MAINTENANCE, CALIBRATION, AND OPERATION
OF
ISOKINETIC SOURCE-SAMPLING EQUIPMENT
by
Jerome J. Rom
Applied Technology Division
ENVIRONMENTAL PROTECTION AGENCY
Office of Air Programs
Research Triangle Park, North Carolina
March 1972
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The APTD (Air Pollution Technical Data) series of reports is issued by the Environ-
mental Protection Agency, to report technical data of interest to a limited number
of readers. Copies of APTD reports are available free of charge to Federal
employees, current contractors and grantees, and nonprofit organizations - as
supplies permit - from the Office of Technical Information and Publications,
Environmental Protection Agency, Research Triangle Park, North Carolina 27711,
or from the National Technical Information Service, 5285 Port Royal Road, Spring-
field, Virginia 22151.
Office of Air Programs Publication No. APTD-0576
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ACKNOWLEDGMENTS
The author wishes to thank many individuals for their assistance in the pre-
paration of this manuscript. Special thanks go to Roger T. Shigehara of the Emis-
sion Testing Branch for his efforts in incorporating many of the suggestions and to
Walter S. Smith of the Institute for Air Pollution Training for his review of the
manuscript and his helpful suggestions.
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CONTENTS
Page
LIST OF FIGURES vii
INTRODUCTION 1
MAINTENANCE 3
PITOBE ASSEMBLY 3
Preliminary Disassembly 3
Probe 3
Pitot-Probe Sheath 4
Swagelok Union 4
Assembly 4
NOZZLES 6
METER BOX ASSEMBLY 6
Casing 6
Pump Oil and Filter 6
Thermometers 7
Quick Connects 7
Dual Manometer 7
Pitot-Tube Lines 7
Solenoid Valve 7
Lights and Switches 9
Orifice Meter Lines 9
Timer 9
Amphenol Outlet and Variable Transformer 10
Vacuum System 10
Calibration 10
SAMPLE BOX ASSEMBLY 11
Ice Bath 11
Electrical System 11
POLLUTANT COLLECTOR 15
Glass Parts 15
Glass Frit 15
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Page
Greenburg-Smith Impinger Orifice „ 17
Filter-Holder Gasket 17
UMBILICAL CORD 17
Quick Connects 17
Thermometer „ 17
Electrical Lines 18
Check Valve „ . 18
Vacuum and Pitot Lines 18
CALIBRATION 21
NOZZLE DIAMETER 21
PITOT TUBE 21
DRY GAS METER AND ORIFICE METER 21
HEATING PROBE CALIBRATION 22
FIELD OPERATION 25
NOMOGRAPHS 25
SAMPLE COLLECTION ASSEMBLY 28
Pitobe Assembly 28
Sample Box Assembly 30
LEAK TEST 30
FINAL SAMPLING TRAIN ASSEMBLY 30
SAMPLE RUN 31
SHUTDOWN 33
REFERENCES 35
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LIST OF FIGURES
Figure Page
1 Sampling Train 2
2 Pitobe Assembly 3
3 Suggested Pitobe Assembly Check List 5
4 Pump Meter Assembly 6
5 Front Panel of Meter Box 8
6 Solenoid Assembly Diagram 9
7 Meter Box Wiring Diagram 10
8 Suggested Meter Box Assembly Check List H
9 Suggested Orifice and Dry Gas Meter Calibration and
Calculation Form 12
10 Sample" Box 13
11 Amphenol Adapter 13
12 Amphenol Wiring Diagram 14
13 Suggested Sample Box Check List 14
14 Sample Box Glassware Assembly 15
15 Impinge r 16
16 Glass Filter Holder Assembly 16
17 Glass Frit Pressure Drop Check 16
18 Umbilical Cord 17
19 Suggested Umbilical Cord Check List 19
20 Calibration Setup 22
21 Probe Temperatures 23
22 Nomograph for Correction Factor C 26
23 Use of Nomograph in Selecting Nozzle and Setting K Factor 27
24 Nomograph Operation to Obtain Desired Orifice Meter Settings .... 29
25 Suggested Particulate Field Data Form 32
vn
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MAINTENANCE, CALIBRATION, AND OPERATION
OF
ISOKINETIC SOURCE-SAMPLING EQUIPMENT
INTRODUCTION
The purpose of this publication is to explain the maintenance, calibration,
and operation of the isokinetic source-sampling equipment described in Construction
Details of Isokinetic Source-Sampling Equipment as performed by the Emission
Testing Branch of the Office of Air Programs, Environmental Protection Agency.
This procedure has been used satisfactorily and is presented as a guide to assist
interested personnel in using the equipment.
The sampling train has four major components; (1) the pitobe assembly,
which includes the probe nozzle, a heated glass probe, and a pitot tube for monitor-
ing gas velocity during sampling; (2) the meter box assembly, which consists of a
system of manometers, an orifice meter, a vacuum pump, a dry gas meter, and
electrical controls for sampling; (3) the sample box assembly, which contains the
glassware; and (4) the umbilical cord, which connects the sample box with the
meter box. A representation of the sampling train is shown in Figure 1. The
maintenance and calibration procedure described for each of the components should
be followed in the shop or laboratory in preparation for each sampling test.
