A 10,000t topside lift
17 April 2014ALE has used a specially designed gantry system to perform a lift and mating operation of a 10,000t topside at Drydocks World for a semisubmersible HVDC platform DolWin Beta that was constructed at the shipyard.
ALE's R&D department at ALE in Breda, Netherlands and the Middle East branch combined various standard gantry types into one system to make the lift possible. Drydocks World carried out an assessment of topside structural strength, weight calculations and designed the heavy lift pad eyes to suit the lifting arrangement of ALE.
The topside was lifted from six consoles, four using ALE's laced tower system and two A-frame structures positioned centrally to create longitudinal stability. The system also incorporated side braces into pre-cast concrete foundations in the dock pier walls for transverse stability and a ballasted securing system that could be activated to lock-down the lifted topside if weather conditions suddenly changed.
On top of each gantry tower, four strand jack units were installed giving a total of 24 strand jacks with a minimum capacity of 500t each to lift the topside. ALE said that specialist equipment and personnel were mobilised from across the group to build and operate the gantry system, and the system was set-up for maximum flexibility and accuracy during the mating process.
After a test lift the topside was lifted clear of its supports and suspended in order to prepare the topside for full height lift. The lifting firm said that during the project weather was a constant challenge and all teams worked together to reduce this clear weather window from 5 to 3 days. ALE lifted the topside to a final height of 52.8m in phases, in between which, careful and precise removal of the support barge undocking and docking of the substructure was effected by Drydocks World. Once at full height the semi-submersible hull structure was manoeuvred in-between the ALE gantry system, underneath the suspended topside. ALE then lowered the topside to the precisely positioned substructure, releasing weight in a controlled fashion under careful guidance of the technical personnel of Drydocks World. Welding of the two structures was carried out in parallel with the precise lowering operation.
