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Offshore wind turbines plumb thanks to Enerpac’s synchronous lifting system

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Wind turbine manufacturer Bard Engineering GmbH has developed a unique concept for the foundations of wind turbines. The mast is placed on a supporting cross piece that rests above the water surface on three main pilings. The Enerpac synchronous lifting system was used to level this supporting cross piece accurately and in just a short time frame.

The Bremen-based company developed a patented concept for the foundation of the wind turbines: the BARD Tripile. The 90m high wind turbine rests on three main pilings that are each 90m in length.  Above the water surface, these three pilings are connected to each other by a cross piece on which the turbine mast stands. “One of the unique things of our foundation is that this part and all connections are above the water surface,” says Robert Ebert, Deputy Managing Director at Bard Building GmbH & Co. KG. “The mast usually rests on foundations that are below the water surface. We chose to have all installation activities performed above the water surface. The practical advantages are that we need fewer divers, that we are less dependent on weather conditions and that it allows us to carry out maintenance much more quickly and easily.”

Enerpac's hydraulic synchronous lifting system provided the solution for levelling the supporting cross piece. “The connection flanges aren't always straight and manual correction to the millimetre of any flange deviations turned out to be impossible. That is why we looked for options for installing the 500-ton support construction quickly and accurately, and that was possible with the synchronously controlled hydraulic cylinders,” says Robert Ebert. Three cylinders, each with a capacity of 100 tons, are mounted equally spaced around each piling for installing the supporting cross piece. Each foundation therefore has nine cylinders with a total lifting capacity of 900 tons. The cylinders are then connected to the computer of the synchronous lifting system on board the ‘Wind Lift I’, which finally levels the supporting cross piece with one push of the button."

"To achieve this, the cylinders first lift the supporting cross piece by approximately 20mm and then level it to an accuracy of 1 millimetre from that starting position. The installation process is controlled by the software, using stroke sensors and an inclination meter. Once the supporting cross piece is level, it is locked in place together with the piles by a 5m high concrete casing, with the concrete being poured into a hollow space to make a 13cm thick ring against the wall of both the supporting cross piece and the piles. “Nothing is welded or bolted; the concrete casing handles all the stresses,” explains Ebert.

As well as cylinders, Bard Engineering also invested in two control modules for the synchronous lifting system. Enerpac also trained Bard employees who will be working with the synchronous lifting system. Ebert now knows that the results are excellent. “The nice thing about this hydraulic Synchronous Lifting System is that it works completely automatically. Human errors when levelling manually, such as turning on the wrong valve, are totally eliminated by the system,” concludes Robert Ebert.

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