Heavy lift and transport company ALE has lifted and installed a topside weighing 10,000 tonnes at DryDocks World, Dubai, United Arab Emirates.
The topside is the world’s largest first semisubmersible HVDC platform. It is named the DolWin Beta and was constructed at the DryDocks shipyard. The gantry system used to lift the topside was created by ALE’s research and development department at ALE in Breda, Netherlands, and at the Middle East branch, a company spokesperson said.
ALE used four laced tower systems and two A-frame structures. Side braces were also incorporated into pre-cast concrete foundations in the dock pier walls to provide stability and a ballast securing system for bad weather.
In addition to each gantry tower, four strand jack units were installed, for a total of 24 strand jacks at 500 tonnes each.
Once a test lift had been carried out, the topside was lifted clear of its supports and suspended while the topside was prepared for the full height lift. ALE lifted the topside to a final height of 52.8 metres. Once at full height the semi-submersible hull structure was manoeuvred in between the ALE gantry system and underneath the suspended topside. The topside was then positioned on the semi-submersible hull structure and welded into place.
Edward Talbot, ALE project manager, said, “For our client this was a first and, as such, a lot of design work, verification and detailed checks were completed to ensure full integrity of the entire system during the operation. Our aim was to execute the lift efficiently with minimal risk to the topside and surrounding yard activities.
“Usually a lift such as this would rely upon a very restrictive weather window requiring extended periods of relatively low wind speeds to affect the lift and integration safely." It was up to ALE to create a system that was capable of withstanding 10 year return wind loads but that would not cause permanent disruption to the operability of the dock.
“The design meant that our client could not only perform the mating operation inside the dock but also maintain adjacent docking operations with minimal impact to the yard facility during and after lifting and mating completion,” ALE said.