&ER&
United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
EPA-460-2-78-042C
October 1978
Air
Stack Sampling
Technical Information
A Collection of
Monographs and Papers
Volume
-------
ISO/2-78-042c
Stack Sampling Technical Information
A Collection of Monographs and Papers
Volume
Emission Standards and Engineering Division
U S ENVIRONMENTAL PROTECTION AGENCY
Office of Air, Noise, and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
October 1978
-------
This report has been reviewed by the Emission Standards and Engineering
Division, Office of Air Quality Planning and Standards, Office of Air, Noise
and Radiation, Environmental Protection Agency, and approved for publica-
tion. Mention of company or product names does not constitute endorsement
by EPA. Copies are available free of charge to Federal employees, current
contractors and grantees, and non-profit organizations - as supplies permit
from the Library Services Office, MD-35, Environmental Protection Agency,
Research Triangle Park, NC 27711, or may be obtained, for a fee, from the
National Technical Information Service, 5285 Port Royal Road, Springfield,
VA 22161.
Publication No. EPA-450/2-78-042c
n
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PREFACE
The Clean Air Act of 1970 requires the Administrator of the
Environmental Protection Agency to establish national emission standards
for new stationary sources (Section 111) and hazardous air pollutants
(Section 112). The development of these emission standards required the
concurrent development of reference test methods and procedures. The
reference test methods and procedures are published in the Federal Register
along with the appropriate regulations.
From time to time, questions would surface concerning the methods and
procedures. In many cases, specific studies would be needed to provide
informed, objective answers. The papers and monographs resulting from these
studies were usually distributed to people involved in emission measurement;
a major method of distribution has been the Source Evaluation Society
Newsletter.
To provide a readily available resource for new and experienced personnel,
and to further promote standardized reference methods and procedures, it has
been decided to publish the papers and monographs in a single compendium.
The compendium consists of four volumes. The Table of Contents for all
four volumes is reproduced in each volume for ease of reference.
Congratulations and sincere appreciation to the people who did the
work and took the time to prepare the papers and monographs. For the most
part the work was done because of personal commitments to the development
of objective, standardized methodology, and a firm belief that attention
to the details of stack sampling makes for good data. The foresight of
Mr, Robert L. Ajax, the former Chief of the Emission Measurement Branch and
now the Assistant Director, Emission Standards and Engineering Division, in
providing the atmosphere and encouragement to perform the studies is
gratefully acknowledged. The skill and dedication of Mr. Roger Shigehara,
in providing personal supervision for most of the work, is commended.
Don R. Goodwin
Di rector
Emission Standards and
Engineering Division
m
-------
VOLUME I
TABLE OF CONTENTS
Method for Calculating Power Plant Emission Rate 1
by R. T. Shigehara, R. M. Neulicht, and W. S. Smith
Emission Correction Factor for Fossil Fuel-Fired Steam 10
Generators (COp Concentration Approach)
by R. M. Neulicht
Derivation of Equations for Calculating Power Plant Emission 20
Rates (02 Based Method - Wet and Dry Measurements)
by R. T. Shigehara and R. M. Neulicht
Summary of F Factor Methods for Determining Emissions from 29
Combustion Sources
by R. T. Shigehara, R. M. Neulicht, H. S. Smith,
and 3. W. Peeler
Validating Orsat Analysis Data from Fossil-Fuel-Fired Units 44
by R. T. Shigehara, R. M. Neulicht, and W. S. Smith
A Guideline for Evaluating Compliance Test Results 56
(Isokinetic Sampling Rate Criterion)
by R. T. Shigehara
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VOLUME II
TABLE OF CONTENTS
A Type-S PI tot Tube Calibration Study 1
by Robert F. Vollaro
The Effect of Aerodynamic Interference Between a Type-S 24
Pi tot Tube and Sampling Nozzle on the Value of the
Pi tot Tube Coefficient
by Robert F. Vollaro
The Effects of the Presence of a Probe Sheath on Type-S 30
Pi tot Tube Accuracy
by Robert F. Vollaro
An Evaluation of Single-Velocity Calibration Technique as 48
a Means of Determining Type-S Pi tot Tube Coefficients
by Robert F. Vollaro
Guidelines for Type-S Pitot Tube Calibration §3
by Robert F. Vollaro
The Effects of Impact Opening Misalignment on the Value of 89
the Type-S Pitot Tube Coefficient
by Robert F. Vollaro
Establishment of a Baseline Coefficient Value for Properly 95
Constructed Type-S Pitot Tubes
by Robert F. Vollaro
A Survey of Commercially Available Instrumentation for the 104
Measurement of Low-Range Gas Velocities
by Robert F. Vollaro
The Use of Type-S Pitot Tubes for the Measurement of Low 122
Velocities
by Robert F. Vollaro
VI
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VOLUME III
TABLE OF CONTENTS
Thermocouple Calibration Procedure Evaluation 1
by Kenneth Alexander
Procedure for Calibrating and Using Dry Gas Volume Meters 10
As Calibration Standards
by P. R. Westlin and R. T. Shigehara
Dry-Gas Volume Meter Calibrations 24
by Martin Wortman, Robert Vollaro, and Peter Westlin
Calibration of Dry Gas Meter at Low Flow Rates 33
by R. T. Sfiigehara and W. F, Roberts
Calibration of Probe Nozzle Diameter 41
by P. R. Westlin and R. T. Shigehara
Leak Tests for Flexible Bags 45
by F. C. Biddy and R. T. Shigehara
Adjustments in the EPA Nomograph for Different Pitot Tube 48
Coefficients and Dry Gas Molecular Weights
by R. T. Shigehara
Expansion of EPA Nomograph (Memo) 60
by R. T. Shigehara
EPA Nomograph Adjustments (Memo) 63
by R. T. Shigehara
Graphical Technique for Setting Proportional Sampling 65.
Flow Rates
by R. T. Shigehara
vii
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VOLUME IV
TABLE OF CONTENTS
Recommended Procedure for Sample Trayerses in Ducts Smaller 1
Than 12 Inches In Diameter
by Robert F. -Vollaro
Guidelines for Sampling in Tapered Stacks 24
by T. J. Logan and R. T. Shigehara
Considerations for Evaluating Equivalent Stack Sampling 28
Train Metering Systems
by R. T. Shigehara
Evaluation of Metering Systems for Gas-Sampling Trains 40
by M. A. Wortman and R. T. Shigehara
An Evaluation of the Current EPA Method 5 Filtration 49
Temperature-Control Procedure
by Robert F. Vollaro
Laboratory Evaluation of Silica Gel Collection Efficiency 67
Under Varying Temperature and Pressure Conditions
by Peter R. West!in and Fred C. Biddy
Spurious Acid Mist Results Caused by Peroxides in Isopropyl 79
Alcohol Solutions Used in EPA Test Method 8 (Memo)
by Dr. Joseph E. Knoll
Determination of Isopropanol Loss During Method 8 Simulation 80
Tests (Memo)
by Peter R. West!in
Comparison of Emission Results from In-Stack Filter Sampling 82
and EPA Method 5 Sampling
by Peter R. West!in and Robert L. Ajax
EPA Method 5 Sample Train Clean-Up Procedures gg
by Clyde E. Riley
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THERMOCOUPLE CALIBRATION PROCEDURE EVALUATION
Kenneth Alexander*
Introduction
The Federal test methods published in the August 18, 1977,
Federal Register require that thermocouple-potentiometer systems
be calibrated after each field use. Above 405°C» an NBS calibrated
reference thermocouple-potentiometer system or an alternative
reference, subject to the approval of the Administrator, is
specified for the comparison. Since the calibration procedure
requires the use of high temperatures in the laboratory and the
use of expensive reference thermocouples, a study was conducted
to determine whether extrapolated values from low-temperature
calibrations would provide sufficiently accurate values at the
high temperatures.
The purpose of this paper is to report the findings of the
study and to establish a simplified calibration procedure.
Equipment and Procedure
Six chrome!-alumel (type K) thermocouples and one potentiometer
with readout were selected for calibration. ASTM mercury-in-glass
reference thermometers and an NBS calibrated platinum-rhodium
(type S) thermocouple-potentiometer were used as the temperature
references.
*Emission Measurement Branch, ESED, OAQPS, EPA, Research Triangle
Park,
Published in Source Evaluation Society Newsletter 3(2), June 1978
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2
The following procedures were used in calibrating the thermo-
couples:
1. For the ice point (32°F) calibration, crushed ice and
liquid water were placed in a Dewar vessel to form a slush. The
thermocouples were placed in the slush to a depth of not less than
2 inches, and care was taken so that they did not touch the sides
of the vessel.
After a 3-minute wait for the system to reach thermal equi-
librium, the readout on the potentiometer was observed and recorded.
Eight readings were taken in 1-minute Intervals. When necessary,
ice was added and excess liquid drained off to maintain a temp-
erature of 32°F.
2. For the boiling point calibration a hot plate and a
Pyrex beaker filled with deionized water and several boiling chips
were used. After the water reached a full boil, the thermocouples
were placed in the water to a depth of no less than 4 inches and
the system was allowed to equilibrate for 3 minutes. Eight
potentiometer readings were obtained in successive 1-minute in-
tervals and recorded. Barometric pressure was also recorded
periodically. The temperature of the boiling water was measured
concurrently with a reference thermometer to obtain the correct
temperature of the water.
3. For higher temperature calibrations, a tube furnace and
ASTM reference thermometers (up to 760°F) or the NBS calibrated
platinum-rhodium reference thermocouple (above 760°F) were employed.
-------
3
The tube furnace had a heated cylindrical volume approximately
13 Inches In length and a 1-Inch I.D.; the volume at either end
was opened to the atmosphere.
The highest and most stable temperature was found to be
at the center of the oven volume. This 1s where the tip of the
reference device and the tip of the thermocouple were placed.
The test and reference thermocouples were Inserted Into the
furnace it least 4 Inches. The ASTM reference thermometers,
however, which were designed for full immersion, could not be
2
totally immersed In the furnace. A temperature correction
was made, therefore, for the length of the mercury shaft that
was exposed to the outside of the furnace.
To minimize temperature fluctuations, the furnace was
heated 50° to 100° above the desired calibration temperature
and then allowed to cool at a rate that the slower responding
device could accommodate. When it was clear that both devices
were responding to the temperature drop at the same steady rate,
temperature readings were recorded at 1-minute intervals until
eight readings were obtained. The average of all eight readings
was taken as the calibration temperature. Several high-temperature
calibrations were made in the range of 600° to 1600°F.
To determine whether the thermocouples lose any of their
accuracy or precision at low temperatures after repeated
exposure to high temperatures, three thermocouples were successive-
ly calibrated at the ice point, boiling point, and approximately
1600°F.
-------
4
D2Scussion_of_Resu1 ts
Results of all tests are summarized 1n Tables 1..2, and 3.
Table 1 lists the temperature observed. Table 2 shows the results
of constructing an extrapolated curve from only the 1ce point and
boiling point data found in Table 1 by using the least-squares
method. The final column in Table 2 shows the percent error be-
tween extrapolated and actual values to be always less than 1.1
percent. This 1s well within the specified accuracy of 1.5 percent
of the measured absolute temperature. Table 3 summarizes the tests
made to determine the retention of calibration by thermocouples
after repeated cycling between high and low temperatures. The
percent error between the observed and reference temperatures 1s
never more than 1 percent and rarely above 0.5 percent. Thus,
there seems to be no indication that any loss of precision or
accuracy occurs by cycling the thermocouples between temperature
extremes.
