A Modulift spreader combined with a 45m-long beam attached to a gantry and a crawler crane provides a way to lift 750-ton monopiles from a ship onto land at a German port. Schmidbauer GmbH & Co. was tasked and challenged by Cuxport GmbH to develop equipment for lifting the monopiles, bound for the Nordsee One offshore wind farm, using an existing gantry. However, the crane only offered 600 ton of lifting capacity and the beam had a net weight of 100 tons. So, the gantry was only suitable for a 500 ton lift.
Consideration also had to be given to a number of additional complications. A special coating on the monopiles meant that attaching rigging equipment was not possible at all points, while height was limited and there was 20m between the gantry’s hooks that were positioned 10m to each side of the center.
The lift-planning team discovered 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, explained, 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 has capacity to 600 tibs at 12m or 40 ft and up to 23m or 76 ft at lower capacity.
Verges said: “Slings came together in a 600 ton hook block that let us completely turn the monopiles. The rigging around the monopiles had to be kept short so we had to deliver [125 ton] Polytex slings at a special length to fulfill the requirements.”
At the other end of the tandem lift, Schmidbauer provided a Liebherr crawler crane (model LR 1600/2) with wheeled counterweight carrier that allowed it to lift even the second row of each pontoon load from the barge without turning it.
Thirty monopiles were lifted in a five-month period. Two travelled on each pontoon to Ambau GmbH in Germany. Verges explained that if a smaller crawler crane was used, after picking up the first row, Schmidbauer would have had to turn the barge prior to lifting the second unit. Otherwise, the distance would be too far.
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.
Filed Under: Towers