GustoMSC's new self-propelled jack-up type, the NG-20000X, has been developed to combine high variable load capacity with the ability to access and operate within significant water depths. This is in anticipation of the increased weight and height required for most wind turbine components, as well as the weight of the forthcoming 10MW+ turbines – a far cry from the 3-5MW units that characterised the earliest, near-shore offshore wind farms.
Jan-Mark Meeuwisse, GustoMSC commercial director, comments: “Key to the new approach is to stop the spiralling trend of growing crane weights due to the increasing requirements related to the heavy foundations and high installation heights, and to stay close to the proven design technology at the same time.” Instead, he adds, the NG-20000X has been designed to “scale up the jack-up design and jacking system” and “solve the challenging crane requirements in an innovative manner”.
The NG-20000X would measure 152m x 58m, feature a hull depth of 12m and boast a variable load capacity of 16,500tonnes. As examples, Meeuwisse says, this would “enable the contractor to make a round-trip carrying six complete sets of wind turbine components with a turbine weight of 1,000tonnes, or carrying seven pieces of 900-tonne jacket foundations, optimising the cost per installed turbine or foundation”.
Intended for survivability in water depths of up to 70m, the NG-20000X would deploy triangular open truss, X-braced legs, each featuring an overall length of 120m (including the spud can) and a maximum length of 90m underneath the hull. The NG-20000X would incorporate a telescopic leg crane, developed in-house by GustoMSC in order to realise both significant hoisting height and the ability to handle heavy loads – which, the designer claims, could “break the cycle of extremely long, protruding booms and increasing crane weights”.
The crane would operate in two modes: extended mode, which would see it lift up to 1,250tonnes at an outreach of 47m and to a maximum height of 160m; and retracted mode, in which it will be capable of lifting 2,500tonnes at 30m outreach and to a top height of 120m above deck. GustoMSC explains that extending the crane boom by 40m from retracted to extended mode can be conducted within 16 minutes.
The crane has been designed so that, when the boom is stowed in the boom rest, it will not extend over the jack-up’s bow, to ensure minimum disruption to operations and to prevent obstructions to the helideck. GustoMSC adds: “A second boom-rest position outside the forward leg can be provided, freeing up valuable deck area to load multiple tall objects like jacket foundations.”
The NG-20000X concept would also utilise the GustoMSC VSD system, feature a deck area spanning some 5,600m² (strengthened to 10tonnes per m²) and provide accommodation for up to 130 persons.