A failure due to internal corrosion occurred on a lined sour gas pipeline. The pipeline was a steel pipeline installed initially with a polyamide liner in 2001 and then re-lined in 2003 with a high density polyethylene (HDPE) liner.

Neither of the liners had breached in service, yet corrosion behind the liner occurred and led to failure of the pipeline. The cause of the failure and the strategy to manage corrosion behind the liner in a lined pipeline is discussed.

The strategy involved the development of an attributes model, the use of a new inline inspection tool
along with changes to the operating and integrity reference plans of the lined sour gas pipelines.