459-345 O - 72 - 2
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D)
C
"o.
to
c/3
O)
LL
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MAINTENANCE
PITOBE ASSEMBLY
Preliminary Disassembly
To disassemble the pitobe, first remove the Swagelok* union (parts Z through
7) except for the welded nut (8) as shown in Figure 2. The nozzle (1) is usually
removed in the field and carried separately. Check for broken glass chips.
1131 GLASS BALL JOINT (10) GLASS PROBE 191 PROBE SHEATH 18) NUT (61 0 RING (41 FRONT FERRULE (2\ NUT ID NOZZLE
(11) HIGH TEMPERATURE TAPE
ll«l RUBBER STOPPER
(151 POWER CORD
112) HEAT ING HIRE (101 CLASS PROBE HELD 171 REAR FERRULE I5l UNION |3| REAR FERRULE
(HI QUICK CONNECTS
Figure 2. Pitobe assembly.
Probe
Remove the glass probe (10) from the sheath (9) and check visually for
broken or fractured sections. The most common area of broken or fractured sec-
tions is within 1-1/2 inches from the front and approximately 3 inches from the
rear. Some fractures on the back end are hard to see because of the tape (11) and
rubber stopper (14). One way of checking is to gently twist the glass probe and
listen for grating sounds. Inspect the electrical system of the probe for visible
shorts or burned spots shown by uniform darkening of the high-temperature insula-
tion tape (11), and the power cord connection (15). Then plug the power cord into a
variable transformer and set the power rating at about 55 volts. The probe should
become warm to the touch over its entire length in a few minutes. If the probe does
not heat, check the variable transformer for proper voltage and for loose connec-
tions in the plug (15) and Nichrome wire. Shorts are indicated by partial heating in
^Mention of a specific company or product name does not constitute endorsement
by the Environmental Protection Agency.
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the rear portion of the probe. Breaks in the Nichrome wire can be checked with an
ohmmeter or a battery-light system.
If the probe is in good order, proceed with the cleaning process. Wipe the
grease from the ball joint. Clean the probe internally by brushing, first using tap
water, then distilled, deionized water followed by acetone. Rinse the probe with
acetone and allow it to dry in the air. Inspect visually for cleanliness and repeat
the procedure if necessary.
Pitot-Probe Sheath
Remove the quick connects (17) from the pitot tube (16) and wipe them clean.
A drop of penetrating oil helps keep them in good working condition.
Use compressed air to blow out the pitot tube. Both the pitot tube and sheath
should be wiped or washed clean with water and air dried. Inspect the pitot tube
openings for damage and misalignment, and, if necessary, repair and recalibrate
the tube according to the procedure given in the Calibration section of this report.
Swagelok Union
Clean the stainless steel union (5), nut (2), ferrules (3,4, 7), and rubber
O-ring (6) by scrubbing. Rinse with distilled, deionized water, and then with
acetone; air dry.
Assembly
After the parts are cleaned and inspected, assemble the pitobe component
except the nozzle. Insert the probe into the sheath, making sure that the rubber
stopper seats properly onto the sheath. The front end of the glass probe should be
about flush with the front end of the welded union nut (8). This prevents the union
(5) from pushing against the probe and chipping the end or unseating the rubber
stopper. Replace the Swagelok union (2-7), making sure that the rear ferrule (7)
is on backwards. Asbestos cord should be substituted for the O-ring when stack
temperatures in excess of 500° F are expected. The union (5) should be only finger
tight. The use of a wrench can cause cracks within the first 1/2 inch of the probe
or, if the nut (8) was not welded square with the sheath, cracks about 1-1/2 inches
from the front.
Cover the open ends of the probe with serum caps or similar covers to avoid
contamination.
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A sample check list is shown in Figure 3. There should be at least two sets
of pitches of the desired length for each sample box with each pitobe identified.
Date Probe No.
Probe
Glass probe
Rubber stopper.
Insulation tape.
Power cord extension
Heating system
Clean
Pitot-probe sheath
Quick connects
Pi tot tube
Sheath and welded nut.
Clean
Calibration (pitot tube)
Swagelok union
Probe side
Rear ss ferrule (backwards)
Rubber 0-ring
Asbestos cord
Union
Nozzle side
Front ss ferrule.
Rear ss ferrule _
Clean
General remarks:
Note: 25-foot Nichrome wire on particulate probes.
Initial each item when checked and write in any remarks.
Figure 3. Suggested pitobe assembly check list.
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NOZZLES
Inspect the knife edge of the nozzle for damage. If damaged, repair and
recalibrate the nozzle according to the procedure in the Calibration section. Clean
the nozzle by scrubbing and rinse with distilled, deionized water, and then with
acetone; air dry. Cover the open ends with serum caps or similar covers to avoid
contamination or damage to the knife edge.
There should be a selection of nozzles ranging from 1/8 to 1/2 inch in diameter
in 1/16-inch increments with two or three sets of each size. The exact diameters
should be etched on the shank of each of the nozzles and all the nozzles kept in a
separate box.
METER BOX ASSEMBLY
Casing
Remove the meter box casing, check the general condition, and make neces-
sary repairs.
Pump Oil and Filter
Change the pump lubricating oil (28), if dirty; fill to mark; and clean the
pump filter (27). The parts are identified in Figure 4.
