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The offshore substation jacket for the Dudgeon Offshore Windfarm, made in Lowestoft by Sembmarine SLP, has been successfully installed in the seabed on site.

The four-legged jacket, designed and built by Sembmarine SLP, 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. It the first time suction bucket technology had been used on an offshore substation in UK waters.

SPT Offshore – designers and manufacturers of the suction buckets – performed the installation, pumping the buckets 6m into the seabed 32 km off Cromer, Norfolk. The 1500- tonne steel jacket (the latest of more than 90 offshore structures delivered on time and safely by Sembmarine SLP) had been lifted from its barge by a crane on the Seaway Heavy Lifting vessel, the Stanislav Yudin.

It had been on the barge since its sail away from the Lowestoft fabrication yard recently.


Brett Hurrell, Sembmarine SLP's Offshore Manager said the pump operators of SPT Offshore had done a ‘fantastic job’ performing the suction installation to achieve the 0.01 degrees.

“The jacket inclination is really worthy of note. The SPT operators deserve credit for their work to get it almost perfect. The operators of the four pumps adjusted the pressure after it had sunk under its own weight.

“The design and fabrication of the jacket was crucial too. It was a great combined job by Sembmarine SLP C, who designed the jacket, SLP Lowestoft, who made it and SPT, who made the suction buckets and installed the jacket.”

After delivering the jacket to the best quality, on time and with an outstanding safety record, Sembmarine SLP now hopes to win contracts for future offshore substations for windfarms being built off the east coast.

LOWESTOFT PRIDE Peter Aldous, Waveney

INSTALLATION TIMETABLE The installation operation was completed over two days. The crane lifted the jacket between 8pm-9pm on a Tuesday evening. It was lowered into sea by 9.15pm. By 10.45, it was starting to sink under its own weight and SPT started to control its inclination and, by 11.30pm, it was corrected.

At 6.40am the next day, SPT Offshore began the suction operation. By 8.10am all pumps were turned off as the final penetration and platform inclination had been achieved.


Matthew Wooltorton, Sembmarine SLP's Project Manager for the offshore substation, said: “There’s always a sense of satisfaction to see one of our projects successfully come to its end. Our focus is now on completing the topside for its planned sail away in August.”

Paul Thomson, Sembmarine SLP's Managing Director, said: “Our ambition now is to design and build more offshore substations like this to stand off our coast as an East of England business delivering top quality work and service to East of England offshore windfarms.”

MP, and the East of England Energy Group are working with Sembmarine SLP to win the work for the East of England. When it sailed away, the structure bore the banner ‘Designed and built in Lowestoft and delivered on time.’

The company was contracted to work with Siemens Transmission and Distribution Ltd (STDL) to design and build the offshore substation for windfarm owners Statoil, Statkraft and Masdar.

DUDGEON OFFSHORE WINDFARM The offshore substation will house all systems needed for the handling and export of power from the 402MW windfarm 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 windfarm will generate enough electricity to power 410,000 homes.

Sembmarine SLP

ONGOING PROJECT While the topside is under completion at the Lowestoft yard – the UK’s only fabrication yard of its capacity in the Southern North Sea – VBMS will be mobilising daily pulling in the turbine and export cables to coil on the jacket’s cable deck.


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