GB2207642A

GB2207642A - Buoyant support of flexible structures

Info

Publication number: GB2207642A
Application number: GB08813330A
Authority: GB
Inventors: Mark Lydon Board
Original assignee: SEAFLEX
Current assignee: SEAFLEX
Priority date: 1987-08-06
Filing date: 1988-06-06
Publication date: 1989-02-08
Anticipated expiration: 2008-06-06
Also published as: GB8813330D0; GB2207642B; GB8718581D0

Abstract

A method of first buoyantly supporting and subsequently laying a non-buoyant flexible cable 11 on the bed 13 of a river 15 comprises releasably coupling the cable 11 lengthwise to at least one inflatable tube 17 during haul out of the cable 11 along the path where it is to be laid, i.e. across the river 15. The cable 11 is suspended from the tube 17, position by successive position along the length thereof, from first and second storage stations 19 and 21 respectively from whence the cable 11 and tube 17 are respectively dispensed to position F on the oppsite bank of the river 15. The cable 11 may be caused to sink to rest on the river bed 13 by releasing inflation air from the tube 17, wherby the coupled cable 11 and tube 17 sink together to the bed 13. The coupling between the cable 11 and tube 17 may then be released and the tube 17 thereafter recovered. The invention is also applicable to the buoyant support and subsequent laying of flexible structure in the form of articulated rafts and coverings. <IMAGE>

Description

"Improvements in or relating to the Buoyant Support of Flexible Structures" BACKGROUND TO THE INVENTION This invention relates to buoyant support of flexible structures.

As used herein, the term "flexible structure" includes not only filamentary material such, for example, as cable or pipe, but also flexible mattresses, rafts and coverings, particularly those comprising a plurality of contiguous segments, interconnected in an articulated manner.

SZT#ARIES OF THE INVE2UION According to one aspect of the present invention, a method of buoyantly supporting a flexible structure comprises releasably coupling the structure to at least one buoyancy member of elongate form.

The buoyancy of the buoyancy member may be controllable. The buoyancy member preferably comprises an inflatable tube.

The method may comprise the steps of first causing the flexible structure to sink by reducing the buoyancy of the buoyancy member, so as to cause the coupled flexible structure and buoyancy member to sink together to the bed of an expanse of water and then releasing the coupling between the flexible structure and the buoyancy member.

The buoyancy member may comprise a plurality of closed chambers of elongate form, disposed end to end.

The buoyancy member may be provided with pouch means, extending longitudinally of the buoyancy member. The pouch means may be openable to receive flexible structure in the form of filamentary material. The seam portion may then be closed so as to encompass the said filamentary material and progressively couple the filamentary material to the buoyancy member.

According to another aspect of the invention, apparatus for laying underwater filamentary material according to any of the methods set forth above, comprises apparatus for controlling the buoyancy of the buoyancy member.

The apparatus may further comprise gas pump means for inflating the inflatable buoyancy member.

BRIEF DESCRIPTION OF THE DRATZ GS The foregoing and other features are hereinafter described, by waN of example only, and not of limitation, with reference to the accompanying drawings, wherein Figure 1 is a diagram illustrating a flexible cable in the course of being hauled across water using the method and apparatus of the invention, Figure 2 is a diagram illustrating the sinking of the filamentary material, Figures 3, 4, 5 and 6 illustrate details and modifications of the apparatus, Figure 7 is an end view of a buoyancy member clamping device, Figure 8 is a view taken on the lines VIII - VIII of Figure 7, Figure 9 is an end view of one alternative clamping device, Figure 10 is a view taken on the lines X - X of Figure 9, Figures 11 and 12 are, respectively, end and sectional side views of another clamping device, Figures 13 and 14 are side views in section which illustrate yet further clamping devices, and Figures 15 and 16 illustrate how the invention can be applied to the laying of underwater flexible structure in the form of pipe protecting covering, DETAILED DESCRIPTION OF THE PREFERRED ET~IBODII#E# With reference to Figures 1 and 2, a method of first buoyantly supporting and subsequently laying flexible structure comprising non-buoyant filamentary material in the form of a cable 11 is illustrated thereby.The flexible cable 11 is to be laid on the bed 13 of an expanse of water, which in this example is a river 15, and the method comprises releasably coupling the cable 11 lengthwise to a buoyancy member 17 of elongate form during haul out of the cable 11 along the path where it is to be laid, i.e. across the river 15.