Recommended Procedure
The following procedure is recommended for calibrating thermo-
couples for field use:
1. For the 1ce point calibration, form a slush from crushed
ice and liquid water (preferably deionized, distilled) in an
insulated vessel such as a Dewar flask.
Taking care that they do not touch the sides of the flask,
insert the thermocouples into the slush to a depth of at least
2 Inches. Wait 1 minute to achieve thermal equilibrium, and
record the readout on the potentiometer. Obtain three readings
-------
Table 1: DATA SUMMARY OF THERMOCOUPLE CALIBRATION
I.D. NO.
10K.
Test
temperature, R
494
676
1113
1261
1664
Reference
temperature. °R
492 (32°F)
675 (215°F)
1108 (648°F)
1260 (800°F)
1658 (1196°F)
I.D. NO.
108
Test
temperature, R
493
674
1107
1304
1598
2012
Reference
temperature, °R
492
672
1104
1298 '
1590
2018
I.D
Test
temperature-?R
494
676
1295
1596
. NO.
02
Reference
temperature. °R
492
675
1292
1583
I.D. NO.
110
Test
temperature°R
493
674
1298
1628
2074
Reference
tempera ture,°R
492
672
1295
1618
2064
I.D.
1(
Test
temperature. °R
493
674 i
1118
1276
1537
"1969
I.D
1
Test
temperature, °R
493
' 674'
1293
1624
NO.
3
Reference
temperature, °R
492
.672
1114
1273
1537
1972
NO.
1
Reference
temperature, °R
492
672
1285
1609
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Table 2: TRUE REFERENCE TEMPERATURES VERSUS EXTRAPOLATED REFERENCE TEMPERATURE
t
I.D. NO.
101
101
102
102
103
103
103
108
108
108
no
no
no
in
m
Observed
temperature,
R
1261
1663
1295
1596
1276
1537
1969
1304
1598
2012
1298
1628
2074
1293
1624
Reference,
temperature,
°R
1260
1658
1292
1583
1273
1537
1972
1298
1590
2018
1291
1618
2064
1285
1609
Reference Temperature
Extrapolated From 32 ,
212° F (1), R°
1263
1667
1297
1600
1271
1530
1960
1298
1591
2003
1293
1621
2064
1288
1617
% Error Between Actual
.Reference-, And
Extrapulated Reference
0.24
0.54
0.39
1.07
0.16
0.46
1.0
0
0.06
1.0
0.15
0.18
0
0.23
0.50
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Table 3: EFFECTS OF REPEATED CYCLING BETWEEN HIGH AND LOW TEMPERATURES
Run
1
2
3
4
5
6
1
2
3
4
5
6
1
2
3
4
5
6 1
Test
temperature
°R
493
493
493
493
493
494
675
674
674
674
675
675
2090
2110
2068
2096
2382
2079
1:0: No:
110
Reference
t»ro
-------
8
taken 1n 1-minute intervals. (Longer times may be required to
attain thermal equilibrium with thick-sheathed thermocouples.)
2. Fill a large Pyrex beaker with water to a depth of no
less than 4 inches. Place several boiling chips 1n the water,
and bring the water to a full boil using a hot plate as the heat
source. Insert the thermocouple(s) in the boiling water to a
depth of at least 2 inches, taking care not to touch the sides
or bottom of the beaker.
Alongside the thermocouple(s) an ASTM reference thermometer
should be placed. If the entire length of the mercury shaft in
the thermometer cannot be Immersed, a temperature correction
2
will be required to give the correct reference temperature.
After 3 minutes both instruments will attain thermal
equilibrium. Simultaneously record temperatures from the ASTM
reference thermometer and the thermocouple-potentiometer three
times at 1-minute Intervals.
3. From the calibration data obtained in the first two
steps of the procedure, plot a linear curve of observed temperature
versus reference temperature. Extrapolate a linear curve from
these two points using the least-squares method, and the result will
be a calibration curve for higher temperatures (up to 1500°F)
accurate to within 1.5 percent on the absolute temperature scale.
4. For even greater accuracy in constructing a calibration
curve, it is recommended that a boiling liquid (such as cooking
oil) be used for a calibration point in the 300°- 500°F range.
-------
References
1. "Standards of Performance for New Stationary Sources,
Revisions to Methods 1 - 8," Title 40, Part 60. Federal Register.
Vol. 42, No. 160 August 18, 1977.
2. Weast, Robert C., Handbook of Chemistry and Physics,
54th Edition. CRC Press, Cleveland, Ohio, 1973, pp. D158.
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10
PROCEDURE FOR CALIBRATING AND USING
DRY GAS VOLUME METERS AS
CALIBRATION STANDARDS
P. R. West!in and R. T. Shlgehara*
INTRODUCTION
Method 5, "Determination of Participate Emissions from Sta-
2
tionary Sources," and APTD-0576, Maintenance. Calibration, and
Operation of Ispklnetlc Sampling Equipment, specify that a wet
test meter be used as the calibration standard for volume measure-
3
ments. A recent study has shown, however, that a properly cali-
brated dry gas volume meter may be used in lieu of a wet test
meter for calibrating Method 5 equipment. The procedure below
outlines the proper calibration steps for preparing a dry gas
volume meter as a calibration standard. In addition, the proce-
dures outlined in APTD-0576 for calibration of a dry gas meter
in the Method 5 sampling train are modified to reflect the find-
ings of the above mentioned study.
CALIBRATING THE STANDARD DRY GAS METER
The dry gas meter to be calibrated and used as a secondary
reference meter should be of high quality and have a scale of
3 liters/rev (0.1 ft /rev). A spirometer (400 liter or more capacity)
may be used for this calibration, although a wet test meter is
usually more practical. The wet test meter should have a scale
3
of 30 liters/rev {1 ft /rev) and capable of measuring volume to within
<_ 1.0 percent; wet test meters should be checked against a spiro-
meter or a liquid displacement meter to ensure the accuracy of
the wet test meter. Spirometers or wet test meters of other sizes
Emission Measurement Branch, ESED, OAQPS, EPA, RTF, NC.
Published in Source Evaluation Society Newsletter 3(1), February 1978
-------
11
may be used, provided that the specified accuracies of the proce-
dure are maintained.
Set up the components as shown in Figure 1. A spirometer may
be used in place of the wet test meter in the system. Run the pump
for at least 5 minutes at a flow rate of about 10 liters/min
(0.35 cfm) to condition the interior surface of the wet test meter.
The pressure drop indicated by the manometer at the inlet side of
the dry gas meter should be minimized [no greater than 100 mm H-0
(4 in. H20) at a flow rate of 30 liters/min (1 cfm)]. This can be
accomplished by using large-diameter tubing connections and straight
pipe fittings.
The data collected for each run include: approximate flow rate
setting, wet test meter volumes, dry gas meter volumes, meter
temperatures, dry gas meter inlet pressure, barometric pressure,
and run time. Figure 2 shows an example data sheet that may be used
in data collection. Repeat runs at each orifice settings at least
three times.
Repeat the calibration runs at no less than five different
flow rates. The range of flow rates should be between 10 and
34 liters/min (0.35 and 1.2 cfm).
Calculate flow rate, Q, for each run using the wet test meter
gas volume, V^., and the run time, e. These calculations are as
wi
follows:
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12
THERMOMETERS
U-TUBE
MANOMETER
PUMP
DRY GAS METER
WET TEST METER
Figure 1, Equipment arrangement for dry-gas meter calibration.
-------
DATE:.
DRY GAS METER IDENTIFICATION:.
BAROMETRIC PRESSURE (Pb):
, in. Hg
APPROXIMATE
FLOW RATE
(Q)
efm
0.40
0.60
0.80
1.00
1.20
SPIROMETER
(WET METER)
GAS VOLUME
(V,)
f|3
DRY GAS
METER
VOLUME
(Vdg)
ft3
TEMPERATURES
SPIRDMETER
(WET METER)
W
°F
DRY GAS METER
INLET
(tj)
°F
OUTLET
(t0)
°F
AVERAGE
(td>
°F
DRY GAS
METER
PRESSURE
(£p)
in. H20
TIME
(6)
min.
FLOW
RATE
(Q)
cfm
METER
METER
COEFFICIENT
-------
14
P V
Q = 0.3855 (t b 2?3) -^ (SI units)
w
Q = 17'65 (t ° 460) ^ (English)
W
Equation 1
Calculate the dry gas meter coefficient, Y. , for each run as
follows:
V, (t . + 273) P.
vrb 13.6J
Equation 2
Vw (t. + 460) P.
Yds = TT (t + 460)- ,p !_3U (Engll"Sh)
(J3 W \ r i • •• A *• I
b 13.6
Where:
Y. = dry gas meter coefficient, dimensionless
o
V = wet test meter volume, liters (ft )
V. = dry gas meter volume, liters (ft )
t.g = average dry gas meter temperature, °C (°F)
t = average wet test meter temperature, °C (°F)
P. = barometric pressure, mm Hg(in. Hg)
Ap = dry gas meter inlet differential pressure, mm H20(in. KLO)
O = run time, min
Compare the three Y . values at each of the flow rates and
-------
15
determine the maximum and minimum values. The difference between
the maximum and minimum values at each flow rate should be no
greater than 0.030. Extra runs may be made in order to complete
this requirement. If this specification cannot be met in six
successive runs, the meter is not suitable as a calibration stan-
dard and should not be used as such. In addition, the meter coef-
ficients should be between 0.95 and 1.05. If these specifications
are met, average the three Y . values at each flow rate resulting
in five average meter coefficients, 7^ .
Prepare a curve of meter coefficient, T, , versus flow rate,
Q, for the dry gas meter. This curve shall be used as a reference
when the meter is used to calibrate other dry gas meters and to
determine whether recallbration is required.
USING THE STANDARD DRY GAS METER AS A CALIBRATION STANDARD
The sampling dry gas meter shall be calibrated as it will be
used in the field; therefore, it shall be installed into the field
meter box, if applicable, prior to calibration. Set up the com-
ponents as shown in Figure 3. Run the pump in the meter box about
15 minutes to warm the pump and other components. Select three
equally spaced flow rates for calibration that cover the range of
flow rates expected in the field. Then collect the data for cali-
bration. These data include approximate flow rate, orifice setting,
initial and final standard dry gas meter volumes, initial and final
meter box gas meter volumes, meter temperatures, barometric pres-
sure, and run time. Repeat the runs at each flow rate at least twice.
-------
16
UMBILICAL
V
METER BOX
CALIBRATION
DRY TEST METER
Figure 3. Meter box calibration set-up.
-------
17
The range of flow rates will depend somewhat on the use of
the meter in the field. That is, if the meter is to be used at
flow rates between 10 and 34 liters/min (0.35 and 1,2 cfm), then
duplicate calibrations should be run at three equally spaced flow
rates between these two values.
