Installation of 2 Gravity Based Foundations

Market: Renewables and Environmental
Scope of Work: Installation of 2 Gravity Based Foundations, Kriegers Flak Windfarm
Location: Baltic Sea, Denmark
Client: Jan De Nul NV
Period: February 2018
HLV: Rambiz

The Kriegers Flak Offshore Wind Farm (OWF) is a large offshore wind farm in the Danish sector of the Baltic Sea. This OWF is built on the Kriegers Flak shallow region, some 15km out of the Danish coast, close to the EEZ of Denmark, Sweden and Germany.

The OWF comprises of 600MW wind turbines in 2 separate areas. An offshore substation for each area will be erected: Kriegers Flak A (KFA; 200MW) in the western area and Kriegers Flak B (KFB; 400MW) in the eastern area. Kriegers Flak B includes an extension part denoted KFE so the foundation is denoted KFBE. The offshore substations will act as interconnector for the national grids in the Baltic Sea.

Scaldis Scope

Scaldis scope of this project comprised in the installation of both offshore substation’s Gravity Based Foundations (GBF’s) KFA and KFBE. Both GBF’s (KFA and KFBE) were supplied on one semi-submersible barge to the field. On site two main activities took place, which were repeated for each GBF:

1. Float-off GBF by Rambiz from the semi-submersible barge.
2. Sail to installation location with the GBF in Rambiz crane hook’s.
3. Position, lower and install.

At float-off location, the semi-submersible barge was fully anchored and pre-ballasted to a low freeboard condition. After rigging connection, the barge was submerged while Rambiz maintained pre-tension until the moment the GBF started floating.
With the GBF afloat, the float-off operation and transfer to installation position could commence. After arrival at installation location, HLV Rambiz positioned herself according to the applicable installation coordinates in a four point mooring system.

During the lowering operation, by filling the GBF’s ballast tanks, tension was kept in the Rambiz cranes continuously to keep the GBF stable and prevent it from capsizing. After touch down, the remainder of the GBF ballast tanks were filled. Once position and heading of the installed GBF were confirmed, rigging could be disconnected from the GBF by hydraulic
release shackles.


The Kriegers Flak wind farm is located in the Danish sector of the Baltic Sea and will act as interconnector between the Danish and German power grid. This interconnector project is  funded by the European Energy Programme for Recovery.