Explosion and fire in a hydrogen compressors building

Hydrogen leaked from a hydrogen compressor and ignited, causing an explosion and a fire. The hydrogen fire further ignited roofing materials which had fallen down as the result of the explosion. 

The operator, who was outside the plant when the explosion occurred, pulled the emergency switch which shut down all the compressors. Although in a dazed condition, he then checked in the motor room that all the motors had stopped. He was subsequently taken to hospital where he was found without physical injuries but moderately shocked. 

After that the alarm was given, the plant fire team cut off the supply of hydrogen to the compressor. This stopped the flow of hydrogen.

The INITIATING CAUSE of the first explosion was attributed to the failure of the coupling of a pressure gauge, the associated pipe and the related isolating valve. This conclusion was based on the finding of this component on the floor near a wall. 

The ROOT CAUSE is of difficult attribution. All similar couplings were found properly installed. A better risk assessment during intrinsic safe design could have recognised that failure of this type of coupling had worse consequences than other types of high pressure joints, and could have taken additional preventive measures.

H2 compressor

The compressor involved had recently been overhauled and handed back to production on the day before the explosion. It ran satisfactorily for an hour before being shut down to fix clamps on the high pressure cooling coils which were vibrating. It was restarted on the following morning and ran without signs of trouble for a hour, when the explosion occurred.

Apart from the shocked operator, there were no other personnel injured. 

The explosion damaged (mainly superficially) roof and walls of the building, plant instrumentation and electrical wiring. Windows were broken in an adjacent building. 

The fire caused only minor damage in the vicinity of the affected compressor.

The fire alarm was raised by the gatekeeper who had heard the explosion and seen flames and smoke in the vicinity of the hydrogen plant. 

The works fire team were quickly on the scene but were advised not to extinguish the fire while hydrogen was still escaping, to prevent the likelihood of further explosion. 

The supply of hydrogen to the compression plant was cut off and the plant was electrically isolated before the arrival of the County Brigade. By the time they arrived, (within about seven minutes), the flow of hydrogen had stopped and the fire was quickly extinguished using water.

The post-incident investigation attributed the initial loss of confinement to the failure of the coupling between the compressor and a pressure gauge system consisting of the gauge itself, the connecting pipe and the isolating valve. All similar couplings were checked and found to be satisfactory. Nevertheless, it was noted that the failure of this type of joint has more serious consequences than failures of other types of high pressure joint. The possibility of higher risks for critical joints should be recognised and taken into account during initial safe design.