Overdick

OVERDICK is proud to announce the successful float-over installation of the DolWin gamma HVDC platform. The platform is located approximately 80 km offshore in the south-western part of the North Sea in water depth of only 27.5 m.

OVERDICK was contracted by NORDIC YARDS to do the basic, detail as well as T&I (Transportation & Installation) design of the DolWin 3 HVDC platform. NORDIC YARDS itself was contracted by GE who was hired as the main contractor by TenneT for this project.
Considering a topside weight of 18,450 tons, which is beyond the lifting capacity of any available offshore crane, the topsides was installed by a float-over operation. The jacket was designed as a split jacket so as not to pose any limitations to the transport barge and have a tide-independent float-over operation. The jacket was installed in 2016. Topsides transportation from the NORDIC YARDS (in Warnemünde) started on June 15th 2017 and took six (6) days.

For the float-over, the transport barge carrying the topsides was positioned in between the two jackets. Subsequently, the barge was de-ballasted to lower the topsides down to the jacket. After the mating of the topsides legs with the jacket LMUs was completed, the barge was removed and the topsides was jacked with the support of a temporary hydraulic strand jacking system to its final elevation 21.5 meters above the sea level. Although the split jacket design posed several engineering challenges, such as the relative positioning of the jackets and the topsides, the complete installation process is reported to be executed without any problems.

The scalable strand jacking system allowed completing the outfitting and pre-commissioning of the topsides in the yard in order to minimize a time-consuming and costly completion process as well as an efficient hook-up and commissioning work offshore.

After final completion, 900 MW topsides will be connected to the wind parks MERKUR OFFSHORE and BORKUM RIFFGRUND 2, supplying power to more than a million German households.

DolWin 3 is the fourth self-elevating HVDC platform for the German Bight designed by OVERDICK. Once more OVERDICK continues a successful track record by setting high standards in the self-elevating topsides weight and showing the scalable capabilities of the float-over installed self-elevating platform concept.

The excellent engineering service of OVERDICK ensured a proper and successful installation of DolWin 3 platform. Furthermore, OVERDICK is known as one of the leading engineering contributors to German offshore wind substation development.

Topsides Floatover – short video
OVERDICK Projects – DOLWIN gamma