[Code of Federal Regulations]
[Title 40, Volume 31]
[Revised as of July 1, 2007]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR1065.140]
[Page 690-692]
TITLE 40--PROTECTION OF ENVIRONMENT
CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
PART 1065_ENGINE-TESTING PROCEDURES--Table of Contents
Subpart B_Equipment Specifications
Sec. 1065.140 Dilution for gaseous and PM constituents.
(a) General. You may dilute exhaust with ambient air, synthetic air,
or nitrogen that is at least 15 [deg]C. Note that the composition of the
diluent affects some gaseous emission measurement instruments' response
to emissions. We recommend diluting exhaust at a location as close as
possible to the location where ambient air dilution would occur in use.
(b) Dilution-air conditions and background concentrations. Before a
diluent is mixed with exhaust, you may precondition it by increasing or
decreasing its temperature or humidity. You may also remove constituents
to reduce their background concentrations. The following provisions
apply to removing constituents or accounting for background
concentrations:
(1) You may measure constituent concentrations in the diluent and
compensate for background effects on test results. See Sec. 1065.650
for calculations that compensate for background concentrations.
(2) Either measure these background concentrations the same way you
measure diluted exhaust constituents, or measure them in a way that does
not affect your ability to demonstrate compliance with the applicable
standards. For example, you may use the following simplifications for
background sampling:
(i) You may disregard any proportional sampling requirements.
(ii) You may use unheated gaseous sampling systems.
(iii) You may use unheated PM sampling systems only if we approve it
in advance.
(iv) You may use continuous sampling if you use batch sampling for
diluted emissions.
(v) You may use batch sampling if you use continuous sampling for
diluted emissions.
(3) For removing background PM, we recommend that you filter all
dilution air, including primary full-flow dilution air, with high-
efficiency particulate air (HEPA) filters that have an initial minimum
collection efficiency specification of 99.97% (see Sec. 1065.1001 for
procedures related to HEPA-filtration efficiencies). Ensure that HEPA
filters are installed properly so that background PM does not leak past
the HEPA filters. If you choose to correct for background PM without
using HEPA filtration, demonstrate that the background PM in the
dilution air contributes less than 50% to the net PM collected on the
sample filter.
(c) Full-flow dilution; constant-volume sampling (CVS). You may
dilute the full flow of raw exhaust in a dilution tunnel that maintains
a nominally constant volume flow rate, molar flow rate or mass flow rate
of diluted exhaust, as follows:
(1) Construction. Use a tunnel with inside surfaces of 300 series
stainless steel. Electrically ground the entire dilution tunnel. We
recommend a thin-walled and insulated dilution tunnel to minimize
temperature differences between the wall and the exhaust gases.
(2) Pressure control. Maintain static pressure at the location where
raw exhaust is introduced into the tunnel within 1.2 kPa of atmospheric
pressure. You may use a booster blower to control this pressure. If you
test an engine using more careful pressure control and you show by
engineering analysis or by test data that you require this level of
control to demonstrate compliance at the applicable standards, we will
maintain the same level of static pressure control when we test that
engine.
(3) Mixing. Introduce raw exhaust into the tunnel by directing it
downstream along the centerline of the tunnel. You may introduce a
fraction of dilution air radially from the tunnel's inner surface to
minimize exhaust interaction with the tunnel walls. You may configure
the system with turbulence generators such as orifice plates or fins to
achieve good mixing. We recommend a minimum Reynolds number,
[[Page 691]]
Re#, of 4000 for the diluted exhaust stream, where Re# is based on the
inside diameter of the dilution tunnel. Re# is defined in Sec.
1065.640.
(4) Flow measurement preconditioning. You may condition the diluted
exhaust before measuring its flow rate, as long as this conditioning
takes place downstream of any sample probes, as follows:
(i) You may use flow straighteners, pulsation dampeners, or both of
these.
(ii) You may use a filter.
(iii) You may use a heat exchanger to control the temperature
upstream of any flow meter. Note paragraph (c)(6) of this section
regarding aqueous condensation.
(5) Flow measurement. Section 1065.240 describes measurement
instruments for diluted exhaust flow.
(6) Aqueous condensation. You may either prevent aqueous
condensation throughout the dilution tunnel or you may measure humidity
at the flow meter inlet. Calculations in Sec. 1065.645 and Sec.
