Document ID: chunk:federal_register_of_legislation:F2023L00129:reg:13:p40
Version: federal_register_of_legislation:F2023L00129
Segment Type: reg
Provision Reference: reg 13 (pt 40/56)
Character Range: 405334–408175

analyzers calculated.
 The CLD mean value shall be subtracted from the NDUV mean value. This difference shall be multiplied by the ratio of the expected mean HC concentration to the HC concentration measured during the verification, as follows:
                       (82)
 Where:
                     cNOx,CLD is the measured NOx concentration with CLD, ppm
                     cNOx,NDUV is the measured NOx concentration with NDUV, ppm
                     cHC,e is the expected max. HC concentration, ppm
                     cHC,m is the measured HC concentration, ppm
9.3.9.3.2. Maximum allowable quench
 The combined HC and water quench shall not exceed 2 per cent of the NOx concentration expected during testing.
9.3.9.4. Sample dryer
 A sample dryer removes water, which can otherwise interfere with a NOx measurement.
              9.3.9.4.1. Sample dryer efficiency

              For dry CLD analysers, it shall be demonstrated that for the highest expected water vapour concentration Hm (see paragraph 9.3.9.2.2.), the sample dryer maintains CLD humidity at ≤ 5 g water/kg dry air (or about 0.8 volume per cent H2O), which is 100 per cent relative humidity at 3.9 °C and 101.3 kPa. This humidity specification is also equivalent to about 25 per cent relative humidity at 25 °C and 101.3 kPa. This may be demonstrated by measuring the temperature at the outlet of a thermal dehumidifier, or by measuring humidity at a point just upstream of the CLD. Humidity of the CLD exhaust might also be measured as long as the only flow into the CLD is the flow from the dehumidifier.

9.3.9.4.2. Sample dryer NO2 penetration
 Liquid water remaining in an improperly designed sample dryer can remove NO2 from the sample. If a sample dryer is used in combination with an NDUV analyzer without an NO2/NO converter upstream, it could therefore remove NO2 from the sample prior NOx measurement.
 The sample dryer shall allow for measuring at least 95 per cent of the total NO2 at the maximum expected concentration of NO2.
9.3.10. Sampling for raw gaseous emissions, if applicable
 The gaseous emissions sampling probes shall be fitted at least 0.5 m or three times the diameter of the exhaust pipe - whichever is the larger - upstream of the exit of the exhaust gas system but sufficiently close to the engine as to ensure an exhaust gas temperature of at least 343 K (70 °C) at the probe.
 In the case of a multi-cylinder engine with a branched exhaust manifold, the inlet of the probe shall be located sufficiently far downstream so as to ensure that the sample is representative of the average exhaust emissions from all cylinders. In multi-cylinder engines having distinct groups of manifolds, such as in a "Vee" engine configuration, it is recommended to combine the manifolds upstream of the sampling probe. If this is not practical, it