Wolffkran won the contract to supply the crane at the beginning of the year. The construction of the Spitallamm Replacement Dam at Lake Grimsel is located almost 2,000m above sea level. With the crane assembly planned for September, the first two TV60 tower sections were assembled for testing at the Wolffkran production facility in Brandenburg, Germany.

"Both Wolff 1250 B luffers have to be erected with a freestanding tower height of 92m, as they can neither be tied to the dam wall nor the surrounding rock face – and this in high alpine terrain with extreme weather conditions," said Patrick Witteck from the technical support team at Wolffkran and responsible for the development of the new TV 60.

"At the same time, they have to lift 16t at a maximum jib radius of 70 to 80m. This would not have been structurally possible using the TV 33, our largest standard tower element with external dimensions of 3.30m x 3.30m. That is why we developed the TV 60 for this project."

The cranes can lift the specified loads without needing any tower-ties, and still withstand wind speeds of up to 220km/h in wind zone D50 (according to EN 14439) when out of service.

"This was decisive as the WOLFF cranes will remain on the construction site throughout the winter," said Witteck.

Despite the sheer dimensions of the tower section, which has to be assembled with no less than 288 screw bolts and 24 pins, the project team placed particular emphasis on making its assembly as simple as possible.

"By using only comparably small M48 and M24 screw bolts, the tightening tools can easily be handled with one hand. Also, the screw bolts for connecting the tower sections are positioned so that no fixed tightening sequence is necessary and they can be handled by one person," Witteck explained.

Wolffkran estimates an assembly time of about four hours per tower element.

A total of fourteen TV 60 tower sections will be manufactured for the dam project at Lake Grimsel. A new connecting frame VR 3360 has also been developed to combine the TV 60 with the TV 33 tower system, allowing a freestanding tower height of up to 130m for the WOLFF 1250 B. The new XXL tower element weighing 28t can be disassembled into its individual parts and transported on just 1.5 trucks while also being optimised for transportation in standard sea freight containers.