Pipe explosion at a hydrogen production unit in a refinery

A fire broke out at a pipe of the hydrogen production unit, belonging to the steam methane reformer part of the fluidised catalytic cracking (FCC) plant. The fire occurred when personnel of a contracting company were executing preparing maintenance works. For this, they had to open a hydrogen-carrying pipe at a flange and blind both opening with bolted steel plate. The pipe was still containing residual hydrogen, which ignited when the pipe was opened.

Valves connected to the affected pipe were shut off. Fire authorities mobilized 25 personnel and 23 pieces of equipment to extinguish the blaze, which was fully contained approximately 20 minutes later. After suppression, further efforts were continued by spraying water on the pipeline to avoid secondary accidents.

The INITATING CAUSE was the opening of a hydrogen pipe containing still residual hydrogen.

The results of the legal investigation are not (yet) known and still several questions are open. Why was there was still hydrogen in the pipe? Was this the result of a wrong purge, or was the wrong pipe to be maintained? Were the actions under the exclusive responsibility of the subcontractor, or was the plant management responsible for unclear instruction and process?

pipe, flange