New-generation cable-lay vessels have several features in common, not least significant cable-installation capacity and environmentally friendly operation
Recent weeks have seen one highly specified cable-lay vessel enter operation, with another due to follow into service shortly. Prysmian’s new cable-lay vessel Leonardo da Vinci was delivered in August 2021, shortly after another newbuild, Nexan’s Nexans Aurora was delivered.
Both can transport and install significant amounts of cable, have DP3 class dynamic positioning and can operate in an environmentally friendly manner.
Like other new-generation cable-lay vessels, Leonardo da Vinci and Nexans Aurora’s large cable-loading capacity compared with earlier units enable them to install cables with fewer joints and spend less time in transit to port to load cable.
Leonardo da Vinci will be able to carry out cable laying and burial operations simultaneously, thus shortening the time required to undertake large-scale projects such as export cables and interconnectors. It is also designed to provide an especially high level of flexibility and install cables in deep water of more than 3,000 m when required. It has two carousels, one of 7,000 tonnes capacity and one of 10,000 tonnes.
Prysmian’s new vessel will have two independent laying lines to increase flexibility and a bollard pull of more than 180 tonnes, allowing it to undertake simultaneous laying and cable burial, supporting a variety of burial machines, such as heavy-duty ploughs and the company’s Hydroplow.
Designed to undertake bundled cable laying in addition to simultaneous laying and burial, the new vessel has a length of approximately 172 m, a beam of 34 m and accommodation for 120 people.
The vessel’s propulsion system is designed to reduce the ship’s environmental footprint. With a speed in transit of more than 14 knots, Leonardo da Vinci has a hybrid propulsion system of a type increasingly adopted for use on offshore vessels. On this vessel, it takes the form of six diesel generators and two battery-based energy storage systems, each of 750 kW, providing the vessel with a total of 21 MW. The battery power will assist with peak shaving, when energy demands on the vessel are high, and will help to reduce fuel consumption.
The first project assigned to Leonardo da Vinci vessel is the installation of the Viking Link submarine cable connection between the UK and Denmark, the world’s longest power interconnection. In mid-August, the vessel arrived at the Arco Felice plant – one of Prysmian’s four centres of excellence for producing submarine cables – to load cable for the project. Later in 2021, it will execute another interconnection project, between the Spanish islands of Lanzarote and Fuerteventura and install the cabling on the Saint Nazaire offshore windfarm in France.
Prysmian Group also recently finalised a contract with RWE Renewables for the high-voltage submarine and land export cable connection for the 1.4-GW Sofia offshore windfarm in the North Sea, a project for which Leonardo da Vinci will also be used. The group announced it had been selected as the preferred bidder for the project in November 2020. The contract is worth more than €200M (US$244M).
Nexans Aurora was delivered in June 2021, shortly before Leonardo da Vinci. Designed to transport and install subsea cables and undertake related subsea construction work, the vessel is fitted with purpose-designed equipment for cable and umbilical transport and laying, including bundle laying, protection and jointing.
Nexans Aurora is also a DP3 vessel and the ST-297 design from Skipsteknisk in Norway is designed for installing HVDC and HVAC cable systems and for deepsea and nearshore cable-laying. The design was developed for operation in rough weather and has high levels of manoeuvrability and stationkeeping. The vessel is 149.9 m long with a deadweight of 17,000 tonnes and can accommodate 90 people.
In addition to power cables for export lines for offshore wind and deepwater interconnector projects, it can carry and deploy fibre optic cables, repairing and jointing cables and will operate a seabed trenching machine.
Much of the cable-laying equipment for the vessel was designed by MAATS Tech in the UK, including the vessel’s carousel, which will carry cable in an innovative ‘carousel-in-a-carousel’ arrangement that will allow it to carry more cable without significantly increasing the vessel’s size or cost. The concentric carousel-in-a-carousel concept on Nexans Aurora can process two cables simultaneously or store a single length weighing 10,000 tonnes. The vessel will have two firing lines.
MAATS tells OWJ, “[The] system consists of an on-deck, concentric, 10,000-tonne carousel and two separate firing-line deck-spread systems, one line utilising a capstan lay solution while the other adopts two twin-track 25-tonne tensions, each providing four points of contact to the product.” Complementing the system are a range of heavy-duty roller pathways, two loading arms and stern lay wheels, all of which help enable laying in deep water, harsh conditions and rough weather.
There is also space for a container garage with handling systems and storage positions for nine 20-ft containers arranged inhouse. “This enables efficient mobilising and demobilising between missions,” designer Skipsteknisk tells OWJ. “An automated handling system for up to eight workboats is situated in a protected area on deck.”
The vessel is also designed to be environmentally friendly and has ‘Silent-E’ class notation from DNV. “Our first concern is that our operations do not have a negative impact on the environment, and this extends to underwater radiated noise,” explains Nexans group project manager Frode Beyer, citing specific local requirements that are designed to protect vulnerable surroundings.
Nexans recently signed a preferred supplier agreement with Empire Offshore Wind to connect the company’s offshore wind projects to the grid using Nexans Aurora. The company’s chief executive Christopher Guérin says the deal “demonstrates the value of our end-to-end model and supports our investment in US offshore wind and our new cable-laying vessel.”
Al Gihaz Holding acquires Enshore Subsea
Al Gihaz Contracting, part of Al Gihaz Holding, has acquired the assets, intellectual property and management systems of Enshore Subsea Ltd, the UK-based subsea trenching company. The acquisition will see the creation of a new joint venture with the aim of forming a leading seabed intervention and construction management services provider. The joint venture will rely on the acquired assets and the company’s successful track record of completed projects.
The deal came after DeepOcean commenced a restructuring process in late 2020 in relation to three UK subsidiaries in its cable-laying and trenching business that will enable the group to be wound down on a solvent basis. DeepOcean 1 UK Limited, DeepOcean Subsea Cables Limited and Enshore Subsea Limited filed a practice statement letter that informed creditors of the companies’ intention to propose restructuring plans to their creditors and the objectives of those plans.
Enshore Subsea will be based out of its existing facility at Port of Blyth in the UK, which is well-suited to serving the European offshore wind and offshore oil and gas markets. The company will provide services including subsea engineering and construction management, manpower supply and equipment rental for subsea trenching, seabed intervention, development of seabed tooling technology and submarine flexible product installation.