DEME Group’s new cablelay vessel Living Stone has already been awarded three contracts – proof if any were needed of its extremely high-spec design and cost-effective mode of operation
Due to enter service shortly, Living Stone, DEME Group’s new cablelay, trenching and rock installation vessel, has a considerable backlog ahead of it.
The first project it will undertake will see it install the inter-array cables on the Merkur offshore windfarm in the North Sea. The second contract, awarded by Dong Energy to Tideway, a subsidiary of DEME, will see the ship install the cabling for the Hornsea Project One offshore windfarm. The third project is an interconnector job.
For the Hornsea Project One contract, Tideway will deploy DEME’s dynamic positioning class 3 vessel to install the cables on what will be the world’s largest offshore windfarm. The scope of work to be undertaken by Tideway includes cablelay, pre-trenching, backfilling, pre-sweeping, route preparation and rock placement for three high voltage subsea power cables from three offshore substations to the shore, as well as the installation of two interlink cables.
Describing the contract and the company’s role in it, Hugo Bouvy and Lucas Bols, directors at Tideway, said the work on Hornsea Project One would make use of the vessel’s innovative, modular cable/umbilical-handling system, which has a 10,000-tonne cable capacity divided over two turntables, both of which are arranged below deck.
The second contract that will be undertaken by Living Stone was awarded to Dredging International, also part of DEME Group, which has secured a contract from Belgian transmission system operator Elia to install the power cables for a modular offshore grid in the North Sea.
DEME will use a number of newly built vessels from its fleet to carry out the work, including Living Stone and the trailing suction hopper dredgers Minerva – the first of its type in the world with dual-fuel liquefied natural gas (LNG) propulsion – and Scheldt River. DEME will use Minerva and Scheldt River to prepare the seabed before installing the cable from Living Stone.
Elia’s modular offshore grid includes a substation located about 40 km off the coast of Zeebrugge to which four windfarms will be connected. Submarine cables will link the platform with a substation in Belgium, where electricity from the windfarms will be injected into the Belgian grid. The contract includes the supply, installation and maintenance of the submarine power cables. One 220 kV power cable will be installed along a 4.5 km route between the substation and the first windfarm. Two 220 kV submarine power cables of approximately 39 km each will be installed from the substation to the onshore connection point at Zeebrugge.
Like Minerva, Living Stone also has dual-fuel engines and will use LNG as its primary fuel. Built at Spanish shipyard LaNaval, the vessel’s turntables can transport more than 200 km of cable. With deck space of 3,500m2 and an innovative cable-handling system with cable-handling tools for cable ends, connections and cable protection systems accommodated on deck, Living Stone can also be equipped with a third carousel with an additional loading capacity of 2,000 tonnes, if required.
Complementing this huge cable-carrying capacity are remotely operated vehicles and a subsea trenching tool and fallpipe system that will be used to lower rock to protect cables once they have been installed. The vessel also has a 7.7 m by 7.7 m moonpool and a 600-tonne crane for the installation and removal of subsea structures and will provide accommodation for up to 100 people. It can be also be fitted with a 65-tonne safe working load A-frame that will have a telescopic docking frame and a winch with slack motion compensation.
Unsurprisingly, given all of the above-mentioned capability and technology developed in house by Tideway, DEME claims that Living Stone will install cables more quickly and more efficiently and in longer lengths and with fewer offshore joints than any other cable installation vessel.