Determine the flow rate for each run using the standard dry
gas meter volume, V, .
Q - 0.3855 (t I 273) -f (SI units)
Equation 3
P V
• 17'65 (tH *460) Hr (English)
OS
Using the curve of Y . versus flow rate established earlier for
the standard dry gas meter, determine the meter coefficient, V .»
at each orifice setting, &H, as follows:
V . (tH + 273) Ph
v - v ds d _ _ b
Y " Y
_ _
d " ds FT (t Ac + 273)
d ds
TF
Equation 4
Vds (td * 460J Pb
Yd = Yds FT (t,. + 460) ,p . M } (English)
d ds iF + j
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18
Calculate an average Y . over the range of operation and calculate
a standard deviation for all the calibration runs. The maximum stan-
dard deviation should not exceed a value of +_ 0.020. Figure 4 shows
an example data sheet that may be used for these calibrations with
the necessary calculations. The average Y. should be marked on the
calibrated meter box along with the date of calibration and AH-, the
orifice setting that corresoonds to 21 liters/min (0.75 cfm) at 20° C
and 760 mm Hg (68° F and 29.92 in. Hg).
RECALIBRATION OF STANDARD DRY GAS METER
3
In a recent study a dry gas meter under controlled conditions in
a laboratory maintained its calibration within about 1 percent for
at least 200 hours of operation. It is recommended that the standard
dry gas meter be recalibrated against a wet test meter or spirometer
annually or after every 200 hours of operation, whichever comes first.
This requirement is valid provided the standard dry gas meter is kept
in a laboratory and, if transported, cared for as any other laboratory
instrument. Abuse to the standard meter may cause a change in the
calibration and will require more frequent recallbrations.
As an alternative to full recalibration, a two-point calibration
check may be made. Follow the same procedure and equipment arrange-
ment as for a full recalibration, but run the meter at only two flow
rates [suggested rates are 14 and 28 liters/min (0.5 and 1.0 cfm).
Calculate the meter coefficients for these two points, and compare
the values with the meter calibration curve. If the two coefficients
are within +1.5 percent of the calibration curve values at the same
flow rates, the meter need not be recalibrated until the next date for
-------
DATE:.
METER BOX IDENTIFICATION:.
.CALIBRATION METER IDENTIFICATION:.
. BAROMETRIC PRESSURE (Pb»:
.in. Kg
APPROXIMATE
FLOW
RATE
(5)
efm
0,40
0.80
1.20
ORIFICE
READING
(AH)
in. H20
CALIBRATION
METER
GAS VOLUME
(vds>
ft3
METER BOX
METER
GAS VOLUME
(Vd)
It3
TEMPERATURE
CALIBRATION METER
INLET
(tdti)
op
OUTLET
0F
AVERAGE
fkls)
°F
METER BOX METER
INLET
Udi>
°F
OUTLET
(tdo)
°F
AVERAGE
ft)
°F
AVERAGE
TIME
(0)
min.
METER BOX
METER
COEFFICIENT
{Yd)
(AH(3)
Yd = Yds-
Vd fidi+410)
AH,
0.0317 AH (Id*+ 480)8 2
WHERE: AH@ = ORIFICE PRESSURE DIFFERENTIAL THAT GIVES 0.75 cfmOF AIR AT 70° F AND 29.92 inches OF MERCURY, in. HsO.
TOLERANCE* ±0.15
Figure 4. Example data sheet for calibration of meter box gas meter against a calibration dry gas meter (English units).
-------
20
a recallbration check.
CALIBRATING THE DRY GAS METER FOR METHOD 6 SAMPLING
Method 6, "Determination of Sulfur Dioxide Emissions from
Stationary Sources," requires a meter box with a flow rate of
about 1 liter/win (2 cfh). A dry gas meter may be used as a stan-
dard volume meter for this application, if it has been calibrated
against a wet test meter (1 liter/min) or spirometer in the proper
flow rate range. For this purpose, a dry gas meter standard need
be calibrated at 1 liter/min (2 cfh) and the meter box should be
calibrated against the standard dry gas meter at the same flow rate.
The calculations are similar to the ones described earlier. Again,
the calibrations of the standard meter should be repeated three times
against the wet test meter or spirometer. The calibration of the
meter box gas meter should be repeated twice. Example data sheets
for these calibrations are shown in Figures 5 and 6.
SUMMARY
A dry gas volume meter is calibrated against a spirometer or
a wet test meter under controlled conditions. A curve of meter
coefficient versus meter flow rate is established and kept with the
dry gas meter. The calibrated dry gas meter is then used as a
reference meter in the calibration of meters used in field testing.
REFERENCES
1. "Standards of Performance for New Stationary Sources,
Revisions to Methods 1-8," Title 40, Part 60. Federal Register.
Vol. 42, No. 160. August 18, 1977.
-------
DATE:
DRY GAS METER IDENTIFICATION:.
BAROMETRIC PRESSURE (Pb):
.in. Hg
APPROXIMATE
FLOW RATE
(5)
cfh
2.0
SPIROMETER
(WET METER)
GAS VOLUME
ft3
DRY GAS
METER
VOLUME
Win)
ftJ
TEMPERATURES
SPIROMETER
(WET METER)
fts)
°F
DRY GAS METER
INLET
(tdi)
°F
OUTLET
(tdo>
°F
AVERAGE
(id)
°F
DRY GAS
METER
PRESSURE
(AP)
in. HiO
TIME
(9)
min.
FLOW
RATE
(Q)
cfh
AVERAGE
METER
COEFFICIENT
(Yd$)
1063
© (t, + 460)
Yds--—•
Vdg
Figure 5. Example data sheet for calibration of a standard dry gas meter for method 6 sampling equipment (English units).
-------
DATE:.
CALIBRATION METER IDENTIFICATION.
METER BOX IDENTIFICATION.
BAROMETRIC PRESSURE
.in.Hg
APPROXIMATE
FLOW
RATE
(Q)
cfh
ORIFICE
READING
(AH)
in. H20
CALIBRATION
METER
CAS VOLUME
(vds)
ft3
METER BOX
METER
GAS VOLUME
(Vd)
ft3
TEMPERATURE
CALIBRATION METER
INLET
(tdsi>
°F
OUTLET
(tdso)
°F
AVERAGE
Kds»
°F
METER BOX METER
INLET
°F
OUTLET
(tdo)
°F
AVERAGE
(Id)
°F
AVERAGE
METER BOX
METER
COEFFICIENT
(Yd)
ro
rvs
'! VjS
+ 460)
Figure 6. Example data sheet for calibration of meter box gas meter against a calibration dry gas meter (English units).
-------
23
2. Rom, Jerome J. Maintenance, Calibration, and Operation
of Isokinetic Source Sampling Equipment. Environmental Protection
Agency, Research Triangle Park, N. C. APTD-0576. March, 1972.
3. Wortman, Martin, Robert Vollaro, and Peter Westlin.
Dry-Gas Volume Meter Calibrations. Environmental Protection Agency
monograph. Research Triangle Park, N. C. February, 1977.
-------
24
DRY-GAS VOLUME
METER CALIBRATIONS
By
Martin Wortman, Robert Vollaro and Peter West!in
INTRODUCTION
APTD 0576, "Maintenance, Calibration and Operation of Isokinetic Source-
Sampling Equipment," specifies that the coefficients of dry-gas meters are to
be determined by calibration against a direct-displacement wet test meter.
This requirement can be burdensome to the tester, however, because the capital
cost of wet test meters is high. The objective of these tests was to determine
the feasibility of using a less expensive bellows dry-gas meter as a calibration
standard. The experiments produced data sufficient to study the variation of
the dry-gas meter coefficient (Y) with flow rate; and to determine the stability
of Y over long periods of meter operation. This paper presents the results of
these tests and discusses their significance.
TEST PROGRAM
The coefficient characteristics (i.e., variation of Y with flow rate and
the operating stability of Y) of two dry-gas meters were investigated. At the
outset, each dry-gas meter was calibrated against a spirometer. The calibration
arrangement is shown in Figure la; each dry-gas meter was placed between the
spirometer and a leakless, fiber vane pump, with the pump downstream. An orifice
meter was placed downstream of the pump to measure the approximate gas flow rate,
and a manometer was tapped between the spirometer and dry-gas meter to measure
static pressure. Flow rate was controlled by a coarse control valve and a fine
control bypass valve. The system was carefully leak-checked and any leaks were
eliminated prior to calibration. The spirometer used in these tests was
a Emission Measurement Branch, ESED, OAQPS, EPA, May, 1977.
-------
25
manufactured by the Warren E. Collins Company; it had a 600 liter capacity,
and was a counter-balanced, frictionless device. Since the spirometer is a
primary standard, its calibration coefficient was assumed to be 1.0 and
independent of flow rate. During calibration runs, data were collected at1,
five orifice settings in the range from 0.5 to 8.0 inches of water. The total
volume of gas sampled was recorded at each orifice setting, for both the
dry-gas meter and the spirometer; note that the sample volume was not the same
at each setting, but was about 5 standard cubic feet (SCF) at orifice settings
less than or equal to 1.0 in. HpO, and about 10 SCF at the other orifice settings,
In addition, the barometric pressure, static pressure of the dry-gas meter,
temperature of both the spirometer and dry-gas meter, and the total sampling
time were recorded at each orifice setting. The calibration procedure was
completed twice at each setting.
Following their initial calibrations, the two dry-gas meters were connected
in series downstream of the pump (Figure Ib); the flow rate was set at about 0.8
SCFM, and the system was allowed to run for about 16 hours. After the 16-hour
test run, each dry-gas meter was returned to the calibration system (Figure la),
leak-tested, and recalibrated, over the full range of orifice settings. The
test run and recall'oration sequence was repeated numerous times. The two meters
were run for a combined total of 352 hours. Meter No. JA610713 operated for
192 hours, without adjustment. Meter No. JA610715 operated for 64 hours, at an
average Y value of about 0.95; the meter cams were then reset, to produce a Y
value closer to 1.0, and the meter was run for an additional 96 hours.
A wet test meter was also calibrated against the spirometer. The results
of the wet test meter calibration are presented in the Appendix.
Mention of specific companies or products does not constitute endorsement by the
Environmental Protection Agency.
-------
(a) C«LliBAriOf« SET-OP
TEST SET-UP
BYPASS
VALVE
.COARSE CONTROL
VALVE
26
Figure 1. Equipment arrangement
TABLE I. DRY-GAS VOLUME METES COEFFICIENT VALUES AT
DIFFERENT ORIFICE SETTINGS
Total
Hours
of
Operation
0
15
32
W
64
Cry-gas seter JAS10715 calibration coefficients (Y)
0.5 in. K20
0.962
0.971
0.976 .
'0.973
0.975
1.0 in. H20
0.955
0.954
0.973
0.973
0,953
2.0 in. K20 • 4.0 in. H20
0.967
0.970
0.974
0,967
0.967
0.954
0.962
0.965
0,960.
