Essar Oil UK has been fined £1.65m following an explosion at its Stanlow refinery in Ellesmere Port, Cheshire.

Liverpool Crown Court heard that while there were no injuries, the blast in the early hours of 14 November 2013 caused internal structures to collapse and damage totalling more than £20m.

Problems started at the site during the start-up of its main distillation unit, when extremely flammable hydrocarbons were allowed to enter an unignited furnace. The heat from another furnace nearby triggered the explosion which destroyed the furnace, starting a number of fires which the Fire Service had to bring under control.

The incident was reported to the EU as a major accident under schedule 7 of the Control of Major Accident Hazards (COMAH) Regulations 1999.

A Health and Safety Executive (HSE) investigation found that Essar had failed to take all measures necessary to prevent or mitigate a major accident. There were three key failings in this case:

• A safety critical valve was ordered and installed incorrectly and Essar failed to correctly validate its operation;

• Essar failed to adequately assess the installation of a new safety critical trip as they failed to recognise the system had a by-pass line which defeated the trip’s operation; and

• Essar’s policy was to isolate main fuel lines to the furnace, however the hydrocarbons entered the furnace via a secondary fuel line which had not been isolated when shut down.

Essar pleaded guilty to breaching Regulation 4 of the Control of Major Hazards Regulations 1999 and was fined £1,650,000 with costs of £57,644.80.

Speaking after sentence, HSE principal inspector Joanne Eccles said: “The industry should take notice of this case. There were no injuries but mistakes were made and could have been prevented.”