Document ID: chunk:federal_register_of_legislation:F2012C00283:reg:3:p17
Version: federal_register_of_legislation:F2012C00283
Segment Type: reg
Provision Reference: reg 3 (pt 17/18)
Character Range: 409632–412714

final readings CHCf, Pf, Tf for the hydrocarbon retention check.
              2.3.11. Using the formula in paragraph 2.4. below, the hydrocarbon mass is then calculated from the readings taken in paragraphs 2.3.10. and 2.3.6. above. The mass may not differ by more than 3 per cent from the hydrocarbon mass given in paragraph 2.3.7. above.
              2.4. Calculations
               The calculation of net hydrocarbon mass change within the enclosure is used to determine the chamber's hydrocarbon background and leak rate. Initial and final readings of hydrocarbon concentration, temperature and barometric pressure are used in the following formula to calculate the mass change.
 Where:
 MHC      =  hydrocarbon mass in grams,
 MHC,out  =  mass of hydrocarbons exiting the enclosure, in the case of fixed-volume enclosures for diurnal emission testing (grams),
 MHC,i    =  mass of hydrocarbons entering the enclosure when a fixed-volume enclosure is used for testing diurnal emissions (grams),
 CHC      =  hydrocarbon concentration in the enclosure (ppm carbon
             (Note: ppm carbon = ppm propane x 3)),
 V        =  enclosure volume in cubic metres,
 T        =  ambient temperature in the enclosure, (K),
 P        =  barometric pressure, (kPa),
 K        =  17.6;

 Where:
i           is the initial reading,
 f          is the final reading.

              3. Checking of FID hydrocarbon analyzer

              3.1. Detector response optimisation

               The FID shall be adjusted as specified by the instrument manufacturer. Propane in air should be used to optimise the response on the most common operating range.

              3.2. Calibration of the HC analyser

               The analyser should be calibrated using propane in air and purified synthetic air. See paragraph 3.2. of Appendix 3 of Annex 4a.

               Establish a calibration curve as described in paragraphs 4.1. to 4.5. of this appendix.

              3.3. Oxygen interference check and recommended limits

               The response factor (Rf) for a particular hydrocarbon species is the ratio of the FID C1 reading to the gas cylinder concentration, expressed as ppm C1. The concentration of the test gas shall be at a level to give a response of approximately 80 per cent of full-scale deflection, for the operating range. The concentration shall be known, to an accuracy of 2 per cent in reference to a gravimetric standard expressed in volume. In addition the gas cylinder shall be preconditioned for 24 hours at a temperature between 293 K and 303 K (20 and 30 °C).

               Response factors should be determined when introducing an analyser into service and thereafter at major service intervals. The reference gas to be used is propane with balance purified air which is taken to give a response factor of 1.00.

               The test gas to be used for oxygen interference and the recommended response factor range are given below:

               Propane and nitrogen:    0.95  Rf  1.05.

              4. Calibration of the hydrocarbon analyzer