Innovative Solution for Seafastening Offshore Wind Turbine Transition Pieces during transport

Innovative Solution for Seafastening Offshore Wind Turbine Transition Pieces during transport

Hoeksema, Wouter

Kolstein, M.H. (mentor)
Bijlaard, F.S.K. (mentor)
Hoogenboom, P.C.J. (mentor)
Breedveld, J.P. (mentor)
van Dalen, W.R. (mentor)

Civil Engineering and Geosciences

Structural Engineering

2014-02

Seaway Heavy Lifting is an offshore contractor that transports, installs and decommissions offshore oil and gas platforms and offshore wind turbines. During transport, objects need to be secured on the deck, the so-called seafastening. In particular for parts of offshore wind turbines, called Transition Pieces, this proves to be difficult. The Transition Pieces are on average 25 m high tubular structures and weight 300 mT. The outside is covered with a special coating and various attachments, such as boat landings, ladders, and anodes for corrosion protection. The inside of the Transition Pieces contains various structures and equipment, such as groutskirts, shear keys, J-tubes and internal platforms. Seaway Heavy Lifting currently uses clamps on the lower flange to secure the Transition Pieces in an upright position to the deck of the ship. This causes relative high stresses in the flange and weld and turned out to be a critical limiting factor during transportation for several projects. Due to this limitation, the workability of the vessels is suboptimal. Many other offshore contractors use the same or similar method of clamping the lower flange to the deck. A new method for seafastening Transition Pieces is proposed to improve the securing strength, the safety, and workability of the vessels. This new method comprises of a tubular element, much like the monopile on which the Transition Piece will stand once on offshore location, welded onto the grillage. The Transition Piece can then be lifted over this tubular element. Mounted on the tubular element are hydraulic cylinders that extend outwards towards the inner wall of the Transition Piece. By exerting a force to the inner wall, the Transition Piece is effectively secured to the vessel. This method avoids using the rather weak lower flange. Strength calculations have shown that this new method can withstand accelerations and accompanying forces caused by the ships motions that are nearly twice as high as the current method allows. Because the new method is fully automated, it requires no manual labour and the seafastening can be activated and deactivated quickly, thus saving critical crane time. It also reduces the time frame where the Transition Pieces stands on the deck unsecured, as is the case with the current method which uses clamps and bolts, thus improving safety. This thesis covers the invention of the new method, calculating the critical structural parts, and detailing those element that are crucial to the design. Currently, a patent applications is pending.

http://resolver.tudelft.nl/uuid:308b7b2f-f6d7-44c5-ae03-ad2519afada3

Student theses

master thesis

(c) 2014 Wouter Hoeksema