New unit can be fitted with jetting installation, a mechanical chain cutter or a combination of both
Jan De Nul Group has signed an agreement with Osbit Ltd (UK) for the design and construction of a new subsea trenching vehicle, which it will call ‘Swordfish.’ Delivery is scheduled for Q1 2022.
Swordfish will be a high-powered subsea trenching vehicle that can be fitted with jetting installation, a mechanical chain cutter or a combination of both to tackle a wide variety of soil conditions and bury cables up to 3.5 m deep.
Jan de Nul manager offshore cables Wouter Vermeersch says, “Swordfish makes a perfect addition to our existing fleet of trenching vehicles. With its high power, Swordfish will be able to bury the cables deeper and thanks to its hybrid mechanical chain-cutting configuration Swordfish can also tackle more challenging soil conditions, including hard clays up to 400 kPa. This new investment, together with the recent acquisition of our cable installation vessel Connector, arms Jan De Nul Group for the energy transition.”
Swordfish will be powered by two 300-kW hydraulic power units and two 300-kW electric high-pressure jet pumps.
In jetting configuration, it will be capable of tackling soil strengths up to 125 kPa, thanks to its 1,120 kW of pump power. In mechanical or hybrid mode, it will be able to cope with soil strengths up to 400 kPa using its 400-kW chain-cutter tool and 420 kW additional jetting power.
The main jetting tool is combined with front cutting nozzles and additional rear backwash swords to optimise trenching performance. Using modular buoyancy, the underwater weight of the vehicle in jetting mode is less than 1 tonne, resulting in a ground pressure not exceeding 5 kPa which allows trenching vehicle operation in very soft soil conditions.
The innovative chain-cutter design and cable-loading system minimise cable handling and have the added benefit of a closed-box depressor to guarantee first-time-right protection.
The trenching vehicle will be launched with a dedicated A-frame and hoisting winch from one of Jan De Nul’s offshore vessels.
The company already operates three trenchers, Sunfish, Moonfish and Starfish. Sunfish and Moonfish were developed specifically for use on the export cable project for the Race Bank offshore windfarm in the UK. The intertidal trenching vehicles were the subject of several industry awards for their innovative design and were subsequently modified and used in support of several other cable installation and protection projects in the European offshore wind market.