RECOMMENDED HEAVY DUTY DIESEL
INSTRUMENTATION AND TEST PROCEDURES
To the User: This recommended practice reflects
the experience of industry and government to date.
This practice is subject to change as new data
are gathered and experience is obtained.
Environmental Protection Agency
Office of Air and Waste Management
Office of Mobile Source Air Pollution Control
Emission Control Technology Division
Standards Development and Support Branch
July 10, 1975
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I. Instrumentation
A. Schematic Drawing.
(1) Figure IA-1 is a schematic drawing of the exhaust gas
sampling and analytical system. All components or parts
of components that are wetted by the sample or corrosive
calibration gases should be either chemically clean
stainless steel or teflon. Use of hydrocarbon deriva-
tives such as Buna-N for packings, -seals, diaphrams or
any other device that may come in contact with the sample
or span gas is not recommended. The use of "gauge savers
or protectors" with non-reactive diaphrams is recommended.
B. System Components.
The following is a list of components shown in Fig. IA-1
by numeric identifier. Pressure ranges and accuracies when
given are suggested values. Any component indicated as being
heated means maintaining that component at 190°C; +10°C, -5°-C
(375°F;
(1) Filters.
(a) Fl - Particulate filter.
(b) F2''- Particulate filter.
(c) F3 - Heated particulate filter.
(2) Flowmeters FL1 and FL2 to indicate sample flow rates
through the CO and CC- analyzers.
(3) Gauges (0-15" H_0) Gl and G2 to measure input pressure to
CO and CO analyzers and any unwanted changes in down-
stream restrictions.
(4) Pressure gauges.
(a) PI - bypass pressure (0-20 psig).
(b) P2, P3, P4, and P5 - sample or span pressure at
inlet to flow control values (0-10 psig) .
(5) Refrigerator or ice bath water traps (Temperature: 0-3°C,
32-37°F) REF1 and REF2 to remove water vapor from the
sample. May include suitable method for draining trap.
(6) Regulators.
(a) Rl, R3, R4, and R6 - line pressure regulators to
control span pressure at inlet to flow control
valves (0-10 psig + 2" HO) .
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L«gend
Span and Span and
Zero Giset Zero Qatet
PirtlcuUU ruur
FlowmotM
Backprttturo Regulator with
Internal Control Loop Shown
Lin* PrtMura lUgulltor wllh
Inurnal Control Loop Shown
Ball Valva or Equlvalvnl
(Oarhtnd Leg tndlcaia* Common Port)
Flow Control or N««dl* Valvo
Plug Valv* or Equivalent
(Center Port la Common)
Healed Area ,
Fig. I A-l
Heavy Duty Exhaust Gas
Sampling and Analytical Train
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(7) Valves.
(a) VI, V7, V8, and V14 - selector valves to select zero
or calibration gases.
(b) V2 - Optional heated selector valve to purge sample
probe.
(c) V3 and V5 - Selector valves to select sample or span
gases.
(d) V4, V6, and V13 - flow control valves.
(e) V9 and V13 - heated selector valve to select sample
or span gases.
(f) V10 and V12 - heated flow control valves.
(g) Vll - Selector valve to select NOx or bypass mode in
the chemiluminescence analyzer.
(8) Pump - sample transfer pump to transport sample to
analyzers (1.5 CFM at free flow).
C. Component Description (exhaust gas sampling).
The following components are recommended for the exhaust
gas sampling system.
(1) Sampling Probe. The sample probe shall be a closed end,
stainless steel, multi-hole probe 1/4 inch outside
diameter extending at least 80% across the exhaust pipe.
There shall be a minimum of 3 ports in probe covering
approximately equal areas of the duct and oriented such
that they face into the exhaust stream. The orifice
should be sized such that each port has approximately the
same flow. The probe shall be located approximately
three to nine feet downstream from the exhaust manifold
outlet flange or turbocharger exit flange and this
position must be downstream of any exhaust emission
control device(s) (catalyst, etc.)-
(2) Sample transfer. The exhaust gas sample shall be trans-
ferred to the analytical instruments through a heated
filter and heated line by a hot pump. The heated line
shall be of stainless steel or teflon construction and
have an I.D. between .18 and .32 inches. The sample line
wall temperature must be maintained at 190°C; +10°C, -5°C
(375°F; +18°F, -9°F) with a maximum line length of 50 ft.
The sample pump shall be located as close as practical to
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the sample probe and the wetted surfaces of the pump must
be heated. The pump must be capable of transporting the
sample from the probe to the analyzers in 5 seconds or
less. The filter must also be heated.
D. Component Description (exhaust gas analysis system).
(1) Total hydrocarbon measurement (HC). The determination of
hydrocarbon concentrations, is to.be ascertained by a
heated flame ionization detector (FID). See the Appendix
for general design specifications.
(2) Oxides of Nitrogen Measurement (NOx). The concentration
of Oxides of Nitrogen (NO + N0_ = NOx) is to be determined
by a chemiluminescence analyzer in the (NOx) mode. This
requires the (NO ) in the sample to be converted to (NO)
by the converter before analyzing the sample in the
reaction chamber. See the Appendix for general design
specifications.
(3) Carbon Monoxide Measurement (CO). The carbon monoxide
concentration is to be determined by an NDIR analyzer.
See the Appendix for general design specifications. If
the turn down ratio of the analyzer is not great enough
for the desired application, a combination of two or more
separate instruments, two or more separate cells with one
amplifier, or a multi-cell analyzer may be used. Accomplish
this by adding a selector valve between flowmeter FL2 and
gauge G2 (See Fig. IA-1). All cell flow paths must be
parallel and must have a gauge G2 immediately upstream of
all detector cells. Vent all detector cells to atmospheric
pressure as shown in Fig. IA-1. If the cells are in
series optically as in some dual cell arrangements, the
cell not in use must be continuously purged with nitrogen
(N?) when analyzing a sample. Furthermore the purge
pressure at G2 should be approximately the same as the
sample pressure at G2 although the flow rate may be
somewhat lower.
