Allseas Deploys New Jacket Lift System (video)

Offshore engineering specialist Allseas has deployed for the first time a new jacket lift system mounted on its Pioneering Spirit construction vessel for a decommissioning project in the UK’s North Sea.

The system was used to hoist an 8,100-tonne steel jacket structure from CNR International’s Ninian Northern crude oil platform, located some 160 kilometres northeast of the Shetland Islands in Scotland.

Once loaded onto the Pioneering Spirit, the jacket was then transported to the deepwater port of Lerwick in Shetland for dismantling at the Veolia-Petersen recycling yard.

“Main hoist blocks suspended from the JLS beams were attached to the jacket top by means of bespoke rigging (built by Allseas Fabrication) and, after final cuts, the 85-metre structure lifted safely out of the water,” the company said.

“The jacket was subsequently aligned with the beams and lowered onto the main aft deck for transit to the Shetlands.”

The twin-hulled Pioneering Spirit was called into action two years ago for the single-lift removal of Ninian Northern’s 14,200-tonne topsides.

The vessel, which began operations in 2016, is 382 metres long and 124 metres wide, and is designed for the single-lift installation and removal of large oil and gas platforms and installation of record-weight pipelines.

The hulking unit is capable of lifting entire platforms weighing up to 48,000 tonnes and jackets up to 20,000 tonnes in a single piece.

For jacket installation and removal, two 170-metre-long beams designed to rotate on hinges are deployed at the Pioneering Spirit’s stern, along with a 5,000-tonne special purpose crane for additional lifts such as lighter topsides and jackets, modules and bridges.

“This advanced technology enables direct transfer of structures to and from the quayside and eliminates the need for support barges. There is no need to seafasten the jacket to the beams during transit due to the vessel’s high level of stability, significantly reducing time in the field and lowering the emissions footprint,” Allseas said.

Pioneering Spirit is expected to lift and transport more than 123,000 tonnes of structure for the offshore energy industry this year, utilising both its jacket lift and motion-compensated topside lift systems.

In addition to heavy-lift operations, Switzerland-based Allseas also specializes in offshore pipeline installation, deep-ocean polymetallic nodule collection and river waste collection.

Watch a video of Allseas' new jacket lift system: