A hydrogen leak originating from a tank within a high-pressure storage unit serving a hydrogen vehicle fueling station resulted in fire and explosion. Emergency responders were on scene within 7 minutes and contained the fire within 3hours. No damage was reported to the separate forecourt H2 dispenser or to other major station components within the station backcourt compound. No personnel injuries resulted directly from the fire and explosion -a nearby vehicle airbag triggered due to the explosion pressure, with minor injuries to the vehicle occupants. Immediately, until root cause was determined, all potentially affected H2 stations were idled.
The root cause of the incident was subsequently identified as an ASSEMBLY ERROR OF A SPECIFIC PLUG IN A HYDROGEN TANK IN THE HIGH-PRESSURE STORAGE UNIT.THE INNER BOLTS OF THE PLUG HAD NOT BEEN ADEQUATELY TORQUED. This led to a hydrogen leak, creating a mixture of hydrogen and air that ignited. The source of ignition has not been positively identified. An inspection and integrity verification program for the high-pressure storage units with similar plugs was implemented, including check and re-torque of tank plugs. Additional measures implemented include revised assembly, verification, and documentation procedures as well as increased automated leak detection frequency. Dependent on site, additional ignition control measures are considered, including loose gravel removal/smooth surface around the high-pressure storage unit, additional backcourt compound ventilation, and higher extent use of explosion-proof components.