(4) Carbon Dioxide Measurement (C0?). The carbon dioxide
concentration is to be determined by an NDIR analyzer.
See the Appendix for general design specifications.
E. Venting.
The method of disposing of the sample is not specified.
However, caution must be used in routing of the vent lines:
(1) Venting of the instruments, especially the NDIR analyzers,
must be such that the analyzer vent does not see a back
pressure caused by the proximity of other vents.
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(2) Pressure relief vents provided by some manufacturers of
regulators and located in the bonnet of the regulator
should be vented to the atmosphere.
II. Information.
The following information as applicable should be recorded for
each test.
A. Engine Description.
(1) Engine identification numbers.
(2) Date of manufacture.
(3) Number of hours of operation accumulated on engine.
(4) Engine family.
(5) Exhaust pipe diameters.
(6) Fuel injector type.
(7) Low idle rpm.
(8) Governed speed.
(9) Maximum power and torque speeds.
(10) Maximum horsepower and torque.
(11) Fuel consumption at maximum power and torque.
(12) Air aspiration system.
(13) Exhaust system back pressure.
(14) Air inlet restriction.
B. Test data.
(1) Test number.
(2) Instrument operator.
(3) Engine operator.
(4) Date and time of day.
(5) Fuel identification, including H/C ratio.
(6) Ambient temperature in dynamometer testing room.
(7) Engine intake air temperature and humidity for each mode.
Air temperature and humidity measurements should be made
within 18 inches of the inlet for engine intake air.
Temperature and humidity measurement devices must respond
to 90% of a step change between 30 to 120 seconds.
(8) Barometric pressure.
(9) Observed engine torque for each mode.
(10) Ir-.t-J-.e air flow for each mode.
(11) Fuel flow and temperature for each mode.
(12) Sample line temperature. Line temperature shall be taken
at a minimum of three locations, two of which should be
the sample probe outlet and instrumentation inlet.
(13) Sample line residence time (Refer to Section IV).
(14) Date of most recent analytical assembly calibration.
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(15) All pertinent instrument information such as tuning-gain-
serial numbers-detector numbers-range.
(16) Recorder chart. Identify for each test mode: zero
traces for each range used-calibration or span traces for
each range used - emission concentration traces and
associated analyzer range(s) - start and finish of each
test.
(17) Record chart speed of recorder and date of last speed
calibration. The minimum chart speed allowed is .5
inches per minute.
(18) Record engine torque and engine r.p.ra. continuously on
the same chart.
III. Calibration and instrument checks.
A. Calibrate the analytical assembly including recorder chart
speeds at least once every 30 days. Use the same flow rate
and chart speed as when analyzing samples.
(1) Perform a pressure leak check per Section IV A.
(2) Adjust analyzers to optimize performance. See the
Appendix.
(3) Zero the hydrocarbon analyzer with zero grade air and the
carbon monoxide, carbon dioxide, and oxides of nitrogen
analyzers with zero grade nitrogen. The allowable zero
gas impurity concentrations should not exceed 0.1 p.p.m.
equivalent carbon response, 1 p.p.m. carbon monoxide, 400
p.p.m. carbon dioxide, and 0.1 p.p.m. nitric oxide.
(4) Calibration gas concentrations shall be determined within
+1.0% of the absolute value.
(5) Set the CO and CO^ analyzer gains to give the desired
range. Select desired attenuation scale of the HC
analyzer and adjust the electronic gain control to give
the desired full scale range. Select the desired scale
of the NOx analyzer and adjust the phototube high voltage
supp'ly or amplifier gain to give the desired range.
Normally, zero and gain adjustment should be performed on
the lowest anticipated range.
(6) Calibrate the HC analyzer per the Appendix.
(7) Calibrate the CO analyzer with carbon monoxide (nitrogen
diluent) gases and the CO„ analyzer with carbon dioxide
(nitrogen diluent) gases having nominal concentrations of
20, 30, 40, 50, 60, 70, 80, and 90 percent of full scale
of each range used.
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(8) Calibrate the NOx analyzer per the Appendix.
(9) Check NOx converter efficiency per the Appendix.
(10) Compare values obtained on all analyzers with previous
calibration curves. Any significant change reflects some
problem in the system.
B. Verifications and instrument checks sHould be performed in
accordance with Section IV on in-use system.
C. For the purposes of this section, the term "zero grade air"
includes artificial "air" consisting of a blend of nitrogen
and oxygen with oxygen concentrations between 20.0- and 22.0-
mole percent.
D. Calibrate the dynamometer test stand and other instruments for
measurement of power output and the fuel flow measurement •
instrumentation at least once every 180 days.
IV. Sampling procedures.
A. HC, CO, C09 and NOx measurements. Allow a minimum of 2 hours
warmup for the CO, C0_, HC, and NOx analyzers. (Power is
normally left on for the infrared, chemiluminescence, and FID
analyzers; but when not in use, the chopper motors of the
infrared analyzers are turned off and the phototube high
voltage supply of the chemiluminescence analyzer is placed in
the standby position. Also, leaving the flame and the oven
"on" in the FID leads to a more stable response.) The follow-
ing sequence of operations should be performed in conjunction
with each series of measurements:
(1) Replace or clean filters.
(2) After the filter(s) have been replaced or cleaned, check
the sampling system for any leaks that: could dilute the
exhaust gas. If during the test, the filters are replaced
or cleaned, a leak check must be performed after the test
is completed. This post test leak check must be performed
aft^r ha">2';p rhecl't F^O narlc. The pressure r-ldf. leal-'
check may be borrowed from the 30 day check of the system.
Check sample system leakage in the following manner:
(a) Vacuum Side
(A) Cap the probe or sample line at the probe
fitting.
