Fire from a flange with a wrong seal at a solvent manufacturing plant

The hydrogen fire occurred at a solvent manufacturing plant. Hydrogen leaked from a flange of a hydrogen supply pipe and ignited inside the thermal insulation around the pipe. This first fire was relatively small, but it damaged the gasket of another flange with which the first flange shared the thermal insulation, causing a much larger hydrogen release which contributed spreading the fire.

The reason for the first leak was a gasket with the wrong size. The gasket was regularly replaced, during the periodic maintenances exchanging catalyst. The last time, a smaller than the standard one was installed. It could not withstand the hydrogen pressure during the operation.

Damage was limited only to the initiating area of the fire, thanks to the a timely intervention which replaced hydrogen with nitrogen in the pipe.

The INITIATING/direct cause was a mistake during maintenance, which brought to install the wrong flange gasket.
This could be attributed to human error or shortcoming in the management of the periodic turnaround shutdowns, specifically the material- and parts-handling management.

gaskets, thermal insulation, fhanges

The operation was ongoing as expected, the leakage was the effect of a mistake occurred at the previous turnaround shutdown.

Damage was limited only to the immediate area of the fire

The plant was shut down urgently and employees carried out initial fire fighting and nitrogen substitution.
The hydrogen in the leaking section of the pipe was replaced with nitrogen.

(i) In case of fires fed by a considerable amount of hydrogen, it is crucial for a successful fire-fighting to be able to stop the leak. Otherwise, mitigating measures from outside risk to have limited effect.
(ii) As in the case of event 038, the affected flange passed the leak test. This test is too short and not executed under the same conditions experienced by the flange during operation.
(iii) Thermal insulations around pipes hinders the early discovery of damages or leaks.

(1) To prevent the use of the wrong gaskets, the management of the maintenance and turnaround shutdown procedures was improved.
(2) To detect a gas leak inside thermal insulation, inspection windows were installed on thermal insulation and the gas leak checks were strengthened.
(3) The flange construction itself was improved.