Cost-effective risk-based inspection planning for offshore wind farms

Offshore wind farm assets require regular inspections. Studies and industry experience have highlighted the importance of selecting the appropriate inspection and maintenance (I&M) plan, as it directly impacts the reliability of the components and the associated maintenance cost. If inspections are carried out too frequently, the associated risks will be low and reliability will be high, but the cost will also be high. On the contrary, if no or very few inspections are carried out, unexpected failures of the structures could occur. This paper presents a risk-based inspection (RBI) framework for offshore wind farms, building on existing knowledge from other industries including nuclear, oil & gas, chemical and aerospace. This approach considers the probability, the consequences and the cost of the operational or maintenance activity via a criticality analysis that allows optimal selection and prioritisation of I&M activities. A case study is presented where this framework is implemented on the transition pieces (TPs) of the wind turbines, by investigating information received from design, operation and inspection reports as well as monitoring equipment. Guidelines are also proposed on how to utilise novel monitoring and visual inspection techniques to further improve the implementation of RBI. The results of this paper suggest a less frequent I&M strategy, which could reduce the associated TP inspection costs by up to £0.7 million/MW installed and increase the safety of personnel. The study will be of interest to offshore wind farm developers, operators and maintenance providers, to better prioritise I&M activities and increase the operating revenue of their assets. A Koltsidopoulos Papatzimos, T Dawood and P R Thies