§1065.660. THC, NMHC, NMNEHC, CH 4 , and C 2 H 6 determination. — Inbound Citations

(2) For additive deterioration factors, the difference between emissions at the end of useful life and emissions at the low-hour test point.

Diesel exhaust fluid (DEF) means a liquid reducing agent (other than the engine fuel) used in conjunction with selective catalytic reduction to reduce NOX emissions. Diesel exhaust fluid is generally understood to be an aqueous solution of urea conforming to the specifications of ISO 22241.

Discrete-mode means relating to the discrete-mode type of steady-state test described in § 1039.505.

Dual-fuel means relating to an engine designed for operation on two different fuels but not on a continuous mixture of those fuels (see § 1039.601(b)). For purposes of this part, such an engine remains a dual-fuel engine even if it is designed for operation on three or more different fuels.

Emergency equipment means any of the following types of equipment that is not a motor vehicle:

(3) A distinct operator demand setting, such as would occur when testing locomotives or constant-speed engines.

Neat means fuel that is free from mixture or dilution with other fuels. For example, hydrogen or natural gas fuel used without diesel pilot fuel are neat.

NIST-accepted means relating to a value that has been assigned or named by NIST.

NIST-traceable means relating to a standard value that can be related to NIST-stated references through an unbroken chain of comparisons, all having stated uncertainties, as specified in NIST Technical Note 1297 (incorporated by reference, see § 1065.1010). Allowable uncertainty limits specified for NIST-traceability refer to the propagated uncertainty specified by NIST.

Noise means the precision of 30 seconds of updated recorded values from a measurement instrument as it quantifies a zero or reference value. Determine instrument noise, repeatability, and accuracy from the same data set. We specify a procedure for determining noise in § 1065.305.

No-load means a dynamometer setting of zero torque.

Nonmethane hydrocarbon equivalent (NMHCE) means the sum of the carbon mass contributions of non-oxygenated nonmethane hydrocarbons, alcohols and aldehydes, or other organic compounds that are measured separately as contained in a gas sample, expressed as exhaust nonmethane hydrocarbon from petroleum-fueled engines. The hydrogen-to-carbon ratio of the equivalent hydrocarbon is 1.85:1.

Nonmethane hydrocarbons (NMHC) means the sum of all hydrocarbon species except methane. Refer to § 1065.660 for NMHC determination.

Nonmethane nonethane hydrocarbon (NMNEHC) means the sum of all hydrocarbon species except methane and ethane. Refer to § 1065.660 for NMNEHC determination.

Nonroad means relating to nonroad engines.

Nonroad engine has the meaning we give in 40 CFR 1068.30. In general this means all internal-combustion engines except motor vehicle engines, stationary engines, engines used solely for competition, or engines used in aircraft.

Open crankcase emissions means any flow from an engine's crankcase that is emitted directly into the environment. Crankcase emissions are not “open crankcase emissions” if the engine is designed to always route all crankcase emissions back into the engine (for example, through the intake system or an aftertreatment system) such that all the crankcase emissions, or their products, are emitted into the environment only through the engine exhaust system.

Operator demand means an engine operator's input to control engine output. The “operator” may be a person (i.e., manual), or a governor (i.e., automatic) that mechanically or electronically signals an input that demands engine output. Input may be from an accelerator pedal or signal, a throttle-control lever or signal, a fuel lever or signal, a speed lever or signal, or a governor setpoint or signal. Output means engine power, P, which is the product of engine speed, fn, and engine torque, T.

Oxides of nitrogen means NO and NO2 as measured by the procedures specified in § 1065.270. Oxides of nitrogen are expressed quantitatively as if the NO is in the form of NO2, such that you use an effective molar mass for all oxides of nitrogen equivalent to that of NO2.

Oxygenated fuels means fuels composed of at least 25% oxygen-containing compounds, such as ethanol or methanol. Testing engines that use oxygenated fuels generally requires the use of the sampling methods in subpart I of this part. However, you should read the standard-setting part and subpart I of this part to determine appropriate sampling methods.

Partial pressure means the pressure, p, attributable to a single gas in a gas mixture. For an ideal gas, the partial pressure divided by the total pressure is equal to the constituent's molar concentration, x.

