Document ID: chunk:federal_register_of_legislation:F2023L01526:body:0:p55
Version: federal_register_of_legislation:F2023L01526
Segment Type: other
Provision Reference: 
Character Range: 153656–156642

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 of the chamber shall be allowed to mix for five minutes and then the hydrogen concentration, temperature and barometric pressure are measured. These are the final readings CH2f, Tf and Pf for the calibration of the enclosure as well as the initial readings CH2i, Ti and Pi for the retention check.

       2.3.8. On the basis of the readings taken in paragraphs 2.3.4 and 2.3.7 above and the formula in paragraph 2.4. below, the mass of hydrogen in the enclosure is calculated. This shall be within ±2 per cent of the mass of hydrogen measured in paragraph 2.3.6. above.

       2.3.9. The contents of the chamber shall be allowed to mix for a minimum of 10 hours. At the completion of the period, the final hydrogen concentration, temperature and barometric pressure are measured and recorded. These are the final readings CH2f, Tf and Pf for the hydrogen retention check.

       2.3.10. Using the formula in paragraph 2.4. below, the hydrogen mass is then calculated from the readings taken in paragraphs 2.3.7 and 2.3.9. above. This mass may not differ by more than 5 per cent from the hydrogen mass given by paragraph 2.3.8. above.

       2.4. Calculation

       The calculation of net hydrogen mass change within the enclosure is used to determine the chamber's hydrocarbon background and leak rate. Initial and final readings of hydrogen concentration, temperature and barometric pressure are used in the following formula to calculate the mass change.

       Where:

                     MH2 = hydrogen mass, in grams

                     CH2 = measured hydrogen concentration into the enclosure, in ppm volume

                     V = enclosure volume in cubic metres (m3) as measured in paragraph 2.1.1. above.

                     Vout = compensation volume in m³, at the test temperature and pressure

                     T = ambient chamber temperature, in K

                     P = absolute enclosure pressure, in kPa

                     k = 2.42

       Where: i is the initial reading

                     f is the final reading

       3. Calibration of the hydrogen analyser

       The analyser should be calibrated using hydrogen in air and purified synthetic air. See Annex 8, paragraph 4.8.2.

       Each of the normally used operating ranges are calibrated by the following procedure:

       3.1. Establish the calibration curve by at least five calibration points spaced as evenly as possible over the operating range. The nominal concentration of the calibration gas with the highest concentrations to be at least 80 per cent of the full scale.

       3.2. Calculate the calibration curve by the method of least squares. If the resulting polynomial degree is greater than three, then the number