Document ID: chunk:federal_register_of_legislation:F2023L00129:reg:13:p37
Version: federal_register_of_legislation:F2023L00129
Segment Type: reg
Provision Reference: reg 13 (pt 37/56)
Character Range: 397586–400554

the removal of the non-methane hydrocarbons from the sample gas by oxidizing all hydrocarbons except methane. Ideally, the conversion for methane is 0 per cent, and for the other hydrocarbons represented by ethane is 100 per cent. For the accurate measurement of NMHC, the two efficiencies shall be determined and used for the calculation of the NMHC emission mass flow rate (see paragraph 8.6.2.).
9.3.8.1. Methane Efficiency
 Methane calibration gas shall be flown through the FID with and without bypassing the NMC and the two concentrations recorded. The efficiency shall be determined as follows:
                       (75)

 Where:
                     cHC(w/NMC) is the HC concentration with CH4 flowing through the NMC, ppm C
                     cHC(w/o NMC) is the HC concentration with CH4 bypassing the NMC, ppm C
9.3.8.2. Ethane Efficiency
 Ethane calibration gas shall be flown through the FID with and without bypassing the NMC and the two concentrations recorded. The efficiency shall be determined as follows:
                       (76)

 Where:
                     cHC(w/NMC) is the HC concentration with C2H6 flowing through the NMC, ppm C
                     cHC(w/o NMC) is the HC concentration with C2H6 bypassing the NMC, ppm C
9.3.9. Interference effects
 Other gases than the one being analyzed can interfere with the reading in several ways. Positive interference occurs in NDIR instruments where the interfering gas gives the same effect as the gas being measured, but to a lesser degree. Negative interference occurs in NDIR instruments by the interfering gas broadening the absorption band of the measured gas, and in CLD instruments by the interfering gas quenching the reaction. The interference checks in paragraphs 9.3.9.1. and 9.3.9.3. shall be performed prior to an analyzer's initial use and after major service intervals.
9.3.9.1. CO analyzer interference check
 Water and CO2 can interfere with the CO analyzer performance. Therefore, a CO2 span gas having a concentration of 80 to 100 per cent of full scale of the maximum operating range used during testing shall be bubbled through water at room temperature and the analyzer response recorded. The analyzer response shall not be more than 2 per cent of the mean CO concentration expected during testing.
 Interference procedures for CO2 and H2O may also be run separately. If the CO2 and H2O levels used are higher than the maximum levels expected during testing, each observed interference value shall be scaled down by multiplying the observed interference by the ratio of the maximum expected concentration value to the actual value used during this procedure. Separate interference procedures concentrations of H2O that are lower than the maximum levels expected during testing may be run, but the observed H2O interference shall be scaled up by multiplying the observed interference by the ratio of the maximum expected H2O concentration value to the actual value used