(B) Measure the flow at the discharge of the pump.
(C) If the measured flow exceeds 2.0 cc/min, effect
repairs to the system.
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(b) Pressure side
(A) Vent the inlet of the pump to the atmosphere.
(B) Cap the sample line at the point the line
connects to the analysis train.
(C) Measure the flow at the inlet to the pump.
(D) If the measured flow exceeds 10.0 cc/min,
effect repairs to the system.
(E) All other pressure fittings may be checked by
using the bubble-check method. Various com-
mercial preparations are available for this
purpose. Fitting leakage should be corrected.
(3) Introduce the zero grade gases at the same flow rates
used to analyze the test samples and zero the analyzers
on the lowest anticipated range that may be used during
the test. Record a stable zero for each anticipated
range that may be used during the test prior to the test.
Record these zero values for each analyzer.
(4) Introduce span gases to the instruments under the same
flow conditions as were used for the zero gases. Adjust
the instrument gains on the lowest range to be used to
give the desired value. Span gases should have a concen-
tration greater than 65% of full-scale for each range
used. A significant shift in gain setting indicates an
instrument or system problem. If necessary, recheck
calibration and span-gas concentration-label. Record the
response to the span-gas and the span-gas concentration
for each anticipated range that may be used during the
test prior to the test. Record these values for each
analyzer.
(5) Recheck zeros; repeat the procedure in subparagraphs (3)
and (4) of this paragraph, if required.
(6) Check sample line temperature and sample residence time.
To check f=,?Tple residence time.:
(a) Introduce HC span gas into sampling system at sample
inlet and simultaneously start timer.
(b) When HC instrument indication is 15 percent of full-
scale, stop timer.
(c) If elapsed time is more than 5.0 seconds, make
necessary adjustments.
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(d) Repeat (a) through (c) with CO, CO , and NOx instru-
ments and span gases.
(7) Sample residence-time may be used from previous tests if
all of the following conditions are met:
(a) The same size and type of pump is used.
(b) The sample line I.D. is the-same and the length is
equal to or shorter than the tested line.
(c) The sample line temperature is the same (+ 5°C,
9°F).
(d) Pressure gauges PI, P2, P3, P4, and P5 read the same
pressure (+ 15% of original value).
(8) Check instrument flow rates and pressures.
(9) Operate the engine in accordance with Section V. Measure
HC, CO, CO-, and NOx volume concentration in the exhaust
sample. Record data specified in Section II. Should the
emission volume concentration exceed 95% of full-scale
value for non linear instruments (100% of full-scale
value for linear instruments) or respond less than 20% of
full-scale value, (for all instruments) the next higher
or lower analyzer range should be used per the Appendix.
Note: the lower limit (20% of full-scale) would not appjy
when the full-scale value is 120 ppm (or ppmC) or less.
Should the fuel flow instrument read below 20% of full-
scale value, a smaller flow measurement unit must be used
unless the option in the Appendix is desired.
(10) Each range that may be used during a particular mode must
have the zero response and span response recorded prior
to the emission measurement at least once every 30 minutes.
Only the range(s) used to measure emissions need be
checked. At the completion of the test the zero response
and span response for each range that was used during
test should be recorded. If the difference between the
span-gas response and the zero-gas response has changed
more than +2.0 percent of full scale based on the 30.
n:Jr.'iL«j check., tl.v. cect r-!:ould be /.^ixn aiu-;T ...i^irL'.L.c'nL
maintenance. In addition the test should be rerun if the
zero response changes more than +6.0 percent of full
scale. If the zero response has changed less than +2.0
percent, the pre-test zero response is to be used.
However, if the response change is between + 2.0 and ;+
6.0 percent of full scale, a zero response correction
based on an interpolation which is linear with time is
acceptable.
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B. Sample system contamination.
(1) Care shall be taken to avoid loading of the sampling
system with raw fuel discharged during engine starting.
(2) When the sample probe is in the exhaust stream and
sampling is not in process, a back purge with air or an
inert gas may be necessary to protect the probe and
sample line from particulate .buildup which could affect
hydrocarbon readings. Check sample line for contamina-
tion before and after each test. Use the following
procedure to check the sample line:
(a) With the HC analyzer calibrated on the lowest range
to be used for the test, and the sample line at the
required temperature, check the sample-line hangup
at least 45 minutes prior to the start of the test.
Introduce an HC zero-gas into the sample probe. If
the instrument reading increases from the calibrated-
zero reading by more than 5.0 percent of full-scale,
the sample-line shall be purged or cleaned as required
to bring the instrument reading within limits.
(b) Within 10 minutes after the completion of the post-
test zero and span check of the analyzers, check the
sample-line hangup. Remove the probe from exhaust
pipe. Turn the engine off. Introduce an HC zero-
gas into the sample probe. If the instrument reading
increases from the calibrated-zero reading by more
than 5.0 percent of full scale, rerun the test.
V, Test run.
A. The temperature of the air supplied to the engine shall be
between 68°F and 86°F. The fuel temperature at the pump inlet
shall be 100°F, + 10°F. The observed barometric pressure
shall be between 28.5 inches and 31 inches Hg. Higher air
temperature or lower barometric pressure may be used, if
desired, but no allowance shall be made for increased emissions
because of such conditions.
B. Tho governor and fuel system shall h?.ve been adjusted to
provide engine performance at the levels specified by the
engine manufacturer for maximum rated horsepower and maximum
rated torque.
C. The following steps shall be taken for each test:
(1) Install instrumentation and sample probes as required.
(2) Observe sampling procedure in Section IV.
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CS) Start cooling system.
(4) Start the engine, warm it up and precondition it by
running it at rated speed and maximum horsepower for 10
minutes or until all temperature and pressures have
reached equilibrium.
(5) Determine by experimentation the maximum torque at rated
speed and intermediate speed to calculate the torque
values for specified test modes.
