ExxonMobil has been fined £267,000 after five leaks of extremely flammable hydrocarbons at its former Fife Ethylene Plant, including one the company knew about for around four months before it was fixed.
A damning report by the Health and Safety Executive (HSE) said the failures could have resulted in a "catastrophic event" and that measures to check for corrosion were "woefully inadequate".
ExxonMobil admitted numerous health and safety failings at Kirkcaldy Sheriff Court yesterday (Tuesday).
HSE inspector Lindsey Stein said: “At a site run by one of the biggest energy companies in the world, subject to the strictest controls, and processing high volumes of hazardous material, what our inspectors found beggars belief.
“The failure of ExxonMobil to properly inspect insulated pipework led to five separate leaks of highly flammable hydrocarbons, and while none of these leaks resulted in a catastrophic event, this was down to good fortune rather than good management."
HSE inspectors discovered a leak in May 2019 after detecting a strong smell of dimethyl sulphide during a routine visit to the plant, which is close to Cowdenbeath and Crossgates.
The company had first identified the leak on January 29 that year, meaning a mixture of ethane and dimethyl sulphide had been escaping from a pipe for around four-and-a-half months.
HSE issued a prohibition notice restricting access to the area, followed by an improvement notice requiring repairs. The leak was fixed in June 2019 after a bypass was installed.
Inspectors found the incident was not isolated.
Four other leaks of highly flammable hydrocarbons were identified at the Mossmorran plant between February 2018 and September 2019.
The first was a pinhole leak on a high-pressure pipe carrying dimethyl sulphide and ethane. It lasted about four months before being repaired.
In December 2018, a worker spotted a haze coming through insulation on another pipe. Corrosion had created four small holes and the leak continued for around six weeks, releasing an estimated 82 tonnes of hydrocarbons into the atmosphere.
A further pinhole leak was discovered in June 2019 on a pipe leading to the acetylene converter. Part of the plant was shut down for repairs and the leak lasted around two weeks.
The fifth was found in September 2019 during inspections required by HSE. It was on the same line as the December 2018 incident and was repaired after the pipe was purged.
All of the leaks were caused by corrosion under insulation, where water becomes trapped beneath protective covering and damages the pipework underneath.
HSE inspectors found overhead pipes were often assessed from ground level and insulation was not always removed to allow a full inspection.
Ms Stein said: “The arrangements in place to detect and prevent corrosion were woefully inadequate, and the consequences could have been far more serious.”
The company, registered at Fawley Refinery in Southampton, pleaded guilty to breaches of health and safety law.
A ship’s engineer suffered serious cold burns when liquid propane was released during loading operations in 2018, creating a flammable vapour cloud.
In April of the same year, ExxonMobil and Shell UK, who run the Fife NGL Plant next door at Mossmorran, were both served with final warning letters by Sepa for repeated episodes of unplanned flaring from their sites.
Fife Ethylene Plant stopped production in early 2026, after more than 40 years of operation.
ExxonMobil said the site was no longer commercially viable and it is now being decommissioned. Shell’s plant at Mossmorran remains operational.
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