Fire at the desulphurisation unit of a refinery

The explosion occurred during preparatory work to start a compressor that supplies hydrogen gas to a heavy oil direct desulfurization unit. The inspection cover of the crank case came off, injuring an operator.
Normally, nitrogen was supplied to purge the case , displacing the hydrogen leaking from the shaft seal of the compressor cylinder. The accident investigation revealed that the nitrogen flow meter was broken, causing almost no gas to flow.
It is assumed that the hydrogen leaking from the shaft seal of the cylinder entered the crankcase, ignited and burned due to static electricity. The expansion force of the explosion caused the inspection cover of the crankcase to fly off.

The INITIATING CAUSE was the failing of the nitrogen system supposed to purge the compressor crankcase free of hydrogen.
The failure to purge was due to a broken flow metre which was indicating nitrogen flow while almost no nitrogen was flowing
The ROOT CAUSE was a lack of proper inspection and maintenance.

flow meter, shaft seal,
compressor cylinder,
crankcase,
H2 compressor

Preparatory operation was ongoing for the start of a hydrogen compressor

minor injury

This is an incident cause by the wrong indication of an instrument, which was a critical component of preventing measures of the system. Special attention should be given to the proper functioning of components critical to safety. Effective check/inspection shall be in place to detect early enough malfunctioning. Moreover, redundancy could be provided, for example by installing two components with the same function.