June 28 - Mammoet has introduced a Wind Turbine Assembly crane, the WTA 250, and a Wind Turbine Maintenance crane, the WTM 100, designed to address the construction and maintenance limitations of conventional cranes, as the turbines get bigger and higher.

Both cranes use the turbine's tower as a point of support, which Mammoet claims allows them to lift and lower components to greater heights than the equipment that is currently used. According to Mammoet, the innovations enable wind turbine manufacturers to further increase the capacity of their turbines with greater height and scale.

The WTA 250 has a capacity of 250 tonnes and will be developed in cooperation with the engineering firm MECAL, which will provide the wind turbine tower design. The crane is installed on a guide rail that runs along the bottom turbine section and can lift the next section using the turbine tower as support.

Once the next section is installed and equipped with a guide rail as well, the crane can push itself up along the rail and repeat the process for all the subsequent turbine sections, says Mammoet. After construction the guide rail can either be removed, or remain in place to for future maintenance operations.

According to Mammoet, because the crane uses the turbine's tower for support, the maximum lifting height of the crane "is virtually limitless."

The WTM 100, which has a capacity of 100 tonnes, is attached to two pre-installed hoisting eyes and can pull itself and the load up along the turbine using the tower for support. The WTM 100 has been equipped with claws that wrap around the tower to keep itself steady. According to Mammoet, it can be used on turbines that have been equipped with pre-fitted hoisting eyes and, in some cases, it can be used on existing turbines.

"Both cranes are compact - the WTM can easily fit into two standard-sized containers - and the WTA only needs two transport trailers to be moved on site," explains Wessel Helmens, Mammoet's innovations director. "Both cranes eliminate the height restrictions for turbines and render both the assembly and replacement process faster and more cost-effective.

"Because the cranes are attached to the tower, they have no footprint, making the need for additional ground reinforcements virtually redundant," adds Helmens.

Mammoet is currently discussing the first applications of this new technology with its customers, as well as the possibility of introducing more additions to the WT-series.

The WTA 250 ready to lift the second tower section.

The WTM 100 ascends to elevation just below the turbine.