Project

The contract involved the installation of the mono pile foundation together with the erection of the tower, nacelle and rotors.

Scope of work

Installation of large diameter driven piles
Specialist grouting
Offshore transport
Erection of offshore wind turbines

General Information

Hydro Soil Services, one of the subsidiaries of our main shareholder DEME completed the first (supra mega watt turbine) wind park offshore in the Baltic as main contractor for Enron Wind. This project included the installation of the mono pile foundation, the transport and the erection of the wind turbines for the Utgrunden off shore wind farm in Sweden.
Hydro Soil Services was awarded the contract to transport and install seven 1.5 MW turbines.
The contract involved the installation of the mono pile foundation together with the erection of the tower, nacelle and rotors. Hydro Soil Services carried out detailed assessment of the lifting requirements and decided to deploy two self-elevating jack up platforms of 600 tonne and 200 tonne deck capacity to undertake the work. This proved to be critical in reducing delays due to poor weather to a minimum and enabled the erection to be undertaken in the most efficient and cost effective manner.

Description of the works

The first stage of the project involved the transport and instal-lation of seven steel mono piles. Each pile weighed 140 tonnes, was 34 m long and 3.0 m in diameter. The piles were transported from the fabrication site atFrederikshavn by sea going barge and thenlifted into position and driven using one of the jack up platforms. Each pile was driven 19 m into the seabed by means of an hydraulic hammer of 500 kNm deployed from the jack up.
On completion of the foundations, each pile cap was fitted with a prefabricated transition piece incor-porating a working platform and cantilevered transformer bed. The transition pieces were attached to the pile caps by means of a specially designed grouted sleeveconnection, 5 m above sea level.
The third phase of the operation involved the erection of the towers, nacelles and rotors. Towers and nacelles were transported by barge from the quayside at Bergkvara and erected with the jack up platform which installed the foundations.

The prefabricated 70.5 m diameter rotors were collected at Bergkvara by the smaller jack up and then lifted into position with the two jack up platforms working and lift-ing in Tandem. The final assembly stands some 65 m high to the nacelle hub.
The project was awarded end of July 2000 and work commenced in early September 2000. Transporta-tion and installation of the founda-tions was completed by the end of September with the final erection of the towersand rotors completed by the end of October 2000.

Main Equipment