Multiple failures of API 5L X42 natural gas pipeline

This paper discuss the failure analysis of API 5L X42 (NPS8) coal-tar coated natural gas feeder line. Three separate pin holes with difference sizes were observe on the pipe surface facing leaked water pipe dismisses the possibility of corrosion as the cause of the failure. Site investigation, soil sampling and physical inspection performed to identify the cause of the pipe failures. The investigations revealed that the NPS8 gas pipe failures was caused by the failure of weld joint of underneath water pipe which produced high pressure water jet impacting the natural gas pipeline as well as entraining the surrounding sand particles causing erosion to the natural gas pipeline.