Document ID: chunk:federal_register_of_legislation:F2012C00283:reg:21:p18
Version: federal_register_of_legislation:F2012C00283
Segment Type: reg
Provision Reference: reg 21 (pt 18/39)
Character Range: 306462–309422

and purified air: 0.90 < Rf < 1.00

                These are relative to a response factor (Rf) of 1.00 for propane and purified air.
              2.3.4. Oxygen interference check and recommended limits
               The response factor shall be determined as described in paragraph 2.3.3. above. The test gas to be used and recommended response factor range is:
               Propane and nitrogen: 0.95 < Rf < 1.05
              2.4. NOx Converter Efficiency Test Procedure
               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 11 and the procedure described below, the efficiency of converters can be tested by means of an ozonator.
              2.4.1. 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.
              2.4.2. Via a T-fitting, oxygen or synthetic air is added continuously to the span gas flow until the concentration indicated is about 10 per cent less than the indicated calibration concentration given in paragraph 2.4.1. above. Record the indicated concentration (c). The ozonator is kept deactivated throughout this process.
              2.4.3. The ozonator is now activated to generate enough ozone to bring the NO concentration down to 20 per cent (minimum 10 per cent) of the calibration concentration given in paragraph 2.4.1. above. Record the indicated concentration (d).
              2.4.4. The NOx analyser is then switched to the NOx mode, which means that the gas mixture (consisting of NO, NO2, O2 and N2 ) now passes through the converter. Record the indicated concentration (a).
              2.4.5. The ozonator is now deactivated. The mixture of gases described in paragraph 2.4.2. above passes through the converter into the detector. Record the indicated concentration (b).

Figure 11
NOx Converter Efficiency Test Configuration
              2.4.6.  With the ozonator deactivated, the flow of oxygen or synthetic air is also shut off. The NO2 reading of the analyser shall then be no more than 5 per cent above the figure given in paragraph 2.4.1. above.
              2.4.7.  The efficiency of the NOx converter is calculated as follows:

       2.4.8.  The efficiency of the converter shall not be less than 95 per cent.

       2.4.9.  The efficiency of the converter shall be tested at least once a week.

3.  Reference gases

3.1.  Pure gases

               The following pure gases shall be available, if necessary, for calibration and operation:

               Purified nitrogen: (purity: ≤ 1 ppm C,