How our cable-laying vessels work
Helping to connect islands, wind farms, oil rigs and people.
In 2017, the 170-km long Maritime Link Project, which transports renewable electricity from Newfoundland and Labrador, was completed. The bulk of the link – two 6,000-tonne high voltage cables installed in Canada’s Cabot Straight down to a 470-meter depth – only took 14 days to lay each of the two cables down underwater.
The quick installation process is partly credited to one of the greatest unsung heroes of the Maritime Link and other similar vast infrastructure projects: Nexans’ state-of-the-art subsea cable-laying vessels, which can carry up to 7,000 tonnes of cables, and lay them on the ocean floor at a speed of up to 20 meters per minute.
So, how exactly do these mighty cable-laying ships work?
Initially, Nexans works closely with customers to carefully survey where the cables will be installed so the ideal route can be planned. Once this phase is complete and subsea cable is manufactured, assuming the weather is calm – without big waves, high winds or strong currents that can pose challenges to the cable-laying process – the cable is lowered from the vessel and into the water. During the pull-in process to shallow water, the cable is supported by floats that prevent the cable from sinking so it can be moved with ease.
Meanwhile, in separate smaller workboats, a team of experts carefully handles the cable, guiding it to shore and maintaining a proper bending radius so the cable is not damaged.
Once it has reached land, it’s pulled into place by an onshore winch. The floats are then removed, allowing the cable to sink down to the seabed.
For deep-water installations, the cable-laying vessel can lower cable right into the water And along the way, precautions are taken to snake cable around large rocks or other potentially hazardous obstacles.
A remote operating vehicle (ROV) monitors and operates cable touchdown on the sea floor, helping to adjust the cable angle and tension as needed.
Finally, for both shallow and deep-water installations, Nexans has developed a high-tech cable protection system called CAPJET that uses a trenching tool manufactured in-house to bury cable up to three meters beneath the seabed. This is the last step in the cable-laying process and helps to protect the cable from ship anchors, fish and other possible disruptions.
Starting in 2021, cable-laying productivity will reach new heights – and depths – as Nexans launches its newest cable-laying vessel: Aurora. The 150-meter-long vessel, specifically designed for rough weather and high manoeuvrability, will be able to hold 10,000 tonnes of vital cable, helping to make new and more powerful connections underwater for years to come.