GB1594702A

GB1594702A - Armoured cables

Info

Publication number: GB1594702A
Application number: GB3713877A
Authority: GB
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC
Priority date: 1977-09-06
Filing date: 1977-09-06
Publication date: 1981-08-05
Also published as: FR2402283B1; FR2402283A1; DE2838577A1; DE2838577C2

Description

(54) ARMOURED CABLES (71) We, STANDARD TELEPHONES AND CABLES LIMITED a British Company of 190 Strand, London W.C.2. England, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to electric cables, particularly cables intended to withstand heavy tensile loads.

Underwater cables often have to withstand heavy tensile loads. For example undersea transmission sytems utilise cables which are laid in great depths of water and have to be strong enough not only to be laid from a ship but also to be recovered from the sea bed in the event of a fault or breakage occurring.

Cables are used underwater for other purposes, for example diving in which the cable provides not only electrical power and telephone transmission and telemetry circuits, but also oxygen/helium facilities.

Underwater cables are also used for underwater vehicles for remotely controlling the vehicle and providing TV control telemetry and power circuits. Underwater cables are also designed for surveys in which heavy underwater survey devices are towed using the cable which also provides control, telemetry and power circuits. Some underwater cables are purely used for control for example to supply power and control circuits for the sea floor well head systems used at oil drilling installations in, for example, the North Sea.

All these cables have to withstand high tensile loads, in some cables up to 150 tons.

According to the present invention there is provided a flexible elongate member comprising a laid-up bundle of sub-units including at least one hose for conducting fluids and at least one optical fibre or insulated electric wire for conducting light signals or electricity, the hose and the wire or fibre being laid-up in a first extruded plastics sheath, and at least one helical layer of flexible tensile strain elements over the first sheath which gives the member the tensile strength it is required to possess, at least some of the tensile strain elements each comprising an elongate wire of metal or high tensile plastics encased in a plastics sheath of rectangular cross-section.

In order that the invention can be clearly understood reference will now be made to the accompanying drawing which shows in cross-section an electric underwater strain cable according to an embodiment of the invention.

Referring to the drawing the cable comprises three triaxially arranged gas hoses 1, 2 and 3 laid-up around a central plastics filler member 4. In the interstices between the hoses are disposed three power cores 5, 6 and 7. Each power core is polyethylene insulated. In the external interstices between the power cores and the hoses are six screened pairs such as 8. It would also be possible to have optical fibres as well as or in place of some of the screened pairs. A polyethylene sheath 9 is extruded solid over the laid-up members (overall diameter 32" in the embodiment described) and two layers 10 and 11 of strain elements are applied over the sheath 9. The sheath 9 fills the external interstices but the internal interstices are empty or filled with a water blocking compound.

Each strain element in the layers 10 and 11 is shown in an enlarged cross-section in Fig. 1B and comprises a central high tensile steel strength member such as a galvanised plough steel wire 12 in the range 0.06 to 0.080 inches diameter encased in a high tensile plastics material 17, preferably polyeth leneglycolterephthalate (PGT). In the embodiment described the dimensions of the main body of each strain element measures approximately 0.10 inches by 0.20 inches. Each element has a rib 13 extending along one narrow longitudinal face and a correspondingly shaped recess or socket 14 extending along the opposite face. The pitch of the elements lies in the range 17 to 25".

These elements provide not only the tensile strength the cable is required to possess without additional strength members but also is resistant to abrasion and local dam age. In the event that the high tensile metal wire corrodes the PGT encapsulation would have sufficient tensile strength to enable the cable to be recovered intact from its location under water. In the dynamic mode, radial compressive forces on the inner cable components will be minimised.

The rib and socket arrangement permits the strain elements to be locked together without decrease in overall flexibility. However, the invention is not limited to strain elements with rib and socket configurations as shown in Fig. 1B but also plain rectangular elements as shown in Fig. 1C similar to that shown in Fig. 1B but without rib and socket 13 and 14. In that event the braid 15 and outer jacket 16 shown will be necessary to keep the strain elements in place giving an outer diameter of about 4A". The braid can be an interwoven layer of "Terylene" (R.T.M.) monofilament and the outer sheath polyethylene butylterephthalate which locks into the braid. It is envisaged that the strain elements could be preformed so that they resiliently tightly embrace the cable and thus retain their position.-It is also envisaged in the case of the embodiment of Figs. 1A and 1B that the outer sheath could be omitted.