(6) Start the test sequence. Operate the engine for 10
minutes in each mode, completing engine speed and load
changes in the first minute. If a delay of more than 10
minutes occurs between the end of one mode and the start
of the next mode, discontinue the sequence and repeat the
test from Mode No. 1. Record the response of the analyzers
on a strip chart recorder for the full 10 minutes with
exhaust gas flowing through the analyzers at least during
the last 5 minutes. Record the engine speed and load,
intake air temperature and restriction, exhaust back
pressure, fuel flow and air or exhaust flow during the
last 5 minutes of each mode, making certain that the
speed and load requirements are met during the last
minute of each mode. Fuel flow during idle or 2 percent
load conditions may be determined just prior to or
immediately following the dynamometer sequence, if longer
times are required for accurate measurements.
(7) Read and record any additonal data as required for
Section II.
*
(8) Check analyzer zero and spans as required for Section IV.
(9) Backflush condensate trap and replace filters as required,
per Section IV.
V I . Chart reading .
A. Locate the last 60 seconds of each mode. Integrate the chart
reading to determine the percent of full scale deflection of
the CO., CO, HC, n--' NOx annlvzevs d'irjrir this 60 ? --conds.
(1) If the excursion from a straight line (other than instru-
ment noise) during this 60 seconds is less than 1 percent
of full scale, a simple average may be used to determine
analyzer deflection.
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B. Determine the concentration of the CO , CO, HC, and NO during
the last 60 seconds of each mode from the percent of full
scale analyzer deflection, span gas response, range correction
factor, linearity curves, and other calibration data.
VII. Calculations.
The final reported test results should be derived through the
following steps.
A. Determine the exhaust species volume concentration for each
mode per Section VI.
B. Convert the measured hydrocarbon (HC) volume concentrations to
dry basis per the following:
wet-concentrations = KW x dry-concentrations
where:
1 +'
DCO
DCO\
2Y /
&\
DCO
10
DCO
10
?) (• • T)
CX =
DCO =
DC02 =
WHC =
K
atomic hydrogen/carbon ratio
CO volume concentration in exhaust, ppm (dry)
C02 volume concentration in exhaust, % (dry)
HC volume Concentration in exhaust, ppm C (wet)
Water - gas equilibrium constant =3.5
^ = H2° y°J-ul-e <--.oncentraticn of intake aii , % (Pee the Appendix)
0 = fuel-air ratio (actual)/fuel-air ratio (stoichiometric)
(See the Appendix)
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C. Multiply the dry nitric oxide volume concentrations by
the following humidity correction factor:
1+A (H-75) + B (T-85)
where:
A = 0.044 (f/a) - 0.0038
B = -0.116 (f/a) + 0.0053
H = humidity of the inlet air in grains of water per pound of
dry air.
T = Temperature of inlet air °F.
D. Compute the dry (f/a) as follows:
(l +^\
^___ 4.77\ 4/ (f/a)stoich
(f/a) =
i / DCO \ / DHC \ ot / DHC \
I ~U (10)6 )1x 106 J * ( ' XC10)6 I
.75 PC.
where the stochiometric (f/a) is
M + o^M,
(f/a)stoch =
138.:
OC = atomic hydrogen/carbon ratio
M = Molecular weight of carbon
L*
M^ = Molecular weight of hydrogen
DCO = Dry volume concentration of CO in exhaust, ppm (dry)
DCO,, = Dry volume concentration of CO in exhaust, % (dry)
DHC = Dry volume concentration of HC in exhaust computed from the
wet volume concentration in ppm C by:
dry concentration = wet concentration/IC
w
K = water-gas equilibrium constant = 3.5
X = DC02/102 + DCO/106 + DHC/106
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Compare the calculated dry (f/a) to the measured fuel and air flow.
For a valid test the emission calculated (f/a) must agree within 10% of
the measured (f/a) for each mode (idle and 2% modes excepted).
E. Calculate the mass emissions of each species in grams per hour
for each mode as follows:
(1) HC grams/hr = WR(, =
(2) CO grams/hr = WCQ
io4 "f •
DCO DHC
10* 2 IO4
MCO 104H£
(M + o4 Mj ) • / DCO
° Uo4 +
DHC\
DC°2 + io4/
^n DKNO u
^°2 4 wf
10
= (M ^ M ) /DCO
C -1 » 11 [ H
\1(T
DHC \
h DCO ^ \
* io 1
(3) NOx grams/hr =
where:
o4 = atomic hydrogen/carbon ratio
DCO = CO volume concentration in exhaust, ppm (dry)
DCO- = C0_ volume concentration in exhaust, % (dry)
DHC = HC volume carbon concentration in exhaust, ppm C (dry)
DKNO = NO volume concentration in exhaust, in ppm (dry and humidity
corrected)
HC = Molecular v.'eight. of the carbon
(M ^O^MU) = mean molecular weight of the fuel/carbon atom
MCO = Molecular weight of CO
M = Molecular weight of hydrogen
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= Molecular weight of nitrogen dioxide (N0_)
W.,. = Mass rate of CO in exhaust, grams /hr.
CO
Wf = Mass flow rate of fuel used in the engine, grams/hr.
= (453.59) x (Wf Ibs/hr.)
W = Mass rate of HC in exhaust, grams/hr.
HC
W _ = Mass rate of NOx in exhaust, grams/hr.
F. Weight the values of BHP, WRC, VCQ, WN()X, and Wf
(1) Average the values obtained from the three idle modes and
multiply this value by (.02V 3). Substitute this value
for each of the three idle modes.
(2) Weight the remaining modes by multiplying the values by
0.08.
G. Calculate the brake specific emission for each test by summing
the weighted values (BHP, W , Wp_, and W ) from each mode
f 11 rid L»U
as follows:
BSHC
= I weighted WHC
^weighted BHP
BSCO = ^weighted WCQ
£weighted BHP
BSNOx = Eweighted WH()X
^weighted BHP
H. Calculate the brake specific fuel consumption (BSFC) from the
non-weighted BHP and W- values for each mode (except the idle
mode) as follows:
W.
