DECK EQUIPMENT & LIFTING GEAR
JACKET LIFTING SYSTEM COMPLETES FIRST DEPLOYMENT Allseas’ Pioneering Spirit’s recent 8,100t lift is barely a third of its new system’s lifting capacity The new jacket lifting system on Pioneering Spirit, the construction vessel designed and owned by Allseas, has completed its first deployment and lifted an 8,100-tonne jacket from a gas production platform in the North Sea in a single lift. And although the lift is considered one of the heaviest offshore jacket lifts ever, the weight is still well within the system’s lifting capacity of 20,000 tonnes, Allseas says. The eight-legged jacket was lifted a week after the Pioneering Spirit arrived in the Ninian gas field, 160 km northeast of the Shetland Islands. It has been lowered onto the deck of the vessel and will be delivered to the Veolia-Peterson yard in Dales Voe, which aims to reuse 98% of the steel it deals with. Allseas says the lifting system is different from conventional crane-lifting vessels in that it is aft mounted and comprises two connected 170-metre long beams that lift and support jackets of all sizes during removal and installation operations. ”The original idea for a jacket lift system dates back to the late 1980s, when Allseas’ concept for a vessel capable of lifting entire platforms in a single lift was unveiled,” said Kristian Hall, communications officer for Allseas. ”There were numerous tweaks to the design before a decision on the final design was made several years ago. Fabrication got under way in 2019. The aft-mounted jacket lift system is the vessel’s second unique lifting system. The bow is fitted with a motion-compensated topsides lift system (TLS), capable of lifting entire platform topsides up to 48,000 tonnes.
Although the lift is considered one of the heaviest offshore jacket lifts ever, the weight is still well within the system’s lifting capacity of 20,000 tonnes “It is fundamentally different from conventional cranelifting vessels. When removing large jackets, conventionally they need to be cut up into small sections suitable for crane lifts, requiring lengthy and weather-sensitive, complex subsea cutting operations. Pioneering Spirit removes and installs jackets weighing up to 20,000 t in a single lift, thereby limiting subsea work and associated risks. In essence, our vessel is in the field only days compared to months required by smaller vessels. ”Jackets are lifted over the stern, for which the vessel is repositioned. After cuts have been made in the foundation piles at seabed level, or above the pile clusters as required, the main hoist blocks suspended from the 170-metre long main beams raise the jacket at the main legs. The jacket is subsequently aligned with the beams and lowered onto the deck for transit to a disposal yard. The system also enables the transport of jackets in a near-vertical position to safeguard structure integrity.” The jackets can be transported in a near vertical position to
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safeguard structural integrity, and direct transfer to and from the quayside means support barges are not required. ”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.” Ninian Northern is the first of several major jacket removal and installation commitments for Pioneering Spirit in 2022. The vessel will lift and transport more than 123,000 tonnes of structures for the offshore energy industry this year, utilising both its jacket lift and motion-compensated topsides lift systems. All of Allseas’ vessels and equipment are designed entirely in house, said Hall. Some elements are built by the company’s fabrication unit, he says, while larger, more technical subsystems are subcontracted to sites around the world belonging to the likes of Huisman, Cimolai and Remazel. All elements were transported to Rotterdam and installed and integrated in stages, with commissioning, testing and certification completed earlier this year.
8 Pioneering Spirit’s new jacket-lifting system
8 Pioneering Spirit
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