Release from the dispenser of a refuelling station

The vent occurred at a hydrogen refuelling station (HRS) of a research laboratory (not public) serving heavy- and light-duty vehicle. The affected dispenser was a 700-bar dispenser for light-duty use supplied by an on-site gaseous storage of approx. 600 kg.
The leak occurred due O-ring extrusion and/or failure, on a medium-pressure manual isolation ball valve (normally open). The valve was connected to the end plug of a medium pressure tank. The failure of an O-ring created an external leak which could not be isolated.
The released quantity were small, in the 1 to 2 kg range. The leak was audible, but the hydrogen did not ignite and activated a safety sensor.
This leak occurred during the recommissioning of the medium pressure system following extended downtime and rebuild of a system that had been originally installed at a different facility.

The INITIATING CAUSE was the failure of a O-ring.
The ROOT CAUSE is related not only to a material failure, but also to the fact that the event occurred at the recommissioning of the medium pressure system, originally installed at a different facility, and after extended downtime. Ageing may have played a role in this case.

dispenser, valve, o-ring

This is a near-miss

The safety system worked as expected.