REpower Systems AG, the exclusive turbine supplier, developed the 5M wind turbines, whose 5MW capacity is derived from a rotor blade diameter of 126m. While the turbine’s offshore jacket was being installed on the seabed, the turbines themselves were being transported to Scotland by ship, where they were erected on the quayside of Nigg harbour.

BOWTIS allows the full assembly of the 85m high turbine onshore and the safe vertical transit of the 1,000 ton assembly and lifting equipment to the offshore site on pontoon barge. It also allows a crane barge, in this case the self-propelled Rambiz of Scaldis Salvage & Marine Contractors NV, to land and align the turbine on the fixed jacket with an impact of less than 0.3g.

The Engineering Business’ system consists of three key elements, starting with a Jacket Interface Frame (JIF) which is fitted to the offshore jacket and provides the landing structure for the turbine. The Turbine Interface Frame (TIF) provides a base for the turbine on land during assembly and the main lift point. It also incorporates the hydraulic Soft Landing and Alignment Systems and is 22m in diameter. The Spreader Beam (SB) supports the top of the turbine and routes the lift wires to the turbine base.

All went to plan on the day the first turbine was installed. The weather then turned and Rambiz was under contractual obligation to leave before suitable conditions returned. The second of the two 5M turbines will be installed at a later date.

There was, nonetheless, cause for celebration, as expressed by The Engineering Business’ engineering director Mike Watchorn who said, ‘We have been campaigning for the concept of installing offshore wind turbines in a single lift since 2002. The Beatrice project has allowed the demonstration of both the feasibility and benefits of this concept.’

MJ Information No: 22518<