Torqueing Undersea Cables

Fraser Hydraulic Power, a family owned company based in Newcastle Upon Tyne, have developed an interesting solution to overcome some of the problems associated with the laying of the latest generation of subsea Telecommunication cables.

For many years the machines for laying the cables on the seabed have been hydraulically driven. The old cables were heavy and rugged and hydraulic systems proved to be the most reliable, suiting the arduous conditions on the exposed decks of vessels at sea.

Now Fraser's (like many other companies) are faced with new challenges as the introduction of Fibre-optic cables begins to replace old armoured copper based cables.

During laying operations a large plough is towed behind a ship at a approximately 6 knots, typically at depths of 1000m and up to 2000m behind the ship. The plough opens up a furrow and the cable is fed into the trench. The same plough then back fills the trench to cover the cable. All of this happens as a continuous operation. It is essential that the tension in the telecommunications cable being layed, is maintained within predetermined limits to suit the laying conditions and the type of cable being used. Failure to maintain tension can cause the cable to foul up on the plough or on the towing vessel and if there is too much  tension the cable can break. With typical repair costs for cable damage being around £100k, it is imperative that the cable is not damaged.

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