0.555
6.0 in. n-J i Average
j coeffi-
0.956 [0.551
0.960 JO. 965
0.95S !o.S£9
0.953 ! 0.556
0.949 JO. 953
TABLE II. DRY-GAS VOLUME KETER COEFFICIENT VALUES AT
- DIFFERENT ORIFICE SETTINGS
Tow1,
Dry-gas rater 3A6107b calibration coefficients (V)
Hol"s ; 0.5 In. H,0
Ot 5 <-
Operation
'
i
0 1 1 .029
16 1.025
32
43
1.003
1.020
64 j ' 1.022
53
1.071
i
96
1.024
1.0 in. H20
1.020
1.020
1.041
1.025
1;025
1.023
1.027
2.0 in. K20
4,0 in. t^O
1.021 1.018
1.013 1.011
1.031
1.020
1.029
1.029
1,022
1.021
1.025
1.023
1.023
1.027
6.0 in. H20
1.019
1.010
1.012
8.0 i,i.H2u Average
coet.
f
1.010
0.577
1.D07 •
1.020
; .0' a
i
1.019
T.022
1.021
1.018
l.OU
1.020
1 .020
1.025
i
1.017 jl.OL'4
]
1.015 jl.021
-------
27
METHOD OF DATA ANALYSIS
The data from the experiments are presented in Tables I through III.
A separate analysis was performed with the data listed in each of the three
tables. These data were analyzed as outlined in (1) through (6) below.
(1) The dry-gas meter coefficient, Y (average of two determinations),
was calculated at each orifice setting of each calibration run. The follow
ing equation was used:
V P T
S '
VPb + Tire Ts
Where:
PL = barometric pressure (in. Hg)
Pd = static gauge pressure in dry-gas meter (in. HgO)
T = temperature of spirometer (°R)
Td = temperature of dry-gas meter (°R)
V = sample volume measured by spirometer (SCF)
V. = sample volume measured by dry-gas meter (SCF)
(2) The average dry-gas meter coefficient, T, was calculated for each
calibration run, as follows:
~n
7- ->V'
Y -
-------
28
TABLE III. DRY-GAS VOLUME METER COEFFICIENT VALUES AT
DIFFERENT ORIFICE SETTINGS
r.Oiirs j-
of
Operation
0
16
32
48
64
SO
96
112
128
144
160
176
Dry-gas meter JA610713 calibration coefficients (Y)
0.5 in, H20
1.019
1,005
1,018
1.011
1.015
1.017
1.009
1,008
1.000
1,020
0,998
1.0 in. H20
1.013
1.018
1.017
1,012
1.002
1 .013
1,007 .
1.006
1 .008
1.020
1 .013
1.002 | 0.999
192 1 , 000
1.009
2.0 in. H20
1.013
1.012
1,016
1.004
0.999
1.012
1 .012
1.015
1.015
1.011
1.014
1.013
1 .003
4.0 in. H20
1.010
1.002
1.007
0.991
0,991
1.003
1.008
0.999
1.005
1.006
1 .008
1.015
1,001
6.0 in. H20
0.993
0.992
0.997
0.933
0.986
0.992
1.005
1.005
0.996
1,000
1.003
1.005
0.993
8.0 in. H,0 Averagt
1 coef .
Y
| 1.010
1 .OOC
| 1.011
0.971. 1.000
0.976 |0.99S
0.937 1.000
1,000 1.007
O.SS3 ' 1.0C4
*
1,000 1.CC4
'0.993 jl.CCi
O.S39 |l,OCo
0.557 jl.CCE
1 ,CCO ' " ,CC1
1.05,—
1,04
1.03
1.02
1.03
1,0
0.99
0,98
0.97,
V^__
~~-~~-~-^.
^^*\
~ ^\
\
—
I I 1 l__l ..1 I 1
0 0,1 0.2 0.3 0.4 0.5 0.6 0.7 0,8 0.9 1.0 11 1 ?
GAS FLOW RATE (SCFM)
FIGURE 2. Typical Y Coefficient Versus Gas Flow Rate
(Run Number 1, Meter JA610713)
-------
29
(3) The standard deviation from the average was calculated for each
calibration run, using the following equation:
(Eq. 3)
(4) A plot of Y versus flow rate was constructed for each calibration
run (e.g. Figure 2)
(5) A plot of T versus total hours of meter operation (Figure 3) was
constructed.
(6) A statistical analysis (analysis of variance) of the data was performed,
to determine whether or not the observed variations in Twith operating time
were statistically significant.
RESULTS OF DATA ANALYSIS
The results of the data analysis are presented in Figure 2 through 6, and
in Table IV.
Figure 2 is a plot of Y versus flow rate, for a typical calibration run.
Careful examination of 23 such curves showed that the variation of Y with flow
rate is small for the range of flow rates tested. This range is consistent with
the requirements of EPA Method 5. For Meter No. JA610715, the standard deviation
(G) values ranged from 0.004 to 0.021 and averaged 0.010 during the 96-hour
calibration period; for the 64-hour period, a ranged from 0.005 to 0.011, averaging
0.008. For Meter No. JA610713, the a values ranged from 0.005 to 0.017, and
averaged 0.009. The relationship between Y and flow rate appears to be characteristic
-------
30
of the individual dry-gas meter. Different calibration curves were obtained
for Meters JA610713 and JA610715; however, the general shape of the curves
remained about the same for each meter from one calibration run to the next.
Figure 3 is a plot of 7 versus hours of operation. Figure 3 shows that
the value of 7 changed very little with time; the changes that did occur seemed
to be random in nature. For Meter No. JA.61Q713, the percentage deviation be-
tween the highest and lowest values of 7 (observed over 192 hours of operation)
was only about 1 percent; for Meter No. JA610715, the percentage difference was
about 1 percent during the 64-hour period and 1.5 percent during the 96-hour
period.
The results of the statistical analysis are presented in Table IV. These
results indicate that for the data shown in Tables I, II and III, the variation
of 7 with operating time is not statistically significant. This result is
consistent with the plot of 7 versus operating time shown in Figure 6.
CONCLUSIONS
Recent dry-gas meter calibration experiments have demonstrated the following
(1) The dry-gas meter coefficient appears to be a function of flow rate.
It appears to be charatetersltic of the individual dry-gas meter. The variation
of Y with flow rate is small (about 1 to 2 percent over the orifice setting range
from 0.5 to 8.0 in. HJ)) and non-uniform.
(2) The value of the dry-gas meter coefficient is stable with respect to
operating time. For operating times of up to 192 hours* the variation in 7 was
observed to be only about 1 percent, and was attributable to experimental error.
-------
10!
31
UGM MIW1S
S ass
I
f«Tin COEFFICIENT
HESCT
OS
OO
20
20
40
CO
to
0
80
20
108
40
120
GO
140
TIME OF OPERATION (HOURS)
Figure 3 Ory ps muer coneetion ccallicicni svcrarc vs hours of operation
80
ICO
too
ISO
110
200
TABLE IV. Results of Statistical Analysis
Meter
no.
JA610715
(64-hr, period)
JA610715
(96-hr, period)
JA610713
(192-hour period]
Ca leu la tec
F
valae
0.805
1.73
1.22
F-vslues from
-------
32
APPENDIX
Results of Wet Test
Meter Calibration
The results of the experiments in which a wet test meter was cali-
brated against the spirometer, are presented in Table Al. Table Al shows
that the values of Y (average of four determinations of Y at the indivi-
dual flow rates) for the wet test meter ranged from 0.9885 to 1.0078. The
percentage deviations of the Y values from unity (1.00) ranged from 0.1
to 1.1 percent, and averaged 0.5 percent. These results indicate that at
flow rates ranging from 0.2 to 1.4 cfm, the coefficient of a wet test
meter remains sufficiently close to unity to warrant use of the wet test
meter as a primary standard for the calibration of reference dry-gas meters,
-------
33
CALIBRATION OF DRY GAS METER AT LOW FLOW RATES
R. T. Shigehara and W. F. Roberts
INTRODUCTION
In a description of the moisture (Method 4) and sulfur dioxide (Method 6)
gas-sampling methods, the December 23, 1971, Federal Register specifies the
use of a volume meter "sufficiently accurate to measure the sample volume
within 1%." These gas-sampling trains were evaluated to determine (1) an
acceptable calibration procedure and (2) the accuracy of the volume meters.
PROCEDURE
Test Equipment
The test train metering components used were the same as those specified
by Method 6, except that the metering valve was placed before the pump, a small
surge tank was placed between the pump and flow meter, and the silica gel drying
tube was not used. This modified arrangement does not alter performance of the
23 *
train. The dry gas meter (0.1 ft /rev.) employed was a Rockwell Meter No. 175S;
discussion in this paper is, therefore, limited to this type of meter, A wet
test meter (0.05 ft /rev.) was connected to the inlet of the metering system. A
schematic of the calibration system is shown in Figure 1.
Test Procedure
The calibration was conducted in the following manner:
1. A leak check of the pump system was first conducted. This check con-
sisted of connecting a vacuum gauge (mercury manometer) to the inlet of the meter-
ing system, turning on the pump, pinching off the line after the pump, turning
off the pump after maximum vacuum was reached, and noting the gauge reading. If
any leak was noted by a drop in gauge reading, it was corrected before proceeding
* Mention of a specific company and model number does not signify endorsement
by the Environmental Protection Agency.
-------
WET TEST
METER
DIAPHRAGM
PUMP
DRY GAS
METER
Figure 1. Test sampling train arrangement.
-------
35
with the calibration run. (Note: In a Thomas Model No. 107CA20, leaks can
occur within the pump where the diaphragm is connected by two screws to the
connecting rod.)
2. Using the rotameter as a flow rate indicator, the following information
was gathered: Rotameter readings (levels of 0.5, 1.0, 2,0, 4.0, 6.0, and 10.0 cfh),
wet test meter volumes (running totals at increments of 0.1 ft ) and temperatures,
dry gas meter temperatures and volumes, corresponding to the wet test meter volumes
and running time. Two runs were made at each level of rotameter readings. From
the raw data, the calibration factor, which is the ratio of wet test meter volume
to dry gas meter volume (both corrected for temperature and pressure differences)
was computed.
RESULTS
The data (percent deviation vs. sample volume) for all test runs are plotted
in Figure 2. The maximum percent deviations at a dry gas meter volume of 0.1 and
0.2 ft3 are shown in Table I.
Table I. MAXIMUM DEVIATION AT DRY GAS METER
VOLUME OF 0.1 AND 0.2 FT3
Meter No,
Maximum deviation, percent
1
7
9
11
0.1 ft3
+2.5
-5.0
+5.5
-6.0
+7.9
-6.9
+4.6
-6.3
0.2 ft3
+2.3
-2.0
+3.0
-4.0
+3.3
-3.0
+3.2
-3.5
-------
2
O
I-
LU
Q
A (1)
+4
+3
+1
+2
0
-1
2
3
-4
-5
+3
+2
+1
0
-1
2
-3
-4
-5
rw
I
I
- 8 8
—
o
o
§
o g 8
0 0 0
o
~ o o
0
—
o
— o o .
