Gantry cranes and crawler cranes are an odd pairing, but one that worked perfectly at an offshore wind farm. Although I did not visit the site in person, through case analysis, I can also know that this is a very difficult project.

A dockside gantry crane and crawler to work in tandem

The challenge of this project was the need to develop a solution for lifting offshore wind farm monopiles using existing gantry cranes.

However, the gantry crane currently owned by the project can only provide a lifting capacity of 600t, and the net weight of the beam itself is 100t, so the gantry is only suitable for lifting 500t.

Consideration also had to be given to a number of additional complications. There was a special coating on the monopiles that meant attaching rigging equipment was not possible at all points, while height was limited and there was 20m distance between the gantry’s hooks that were positioned 10m to each side of the centre.

The lift planning team discovered that there were two lifting lugs in the centre of the 45m beam offering a more convenient distance of just 4.75m. However, they were 90° in the wrong direction – the beam was originally manufactured for special lifting of three-legged tripiles – and the forces applied during lifting would have broken the eye plates.

Eventually, a MOD 400/600 beam was used as an inverted spreader, owing to the two pick points above it and the need to bring the slings together in one point. MOD 400/600s offer capacity to 600t at 12m and up to 23m at lower capacity.

At the other end of the tandem lift, the company provided a Liebherr LR 1600/2 crawler with wheeled counterweight carrier. This was able to lift both the first and second row of piles, without turning the barge, which would have been necessary with a smaller crawler crane.

Thirty monopiles were lifted in a five-month period; two travelled on each pontoon to Ambau in Germany.

What we learned from this case

Although we have not provided complex solutions for offshore wind farms, we have provided container gantry cranes for ports, rail-mounted gantry cranes for train projects, and crane solutions for complex environments such as cement plants and steel plants. We believe that with complete technical reserves, no matter how complex the working environment is, we can always find a corresponding solution.

Through this case, we can extend our thinking. Does the offshore wind farm need to use gantry cranes for maintenance after the construction is completed? Such as wind turbine components, towers, infrastructure, etc. These components are usually bulky and heavy. Once they enter maintenance mode, they should require further participation from the gantry crane. Therefore, when designing a gantry crane, it is necessary to consider the corrosion problems faced by the gantry crane during long-term operations in the port. At the same time, due to the complex environmental conditions of offshore wind farms, gantry cranes need to have high stability and safety to ensure safe and stable hoisting operations under various weather and sea conditions.

Facility structures and layouts at offshore wind farms vary, requiring customized designs based on specific wind farm conditions. Customized gantry cranes can better adapt to the characteristics and needs of wind farms, improving work efficiency and safety.