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Posted by Ted Sheppard on June 22, 2010 at 12:37 PM.
With the pending introduction of wind turbines offshore U.S. waters (the Cape Wind Project has been approved by the U.S. Dept. of the Interior and will involve 130 turbines) the time has come to develop comprehensive plans for addressing structural integrity management for the service life of these systems. Current regulations for offshore facilities focus on oil and gas drilling and production. While there are many similarities between wind facilities and oil and gas facilities offshore, the differences will have a major impact on how inspections are planned and executed.
Energo Engineering, Houston, Texas, did some work for the Minerals Management Service (MMS) to establish guidelines for inspection of the structural portions of offshore wind turbines. Robert Sheppard of Energo presented a paper (summarized below) on the subject at this year’s Offshore Technology Conference in Houston.
The height of the tower structure, compact footprint of the installed equipment, large blades that form an integral part of the structure and operations, and the number of facilities installed in a field are just some examples of the unique features of wind turbine structures that pose a challenge to inspections, particularly if your background is offshore oil and gas as opposed to land-based wind turbines. And for those familiar with land-based turbines, moving to the offshore presents a different set of issues such as getting inspectors to the facilities, evaluating the subsea structure and systems, and how degradations such as fatigue and corrosion are influenced by the offshore environment.
Some considerations for those involved in planning or executing offshore wind turbine inspections and integrity management include:
- Is there infrastructure to support getting inspectors to and from the facilities?
- Is there infrastructure to support subsea inspections either by diver or ROV?
- How will the inspectors get from the base of the tower to the nacelle?
- Do the data you want to gather (i.e., corrosion levels, crack indications, blade damage) involve visual only, visual from a distance, NDT, close access to blades?
- What will you do with the data gathered and how will that help plan future inspections of this and other facilities in the field?
With proper planning both for collecting and using the data gathered during inspections, a robust integrity management program can be implemented to help ensure these facilities are operational throughout their service life.