Relief valve opening at a aerospace CGH2 storage system

During the development test of a booster, a 3000 psig (ca. 205 bar) relief valve actuated at the normal line pressure releasing gaseous hydrogen, which ignited, resulting in an explosion which damaged the test facility.

The INITIATING CAUSE was the premature activation of the pressure relief valve. This was due to the improper setting of the activation pressure. The ROOT CAUSE was an inadequate inspection procedure, and a CONTRIBUTING CAUSE was a poor design of the venting system which was installed in a horizontal position causing inadequate venting and build-up of static electricity.

relief valve, booster

The site needed to implement an effective inspection procedure, by checking all relief valve set points. As H2TOOLS puts it, a proper vent system design is as important as the relief valve itself. A venting system should be able to release hydrogen to the atmosphere at a safe location (the height above ground maybe even be prescribed by law) and done in a way to maximising the probability of hydrogen dispersion without ignition sources. A horizontal venting stack plaid a role as contributing cause also in the event HIAD_302, belonging as well to the collection of NASA mishaps.