October 2 - At the ABC-Halbinsel offshore terminal in Bremerhaven, Germany, a jacket representing the underlying substation platform structure of the "Borkum West II" offshore wind park was fitted using two 750 tonne Liebherr LR 1750 crawler cranes.
The challenge here was not simply to hoist the exceptionally heavy load in tandem, but to move both cranes while they were 70m apart with this load on the hook.
The 600 tonne upper section of the jacket needed to be positioned on top of the 900 tonne lower section. To achieve this, there two Liebherr crawler cranes had the same configuration: 42 m main boom, 28 luffing jib and 31 m derrick boom with 260 tonnes of suspended ballast.
All engineering work as well as the delicate adjustment work and crane operations planning were undertaken by experts from crane and heavy load specialist Schmidbauer, a firm contracted by BLG. A highly detailed crane study simulated all phases of the hoisting process. Special attention was paid to the projecting edges as well as the ground pressure and the hook height.
Once the cranes had been moved into position on a special bed of sand with load distribution mats, the load was fastened with the help of two further auxiliary cranes. Four 400 tonne shackles needed to be installed in a confined space, with the shackle pin alone weighing 75kg.
The upper jacket section was then disconnected from its assembly platform and thanks to good weather conditions, it was possible to start the hoisting process immediately. The cranes needed to lift the jacket out of the support framework with complete lift synchronicity. The actual moving process was then carried out, with two guides ensuring that the distance between the two crawler cranes remained the same at all times. The specified positions for setting down and welding on the upper section were successfully attained on the first attempt, and it was possible to start the process of connecting the upper and lower sections straight away.
In the next stage, the load still needed to be held in place for two full days until the welding work was complete. The shackles and ropes were then removed at a height of 50m, using a 450 tonne telescopic crane with luffing jib.
The ABC-Halbinsel offshore terminal in Bremerhaven is used for the temporary storage of offshore windparks and to load this equipment onto construction vessels for offshore installation. The manufacturer of the underlying structures is WeserWind GmbH Offshore Construction Georgsmarienhütte which worked together on this project with BLG Logistics Solutions GmbH & Co. KG in the area of transport and warehouse logistics.
BLG offers comprehensive logistics solutions for the offshore wind industry, from procurement to production through to offshore installation.