Severity
Incident
Leak
Yes
Ignition
Yes

Incident Synopsis
A technician was welding a cable suspended over a stainless steel H2 instrument line. During the welding process, two holes were accidentally burned through the hydrogen tubing. The operator heard a hissing sound and closed the valve, but the hydrogen had already ignited and it burned his hand while he was feeling for a leak.

Cause
A short during welding caused the pinholes in the tubing containing the gaseous H2.

Incident Date
Dec 31, 1969
Setting
Equipment
  • Piping/Fittings/Valves
  • Piping
  • Electrical Equipment
  • Hand Tools
  • Crafts Tools
Damage and Injuries
When Incident Discovered
Lessons Learned

Because of the near invisibility of a hydrogen flame in daylight and hydrogen's extremely low ignition coefficient, if a known leak is present (e.g., an audible hissing), ignition should always be presumed. The primary cause of this incident derives from the technician improperly performing hot work in the vicinity of a charged flammable gas line. Given the location of the flammable gas line, an alternative to performing hot work or relocating the hot work should have been considered. If such work was necessary at this location, it should have been performed only after the gas supply was verified closed (along with a lock and tag). Also, if this latter option was chosen, then the system should be checked for leaks prior to turning the gas back on.