Hydrogen line leakage in a metal production plant

In a metal production company, a leak occurred on valve of a hydrogen line. A new valve was ordered. Almost one month later workers arrived on site to replace the valve. After one hour they heard an explosion. Two men went to investigate and saw flames coming from the hydrogen pipe that was being repaired. They ran outside to isolate the hydrogen line
One worker had burnt his arm.
The hydrogen regulator was burnt and a new one had to be fitted.

The INITIATING CAUSE was the leak of a hydrogen valve during replacement.
CONTRIBUTING CAUSE was the fact that the workers fitted the new regulator and valve, but did not test the tightness of the new installation because the pipe was too hot. This hint as well to a lack of good procedures.

Hydrogen line, valve, regulator.

One month before the incident, a valve started leaking. The incident occurred when contractor's workers were on site to replace it.

Two workers ran outside to isolate the hydrogen. When returning to the scene of the event, they found a colleague had suffered burns to the arms.