(27) PUMP FILTER
(25) THERMOMETERS
(24) ORIFICE
A
(6) FINE ADJUST VALVE (8) VACUUM GAUGE
(!) COARSE ADJUST
VALVE
(28) LUBRICATOR
(5)! DRY TEST METER
Figure 4. Pump-meter assembly.
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Thermometers
Check the dry-gas-meter thermometers (25). The temperature should check
against room temperature using a mercury-in-glass thermometer as the standard.
Quick Connects
Wipe the quick connects (9) clean (Figure 5). A drop of penetrating oil helps
keep them in good working condition.
,12) MANOMETER PORTS
(31 FILL PLUG SCREW
(4) VALVE SWITCH
(51 DRY GAS METER.
(61 FINE ADJUST
(71 COARSE ADJUST
(8) VACUUM GAUG
(9) MANOMETER QUICK CONNECT,
(10) SAMPLE PORT QUICK-CONNECT.
(11) AMPHENOL CONNECTOR
(12) POWER INDICATOR.
LIGHT
(131 TIMER INDICATOR.
LIGHT
.111 DUAL MANOMETER
23) DRAIN SCREWS
(221 PLUNGER
-(21) PUMP SWITCH AND LIGHT
201 PROBE SWITCH AND LIGHT
(191 HEAT SWITCH AND LIGHT
•(18) FAN SWITCH AND LIGHT
1171 VARIABLE TRANSFORMER
CONTROL
(151 TIMER SYSTEM
'1141 POWER CORD (110 V) (16) LEVELING SCREW
Figure 5. Front panel of meter box.
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Dual Manometer
Visually check the pitot and orifice manometer lines. They should be free of
fluid. Check for leaks, especially around the fluid-level plunger (22) and drain
screws (23) shown in Figure 5. Replace the fluid-level plunger or O-rings, if
necessary. Wipe the dual manometer (1) clean. The back can be cleaned with
compressed air or the device can be removed from the box and wiped clean. If
the dual manometer is unusually dirty, clean as recommended by the manufacturer.
Replace the red manometer fluid, if it is faded. Manometer fluids are color-coded:
red is used for the pitot tube manometer and yellow for the orifice manometer (or
a similar combination) for ease of reading in the field.
After making sure that the manometer ports (2) are open and the manometer
lines connected, level the manometer and check the fluid level. The manometer
can be filled with fluid by removing the screw (3) on the left side. When the mano-
meter is zeroed, the fluid-level plunger should have about 1/4- to 1/2-inch travel
inward.
Pitot-Tube Lines
Blow through the pitot-tube quick connects (9) to check for obstructions.
The sealing balls in these quick connects should be removed to allow for free move-
ment of air. The pitot-tube manometer should respond.
Solenoid Valve
Plug the meter-box power cord into a 110-volt outlet. The power indicator
light (12) should go on and a click should be heard. The click is the sound of the
solenoid valves moving into the position shown in Figure 6. If the clicking sound
does not occur, check the power source, plug, power cord and connections, bulb,
and solenoid valve.
The valve switch (4), shown in Figure 5, operates the solenoid valve
assembly, which contains three 2-way solenoid valves (Figure 6). Two are
usually open and one is closed. When the valve switch is turned on, the two open
valves close and the flow into the manometer is blocked and the closed solenoid
valve opens to allow the pressure to equalize. This allows the manometer to be
zeroed while the pump is running.
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TO PUMP SWITCH
SPOT SWITCH
SOLENOID VALVES
NORMALLY OPEN
NORMALLY CLOSED
NORMALLY OPEN
TO MANOMETER
Figure 6. Solenoid assembly diagram.
The solenoid assembly operates only on the orifice manometer. To zero the
pitot tube manometer, the pitot tube lines can be disconnected at the quick connects
on the meter box.
Lights and Switches
Turn the coarse-adjust valve (7) to the off position and open fully the fine-
adjust valve (6). Turn on all switches (18 through 21) to check the lights. The
heater light should not go on until the fan switch is also on. If any of the lights do
not function, check for defective parts, including switches, lights, fuses, and
wiring.
Orifice Meter Lines
Turn off all switches except the pump switch (21). Turn on the valve switch
(4) and carefully adjust the coarse-adjust and fine-adjust valves. The orifice meter
manometer should respond to valve controls. If no movement is observed, check
the solenoid valves or the orifice meter system.
Timer
Leaving the pump on, check the timer system (15), which should operate only
when the pump is on. Malfunction of the timer can be caused by decreased voltage
supply or a worn synchronous motor. The timer has different cams for various
time periods or cycles, but the most commonly used is 5 minutes. Check the
459-345 O - 72 - 3
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timing for at least two cycles. The buzzer and timer light (13) should go on at the
end of the specified cycle. The duration of the buzz can be regulated by adjusting
the notch on the timer. Turn the pump off.
Amphenol Outlet and Variable Transformer
Check the Amphenol outlet with a voltmeter or check light by connecting the
leads to the different terminals (Figure 7). When connected across the variable
transformer, the voltage meter or check light should respond correspondingly.
^^5
BUZZER TIMER
PILOT LIGHT
PILOT LIGHT
TO
MANOMETER
ZERO
Figure 7. Meter box wiring diagram.
