Failure Analysis of a Welded Hydrocarbon Off-Shore Transmission Line Joint

A carbon steel joint on an offshore transmission line used to transport a mixture of water and hydrocarbons developed a leak while in service. Analysis of the leak site indicated that the joint exhibited corrosion attack at a weld joining a flanged end to the main body of the segment. Corrosion was accelerated by metallurgical conditions at the weld site and the environment formed by deposits and scale inside the pipe, which included naturally occurring radioactive material (NORM). The contribution of material and unique environmental factors to the preferential corrosion of the weld zone will be discussed in this case study.