Percent (%) means a representation of exactly 0.01. Numbers expressed as percentages in this part (such as a tolerance of ±2%) have infinite precision, so 2% and 2.000000000% have the same meaning. This means that where we specify some percentage of a total value, the calculated value has the same number of significant digits as the total value. For example, 2% of a span value where the span value is 101.3302 is 2.026604.

Portable emission measurement system (PEMS) means a measurement system consisting of portable equipment that can be used to generate brake-specific emission measurements during field testing or laboratory testing.

Precision means two times the standard deviation of a set of measured values of a single zero or reference quantity. See also the related definitions of noise and repeatability in this section.

Procedures means all aspects of engine testing, including the equipment specifications, calibrations, calculations and other protocols and specifications needed to measure emissions, unless we specify otherwise.

Proving ring is a device used to measure static force based on the linear relationship between stress and strain in an elastic material. It is typically a steel alloy ring, and you measure the deflection (strain) of its diameter when a static force (stress) is applied across its diameter.

PTFE means polytetrafluoroethylene, commonly known as Teflon TM.

Purified air means air meeting the specifications for purified air in § 1065.750. Purified air may be produced by purifying ambient air. The purification may occur at the test site or at another location (such as at a gas supplier's facility). Alternatively, purified air may be synthetically generated, using good engineering judgment, from purified oxygen and nitrogen. The addition of other elements normally present in purified ambient air (such as Ar) is not required.

Ramped-modal means relating to a ramped-modal type of steady-state test, as described in the standard-setting part.

Recommend has the meaning given in § 1065.201.

Rechargeable Energy Storage System (RESS) means engine or equipment components that store recovered energy for later use to propel the vehicle or accomplish a different primary function. Examples of RESS include the battery system or a hydraulic accumulator in a hybrid vehicle.

Regression statistics means any of the regression statistics specified in § 1065.602.

Repeatability means the precision of ten mean measurements of a reference quantity. Determine instrument repeatability, accuracy, and noise from the same data set. We specify a procedure for determining repeatability in § 1065.305.

Revoke has the meaning given in 40 CFR 1068.30.

Rise time, t10-90, means the time interval of a measurement instrument's response after any step increase to the input between the following points:

(b) Determine nonmethane-cutter performance as described in § 1065.365 and use the results to calculate CH4 or NMHC emissions in § 1065.660.

(a) This section describes a verification procedure for system response and updating-recording frequency for continuous gas analyzers that output a single gas species mole fraction (i.e., concentration) based on a continuous combination of multiple gas species measured with multiple detectors (i.e., gas analyzers continuously compensated for other gas species). See § 1065.308 for verification procedures that apply to continuous gas analyzers that are not continuously compensated for other gas species or that use only one detector for gaseous species. Perform this verification to determine the system response of the continuous gas analyzer and its sampling system. This verification is required for continuous gas analyzers used for transient or ramped-modal testing. You need not perform this verification for batch gas analyzers or for continuous gas analyzers that are used only for discrete-mode testing. For this check we consider water vapor a gaseous constituent. This verification does not apply to any processing of individual analyzer signals that are time-aligned to their t50 times and were verified according to § 1065.308. For example, this verification does not apply to correction for water removed from the sample done in post-processing according to § 1065.659 (40 CFR 1066.620 for vehicle testing) and it does not apply to NMHC determination from THC and CH4 according to § 1065.660. Perform this verification after initial installation (i.e., test cell commissioning) and after any modifications to the system that would change the system response.

(7) When the overflow HC concentration does not exceed 2 µmol/mol, record this value as xTHCinit and use it to correct for HC contamination as described in § 1065.660.

(d) You may use any gas analyzer for this test. If you use a FID for this test, correct for any HC contamination in the sampling system according to § 1065.660. If you use an O2 analyzer described in § 1065.280 for this test, you may use purified N2 to detect a leak. To avoid misleading results from this test, we recommend using only analyzers that have a repeatability of 0.5% or better at the reference gas concentration used for this test. Perform a vacuum-side leak test as follows:

(3) Route overflow reference gas to the inlet of the sample probe or at a tee fitting in the transfer line near the exit of the probe. You may use a valve upstream of the overflow fitting to prevent overflow of reference gas out of the inlet of the probe, but you must then provide an overflow vent in the overflow supply line.

(4) Verify that the measured overflow reference gas concentration is within ±0.5% of the concentration measured in paragraph (d)(2) of this section. A measured value lower than expected indicates a leak, but a value higher than expected may indicate a problem with the reference gas or the analyzer itself. A measured value higher than expected does not indicate a leak.

