cylindrical shape
can be produced in glass or teflon.
Other features of the impinger train are the following:
• Impinger rack constructed of PVC plastic
• Thermocouple mounted on cap of last bottle for monitoring outgoing
gas temperature
• Stainless steel cap on first impinger to withstand high temperature
gas
• Fiberglass carrying case also serves as ice bath
• Carrying case accommodates impingers, rack, and a 25-foot umbilical
line
• Impinger train is separable from the oven.
The feature of being able to separate the impinger train from the oven is useful
.*
because not all sampling situations involve high temperature gas streams.
2.5 VACUUM PUMP
A vane-type vacuum pump, Gast Model 1022, is used. This pump has a 3/4
h.p. motor, flowrate of 10 cfm at 0 in. Hg, and weighs 59 Ibs. including all
fittings (Figure 2-12). The features of this pump are as follows:
• Smooth, pulse-free flow
• High vacuum capacity
2-16
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H
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Figure 2-10. Lexan Impingers with Combination Ice Bath/Carrying Case
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L^B •«•• >«MW W^^ MM
Figure 2-11. Lexan Impinger Dimensions
2-18
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SJ
-
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Figure 2-12. Vacuum Pump Assembly
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• Self-lubricating carbon vanes
• Special shaft seal
• Coarse and fine flow control valves located on pump
• Carrying handle
• Operates in open air for good cooling
• Unbreakable metal filter and muffler jars
• Vacuum gage to indicate filter condition
• Quick disconnect fittings*
The pump is relatively heavy compared to the lifting capacity of an in-
dividual. However, the pump is quite compact and the carrying handle makes its
weight manageable. We explored ways for lightening the vaccum pump/ including
the following:
• Use diaphragm pump
• Have special pump head fabricated from a lightweight alloy
• Use smaller pump operated at higher rpm
• Substitute a high performance induction or universal motor for the
standard motor.
A Thomas Model 2727BA39 diaphragm type vacuum pump was evaluated. This pump
has two diaphragms, a flowrate of 7 cfm at 0 in. Hg, and weighs 27 pounds. The
low weight, as compared to a vane pump, is mostly the result of using lightweight
die castings for the pump head.
The diaphragm pump was not satisfactory because of its pulsating flow.
It is possible that a surge tank could have been used to reduce the magnitude
of the pulsations. However, the additional weight of a surge tank would negate
the advantage of low weight in the pump itself.
At one point the leak-free characteristic of the diaphragm pump was
considered a strong point. The seals on a vane pump were reworked, however, re-
sulting in a negligible leak rate.
The possibility of a special lightweight pump was also considered. This
was not a practical approach because the pump manufacturer (Cast, Inc.) had no
interest in producing small quantities, i.e., less than 1,000 units, of a special
pump. The same response resulted when we asked for a corrosion-resistant stain-
less steel pump.
The last two possibilities for reducing pump weight remain practical.
As much as 15 Ibs. could be saved by operating a small pump at high rpm using
2-20
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a high performance induction motor. However, the cost of developing a lightweight
Pump/motor combination was not justifiable on this program.
One of the major reasons for using a vane pump rather than diaphragm pump
18 *-ne better flow/weight ratio at high vacuum for the vane pump. Above 7 in.
9» the vane type pump actually weighs less than a diaphragm pump of the same
flow capacity.
2.6
UMBILICAL LINE
The umbilical line provides all power, thermocouple, and pneumatic con-
nections between the probe, oven, and impingers and the Control Unit (Figure 2-1)
ne significant features of this part are as follows:
• Quick disconnects and plugs at each end
• Strain reliefs to prevent inadvertent opening of connections or
wearing of lines
• Smooth, kink-free, waterproof sheath for enclosing all lines
• Mating ends of connectors configured so that umbilical line length
may be increased by plugging in additional line.
The basic umbilical line has a length of 25 feet.
2'7 TRAVERSING STAND
The oven with probe attached is supported from a roller-carriage running
°n a track in the traversing stand (Figure 2-1). Thus the probe can easily be
9Ulded across the stack being sampled.
The stand can be erected in two configurations, one for horizontal probe
traverses, the other for vertical traverses (Figure 2-13). The height of the
stand is adjustable over a distance of 7 feet for horizontal traverses. The
and breaks down into pieces for convenience in shipping.