Vacuum System
Insert a plugged male quick connect into the sample port (10), shown in
Figure 5. Make sure that the valve switch (4) is off and then activate the pump.
Turn the coarse-adjust valve to the on position and close fully the fine-adjust valve.
The vacuum gauge (8) should read about 27 inches of mercury for a barometric
pressure of 30 inches of mercury. Check the leakage rate using the reading on the
dry gas meter (5) and a watch. If leakage exceeds 0. 02 cubic foot per minute,
find and correct the leak or leaks. Parts to check are the pump, vacuum gauge,
metering valves, and pipes.
Calibration
After all systems are functioning properly, calibrate the dry gas meter (5)
shown in Figure 5 and the orifice meter (24) shown in Figure 4 according to the
procedure in the Calibration section.
A sample check list and a calibration and calculation sheet are shown in
Figures 8 and 9. For recording purposes, the meter box should be numbered.
10
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Date Box No. Dry gas meter No.
Pump oil and filter
Quick connects
Dry-gas meter thermometers
Dual manometer system
Pi tot-tube lines
Solenoid valve
Lights and switches.
Orifice-meter lines.
Timer
Amphenol outlet.
Variable transformer.
Vacuum system
Metering valve _
Vacuum gauge
Leak check at inches of mercury - leakage =
Calibration (orifice and meter)
General remarks
Initial each item when checked and write in any remarks.
Figure 8- Suggested meter box assembly check list.
SAMPLE BOX ASSEMBLY
Ice Bath
Fill the ice bath (4) with water and check for leaks (Figure 10).
Electrical System
Using an Amphenol adapter (Figure 11), plug into a 110-volt source. The fan
and heater should go on. Failure to operate may be caused by a faulty electrical
source, a poor connection, a defective fan, or a defective heating element. The
11
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Date.
Barometric pressure,
in. Hg
Box No..
Dry gas meter No.
Orifice
manometer
setting,
AH,
in. HgO
0.5
1.0
2.0
4.0
6.0
8.0
Gas volume
wet test
meter
Vw,
ft3
5
5
10
10
10
10
Gas volume
dry gas
meter
vd>
ft3
Temperature
Wet test
Meter
tw»
°F
Dry gas meter
Inlet
tdi>
°F
Outlet
tdo>
°F
Average
td.
°F
Time
e,
min
Average
Y
AH@
Calculations
AH
0.5
1.0
2.0
4.0
6.0
8.0
An
13.6
0.0368
0.0737
0.147
0.294
0.431
0.588
Y
Vw Pb (td + 460)
(.ij \ / \
r\. . An \ /j. , /t rr\ \
Pb 13.6/ ( w 4CO/
AH@
0.0317 AH f(tw + 460) el 2
Pb (^ + 460) |_ Vw J
Y = Ratio of accuracy of wet test meter to dry test meter. Tolerance = ± 0.01
AH@ = Orifice pressure differential that gives 0.75 cfm of air at 70° F and 29.92
inches of mercury, in. H20. Tolerance - ± 0.15
Figure 9. Suggested orifice and dry gas meter calibration and calculation form.
wiring diagram is shown in Figure 12. Check thermostat operation by inserting a
dial thermometer in the heated section of the box. The temperature will generally
fluctuate 20 to 30° about the average after it stabilizes. The usual setting is 250° F,
but the thermostat can be adjusted to the setting desired.
Check the probe heater plug with a voltmeter or with a 110-volt check light.
12
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(1) THERMOSTAT
(2) AMPHENOL
CONNECTOR
(3) PROBE PLUG
(4) ICE BATH
Figure 10. Sample box.
110-V PLUG
Figure 11. Amphenol adaptor.
A sample check list is shown in Figure 13. Again, for recording purposes,
the box should be numbered. At least two sets of the sample-box assembly, includ-
ing the glassware for each meter box, should be on hand for a stack test and pre-
ferably more, depending on the number of runs required in a day. The availability
of several sets increases efficiency during the test since the sample train can be
cleaned while the second run is being made or the trains can be cleaned after all
runs have been completed.
13
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THERMOSTAT
AMPHENOL CONNECTOR
Figure 12. Amphenol wiring diagram..
Date
Box No.
Ice bath
Electrical system
Heater
Blower
Probe receptacle
Thermostat
Setting for average temperature of °F
Temperature variation °F ± °F
General remarks.
no-v PLUG
Initial each item when checked and write in any remarks.
Figure 13. Suggested sample box check list.
14
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POLLUTANT COLLECTOR
Glass Parts
Wipe the grease from the joints of the cyclone (1) and flask (Z), filter holder
(4), glass connectors (5), and impingers (3), shown in Figure 14. Wash with glass
cleaning detergent. For hard-to-clean parts use dichromate sulfuric acid cleaning
solution. Rinse with distilled, deionized water, and then acetone; air dry.
Reassemble the impinger portions using a thin coat of acetone-insoluble silicone
stopcock grease on the upper half of the taper joints (Figure 15). Cover all exposed
openings to avoid contamination.
HEATED AREA
(4) FILTER HOLDER
rx
(5) GLASS CONNECTORS
ICE BATH
Figure 14. Sample box glassware assembly.
