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The Santa Clara transfill facility supplies gaseous hydrogen (GH2) at 517 barg (7500 psig) and near-ambient temperature to high pressure tube trailers for delivery to retail fuelling stations. At the time of the incident, in Bay#3, a duel-module tube trailer with a total GH2 capacity of 500kg (1102lb) was being filled by 2 drivers (a trainer and a trainee). Both modules were being filled simultaneously using the automated fill system. When both modules were almost full, the trainee noticed a GH2 leak and reported it to the trainer who instructed the trainee to stop filling that module. However, the trainee stopped the filling process for both the modules and did not uncouple the trailer from the fill system. The trainer then isolated the front module fill line, depressed the fill manifold, and removed a pipe spool. He soon realised he did not have all the required materials so instructed the trainee to shut off the GH2 supply. The trainee misunderstood and pressed a ‘purge/enable trailer’ button which opened all pneumatic valves on the trailer, inadvertently restarting the fill process. GH2 escaped from the open-ended pipe spool. The GH2/air mixture ignited within 3 seconds, causing a deflagration explosion followed by a jet fire. The trainer immediately pressed the emergency stop button. All pneumatic valves on the trailer closed either by this action or by plastic air supply lines melting. The explosion and jet fire caused additional leaks which escalated the fire.
Ask yourself and your crew:
- How can something like this happen here (e.g. on our site)?
- What safety measures (i.e. procedures, controls/barriers) do we have in place to mitigate the risk?
- How do we know the risk controls/barriers are working?
- What improvements or changes should we make to the procedures, controls/barriers or the way we work?
Original content courtesy of IChemE Safety Centre
