A study performed by DNV GL has shed light on how strength capacity of Mobile Offshore Drilling Unit (MODU) mooring systems relates to overall mooring system reliability; in short, it doesn’t.
Comparing failure rates from installations operating on the UK Continental Shelf (UKCS) to those operating on the Norwegian Continental Shelf (NCS), there is little change in the rate of single-line and multi-line failure despite increased strength requirements for NCS units. Read more about the study at this link:
It would be interesting to see similar data on failure rates of permanently moored floating production systems. Although there are distinct differences in mooring system design for permanent mooring systems compared to (temporary) MODU moorings, permanent moorings typically fail by means other than tensile overload and tension-tension fatigue to which they are primarily designed.
DNV GL recommends an increased focus on understanding past failures as the most effective method of improving mooring system reliability. Welaptega is actively performing in-service inspections and Mooring Fitness for Purpose Assessment (MFPA) projects in virtually every floating production region worldwide. We use this experience to identify risks of potential degradation and failure modes to other mooring systems operating in similar environments and under similar operating conditions.
Ask us how we can use our experience to provide greater confidence in your mooring integrity management.