The buoyancy of the member 17, which comprises an inflatable tube, is controllable.

The flexible cable 11 is susPended from the buoyancy member 17, position by successive position along the length thereof, from first and second storage stations 19 and 21 respectively from whence the cable 11 and member 17 are respectively dispensed to position F on the opposite bank of the river 15.

The cable 11 may be caused to sink to rest on the river bed 13 by reducing the buoyancy of the buoyancy member 17, whereby the coupled cable 11 and member 17 sink together to the bed 13, extending along the route B. The couplings between the cable 11 and buoyancy member 17 may then be released and the member 17 thereafter recovered.

In an alternative method of controlling the coupled cable 11 and buoyancy member 17, the cable 11 may be caused to sink to rest on the bed 13, along the route 3, by disconnecting the coupling between the cable and the buoyancy member while allowing the member 17 to float, thereby freeing the cable 11 from the floating member.

With reference to Figure 3, the buoyancy member 17 need not be in a single length. For versatility of application, a buoyancy member may comprise a plurality of sections l7a, 17b, 17c and so on, each in the form of a tubular chamber of elongate form and each, for example, of 25 metres in length. The sections 17a etc. may be preinflated and brought into use when desired. The sections 17a etc.

illustrated by Figure 3 are constructed so as to be releasably connected to each other.

As shown in Figure 1, the cable 11 and the buoyancy member 17 are preferably coupled together lengthwise progressively at a position 23 where the coupled components are hauled out into the river 15.

The cable 11 and the buoyancy member 17 may be coupled by a multiplicity of releasable tie devices 25 (Figure 4) disposed at intervals along the juxtaposed lengths of the two components as they progress past the position 23 and towards the adjacent point of entry into the river 15.

With reference to Figures 5 and 6, the tie devices 25 of Figure 4 may be replaced by an arrangement wherein the buoyancy member 17 is provided with a tubular pouch 41 extending substantially the length of the member 17.

The pouch 41 is provided with releasable closure means 39, comprising for example, slide fastener means, a "ZIP" (Registered Trade Mark) fastener, a bead and socket fastener, or a loop and hook fastener, e.g. Velcro (Registered Trade Mark) fastener means.

When the pouch 41 is in use, cable 11 dispensed from the station 19 is fed progressively to occupy the tubular pouch 41 which is formed by progressive closure operation of the pouch closure means 39.

The first and second storage stations 19, 21 comprise rotatable reels on which the cable 11 and the buoyancy member 17, respectively, are laid up, the latter in flattened, deflated form. The reels 19, 21 are rotatable about substantially horizontal (fixed) axes.

Gas, introduced into the buoyancy member 17 as it is hauled off its reel 21, causes the flat member 17 to inflate from the position of gas entry back to the reel 21. The gas, which may be air, is preferably introduced by gas pump means. (Not shown). Introduction of the inflation gas into the buoyancy member 17 provides the member with its own moving gas seal.

When in the course of performing the method, employing apparatus as hereinbefore described, the coupled cable 11 and buoyancy member 17 are in position buoyantly spanning the route A, across the river bed 13. Thereafter, the coupled components are caused to sink to the river bed.

Sinking may be achieved by first reducing buoyancy to the coupled components to commence the sinking operation. This is done by adding weight W to the components. The buoyancy of the buoyancy member 17 is then reduced by allowing air to escape from the member 17, using air release valve means fitted thereto, in order to control the sink rate.

To achieve a more rapid escape of buoyancy air from the buoyancy member 17, the latter may be provided with a "ZIP" (R.T.M.) fastener or the like, in order to provide an air escape opening of large cross-section, preferably at least equivalent to the crosssection of the member 17.

When the coupled components 11, 17 are at rest together on the river bed 13, they are separated either by releasing the tie devices 25 or by opening the tubular pouch 41, as the case may be. With the cable 11 freed from the buoyancy member 17, the member 17 may be recovered for restorage on its reel 21. Any residual gas contained in the member 17 is expelled in the course of such recovery.

Freeing of the cable 11 from the buoyancy member 17 may demand the intervention of a diver to release the tie devices 25 or undo the pouch 41 as the case may be.

