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Stored pressure: Corrosion coupon plug ejected from pressurised pipeline

The International Association of Oil and Gas Producers (IOGP) has published a safety alert regarding an incident in which a corrosion coupon plug was ejected from a pressurised pipeline. The incident occurred during a ‘routine’ plug retrieval operation on a 28″ crude oil pipeline. The plug was ejected at high velocity from a 2″ access fitting on the pipeline. The pipeline was pressurised to 103 bar. There was a spillage of crude oil from the pipeline via the access fitting. There were no injuries.

Investigation revealed that the most likely cause was that the threads of the access fitting were worn down and unable to restrain the plug against 103 bar of pressure. The access fitting was nearly thirty years old and had been subject to over 140 coupon retrieval and installation cycles.

Further information is available at

The following two incidents, relating not to stored pressure release or to pipelines, but to worn-out threads, may be of interest to members:

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