A significant hydrogen leak occurred during refueling of the onboard hydrogen storage tank of a fuel cell-powered lift truck while it was completely depowered. The in-tank shutoff solenoid valve had recently been replaced, and this was the initial refueling event after the replacement. The fuel zone access panel was removed to allow constant visual leak checking with Snoop leak-detection fluid. The event occurred during the final pressure testing of the repaired system when an O-ring failed at approximately 4500 psi, releasing the entire contents of the hydrogen tank in about 10 minutes. The dispenser hose/nozzle was immediately disconnected, and the leak location was quickly isolated to the tank/valve interface. A 30-foot boundary around the lift truck was cleared of personnel and view more

During a facility walk-through, it was noted that a combustible gas (hydrogen) monitoring system installed in a furnace room was inoperable (the system had been unplugged). This system is used to detect and warn facility employees of an explosive or flammable environment. An explosive or flammable environment can only occur if there is a leak in the system, which would not be expected to occur during normal operations. When the system was reactivated, no leaks were indicated.

The incident had the following three causes:

A procedure describing administrative controls necessary to ensure safe operations in the area should have been developed and implemented prior to disabling the hydrogen monitoring system.
The hydrogen monitor was not hard-wired, which allowed it view more