As illustrated by Figure 6, in an alternative method, the pouch 41 can be progressively opened while the buoyancy member 17 floats on the water, allowing the cable 11 to sink onto the river bed 13. With this arrangement the buoyancy member 17 can be recovered from the water surface without recourse to the services of a diver. Indeed, using a slide fastener or the like closure means, the weight of cable 11 released from the buoyancy member 17, following opening of an end portion of such fastener, can be utilised to continue the fastener opening process. The cable 11, being thereby progressively released from the buoyancy member 17, sinks to the desired route 3, member 17 being recoverable by being hauled to the river bank (or dry access position) without the necessity for venturing on or into the water.

From a safety and security viewpoint, it is desirable to be able to isolate and/or repair any given section of the inflated buoyancy member. With reference to Figures 7 and 8, such action may be achieved by clamping two members 50 across the cut end of the buoyancy member 17, thereby pinching it in order to form a gas seal. The members 50 are held in place by releasable clamps 51.

Figures 9 and 10 show an alternative method of clamping, comprising the use of strongbacks 55 held together by pillars 56, and inflatable bags 57 disposed between the buoyancy member 17 and the strongbacks 55 so as to pinch the member 17.

Figures 11 and 12 show another alternative, using an end plate 60 disposed in a cut end of the buoyancy member 17 and clamped in place by a releasable band 61 encircling both the plate 60 and cut end of the member. The plate 60 carries a valve 62, which may be used to control the flow of air to the member 17 from an external source.

Figure 13 shows an arrangement wherein cut ends of the buoyancy member 17 are interconnected by a short length of flexible tube 65.

The ends of the tube 65 are secured to the cut ends of the buoyancy member 17 by inflatable structures 66 of annular form. The arrangement allows flow between the interconnected tube ends.

Figure 14 shows how one cut end of the buoyancy member 17 can be closed by an inflatable stopper 70, perforated by an air supply duct 71. A control valve 72 can be used to connect the duct 71 with an external air supply source.

Due to the fact that inflation of the buoyancy member 17 to its developed tubular state is carried out from the leading end of the member, only the required amount of tubular member will be inflated.

Should the buoyancy member be constructed in sections, as illustrated by Figure 3, the sections may be serially connected and/or separated, hydraulically. In the latter case they may be inflated before contact with the water by inflation hose means which would be disconnected from an inflated section 17a, say, or, alternate sections 17a, l7c, say, and then connected to the next section 17b or next pair of alternate sections 17b, 17d, as the case may be.

At least one of the reels of storage stations 19, 21 can be replaced by a storage chamber.

The storage station 21 may have associated therewith at least one roller pair through the nip(s) thereof the buoyancy member 17 passes in the course of being dispensed. At least one of the or each roller pair is preferably drivable. The nip(s) may be used to form one or more closed ends within the buoyancy member 17.

With reference to Figures 15 and 16, use of the invention is not limited to handling flexible structures of filamentary form.

Figure 15 is a view in perspective and from above, of a mattress-like flexible structure 80 comprising a plurality of contiguous segments 81 interconnected in an articulated manner whereby one segment 81 can move relative to another or the others.

The segments 81, which are hollow, are of hexagonal plan form and have tapered lower ends, and are interconnected by a rope network 82.

The segments 81 are filled with concrete.

Buoyancy is provided by a plurality of air-filled buoyancy members 17 releasably coupled to the flexible structure 80 by ties 25. The members 17 are disposed lengthwise on the structure 80, in substantially parallel array.

The flexible structure 80 is intended to be used as a protective covering of underwater pipes (or cables).

In use, as illustrated by Figure 16, the flexible structure 80 is floated, from, for example, a beach, above the position where a pipe 83 has been laid on the sea bed 84.

Buoyancy is then removed by releasing inflation air from the buoyancy members, using release valves 85, and the flexible structure 80 allowed to sink progressively to a position whereby it covers the pipe 83.

Subsequently, the members 17 are recovered, using divers, in the manner described above.

The flexible structure 80 is of the form marketed under the Trade Mark "LINKLOK" by Hydrofax Limited of Great Yarmouth, Norfolk, U.K.