- ?<4)
—
o
_ 8 °
o
o
0
— o
8 g
~ 6 §
o 0 °
— 8 o
8 o
_ 8
"~ 8
o
: O
0 I
I II
1 I 1
O
8 ° o °
a 1 o §
0 ft Q 8 9
5 B I S §
° 8 S
METER BOX 7
8 o
e ° o °
o ° ° o
° § o 0 §
8 a i § 1
e S o 8 °
§ 0 °
METER BOX 1
I I I
|
—
_
§ 8
« ® —
a o
i 8 -
8
—
. —
—
—
—
•' l-
—
O O
—
• —
1
" 1
o
o
0
8
o
o
0
_ a
B
0
— 0
o
1
0
o 'o
e
0 0
i I
o a
0 0
o
o
o
0
o
e
9
§
8
8
_ METER
- 9(5)
o
0 0
o
o
— o
o
O Q
— o o
o
— o
o
o §
J3) |
o
o
° 8
« 8
I i
o
o
°
o
0
METER
1
1
O1
o
0
e
o
o
BOX
8
o
§
8
o
o
8
BOX
|
o
8
o
o
8
§
8
9
0
o
g
O
0
8
11
I I
0
o
o —
o
0 0 §
8 o o ~~
@O — .
Q Q
0 o 8 _
V
o
—
—
—
—
S 8 8 ~
H o ft
i § 1 -
§ @ o
§ -
o
l i
0.2 0.4 0.6 0.8 1.0 0 * 0.2
VOLUME, ft3
Figure 2. Percent deviation vs. volume.
0.4
0.6
0.8
1.0
-------
37
It is apparent from the figure and the table that the volume used in the
calibration procedure is definitely a factor in the calibration. Originally,
it was assumed that 1 revolution on the dry gas meter would provide a repro-
ducible measurement. The data show, however, that at least 3 revolutions or
3
0.3 ft is necessary to provide a stable calibration factor within +_ 2 percent.
In Figure 3, the percent deviation is plotted against the flow rate; the
data corresponding to the volumes of 0.1 and 0.2 ft are deleted. Figure 3
shows that the calibration factor is a function of flow rate. Because of the
more pronounced effect of flow rate on Meter No. 9, the experiment was repeated
and the resulting data are shown as Test 2 in Figure 3. An effect similar to
the previous one was observed.
The dependency of the calibration factor on flow rate shows that best
accuracy is obtained if calibration factors are determined at individual flow
rates. This observation is not unreasonable as most gas sampling tests involve
sampling at one flow rate or, if proportional sampling is conducted, at rates
varying by no more than a factor of 2. To determine the variation of the cali-
bration at one flow rate, 10 runs were made at a flow rate of 2 cfh, with read-
ings taken at volumes of 0.3, 0.4, 0.5 ft . The results are shown in Figure 4.
This experiment shows that three of the meters are not capable of operating
within +_ 1 percent of the wet test meter readings; a +_ 2 percent deviation is
more reasonable.
CALIBRATION PROCEDURE
On the basis of the results of the experiments previously discussed, the
following calibration procedure is suggested.
1. Leak check the sampling train as described under Test Procedure.
2. Calibrate the dry gas meter at the desired flow rate (as specified by
the test methods).
-------
-1-4
+3
+2
+1
0
z
g -1
3 -2
LU
O
8?
+3
+2
+1
0
-1
-2
METER BOX 7
_ 0 RUN 1 _
* RUN 2
— —
o
O Q
- !•• i
-!: • ! I
• « &
— . —
METER BOX 1
— ' —
g •
o * • .
L '" ! § ° i ~
• Q |
1 1
8
10
+4
+3
+2
+1
0
-1
-2
+4
+3
+2
+1
0
-1
-2
+2
+1
0
-1 r—
-2
I '
O •
I *
1
8
I
o
1
i
• t
* *
FLOW RATE, cfh
Figure 3. Percent deviation vs. flow rate.
METER BOX 9 -TEST 2
o
o
METER BOX 9- TEST 1
CD
i
METER BOX 11
8
10
-------
+2
1+1
I-
<
> 0
LU
O
s? ,
-2
©8
METER BOX 1
O
O
o
METER BOX 7
METER BOX 9
§
METER BOX 11
CO
Id
0.3 0.4 0.5
0.3 0.4 0.5 0.3 0.4 0.5
VOLUME, ft3
Figure 4. Percent deviation vs. volume at 2 cfh.
0.3 0.4 0.5
-------
40
3. Make three independent runs, using at least 5 revolutions, and cal-
culate the calibration factor for each run. The 5 revolutions were selected
over 3 and 4 to minimize the estimation errors in dry gas meter readings and
to allow for the irregular movement of the meter dial.
4. Average the results. If any reading deviates by more than +_ 2 per-
cent from the average, reject the meter.
5. Make periodic checks of meter (after each test). For these checks,
0.3 ft (3 revolutions) or more may be used. If the calibration factor deviates
by more than +_ 2 percent from the average of Step 4 above, recalibrate the dry
gas meter as in Steps 1-4.
REFERENCES
1. Standards of Performance for New Stationary Sources. Federal Register
(Washington) 36 (247): 24882-24895, December 23, 1971.
2. Wortman, M. A. and R. T. Shigehara. Evaluation of Metering Systems for
Gas-Sampling Trains. Stack Sampling News £(9):6-ll, March 1975.
-------
41
CALIBRATION OP PROBE NOZZLE DIAMETER
P. R. West!in and R. T. Shigehara*
Introduction
Document APTD-0176, Maintenance, Calibration, and Operation of
Isokinetic Source-Sampling Equipment, requires that the diameter of
the probe nozzle opening for source sampling be calibrated with a micro-
meter to the nearest 0.001 inch. According to the document, 10 different
diameters should be measured and the average of the readings used as the
nozzle diameter. To ensure roundness, it is specified that the largest
deviation from the average must not exceed 0.002 inch.
The requirement for 10 measurements has been questioned. It has been
suggested, instead, that 3 measurements would be practical and adequate
for accurate nozzle-diameter measurements. To examine this possibility, a
short study was conducted to determine if reasonable accuracy could be ob-
tained from 3 nozzle diameter measurements.
Test Program
Five differently sized nozzles were chosen for this study. The nozzle
tips were visually inspected for dents and roundness, corrosion, and nicks.
If the nozzles were not in good general condition, they were rehoned and
reshaped.
Two technicians were assigned to make 10 measurements of each nozzle
diameter as outlined by the procedure in APTD-0576, except measurements were
made to the nearest 0.0001 inch. Internal calipers were used to gauge the
diameters. The same technicians then made three additional measurements of
Emission Measurement Branch, ESED, OAOPS, EPA, RTF, NC, October 1974
-------
42
the nozzles' diameters following the same technique.
Results and Discussion
The collected data are shown in Table 1. A first analysis of the
data involved a simple comparision of the averages obtained by the two
technicians. First, when comparing the measurements of technician A to
those of technician B, no pair of average readings for the two technicians
varied by more than 0.001 inch when rounded to the nearest 0.001 inch.
This was true for the averages of 3 measurements as well as for the averages
of 10 measurements. The maximum deviation from the average for either
technician exceeded 0.002 inch in only one case, and this value was less
than 0.003 inch.
In the second comparison, it was found that the averages of the 10
readings differed from the averages of 3 readings by no more than 0.001 inch
when rounded to the nearest 0.001 inch. The maximum deviations from the
average tended to the smaller for the 3 reading averages than for the 10
reading averages.
An error or bias in the diameter of a sampling nozzle is more signifi-
cant for smaller nozzles than for larger nozzles. An error of 0.001 inch in
the measurement of the diameter of a 0.125-inch diameter nozzle will intro-
2 3
duce an error of about 1.6 percent in the isokinetic rate adjustments .
For most applications, this is an acceptable error.
In a third analysis of the data, the statistical t-test was used, to
determine if the average of the 3 readings of the nozzle diameter for each
-------
43
TABLE 1
Nozzle Diameter Measurements
(in.)
Nozzle
Number
Reading
1
2
3
4
5
6
7
8
9
10
Average
Maximum
Deviation
11
12
13
Average
Maximum
Deviation
1
Technician
A
0.1536
0.1536
0.1533
0.1554
0,1544
0.1536
0.1556
0.1551
0.1541
0.1547
0.1543
0.0013
0.1530
0.1532
0.1527
0.1530
0,0003
Technician
B
0.1536
0.1536
0.1537
0.1530
0.1528
0.1533
0.1526
0.1523
0.1531
0.1520
0.1530
0.0010
0.1533
0.1536
0.1536
0.1535
0.0002
2
A
0.2511
0.2501
0.2511
0.2508
0.2496
0.2508
0.2501
0.2508
0.2510
0.2512
0.2507
0.0011
0.2504
0.2511
0.2515
0.2510
0.0006
B
0.2515
0.2510
0.2522
0.2518
0.2510
0.2512
0.2505
0.2517
0.2517
0.2519
0.2514
0.0009
0.2501
0.2518
0.2516
0.2512
0.0011
3
A
0.3136
0.3141
0.3139
0.3139
0.3142
0.3138
0.3140
0.3134
0.3141
0.3143
0.3139
0.0005
0.3144
0.3143
0.3142
0.3143
0.0001
B
0.3138
0.3141
0.3144
0.3144
0.3147
0.3137
0.3144
0.3137
0.3141
0.3142
0.3142
0.0005
0.3140
0.3141
0.3139
0.3140
0.0001
4
A
0.3762
0.3767
0.3762
0.3766
0.3770
0.3759
0.3781
0.3763
0.3768
0.3763
0.3766
0.0015
0.3774
0.3780
0.3771
0.3775
0.0005
B
0.3779
0.3769
0.3770
0.3770
0.3771
0.3767
0.3774
0.3765
0.3781
0.3771
0.3772
0.0009
0.3777
0.3771
0.3766
0.3771
0.0006
5
A
0.5014
0.5002
0.4999
0.4992
0.4980
0.5003
0.4995
0. 5007
0.4996
0.5015
0.5000
0.0020
0.4991
0.4984
0.5011
0.4995
0.0016
B
0.4977
0.5008
0.4966
0.5001
0.5000
0.4986
0.5017
0.4982
0.5000
0.4999
0.4994
0.0028
0.5015
0.5003
0.4993
0.5004
0.0011
-------
44
technician was statistically different from average of the 10 readings.
The results for technician A were different from those for technician B.
Statistically significant differences were found between the two values
for nozzle 1 and 4 for this technician. The result indicates a possible
bias between the two sets of readings, but, as noted previously, the actual
magnitude of the bias is small. For technician B» no significant differences
were found between my of the averages.
Summary
It has been found that visual inspection is sufficient to determine
roundness of nozzles. For well-honed nozzles, averaging 3 diameter readings
instead of 10 readings introduces only a small error in the diameter value
and is sufficiently accurate for stack sampling work. To ensure roundness
and to prevent gross errors in measurements of the nozzle tip, however, it
is recommended that the range of diameter readings not exceed 0.004 inch.
References
1. Rom, Jerome J. Maintenance, Calibration, and Operation of Isokinetic
Source-Sampling Equipment. Environmental Protection Agency. Publication
Number APTD-9576. Research Triangle Park, North Carolina. 35 pages. March 1972.
2. Wine, R. Lowell. Statistics for Scientists and Engineers. Englewood
Cliffs, N. J. Prentice-Hall, Inc. 671 pages. 1964.
3. Shigehara, R. T., W. F. Todd, and W. S. Smith. Significance of Errors
in Stack Sampling Measurements. Stack Sampling News. Westport, Conn.
