Document ID: chunk:federal_register_of_legislation:F2023L01530:body:0:p44
Version: federal_register_of_legislation:F2023L01530
Segment Type: other
Provision Reference: 
Character Range: 124163–126935

compressed hydrogen storage system leak test
         The crash tests used to evaluate post-crash hydrogen leakage are those set out in paragraph 7.2. of this Regulation.
         Prior to conducting the crash test, instrumentation is installed in the hydrogen storage system to perform the required pressure and temperature measurements if the standard vehicle does not already have instrumentation with the required accuracy.
         The storage system is then purged, if necessary, following manufacturer's directions to remove impurities from the container before filling the storage system with compressed hydrogen or helium gas. Since the storage system pressure varies with temperature, the targeted fill pressure is a function of the temperature. The target pressure shall be determined from the following equation:
         Ptarget = NWP x (273 + To) / 288
         where NWP is the Nominal Working Pressure (MPa), To is the ambient temperature to which the storage system is expected to settle, and Ptarget is the targeted fill pressure after the temperature settles.
         The container is filled to a minimum of 95 per cent of the targeted fill pressure and allowed to settle (stabilize) prior to conducting the crash test.
         The main stop valve and shut-off valves for hydrogen gas, located in the downstream hydrogen gas piping, are in normal driving condition immediately prior to the impact.
         1.1. Post-crash leak test: compressed hydrogen storage system filled with compressed hydrogen
         The hydrogen gas pressure, P0 (MPa) and temperature, T0 (°C) are measured immediately before the impact and then at a time interval, Δt (min), after the impact. The time interval, Δt, starts when the vehicle comes to rest after the impact and continues for at least 60 minutes. The time interval, Δt, shall be increased, if necessary, to accommodate measurement accuracy for a storage system with a large volume operating up to 70MPa; in that case, Δt is calculated from the following equation:
         Δt = VCHSS x NWP /1,000 x ((-0.027 x NWP +4) x Rs – 0.21) -1.7 x Rs
         where Rs = Ps / NWP, Ps is the pressure range of the pressure sensor (MPa), NWP is the Nominal Working Pressure (MPa), VCHSS is the volume of the compressed hydrogen storage system (L), and Δt is the time interval (min). If the calculated value of Δt is less than 60 minutes, Δt is set to 60 minutes.
         The initial mass of hydrogen in the storage system is calculated as follows:
         Po' = Po x 288 / (273 + T0)
         ρo' = –0.0027 x (P0')2 + 0.75 x P0' + 0.5789
         Mo = ρo' x VCHSS
         The final mass of hydrogen in the storage system, Mf, at the end of the time interval, Δt, is calculated as follows:
         Pf' = Pf x 288 / (273