Fire in a diesel distillation unit

A jet flame occurred in a diesel distillation unit.
It was caused by the release and ignition of hydrogen from the low-pressure (60 bar) section of a the unit. It occurred during maintenance works aiming at replacing the temporary seals with definitive ones, after which the discharge valve would have been re-opened and the compressor re-started.

The unit was depressurised and the emergency status was called.

The INITIATING cause was the fact that the discharge valve was not completely closed even though the panel control indicated that it was entirely closed.
The ROOT CAUSE could be attributed to a wrong design, which did not considered the possibility of a wrong signal on a critical component for safety.

Gasoil distillation unit , seals

Maintenance works were ongoing on the compressor on recycled gas circuit. Temporary seals had to be replaced by definitive seals.

The independent inspection required a root cause analysis and a detailed examination of the tightness of the automatic valve.

Rescue units were on site but they did not make an attempt to extinguish the fire to avoid the formation of a hydrogen cloud. The affected unit was depressurised. After 50 minute the leak was closed and the fire extinguished. Shortly afterward the alarm was terminated.

The plant operator modified the system controlling the opening of the affected valve during the maintenance works.