Document ID: chunk:federal_register_of_legislation:F2023C00229:reg:9:p29
Version: federal_register_of_legislation:F2023C00229
Segment Type: reg
Provision Reference: reg 9 (pt 29/71)
Character Range: 290839–293843

then these alternatives may be used.

1.6.                            Verification of the calibration

              Each normally used operating range shall be checked prior to each analysis in accordance with the following procedure.

              The calibration shall be checked by using a zero gas and a span gas whose nominal value is more than 80 % of full scale of the measuring range.

              If, for the two points considered, the value found does not differ by more than ± 4 % of full scale from the declared reference value, the adjustment parameters may be modified. Should this not be the case, a new calibration curve shall be established in accordance with Section 1.5.5.

1.7.                            Efficiency test of the NOx converter

              The efficiency of the converter used for the conversion of NO2 into NO shall be tested as given in Sections 1.7.1 to 1.7.8 (Figure 6).

1.7.1.                        Test set-up

              Using the test set-up as shown in Figure 6 (see also Annex III, Appendix 4, Section 3.3.5) and the procedure below, the efficiency of converters can be tested by means of an ozonator.

1.7.2.                        Calibration

              The CLD and the HCLD shall be calibrated in the most common operating range following the manufacturer's specifications using zero and span gas (the NO content of which must amount to about 80 % of the operating range and the NO2 concentration of the gas mixture to less than 5 % of the NO concentration). The NOx analyser must be in the NO mode so that the span gas does not pass through the converter. The indicated concentration has to be recorded.

1.7.3.                        Calculation

              The efficiency of the NOx converter is calculated as follows:

              Where:

              a = is the NOx concentration according to Section 1.7.6

         b = is the NOx concentration according to Section 1.7.7

         c = is the NO concentration according to Section 1.7.4

         d = is the NO concentration according to Section 1.7.5

1.7.4.                        Adding of oxygen

              Via a T-fitting, oxygen or zero air is added continuously to the gas flow until the concentration indicated is about 20 % less than the indicated calibration concentration given in Section 1.7.2. (The analyser is in the NO mode). The indicated concentration c shall be recorded. The ozonator is kept deactivated throughout the process.

1.7.5.                        Activation of the ozonator

              The ozonator is now activated to generate enough ozone to bring the NO concentration down to about 20 % (minimum 10 %) of the calibration concentration given in Section 1.7.2. The indicated concentration d shall be recorded. (The analyser is in the NO mode).

1.7.6.                        NOx mode

              The NO analyser is then switched to the NOx mode so that the gas mixture (consisting of NO, NO2, O2 and N2) now passes through the converter.