The odd couple14 November 2016
A Modulift spreader bar was used to allow a dockside gantry crane and crawler to work in tandem.
For a job lifting 750t monopiles at the port of Cuxhaven, Schmidbauer used the port’s own gantry crane and a 600t Liebherr crawler, rigged with a Modulift spreader and 45m lifting beam.
Schmidbauer was challenged by Cuxport to develop a solution for lifting the monopiles for the Nordsee One offshore wind farm, using an existing gantry crane.
However, the crane only offered 600t of lifting capacity and the beam itself had a net weight of 100t, therefore the gantry was only suitable for 500t of lift.
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, as Philipp Verges, sales manager global projects and key account manager offshore at Schmidbauer, said 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, sourced from Schmidbauer stock, 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.
Verges said: “Slings came together in a 600t hook block that allowed us to complete turning of the monopiles. The rigging around the monopiles had to be kept short so we had to deliver [125t] Polytex slings at a special length to fulfill the requirements.”
At the other end of the tandem lift, Schmidbauer 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.The Nordsee One wind farm consists of one offshore substation platform and 54 wind turbines that will be installed in water depths ranging between 25m and 29m. The wind farm is situated in a special spatial planning area reserved for offshore wind energy.