Mammoet supports world’s first floating wind farm

Mammoet undertook two scopes during the course of the project. Firstly, Mammoet performed the weighing, transportation, and load-out of five spars, weighing 3,585t each and measuring 91m long x 14m wide, in Fene Shipyard in Ferrol, Spain. 

Mammoet began this operation by using jacks and weighing cells to carry out the weighing. For the transportation of the spars, four sets of trolleys connected to four hydraulic points were used. The spars were transported from the construction table, then either to the loading dock or first to the intermediate storage area and then to the loading dock.

Mammoet designed and manufactured transport cradles to sit the spars in. The spars were loaded out consecutively, by loading out the first spar then turning the boat 180°, and loading out the second spar. Mammoet used 30 ramps, measuring 5m long, to access the ship from the pier. The transport of the fully-assembled spars reduced the total number of maneuvers needed and enabled Mammoet to meet the project’s deadlines and milestones. Following the completion of this project phase, the spars were shipped to the assembly site. 

The turbines themselves would be assembled at NorSea Group’s Stordbase yard in Stord, Norway. Mammoet was contracted by NorSea Group AS for the lifting and transport operations conducted onshore at the yard. Besides the lifting and transport activities needed to assemble the five turbines, Mammoet was also hired for its specific turbine assembly expertise. Mammoet was responsible for the engineering drawings and the transport drawings and provided NorSea Group with advice on lifting strategies and planning, resulting in a smooth assembly.

Initial estimates showed that the customer would need a 1,350t crawler crane to lift the components. Based on its expertise, Mammoet came up with an approach that would only require a 1,100t crane, allowing it to do the job much more efficiently. Each of the 6 MW wind turbines had been shipped to Stord in nine separate components. At the yard, Mammoet assembled them using an LR 11000 crawler crane as the main crane and 24 axle lines of SPMTs. When the assembly and outfitting were completed, a Crane Vessel transported the 1,150t assembled turbines to their floating foundations – the spars – now situated in the fjord. 

After the turbines were installed on the foundations and finally prepared, they were towed across the North Sea to their final destination , Scotland. The wind farm - which generates enough power to light up approximately 20,000 households – now stretches over about four square kilometers, at a water depth of 95-120m.