Document ID: chunk:federal_register_of_legislation:F2023L00129:reg:13:p32
Version: federal_register_of_legislation:F2023L00129
Segment Type: reg
Provision Reference: reg 13 (pt 32/56)
Character Range: 385150–387919

between 15 and 50 per cent of full scale for each calibration incorporating a gas divider. An additional verification may be performed using another calibration gas, if the first verification has failed.
 Optionally, the blending device may be checked with an instrument which by nature is linear, e.g. using NO gas with a CLD. The span value of the instrument shall be adjusted with the span gas directly connected to the instrument. The gas divider shall be checked at the settings used and the nominal value shall be compared to the measured concentration of the instrument. This difference shall in each point be within ±1 per cent of the nominal value.
 For conducting the linearity verification according to paragraph 9.2.1., the gas divider shall be accurate to within 1 per cent.
9.3.3.4. Oxygen interference check gases
 Oxygen interference check gases are a blend of propane, oxygen and nitrogen. They shall contain propane with 350 ppm C  75 ppm C hydrocarbon. The concentration value shall be determined to calibration gas tolerances by chromatographic analysis of total hydrocarbons plus impurities or by dynamic blending. The oxygen concentrations required for positive ignition and compression ignition engine testing are listed in Table 8 with the remainder being purified nitrogen.
              Table 8
              Oxygen interference check gases
Type of engine                     O2 concentration (per cent)
Compression ignition               21 (20 to 22)
Compression and positive ignition  10 (9 to 11)
Compression and positive ignition  5 (4 to 6)
Positive ignition                  0 (0 to 1)

9.3.4. Leak check
 A system leak check shall be performed. The probe shall be disconnected from the exhaust system and the end plugged. The analyzer pump shall be switched on. After an initial stabilization period all flowmeters will read approximately zero in the absence of a leak. If not, the sampling lines shall be checked and the fault corrected.
 The maximum allowable leakage rate on the vacuum side shall be 0.5 per cent of the in-use flow rate for the portion of the system being checked. The analyzer flows and bypass flows may be used to estimate the in-use flow rates.
 Alternatively, the system may be evacuated to a pressure of at least 20 kPa vacuum (80 kPa absolute). After an initial stabilization period the pressure increase p (kPa/min) in the system shall not exceed:

 p = p / Vs  0.005  qvs (71)
 Where:
Vs is the system volume, l
qvs is the system flow rate, l/min
 Another method is the introduction of a concentration step change at the beginning of the sampling line by switching from zero to span gas. If for a correctly calibrated analyzer after an adequate period of time the reading is ≤  99 per cent compared