A high level of flexibility, redundancy and ballast water-handling capability characterise a new class of semi-submersible heavy-lift vessels managed by GPO Heavylift in Norway
GPO Grace, the first of a quartet of high-spec semi-submersible heavy-lift vessels, entered service in 2017 and will be followed into service by a second unit later this year. Two more examples of the type are due to be delivered to their owner in 2019 and operated by GPO Heavylift, a company formed in 2014 to operate the semi-submersible vessels.
Intended for dry transportation of offshore drilling rigs, modules and other heavy cargo, the four vessels – GPO Grace, GPO Amethyst, GPO Sapphire and GPO Emerald – can transport jack-up drilling rigs, semi-submersible drilling rigs, dredging equipment, cranes, barges, other floating cargo and offshore and onshore modules.
Towards the end of last year, GPO Grace completed a maiden voyage from Thailand to Norway with the module support frame for Statoil’s Johan Sverdrup drilling platform. Having delivered the module support frame for Johan Sverdrup, GPO Grace has secured a number of other projects since and most recently discharged cargo in Brazil, after which it was due to transport a cargo of barges to Egypt.
As Dagfinn Thorsen, managing director of GPO Heavylift, told OSJ, the design of the heavy lifters draws on around 25 years of experience in the market. The market for semi-submersible heavy-lift vessels may not be enjoying the best right now, he agreed, but the number of enquiries the company is receiving is picking up, and the new vessels have been well received by potential clients.
At 25 m overall and with a breadth of 48 m, the dynamic positioning class 2 vessels have free deck space of 183 m x 48 m and a deadweight of 64,000 tonnes. Designed to submerge to a depth of 15.00 m, they benefit from a particularly high level of redundancy (and have RPS class notation from DNV GL) and manoeuvrability.
With controllable pitch five-bladed propellers that can be feathered in the event of a problem with one of them, enabling the remaining unit to maintain full thrust, they have four tunnel thrusters (two fore and two aft) and Becker rudders. Loading/discharge can be undertaken by floating the cargo on board, skidding, rolling or by lifting. Designed with a uniform deck strength of 30 tonnes/m2, the new vessels have a point strength of 1,500 tonnes/m2 and line strength of 300 tonnes/m2.
Mr Thorsen explained that the ballast water system for the vessels is also unique on this kind of vessel in as much as it makes use of pumps rather than compressed air, which makes ballasting when skidding loads onto the deck especially flexible and responsive.
Another interesting if not unique feature of the vessels is the buoyancy towers, which can be moved around the deck by the ship’s crew in order to facilitate loading via the stern. The ships are thus capable of stern or side load-out operation and of discharging their cargo by float-over operation.
Owner/manager GPO Heavylift
Builder CSBC Taiwan
Length 225.00 m
Breadth 48.00 m
Free deck space 183 m x 48 m
Depth 13.80 m
Draught 10.68 m
Deadweight 64,000 t
Submerging depth 15.00 m
Bow thrusters 2 x 1,750 kW
Stern thrusters 2 x 1,000 kW
Propulsion 2 x 8,000 kW
Class DNV GL + 1a1 Semi-Submersible Heavy Transport Vessel, E0, Dynpos-AUTR, Clean, DK(+), RPS, PDWK, Coat-PSPC(B), BIS, TMON, Ice-1c, Naut-OC