1065.650 account for either method of addressing humidity in the diluted
exhaust. Note that preventing aqueous condensation involves more than
keeping pure water in a vapor phase (see Sec. 1065.1001).
(7) Flow compensation. Maintain nominally constant molar, volumetric
or mass flow of diluted exhaust. You may maintain nominally constant
flow by either maintaining the temperature and pressure at the flow
meter or by directly controlling the flow of diluted exhaust. You may
also directly control the flow of proportional samplers to maintain
proportional sampling. For an individual test, validate proportional
sampling as described in Sec. 1065.545.
(d) Partial-flow dilution (PFD). Except as specified in this
paragraph (d), you may dilute a partial flow of raw or previously
diluted exhaust before measuring emissions. Sec. 1065.240 describes
PFD-related flow measurement instruments. PFD may consist of constant or
varying dilution ratios as described in paragraphs (d)(2) and (3) of
this section. An example of a constant dilution ratio PFD is a
``secondary dilution PM'' measurement system. An example of a varying
dilution ratio PFD is a ``bag mini-diluter'' or BMD.
(1) Applicability. (i) You may not use PFD if the standard-setting
part prohibits it.
(ii) You may use PFD to extract a proportional raw exhaust sample
for any batch or continuous PM emission sampling over any transient duty
cycle only if we have explicitly approved it according to Sec. 1065.10
as an alternative procedure to the specified procedure for full-flow
CVS.
(iii) You may use PFD to extract a proportional raw exhaust sample
for any batch or continuous gaseous emission sampling.
(iv) You may use PFD to extract a proportional raw exhaust sample
for any batch or continuous PM emission sampling over any steady-state
duty cycle or its ramped-modal cycle (RMC) equivalent.
(v) You may use PFD to extract a proportional raw exhaust sample for
any batch or continuous field-testing.
(vi) You may use PFD to extract a proportional diluted exhaust
sample from a CVS for any batch or continuous emission sampling.
(vii) You may use PFD to extract a constant raw or diluted exhaust
sample for any continuous emission sampling.
(2) Constant dilution-ratio PFD. Do one of the following for
constant dilution-ratio PFD:
(i) Dilute an already proportional flow. For example, you may do
this as a way of performing secondary dilution from a CVS tunnel to
achieve temperature control for PM sampling.
(ii) Continuously measure constituent concentrations. For example,
you might dilute to precondition a sample of raw exhaust to control its
temperature, humidity, or constituent concentrations upstream of
continuous analyzers. In this case, you must take into account the
dilution ratio before multiplying the continuous concentration by the
sampled exhaust flow rate.
(iii) Extract a proportional sample from the constant dilution ratio
PFD system. For example, you might use a variable-flow pump to
proportionally fill a gaseous storage medium such as a bag from a PFD
system. In this case, the proportional sampling must meet the same
specifications as varying dilution ratio PFD in paragraph (d)(3) of this
section.
[[Page 692]]
(3) Varying dilution-ratio PFD. All the following provisions apply
for varying dilution-ratio PFD:
(i) Use a control system with sensors and actuators that can
maintain proportional sampling over intervals as short as 200 ms (i.e.,
5 Hz control).
(ii) For control input, you may use any sensor output from one or
more measurements; for example, intake-air flow, fuel flow, exhaust
flow, engine speed, and intake manifold temperature and pressure.
(iii) Account for any emission transit time in the PFD system.
(iv) You may use preprogrammed data if they have been determined for
the specific test site, duty cycle, and test engine from which you
dilute emissions.
(v) We recommend that you run practice cycles to meet the validation
criteria in Sec. 1065.545. Note that you must validate every emission
test by meeting the validation criteria with the data from that specific
test, not from practice cycles or other tests.
(vi) You may not use a PFD system that requires preparatory tuning
or calibration with a CVS or with the emission results from a CVS.
Rather, you must be able to independently calibrate the PFD.
(e) Dilution and temperature control of PM samples. Dilute PM
samples at least once upstream of transfer lines. You may dilute PM
samples upstream of a transfer line using full-flow dilution, or
partial-flow dilution immediately downstream of a PM probe. Control
sample temperature to a (47 5) [deg]C tolerance,
as measured anywhere within 20 cm upstream or downstream of the PM
storage media (such as a filter). Measure this temperature with a bare-
wire junction thermocouple with wires that are (0.500 0.025) mm diameter, or with another suitable instrument
that has equivalent performance. Heat or cool the PM sample primarily by
dilution.