2 R
•° COMPARISON OF ACTUAL SAMPLING SYSTEM TO DESIGN OBJECTIVES
The design objectives were to construct a Method 5 type of sampling train
aving a flow capacity of 5-10 cfm, portability, ruggedness to resist the rigors
shipment, and ease of set-up and handling. The oven and probe were to be
eatable to 500°F. The system was to break down into modules weighing no more
th*n 50 ibs.
The sampling train actually constructed samples at a maximum rate of
°ut 6 cfm, limited by the vacuum pump capacity. With a larger vacuum pump,
2-21
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ne capacity can be increased to 8 cfm when the flow is limited by water carry-
Ver in the impinger train. The oven and probe may be heated to 500°F, although
°r long life of the oven door gaskets, 450°F is a better limit. The heaviest
in the system are the control unit, 66 Ibs., and the pump, 59 Ibs. While
modules are heavier than desired, they are quite manageable because of the
handles provided.
Rugged shipping cases are provided for all parts of the system: high
^pact strength fiberglass for the control unit, oven, impinger train, and vac-
Um Pump; steel reinforced plywood for the probe and traversing stand.
The entire system can be unpacked and set up for use in less than one
°Ur- Heating time for the probe and oven is less than 15 minutes.
2-23
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SECTION 3
RECOMMENDATIONS FOR FUTURE WORK
The two most useful objectives for future work are weight reduction and
simplification of operation. To illustrate, the present high volume sampling
system has a weight of 300 Ibs. including 90 Ibs. of shipping containers. The
valve adjustments and computations for establishing isokinetic sampling condi-
tions are repetitive, tedious, and require the abilities of a skilled technician
Fortunately, weight reduction and simplification of operation are complementary
objectives.
One of the main contributions to the weight of a stack sampling system is
the meter used for measuring total sample flow. A 6 cfm sampler, for example,
requires a bulky meter weighing about 20 Ibs. The reason for using this type
of meter is that it is simple and inexpensive. If the instrumentation is changed
so that an electrical signal corresponding to flow rate is produced, then elec-
tronic flow integration becomes possible. The gas meter is thus replaceable by
an electronics module weighing a few ounces. There are further advantages, how-
ever. The sampling system can now be made to automatically maintain isokinetic
sampling conditions. Since all parameters are available as electrical signals,
e.g. stack temperature, velocity, sampling rate..., it is feasible to automate
the recording of data also. (See Table 3-1 for comparison of manual and auto-
mated sampling systems.)
The concept for an advanced, automated particulate sampler would not have
been very practical two years ago. It was about then that small, versatile
computers for process control and low-cost digital displays began to appear on
the marketplace.
A sampler based on a digital computer would have these capabilities:
• Continuous, automatic control of sampling rate
• Compensation for stack temperature variations
• Control of probe and oven heaters
• Continuous digital display of all important test parameters
• Data logging on magnetic tape cassette
• Data logging on digital printer
3-1
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TABLE 3-1
SUMMARY OF SAMPLING SYSTEM CONCEPTS
System Type
Description
Estimated Cost*
Dollars
Manual
Data taking and adjustment for isokinetic sam-
pling entirely manual. System is heavy, re-
quires skilled operator. Because of simplicity
easy to comprehend its use and maintenance re-
quirements. Currently most common type of
sampling system.
2,500-6,000
Semi-automatic
Adjustment for isokinetic sampling automatic, but
manual data taking. Simplifies operation of
sampler, reduces skill level required of oper-
ator and chances for error. Isokinetic con-
ditions and flow regulation determined by
simple analog or digital computer. Electronic
flow Integration. System bulk and weight re-
duced to half that of manual system. Adaptable
to continuous monitoring applications.
4,000-12,000
Automatic
Adjustment for isokinetic sampling and data
taking are automatic. Data recorded on tape
cassette for rapid data reduction. Cassette
interface with computer for data print-out,
calculations, or curve plotting, e.g. temper-
ature and velocity profiles. Lightweight
system requiring minimum of skill to operate.
Adaptable to continuous monitoring applications,
6,000-14,000
Automatic
Sampling and
Probe
Traversing
All the features of the automatic sampler with
the additional advantage of automatic probe
positioning. A single operator can monitor
several units simultaneously. Adaptable to
continuous monitoring of large stacks.