Techronic Publishing Co., Inc. Volume 1. Numbers, pages 6-18. September
1973.
-------
45
LEAK TESTS FOR FLEXIBLE BAGS
F. C. Biddy and R. T. Shigehara*
INTRODUCTION
"Method 3 - Gas Analysis for Carbon Dioxide, Excess Air, and Dry
Molecular Weight", published in the December 23, 1971, Federal Register,
specifies that the flexible bag used in the integrated gas-sampling train
be leak-tested in the laboratory before use. A procedure for leak testing
is not given, however. Therefore, several methods were considered and in-
vestigated. On the basis of this investigation, leak test procedures are
recommended for laboratory and field uses.
TESTING METHODS
Some commonly used leak test methods for flexible bags are as follows:
1. Evacuating the bag to about 25 in. Hg vacuum. Leaks are indicated
by movement of the vacuum gauge indicator, which is left attached. Experi-
ence has shown that this method does not detect leaks at times, because of
the bag film plugging the valve outlet. There are also indications that bag
life is shortened because of the additional number of times the bag is
evacuated. Therefore, this method was dropped from further consideration.
2. Inflating the bag and submerging it in water. Leaks are detected
by air bubbles. This method is very effective in locating leaks. However,
considerable pressure must be exerted on the bag when submerged to locate
tiny leaks, and the bag can only be tested when separated from its protective
container.
Emission Measurement Branch, ESED, OAQPS, EPA, RTP, NC, December 1974
-------
46
3. Inflating the bag to low positive pressure (2-4 in. H^O),
sealing it, and allowing it to stand overnight. A visible collapse of
the bag indicates a leak. Except for the time element, this method is
very effective for determining leaks.
4. Inflating the bag to a low positive pressure (2-4 in. H^O) and
connecting bag to a water manometer. A drop in pressure denotes a leak.
This method is quite sensitive for detecting leaks and can be used in a
short period of time.
RECOMMENDED LEAK CHECK PROCEDURE
On the basis of an investigation of the various testing methods, the
following leak-test procedures are recommended for laboratory and field uses:
1. After the bag is manufactured or upon receipt of the bag from a
distributor, leak-test the bag by either one of the following two methods:
Method A. Inflate the bag to a positive pressure of about 2-4 in.
HpO, connect the bag to a water manometer, and observe the pressure for an
interval of 10 minutes. If any visible drop occurs, repair or discard the
bag. Temperature changes will affect the reading on the manometer. With
a leakless bag, the reading should stabilize within 5 minutes.
Method B. As an alternative method for leak checking a bag in
the laboratory, inflate the bag to a positive pressure of about 2-4 in.
HpO, seal it, and allow it to set overnight. If any visible collapsing of
the bag occurs, repair or discard the bag.
2. Using bags that pass the above leak test, place the bag in a rigid
container (with a vent) to prevent puncture when in the field. Then, leak
-------
47
check the bag, using Method A.
3. In the field, just prior to sampling, conduct the leak test,
using Method A.
REFERENCES
1. Standard of Performance for New Stationary Sources. Federal
Register. 36 (247)r24886, December 23, 1971.
-------
48
ADJUSTMENTS IN THE EPA NOMOGRAPH FOR DIFFERENT PITOT TUBE
COEFFICIENTS AND DRY MOLECULAR WEIGHTS
R. T. Shlgehara*
INTRODUCTION
In order to sample isokinetically, the flow rate through the sampling
train nozzle must be such that its corresponding velocity at the nozzle
tip is equal to that of the measuring point within the stack. For a
sampling train utilizing a calibrated pitot tube and a calibrated orifice
meter, this is done by setting the pressure differential (AH) across the
orifice to the value that corresponds isokinetically to the velocity head
(AP) as determined by the pitot tube in the stack.
Nomographs have become useful tools for determining the proper AH's
for rapid isokinetic sampling rate adjustments. One such nomograph is the
1 2
Environmental Protection Agency Method 5 nomograph, * which is now widely
used and is also commercially available.
Certain assumptions have been made in the construction of the EPA
nomograph. In particular, the pitot tube is assumed to have a coefficient
of 0.85 and the dry molecular weight of the stack gas is assumed to be 29.
The purpose of this paper is to show how adjustments in nomograph values
can be made to account for differences in pitot tube coefficients and in
dry molecular weights. In addition, steps are given for checking the
accuracy of commercially available nomographs.
*Emission Measurement Branch, ESED, OAOPS, EPA, RTF, NC
Published in Stack Sampling News 2(4): 4-11, October 1974
-------
49
NOMENCLATURE
B = water vapor in sample gas at meter, proportion by volume
Win
B = water vapor in stack gas, proportion by volume
ws
C = ratio of K t/K@' dimensionless
C .. = adjusted C value, dimensionless
C = pitot tube coefficient, dimensionless
D = nozzle diameter, in.
AH = orifice meter pressure differential, in. H^
AH
3
@ = AH that gives 0.75 ft/min dry air at 70°F and 29.92 in. Hg
AH t = actual AH read from nomograph scale
Tm Ps
M
act
0.921 [(4)(144)]2
18
= 5.507 x 10, calculated from K . assuming that C = 0.85;
Tm = 530°R (70°F); AH@ = 1.84 in. H20; Pg = Pm = 29.92
in. Hg; Md = 29 lbm/lbm - mile; and BWS = 0.05 (lt>m = pound mass)
ft0
K = orifice meter constant,
^ mTn
(in. Hg) (lbm/lb - mole)] 1/2
m' m
ft
K = pitot tube constant, 85.48 —c
(°R) (in. H20
(in. Hg) (lbm/lbm -
(°R) (in. H90)
...
MQ = dry molecular weight of air of 29 Ib /lb - mole
IP mm
Md = dry molecular weight of stack or sample gas, lbm/lbm - mole
-------
50
Mm = molecular weight of sample gas at meter, lbm/lbm - mole
MS = molecular weight of stack gas, lt>m/lbm - m°le
Ap = velocity head of stack gas, in. H^O
Pp = absolute orifice meter pressure of 29.92 in. Hg
P = absolute meter pressure, in. Hg
P = absolute stack gas pressure, in. Hg
Qffl = orifice meter flow rate of 0.75 ft /min of dry air at 70°F
L and 29.92 in. Hg
T@ = absolute orifice meter temperature of 530°R
T = absolute stack gas temperature, °R
t = meter temperature, °F
t = stack gas temperature, °F
Y • (MS/MJ C(l - Bws)/(l - B^)]2
18 = molecular weight of water, Ib /lb - mole
mm
29 = molecular weight of dry air, lb /lb - mole
60 = conversion factor, sec/min
2 2
144 = conversion factor, in. /ft
BASIC EQUATIONS
Isokinetic Equation
The basic isokinetic equation that relates the pitot tube velocity
head reading (AP) to the orifice meter pressure differential reading
(AH) is:
-------
51
9 9 7 9 & ~ ~*9
60^ K * C_ * D_ P _T M 1 - B. l£
AH =
s mm
ws :
^ r/A\ /1 >i >i \ ~i ^
m 5 5
L- .1
C [(1) (144)]' Pm Ts Ms 1 - Bm.
(1)
Definition ojF AH@
The EPA nomograph equation modifies Equation 1 by defining the
orifice meter constant K_ in terms of a value called "AHg," which is a
AH value measured for a given orifice operating under specifically se-
lected conditions. These selected conditions, based on general sampling
3
conditions and sampling train design, are a flow rate of 0.75 ft /min of
dry air at 70°F and 29.92 in. Hg. In practice, the orifice meter is
first calibrated and K calculated. Then AH« is determined by the fol-
lowing equation:
2
,u _ @ @ @ _ 0.921 /Ox
Anffl - 7y s— \£.)
Molecular Weight and Moisture
Equation 1 assumes that changes in molecular weights are due only to
water in the stack gas. Since M and M are functions of B and B ,
S ill WS WiTI
respectively, the term (M /Mj[(l - B11C)/(1 - B)]? which will be defined
s m ws wm
as "Y," can be written as:
1 - B "2
(3)
M
d
1 - B.
wm
-------
52
In the EPA sampling train, silica gel is used to dry the sample gas
stream, so it is assumed that B is zero. Thus, Equation 3 becomes:
wm
Y .
Md " - Bws' * '" Bws
EPA Isokinetic Equation
Substituting Equations 2 and 4 into Equation 1, the EPA isokinetic
equation is obtained:
602 K,,2 Cp2 ,2 D/ Ps Tm !
4H =
(144)]2PmTs .Md(l -BWS).18BWS'
In practice, the calculation of Equation 5 is carried out by two nomographs.
These are the Operating Nomograph and the Correction Factor for C Nomograph.
EPA Operating Nomograph Equation
The Operation Nomograph equation is obtained by rewriting Equation 5 as:
D4
AH = K@ C ^ Ap (6)
EPA Correction Factor for C_ Nomograph Equation
The factor C in Equation 6 is usually a constant during sampling at a
given site, but it may change for different sampling locations or processes.
The Correction Factor for C Nomograph is designed to account for changes in
AHQ, T , P , P , and B . C and M . are still assumed to remain as 0.85 and
@ m m s ws p d
29, respectively. Thus, this nomograph equation is represented by:
-------
53
r Pm !29 H -Bwsj+18Bws.
L 897.1
ADJUSTING C FOR CHANGES IN C
3
The operations manual for the EPA sampling train limits the selection
of pitot tubes to those that have a coefficient (C ) of 0.85 ±0.02. How-
ever, this limitation is not necessary if C can be adjusted to account for
the differences in C 's. Realizing that C is also the ratio of K +/Kffl, it
P aC L v?
can be adjusted for differences in C 's by the following equation:
^_
0.85
The steps for adjusting C for differences in C 's are as follows:
1. Determine C from the existing Correction Factor for C Nomograph
by the usual manipulations. Example: For AH@ = 2.1 in. H^O,
t = 100°F, B = 0.10 and P /P = 1.0, C equals 1.10.
IN W5 5 ITi
2. Multiply C obtained from step 1 by the ratio of the squares of
C 's as shown in Equation 8 to obtain the adjusted C. Example:
If C = 1.0, then:
C ..,r x = 1.10 ^-9 = 1.52
adj(Cp} 0.852
-------
54
3. Set the adjusted value on the Correction Factor C scale (Example:
) = ^*52) on tne Operating Nomograph.
p
The following may be used as a guide to determine when adjustments
in C 's should be made. Each percent difference from 0.85 will introduce
P
about 1 percent error in the isokinetic rate. Generally, about 5 percent
2 2
error is tolerable. Thus, when 0.87 < C < 0.83, or when 0.95 < C_ /0.85 < 1.05,
— p — — p —
adjustments should not be necessary.
ADJUSTING C FOR CHANGES IN Md
Adjustments for differences in M.'s can be effected by the following
equation:
Cadj(Md) = C (1 - Bws) + 18 »ws/'-«d
In most sampling situations, where air and/or combustion products of
fossil fuels are the principle constituents of the stack gas stream, the
amount of adjustment is quite minimal (see Table I) and adjustments are
not necessary. However, for stack gases consisting primarily of lower
molecular weight gases, e.g. hydrogen, adjustments become significant and
must be made. In addition, the orifice meter will need to be redesigned,
and the Operating Nomograph C-scale may need to be modified by extending
the logarithmetic scale.