Glass Frit
If the glass frit (7), shown in Figure 16, is dirty, place it in boiling, concen-
trated HC1 for 0. 5 hour. Rinse with distilled, deionized water, and then acetone;
air dry. If the frit still does not appear clean, boil for 2 hours in concentrated
H2SO4 plus a few drops of sodium or potassium nitrate. Rinse well with distilled,
15
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LUBRICATE
INDICATED AREA'
GLASS.FIBER FILTER
(6) BACK HALF / \ (10) FRONT HALF
(7) GLASS FRIT (9) RUBBER GASKET
Figure 16. Glass filter holder assembly.
Figure 15. Impinger.
deionized water, and then acetone; air dry. This procedure should also be followed
with new frits. The filter-holder assembly is shown in Figure 16.
Assemble the filter holder and components for a pressure-drop check as
shown in Figure 17 (see dry gas meter and orifice meter under Calibration). Turn
the pump on and adjust flow on the orifice manometer to AH@. If the vacuum gauge
METER BOX
VACUUM GAUGE
INLET
FILTER HOLDER
„ _ UMBILICAL )
Figure 17. Glass frit pressure drop check.
16
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on the meter box reads higher than 2 inches of mercury, the frit either is too fine
and should be replaced or is dirty and should be cleaned and checked again.
Greenburg-Smith Impinger Orifice
Fill the Greenburg-Smith impinger tube with water. If the water does not
drain through the orifice in 6 to 8 seconds, it should be replaced. This is only
required for new impingers.
Filter-Holder Gasket
Clean the filter-holder gasket by washing. Rinse with distilled, deionized
water, and then acetone; air dry.
UMBILICAL CORD
Quick Connects
Wipe the vacuum line and pitot line (1-2) quick connects clean (Figure 18).
A drop of penetrating oil on each helps keep them in good working condition.
Thermometer
Check the dial thermometer (4). The temperature should check against room
temperature when a mercury-in-glass thermometer is used as the standard.
(1) VACUUM LINE
(2) PITOT LINE.
(3) AMPHENOL CONN
(5) CHECK VALVE
{2) PITOT LINE
(4) THERMOMETER
Figure 18. Umbilical cord.
17
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Electrical Lines
Check the electrical lines (3) for continuity using an ohrnmeter or a battery-
light system. Make sure that the leads are connected to the proper prongs. If
there is no continuity in any of the lines, check the Amphenol connections. If this
is not the problem, replace the cord.
Check Valve
Disconnect the joint at the check valve (5) and add a drop of lubricating oil on
the valve.
Vacuum and Pitot Lines
Test the vacuum line for leaks by blocking the inlet with the plugged ball joint.
Connect the line to the meter box and check for leakage as before. If leakage is
noted, check all connections first and then, if necessary, check the tubing. If the
cause is not readily identified, slightly pressurize the line and check for leaks
using soapy water.
Connect one end of the pitot-tube line to a 36-inch U-tube mercury manometer
or a similar device. Pull a vacuum of at least 10 inches, seal the tubing at the
pump end, and check for leaks by noting the mercury manometer. Do the same for
the other side. If leakage is noted, check the tubing the same way as for the
vacuum line.
A sample check list is shown in Figure 19. For recording purposes, the
umbilical cord should be numbered.
18
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Date Umbilical No.
Quick connects
Thermometer
Electrical check
Check valve
Leak test
Vacuum line_
Pi tot lines_
General remarks_
Initial each item when checked and write in any remarks.
Figure 19. Suggested umbilical cord check list.
19
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CALIBRATION
NOZZLE DIAMETER
Using a micrometer, measure the inside diameter of the nozzle to the nearest
0. 001 inch. Make 10 separate measurements using different diameters each time
and obtain the average of the measurements. The largest deviation from the average
should not exceed 0. 002 inch. If the nozzle is satisfactory, polish off the old
inscribed value or, if new, etch the value of the inside diameter on the outside of
the nozzle.
PITOT TUBE
Measure the velocity pressure, AP, at the same point within a cross section
of a straight run of ductwork (8 diameters downstream and 2 diameters upstream
from any point of disturbance) with a standard pitot tube and the S-type pitot tube
for the desired range of gas velocities. The S-type pitot should be calibrated twice,
reversing the direction of the legs during the second calibration. Make at least
three determinations for each direction. Determine the pitot tube coefficient for
each direction as:
AP(S)
Use only those pitot tubes in which the average coefficient, Cp, equals 0. 85 I 0. 02
in both directions, since the nomograph used with the sampling train is designed
for this number.
DRY GAS METER AND ORIFICE METER
Connect the components as shown in Figure 20. The wet test meter is a
1-cubic-foot-per-revolution meter with t l percent accuracy. Run the pump for
about 15 minutes with the orifice manometer set at about 0. 5 inch of water to allow
the pump to warm up and to permit the interior surface of the wet test meter to be
wetted. Then gather the information as requested on the data sheet in Figure 9.
Calculate y , the ratio of accuracy of the wet test meter to the dry test meter, and
AH@. If an average y of 1. 0 +_ 0. 01 is not obtained, the dry gas meter should be
21
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1
^""~~~--j
%*
^
o
• • • •
p
GLASS TUBE THERMOMETER
,'^
s
/
V
s
/\
UMBILICAL '
/
/
/
X
U-TUBE MANOMETER
WET TEST METER
METER BOX
Figure 20. Calibration setup.
adjusted until y meets the specification. This can be accomplished by removing
the plate on top of the gas meter and adjusting the linkages.
