ALE and Drydocks World collaborated to perform the lifting and mating of a 10,000-tonne topside (pictured below) using a bespoke gantry system, for the semisubmersible HVDC platform DolWin Beta.
The gantry system created by 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 top side structural strength, carried out precise weight calculations and designed of the heavy lift pad eyes to suit the tailor made 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 that provided transverse stability and a ballasted securing system that could be activated to lock-down the lifted topside if weather conditions were to deteriorate suddenly.
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. 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 the test lift, the topside was lifted clear of its supports and suspended in order to prepare the topside for full height lift. Weather was a constant challenge and all teams worked together to reduce this clear weather window from 5 to 3 days. This was done by carefully planning and combining Drydocks World marine capabilities and ALE lifting operations.
ALE lifted the topside to a final height of 52.8m meters 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 extremely carefully manoeuvred in-between ALE Gantry system, underneath the suspended topside.
The innovative fendering system designed by Drydocks World facilitated this process. ALE then lowered topside to the precisely positioned substructure thereby releasing weight in a controlled fashion under careful guidance of the technical personnel of Drydocks World. Welding of the two structures was carried out simultaneously in parallel with a precise lowering operation. The outcome of this team effort was a perfect Mating.
Edward Talbot, Projects Manager at ALE 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 effect the lift and integration safely. In this case it was up to ALE to create a system that was capable of withstanding 10 year return wind loads, however 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.”
About ALE (Abnormal Load Engineering)
Founded in 1983 by Roger Harries, ALE delivers a highly tailored, end-to-end service covering every aspect of the handling, transportation and installation of heavy, indivisible loads, including lifting, transporting, installing, ballasting, jacking and weighing.
ALE delivers strategic heavy-lift services to a wide range of sectors, including civil, oil and gas, energy, nuclear, offshore, renewables, petrochemical, ports, marine, minerals and metals and mining.
In 2008 it launched the AL.SK190, the world’s largest land-based crane, which it developed specifically for the lifting and installation of ultra-heavy loads and which is capable of lifting a record-breaking 4,300te and can be relocated on site fully rigged.
In 2011 ALE launched its ground breaking innovation – the Mega Jack system- capable of lifting 60,000te to a height of 25m the Mega Jack was developed to meet increasing demand in the offshore industry.
In 2012 ALE announced the building of the next generation AL.SK350 – the latest world’s largest capacity land based crane with a lifting capacity of 5000te.
ALE is headquartered in Staffordshire and has more than 30 offices across Europe, the Far East, Africa, America, South America, the Middle East and Australia. It is fully compliant with international standards of safety and excellence, including Quality standard ISO 9001