West of Duddon Sands Wind Farm

At the time, the West of Duddon Sands wind farm involved one of the biggest offshore grouting contracts ever built in UK waters. The foundation installation was carried out by Offshore Wind Force, a joint venture of Dutch-based contractors Volker Stevin Offshore and Boskalis Offshore. The 108 turbines were mounted on monopile foundations, requiring specialized grouting to fill the annular gaps between monopiles and transition pieces. Installation and grouting took place in challenging offshore conditions, with short weather windows and tidal variations exceeding 8 meters.

After securing the monopile foundations in the seabed, transition pieces are placed and aligned for turbine tower installation. Pre-installed grout lines on the transition pieces enable flexible hose connections at the access platform, extending to the turbine deck. This setup allows the grouting contractor to efficiently connect grout hoses via a flexible boom arm from the vessel.

Over 4,770 tons of SikaGrout®-9500 grout was pumped into the monopile transition piece connections using the FoundOcean Super Pan Mixer. This mixer is proven to double current grout output rates when compared with other high-strength grout mixers on the market. Installing the 108 foundations, including the grouting works, took just 5 months to complete, averaging 21 foundation installations per month. This is a world record in the industry, and a new benchmark for future offshore wind farms.

Customer Benefits

• The high-efficiency mixing and delivery system enabled a record 8.8-hour foundation installation, including the monopile installation, levelling of the transition piece, and the grouting works.
• SikaGrout®-9500’s rapid strength development reduced the required weather window by 25% to 18 hours, significantly improving project efficiency.

Quick Facts

• Amount of material used: 4,770 tons
• Number of turbines: 108 × Siemens 3.6 MW
• Windfarm total capacity: 389 MW
• Homes equivalent: 300,000
• CO₂ reduced per year: 43,586 tons
• Turbine tip height: up to 150 meters above mean sea level
• Area of wind farm: 67 km²
• Foundation type: Monopile / Transition Piece
• Typical water depth: 18 - 24