Section

[Code of Federal Regulations]

[Title 40, Volume 31]

[Revised as of July 1, 2006]

From the U.S. Government Printing Office via GPO Access

[CITE: 40CFR1065.140]

[Page 689-691]

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.

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 690]]

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 691]]

(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.