Since the nomograph is designed for a AH@ of 1. 84 inches of water, a value
within 0. 25 inch of 1. 84 inches of water is desirable. If a value in this range is not
obtained, the orifice opening should be adjusted or the orifice replaced. In addition,
AH@ should not vary by more than 1 0. 15 over the range of operation of 0. 5 to 8
inches of water. If the AH@ is acceptable, record AH@ on the front of the meter
box.
HEATING PROBE CALIBRATION
If the probes are constructed as outlined in Reference 1, the graphs in
Figure 21 may be used to determine the probe heat setting required. If the probes
are not constructed as outlined or a calibration of the probes is required, similar
graphs can be constructed by using a heat source and measuring the inlet and outlet
temperatures at the various variable transformer settings while passing air through
at about 0. 75 cubic foot per minute.
22
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350
g- 300
UJ
jg 250
t—
£200
5
£ 150
UJ
^ 100
o
g 50
ce
Q_
0
— 3-ft PROBE (5-min WARMUP)
INLET, 250 °F
INLET AMBIENT,
80 °F
— INLET, 150 °F
20 40 60 80
POWERSTAT SETTING, %
350
£"300
ul
= 250
cc
150
o
cc
0.
— 4-ft, PROBE (10-min WARMUP) —
INLET, 250 °F
INLET, 150 °F
20 40 60 80
POWERSTAT SETTING,%
350
0^300
= 250
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FIELD OPERATION
Preparing the site so that the equipment can be positioned is frequently the
most difficult part of sampling. Scaffolding must occasionally be erected when the
sample port is not near a catwalk or other structure. The duorail has been found
to be a useful tool for sampling small-diameter stacks. At many sites the sampler
must use his ingenuity to get the sampling equipment to the sample port.
In selecting the site, the sampler should keep in mind that the distance from
the probe to the bottom of the sample box is about 13 inches. Although the equip-
ment was designed to fit into 2-1/2-inch holes, it has been found that 3-inch holes
allow easier entrance and removal without nicking the nozzle or picking up deposited
dust.
Because sampling approaches vary, the description of the operation of the
isokinetic sampling equipment will be confined to the use of the nomographs,
assembly of the components, and adjustment of the flow rate to isokinetic conditions
once the probe is positioned at the desired sampling point.
NOMOGRAPHS
The correction factor nomograph (Figure 22) and the operating nomograph
(Figure 23) have been designed for use with the sampling train as aids for rapid
isokinetic sampling rate adjustments and for selection of a convenient nozzle size.
To determine the correction factor, C, on the nomograph, the following information
is first required:
1. Percent moisture, % H2O. This maybe determined from a previous test
or presurvey, or before the sample run.
2. Orifice calibration factor, AH@. This is determined from the laboratory
calibration (see section on Calibration).
3. Meter temperature, Tm. Temperature at the meter rises above ambient
temperature because of the pump and can easily be estimated with experi-
ence. An estimate within 10° F (approximately +_ 1 percent error) is all
25
-------
% H,0
@
3 0
-
_ 2 5
—
— to
- 2__°___
~
— 1 5
__
_ 1 0
REF 2 ° ~
T
'm
150 —
~
--roJlS
A^ = rr — — — ~~ ~
"* STEP 1 —
—
50 —
0 —
—
—
-50 1
C _
B __ .
p: — 2 0 \Q —-*
^— 1 5 ^- — ~
" ~- — ~~ —
— c., 20
— -i_Q STEP 3 _
— 0 8
— 0 6 —
— 0 5 3° —
—
—
EXAMPLE AH^= 1 8 ~
@ 40
Tm = 100 °F _
% H2O ; 10 ~
pS/pm = 1 05 -
__
FIND C = 1 0 50—
PS/PM
1 2
—
1 1
~— 1 0
—
— 0 9
0 8
Figure 22. Nomograph for correction factor C.
that is necessary (an initial estimate of about 25° F above ambient tem-
perature has been used).
4. Stack pressure, Pg. This is measured before the sample run; or if the
sampling site is near the exit of the stack, atmospheric pressure is used.
5. Meter pressure, Pm. Same as atmospheric pressure.
To obtain correction factor, C (Figure 22):
1. Draw line from AH@ to Tm to obtain point "A" on reference line 1 (REF 1).
2. Draw line from point "A" to % H2O to obtain point "B" on reference line 2
(REF 2).
3. Draw line from point "B" to the calculated value
tion factor, C.
to obtain correc-
To select the nozzle size and to set the K-factor on the operating nomograph,
the following information is first required:
1. C factor. This is obtained from the correction-factor nomograph (Figure
22).
2. Stack temperature, Tg. This is determined in °F by a rough temperature
traverse to within 1_ 25° F before the sample run.
