GB2183402A - Armoured cables - Google Patents

Abstract

An armoured submarine cable has a support collar 25 spaced from one end thereof and is secured to the armouring 26,27 of the cable on each side of the collar. The collar has an annular groove 24 which includes a radial shoulder which is downwardly facing when the cable adjacent the collar is disposed substantially vertically and which locates on flanges 23 of a support structure 21 in order to support a depending length 20 of the cable. If the cable is hooked by an anchor or trawl the dowels 34 shear so that excessive loads are not transmitted to the platform. The cable may be a power cable comprising one or more electric conductors, a telecommunications cable comprising wires and/or optical fibres or a hydraulic umbilical. <IMAGE>

Description

SPECIFICATION Armoured cables This invention relates to armoured cables,forex- ample armoured electric power cables which comprise one or more electric conductors, armoured telecommunication cables which comprisetelecommunication transmission elements such as wires and/or optical fibres, and armoured hydraulic cables which comprise one or more hydraulic conduits and are sometimes referred to as hydraulic umbilicals.

In one aspect the invention is concerned with enabling a depending length of an armoured cableto be supported, for example, from an offshore platform.

In this aspectthe invention provides an armoured cable having spaced from one end thereof a support collarwhich is secured to the armouring ofthecable on each side ofthe collar, said collar having a radial shoulder arranged to be downwardly facing when the cable adjacent the collar is disposed substantially vertically with said one end uppermostto enable a depending length ofthe cable adjacent the collarto be supported thereby. As will be appreciated the downwardlyfacing shoulder need only be located on afixed support in orderto support the depending length of cable.

Preferably the collar has a radially outwardly opening annular groove defined between said shoulder and a radial shoulder opposite thereto. The provision of such a grooveenablesthecollarto be located against upward and sideways movement relative to afixed support engaged with the groove.

Whilst the collar may befitted overthe armouring of the cable, preferably an annular section of said armouring is removed from said cable at the location of the collar and the thus formed free ends ofthe armouring are secured to opposed end portions of the collar. Also, preferably the thus formed free ends of the armouring are disposed overthe end portions of the collar.

The collar may be split lengthwise to assist fitting and preferably is obliquely axially split into a plura lity of segments -for example six to facilitate ben- ding of the cable.

Advatangeously, the collar is split into two long itudinal parts which are interconnected by fastening means adapted to shearwhen the collar is subjected to a predetermined tensile load.

In another aspect of the invention there is provided an armoured cable wherein an annular section ofthe armouring thereof is removed from the cable and the thusformedfreeendsofthearmouring are secured to opposed ends of a collar, said collar being split into two longitudinal parts which parts are interconnected byfastening means adapted to shear when the collar is subjected to a predetermined tensile load. Such a collar can be disposed anywhere along the length of the cable.

In orderthattheinventionmaybewell understood, some embodiments thereof, which are given by way of example only, will now be described with reference to the accompanying drawings, in which: Figure 1 is a part-sectional side view of a section of an armoured submarine power cable; Figure2 is an end view of a collar of the power cable of Figure 1; Figure3 is a part-sectional side view ofthe same collar; Figure 4 is a part-sectional side view of an end section of another armoured submarine power cable secured to a platform supportwith a length ofthe cable depending therefrom; and Figure 5is a part-sectional side view of another armoured submarine cable.

Referring first to Figure 1, there is shown a section of an armoured cable adjacent one end thereof (not shown). The armouring of the cable illustrated comprises a single layerofarmourwires 1. Asupport collar 2, formed for example of steel, is spaced from the end of the cable and secured to the armouring on each side ofthe collar 2. The collar has a radial shoul der 3 arranged to be downwardly facing when the cable adjacent the collar is disposed vertically, as shown, orsubstantiallyvertically, with the end ofthe cable closest to the collaruppermostto enable a depending length of cable adjacentthecollarto be supported thereby on a fixed support engaged bythe shoulder.In orderto enable the cable to be more positively supported by the collar, the collar in the arrangement shown in Figure 1 has a radially outwardly opening annular groove 4 defined between the radial shoulder 3 and a radial shoulder 5 opposite thereto and having a base 6. By locating cooperating flanges of a support structure in the groove 4the collarcan be clamped in fixed relationshiptothe support structure, or at least more positively located relative thereto, as will be more apparent hereinafter when the same feature is described in connection with the cableshown in Figure 4.

Aswill be clearer from Figures 2 and 3,the collar2 of the cable shown in Figure 1 is split lengthwise to enable itto befitted aboutthecable. As shown the collar 2 is obliquely axially split into a plurality of seg ments 7 with a small gap between adjacentsegments, six such segments being used in this particularambodiment. The direction and angle ofthe splits in the collar corresponds to that ofthe lay ofthe armour wires 1 to facilitate bending of the section of the cable which includes the collar.

Tofitthecollar2,an annularsection ofthearmour- ing is removed from the cable atthe location ofthe collar and the thus formed free ends 8,9 of the armouring are secured to opposed end portions 10,11 of the collar. As will be appreciated the collar provides mechanical protection forthe cable in place ofthe removed section of armouring and also provides a tensile connection between the armouring on each side ofthe collar. In the illustrated arrangement, the ends 8, 9 of the armouring are disposed overthe end portions 10,11 ofthe collar and fixed to the collar by welds 12,13 which secure the ends of the individual armourwires to the collar.The end portions 10,11 havetapersontheirexternal surfaces such that the outercontourofthe cable is devoid of abrupt changes at their locations. In the fitting ofthe collar, a layerofserving 14, providedoverthearmouringwill have been removed over a length greaterthan the length ofthe collar. After welding ofthe amourwires to the collar has been completed, fresh serving 15 is applied to the armouring and secured by taping 16.

