May 23 - Mammoet has used a Liebherr LR 11350 crawler crane positioned on a jack-up platform to erect 48 Siemens wind turbines for the Westermeerwind offshore wind farm on the IJsselmeer in the Netherlands.
The crane was first configured with a 36 m radius to position the foundation piles, each of which measured up to 40 m long and weighed 300 tonnes, 25 m into the bed of the lake.
Once all the foundation piles had been inserted and the technical equipment installed, work began in September 2015 on lifting the tower sections, nacelles and turbine blades into place. The lattice boom of the Liebherr LR 11350 was extended to a length of 114 m in order to assemble the 95 m high turbines.
Large pontoons - each laden with two tower sections and a nacelle - were transported over 60 km to the site from the Port of Amsterdam using tugs. The tower sections were transported upright, enabling the LR 11350 to lift and assemble the components without using an auxiliary crane. The lower tower section was the largest load lifted, weighing in at 150 tonnes.
A small floating crane was required to help lift and position the wind turbine blades - which were assembled into a rotor star on the opposite coast of the IJsselmeer and then transported to the site.
During the winter, Liebherr explained that storms and strong winds often meant that the pontoons could not travel to the erection site. Despite these setbacks, the farm was completed on schedule and is now operating at a generating capacity of 144 MW.