Failure analysis of fuel supply pipeline

The paper presents the results of a failure investigation carried out on a 52 km long 16″ spiral welded API 5L-X52 fuel supply pipeline. The pipeline supplies liquid fuel from a refinery to a power station. Although there has been a history of external corrosion failures due to coating defects/intermittent cathodic protection problems, a thick wall failure without any indication of external corrosion occurred 100 m away from the power station. The failure of the pipeline was due to delayed cracking as a result of a pre-existing mechanical damage, possibly aided by hydrogen-assisted cracking in the highly strained region under the damaged coating. The fuel properties or the weld were not responsible for the failure. In fact, the spiral weld was found in sound condition.