3. Average velocity pressure, AP. This is determined by a rough prelimi-
nary pitot traverse, using the average of minimum and maximum AP's in
26
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CORRECTION
FACTOR,
c PITOT READING,
ORIFICE READING,
A H
10—
9 —
7 —
6—
=
"=
"^
"=
4-=
^
^
—
n:
~
—
_
— —
—
i
—
0 9
0 8
0 7^
0 6-js
0 5-=j
-=
0 4 ~
jr
0 3-=
5
"^
0 2—
• —
—
-
0 1
REF A —
•S.REF B
"""•^
*^
2 0
— 1 5
-
"~ STEP 1
1 0
— 09
— 0 8
—
— 07
06
— 05
"** .^
~
—2500
-
—2000
-
— 1 500
^
—1000
"*
^- 800
: —
— 600.
— 500
— 400
«1F. ^00
— /oo ""
100
0
STACK
TEMPERATURE,
Ts
SLIDING
SCALE
CUT ALONG LINES
AP
K FACTOR 0001-^
^'"fP
•s^^
' ^Xx^
STEP 2 ^'
AH: m. H,O
C = dimensionless
-
0002J
=
o ooa-r
0 004-5
— ^
PROBE ° 005-=
TIP DIAMETER, ~
D 0 006-^
'^.•^,
•?-^.2.
001 —
; -
3 ~
E_0 8 0 02-=
= _=
— 07 0 03-5
— —
0 04-^
— 0 6 =
= 0 05-=
i" o 06-g
^— 0 5 — 3
E ° 08I3
5~ 0 2-^
=_0 4 -
E ° 2~E
^. —
- 0 3-=
~ — ~
— 03 —
- 3 0 4-=
r^'S"^0'!
i o-**!
— 0 2 ° 6™=
I
- " =
_ 2 0-^
3 o3
— 4 0— =
0 1 5 OMI
— U 1 —
6 0"—
8 0-Z
1 0 0—
K r dimensionless
D - m.
EXAMPLE C : 1 0
Tg .- 300 °F
AP= 0 5 in. H2O
D : 0 250 m., 0 375 in.
Figure 23. Use of the nomograph in selecting nozzle size and setting K factor.
inches of water.
4. Exact available nozzle sizes, D. This is obtained from calibration of
available nozzles.
To select the nozzle size and to set the K-factor pivot point, use the following
procedure (Figure 23):
27
-------
1. Set correction factor, C, on sliding scale to the reference mark, "A. "
2. Align Ts with average AP, note probe tip diameter on D scale, and select
exact nozzle size closest to it.
3. Align Ts with exact nozzle size selected and obtain a value on the AP scale.
4. Align the AP value with reference mark, "B", on AH scale, and set the K-
factor pivot point.
To obtain the orifice meter setting, AH, for isokinetic conditions after the K-
factor pivot point has been set, use the following procedure (Figure 24):
1. Position the pitobe nozzle at the sampling point.
2. Read the pitot tube AP.
3. Align the AP through the K-factor pivot point.
4. Obtain AH and adjust metering valves.
The nomograph assumes the following once the K-factor pivot point is set:
1. Ts does not change more than 25° for Ts < 1000° F or 50° for Ts > 1000°
F.
2. D is not changed during the test.
3. Tm •was estimated correctly and does not vary more than 10°.
4. Percent H2O remains constant, within +. 1- 0%.
5. Ps and Pm remain constant, within +_ 1. 0%.
SAMPLE COLLECTION ASSEMBLY
Pitobe Assembly
After selecting a suitable probe length, remove the cover from the nozzle side
of the stainless steel union on the probe sheath. Ensure that the probe side of the
union contains a stainless steel back ferrule inserted backwards and a Viton A O-
ring, and that the nozzle side has a stainless steel front and back ferrule (Figure
2). If the stack temperature is above 500° F, replace the Viton A O-ring with
asbestos cord.
28
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CORRECTION
FACTOR,
C
ORIFICE READING,
AH
1 0—«
9 3
8— 1
7-J3 REF. A —
6— J
^
~
=
=
~
2-^
—
t
0.9—
0 8 —
0 7 —
0.6-—!
•-REF. B
^XAIVlpl r- '*
0.5-J
0.4^
0.3-=
0 2—
~
—
— 2.0
— 1.5
— 1.0
— 09
H.0.8
— 0.7
— 06
— 05
-•^
—2500
—2000
—
— 1500
-—1000
~ 800
1^,600
TT^00*^*^
H 300
— ZOO
« 1 00
~— 0
STACK
TEMPERATURE,
TS
SLIDING
SCALE
CUT ALONG LINES
PITOT READING,
AP
K FACTOR o.ooi —
^.^PIVOT POINT
""~~"''"V^»,
—
0.002-5
•1
0 003-S
0 004-5
PROBE 0.005-1
TIP DIAMETER, H
Q 0.006-^
0.01 *^
^
E ;
T-° ' -^
1-0 8 0 02^
1_0 7 0 03-1
— 0 6 ~z
= 0 05_i
JT 0 06 -g
r o oe-^
^-04 -
5^.°^ 0 4-|
r "VC^«
- 0 7-5
I '-"-f
I 2 0-1
— 0 1 5 °-|
6.0^
a o^
1 0 0—
AH = in. H2O
C : dimensions
K r dimension less
D ; In.
EXAMPLE 1 AP : 0 5
Ah -- 1 2
EXAMPLE 2 AP : 0 6
AH = 1 53
Figure 24. Nomograph operation to obtain desired orifice meter settings.