It will be appreciated that, in the case of any of the abovedescribed examples, the method of sinking a flexible structure can be reversed, so as to float the same, by refilling member(s) 17 with inflation gas.

Claims

C L A I M S

1. A method of buoyantly supporting flexibl & structure comprising releasably coupling the structure to at least one buoyancy member of elongate form.

2. The method of Claim 1, wherein buoyancy of the buoyancy member is controllable.

3. The method of Claim 1 or 2, wherein the buoyancy member comprises an inflatable tube.

4. The method of Claim 2 or 3, comprising the steps of first causing the flexible structure to sink by reducing the buoyancy of the buoyancy member, so as to cause the coupled flexible structure and buoyancy member to sink together to the bed of the water expanse and then releasing the coupling between the flexible structure and the buoyancy member.

5. The method of any one of Claims 1 to 3, wherein the buoyancy member comprises a plurality of closed chambers of elongate form, disposed end to end.

6, The method of any one of Claims 1 to 5, wherein the flexible structure comprises filamentary material.

7. The method of Claim 6, wherein the buoyancy member is provided with openable pouch means, extending longitudinally of the buoyancy member.

8. The method of Claim 7, wherein the pouch means are openable to receive the filamentary material and are then closable so as to encompass the said filamentary material and progressively couple the filamentary material to the buoyancy member.

9. The method of any one of Claims 1 to 8, wherein the filamentary material and the buoyancy member are coupled by a plurality of releasable tie devices disposed at intervals along the juxtaposed lengths of the filamentary material and the buoyancy member.

10. The method of any one of Claims 6 to 9, wherein the filamentary material and the buoyancy member are respectively dispensed from first and second storage stations, at least one of said storage stations comprising a rotatable reel.

11. The method of any one of Claims 6 to 9, wherein the filamentary material and the buoyancy member are respectively dispensed from first and second storage stations, at least one of said storage stations comprising a storage chamber.

12. The method of Claim 10 or 11, wherein the storage station associated with the buoyancy member has associated therewith, at least one roller pair through the nip of which the buoyancy member passes in the course of being dispensed.

13. The method of Claim 12, wherein at least one of the roller pair is drivable.

14. The method of Claim 10 or 11, wherein the nip of the roller pair is used to form a closed end within the buoyancy member.

15. The method of any one of Claims 1 to 5, wherein the flexible structure comprises a plurality of contiguous segments, interconnected in an articulated manner.

16. Apparatus for buoyantly supporting flexible structure, according to the method claimed in any one of Claims 1 to 15, comprising apparatus for controlling the buoyancy of the buoyancy member.

17. Apparatus as claimed in Claim 16, wherein the buoyancy member is inflatable, the apparatus comprising gas pump means for inflating the buoyancy member.

18. A method of buoyantly supporting and subsequently laying underwater filamentary material, substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.

19. A method of buoyantly supporting and subsequently laying underwater filamentary material, substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings, modified substantially as hereinbefore described with reference to Figure 3 of said drawings.

20. A method of buoyantly supporting and subsequently laying underwater filamentary material, substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings, modified substantially as hereinbefore described with reference to Figure 4 of said drawings.

21. A method of buoyantly supporting and subsequently laying underwater filamentary material, substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings, modified substantially as hereinbefore described with reference to Figures 5 and 6 of said drawings.

22. A method of buoyantly supporting and subsequently laying underwater filamentary material, substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings, modified substantially as hereinbefore described with reference to Figures 7 and 8 of said drawings.

23. A method of buoyantly supporting and subsequently laying underwater filamentary material, substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings, modified substantially as hereinbefore described with reference to Figures 9 and 10 of said drawings.

24. A method of buoyantly supporting and subsequently laying underwater filamentary material, substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings, modified substantially as hereinbefore described with reference to Figures 11 and 12 of said drawings.

25. A method of buoyantly supporting and subsequently laying underwater filamentary material, substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings, modified substantially as hereinbefore described with reference to Figure 13 of said drawings.

26. A method of buoyantly supporting and subsequently laying underwater filamentary material, substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings, modified substantially as hereinbefore described with reference to Figure 14 of said drawings.

27. A method of buoyantly supporting and subsequently laying underwater flexible structure, substantially as hereinbefore described with reference to Figures 15 and 16 of the accompanying drawings.