A 1,500-tonne steel jacket which will support an offshore substation at the 402MW Dudgeon offshore wind farm has been installed in the seabed some 32 kilometres off Cromer, Norfolk.
The jacket structure, built by Sembmarine SLP Ltd, was sunk into the seabed using suction bucket technology for the first time on an offshore substation in the UK. Four suction buckets, weighing around 110 tonnes each, were welded on to the legs of the jacket in Sembmarine SLP’s yard at Hamilton Dock.
The jacket stands at a near-perfect verticality of 0.01 degrees. Pump operators on the four 9-metre diameter suction buckets achieved the almost-perfect inclination in less than two hours’ pumping, SLP said.
SPT Offshore, designers and manufacturers of the suction buckets, performed the installation, pumping the buckets 6 metres into the seabed.
The steel jacket had been lifted from its barge by a crane on the Seaway Heavy Lifting vessel, the Stanislav Yudin.
The installation operation was completed over two days.
The four-deck topside which will be lifted onto the jacket is currently being completed and will be ready for sail-away in August.
Sembmarine SLP was contracted to work with Siemens Transmission and Distribution Ltd (STDL) to design and build the offshore substation for wind farm owners Statoil, Statkraft and Masdar.
The offshore substation will house all systems needed for the handling and export of power from the 402MW wind farm to the onshore substation at Necton, Norfolk and connects to Dudgeon’s 67 Siemens 6MW turbines by 12 inter-array cables. Two export cables will take the power to Necton. The wind farm is expected to be commissioned by early 2017.