Document ID: chunk:federal_register_of_legislation:F2011C00805:reg:120:p13
Version: federal_register_of_legislation:F2011C00805
Segment Type: reg
Provision Reference: reg 120 (pt 13/23)
Character Range: 269057–272063

measuring results is less than 2 per cent.

         2. CHECKING FOR FID HYDROCARBON RESPONSE

         2.1.  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.

         2.2.  Calibration of the HC analyser

         The analyser should be calibrated using propane in air and purified synthetic air. See paragraph 4.5.2. of Annex 4 (calibration and span gases).

         Establish a calibration curve as described in paragraphs 1.1. to 1.5. of this Appendix.

         2.3.  Response factors of different hydrocarbons 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 pre-conditioned 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 test gases to be used and the recommended response factors are:

                                     Methane and purified air: 1.00 < Rf < 1.15

                                     or   1.00 < Rf < 1.05 for NG fuelled vehicles

                                     Propylene and purified air: 0.90 < Rf < 1.00

                                     Toluene and purified air: 0.90 < Rf < 1.00

         Relative to a response factor (Rf) of 1.00 for propane and purified air.

         2.4.  Oxygen interference check and recommended limits

         The response factor shall be determined as described in paragraph 2.3. above. The test gas to be used and recommended response factor range is:

                                     Propane and nitrogen: 0.95 < Rf < 1.05

         3.  EFFICIENCY TEST OF THE NOx CONVERTER

         The efficiency of the converter used for the conversion of NO2 into NO is tested as follows:

         Using the test set up as shown in Figure 6/1 and the procedure described below, the efficiency of converters can be tested by means of an ozonator.

         3.1. Calibrate the analyzer in the most common operating range following the manufacturer's specifications using zero and span gas (the NO content of which shall amount to about 80 per cent of the operating range and the NO2 concentration of the gas mixture shall be less than 5 per cent of the NO concentration). The NOx analyser shall be in the NO mode so that the span gas does not pass through the converter. Record the indicated concentration.

         3.2. Via a T-fitting, oxygen or synthetic