Document ID: chunk:federal_register_of_legislation:F2023L01526:body:0:p54
Version: federal_register_of_legislation:F2023L01526
Segment Type: other
Provision Reference: 
Character Range: 150996–153905

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 Annex 8, paragraph 2.4. 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 may be determined quarterly thereafter as long as no corrective action is required.

       2.3.1. The enclosure shall be purged until a stable hydrogen concentration is reached. The mixing fan is turned on, if not already switched on. The hydrogen analyser is zeroed, calibrated if required, and spanned.

       2.3.2. The enclosure shall be latched to the nominal volume position.

       2.3.3. The ambient temperature control system is then turned on (if not already on) and adjusted for an initial temperature of 293 K.

       2.3.4. When the enclosure temperature stabilizes at 293 K ± 2 K, the enclosure is sealed and the background concentration, temperature and barometric pressure measured. These are the initial readings CH2i, Ti and Pi used in the enclosure calibration.

       2.3.5. The enclosure shall be unlatched from the nominal volume.

       2.3.6. A quantity of approximately 100 g of hydrogen is injected into the enclosure.  This mass of hydrogen shall be measured to an accuracy of ±2 per cent of the measured value.

       2.3.7. The contents