Hydraulic and earth engineering – Subterranean or submarine pipe or cable laying – retrieving,... – Submerging – raising – or manipulating line of pipe or cable...
Patent
1995-10-20
1998-03-03
Graysay, Tamara L.
Hydraulic and earth engineering
Subterranean or submarine pipe or cable laying, retrieving,...
Submerging, raising, or manipulating line of pipe or cable...
405159, 405158, F16L 112
Patent
active
057227934
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method and device for continuously laying and burying a flexible submarine conduit, for example an optical fibre transmission cable.
The growth of international and even intercontinental links by means of submarine cables, in particular by means of telecommunication cables such as telephone cables, has lead researchers to design and manufacture methods and devices for laying long lengths of cable on the sea bed.
At an early stage it became apparent that merely laying a cable on the sea bed is unsatisfactory in many cases. The cable is subject to frequent aggression of various kinds, for example by ships' anchors, fishing boats' nets, the effects of swell and currents and the movement of the cable laying vessel itself. One solution is to protect the cable by providing it with reinforcing armouring to increase its mechanical strength and its weight over that part of its length down to a depth of approximately 1000 m. Beyond this depth, experts regard the risk of damage to the cable due to fishing and shipping activities to be negligible.
Another known technique is to lay a layer of gravel or pebbles on top of the cable, known as "gravel dumping", or sacks of sand or cement. In some cases the weight of the cable is increased sufficiently for it to become buried in the sea bed of its own accord.
A further solution, in increasingly widespread use, since it offers improved cable protection, is to bury the cable in a trench dug into the sea bed.
When two distant points are to be linked by a submarine cable a specialised cable ship is employed having storage means, baskets for example which are adapted to contain all of the cable to be laid, a sea plough that is used to bury the cable and all the mechanical, hydraulic and power equipment needed for laying the cable and to operate the sea plough.
The first operation is to pay out one end of the cable from the cable ship so that this end can be taken ashore. The cable ship and the shore are separated by a distance of several hundred meters, possibly more than one kilometer. During this first landing operation the heavy cable is dragged along the sea bed, generating high friction forces. The cable can be lightened so that it floats on and is drawn along the surface, but in this case the cable is subject to high loads due to swell and currents. In all cases it has been proved necessary to reinforce the cable in the part drawn ashore.
The second operation is to submerge the sea plough, linked to the cable ship by the towing cable adapted to withstand loads of several tonnes. The sea plough is controlled from the cable ship by means of an umbilical link and buries the cable as the cable ship moves forward and as the cable is laid on the sea bed.
To bury the part of the cable laid without burying it in the landing area, which therefore remains exposed on the sea bed, it is necessary to use different specialised equipment to carry out a procedure known as burying after laying.
A major drawback of this procedure is that it involves several different operations, including cable protection operations, and several different items of equipment.
Another drawback is that long lengths of reinforced cable have to be put on board the cable ship, the reinforcement of the cable increasing its diameter and its weight and representing an additional load for the cable ship and the equipment, especially the sea plough. The costs of laying is substantially increased, as is that of manufacturing the cable, of course.
The same operations naturally have to be carried out on reaching the other end of the link, with the same drawbacks.
When the cable is relatively fragile and light in weight, as is the case with an optical cable, the reinforcement must be proportionately greater.
The present invention aims to remedy the above drawbacks and to provide a simultaneous cable laying and burying method that is easy to use.
An object of the present invention is to carry out cable laying and burying simultaneously in one operation covering a landing area and an offsh
REFERENCES:
patent: 3434297 (1969-03-01), Gretter et al.
patent: 4010619 (1977-03-01), Hightower et al.
patent: 4190382 (1980-02-01), Schmitz et al.
patent: 4362436 (1982-12-01), Harmstorf
patent: 4492492 (1985-01-01), Izawa et al.
patent: 4537530 (1985-08-01), Yamamura et al.
patent: 4749308 (1988-06-01), Izawa
patent: 4812079 (1989-03-01), Johnson et al.
patent: 4892443 (1990-01-01), Kunze et al.
Baumaschine & Bautechnik--BMT, vol. 28, No. 6, Jun. 1981, Wiesbaden DE pp. 301-303; Christian Benoit p. 302, paragraph 6.
NTT Review, vol. 4, No. 5, Sep. 1992, Tokyo JP pp. 100-102, Yoshiki Shiba et al, "Underwater Robot for Submarine Cable Maintenance".
Petrole Et Entreprise, No. 32, Mar. 1986, Paris FR pp. 16-18, Claude Burckbachler et al "Les aterrages".
Coflexip
Graysay Tamara L.
Lagman Frederick L.
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