7,000-15,000
n9 small quantity production, e.g. 10 units
3-2
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Some of the features of the automated sampling system are considered
below (Figure 3-1). First, it should be noted that the operator must initially
supply some basic data to the computer, e.g., stack pressure, molecular weight
of the sampled gas, and the desired probe and oven operating temperatures. The
operator must also select the appropriate sampling nozzle diameter.
The sample flowrate is measured with a turbine flowmeter. This type of
flowmeter is usable over a flow range of at least 10:1, has a digital signal
corresponding to volumetric flowrate, and is nearly insensitive to gas viscosity.
The flowmeter is placed in the oven, together with the cyclone, filter, and
motorized control valve. Thus none of these components are affected by con-
densation of water or other vapors.
A gas-to-air heat exchanger would be used instead of an impinger train
for cooling the sample gas. This would eliminate the need for ice and result
in a lighter weight cooling system than the impinger train.
The vacuum pump is located downstream from the turbine flowmeter. With
this positioning of components, the leakage characteristics of the pump are not
critical, assuming the pump can handle the required flowrate and vacuum. Because
the leakage characteristics of the pump are not critical, there is an opportunity
to reduce the transported weight of the system in a novel way. The pump can be
purchased as a piece of plant equipment and left permanently on site.
All of the important test variables are displayed digitally. The operator
can thus verify that all conditions are normal. The data can be automatically
recorded on a tape cassette. Using a cassette, the data can be fed into a
computer, perhaps over a telephone line, for the determination of velocity pro-
files and particulate concentrations. A digital printer could be used as a back-
up of a tape cassette data logger.
Probe traversing can also be done automatically since all that is required
is motion along a straight line. A signal indicating probe position would be
into the system for recording regardless of whether the probe is moved manually
or automatically.
The weight of an automated system would be about 140 Ibs., assuming the
vacuum pump and heavy vacuum line are left at the sampling site. The greatly
simplified operation will free the test personnel so that they can make subjec-
tive evaluations of sampling conditions, or conduct other measurements, e.g.r
chemical analyses.
3-3
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TUEBiNE
I
STACK.
PITOT PfZOSE
I
DIFFERENTIAL
PRESSURE TRAKJSPUCER
i PKOBE POSITION SIGNAL.
STACK
RELAY
OVEN HEATER.
RELAY
t
MOLECULAR WEIGHT
STACK PRESSURE I
OVEN)
PROBE TEMP6RATUBC
CC-MTKOL.
SllSNJAl-
DIGITAL.
DATA
OUTPUT
MANUAL DATA
INPUT SWITCHES
VACUUM
PUMP
TIMS
STACK, TEMPE|?ATUee
STACK VELOCITY
SAMPLING RATE
TOTAL SAMPLE FLOW
OVEN
PROBe
1 DIGITAL j
I PRINTER I
I I
A- 837 6
Figure 3-1. Automated Particulate Sampler
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An automated, portable particulate sampling system would undoubtedly be
useful. A system of this type would have even greater usefulness for continuous
monitoring applications where the system is permanently installed on the stack.
3-5
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APPENDIX A
INSTRUMENTATION FOR STACK SAMPLING
Isokinetic stack sampling with an EPA type of sampling system requires the
following measurements:
• Stack temperature
• Temperature at orifice meter
• Stack pressure
• Sample flowrate and cumulative flow
• Stack velocity
• Humidity
The various ways for performing these measurements are indicated in Tables
1~4.
In the future, stack sampling can be expected to become more automated and
The measurement methods suitable for the current EPA sampling train will
ot necessarily be appropriate for the more advanced equipment. For example, it
8 currently feasible to measure temperatures with glass-stem or bi-metallic ther-
°toeters. it is more convenient, however, to measure temperature with thermocouples.
temperatures of concern can then be displayed at a single location, sensor place-
is Simple in the case of thermocouples, and the temperature is observable as a
°ltage suitable for recording or as a control signal.
The measurement of flowrate and total flow is another area where improve-
ent is needed. The orifice meters used for measuring flowrate are accurate only
QVev
a narrow range of flow conditions. Three separate orifices are necessary,
r example. to cover the 0-6 cfm range of the Aerotherm high volume stack sampler.
ML.
"etter way to measure flowrate is with a turbine flowmeter. A single turbine
n cover a 10:1 flow range easily. The electrical signal produced by the turbine
°wmeter is useful as the input to a controller which automatically maintains
kinetic sampling conditions. The flowmeter signal can also be" integrated elec-
°nically, thus eliminating the requirement for a heavy, bulky gas meter.
