Fire in the desulphurisation unit of a refinery

The accident occurred in the de-sulphurisation unit, and specifically on a pipeline at 50 bar, for the recycling of the hydrogen (containing hydrogen sulphide impurities). The pipe failed due to corrosion and the released hydrogen which ignited. The unit was containing 4000 kg of hydrogen, but it is not known if all of it was released.
The unit was stopped, de-pressurised and put under nitrogen.
Following the accidents, all other pipeline were controlled looking for anomalies.

The INITIATING cause was the failure of a hydrogen pipe due to corrosion. The accident investigation discovered that the part of the 100 mm diameter pipe which failed had a residual thickness of 2 instead of the nominal 6.3 mm.

The ARIA report (see references) does not mention any root cause, but judging by the deep corrosion, a lack of adequate inspection/maintenance can be postulated.

hydrogen recycling pipeline

Due to inner corrosion of a 100mm (DIN 100) pipe the wall thickness was reduced from 6.3 mm to 2 mm.

1 injury, no fatality. The injury was due to the fact that an employee who had just left the plant was startled by the bang of the explosion and suffered a sprained ligament in a sudden movement.

The material damage were estimated around 3 millions et 3 000 DM (ZEMA reports 2 Meuros + offside loss due to vehicle pollution in the employee parking lot).

Inside the plant, the air conditioning system in the control room was switched to recirculated air, the electrical power supply was switched off, the plant was depressurized, emptied and flushed with nitrogen. The plant fire brigade only used water as an extinguishing agent, mainly to cool plant components and to contain the fire. The extinguishing water was retained and only released for discharge after analysis.
Outside the facility, the road to the plant was cordoned off by the police as a precautionary measure and air quality measurements were taken in the surrounding area.

. Nevertheless, the fact that the pipe failed due to internal corrosion indicate a lack of fit-for-purpose inspection, able to detect material degradation on limited sections.

Following the accidents, all other pipeline were controlled looking for anomalies. Nothing is known on measures aiming at preventing the occurrence of similar cases in the future.

The sources do not report the