BSFC =
Corrected BHP
(1, Coveted BHP . BHp(|yi)
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where:
BARO = Barometric pressure (in Hg A)
Wf » Fuel flow (Ib/hr)
T = Temperature of inlet air, °F
I. Calculate the weighted brake specific fuel consumption (WBSFC)
for each test sequence by summing the weighted values (Wf and
corrected BHP) from each mode as follows:
WBSFC = <- wei£hted Wf
V weighted corrected BHP
Wf = Fuel flow in Ib/hr
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Appendix
General Design Specifications for Heavy Duty Vehicle Analytical
Instruments..
I. Measurement accuracy:
A, All emission analyzers: Listed are suggested ranges for all
emission analyzers. Select the appropriate ranges and number of ranges.
for each analyzer. The analyzers must operate between 20 percent and
95 percent of full-scale value for non-linear instruments (20 to 100
percent for linear analyzers) during the measurement of the emissions
for each, mode. The exceptions to the lower limit of this operating
rule are;
(1) The analyzer response may be less than 20 percent
of full-scale if the full-scale value is 120 ppm (or ppm
C) or less.
(2) The analyzers response may be less than 20 percent of •
full-scale if the emissions from the engine are irratic and
the integrated chart-deflection value is greater than 20
percent of full-scale.
C3) The analyzer response may be less than 20 percent of
full-scale during the initial part of the CT mode provided
that the integrated chart-deflection value is greater than
20 percent of full-scale.
The magnitude of full-scale value of the .suggested ranges
may vary somewhat to suit instrument characteristics or to facilitate
data collection. .
Suggested Ranges
Instrument Accuracy
0-10. ppm or ppm C
0-40. ppm or ppm C
0-100. ppm or ppm C
0-400. ppm or ppm C
0-1000. ppm or ppm C
0-4000. ppm or ppm C
0-10000', ppm or ppm C
0-40000. ppm or ppm C
0-10.00 percent
0-15.00 percent
0-20.00 percent
5 percent of full-scale
2 percent of full-scale
1 percent of full-scale
1 percent of full-scale
1 percent of full-scale
1 percent of full-scale
1 percent of full-scale
1 percent of full-scale
1 percent of full-scale
1 percent of full-scale
1 percent of full-scale
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B. The dynamometer test stand and other instruments for measurement
of power output shall be accurate to within + 2 percent of full-scale
at all power settings.
C. The fuel flow measurement instrumentation shall have a minimum
accuracy of 1 percent of full-scale for each range used. Fuel flow
measurements may not be used as official values if the readings are
below 20 percent of full scale value unless the point accuracy has
an error of less than 5 percent.
II. NDIR instruments: Nondispersive infrared (NDIR) analyzers shall
be used for the continuous monitoring of carbon monoxide and carbon
dioxide.
A. Analyzer description: The NDIR instruments operate on the
principle of differential energy absorption from parallel beams of
infrared energy. The energy is transmitted to a differential detector
through parallel cells, one containing a reference gas, and the other,
sample gas. The detector, charged with the component to be measured,
transduces the optical signal to an . electrical signal. The electrical
signal thus generated is amplified and continuously recorded.
B. Analyzer specification:
Response time (pnuematic^r-lS percent of full-scale in 0.5
seconds or less.
Response time (electrical)—95 percent of full-scale in
0.5 seconds or less.
Noise—H-l percent of full scale on most sensitive range.
Repeatability—KL^ percent of full scale.
Zero drift—Less than +1 percent of full-scale in 2 hours
on all ranges.
Span drift—Less than +1 percent of full-scale in 2 hours
on all ranges.
Cell temperature—Minimum 50°C maintained within + 2°C.
C. Cell length: All NDIR instruments shall be equipped with
cells of sufficient length to accurately measure the exhaust con-
centrations encountered during the test. (See I A.) Range changes
shall be accomplished either by the use of stacked sample cells
or changes in the electronic circuitry, or both.
D. Zero supression: Various techniques of zero supression may be used
to increase readability. Note, that by supressin^ the zero response, the
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readability of the emission response is increased, but accuracy of
this response expressed as a percent of full-scale value does not
change.
III. Total hydrocarbon analyzer:
A. Analyzer description: The measurement of total hydrocarbon
is to be made by an analyzer. using a flame ionizaticti detector (FID).
With this type detector an ionization current proportional to the mass.
rate of hydrocarbon entering a hydrogen flame is measured by an electro-
meter amplifier and continuously recorded.
The analyzer shall be fitted with a constant-temperature oven
housing the detector and sample-handling components. It shall maintain
temperature within +_2°C.of the set point.
The detector and sample-handling components shall be suitable
for continuous operation at temperatures to 200°C.
B. Analyzer specification:
Response time (pneumatic)—15 percent of full-scale in .5
secoi\ds or less.
Response time (electrical)--95 percent of full scale in 0.5
seconds or less,
Noise*-'-+l_ percent of full scale on most sensitive range.
Repeatability—+1 percent of full scale.
Zero drift—Less than +1 perecent of full scale in 2 hours
on all ranges.
Span drift'—Less than +1 perecnt of full scale in 2 hours
on all ranges.
Linearity—Response with propane in. air shall be linear
within + 2 percent.
C. Detector response optimization:
(1). Follow manufacturers instructions for instrument
start-up and basic operating adjustments.
(a) The fuel shall contain 40 + 1% hydrogen. The
balance shall be helium. The mixture shall contain
less than 2 ppm C hydrocarbon.
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(b) The air shall contain 21 + 1% oxygen. Compressed
"hydrocarbon-free" grade of atmospheric air meets the
oxygen-concentration requirements. The air shall contain
less than 2 ppm C hydrocarbon.