(d) 4 response factor determination. This procedure is only for FID analyzers that measure THC. Since FID analyzers generally have a different response to CH4 versus C3H8, determine the THC-FID analyzer's CH4 response factor, RFCH4[THC-FID], after FID optimization. Use the most recent RFCH4[THC-FID] measured according to this section in the calculations for HC determination described in § 1065.660 to compensate for CH4 response. Determine RFCH4[THC-FID] as follows, noting that you do not determine RFCH4[THC-FID] for FIDs that are calibrated and spanned using CH4 with an NMC:

(1) Select a C3 H8 span gas concentration that you use to span your analyzers before emission testing. Use only span gases that meet the specifications of § 1065.750. Record the C3H8 concentration of the gas.

(2) Select a CH4 span gas concentration that you use to span your analyzers before emission testing. Use only span gases that meet the specifications of § 1065.750. Record the CH4 concentration of the gas.

(4) Calibrate on a carbon number basis of one (C1). For example, if you use a C3 H8 span gas of concentration 200 µmol/mol, span the FID to respond with a value of 600 µmol/mol.

(6) Span the FID with the C3H8 span gas that you selected under paragraph (d)(1) of this section.

(7) Introduce the CH4 span gas that you selected under paragraph (d)(2) of this section into the FID analyzer.

(8) Stabilization time may include time to purge the analyzer and to account for its response.

(9) Calculate the arithmetic mean of these values.

(10) For analyzers with multiple ranges, you need to perform the procedure in this paragraph (d) only on a single range.

(11) Divide the mean measured concentration by the recorded span concentration of the CH4 calibration gas. The result is the FID analyzer's response factor for CH4, RF CH4[THC-FID].

(12) You may determine the response factor as a function of molar water concentration using the following procedures and use this response factor to account for the CH4 response for NMHC determination described in § 1065.660(b)(2)(iii):

(i) Humidify the CH4 span gas as described in § 1065.365(g) and repeat the steps in paragraphs (d)(7) through (9) of this section until measurements are complete for each setpoint in the selected range.

(ii) Divide each mean measured CH4 concentration by the recorded span concentration of the CH4 calibration gas, adjusted for water content, to determine the FID analyzer's CH4 response factor, RFCH4[THC-FID].

(iii) Use the CH4 response factors at the different setpoints to create a functional relationship between response factor and molar water concentration, downstream of the last sample dryer if any sample dryers are present.

(a) If you use a FID analyzer and an NMC to measure methane (CH4), verify that the catalytic activity of the NMC has not deteriorated as described in this section. Determine the NMC's penetration fractions (PF) of CH4 and ethane (C2H6) and, if applicable, the FID analyzer response factors using the appropriate procedures of paragraph (d), (e), or (f) of this section. As detailed in this section, these penetration fractions may be determined as a combination of NMC penetration fractions and FID analyzer response factors, depending on your particular NMC and FID analyzer configuration. Perform this verification after installing the NMC and repeat this verification within 185 days of testing. Note that because NMCs can deteriorate rapidly and without warning if they are operated outside of certain ranges of gas concentrations and outside of certain temperature ranges, good engineering judgment may dictate that you determine an NMC's penetration fractions more frequently. Use the most recently determined penetration fraction from this section to calculate HC emissions according to § 1065.660 as applicable.

(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.

(v) Calculate all NMHC and CH4 concentrations, including dilution air background concentrations, as described in § 1065.660.

(6) Record this value as the initial HC concentration, xTHCinit, and use it to correct measured values as described in § 1065.660.

(3) Calculate all NMHC and CH4 concentrations, including dilution air background concentrations, as described in 40 CFR 1065.660.

(iii) Correct all THC and CH4 concentrations for initial contamination as described in § 1065.660(a), including continuous readings, sample bags readings, and dilution air background readings.

(1) For vehicles above 14,000 pounds GVWR, correct all THC and CH4 concentrations for initial contamination as described in 40 CFR 1065.660(a), including continuous readings, sample bag readings, and dilution air background readings. This correction is optional for vehicles at or below 14,000 pounds GVWR.

(1) Measure emissions of NOX, CO, and CO2. We may require you to also measure emissions of HC and PM. You may determine HC emissions by any method specified in 40 CFR 1065.660(b).