Stack velocity is usually observed with Magnehelic gages or inclined/verti-
i manometers. The pitot differential pressure displayed by these instruments is
^ectly related to the stack velocity. A direct indication of stack velocity
1(3 be useful. This can be obtained by measuring differential pressure with a
Ure transducer. The pressure signal would then be processed along with stack
rature in an analog or digital computer having stack velocity for the output.
A-l
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Table 1. Measurement of Temperature
Measuring Device
Glass-stem thermometers
Mercurv-fllass
thermometer
Atcohol-gtass
thermometer
Pcntane-glass
thermometer
Jena or quartz mercury-
nitrogen thermometers
Gas thermometers
Resistance thermometers
Platinum-resistance
thermometer
Nickel-resistance
thermometer
Thermistors
Thermocouples
Pl-Pt-Rh thermocouple
Chromel-alumel thermo-
couple
Iron-constantan
thermocouple
Cofiper-constantan
thermocouple
Chromcl-constaotan
thermocouple
Beckman thermometers
(Metastatic)
Bimetallic thermometers
Pressure-bulb thermometers
Gas-filled bulb
Vapor-filled bulb
Liquid-filled bulb
Application
Temperature of gases and
liquids by contact
Primary Standard
Precision; remote read-
ings; temperature of
fluids or solids by contact
Remote readings;
temperature by contact
Standard for thermo-
couples
General testing of high
temperature; remote rapid
readings by direct contact
I!
1!
Same as above, especially
suited for low temperature
For differential
temperature in same
applications as in glass
stem thermometer
For approximate
temperature
Remote-testing
I
II
Range, ° F Precision. ° F Limitations
—38/575 Less than 0.1 In gases, accuracy affected
to 10
-100/100
-200/70
-38/1.000
by radiation
-459/1.600 Less than 0.01 Requires considerable skill to us*
-320/ 1 ,800 Less than 0.2 High cost; accuracy affected
to 5 by radiation in gases
-150/300 0.3
Up to 600 0.1
Accuracy affected by
radiation in gases
500/3,000 0.1 to 5 High cost: also, requires
Up to 2,200 0.1 to
Up to 1.500 0.1 to
Up to 700 0.1 to
expensive measuring device
15 Less accurate than above
15 'Subject to oxidation
15
5°C difference 0.01'C Must be set for temperature
to be measured
0/1,000 1 usually much Time lag; unsuitable for remote
more use; unreliable
-200/1,000 2
20/500 2
-50/2,100 2
taut-on must be exercised s°
that installation is correct
Optical pyrometers
Radiation pyrometers
Seger cones (fusion
pyrometers)
Indicating crayons
Melting and boiling
points of materials
For intensity of narrow
spectral band of high
temperature radiation
(remote)
For intensiry of total
high-temperature
radiation (remote)
1,500 upward
Any range
15
Approximate tern perature 1.000/3,600
(within temperature source)
Approximate temperature
(on surface)
Standards
125/900
All except ex-
tremely high
temperature
50
±1%
Extremely precise For laboratory use only
A-2
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Table 2. Measurement of Absolute Pressure
Measuring Device
McLeod gauge
f Irani gauge
Thermocouple vacuum gauge
Absolute-pressure manometer
Diaphragm gauge
Barometer, mercury-
nianometer type
Differential manometer and
barometer
Evaporation liquid temperature
Pressure transducers - strain
Oage. capacity, potentiometer.
crystal, magnet, and others '
Application Range
Very low absolute. 0-0.1 in. Hg
pressure
Moderately low absolute 0-30 in. Hg
pressure or above
0.1-20 mm Hg
Atmospheric pressure
Moderately low absolute 0-450 in. Hg
pressure .or above
On refrigeration machine Depends on
and for use during liquid
evacuation
Remote reading, responds 0.05 to 50.000
to rapid changes of pressure psi
Precision Limitations
2-5% Not direct reading; vapors
tend to condense out
Must be calibrated for gas
composition on which used
0.01 in. Not readily portable
0.05 mm Hg Direct reading
0.001-0.01 in. Not readily portable
0.01 in. Awkward observation; requires
two readings
1% Liquid must be kept supplied; can
be used only where liquid evap-
oration will not damage system
0.1%
Table 3. Measurement of Differential Pressures
Measuring Device
Micromanometer
Draft gauges
Manometer
Swinging-vane type gauge
Bourdon-tube type
Pressure transducers -
Strain gauge, capacity.
