scope:

Description of Driving Event:

A three inch diameter stainless steel manifold containing hydrogen (0.27 lbs) and air (0.26 lbs) at 350 psia ruptured during experimental operation. The hardware was off-the-shelf, slightly modified, pre-safety checked and analyzed by the supply vendor. The test apparatus was in an altitude tank at simulated altitude conditions at the time of the mishap. Damage was restricted to the manifold and some of the experimental package valves.

The cause of the rupture was a detonation of an unplanned hydrogen and air mixture inside the manifold. A contributing factor was the deviation from preplanned test procedure by the test crew while attempting to make the device work.

The investigation team determined that the principal cause of the mishap was the lack of backflow prevention devices in the hydrogen and air supplies to the test package. That deficiency permitted the accumulation of the detonation charge within the manifold.