Remove the cover from the shank end of the selected nozzle (obtained from the
nomograph), insert the nozzle in the probe sheath union, and finger tighten the
union. Avoid the use of wrenches as this would bind the ferrules to the nozzle
shank and could cause the glass probe to crack. Keep the nozzle tip and the ball
joint on the glass probe covered until the assembly of the equipment is complete
and sampling is about to begin. Mark the probe with heat-resistant tape or by
29
-------
some other method to denote the proper distance into the stack or duct for each
sampling point.
Attach a temperature probe to the metal sheath of the sampling probe so that
the sensor extends beyond the probe tip and does not touch any metal. Its position
should be about 1 inch from the pitot tube and probe nozzle to avoid interference
with the gas flow.
Sample Box Assembly
Place the tared filter in the filter holder and record the filter number on the
data sheet. Tighten the clamps around the filter holder to prevent leakage around
the rubber gasket.
Assemble the collection system, as shown in Figure 1 or as dictated by the
requirements of the test, using a very light coat of silicone grease (acetone non-
reactive) on the lower half of all the male ball joints (Figure 15).
LEAK TEST
Place the meter box in a convenient position up to 200 feet from the test port
and connect the vacuum line of the umbilical cord to the inlet of the meter box and
the outlet of the last Greenburg-Smith impinger of the sample box. Check the ball
joint stopper in the inlet to the cyclone for possible leakage. Turn the coarse-
adjust valve on the meter box to the off position and open the fine-adjust valve
slowly until fully opened. Partially close the fine-ad just valve until the vacuum
gauge reads 10 inches of mercury; then check the dry gas meter for flow. If the
flow through the dry gas meter exceeds 0. 02 cubic foot per minute at 10 inches of
mercury gauge pressure, the leak or leaks must be found and corrected.
When the check is complete, first remove the plug from the inlet to the
cyclone, and immediately turn off the vacuum pump. This prevents water from the
impingers from being forced backward into the filter and cyclone.
FINAL SAMPLING TRAIN ASSEMBLY
Remove the cover from the ball joint on the probe, lightly grease the lower
half of the ball joint with silicone grease (Figure 15), and connect the probe. Make
sure that the rubber stopper is snug in the opening in the sample box. Secure the
probe by tightening the probe holding clamps.
30
-------
Make all necessary electrical and pitot-tube line connections. Set the vari-
able transformer on the meter box so that the desired probe temperature is
obtained (use Figure 21 as a guide). Set the thermostat on the sample box at 250°
F or at the desired temperature. Turn on the heater, blower, and probe switches
on the meter box. Allow the sample box and probe to heat for at least 15 minutes
before starting the test and make periodic checks and adjustments to assure the
desired sample box temperature.
Fill the impinger section of the sample box with ice and a little water. Add
ice periodically during testing to maintain the temperature of the gas leaving the
last impinger at less than 70° F.
SAMPLE RUN
Record all necessary initial data such as that shown at the top of the sample
data sheet in Figure 25, including the initial dry gas meter reading. Turn off the
coarse-adjust valve on the meter box, fully open the fine-adjust valve, and set the
timer cam to zero. Remove the cover from the nozzle tip and place the pitobe at
the first sampling point. Record the clock time, read AP on the pitot tube mano-
meter, and determine AH from the nomograph as shown previously.
Turn the pump on and set AH on the meter box first by adjusting the coarse-
adjust valve and then the fine-adjust valve.
The sample run plan should consider the number of traverse points and the
sampling time at each point. A good rule of thumb to follow is to collect a weight
of particulate matter equal to about 20 percent of the filter weight. The upper
limit is usually set by the pressure drop across the filter and the amount of con-
densate the impingers can hold. Generally the length of sampling time at each
traverse point is 5 or 10 minutes.
During the sample traverse the pitobe is moved from point to point without
turning the pump off except when changing ports. The AP should be monitored and
adjustments made on the orifice meter with the aid of the nomograph when neces-
sary. Besides the regular time interval recordings, a set of readings should be
recorded when the AP changes by more than 20 percent.
31
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SHUTDOWN
When testing has been completed, turn off the vacuum pump, remove the
pitobe from the stack, and take a final set of readings. Turn off the heater, blower,
and probe heat switches and remove the probe from the sampling port. Cover the
nozzle tip as soon as it is cool enough in order to avoid contamination or loss of
sample. Disconnect the probe from the cyclone inlet and cover both the end of the
probe and the inlet to the cyclone. Disconnect the umbilical cord from the sample
box and cover the last impinger outlet. The probe and sample box are then ready
for cleanup and the analytical procedure.
33
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REFERENCES
1. Martin, Robert M. Construction Details of Isokinetic Source-Sampling
Equipment. Air Pollution Control Office, Environmental Protection Agency,
Research Triangle Park, N. C. Publication No. APTD-0581. April 1971.
2. Smith, Walter S. et al. Stack Gas Sampling Improved and Simplified with New
Equipment. Presented at 60th Annual Meeting of Air Poll. Control Assoc. ,
Cleveland, Ohio. June 11-16, 1967.
35
U. S. GOVERNMENT PRINTING OFFICE : 1972 O - 549-345
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