Liebherr crawler cranes make tandem jacket lift

Heavy load specialist Schmidbauer engineered a tandem jacket lift using two 750t Liebherr crawler cranes  at an offshore terminal in Bremerhaven, Germany. Offshore logistics provider BLG contracted Schmidbauer to assemble the jacket's underlying structure, destined for the Borkum West II offshore windpark. The 600t upper section of the jacket needed to be positioned on top of the 900t lower section. The challenge was to move both cranes while 70m apart with this load on the hook, Liebherr said.

The operators set up the two Liebherr LR 1750 with the same configuration: 42m main boom, 28 luffing jib and 31 m derrick boom with 260t of suspended ballast. Schmidbauer conducted a detailed crane study simulating all phases of the hoisting process, preventing complications related to projecting edges, ground pressure and hook height. It ensured ground preparation on a special bed of sand with load distribution mats before fastening the load with two auxiliary cranes. It rigged four 400t shackles in a confined space.

The crawlers tandem-lifted the jacket out of the support framework, with two guides ensuring that the distance between the two crawler cranes remained the same at all times. Once the upper and lower sections were placed, the cranes continued to hold the load in place for two full days until the welding of the platforms was complete. Schmidbauer used a 450t telescopic crane with luffing jib to remove the shackles and ropes at a height of 50m using two 750t Liebherr cranes belonging to third party firms.