(2) Set the oven temperature 5°C hotter than the required
sample-line.temperature. Allov/ at least one-half hour after
the oven has reached temperature for the system to equilibrate.
(3) Peak the detector: With the fuel and air set at the •
•manufacturer's settings, introduce a mixture of propane in
a.±r to the detector. The propane concentration should be
approximately 8Q ppm C + 20 ppm C. Determine the response
at a given fuel fIov7 from the difference between the span-
gas response and the zero-gas response. Incrementally adjust
the fuel flow above and below the manufacturer's specification.
Record the span and zero response at these fuel flows. A
plot of the difference between the span and zero response versus
fuel flow will be similar to the one shown in Fig .111-1. Ad-
just the fuel flow-rate to the rich side of the curve, as shown.
This is an initial flow-rate setting and may not be the final
optimized-flow-rate.
(4) Oxygen effect: check the response of the detector with
various concentrations of oxygen in the sample. Conduct this
test with the oven temperature set as required by step III B (2).
The initial fuel flow shall be the same as that determined by
step III B (3).
(a) Zero the analyzer with hydrocarbon-free air. Introduce
nitrogen (N2) zero-gas. The response to the nitrogen zero-
gas must be less than 0.5 percent of full-scale value of
the lowest anticipated range.
(b) The following blends of calibration gases shall be used
to determine the effect of oxygen (02) in the sample.
Calibration-Gas 0? concentration Balance
Propane 21% . N2
Propane ' 15% N2
Propane 10% N2
Propane 5% N2
Propane 0% N2
The oxygen-concentration blend-tolerance is + 1%
(i.e. 10 + 1% means 9% to 11%). The analysis of the oxygen-
concentration must be within + 1% of the absolute con-
centration-value. The calibration-gas concentration should
be about 80 ppm C + 20 ppm C and must be known within + 1%
of the absolute concentration-value.
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Detector
Response
Optimum
Fuel Flow
Figure III - I
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-5-
(c) Calibrate the analyzer with the calibration
mixture containing 21% oxygen.
(d) Introduce the calibration mixtures containing
the 15, 10, 5 and 0 percent oxygen to the detector
in sequence. Record the response to each of the
mixtures.
(e) Recheck the zero response. If it has changed,
repeat the test.
(f) Calculate the oxygen interference (% 02j) for
the 15, 10, 5, and 0 percent oxygen-mixtures by
equation III-l.
ClII.'-l) % 02J = Bx - Analyzer Response (ppm C)
Bx
where
Bx = hydrocarbon concentration of the oxygen-
interference cylinders (15%, 10%, 5% and 0%)
(III-2) Analyzer Response =
[hydrocarbon concentration (ppm C) in the 21% mixture] (100) (% of Full-Scale ana-
% of full-scale analyzer response due to 21% mixture lyzer response due to Bx)
(g) If the oxygen interference for the 15, 10, and 5 per-
cent oxygen mixtures is less than + 2% and less than +2.5%
for the zero percent oxygen mixture, then no oxygen-
interference correction-factor need be used.
(h) If the oxygen interference is greater than the
specifications, incrementally adjust the air flow above
and below the manufacturer's specifications, and repeat
subparagraphs (c) through (g) of step III C (4).
(j) "If the oxygen interference is still greater than
. the specifications, repair or replace the detector.
(5) Linearity:
(a) With the fuel flow, air flow, and sample flow adjusted
to meet the oxygen interference specification, the instrument
linearity shall be checked for the ranges covering the range
of analysis using propane-in-air with nominal concentrations
of 30, 60, -and 90 percent of full-scale of each range. The
deviation of a bestrfit curve from a least-squares best-fit
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straight line.should not exceed 2 percent of the value
at any point. If this specification is met, concentra-
tion values may be calculated by use of single calibration
factor.
Note, by varying the air, fuel, and sample flow^rates
within the boundaries of the oxygen interference specifica?-
tions, the analyzer may produce a more linear response. If
the deviation exceeds 2 percent at any point, concentration
values sha.ll be calculated from a calibration curve prepared
during this alignment procedure (III C (5)).
(b) With the exception of any possible changes required by
subparagraph (6) of III C, the flow-rate, air flow-rate,
and sample flow-rate are defined as "optimized" at this
point.
(6) Initially, and within every 180 days thereafter, make
a comparison of response to the different classes of compounds
using Cindividually) propylene, toluene, n-hexane, and propane,
each at 20 to 50 ppm C concentration in air. If the response
to propylene, toluene, or n-hexane differs by more than 5 percent
from the response to propane, check instrument operating para-
meters, Reducing sample flow rate generally improves uniformity
of response,
iy. Oxides of Nitrogen (NOx) Analyzer:
A- Analyzer description: The method of measuring total oxides of
nitrogen consists of two distinct operations. First the nitrogen dioxide
(N02) in the sample is converted to an equivalent amount of nitric oxide
(NO). Next this amount of (NO) is added to the NO that was already in
th,e sample.. This total amount of NO is then measured by the chemilumine-
scence method.
(.1) N02 -*• NO Converter: There are at least two methods of con-
venting N02 to NO. The most frequently used methods employ either
a thermal-conversion principle of a combination of thermal-con-
version and catalytic-conversion. In order to meet the sample
response-times required, it is usually necessary to employ a
high flow-rate convertor. The governing criterion for the
converter is that it must have a minimum conversion efficiency
of -90% when converting N02 ~> NO.
(2) Chemiluminescence Reaction Chamber; The chemiluminescence
method utilizes the principle that nitric oxide (NO) reacts with
ozone (03) to give nitrogen dioxide (N02) and oxygen (02). Approxi-
mately 10 percent of the N02 is electronically excited. The transi-
tion of excited N02 to the ground state yields a light emission
(600-2600 nanometer region at low pressures). The detectable
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-7-
region of this emission depends on the PM-tube/optical filter
being used in the detector. The intensity of this emission
is proportional to the mass flow 'rate of NO into the reactor.
