Analysis of a corrosion under insulation failure in a carbon steel refinery hydrocarbon line

Case Studies in Engineering Failure Analysis, Available online 11 October 2013, In Press, Accepted Manuscript Open Access
Analysis of a corrosion under insulation failure in a carbon steel refinery hydrocarbon line
W. Geary,
Health and Safety Laboratory, Harpur Hill Buxton Derbyshire, UK, SK17 9JN
Abstract
The catastrophic failure of an insulated 210 mm internal diameter pipe carrying hydrocarbons led to an explosion and fire at a refinery facility, the evacuation of the site and to millions of pounds worth of damage to a process vessel and associated plant. The investigation showed that the failure had occurred as a result of a corrosion under insulation (CUI) mechanism.
Water had entered the insulation system through a breach in the jacketing, made to accommodate a walkway support bracket. No adequate precautions had been made to weather-proof the insulation following the penetration of the jacket/insulation system.
Water, contaminated with sodium chloride and other pollutants, had migrated through the insulation and along the interface between the insulation and the pipe, forming a pool at the lowest point. The zinc and silicone acrylic pipe coating system had been consumed and corrosion of the carbon steel substrate had occurred at a rate consistent with published data.
The underlying causes of failure were identified as: a) a lack of adequate management controls over the insulation installation process and b), the lack of an adequate inspection regime to identify CUI in the period between installation and failure.
The incident resulted in heightened awareness of CUI issues on major hazard plant and increased regulator focus on this issue in all areas of ageing plant.
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