Document ID: chunk:federal_register_of_legislation:F2023L01530:body:0:p46
Version: federal_register_of_legislation:F2023L01530
Segment Type: other
Provision Reference: 
Character Range: 129033–131862

measured final pressure (MPa) at the end of the time interval, and Tf is the measured final temperature (°C).
         The average helium flow rate over the time interval is therefore
         VHe = (Mf-Mo) / Δt x 22.41 / 4.003 x (Ptarget/ Po)
         where VHe is the average volumetric flow rate (NL/min) over the time interval and the term Ptarget/ Po is used to compensate for differences between the measured initial pressure (Po) and the targeted fill pressure (Ptarget).
         Conversion of the average volumetric flow of helium to the average hydrogen flow is calculated with the following expression:
         VH2 = VHe / 0.75
         where VH2 is the corresponding average volumetric flow of hydrogen (that shall be less than the requirements in paragraph 7.2.1. of this Regulation to comply with).
         2. Post-crash concentration test for enclosed spaces
         The measurements are recorded in the crash test that evaluates potential hydrogen (or helium) leakage (Annex 5, paragraph 1. test procedure).
         Sensors are selected to measure either the build-up of the hydrogen or helium gas or the reduction in oxygen (due to displacement of air by leaking hydrogen/helium).
         Sensors are calibrated to traceable references to ensure an accuracy of ±5 per cent at the targeted criteria of 4 per cent hydrogen or 3 per cent helium by volume in air, and a full scale measurement capability of at least 25 per cent above the target criteria. The sensor shall be capable of a 90 per cent response to a full scale change in concentration within 10 seconds.
         Prior to the crash impact, the sensors are located in the passenger and, luggage compartments of the vehicle as follows:
              (a) At a distance within 250 mm of the headliner above the driver's seat or near the top centre the passenger compartment;
              (b) At a distance within 250 mm of the floor in front of the rear (or rear most) seat in the passenger compartment;
              (c) At a distance within 100 mm of the top of luggage compartments within the vehicle that are not directly affected by the particular crash impact to be conducted.
         The sensors are securely mounted on the vehicle structure or seats and protected for the planned crash test from debris, air bag exhaust gas and projectiles. The measurements following the crash are recorded by instruments located within the vehicle or by remote transmission.
         The vehicle may be located either outdoors in an area protected from the wind and possible solar effects or indoors in a space that is large enough or ventilated to prevent the build-up of hydrogen to more than 10 per cent of the targeted criteria in the passenger and luggage compartments.
         Post-crash data collection in enclosed spaces commences when the vehicle