Integrity Management Strategy Definition
Creators: name: Róisín Harris
name: La Grotta, Alessandro
Publisher: name: Zenodo
Year: 2021

description: The MooringSense project aims to reducing OPerational EXpenditure (OPEX) and increasing efficiency of floating offshore wind turbines through the development of efficient risk-based integrity management strategies for mooring systems based on a cost effective and reliable on-line monitoring technology and digital twin. Currently, integrity management for Mooring Lines is based around time-based inspections and does not account for the location, type of damage or risk. Given the high cost of offshore operations (inspection, maintenance, repairs) it is of vital importance that a cost-effective integrity management strategy is developed to keep OPEX at an acceptable level. This deliverable details the advantages of using a risk-based methodology and goes on to develop a Risk Based integrity management strategy specific to MooringSense, to optimise inspection activity and reduce OPEX. Risk Based Inspection (RBI) identifies the components and areas in a mooring system of greatest risk and focuses inspection efforts on these areas. Risk Based Inspection is also able to detail the risks from a safety/health/environment perspective and/or from an economic standpoint. From this an optimised approach to inspection planning can be taken, with appropriate inspection intervals assigned which are based on risk. The degree of understanding of mooring integrity risk during the life of an asset, increases over time as more data from inspection and the digital twin becomes available. The assessment of mooring risk is, therefore, an ongoing activity with the level of detail increasing throughout the life cycle, and risk must be periodically reassessed over the lifetime of the windfarm, from design phase through to decommissioning. To develop the integrity management strategy, all potential threats and damage mechanisms that a mooring line may be subject to through its entire lifecycle have been identified. The mooring line is also segmented to identify specific areas of higher risk. The risk profile will not be uniform along the Mooring Line and not all degradation mechanisms are seen at all water depths. Risk can be assessed quantitatively or qualitatively. The risk level in MooringSense has been assessed qualitatively because degradation mechanisms associated with Mooring Lines are often complex and difficult to model. Fully quantitative RBI assessment is also data heavy and laborious and often does not further reduce risk nor results in better outcomes. The risk level is a combination of the likelihood of failure and the consequence of failure, and then the risk is evaluated using a risk matrix, to target targeting inspection to critical areas that require attention. This forms an initial risk ranking and inspection plan. The strategy then utilises the MooringSense digital twin, to inform inspection activities. The Structural Health Monitoring system and Remaining Useful Life tools are integrated into the strategy to inform the risk quantifying process. These provide continuous, online information, to flag integrity threats or degraded condition before an inspection would. The baseline inspection plan can then be altered according to digital twin data.