Mooring systems are designed to last for long periods of time (generally 10 to 30 years) in extremely challenging environments. Between tropical cyclones, accelerated corrosion, and constant fatigue loads, every operating region faces major challenges for continuous operation without failure. Mooring design guidance is equally robust to meet these challenges. Software packages accurately simulate mooring loads, components are manufactured with higher strength and fatigue capacities, and design guidance is being updated to reflect new failure modes.
So why do failures of permanent mooring systems happen at such an alarming rate (approximately 30 times more than the industry target according to OTC 24025)?
In most cases, mooring systems fail because they face conditions outside of their intended design envelope. Despite mooring designs being exceptionally sophisticated, the analysis methods and safety factors are invalid when certain assumptions and parameters of operation are not met.
Maintaining mooring integrity for extended periods of time requires monitoring and inspection to ensure that moorings are operating within their intended design envelope. This requires feedback cycles that compare actual operating conditions and degradation to design parameters and assumptions. Also, analysis must be performed when the operating conditions are not consistent with the original design case.
Three integral aspects of maintaining mooring integrity for extended periods of time:
Monitor design input/output parameters to ensure that design assumptions and predictions, including line tensions (or line angles), vessel excursions, and metocean conditions, are valid.
Inspect to ensure that components remain undamaged, deteriorate at anticipated rates, and function according to assumptions of the design.
Perform Engineering Analysis when the mooring system is operating outside out of the intended design envelope to ensure that it still meets allowable excursions and minimum safety factors for intact, damaged, and fatigue limit states.
Contact us to see how we can support the above requirements and strengthen your confidence that your mooring system is performing as intended, leading to production uptime and safe operation.