Detection alarm in compressor room of a mobile production facility

This event with minor hydrogen releases occurred during the operation of a hydrogen compressor.
The compressor was part of a mobile hydrogen production unit and connected to a bundle of cylinders with compressed hydrogen.
The room gas detector sent a firstly a low-level alarm (alarm setting value = 4,800 ppm of hydrogen in air) and the equipment was temporarily shut down. To identify the location of the leak, the equipment was restarted and checked. 15 minutes later, the detector triggered a major alarm (alarm setting value = 9,600 ppm) and the equipment was shut down. A gas reaction was confirmed from the compressor.

To identify the location of the leak, the upper, middle, and lower high-pressure compressor stages were disassembled and inspected.
Two leak locations were found:
(1) A penetration crack in the O-ring of the check valve on the discharge side of the left end cap of the high-pressure middle compressor. The two causes of this crack were a Blister phenomenon and a O-ring protrusion phenomenon due to deformation of the backup ring.
(2). A scratch in the circumferential direction on the seat surface of the pipe joint (retainer) on the suction side of the left end cap of the high-pressure lower compressor. The cause of the circumferential scratch was a damage caused by partial contact of a part with a harder hardness than the seat surface when repeatedly connecting and disconnecting the fitting.

[Note of HIAD validator: this event could be classified as near miss, if it were not for the bit unclear statement that a ‘reaction took place in the compressor’. It has now classified as a event with ignition, even if minor].

The INITIATING CAUSE was two leaks on the compressor components.
The ROOT CAUSE were probably to be attributed to material damage, possibly due to repeated use and/or installation mishaps.

Fittings

After the incident, the compressor was depressurised, a gas detection was performed, and after confirming that there was no reaction, it was sent to another facility for inspection and repair by the maintenance company.
The procedures for maintenance were improved with specific actions aiming at checking the integrity of the two subcomponents which failed, guaranteeing that these checks would be performed without risk of further damage.