Document ID: chunk:federal_register_of_legislation:F2023L01529:body:0:p43
Version: federal_register_of_legislation:F2023L01529
Segment Type: other
Provision Reference: 
Character Range: 119482–122381

temperature of 293 K.  This nominal volume shall be repeatable within ±0.5 per cent of the reported value.

       2.1.2. The net internal volume is determined by subtracting 1.42 m3 from the internal volume of the chamber.  Alternatively the volume of the test vehicle with the luggage compartment and windows open or REESS may be used instead of the 1.42 m3.

       2.1.3. The chamber shall be checked as in paragraph 2.3. of this annex.  If the hydrogen mass does not agree with the injected mass to within ±2 per cent then corrective action is required.

       2.2. Determination of chamber background emissions

       This operation determines that the chamber does not contain any materials that emit significant amounts of hydrogen.  The check shall be carried out at the enclosure's introduction to service, after any operations in the enclosure which may affect background emissions and at a frequency of at least once per year.

       2.2.1. Variable-volume enclosure may be operated in either latched or unlatched volume configuration, as described in paragraph 2.1.1. above. Ambient temperature shall be maintained at 293 K ± 2 K, throughout the four-hour period mentioned below.

       2.2.2. The enclosure may be sealed and the mixing fan operated for a period of up to 12 hours before the four-hour background-sampling period begins.

       2.2.3. The analyser (if required) shall be calibrated, then zeroed and spanned.

       2.2.4. The enclosure shall be purged until a stable hydrogen reading is obtained, and the mixing fan turned on if not already on.

       2.2.5. The chamber is then sealed and the background hydrogen concentration, temperature and barometric pressure are measured. These are the initial readings CH2i, Ti and Pi used in the enclosure background calculation.

       2.2.6. The enclosure is allowed to stand undisturbed with the mixing fan on for a period of four hours.

       2.2.7. At the end of this time the same analyser is used to measure the hydrogen concentration in the chamber.  The temperature and the barometric pressure are also measured.  These are the final readings CH2f, Tf and Pf.

       2.2.8. The change in mass of hydrogen in the enclosure shall be calculated over the time of the test in accordance with paragraph 2.4. of this annex and shall not exceed 0.5 g.

       2.3. Calibration and hydrogen retention test of the chamber

       The calibration and hydrogen retention test in the chamber provides a check on the calculated volume (paragraph 2.1. above) and also measures any leak rate.  The enclosure leak rate shall be determined at the enclosure's introduction to service, after any operations in the enclosure which may affect the integrity of the enclosure, and at least monthly thereafter.  If six consecutive monthly retention checks are successfully completed without corrective action, the enclosure leak rate