Hydrogen fire in a refinery

A hydrogen leak occurred on the hydrogen line of a hydrodesulphurisation unit, followed by ignition . The failure was located on a supply manifold of the unit at a support beam. The unit was shut down.

The accident was caused by external corrosion which had developed at a support point, under the pipe insulation. A regular thinning of the piping was observed over a length of 450 mm on the lower semi-circumference. The maximum thickness loss was 6.5 mm. The mechanical analysis concluded that the operating pressure was sufficient to cause this initial failure in the weakened area. Its propagation resulted from the dynamic load applied to the line.

INITIATING CAUSE was the thinning of the pipe wall caused by external, not further specified corrosion.

The ROOT CAUSE is not provided, but by proxy with similar cases, it could be concluded that lack of correct non-destructive assessment system did not allow for timely detection of the loss of wall thickness due to corrosion.

hydrogen pipeline, manifold

The unit was shutdown. Further emergency actions were not reported, but it is plausible that they were initiated.

Undetected external corrosion of high-temperature pipe connection is a common cause of loss of confinement. The presence of a thermal insulation layers around the piping does not allow for a visual inspection of the components, and in absence of sound non-destructive assessment tools and methods, the corrosion can proceed and reduce the load-bearing section of the pipe, until the internal pressure cause it burst. Similar cases are described, among others, by events HIAD_ 1067 and HIAD_83.