Mooring Chain Breakage on GoM Platform

Abstract In 2023 a mooring chain breakage was discovered at the Titan platform in US waters in the Gulf of Mexico. Chain links, including the broken link, were then brought to shore for investigation. Hurricane Ida, which passed directly over the Titan platform in August 2021, is identified as the likely event starting the critical crack, whereafter continuous semi-fast fatigue crack growth caused the chain to break in a minor storm seven months later. A forensic study revealed the fracture mechanism and the mechanical properties of the steel, which is important for the understanding of the breakage mechanism. The fatigue-like breakage has a rough fracture surface without rest lines, similar to hydrogen assisted semi-fast crack growth confirmed to occur on high strength (R5 grade) chains used by drilling rigs. Together with the load history and time from likely crack start to breakage, a similar breakage mechanism to the hydrogen assisted high strength chain breakages is indicated. This was unexpected for R4 chain; however, the actual mechanical properties of the chain are not typical for R4, but similar to the breakage cases with high strength chains. The paper presents details of the breakage, the forensic investigation of the broken chain link, a discussion of similarities to high strength chain breakages, and the environmental load event, which likely lead to the breakage.