The light emission can be measured utilizing a photomultiplier
tube and associated electronics.
B. Analyzer specifications: Specifications for the oxides of
nitrogen analysis system are:
Response time (pneumatic)— 15 percent of full-scale in 1.5
seconds or less.
Response time (electrical) — 95 percent of full-scale in 0.5
seconds of less.
Noise'-'-Less than 1 percent of full-scale.
Repeatability — +1 percent of full-scale.
Zero drift — Less than +1 percent of full-scale in 2 hours.
Span drift — Less than +1 percent of full-scale in 2 hours.
Linearity—Linear to within +2 percent of full-scale on all
ranges.
C. System optimization:
(1). Follow manufacturer's instructions for instrument start-up
and basic operating adjustments.
(2) NC>2 -»- NO Converter Check: The apparatus described and
illustrated in Figure IV-1 is to be used to determine the
conversion efficiency of devices that convert NOx to NO. The
following procedure is to be used for determining the values
to be used in Equation IV-1.
(a) Attach the NO/N2 supply (150-250 ppm) at C2, the 02
supply at Cl and the analyzer inlet connection to the
• efficiency detector at C3. If lower concentrations of
NO are used, air may be used in place of Q£ to facilitate
better control of the N0£ genernated during step (d).
(b) With the efficiency detector variac off, place the
NOx converter in bypass .mode and close valve V3 . Open
valve NV2 until sufficient flow and stable readings are
obtained at the analyzer. Zero and span the analyzer
output to indicate the value of the NO concentration
being used. Record this concentration.
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(c) Open valye V3 (on/off flow control solenoid valve
for 62) and adjust valve MV1 (02 supply metering valve)
to blend enough 02 to lower the NO concentration (b)
about 10 percent. Record this concentration.
Cd) Turn on the ozonator and increase its supply voltage
until the NO concentration of (c) is reduced to about
20 percent of (b). N00 is now being formed from the NO +
G-, reaction. There must always be at least 10 percent un-
reacted NO at this point. Record this concentration.
(e) When a stable reading has been obtained from (d),
place the NOx converter in the convert mode. The analyzer
will now indicate the total NOx concentration. Record
this concentration.
(f) Turn off the ozonator and allow the analyzer reading
to stabilize. The mixture NO + 02 is still passing through
the converter. This reading is the total NOx concentration
of the dilute NO span gas used at step (c). Record this
concentration.
Cg) Close valve V3, The NO concentration should be equal
to or greater than the reading of (b) indicating whether
the NO- contains any M^- Calculate the efficiency of the
NOx converter by substituting the concentrations obtained
during the. test into Equation (IV-1).
OV-1) % Eff, = -• [(e) - (f)]
1 + ](c) - (d)] x 100%
The efficiency of the converter should be greater than 90
percent. Adjusting the converter temperature may be needed
to maximize the efficiency. Although steps (b) and (g)
are not used in the calculations, their values should be
recorded to complete the data set for the test sequence.
This procedure does not depend on the amount of N02 in the
span gas nor the equivalence of flows in the by-pass and
converter modes. However, to be consistent with good
. operating practice, flows should be nominally the same,
and the N02 concentration should be less than 5% of the
NOx span concentration. Efficiency checks shall be made
weekly.
(h) If the converter does not meet the conversion-ef-
ficiency specifications, repair or replace the unit.
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(3) Carbon Dioxide (002) and carbon monoxide interference
check:
(a) Calibrate the NOx analyzer on the lowest anticipated
range that may be used during testing.
(b) Introduce (separately) blends of C02/N0x and CO/NOx
(diluent ^) to the analysis system* The C02 and CO
concentrations should be approximately equal to the highest
concentration that may be measured during testing. The
NOx concentration should be similar to the concentration
used in step a). Record the response.
(c) Recheck calibration. If it has shifted, recalibrate
and rerun the interference test.
(d) The difference between the NOx response with the
interference gases and the calculated NOx response must
not be greater than + 2 percent. The calculated response
is based on the calibration curve (Step (c)) and the in-
terference-bottle NOx concentration.
(e) The interference from C0~ and CO in this checking
procedure must be less than 2 percent.
(4) Linearity:
(a) With the operating parameters adjusted to meet the
converter efficiency check and the interference checks,
the instrument linearity shall be checked for the ranges
of analysis using HO in N£ at nominal concentrations of
30, 60, and 90 percent of full-scale of each range. The
deviation of a best-fit curve from a least-squares best-fit
straight line should not exceed 2 percent of the value
at any point. If this specification is met, concentration
values may be calculated by use of a single calibration
factor. If the deviation exceeds 2 percent at any point,
concentration values shall be calculated from a calibration
curve prepared during this alignment procedure (IV C (4)).
(b) The operating parameters are defined as "optimized" at
this point.
V. Humidity Calculations:
A. The specific humidity (H) is defined by equation (V-l).
(V-l) H = • K Pv
BARO - Pv
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where
BAE.O = barometric pressure (Pa)
Pv = partial pressure of water vapor (Pa)
'CIS. 01534 LB. of H20) (18.01534 'gm of H20)
LB. Mole gtf< Mole
K-^' _ ' ~ _ ; _ __ = .6219
C28.967 LB. of Dry Air) (28 . 967 gm of Dry Air )
LB, Mole gm Mole
units of H = LB. of H20 = gm of H_2_0
LB, of Dry Air gm of Dry Air
B. The partial pressure of water vapor may be determined in
two manners:
(1) A dew point device may be used. In that case:
Pv = PDP = staturation .-vapor pressure of water at
the Dew-Point temperature, (Pa)
C2) A wet*-bulb, dry-bulb method may be used. In that
case "Ferrels equation" (eq, (V-2)) is used.
