40 CFR 89.319 - Hydrocarbon analyzer calibration.
(a) The FID hydrocarbon analyzer shall receive the initial and periodic calibration as described in this section. The HFID used with petroleum-fueled diesel (compression-ignition) engines shall be operated to a set point ±5.5 °C between 185 and 197 °C.
(b) Initial and periodic optimization of detector response. Prior to introduction into service and at least annually thereafter, adjust the FID hydrocarbon analyzer for optimum hydrocarbon response as specified in this paragraph. Alternate methods yielding equivalent results may be used, if approved in advance by the Administrator.
(1) Follow good engineering practices for initial instrument start-up and basic operating adjustment using the appropriate fuel (see § 89.312(e)) and zero-grade air.
(2) Optimize the FID's response on the most common operating range. The response is to be optimized with respect to fuel pressure or flow. Efforts shall be made to minimize response variations to different hydrocarbon species that are expected to be in the exhaust. Good engineering judgment is to be used to trade off optimal FID response to propane-in-air against reductions in relative responses to other hydrocarbons. A good example of trading off response on propane for relative responses to other hydrocarbon species is given in Society of Automotive Engineers (SAE) Paper No. 770141, “Optimization of Flame Ionization Detector for Determination of Hydrocarbon in Diluted Automotive Exhausts”; author Glenn D. Reschke. It is also required that the response be set to optimum condition with respect to air flow and sample flow. Heated Flame Ionization Detectors (HFIDs) must be at their specified operating temperature. One of the following procedures is required for FID or HFID optimization:
(i) The procedure outlined in Society of Automotive Engineers (SAE) paper No. 770141, “Optimization of a Flame Ionization Detector for Determination of Hydrocarbon in Diluted Automotive Exhausts”; author, Glenn D. Reschke. This procedure has been incorporated by reference at § 89.6.
(ii) The HFID optimization procedures outlined in 40 CFR part 1065, subpart D.
(iii) Alternative procedures may be used if approved in advance by the Administrator.
(iv) The procedures specified by the manufacturer of the FID or HFID.
(3) After the optimum flow rates have been determined, record them for future reference.
(c) Initial and periodic calibration. Prior to introduction into service, after any maintenance which could alter calibration, and monthly thereafter, the FID or HFID hydrocarbon analyzer shall be calibrated on all normally used instrument ranges using the steps in this paragraph (c). Use the same flow rate and pressures as when analyzing samples. Calibration gases shall be introduced directly at the analyzer, unless the “overflow” calibration option of 40 CFR part 1065, subpart F, for the HFID is taken. New calibration curves need not be generated each month if the existing curve can be verified as continuing to meet the requirements of paragraph (c)(3) of this section.
(1) Adjust analyzer to optimize performance.
(2) Zero the hydrocarbon analyzer with zero-grade air.
(3) Calibrate on each used operating range with propane-in-air (dilute or raw) or propane-in-nitrogen (raw) calibration gases having nominal concentrations starting between 10-15 percent and increasing in at least six incremental steps to 90 percent (e.g., 15, 30, 45, 60, 75, and 90 percent of that range) of that range. The incremental steps are to be spaced to represent good engineering practice. For each range calibrated, if the deviation from a least-squares best-fit straight line is 2 percent or less of the value at each data point, concentration values may be calculated by use of a single calibration factor for that range. If the deviation exceeds 2 percent at each non-zero data point and within ±0.3 percent of full scale on the zero, the best-fit non-linear equation which represents the data to within these limits shall be used to determine concentration.
(d) Oxygen interference optimization (required for raw). Choose a range where the oxygen interference check gases will fall in the upper 50 percent. Conduct the test, as outlined in this paragraph, with the oven temperature set as required by the instrument manufacturer. Oxygen interference check gas specifications are found in § 89.312(d).
(1) Zero the analyzer.
(2) Span the analyzer with the 21% oxygen interference gas specified in § 89.312(d).
(3) Recheck zero response. If it has changed more than 0.5 percent of full scale repeat paragraphs (d)(1) and (d)(2) of this section to correct problem.
(4) Introduce the 5 percent and 10 percent oxygen interference check gases.
(5) Recheck the zero response. If it has changed more ±1 percent of full scale, repeat the test.
(6) Calculate the percent of oxygen interference (designated as percent O2I) for each mixture in paragraph (d)(4) of this section.