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Offshore Wind Journal

New ways sought to make underwater inspection easier

Mon 17 Jul 2017 by David Foxwell

New ways sought to make underwater inspection easier
New ways to inspect grouted connections and welds are required

The Carbon Trust’s Offshore Wind Accelerator has launched a competition to find ways to inspect the substructures of offshore wind turbines more effectively and reduce the cost of offshore wind.

The competition is open to innovators with inspection technologies that can provide information and data on grout integrity and welds for both monopiles and jackets.

Winners of the competition will test their technologies on installed foundations at fully operational windfarms in Europe, and receive hands-on mentoring and advice from the nine Offshore Wind Accelerator (OWA) industry partners, which collectively represent over 75 per cent of the European market. The aim of the competition is to help these new technologies access the market and become part of the normal subsea inspection strategy for offshore wind developers.

Analysis carried out as part of the OWA’s underwater inspection methods study has shown there is a need for innovation in the offshore wind subsea inspection sector. As of January 2017, there were over 3,500 turbines installed in Europe, representing a cumulative total of over 12.5 gigawatts installed capacity. Over 80 per cent of these turbines are built using monopole structures, which have grouted joints. Over the next decade European offshore wind capacity is predicted to almost triple, with the monopile continuing to be popular.

Current estimates show that around 35-40 per cent of the monopile fleet, mainly pre-2012 structures, may have been affected by issues relating to grouted joints, for example corrosion caused by the marine environment. Many of the structures built post-2012 will require performance monitoring. New designs such as jackets, which are constructed using welded nodes are also being developed and present new inspection challenges for the industry.

At present, the methods to inspect grouted connections and welds are limited and do not provide sufficient data for offshore wind developers. There is limited knowledge on the integrity of the structures which can lead to costly high levels of precaution in the inspection regime, such as conservative preventative maintenance or more regular inspections. By providing a solution that can provide asset owners with the knowledge they require, costs can be reduced significantly and the inspection regimes optimised.

Industry standards require that a sample of offshore wind subsea structures within each farm (typically 5-15 per cent) are periodically inspected. This can be carried out at varying intervals, depending on the standards used but would typically occur every 4-5 years per windfarm. If defects, or greater levels of corrosion than expected, are observed then the inspection programme can call for wider (up to full farm, in the case of a serious generic problem) or more frequent inspections. 

“Offshore wind is now well established in Europe, and is truly entering its operational phase. This comes with fresh challenges but also many opportunities for both new innovation and technology transfer from other industries; this competition represents one such opportunity. The Offshore Wind Accelerator is focused on continuing to reduce the costs of offshore wind, and with this call it is hoped that we can find the next generation of inspection technologies to help the industry continue to drive down prices,” said Michael Stephenson, project manager for the foundations research area.

Periodic maintenance specifications will also be a feature of emerging markets in the US, Taiwan, Korea and Japan which present further opportunities for new technologies that can prove cost effective.

The competition will run until 13 October 2017, and clarification questions should be sent to the Carbon Trust by 1 September 2017.

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