(viii) Describe the method you used to determine HC as specified in 40 CFR 1065.660(b).

(e) For demonstrating compliance with NMHC standards, you may either measure THC and determine NMHC mass as described in § 1065.660(b)(1), or you may measure THC and CH4 and determine NMHC as described in § 1065.660(b)(2) or (3). You may also use the additive method in § 1065.660(b)(4) for natural gas-fueled engines as described in § 1065.266. See 40 CFR 1066.635 for methods to demonstrate compliance with NMOG standards for vehicle testing.

(5) Compare the corrected mass of NMHC to corrected mass of THC. If the corrected mass of NMHC is greater than 0.98 times the corrected mass of THC, take the corrected mass of NMHC to be 0.98 times the corrected mass of THC. If you omit the NMHC calculations as described in § 1065.660(b)(1), take the corrected mass of NMHC to be 0.98 times the corrected mass of THC.

(e) For demonstrating compliance with NMHC standards, you may either measure THC and determine NMHC mass as described in § 1065.660(b)(1), or you may measure THC and CH4 and determine NMHC as described in § 1065.660(b)(2) or (3). You may also use the additive method in § 1065.660(b)(4) for natural gas-fueled engines as described in § 1065.266. See 40 CFR 1066.635 for methods to demonstrate compliance with NMOG standards for vehicle testing.

(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) 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 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.

(ii) For batch sampling, fill the sample medium (e.g., bag) and record its mean THC concentration.

(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) 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.

(11) Use RFPFC2H6[NMC-FID] and RFPFCH4[NMC-FID] in emission calculations according to § 1065.660(b)(2)(i) and (d)(1)(i).

(10) Divide the mean C2H6 concentration measured through the NMC by the mean C2H6 concentration measured after bypassing the NMC. The result is the C2H6 penetration fraction, PFC2H6[NMC-FID]. Use this penetration fraction according to § 1065.660(b)(2)(ii) and (d)(1)(ii).

(14) Divide the mean CH4 concentration measured through the NMC by the mean CH4 concentration measured after bypassing the NMC. The result is the CH4 penetration fraction, PFCH4[NMC-FID]. Use this CH4 penetration fraction according to § 1065.660(b)(2)(iii) and (d)(1)(iii).

(11) Use RFPFC2H6[NMC-FID] and RFPFCH4[NMC-FID] in emission calculations according to § 1065.660(b)(2)(i) and (d)(1)(i).

(10) Divide the mean C2H6 concentration measured through the NMC by the mean C2H6 concentration measured after bypassing the NMC. The result is the C2H6 penetration fraction, PFC2H6[NMC-FID]. Use this penetration fraction according to § 1065.660(b)(2)(ii) and (d)(1)(ii).

(12) You may determine the response factor as a function of molar water concentration using the following procedures and use this response factor to account for the CH4 response for NMHC determination described in § 1065.660(b)(2)(iii):

(i) Humidify the CH4 span gas as described in § 1065.365(g) and repeat the steps in paragraphs (d)(7) through (9) of this section until measurements are complete for each setpoint in the selected range.

(ii) Divide each mean measured CH4 concentration by the recorded span concentration of the CH4 calibration gas, adjusted for water content, to determine the FID analyzer's CH4 response factor, RFCH4[THC-FID].

(iii) Use the CH4 response factors at the different setpoints to create a functional relationship between response factor and molar water concentration, downstream of the last sample dryer if any sample dryers are present.

(14) Divide the mean CH4 concentration measured through the NMC by the mean CH4 concentration measured after bypassing the NMC. The result is the CH4 penetration fraction, PFCH4[NMC-FID]. Use this CH4 penetration fraction according to § 1065.660(b)(2)(iii) and (d)(1)(iii).

(e) For demonstrating compliance with NMHC standards, you may either measure THC and determine NMHC mass as described in § 1065.660(b)(1), or you may measure THC and CH4 and determine NMHC as described in § 1065.660(b)(2) or (3). You may also use the additive method in § 1065.660(b)(4) for natural gas-fueled engines as described in § 1065.266. See 40 CFR 1066.635 for methods to demonstrate compliance with NMOG standards for vehicle testing.

(e) 4 and C2H6 from THC. Determine NMHC from subtraction of CH4 from THC as described in § 1065.660(b)(3) and NMNEHC from subtraction of CH4 and C2H6 as described § 1065.660(c)(2). Determine CH4 as described in § 1065.660(d)(2) and C2H6 as described § 1065.660(e).

