A series of unique challenges had to be overcome when crane and transport operator Maxikraft removed the rotor and nacelle of a 5 MW wind turbine at a height of 90 metres - offshore.
Maxikraft Kran- und Schwerlastlogistik used a 1,250 tonne capacity Terex CC 6800 crawler crane on a series of repairs at the Hooksiel offshore wind farm off the north coast of Germany.
Working for wind farm operator BARD, the Maxikraft team had to deal with the different conditions offshore. "To start off with, an offshore lifting operation is obviously much trickier than a land-based assignment, since the wind and sea can act up at any moment and cause a great deal of instability," explained Raik Hanisch, crane operator.
The heavy-lift pontoon Giant 4 was used to bring the CC 6800 to the site, just offshore of Hooksiel in the north of Wilhelmshaven. It also provided the stability required for the four lifting operations. The first was to remove and lower the turbine's 170 tonne rotor, which had a diameter of 127 m. The 280 tonne nacelle could then be removed in a second lifting operation. Once the repairs were completed, the components were lifted and installed back on the tower in the opposite order.
Rigging the 13,952 tonne-metre crane in LFVL boom configuration of 90 m main boom and 18 m fly jib allowed it to reach the required working height. Superstructure counterweight at 250 tonnes, in addition to 80 tonne central ballast on the carrier and a Superlift ballast weighing 240 tonnes, allowed the crane to operate freely within a working radius of 22 m.
The Maxikraft Kran- und Schwerlastlogistik Group consists of four companies: Maxikraft, Maximum, Kranlogistik Sachsen, and Kranlogistik Lausitz. About 400 people are employed by the Group.
It offers crane services up to 1,250 tonnes and transportation of payloads up to 300 tonnes, Also offered are machinery transport and plant relocation, steel and concrete assembly, and tower crane transport and erection.