(1 - B ) + 18 B /29
Table I shows the adjustment factor, n . B ) + 18 B /H * for
some selected values of M.'s and B 's.
0 WS
-------
55
TABLE I. ADJUSTMENT FACTORS FOR SELECTED M.'s AND B 's
\3 WS
Bws
0
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
Md
2
1.00
0.70
0.53
0.43
0.36
0.30
0.26
0.23
0.20
0.18
0.16
20
1.00
0.99
0.97
0.96
0.94
0.93
0.91
0.90
0.88
0.87
0.85
25
1.00
0.99
0.99
0.98
0.98
0.97
0.97
0.96
0.96
0.95
0.94
28
1.00
1.00
1.00
1.00
1.00
0.99
0.99
0.99
0.99
0.99
0.99
30
1.00
1.00
1.00
1.00
1.00
1.01
1.01
1.01
1.01
1.01
1.01
31
1.00
1.00
1.00
1.01
1.01
1.01
1.01
1.02
1.02
1.02
1.03
As a general rule, adjustments are not necessary when the adjustment
factor Is between 0.90 and 1.10 as each percent difference from 1.00 will
introduce about 0.5 percent error. Beyond the above ranqe, C should be
adjusted in the following manner:
1. Determine C from the Correction Factor for C Nomograph by the
usual manipulations.
2. Multiply C obtained in step 1 by the adjustment factor as shown in
Equation 9 to obtain Cad-/M \.
Set Cadj(M(
Nomograph.
Set C ../„ * on the Correction Factor C-scale of the Operating
-------
56
ACCURACY OF NOMOGRAPHS
When calculations for isokineticity show consistent departure from
100 percent of isokinetic conditions, one cause might be the inaccuracy
of the nomograph. The steps below may be used to check the accuracy of
nomographs.
Overal1 Accuracy
Errors in the Operating Nomograph and Correction Factor for C Nomo-
graph may be offsetting or additive. To check the sum total effect,
Equation 5 should be used. Arbitrarily select values for the variables
and calculate the corresponding &H's. Examples are given in Table II.
For each percent difference, there will be about 0.5 percent error in
adjusting the isokinetic flow rate.
TABLE II. CALCULATED AH's FOR SELECTED VALUES
*H0
1.84
3.00
3.00
2.30
1.00
1.20
2.00
70
0
0
140
140
40
100
i
IIO°BWS;
; 5 '
30
i ,
i 50 i
: 0 '
' 10 :
20
30
V.
1.00
0.90
1.20
1.10
1.00
1.20
1.20
C '
1
1.00 {
0.765
0.569 1
,
1.69
0.563
0.556 •
0.828
Dn
0.30
0.25
0.20
0.40
0.25
0.20
S i
1000 ;
500
200 |
1500 :
300 j
200 '
0.25 500 "
1
ap
1.0
2.0
2.0
0.7
2.0
1.0
2.0
AH | *Hact M1ff;j
1 i
3.06 , '
3.43 :
1.52 i
8.51 ,
4.33
0.74
3.71
Generally, about 10 to 15 percent differences will yield sampling rates
within 10 percent of isokinetic. If greater differences are encountered, the
-------
57
separate nomographs may be checked as follows:
Operating Nomograph
K-Factor Line and AH and Ap_ Scales. The accuracy of the placement of the
K-Factor line and the AH and Ap scales may be checked in the manner shown in
Table III. Deviations of 10 percent from the true AH values are generally
acceptable.
Table III. K-FACTOR LINE AND AH AND Ap SCALES CHECK
Set Pivot Point after Aligning:
Ap = 0.001; AH = 0.1
Ap = 10; AH = 10
Ap = 0.1; AH = 1.0
Set Ap to:
0.01
0.1
1.0
0.1
1.0
0.01
AH Should Read:
1.0
10
1.0
0.1
10
0.1
£>.!*« and D Scales. To check the C, t , and D scales, arbitrarily
select values for the variables in Equation 6 and calculate AH's. Nomograph
manipulations should yield values corresponding to the calculated values of
AH's. Examples are given in Table IV. As a general rule, a 10 percent
deviation may be tolerated without appreciable errors. However, it should
be realized that the inaccuracies here, which include the inaccuracies from
the placement of the K-Factor line and the AH and Ap scales, may be offset
or compounded by inaccuracies in the Correction Factor for C Nomograph.
-------
58
Table IV. CALCULATED &H's FOR SELECTED VALUES
c
2.0
1.5
1.0
0.7
0.5
Dn
0.5
0.4
0.3
0.25
0.2
ts (°F)
2500
1500
1000
500
200
dp
0.2
0.7
1.0
2.0
1.0
&H
4.65
7.55
3.06
3.14
0.668
Correction Factor for C Nomograph
To check the accuracy of the Correction Factor for C Nomograph,
arbitrarily select values for the variables in Equation 7 and calculate the
corresponding C's. As a general rule, the nomograph manipulations should
yield, to within 10 percent, the same values of C's. The example calculations
in Table II may be used for this purpose.
SUMMARY
Equations and steps have been given that show how the factor C of the
EPA Method 5 Monograph can be adjusted to account for values of(C )the pi tot
tubr'coefflcient and dry molecular weigKlt'of the sample gas (M.) different
from 0.85 and 29, respectively. In addition, directions and tables have been
presented for checking the accuracy of commercially available nomographs.
ACKNOWLEDGEMENT
The author wishes to thank Mr. Walter S. Smith of Entropy Evironmentalists,
Inc., Research Triangle Park, North Carolina, for his assistance in writing
this paper.
-------
59
REFERENCES
1. Smith, M.S., R.M. Mirtin , D.I. Durst, R.6. Hyland, T.J. Logan, and
C.B. Hager. Stack Gas Sampling Improved and Simplified with New Equipment.
National Center for Air Pollution Control, Cincinnati, Ohio. (Presented at
the 60th Annual Meeting of the Air Pollution Control Association. Cleveland.
June 11-16, 1967.)
2. Standards of Performance for New Stationary Sources. Federal Register.
Vol. 36, No! 247. December 23, 1971. p. 24888-24890.
3. Rom, J,J. Maintenance, Calibration, and Operation of Isokinetic Source-
sampling Equipment. U.S. Environmental Protection Agency. Research Triangle
Park, N.C. Publication No. APTD-0476. March 1972.
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60
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
SUBJECT Expansion of EPA Nomograph DATE MAY 21 1974
FROM R. T. Shigehara, TSS, EMB &
To Emission Measurement Branch Personnel
Enclosed is a copy of the expanded EPA nomograph for determining
the Correction Factor C for high moisture contents. Directions are on
the nomograph.
Directions on how to expand the C-scale on the Operating Nomograph
are also enclosed.
Should you have any questions, please contact me.
Enclosure
EPA form 1320—« (11—711
-------
nef
1.5
Ref "
-E
1
i
i
i
___
T.
15O-=
ioo-i
5O~~
Q_
-50-
1
r\
Ref =
3 I0~
MM
20 |
-
40—11
§0-=
M. f^
° —
—
70
—
—
— ~
Factor C Nomograph
on
C
,
-^
—
~E
—
-
_
2.O
1.O
0.8
1.2
O.6
1.1
0,4
10
02 °9
0.8
li
—
-
=—
1. Align AH@ with T to obtain Ref 1.
2. Align Ref 1 with «H20 to obtain Ref 2.
3. Align Ref 2 with Ps/Pm to obtain Ref 3.
4. Aliqn Ref 3 with A on &H« scale to obtain C
-------
62
Expanding Logarithmic Scales
1. Determine the distance between 2.0 and 1.0. This distance should be
the same as between 1.0 and 0.5, since the ratio is 2.
2. Obtain other points by using this ratio and distance obtained from (1)
This is illustrated below.
fc2.0 —,-2
i
-0.8 j
1.8
All distances shown are equal
;0.4
-,-0.8
~°'5-*-0.45
).25
0.1
-t- 0.4
0.2
1-0.1
0.6
--0.3
-L-0.15
etc,
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63
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
SUBJECT EPA Nomograph Adjustments °*TE MAY 1 6 1974
FROM Roger T. Shigehara, TSS, EMB f*
TO Emission Measurement Branch Personnel
In a recent source test, high moisture content and high dry mole-
cular weight effluent gases were encountered. Since the Environmental
Protection Agency nomograph has a moisture scale range of only 0-50%
and assumes a dry molecular weight of 29, adjustments to the EPA
nomograph are necessary.
Attempts have been made to expand the % H^O and the Correction Factor
C scales. However, due to the magnitude of expansion, slight inaccuracies
in the present nomograph are magnified. Thus, an entirely new nomograph
for the Correction Factor C must be constructed.
Since the construction of the nomograph will take some time, the
attached procedure is recommended for the interim. To handle the calcula-
tions, it is suggested that you use electronic pocket calculators.
Should you have any questions, please contact me.
Enclosure
EPA Form 1320-6 111-711
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64
MAY 1 6 19/4
DIRECTIONS FOR SETTING EPA NOMOGRAPH
1. Obtain the following information:
a.
b.
c.
d.
e.
f.
9-
h.
i.
j.
Item
Orifice meter coefficient, AH@
Pi tot tube coefficient, C
Abs. stack pressure, P = P. + P
Abs. meter pressure, P = P^
m oar
Abs. meter temperature, T = t + 460
mm
Abs. stack temperature, T = t + 460
Dry molecular weight, M,
Moisture content, B = HHgO/lOO
Exact nozzle diameter, D
n
Average velocity head, dp
2. Calculate AH using the following equation:
PS Tm Md (1 -
Dimensions
in. H20
dimensionless
in. Hg
in. Hg
°R
°R
Ib/lb-mole
dimensionless
in.
in H20
AH = 849.6 C.
18 B.
This equation may be used to account for differences in C 's, M.'s,
%HpO, and/or any other variable within the equation.
3. Align calculated aH with average ap on operating nomograph and set
K-Factor pivot point.
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65
GRAPHICAL TECHNIQUE FOR SETTING PROPORTIONAL
SAMPLING FLOW RATES
R. T. Shigehara*
INTRODUCTION
The December 23, 1971, Federal Register requires in certain test
methods that the gaseous sample from an effluent gas stream be extracted
in a proportional manner. "Proportional sampling," according to the
Federaj Register, means "sampling at a rate that produces a constant ratio
of sampling rate to stack gas flow rate." In other words, the ratio (k) of
the gas velocity (v ) at the tip of the probe nozzle to the velocity (v )
of the approaching gas stream at a measuring point within the stack cross
section must remain a constant throughout the sampling period. In equation
form:
— - k CM
v ~ K *''
Since the velocities v and v are not directly measurable, the normal
procedure is to regulate the sampling train meter flow rate (Q ) in relation
to the velocity head Up) of the gas stream such that Equation 1 is satis-
fied. This paper will discuss a graphical technique for setting proportional
sampling flow rates for a sampling train using a rotameter or an orifice
meter as the metering device and a pi tot tube as the means for measuring the
velocity head. Because arrangements of sampling train components differ,
resulting in a difference in treatment, this discussion will limit itself to
the gaseous sampling trains shown in the Federal Regis ter (shown later in
Figure 1).
