Incident Synopsis
During a standard testing procedure, a 3,000 psig relief valve actuated at normal line pressure, releasing gaseous H2. The gaseous H2 combined with air, resulting in an explosion which damaged the test facility.

The relief valve was improperly set to open at line pressure, and the inspection was inadequate in that it didn't identify this error. Contributing cause was poor design of the venting system, which was installed in a horizontal position, causing inadequate venting and buildup of static electricity.

Incident Date
Dec 31, 1969
  • Piping/Fittings/Valves
  • Valve
  • Ventilation System
  • Venting System
Damage and Injuries
When Incident Discovered
Lessons Learned

The site needs to implement a good Operational and Readiness Inspection procedure. System inspection deficiencies need to be identified, and (if possible) reviewed by a second party before future tests are conducted. This inspection could include the following:

Check all relief valve set points
Check potential design flaws
Check all other relevant operational characteristics

A proper vent system design is as important as the relief valve itself. A vent system should be able to operate with no consequence at all. Proper facility design and venting to a safe location would have made this a near-miss instead of an incident.