Referring now to Figure 4, an end section ofanother submarine power cable is illustrated with a depending length 20 thereof being supported by a fixed support structure 21 on an off-shore plateform 22 which includes split flanges 23 which are received in an annular groove 24 of a support col lar 25 of the cable.

The collar 25 and the manner in which it is incorporated in the cable shown in Figure 4 are generally similartothe collar2 and the manner in which itis incorporated in the cable shown in Figure 1 as will be apparent from acomparison of these Figures. How ever, it will be noted thatthe armouring of the cable shown in Figure 4 comprises two layers 26,27Of armourwiresandthatthefreeendsoftheselayers are welded in staggered relationship to the respective end portions 28,29 ofthe collar afterannularsections of the layers 26,27 have been removed from the cable atthe location of the collar.

Additionally, itwill be noted thatthe collar25 is split into two longitudinal parts 30,31. Part 30 is formed with a socket end portion 32 into which a spigot end portion 33 of part 31 fits and the socket and spigot end portions are interconnected by fastening means, shown as radially disposed dowels 34, which areadaptedtoshearwhenthecollarissubjec- ted to a predetermined tensile load for example in the range of 10to 15tones. This feature prevents excessive loads being transferred to the platform should the submarine cable be hooked by an anchor or trawl.

It will also be noted thatthe end ofthe cable is fitted with a pulling eye which enable the cable to be pulled from the sea bed through a caisson (the top of which is illustrated at 35 in Figure 4) and by which the cable can be supportedwhilstthesplitflanges 23 of the support structure 21 on the platform 22 are being located in the groove 24 of the collar 25 in orderto support the depending length 20 of the cable.

The provision ofthe collar2,25 in the illustrated cables does not substantially increase the outer dia- meterofthe cables at their locations northeflexibility thereat and accordingly will not greatly hamperinstallation of the cable. Thus, for example, the cable with the collar already fitted can be readily pulled through the caisson 35. A sleeve may be provided overthe collar and cable adjacent thereto to pro vide an even smoother outer contourforthe cable at the location ofthe collar if desired.

It will therefore be appreciatedthatthe collar can be incorporated in the cable in thefactory, or in any eventpriorto installation off-shore. in orderto re ducethenumberofoperationsrequiredonthecable off-shore.

The armoured cable shown in Figure 5 has an an nular section of its armouring removed and the thus formed free ends of the armouring are secured to opposed end portions 36,37 of a collar 38. The collar38 likethe collar 25 is split into two longitudinal parts 39,40 which are interconnected by fastening means adapted to shear when the collar is subjected to a predetermined tensile load.As with collar 25, the parts 39,40 of collar 38 have cooperating socket and spigot end portions 41,42 which fit together and the fastening means interconnectthese portions and comprise radially disposed dowels 43. Itwill also be noted that the armouring of the cable shown in Figure 5 comprises two layers 44,45 of armour wires like the cable of Figure 4andthatwith the exception of the omission of the annular groove 24 present in collar25 the collar38 and the manner in which itis secured to the armouring is the same as that ofthe collar 25. One or more rubber or elastomeric sleeves 46 which may be heatshrinksleeves, may be provided overthe collar and adjacent cable.

The collar38 does notfunctionto enable a depend- ing length of cable to be supported, but instead can be incorporated anywhere in the cable where it is desired to prevent excessive tensile loads being transmitted by the armouring. Of course, the collar 38 may be incorporated in a cable which is also provided with a collar 25 and accordingly the cable sections shown in Figures 4 and 5 may be sections ofthe same cable.

In connection with the arrangements shown in Figures 4 and 5, it is to be understood thatforthe purposes of installation when the cables are likelyto experience greatertensile loads than can be withstood bythe dowels 34 and 43,dowels, orotherfastening means, of greater shear strength may be used to interconnectthe collar parts.

Claims (13)

1. An armoured cable having spaced from one end thereof a support collarwhich is secured to the armouring ofthe cable on each side of the collar, said collar having a radial shoulder arranged to be down wardlyfacing when the cable adjacentthe collar is disposed substantially vertically with said one end uppermostto enable a depending length of the cable adjacent the collarto be supported thereby.

2. A cable as claimed in claim 1, wherein said collar has a radially outwardly opening annular groove defined between said shoulder and radial shoulder opposite thereto.

3. A cable as claimed in claim 1 or 2, wherein an annular section of said armouring is removed from said cable at the location ofthe collarandthethus formed free ends ofthe armouring are secured to opposed end portions ofthe collar.

4. Acable as claimed in claim 3,wherein said thus formed free ends ofthe armouring are disposed over the end portions ofthe collar.

5. Acableas claimed in anyone of the preceding claims, wherein said collar is split lengthwise.

6. A cable as claimed in claim 5, wherein the collar is obliquely axially split into a plurality of segments.

7. A cable as claimed in claim 6, wherein the collar is split into six segments.

8. A cable as claimed in any one of the preceding claims, wherein the collar is split into two longitudinal parts which are interconnected by fastening means adaptedto shearwhen the collar is subjected to a predetermined tensile load.

9. An armoured cable wherein an annularsection ofthe armouring thereof is removed from the cable and the thus formed free ends of the armouring are secured to opposed ends of a collar, said collar being split into two longitudinal parts which parts are interconnected by fastening means adapted to shear when the collar is subjected to a predetermined tensile load.

10. A cable as claimed in any one of the preceding claims, wherein the cable comprises one or more electric conductors.

11. A cable as claimed in anyone of claims 1 to 9, wherein said cable comprises telecommunication el ements.

12. A cable as claimed in any one of claims 1 to 9, wherein said cable comprises one or more hydraulic conduits.

13. An armoured cable substantially as herein described with reference to Figures 1 to 3,4 or 5 of the accompanying drawings.