Blade Inspection Guidance for Offshore Wind Turbine Facilities

Abstract

Abstract Blades form an integral part to the operations and structural response of wind turbine facilities and demonstrating their long-term integrity in an offshore environment is challenging. Known blade degradation mechanisms and those that are likely in specific US offshore areas are considered along with evaluations of various inspection and condition monitoring capabilities, both now and in the near future. This paper is based on a study funded by the US Department of the Interior, Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE). Development Approach The inspection guidance development started with understanding existing blade inspection practices for both land-based and offshore facilities through a literature search and discussions with industry experts from the manufacturing, service and operational sectors, and others with broad industry experience. Also considered were inspection technologies and practices expected to be available for practical implementation within the next few years since these will likely be in use when the first US offshore wind turbine facilities begin operating. In order to evaluate the pros and cons of various inspection practices, both established and novel, and determine the best approaches to recommend, a set of criteria were established to compare the various practices against each other:Worker Safety - the ability to implement the inspection safely and effectively considering the access requirements for blades in an offshore environmentScalability - the ability to implement the inspection across multiple facilities in a fieldRepeatability - the ability to reliably reproduce the inspection activity and obtain results that are consistent on the same blade and across multiple blades in a fieldCost effectiveness - qualitative assessment of the inspection cost in terms of manpower, downtime, and duration weighed against the potential data gathered Subject matter experts were queried regarding prevalent blade damage mechanisms, techniques used for identifying damage and in what situations each would be implemented, what access equipment and systems are used, and what technologies are available, or will be available, that have the potential for widespread use within the next five to ten years. Damage Mechanisms Current practice for blade inspections for land-based and offshore facilities is generally driven by knowledge of defects in similar blades or problems identified in the power performance of a particular turbine. In developing guidance for more proactive inspection and monitoring programs, it is useful to understand what mechanisms affect blade performance.