HSE/NW/057/08 12 March 2008

Shell UK oil products Ltd fined £266,681 after highly flammable and toxic gas escaped through corroded pipe

Shell UK Oil Products Limited had a ‘narrow escape’ after 20 tonnes of a highly flammable and toxic gas escaped through a corroded pipe at their Stanlow Manufacturing Complex, Ellesmere Port, Cheshire, but dispersed without exploding.

The Health and Safety Executive’s message to all companies is to ensure that robust maintenance is carried out to prevent corrosion of pipes, which was the cause of this incident.

Shell UK Oil Products Limited pleaded guilty to failing to comply with the duty imposed by Regulation 4 of the Control of Major Accident Hazards Regulations 1999 (as amended) to take all measures necessary to prevent major accidents, by its failure to contain a flammable toxic gas.

The company were fined £266,681 and ordered to pay £37,131.62 costs at Chester Crown Court, for the incident, which happened on 29 May 2003, when 20 tonnes of isobutane (LPG), mixed with 150 kg of hydrogen fluoride escaped into the atmosphere from the release from the HF Alkylation plant.  Because of the quantities released, the incident was reported to the European Commission as required by the Control of Major Accident Hazards Regulations 1999 (as amended).

Health and Safety Executive experts inspected the site after the incident and concluded that Shell had lost control of corrosion processes within the pipe to such an extent that a failure became inevitable.

Shell, in one of its own reports, estimated that such an incident could have resulted in multiple fatalities and damage to buildings over a significant area and secondary explosions could have resulted in a major fire leading to catastrophic damage.

Health and Safety Executive Inspector Alan Graham said: "This was a major incident which placed many company employees and others at risk from an escape of a flammable toxic gas. The incident happened when a pressure relief pipe corroded to such an extent that it fractured. Although there was no ignition on this occasion, in different circumstances there could have been an explosion.

"It was the Health and Safety Executive’s case that the gas escape was caused by Shell’s failure to properly inspect and maintain the pipe. This failure caused a jet of gas, which formed a cloud, which was seen to drift 10 - 15 metres above the site. The gas cloud was kept under observation until it dispersed."

Justin McCracken, HSE's Deputy Chief Executive said: "This case illustrates the importance of having effective maintenance regimes for plants dealing with hazardous substances and processes. They should include the prevention of corrosion and the careful monitoring of the state of all safety critical equipment, including pipe work. The company was lucky that this incident did not have very severe consequences."

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