A jacket built for the for the Dudgeon Offshore Wind Farm offshore substation by Sembmarine SLP in Lowestoft, England, sailed away from the yard yesterday (11 May).
The 1500-tonne structure that has dominated Lowestoft’s port skyline for months was maneuvered out of the harbour on a barge by three tugs.
Workers completing the substation’s four-deck topside – due for load-out and sail away in July and August – gathered high on the module to watch the departure of the jacket, its top shrouded in sea mist.
The structure is the latest of more than 90 offshore structures delivered on time and safely by the company.
Sea-going tug Pegasus met the barge just north of Lowestoft at West Holme buoy where it was handed over by Sembmarine SLP to Dutch firm Seaway Heavy Lifting.
Pegasus then towed the jacket 100km to the Dudgeon site 32km off Cromer, Norfolk, to await the arrival of installation crane vessel, Seaway Heavy Lifting’s Stanislav Yudin, from Holland.
The jacket will be lifted into place by the anchored Stanislav Yudin’s crane and sunk into the seabed using suction bucket technology, the first time it has been used on an offshore substation in UK waters.
On board the Stanislav Yudin to supervise its installation will be Sembmarine SLP’s offshore manager Brett Hurrell with staff from suction bucket specialists SPT Offshore.
Sembmarine SLP was contracted to work with Siemens Transmission and Distribution (STD) to design and build the offshore substation for wind farm owners Statoil, Statkraft and Masdar. Representatives from Statoil and Siemens were at the sail away.
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 turbines by 12 inter-array cables.
Two export cables will take the power to Necton. The wind farm will generate enough electricity to power 410,000 homes.
At the sail away, Lowestoft harbour master Gary Horton was on board the barge guiding the vessels out of the harbour. Lead tug was the Multi-Tug 27 with the Avant 20 behind, braking and steering. They were assisted by EMS (Eastern Marine Services) vessels Defender and Surveyor, as guide and transfer vessels.
Matthew Wooltorton, Sembmarine SLP’s project manager for the offshore substation, said: “There is a total of 6000-tonne moving away. It is not a quick operation, at a speed of about 4knots, possibly up to 10 knots once at sea.”
The team had been planning the sail away for months to meet the strict criteria and ensure a safe and smooth departure, he said. Yesterday was chosen for the perfect weather conditions.
“We are already planning the next sail away in August for the topside and are booking tugs."
The jacket is designed to stand in the sea for at least 25 years.