§ 1065.360 - FID optimization and verification.

§ 1065.360 FID optimization and verification.

Cross Reference

Link to an amendment published at 89 FR 29798, Apr. 22, 2024.

(a) Scope and frequency. For all FID analyzers, calibrate the FID upon initial installation. Repeat the calibration as needed using good engineering judgment. For a FID that measures THC, perform the following steps:

(1) Optimize the response to various hydrocarbons after initial analyzer installation and after major maintenance as described in paragraph (c) of this section.

(2) Determine the methane (CH₄) response factor after initial analyzer installation and after major maintenance as described in paragraph (d) of this section.

(3) If you determine NMNEHC by subtracting from measured THC, determine the ethane (C₂H₆) response factor after initial analyzer installation and after major maintenance as described in paragraph (f) of this section. Verify the C₂H₆ response within 185 days before testing as described in paragraph (f) of this section.

(4) For any gaseous-fueled engine, including dual-fuel and flexible-fuel engines, you You may determine the methane (CH₄) and ethane (C₂H₆) response factors as a function of the molar water concentration in the raw or diluted exhaust. If you choose the option in this paragraph (a)(4), generate and verify the humidity level (or fraction) as described in § 1065.365(dg)(11).

(b) Calibration. Use good engineering judgment to develop a calibration procedure, such as one based on the FID-analyzer manufacturer's instructions and recommended frequency for calibrating the FID. Alternately, you may remove system components for off-site calibration. For a FID that measures THC, calibrate using C₃H₈ calibration gases that meet the specifications of § 1065.750. For a FID that measures CH₄, calibrate using CH₄ calibration gases that meet 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. If you use a FID to measure CH₄ downstream of a nonmethane cutter (NMC), you may calibrate that FID using CH₄ calibration gases with the cutterNMC. Regardless of the calibration gas composition, calibrate 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. As another example, if you use a CH₄ span gas with a concentration of 200 µmol/mol, span the FID to respond with a value of 200 µmol/mol.

(c) THC FID response optimization. This procedure is only for FID analyzers that measure THC. Use good engineering judgment for initial instrument start-up and basic operating adjustment using FID fuel and zero air. Heated FIDs must be within their required operating temperature ranges. Optimize FID response at the most common analyzer range expected during emission testing. Optimization involves adjusting flows and pressures of FID fuel, burner air, and sample to minimize response variations to various hydrocarbon species in the exhaust. Use good engineering judgment to trade off peak FID response to propane calibration gases to achieve minimal response variations to different hydrocarbon species. For an example of trading off response to propane for relative responses to other hydrocarbon species, see SAE 770141 (incorporated by reference in , see § 1065.1010). Determine the optimum flow rates and/or pressures for FID fuel, burner air, and sample and record them for future reference.

(d) THC FID CH₄response 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, RF_{CH4[THC-FID],} after FID optimization. Use the most recent RF_CH4[THC-FID] measured according to this section in the calculations for HC determination described in § 1065.660 to compensate for CH₄ response. Determine RF_CH4[THC-FID] as follows, noting that you do not determine RF_CH4[THC-FID] for FIDs that are calibrated and spanned using CH₄ with a nonmethane cutteran 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.

(3) Start and operate the FID analyzer according to the manufacturer's instructions.

(4) Confirm that the FID analyzer has been calibrated using C₃H₈. 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.

(5) Zero the FID with a zero gas that you use for emission testing.

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

(9) While the analyzer measures the CH₄ concentration, record 30 seconds of sampled data. 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) Determine 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(

d

g)

(11)

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

CH₄ calibration gas, adjusted for water content, to determine the FID analyzer's CH₄ response factor, RF_{CH4[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.

(iv) Use this functional relationship to determine the response factor during an emission test.

(e) THC FID CH₄response verification. This procedure is only for FID analyzers that measure THC. Verify RF_CH4[THC-FID] as follows:

(1) Perform a CH₄ response factor determination as described in paragraph (d) of this section. If the resulting value of RF_CH4[THC-FID] is within ±5% of its most recent previously determined value, the THC FID passes the CH₄ response verification. For example, if the most recent previous value for RF_CH4[THC-FID] was 1.05 and it increased by 0.05 to become 1.10 or it decreased by 0.05 to become 1.00, either case would be acceptable because ±4.8% is less than ±5%.

(2) If RF_CH4[THC-FID] is not within the tolerance specified in paragraph (e)(1) of this section, use good engineering judgment to verify that the flow rates and/or pressures of FID fuel, burner air, and sample are at their most recent previously recorded values, as determined in paragraph (c) of this section. You may adjust these flow rates as necessary. Then determine the RF_CH4[THC-FID] as described in paragraph (d) of this section and verify that it is within the tolerance specified in this paragraph (e).

(3) If RF_CH4[THC-FID] is not within the tolerance specified in this paragraph (e), re-optimize the FID response as described in paragraph (c) of this section.

(4) Determine a new RF_CH4[THC-FID] as described in paragraph (d) of this section. Use this new value of RF_CH4[THC-FID] in the calculations for HC determination, as described in § 1065.660.

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

(f) THC FID C₂ H₆ response factor determination. This procedure is only for FID analyzers that measure THC. Since FID analyzers generally have a different response to C₂H₆ than C₃H₈, determine the THC-FID analyzer's C₂H₆ response factor, RF_{C2H6[THC-FID],} after FID optimization using the procedure described in paragraph (d) of this section, replacing CH₄ with C₂H₆. Use the most recent RF_{C2H6[THC-FID]} measured according to this section in the calculations for HC determination described in § 1065.660 to compensate for C₂H₆ response.

[73 FR 37308, June 30, 2008, as amended at 75 FR 23041, Apr. 30, 2010; 76 FR 57447, Sept. 15, 2011; 79 FR 23769, Apr. 28, 2014; 81 FR 74168, Oct. 25, 2016; 86 FR 34543, June 29, 2021; 89 FR 29798, Apr. 22, 2024]