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Performing marine operations in strong current areas effectively

Date: July 09, 2018 at 14:26 GMT

SABELLA’s D10 marine current turbine was immersed in the Fromveur Passage in June 2015, becoming the first, and at present only, full scale tidal turbine to inject electricity into the grid in France. The initial installation was performed by lowering the whole tidal turbine at once, including the gravity-based foundation and its ballasts. This operation was carried out using a standard heavy lift vessel, without dynamic positioning, kept in position by her two anchors and three tugs. The installation was partially successful with the need for a new operation two months later for the connection of the turbine to her export cable. For the retrieval operation, only the turbine was retrieved, while the foundation remained on the seabed. This operation was carried out by MOJO MARITIME using an OCV vessel, with dynamic positioning (DP). This kind of vessel proved to be much more reliable and safer than the first installation vessel, and perfectly adapted to this kind of operation. Specific procedures and tools had to be developed for this operation, including an offshore berth and a “Launch And Recovery System”. Another operation was performed by SABELLA and MOJO MARITIME in order to install a new connector at the end of the export cable, for which the vessel had to leep perfectly her position during more than 48 hours with the cable hanging on her side. This was made possible thanks to a good choice of vessel, a perfect planning and a good management onboard. These innovative methods bring cost reduction opportunities by enabling the use of smaller vessels with lower lifting capacities and result in shorter operating times through adapted tools and well-prepared procedures.

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