HSE Probes Mossmoran Plant Corrosion Risks
ExxonMobil Chemical Limited has been ordered to pay £267,000 after an investigation by the Health and Safety Executive (HSE) uncovered multiple leaks of highly flammable hydrocarbons at its Fife Ethylene Plant near Kirkcaldy. The prosecution highlights systemic failures in managing corrosion risks on insulated pipework at a facility classified as an Upper Tier site under the Control of Major Accident Hazards (COMAH) Regulations.
The regulatory enforcement action follows a routine site inspection conducted by HSE personnel on 21 May 2019. During the visit, inspectors detected a potent smell of dimethyl sulphide (DMS), a hazardous and highly flammable substance capable of causing severe skin and eye irritation. Plant operators subsequently acknowledged that both DMS and ethane were actively leaking from an overhead pipe—an issue that site management had been aware of for approximately four months without taking effective remedial action.
Systemic Failures and Corrosion Under Insulation
Subsequent inquiries by the HSE revealed that the initial discovery was not an isolated incident. Investigators uncovered concrete evidence of five distinct leaks of extremely flammable hydrocarbons occurring between February 2018 and September 2019. All identified failures were directly attributed to Corrosion Under Insulation (CUI).
The safety breaches involved critical dimethyl sulphide and ethane distribution lines. In several instances, hazardous leaks were allowed to persist unchecked for weeks or even months while the high-hazard facility remained fully operational. For example, the first recorded leak originated on 23 February 2018 when a pinhole defect manifested on a high-pressure DMS line operating at 115°C. This specific line continued to leak unhindered for roughly four months prior to permanent repairs being executed. A secondary leak was later uncovered in December 2018 after a plant worker noticed a suspicious vapour haze emerging through degraded insulation during unrelated maintenance activities.
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Regulatory Enforcement and Industry Takeaways
The HSE's findings underscore the critical importance of rigorous inspection regimes, particularly for high-consequence industrial facilities handling volatile substances. Under COMAH regulations, upper-tier sites are held to strict standards regarding plant integrity and preventive maintenance. Failing to address known defects, such as corrosion under insulation, substantially elevates the risk of catastrophic loss of containment, fire, or explosion.
Safety regulators across the UK continue to clamp down on organisations that neglect routine maintenance or fail to act upon internal safety reports. Employers and duty-holders are reminded that comprehensive risk profiling, proactive asset management, and robust employee training remain non-negotiable elements of safe industrial operations. Ensuring that workforces are adequately trained to identify and report plant anomalies can prevent minor maintenance issues from escalating into major regulatory prosecutions. For comprehensive guidance on workplace compliance, risk assessment strategies, and accredited safety training programmes, organisations can visit Abertay Training at https://www.abertaytraining.co.uk