scope:

Description of Driving Event:

At the White Sands Test Facility (WSTF) a burst disc on a high pressure (9700 psi) oxygen system ruptured at 5700 psi, well below the system and rated pressure of the disc. Ignition of the vent system downstream of the burst disc occurred, partially destroying it. The burst disc was a safety relief device placed in an oxygen recharger pumping system and was subjected to rapid cyclical pressure pulses during recharging operations. It was concluded that the cycling fatigued the burst disc metal much more rapidly than would be expected in a static system application. Although the exact source of the ignition is not known, it was assumed that either particles from the ruptured disc or accumulated debris from the oxygen pumping system impacted the vent system in the presence of the high pressure oxygen that flowed past the ruptured disc. This served as an ignition source for the base vent material (stainless steel) fire, which progated until the venting oxygen pressure fell below the level that would support combustion. The fire then self-extinguished. The design of the vent line was changed to place the burst disc very near the end of the vent line, exterior to the facility, and with the discharge oriented away from personnel access areas. In-line particle filters were relocated closer to the oxygen source to reduce the probability of debris exiting at high velocity from the vent system if a burst disc rupture occurs. All WSTF high pressure oxygen vent system designs were reviewed and two additional systems of similar configuration were eliminated (they were no longer needed).