Hydrogen release and explosion on a compressor of a refinery

An explosion took place at the hydrodesulphurisation unit of a refinery's crude oil.
It was caused by a leak at the suction line of a hydrogen compressor used for the re-circulation of the hydrogen required for the desulphurisation process. The compressor was in a room without ventilation, the hydrogen cumulated there creating an explosive mixture which ignited.

The unit's alarm was immediately triggered in the control room and the operator activated the internal emergency plan. The site's firefighting team went to the site and brought the following fire under control. The external fire fighters service did not need to intervene.

The accident caused two fatalities and five injuries among the workers. According to one of the sources, the plant supervisor sent personnel to investigate. it is not clear if this was the cause of the fatalities and injuries. The explosion was heard at 12 km distance.
The operation of the unit affected by the accident were stopped as well as the neighbouring thermal cracking unit, while the operation of 30 units of the refinery have continued their operation.

The INITIATING CAUSE was a hydrogen leak on a compressor for the re-circulation of the hydrogen.
The leaking element was a gasket on the suction line of the compressor, which had been installed at the commissioning of the facility, 9 years before, and had never been inspected or replaced.
The consequences of the leak and ignition were serious, because the explosion occurred in a confined space.

To the ROOT CAUSE contributed factor such as:
(1) failing to inspect and maintain critical components,
(2) ill design of the compressor room,
(3) lack of safety awareness among personnel and the management.
The origin of all this was probably a lack of proper risk assessment and proper safety management.

seal, compressor

Thedamage to the facility was cosniderable, but the costs are unknown.
The thermal cracking unit restarted eight days after the accident. The supply of fuel in the region of north Mexico was not affected, but the daily production of sulphur and gasoline was reduced until the restart of the hydrodesulphurization unit sever weeks later.

An internal investigation committee was set up to find the root cause of the accident. The administration in charge of environmental protection opened an investigation to define the preventive measures that the operator must put in place to avoid this type of accident.

The results of these investigations were not shared in the public space.

The site's firefighting team went to the site, brought the fire under control and rescued the affected workers. The external fire fighters service did not need to intervene.

In absence of publicly available conclusion of the investigation, the following recommendations can be drawn on the facts known:

(1) A risk assessment is necessary for all area where hydrogen is produced and handled, with specific focus on confined and semi-confined spaces where hydrogen can accumulate and explode
(2) Improve the diagnostic systems, so that alarm signals (for example on gas detection and fires) can be easily distinguished from signals carrying operative information. This will help in timely understanding what is going on in the control room.
(3) Training of personnel must be organised around safety topics, such as gas safety, emergency procedures, and the level of personnel awareness on safety aspects has to be measured and maintained (no one-off training but a full lifetime programme).