Large Diameter Drilling (LDD), an Acteon company, has signed a contract with DEME Offshore to deliver grouting services for the installation of foundations at the Saint-Nazaire offshore wind farm in France, where the first turbine foundation was recently installed.

The wind farm, first such project to use drilled XL-monopile foundations, will consist of 80 GE Haliade 6 MW wind turbines, installed between 12 and 20 kilometres off the coast of the Guérande peninsula.

LDD is providing skilled personnel and services for grouting the drilled monopiles in position and the transition pieces to monopile connections.

The scope involves grouting monopiles into drilled rock sockets using a high-strength grout, followed by grouting the transition pieces to the monopiles using an ultra-high-strength grout.

To support these operations, LDD has developed bespoke grout mixing and pumping equipment to deliver mixed grout to the drilled rock sockets at a rate of 100 m3/h, the company said. The equipment is designed to operate primarily using bulk grout supplied from large material silos, which are also being fabricated for this project.

“Traditionally, different types of equipment would be required to do both scopes, but, in this case, we can do both with the same equipment, which will optimise operations”, said Peter McElligott, business development engineer, LDD. “Furthermore, the output of 100 m3/h reduces the vessel time required to complete the foundations. This is a step change from what is currently available on the market and one that will improve the efficiency of installing large quantities of high-strength grout”.

The installation of wind turbine foundations at the Saint-Nazaire offshore wind farm site started at the beginning of this month, with DEME using its installation vessel Innovation to install the project’s 80 wind turbine foundations.

The foundations are being delivered by Eiffage Métal, with Sif producing 80 monopiles and primary steel for the 80 transition pieces, and Smulders manufacturing the transition pieces.

The 480 MW project, also known as Parc du Banc de Guérande, is scheduled to become operational in the summer of 2022, when it will become the first commercial-scale wind farm installed in French waters.

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