The strain elements described can be used on cables in both the static and dynamic mode, that is to say cables which are permanently laid or fixed in position on the one hand, and, on the other hand, cables which are meant for towing underwater vehicles, etc.

It is also envisaged that the high tensile steel wires could be replaced by Kevlar particularly where the cable is intended to be buoyant or neutrally buoyant, i.e. the same specific gravity as seawater. This is particularly suitable for use underwater between well heads and surface platforms.

WHAT WE CLAIM IS: 1. A flexible elongate member comprising a laid-up bundle of sub-units including at least one hose for conducting fluids and at least one optical fibre or insulated electric wire for conducting light signals or electricity, the hose and the wire or fibre being laid-up in a first extruded plastics sheath, and at least one helical layer of flexible tensile strain elements over the first sheath which gives the member the tensile strength it is required to possess, at least some of the tensile strain elements each comprising an elongate wire of metal or high tensile plastics encased in a plastics sheath of rectangular cross-section.

2. A member as claimed in claim 1, wherein the elongate wire is of high tensile steel.

3. A member as claimed in claim 1 or claim 2, wherein the plastics sheath is a high tensile plastics material.

4. A member as claimed in claim 3, wherein the high tensile plastics material is PGT.

5. A member as claimed in claim 4 as appended to claim 3, wherein the elongate wire is in the range 0.06 and 0.08 inches in diameter and the high tensile plastics material of rectangular cross-section measures approximately 0.10 inches by 0.20 inches.

6. A member as claimed in any preceding claim, wherein the strain elements are held in position by an outer jacket closely embracing the outer surface of the elements.

7. An underwater strain cable substantially as hereinbefore described with reference to and as illustrated in Fig. 1A and Fig.

1B, modified or not by Fig. 1C, of the drawing filed with the provisional specification.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. age. In the event that the high tensile metal wire corrodes the PGT encapsulation would have sufficient tensile strength to enable the cable to be recovered intact from its location under water. In the dynamic mode, radial compressive forces on the inner cable components will be minimised. The rib and socket arrangement permits the strain elements to be locked together without decrease in overall flexibility. However, the invention is not limited to strain elements with rib and socket configurations as shown in Fig. 1B but also plain rectangular elements as shown in Fig. 1C similar to that shown in Fig. 1B but without rib and socket 13 and 14. In that event the braid 15 and outer jacket 16 shown will be necessary to keep the strain elements in place giving an outer diameter of about 4A". The braid can be an interwoven layer of "Terylene" (R.T.M.) monofilament and the outer sheath polyethylene butylterephthalate which locks into the braid. It is envisaged that the strain elements could be preformed so that they resiliently tightly embrace the cable and thus retain their position.-It is also envisaged in the case of the embodiment of Figs. 1A and 1B that the outer sheath could be omitted. The strain elements described can be used on cables in both the static and dynamic mode, that is to say cables which are permanently laid or fixed in position on the one hand, and, on the other hand, cables which are meant for towing underwater vehicles, etc. It is also envisaged that the high tensile steel wires could be replaced by Kevlar particularly where the cable is intended to be buoyant or neutrally buoyant, i.e. the same specific gravity as seawater. This is particularly suitable for use underwater between well heads and surface platforms. WHAT WE CLAIM IS:

1. A flexible elongate member comprising a laid-up bundle of sub-units including at least one hose for conducting fluids and at least one optical fibre or insulated electric wire for conducting light signals or electricity, the hose and the wire or fibre being laid-up in a first extruded plastics sheath, and at least one helical layer of flexible tensile strain elements over the first sheath which gives the member the tensile strength it is required to possess, at least some of the tensile strain elements each comprising an elongate wire of metal or high tensile plastics encased in a plastics sheath of rectangular cross-section.