Winds of change


Winds of change

With interest in renewable energy growing worldwide, Trelleborg is adapting its oil and gas solutions for use in the offshore wind sector, with outstanding results.

With much of the world looking for fossil-free energy sources, wind power is becoming increasingly popular. To more efficiently capture this resource, wind farm operators are frequently choosing offshore locations for their plants, where higher velocity winds are present and there is less impact on communities. 

Trelleborg is currently delivering a number of unique solutions for HVDC BorWin3, a high-voltage  link that will allow power generated by wind turbines in the North Sea
to be transmitted to the German mainland. Due to commence operation in 2019, BorWin3 is the third in a series of such links operated by the transmission system operator, TenneT, with each named after the nearby island of Borkum.

BorWin3 is significant in that its converter platform is being constructed using “floatover” technology. This is only the third time that this approach, common in the oil and gas industry, is being used on a wind farm project.

Vincent Tan, Sales and Marketing Manager within Trelleborg Offshore & Construction in Singapore, explains that the converter platform consists of a six-legged base (or jacket) and a separate topside. The base will first be secured in place and then the topside will be transported by barge to the site and lowered on top of it.

Trelleborg was chosen by Petrofac, the company responsible for construction and installation work on the project, to supply six deck support units. These sit between the topside and the deck support frame on the barge used to take the topside to site and absorb impact loads as the topside is mated to the jacket.

Trelleborg is also supplying six leg mating units (LMUs) that reduce impact forces during the mating operation, allowing topside movement to be progressively reduced to zero during load transfer.

While LMUs are generally welded to the topside prior to the transport operation, the BorWin3 project calls for the external tubular cans to serve as individual supports during the construction phase. “This will entail immersion in seawater, and Petrofac expressed concern about the effects on the LMU’s internal parts performance,” says Tan. “Trelleborg responded by creatively proposing that the LMU be delivered in two stages – first the tubular cans in January 2017 and then the internal components in January 2018.”

While this satisfied the customer, it created another challenge as the internal components of the leg mating unit are usually bolted and welded to the tubular can prior to its being welded to the topside. Because the cans are being fitted to the topside in advance, Trelleborg engineers devised a unique clip system that allows the internal components to be easily fitted once the topside is complete.

As well as allowing the BorWin3 project to proceed, the solution has potential for other applications, and Tan says there are now plans to use it on other Trelleborg projects.

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