Document ID: chunk:federal_register_of_legislation:F2024L00447:reg:0:p27
Version: federal_register_of_legislation:F2024L00447
Segment Type: reg
Provision Reference: reg 0 (pt 27/57)
Character Range: 166356–169352

is the actual water vapour concentration [%]

(iii) Maximum allowable quench
                     The combined CO2 and water quench shall not exceed 2 per cent of full scale.

                  (d) Quench check for NDUV analysers

                  Hydrocarbons and water can positively interfere with NDUV analysers by causing a response similar to that of NOX. The manufacturer of the NDUV analyser shall use the following procedure to verify that quench effects are limited:

                     (i) The analyser and chiller shall be set up by following the operating instructions of the manufacturer; adjustments should be made as to optimise the analyser and chiller performance.

                     (ii) A zero calibration and span calibration at concentration values expected during emissions testing shall be performed for the analyser.

                     (iii) A NO2 calibration gas shall be selected that matches as far as possible the maximum NO2 concentration expected during emissions testing.

                     (iv) The NO2 calibration gas shall overflow at the gas sampling system's probe until the NOX response of the analyser has stabilised.

                     (v) The mean concentration of the stabilized NOX recordings over a period of 30 s shall be calculated and recorded as NOX,ref.

                     (vi) The flow of the NO2 calibration gas shall be stopped and the sampling system saturated by overflowing with a dew point generator's output, set at a dew point of 50 °C. The dew point generator's output shall be sampled through the sampling system and chiller for at least 10 minutes until the chiller is expected to be removing a constant rate of water.

                     (vii) Upon completion of (vi), the sampling system shall again be overflown by the NO2 calibration gas used to establish NOX,ref until the total NOX response has stabilized.

                     (viii) The mean concentration of the stabilized NOX recordings over a period of 30 s shall be calculated and recorded as NOX,m.

                     (ix) NOX,m shall be corrected to NOX,dry based upon the residual water vapour that passed through the chiller at the chiller's outlet temperature and pressure.

                   The calculated NOX,dry shall at least amount to 95 per cent of NOX,ref.

                  (e) Sample dryer

                  A sample dryer removes water, which can otherwise interfere with the NOX measurement. For dry CLD analysers, it shall be demonstrated that at the highest expected water vapour concentration Hm the sample dryer maintains the CLD humidity at ≤ 5 g water/kg dry air (or about 0.8 per cent H2O), which is 100 per cent relative humidity at 3.9 °C and 101.3 kPa or about 25 per cent relative humidity at 25 °C and 101.3 kPa. Compliance may be demonstrated by measuring the temperature at the outlet of a thermal sample dryer or by measuring the humidity at a point just upstream of the CLD. The humidity of the CLD exhaust might