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Worlds largest Offshore mast crane vessel, Seven Borealis
a remarkable feature of crane building
In the steel building industry crane building is a special discipline where regularly technical masterpieces are being build where to few people are aware of. The heart of this crane is a column over the full height and the load moment is carried by the mast. This is a unique solution for such a large crane, which rotating slew platform is also a new type. The mast construction gives an inherent safety feature; the load moment is carried by the mast. Both mast en slew bearings are of high technical quality
A 5,000 metric tonnes lifting capacity
The largest offshore crane in the world has a maximum lifting capacity of 5,000 metric tons, the mast stands 85.7 meters high above the main deck and is suitable for depths up to 3,000 meters. Recent developments are that oil-, and gas winning installations no longer function above sea level on platforms but below sea level, mainly due to finds in deep water, where platforms cannot be moored or against extreme high costs. The heart of the crane is the mast. The boom revolves around the mast, the base hinge moves, but the boom itself does not. The platform revolves on a slew baring that is attached to the mast. The boom is also attached to the rotating mast head with cables.
The essence of the crane is that the mast absorbs the entire load moment. To absorb the load moment the tapered mast, with a maximum diameter of 10 meters, is built with rolled sections in Dillimax 690 high strength steel. Plate thicknesses go up to 75mm in the transition part from the rectangular shaped foot and the round mast. The hybrid crane is shaped as an A-frame. Hybrid meaning the legs of the frame are partial tubular supporting beams but lattice constructions over the entire length.
Facts at a glance
- Delivered quantity: 5,000 metric tons
- Materials: Dillimax (S690), S355NL
- Commissioning: 2012
- Design and construction: Huisman Equipment, Schiedam
- Contractor: Subsea 7, Londen (UK)