RR1072 Investigations into the immediate and underlying causes of failures of offshore riser emergency shutdown valves
Riser emergency shutdown valves (RESDVs) are an essential risk reduction measure for offshore installations and are a legal requirement under the Pipelines Safety Regulations 1996. RESDV failures, whether arising from a test or a real demand, are reportable to HSE under RIDDOR and a preliminary survey found approximately 180 cases of failure. Given the criticality of RESDVs to offshore safety, it was determined that the reasons for these occurrences should be investigated with a view to focussing inspection topics and identifying areas for future improvement across the industry.
Two themes have emerged from the causal analysis of RESDV failures: the age of the valves that failed, and the failure to learn and implement lessons from previous incidents. The three most common immediate causes were stated by dutyholders to be corrosion, the age of the RESDV and seizure/sticking.
Nearly half of failed RESDVs have had a previous failure, and over a quarter of failed RESDVs were brought back into service after cycling and/or lubricating the valves. The root cause of the failure needs to be determined and acted upon so that it does not recur, rather than just bringing the RESDV back into service.
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