Mooring integrity management: preventing mooring line failures

Over the last 15 years there have been several multi-million pound failure incidents of permanent mooring systems for Floating Production Units (FPUs). Some of these incidents resulted in vessel drifting, riser ruptures, production shutdown and hydrocarbon releases. Mooring components are subjected to numerous forms of degradation caused by the harsh ocean environment and years of cyclical tension loading. Efforts in the O&G sector to aggregate failure data, show that causes of failure can vary depending on the geographical location, the mooring component type and its position within the mooring line. Experiences like these have led to a consensus amongst operators that there is a need to improve the reliability of permanent mooring systems through improvement in mooring integrity management (MIM). This need for a focus on the installation and long-term degradation management of mooring systems is also becoming increasingly important in the floating wind sector. Mooring analysis alone is not sufficient to guarantee long term mooring reliability. This is achieved through effective implementation of a MIM plan that considers all lifecycle phases – i.e. risks associated with design, manufacturing, installation and operation. This presentation will expand on the key principles in the up-coming DNV GL MIM Recommended Practice(RP) which is expected to be issued in 2021 and is intended to help mooring designers and floating platform operators (in O&G or wind) to improve the reliability, availability and safety of the mooring systems, whilst creating the potential to reduce inspection costs over the lifecycle of their asset. Speakers: Alex Argyros, Lead Naval Architect, Fixed and Floating Structures DNV GL