40 CFR § 1065.520 - Pre-test verification procedures and pre-test data collection.
(a) For tests in which you measure PM emissions, follow the procedures for PM sample preconditioning and tare weighing according to § 1065.590.
(b) Unless the standard-setting part specifies different tolerances, verify at some point before the test that ambient conditions are within the tolerances specified in this paragraph (b). For purposes of this paragraph (b), “before the test” means any time from a point just prior to engine starting (excluding engine restarts) to the point at which emission sampling begins.
(1) Ambient temperature of (20 to 30) °C. See § 1065.530(j) for circumstances under which ambient temperatures must remain within this range during the test.
(2) Atmospheric pressure of (80.000 to 103.325) kPa and within ±5 kPa of the value recorded at the time of the last engine map. You are not required to verify atmospheric pressure prior to a hot start test interval for testing that also includes a cold start.
(3) Dilution air conditions as specified in § 1065.140, except in cases where you preheat your CVS before a cold start test. We recommend verifying dilution air conditions just prior to the start of each test interval.
(c) You may test engines at any intake-air humidity, and we may test engines at any intake-air humidity.
(d) Verify that auxiliary-work inputs and outputs are configured as they were during engine mapping, as described in § 1065.510(a).
(e) You may perform a final calibration of the speed, torque, and proportional-flow control systems, which may include performing practice duty cycles (or portions of duty cycles). This may be done in conjunction with the preconditioning in § 1065.518.
(f) If your testing requires a chemical balance, then before the start of emissions testing select the chemical balance method and the gaseous emission measurement equipment required for testing. Select the chemical balance method depending on the fuels used during testing:
(1) When using only carbon-containing fuels, use the carbon-based chemical balance procedure in § 1065.655.
(2) When using only fuels other than carbon-containing fuels, use the hydrogen-based chemical balance procedure in § 1065.656.
(3) When using constant mixtures of carbon-containing fuels and fuels other than carbon- containing fuels, use the following chemical balance methods and gaseous emission measurement equipment:
(i) If the hydrogen-to-carbon ratio, a, of the fuel mixture is less than or equal to 6, then use the carbon-based chemical balance procedure in § 1065.655.
(ii) Otherwise, use the hydrogen-based chemical balance procedure in § 1065.656.
(4) When using variable mixtures of carbon-containing fuels and fuels other than carbon-containing fuels, if the mean hydrogen-to-carbon ratio of the fuel mixture, a, is expected to be greater than 6 for a test interval, you must use the hydrogen-based chemical balance procedure in § 1065.656 for that test interval. Otherwise, you may use the carbon-based chemical balance procedure in § 1065.655.
(g) If your testing requires measuring hydrocarbon emissions, verify the amount of nonmethane hydrocarbon contamination in the exhaust and background HC sampling systems within 8 hours before the start of the first test interval of each duty-cycle sequence for laboratory tests. You may verify the contamination of a background HC sampling system by reading the last bag fill and purge using zero gas. For any NMHC measurement system that involves separately measuring CH4 and subtracting it from a THC measurement or for any CH4 measurement system that uses an NMC, verify the amount of THC contamination using only the THC analyzer response. There is no need to operate any separate CH4 analyzer for this verification; however, you may measure and correct for THC contamination in the CH4 sample path for the cases where NMHC is determined by subtracting CH4 from THC or, where CH4 is determined, using an NMC as configured in § 1065.365(d), (e), and (f); and using the calculations in § 1065.660(b)(2). Perform this verification as follows:
(1) Select the HC analyzer range for measuring the flow-weighted mean concentration expected at the HC standard.
(2) Zero the HC analyzer at the analyzer zero or sample port. Note that FID zero and span balance gases may be any combination of purified air or purified nitrogen that meets the specifications of § 1065.750. We recommend FID analyzer zero and span gases that contain approximately the flow-weighted mean concentration of O2 expected during testing.
(3) Span the HC analyzer using span gas introduced at the analyzer span or sample port. Span on a carbon number basis of one (C1). For example, if you use a C3H8 span gas of concentration 200 µmol/mol, span the FID to respond with a value of 600 µmol/mol.
(4) Overflow zero gas at the HC probe inlet or into a tee near the probe outlet.
(5) Measure the THC concentration in the sampling and background systems as follows:
(i) For continuous sampling, record the mean THC concentration as overflow zero gas flows.
(ii) For batch sampling, fill the sample medium (e.g., bag) and record its mean THC concentration.
(iii) For the background system, record the mean THC concentration of the last fill and purge.
(6) Record this value as the initial THC concentration, xTHC[THC-FID]init, and use it to correct measured values as described in § 1065.660.
(7) You may correct the measured initial THC concentration for drift as follows:
(i) For batch and continuous HC analyzers, after determining the initial THC concentration, flow zero gas to the analyzer zero or sample port. When the analyzer reading is stable, record the mean analyzer value.
(ii) Flow span gas to the analyzer span or sample port. When the analyzer reading is stable, record the mean analyzer value.
(iii) Use mean analyzer values from paragraphs (g)(2) and (3) and (g)(7)(i) and (ii) of this section to correct the initial THC concentration recorded in paragraph (g)(6) of this section for drift, as described in § 1065.550.
(8) If any of the xTHC[THC-FID]init values exceed the greatest of the following values, determine the source of the contamination and take corrective action, such as purging the system during an additional preconditioning cycle or replacing contaminated portions:
(i) 2% of the flow-weighted mean concentration expected at the HC (THC or NMHC) standard.
(ii) 2% of the flow-weighted mean concentration of HC (THC or NMHC) measured during testing.
(iii) 2 µmol/mol.
(9) If corrective action does not resolve the deficiency, you may request to use the contaminated system as an alternate procedure under § 1065.10.