Pioneering Spirit Gets 20,000-Tonne Floating Sheerlegs System
The giant offshore decommissioning vessel Pioneering Spirit has loaded a new sheerlegs system onto her back deck, giving her the capability to hoist both platform topsides and platform jackets. It will have a capacity of 20,000 tonnes, making her the world's largest floating sheerlegs by a factor of two (in addition to her other world records).
Pioneering Spirit, the world's largest vessel by displacement, was purpose-built for two highly specialized tasks - laying pipe and removing topsides. She has a unique fast-lift hydraulic system on two forward pontoons, which she uses to rapidly lift and remove an entire 48,000 tonne topside module in one go.
That system does not work for jackets, though, and that line of work has previously been reserved for ultra-large crane ships. No longer: Allseas has commissioned two giant lifting beams to mount on Pioneering Spirit's stern, turning her into a floating sheerlegs when needed. Uniquely, the legs are hinged and equipped with a jacking system that lowers them back onto deck for transit. This will allow the vessel to pick up a jacket and lay it flat on board before heading back to port.
Allseas said that the moment of truth for the beam installation was in lining up each main hinge between two giant deck-mounted eyes and inserting the hinge pins, which are more than four feet in diameter.
“To perform this operation, the beams were placed on the same skid system that was used to position the New Safe Confinement dome over the fourth Chernobyl reactor two years ago,” said Florian Wasser, Allseas Manager Capital Projects. “With the ability to manipulate the position of thousands of tonnes within tens of millimetres, the pins went in accurately and smoothly."
The first steel for the sheerlegs system was cut two and a half years ago, when Pioneering Spirit's pipelay work on the TurkStream and Nord Stream 2 megapipelines was nearing an end.