(e) For demonstrating compliance with NMHC standards, you may either measure THC and determine NMHC mass as described in § 1065.660(b)(1), or you may measure THC and CH4 and determine NMHC as described in § 1065.660(b)(2) or (3). You may also use the additive method in § 1065.660(b)(4) for natural gas-fueled engines as described in § 1065.266. See 40 CFR 1066.635 for methods to demonstrate compliance with NMOG standards for vehicle testing.

(d) To determine NMNEHC, measure ethene, ethyne, propane, propene, butane, formaldehyde, acetaldehyde, formic acid, and methanol. To determine NMHC, measure ethane in addition to those same hydrocarbon species. Determine NMHC and NMNEHC as described in § 1065.660(b)(4) and (c)(3).

(f) For demonstrating compliance with NMNEHC standards, you may either measure NMHC or determine NMNEHC mass as described in § 1065.660(c)(1), you may measure THC, CH4, and C2H6 and determine NMNEHC as described in § 1065.660(c)(2), or you may use the additive method in § 1065.660(c)(3).

(i) If the test fuel has less than 0.010 mol/mol of ethane and you omit the NMNEHC calculations as described in § 1065.660(c)(1), take the corrected mass of NMNEHC to be 0.95 times the corrected mass of NMHC.

(f) For demonstrating compliance with NMNEHC standards, you may either measure NMHC or determine NMNEHC mass as described in § 1065.660(c)(1), you may measure THC, CH4, and C2H6 and determine NMNEHC as described in § 1065.660(c)(2), or you may use the additive method in § 1065.660(c)(3).

(e) 4 and C2H6 from THC. Determine NMHC from subtraction of CH4 from THC as described in § 1065.660(b)(3) and NMNEHC from subtraction of CH4 and C2H6 as described § 1065.660(c)(2). Determine CH4 as described in § 1065.660(d)(2) and C2H6 as described § 1065.660(e).

(f) For demonstrating compliance with NMNEHC standards, you may either measure NMHC or determine NMNEHC mass as described in § 1065.660(c)(1), you may measure THC, CH4, and C2H6 and determine NMNEHC as described in § 1065.660(c)(2), or you may use the additive method in § 1065.660(c)(3).

(d) To determine NMNEHC, measure ethene, ethyne, propane, propene, butane, formaldehyde, acetaldehyde, formic acid, and methanol. To determine NMHC, measure ethane in addition to those same hydrocarbon species. Determine NMHC and NMNEHC as described in § 1065.660(b)(4) and (c)(3).

(g) 4. For reporting CH4 or for demonstrating compliance with CH4 standards, you may use a FID analyzer with a nonmethane cutter as described in § 1065.265 or you may use a GC-FID as described in § 1065.267. Determine CH4 as described in § 1065.660(d).

(11) Use RFPFC2H6[NMC-FID] and RFPFCH4[NMC-FID] in emission calculations according to § 1065.660(b)(2)(i) and (d)(1)(i).

(10) Divide the mean C2H6 concentration measured through the NMC by the mean C2H6 concentration measured after bypassing the NMC. The result is the C2H6 penetration fraction, PFC2H6[NMC-FID]. Use this penetration fraction according to § 1065.660(b)(2)(ii) and (d)(1)(ii).

(14) Divide the mean CH4 concentration measured through the NMC by the mean CH4 concentration measured after bypassing the NMC. The result is the CH4 penetration fraction, PFCH4[NMC-FID]. Use this CH4 penetration fraction according to § 1065.660(b)(2)(iii) and (d)(1)(iii).

(e) 4 and C2H6 from THC. Determine NMHC from subtraction of CH4 from THC as described in § 1065.660(b)(3) and NMNEHC from subtraction of CH4 and C2H6 as described § 1065.660(c)(2). Determine CH4 as described in § 1065.660(d)(2) and C2H6 as described § 1065.660(e).

(e) 4 and C2H6 from THC. Determine NMHC from subtraction of CH4 from THC as described in § 1065.660(b)(3) and NMNEHC from subtraction of CH4 and C2H6 as described § 1065.660(c)(2). Determine CH4 as described in § 1065.660(d)(2) and C2H6 as described § 1065.660(e).