Application Rang*
Very low pressure 0-6 in. H,O
differential
Moderately low pressure 0-10in. H,O
differential
Medium pressure 0-100 in. H,O
differential or Hg
Moderately low pressure 0-0.5 in. H,O
differential O-20 in. H,O
Medium to high pressure Any
differential usually to
atmosphere
Remote reading, responds 0.05 to 50,000
to rapid changes of psi
Precision Limitations
0.0005 in. H3O Not readily portable; not easy to
use with pulsating pressure
0.005 in.- Must be leveled carefully
0.05 in. H,O
0.05 in. Where used with liquid must be
compensated for liquid density
5% Generally usable to atmospheric
pressure only
As high as 0.01 Subject to damage due to over-
psi or 0.01 % of pressure shock or pulsation
full scale
0.1%
tIOmeter, crystal, magnet pressure
A-3
-------
Table 4. Measurement of Humidity
Measuring Device
Application
Range
Precision
Limitations
Wet-bulb thermometer with
dry-bulb thermometer
(Psychrometer)
Dew-point apparatus
Condensation type
Fog type
Electrical conductivity
type
Hygrometer (for relative
humidity)
Hair hygrometer
Hygroscopic material
other than hair
Electrical conductivity
Infra-red Radiation
Standard salt
Chemical analysis
Absorption and weighing
Room of building, out-
side air, air moving in
ducts: standard method
0 to 500
0.1 to 1
Occasional laboratory
work; not widely used
-180 to 200
Simple wide range method —100 to -I- 100
Accurate measurement of 0-200
dew point; suitable for
remote use
2
1
For direct relative
humidity (rh) in air
where motion is slight
Same as above — also for
high sensitivity
For remote use
While usable at all
temperatures, it is
uniquely applicable to
extremely low temperatures
For standards
0 to 100% rh-
-40 to 150F
3%rh
Oto100%rh
-40 to 150 F
2 to 5% rh
Should be used in air stream
moving 1,000 to 1,500 fpm or
correction m*de. Thermocouple
may be used at lower velocities.
Difficult to use at sub-freezing
temperature.
Cumbersome, expensive, difficult
to use with precision; unsuitable
for remote use
Series of readings necessary for
determination
Unusable below —20° F
and below 15% rh or for any
moderate humidity at temperature
under 0° F
Considerable lag; low sensitiv-
ity; adversely affected by
temperature above 125DF and
rh below 20%; frequent
calibration required when used
•t extremes of range
Frequent calibration required
when used at extremes of range.
Requires frequent calibration
Requires the use of very costly
equipment
Cumbersome process
Note: Tables 1 - 4 are from the article "Significance of Errors in Stack
Sampling Measurements" by R. T. Shigehara, W. S. Todd, and W. S.
Smith.
A-4
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.,
EPA-650/2-74-067
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Design, Development, and Fabrication of a Prototype
High-Volume Particulate Mass Sampling Train
6. REPORT DATE
May 1974
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
W. F. Lapson and H. J. Dehne
8. PERFORMING ORGANIZATION REPORT NO
7079
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Aerotherm/Acurex Corporation
485 Clyde Avenue
Mountain View, CA 94042
10. PROGRAM ELEMENT NO.
1AB012; ROAP 21ADJ-080
11. CONTRACT/GRANT NO.
68-02-1339
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research .and Development
NERC-RTP, Control Systems Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final: 6/26/73 - 4/30/74
14. SPONSORING AGENCY CODE
18. SUPPLEMENTARY NOTES
16. ABSTRACT
The report gives results of a program to develop a high-volume sampling train with
the following characteristics: 5-10 cfm sampling rate, modular, portable, 500 F
probe/oven temperature, and conforming to Federal Register Method 5 basic
requirements (standards of performance for new stationary sources). The program
included a study of the overall requirements of stack sampling instrumentation,
concluding with recommendations for portable, easier to use systems that are
effective over a wide range of sampling rates.
i.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Chemical Analysis
Air Pollution
Sampling
Particles
Flue Gases
Measuring Instruments
^article Density (Concentration)
Stationary Sources
Particulates
Mass Sampling
13B, 07D
14B
21B
8. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
40
20. SECURITY CLASS (TMspage)
Unclassified
22. PRICE
> Form 2220-1 (9-73)
T-l
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