CRA clad pipes: Do their benefits justify sole selection?
Ahmed Reda, Mohammad Zam Zam Noor, Ali Karrech
Abstract
This article presents a case study of a gas leak at a girth weld on a subsea spool. The leak occurred 14 days after the pipeline’s start-up. The pipeline in question was a 36-inch corrosion-resistant alloy (CRA) clad pipeline, with a carrier pipe made of X65 steel and a 3 mm layer of alloy 825. The girth weld was performed using alloy 625. The leak occurred at the girth weld between the riser and the tie-in subsea spool. The failure was attributed to excessive misalignment, which was unavoidable and evident in radiographic testing (RT). To pass the girth weld in terms of quality control, the welder ground the area around the root where the highest misalignment was located, inadvertently grinding through the CRA clad layer and exposing the carbon steel directly to sour gas. The pipeline had been installed and left in a preservation mode using treated inhibited seawater for several years. It was later dewatered, conditioned, and purged before introducing the wet sour gas. Fourteen days after the start-up, the pipeline ruptured, as discussed in this article.