Ship crane on an even keel

13 December 2007

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Using a climbing jack system to erect a 3,400t shipyard crane allowed Bidlift to control the lift with millimetre precision. Will North reports

Bidlift worked on the project for World Industries Ace (Wia), a South Korean conglomerate that makes everything from machine tools to satellites. On this project, the Korean company erected a Goliath gantry crane for a new shipyard in the Philippines. Bidlift’s Kramo modular climbing jack system was used throughout, from the initial assembly of the gantry’s beam to its final erection.

Four towers were used, in pairs with a lifting beam between each tower pair. On each tower, two climbing units were fitted: the eight 453t climbing units gave a maximum lifting capacity of 3,624t. The 177m main gantry beam and upper trolley were assembled on three stools, and the climbing jacks lifted the beam to a height of 8m, where the gantry beam was held while the lower trolley was fitted.

The two trouser leg sections (the triangular section at the top of the legs) were then welded to the either end of gantry beam, and the legs themselves hinged to these. Each leg was tailed using a mobile crane or crawler. As the climbing jacks lifted the beam, and brought the hinged tops of the legs with them, the feet of the legs moved closer together, tailed by the cranes throughout.

When the legs were at the correct angle, they were welded to the trouser sections. The precise tolerances afforded by the climbing system meant that the best possible position for welding could be achieved. With the top of the legs welded to the trouser sections, the bogies and sill beams (which connect the legs at the base) were positioned underneath. The jacks then lowered the gantry in place, ready to be welded to the sill beams and bogies. Finally, the climbing jacks and lifting beams were lowered to the ground and removed, and the modular tower sections disassembled using a crawler crane

How it works

The climbing jack system uses simple principles to deliver great lifting power and millimetre precision. The climbing motion will be familiar to anyone who’s ever climbed a tree, gripping the trunk with their feet as they reach higher, and then with their hands as they pull their legs up behind them.

Each climbing jack comprises a pair of lifting cylinders with a pair of head blocks above and below, and a pair of equaliser cylinders. The jack grips onto a vertical square bar using wedges in head blocks.

The wedges sit on either side of the square bar inside a cut-out space in the head block shaped like an upside down V-shape. As load is applied to the jacks, the wedges are forced into the narrowing slot, compressing them onto the bars. Should there be a hydraulic failure the wedges engage. This makes the system very safe.

The wedges are locked together with link bars. The length of the linkage and the stroke of the hydraulic cylinders are slightly different. As the lifting cylinders extend and retract, the geometry of the link arrangement engages and disengages the wedges. This fail-safe system makes it impossible for both sets of wedges to open at the same time. Although the bars are clamped to a lattice mast, they move freely under compressive force, so nearly all the load is transmitted down the bars. The lattice mast merely prevents the bars from buckling.

The equalising cylinders are linked together hydraulically. This ensures the load is spread evenly between the jacks, and the top of the jacks remain level with one another without any outside intervention. The pressure in the equalisers can also be adjusted, precisely changing the level of load, with a tolerance of millimetres, for welding jobs and precise fitting of modular installations such as pipe racks.


The gantry raised to near-final height The gantry raised to near-final height
BidLift gantry lift BidLift gantry lift
Starting the job Starting the job