Emission Measurement Branch, ESED, OAOPS, EPA, RTP, NC, October 1974
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66
NOMENCLATURE
2
= cross sectional area of nozzle tip, ft
B = water vapor in sample gas at meter, proportion by volume
WiTI
B.._ = water vapor in sample gas at nozzle tip, proportion by volume
wn
B = water vapor in stack gas, proportion by volume
ws
C = pitot tube coefficient, dimensionless
AH = orifice meter pressure differential, in. H~0
K = overall constant
k = proportionality constant, dimensionless
u _ or-jfice meter constant,
K_ = pitot tube constant, 85.48 ||-
p
ft3
min
(in. Hg)(lbm/lbm-mole)
(°R)(in. H20)
1/2
(in. Hg)(lbm/lbm-mole)
(°RJTin.
M = molecular weight of sample gas at meter, Ib /lb -mole
m mm
M = molecular weight of stack gas, Ib /Ib -mole
s mm
Ap = velocity head of stack gas, in. HpO
P = absolute meter pressure, in. Hg
P = absolute pressure at nozzle tip, in. Hg
P = absolute stack gas pressure, in. Hg
3
Q = volumetric flow rate at meter, ft /min
Q = volumetric flow rate at nozzle tip, ft /min
T = absolute meter temperature, °R
T = absolute stack gas temperature at nozzle tip, °R
T = absolute stack gas temperature, °R
vn = velocity of sample gas stream at nozzle tip, ft/sec
1/2
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67
v = velocity of stack gas stream at measuring point, ft/sec
60 = conversion factor, sec/mln
DEVELOPMENT OF GENERAL EQUATIONS
General equations that relate the velocity head readingsUp) to the
flow rate meter readings will be developed in this section. The velocity
at a point within the stack cross section as measured by a pitot tube is
given by the equation:
•60
The velocity v can be written in terms of volumetric flow rate as:
and, assuming that moisture is the only condensible matter, the relationship
between the flow rate (Q ) at the nozzle tip and the flow rate (Qm) at the
flow meter is:
V1 - In' Pn . V1 - B.J "m
T T
n m
Since the conditions at the nozzle tip and at the measuring point within the
stack are identical, it follows that:
Pn = Ps (5)
Tn - Ts (6)
wn ~ ws
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68
The flow rate through an orifice meter is given by:
nlAH
(8)
For a sampling train using an orifice meter, the general equation that
relates Ap to AH for setting proportional sampling rates is obtained by
substituting Equations 2 through 8 into Equation 1:
Note that when k = 1, Equation 9 reduces to the isokinetic equation.
For a sampling train using a rotameter, the general equation that
relates AP to Q for setting proportional sampling rates is obtained by
substituting Equations 2 through 7 into Equation 1:
Q = 60 k " *~ A ws
(1 - B ) P
x wnr m
The reason for using this form instead of one relating AP to the rotameter
reading is that the latter equation becomes complicated since most commonly
used rotameters are viscosity dependent.
EVALUATION OF GENERAL EQUATIONS
Equations 9 and 10 must be evaluated for a specific sampling train and
sampling source. Considering the arrangement of the sampling train com-
ponents shown in Figure 1 and the conditions of most sampling sources, the
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69
following terms can be considered to remain as constants or nearly so:
C , An> BWS, TS> T , M , PS> and P . Because a desiccant is used in the
sampling train, B can be considered to be negligible, i.e. zero. Com-
win
bining these terms with the proportionality constant k and the other constants,
60 and K , into an overall constant K, Equations 9 and 10 can be rewritten
as:
AH = K Ap (11)
Qm = K/Ap- (12)
The construction of graphs to aid in the setting of proportional rates will
now be discussed for Equations 11 and 12.
CONSTRUCTION AND USE OF GRAPHS
Since size ranges of orifice meters and rotameters vary, examples
3
using a rotameter flow range of 0 to 10 ft /hr and an orifice AH range of
0 to 10 in. HpO corresponding to 0 to 10 ft /hr will be used to illustrate
the technique. In addition, a possible Ap range of 0.001 to 10 in. H^O
will be used.
Equation 11
The operation of Equation 11 is best carried out by a nomograph. To
construct the nomograph:
1. Position two log scales, two cycles for AH and four cycles for
A, parallel to each other in the manner shown in Figure 2. Label
the scales as shown.
2. Locate the intersects A and B as shown in Figure 2. Then draw
the K-factor line.
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70
PfiOCE [f.-O PACKS)
WITH CUAKTZ Oft
SILICA GEL DRYING T&E
,r-,V,!DGtT WjnCLER MIDGET 1MPINGEHS
DfiYGASMtTBi ROTAMHT2S
PSOSE iP;o
SAMPLING TRAIN WITH RQTAMETER
S;LICA GEL OWING TUSE
«,'!f i£T E'JSLER MIDGET IWlNGERS
/
OSVCASMJTift
SAMPLING TRAIN WITH ORIFICE
Figure 1. Schematic showing arrangement of sampling
train components.
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71
To use this nomograph:
1. Determine from a rough preliminary traverse the minimum and
maximum Ap's. Assume, for this example, that the values are
0.1 and 0.4 in. H^O, respectively.
2. Align the midpoint of the minimum and maximum Ap's from step 1
(example: 0.25 in. H^O) with the midpoint of the orifice meter
flow range (example: AH = 5 in. H^O), or some other convenient
AH, and determine the pivot point P on the K-factor line as
shown in Figure 3.
3. Align minimum and maximum Ap's with pivot point P to check if
the corresponding AH's will fall within the flow range of the
orifice meter. Allow some leeway on both sides as a safety fac-
tor. If necessary, reset the pivot point using a more suitable
AH.
4. During sampling, determine AH from Ap's of the pi tot tube and
adjust sampling rate accordingly.
Note: The allowable range of flow rate through the collector system
should also be considered. Too large a flow rate will cause carryover,
while too low a flow rate will sometimes cause inefficient collection. If
sampling equipment is properly engineered, the flow meters will adequately
cover the allowable range through the collector system and the median
velocity pressure should be aligned with the nominal rated flow through the
collector.
Equation 12
The operation of Equation 12 is also best carried out by a nomograph.
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72
K-FACTOR
0.001-
mor READij
Figure 2. Nomograph construction for Equation 11.
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73
The steps in construction and use of the nomograph are identical to that
of Equation 11, except that a Q scale replaces the &H scale and the K-fac-
tor line is now midway between the two log scales. If the rotameter scale
does not read directly in cubic feet per hour, corresponding scale readings
may be substituted for Q via a calibration curve. All of this is illustrated
in Figures 4 and 5 in conjunction with Table 1.
Tube reading
Table 1. EXAMPLE ROTAMETER CALIBRATION
3 3
Q_, ft /hr Tube reading Q » ft /hr Tube reading
25
20
18
16
14
11,07
8.61
7.59
6.49
5.50
12
10
8
7
6
4.53
3.60
2.65
2.20
1.76
5
4
3
2
1.33
0.916
0.535
0.234
GUIDELINE FOR APPLYING PROPORTIONAL SAMPLING
The need for sampling proportionately is a function of the variation of
the pollutant concentration with respect to velocity. Since this relationship
is not generally known, a sampling rate proportional to the stack velocity will
give the desired time integrated average pollutant concentration.
On a practical scale, a constant sampling flow rate will most likely
meet the proportionality requirement in sources under steady state operations,
e.g., power plants, municipal incinerators, and cement plants. As a rule of
thumb, a constant flow rate may be used when velocity variations do not
exceed 20 percent from the average. Beyond this, the sampling flow rate
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74
OSIFICE READING
AH
10-=;
K-Factor
0.9
—S
0.8-|
^
0.6—I
0.5-f
0.4-1
0.3—=
0.2 —
0.1—I
\
\
0.001 1
WOT READING
0.002-=
0.003-1
0.004-41
0.005-
0.006-
0.008-=
0.01-=
0.02—E
0.03-
0.04-
0.05-
0.06-
_ 0.08^
0.2^-i
0.3—1
X
0.4-
0.5—=
3—=
Figure 3. Determining suitable pivot point for
setting proportional flow rates.
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75
Rotameter Flow Rate
K-Factor
0.001-
Figure 4. Nomograph construction for Equation 12.
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76
Rotameter
Tube Rotameter
Reading Flow
Rate
10-
20
18
16
14
12
10
8
7
6
5
6-1
SB
0.8
0.7
0.6
0.5-
0.4-
0.3-=
o.i—
K-Factor
\
0.001 —
PJ7OT READING
AP -.
0.002-3
0.003-^
0.004-
0.065-I
0.006-^
0.008-=
0.02-^
0.03-
0.04-
0.05-
0.06-
.0.08-
Q.f-
X v.
0.4-
O.S-
0.6-
O.B"
i.o-
4
5
6
Figure 5
Determining suitable pivot ppint for setting
proportional flow rates for Equation 12
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77
should be regulated In relation to the velocity such that the proportionality
constant k varies no more than 20 percent from the average.
SUMMARY
A graphical technique for setting proportional flow rates when sampling
for gaseous pollutants with sampling trains utilizing either an orifice
meter or rotameter has been discussed. Steps for constructing nomographs
and their use have been outlined.
REFERENCES
1. Standards of Performance for New Stationary Sources. Federal Register.
Vol. 36, No. 247, Thursday, December 23, 1971.
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing}
1 REPORT NO
EPA-450/2-78-042C
3 RECIPIENT'S ACCESSION NO.
4 TITLE AND SUBTITLE
Stack Sampling Technical Information:
of Monographs and Papers Volume III
A Collection
5 REPORT DATE
October 1978
6 PERFORMING ORGANIZATION CODE
AUTHOR(S)
Roger T. Shigehara (Editor)
8. PERFORMING ORGANIZATION REPORT NO
9 PERFORMING ORGANIZATION NAME AND ADDRESS
U.S. Environmental Protection Agency
Emission Standards and Engineering Division
Emission Measurement Branch
Research Triangle Park, NC 27711
10 PROGRAM ELEMENT NO
11 CONTRACT/GRANT NO.
12 SPONSORING AGENCY NAME AND ADDRESS
13 TYPE OF REPORT AND PERIOD COVERED
Same as above.
14 SPONSORING AGENCY CODE
15 SUPPLEMENTARY NOTES
16 ABSTRACT
"Stack Sampling Technical Information" is a four-volume collection of monographs
and papers which have been compiled by the Emission Measurement Branch, ESED, OAQPS,
The information specifically relate to current EPA test methods and compliance
test procedures. The data presented in some of these documents have served as
the basis for a number of revisions made in the EPA Reference Methods 1 through 8.
Several of the documents are also useful in determining acceptable alternative
procedures.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Gas Sampling
Filtered Particle Sampling
Gas Analysis
Stack Sampling
14B
14D
18 DISTRIBUTION STATEMEN1
Unlimited
19 SECURITY CLASS (This Report)
Unclassified
21 NO OF PAGES
90
20 SECURITY CLASS (Thispage)
Unclassified
22 PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
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