(V-2) Pv = PTO -(3.67)(10)-4 (BARO)(tdb - twh)ftwb +1539]
1571
P^ and (BARO) must have the same units
where
1, = Dry bulb temperature (°F)
temperature (°F)
C. The saturated vapor pressure of water at the wet-bulb temperature
(P^rg) is defined by equation (V-3) (Ref. Wexler and Greenspan, equation
(23), National Bureau of Standards).
9
(V-3) P = (e) [B in T + Z F.
1=0
where
•^WB ~ is in Pascals (Pa.)
T ~ Wet~tulb temperature C°;K)
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B = -12.150799
F0 = -8.49922(10)3
F-L = -7.4231865(10)3
F2 = 96.1635147
F3 = 2.4917646 0-0)"2
F4 = -1.3160119Q-0)-5
F5 = -1.1460454(10)~8
F6 = 2.1701289(10)-11
F7 = -3.610253(10)-15
Fg = 3.8504519(10)~18
Fg = -1.4317(10)-21
•]). The saturate vapor pressure of water at the dry^bulb temperature
(Png) is found (if required) by using dry-bulb absolute-temperature (°K)
in equation (V^-3).
E, The percent of relative humidity (RH) (if required) is defined
by equation (V-4).
(V-4) RH = Ey. (100)
PDB
C6) The water<-vapor volume-concentration of the engine intake
air (Y) is defined by equation (V-5):
CV-5) Y = (H) (Mair) = Pv
BARO-PV
where
Mair = Molecular weight of air = 28.967
MH2o = Molecular weight of water = 18.01534
VI. Airflow Measurement: There are many different methods of measuring
airflow to Diesel and gasoline engines. The method used should have a turn-
down ratio large enough to accurately measure the airflow over the engine
operating range during the test. Preferred measurement techniques include
measurement by a laminar flow device or a vortex shedding device. Other
techniques may be used; however, the overall measurement accuracy should
be +1 percent of full-scale value of the measurement device.
(1) Engine System: When measuring inlet air, various engines
systems may have additions or subtractions of small quantities
of air downstream of the airflow measuring device. An example
of air addition would be an air injection system (i.e. air pump).
An example of air subtraction would be compressor bleed-air that
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is used to operate an intercooler fan on a turbocharged
engine. This bleed-air is normally vented to the atmosphere
and does not pass through the engine. In determining the (f/a)
ratio for the required calculations, use the following conventions:
(a) Wet to Dry conversion factor (Kw): When calculating
the (f/a) ratio to be used in determining Kw, use only the
airflow entering the combustion chamber. This may require
substraction of bleed-air, etc. from the measured airflow.
(b) Fuel/Air ratio comparison: When comparing measured (f/a)
ratio to an emissions calculated (f/a) ratio the, measured
airflow (in terms of mass) is the total mass of air entering
the exhaust pipe. This may include additions of air mass to
the exhaust pipe by an air injection system.
(2) Corrections to the measured air mass-flow-rate: When an engine
system incorporates devices that add or substract air mass as deter-
mined by VI (1), determine the air mass from these devices by one
of the following methods:
(a) Measure the air mass-flow from the device during each
operating mode.
(b) Determine that the air mass-flow for each mode, from
the device is typical for many system applications. Then
the device flow-rate for each mode may be generally applied.
(c) Under certain circumstances, such as turbomachinery,
theorectical calculations that predict the device mass flow-
rate during each mode may be used.
(3) Gasoline fueled engine systems: When measuring air flow-rate
of a gasoline engine, special care must be taken in the areas of
flow distribution, velocity profiles, and pressure drop to the engine
system:
(a) "Flow distribution: The air-cleaner is considered part
,of the engine system. Flow distribution should be considered
as flow distribution to the air cleaner. A plenum chamber
of sufficient volume is recommended to insure uniform distri-
bution to the engine.
(b) Velocity profile: The velocity profile is considered
the velocity profile to the air cleaner. The shape of the
plenum chamber and the entrance to the plenum chamber in-
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fluence the velocity distribution. The desired condition
is a uniform velocity - profile with a velocity between 3.3
to 13.2 metres per second (10 to 40 feet per second delivering
air to the air cleaner.
(c) Pressure drop: During the measurement process of air
flow, the velocity at the point of measurement is usually
quite high, i.e. as high as 61 metres/sec (200 ft/sec). In
order to slow this velocity down to the desired velocity
range in the plenum chamber without incurring additional
pressure-losses, it is recommended that a diffusser be used
between the. air-flow measurement device and the plenum chamber.
In any case, the pressure drop (from atmospheric pressure)
at the inlet to the air cleaner should not be more than 1.74
kPa (7.0 in H20).
(d) Vents: Devices like PCV valves that vent to the air
cleaner, should continue to be vented to the air cleaner.
Devices that vent to the atmosphere as some carburetor float
vents, governors, etc. should vent to the plenum chamber.
(e) Hot air: Engine inlet air temperature: Due to the
preconditioning schedule, ambient soak, and subsequent warm-
up idle, the first test-sequence should not be considered
a cold test-sequence. Therefore, considering current under-
hood-temperatures on a 20°C (68°F) to 30°C (86°F) day, devices
that provide hot air to the carburetor are defined as non-
functional during the test sequence. Use the following conven-
tion in determining the inlet air temperature to the engine:
(A) Ducted Ambient-Air: On engines that use ducted
ambient-air to the carburetor, the hot-air device should
be non-functional during the test sequence. The engine
should induct ambient air at 20°C (68°F) to 30°C (86°F).
(B) Under-Hood Air: On engines that induct air under
the hood, the hot air device (if used) will be non-
functional during the test sequence. The engine should
induct air at a typical under hood temperature that would
occur on a 20°C (68°F) to 30°C (86°F) day. The manu-
facturer should specify and substantiate the under hood
intake air temperature.
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