UK-based Osprey Ltd has lifted a 72.5 t catamaran using a 1000 t capacity Liebherr mobile crane and a one-over-two Modulift spreader beam configuration beneath its hook.
Osprey accepted a scope of work from shipbuilder Wight Shipyard to move the catamaran from the building where it was built to the water at Venture Quays, Cowes on the Isle of Wight, before a course was set for its final destination in Austria.
The 250-passenger Twin City Liner is 39.7 m long, 11.1 m wide, and 6.8 m high. The vessel is due to arrive in Vienna in time for the start of the new season at the end of March 2019.
From Building to Crane by SPMTs
The first challenge was removing the vessel from its building. Osprey selected two, six-axle Goldhofer self-propelled modular transporters (SPMTs) to work in tandem to move the load to within the reach of the Liebherr LTM1800D.
Lifting Equipment
The crane was complete with a 36 m high rig, designed to accommodate a 3.7 m centre of gravity offset and different elevations of the boat’s lifting eyes. A Modulift MOD400 was used at a 29 m span beneath 29 m long and 26.4 m long top slings to balance the lift. Two MOD70H beams were used underneath, one at 5.5 m long and the other at 4 m.
Two different lengths of sling were used to connect them to the top beam — 3 m at the stern (back) and 3.9 m at the bow (front). The slings that met the lifting eyes at the bottom of the rig were all 4m in length.
Completely Level Lifting
Danny Skidmore, heavy cranes manager at Osprey, said: ‘We had to work closely with shipbuilders and naval architects, and refer to CAD, to devise a method of lifting the catamaran safely and completely level. The previous time we lifted such a vessel, we used two cranes in tandem, but mobilising two cranes of that size represents a large-scale operation and high costs, not to mention the disruption it has on the shipyard. We wanted to come up with a way to minimise mobilisation and limit the impact on our client’s busy, marine environment.’
Central Support Sling System
Osprey consulted Modulift and FLG Services, principally on utilisation of the MOD400 at 29 m, which usually has a maximum span of 24 m. Sue Spencer, technical director at Modulift, said: ‘It was more cost effective and convenient for Osprey to source the beam from a rental partner versus a custom designed product. Our technical team looked into the feasibility, and came up with a solution whereby a central support sling system would be required to support the self-weight of the main spreader beam to minimise any potential deflection—and this adjustable sling system would need to be attached vertically to the crane hook.’
She added: ‘We devised a design whereby the tension load in the central sling could be monitored using a wireless load link to ensure that the sling was carrying the correct share of the self-weight of the beam throughout the lift, with the means to adjust the tension by way of a chain block. The customer monitored the tension throughout the lift to ensure that it did not go outside specified parameters.
Picture: A central support sling supported the self-weight of the spreader beam to minimise its deflection.
