GB2540780A

GB2540780A - Restricting the bending of an underwater cable

Info

Publication number: GB2540780A
Application number: GB1513192.3A
Authority: GB
Inventors: John Blackburn Darren; Conlon Gordon
Original assignee: Super Grip (uk) Ltd
Current assignee: Super Grip (uk) Ltd
Priority date: 2015-07-25
Filing date: 2015-07-25
Publication date: 2017-02-01
Anticipated expiration: 2035-07-25
Also published as: GB2540780B; GB201513192D0

Abstract

A bend restrictor for underwater cables or pipes consists of a series of links or shells, each shell consisting of two half-shells 301 and 302. The half-shells have mutually engaging surfaces and are held together by two axial pins placed on diametrically opposite sides of the half shells (only pin 508 is shown). The mutually engaging surfaces have interdigitating castellations (only castellations 501, 502, 503, 505, 506 on one side of the shell are shown). The shell is opened by removing one pin and positioning cable 502 within an axial void defined by the open shell. The shell is then closed and the pin manually inserted and secured. Each shell has a knuckle portion 509 which has an outer surface 510. Assembling the restrictor requires engaging the outer surface of the knuckle with an overlapping inner surface of a neighbouring shell (not shown). The shells can be moulded from structural polyurethane.

Description

Restricting the Bending of an Underwater Cable

CROSS REFERENCE TO RELATED APPLICATIONS

This application represents the first application for a patent directed towards the invention and the subject matter.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to restricting the bending of an underwater cable. 2. Description of the Related Art

Vertebrae bend restrictors (referred to herein as bend restrictors) are known in the oil and gas industry and are designed to prevent damage of an umbilical cable due to over bending.

It is known to manufacture bend restrictors from a plurality of interlocking elements that are moulded in the form of half shells, so as to allow the bend restrictor to be fitted on land, on board a vessel as a cable is being deployed or under water after deployment.

It is known for two half shells to be bolted together to form a whole element around a cable and when further elements are bolted into place in this way, each interlocks with the previous one already in place. This configuration allows the elements to move by a small angular displacement, such that the construction as a whole will lock up at a predetermined minimum bend radius when a bending moment is applied.

BRIEF SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided apparatus for restricting the bending of an underwater cable, comprising a plurality of interlocking elements each formed from a first half-shell circumferentially displaced from a second half shell, wherein, for each said element: a first half shell is secured to a second half shell by a first axial pin; and said first half shell is also secured to said second half shell by a second securing means circumferentially displaced from said first axial pin.

In a preferred embodiment, the second securing means includes a second axial pin circumferentially displaced from the first axial pin.

According to a second aspect of the present invention, there is provided a half shell configured to interlock with a second half shell to form an element, said element being configured to interlock with a similar element and so on to form a bend restrictor, comprising: first castellations extending from a first radial surface, for interdigitating with similar from an interlocking element; and second castellations extending from a second radial surface, for interdigitating with similar from said interlocking element.

In a preferred embodiment, the first castellations include a first hole for receiving a first pin. Preferably, the second castellations include a second hole for receiving a second pin.

According to a third aspect of the present invention, there is provided a method of applying a bend restricting assembly to a cable, comprising the steps of: receiving an element having a first half shell circumferentially displaced from a second half shell, wherein said first half shell is hinged with respect to said second half shell by a first radially displaced axial pin; opening said element by opening said first half shell with respect to said second half shell; positioning a cable within an axial void defined by the open element; closing the element to encase said cable, thereby bringing a third radial face of the first half shell into contact with a fourth radial face of the second half shell; and securing the first half shell to the second half shell.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a half-shell, configured to interlock with a similar second half-shell to form an element;

Figure 2 shows the half-shell of Figure 1 in cross section;

Figure 3 shows two half-shells in combination to form an element;

Figure 4 shows the opening of an element to initiate deployment;

Figure 5 shows an element encased around a cable;

Figure 6 shows the encasing of a second element around the cable of Figure 5;

Figure 7 shows the locking of the second element; and

Figure 8 shows the deployment of an assembly. DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS Figure 1 A half shell 101 is shown in Figure 1, configured to interlock with a similar second half shell to form an element (as shown in Figure 3). The element is configured to interlock with a similar element and so on to form a bend restrictor (as shown in Figure 9).

First castellations 102,103,104 extend form a first radial surface 105 for interdigitation with similar from an interlocking element. Second castellations 106, 107 extend from a second radial surface 108 for interdigitation with similar from the interlocking element.

The first castellations 102, 103 and 104 include a respective first hole 109, 110, 111 for receiving a first pin 112. The first pin 112 includes a threaded end 113. Hole 109 is also threaded (tapped) such that after insertion through hole 111 and hole 110, the pin 112 is secured within hole 109.

The second castellations 106, 107 also include a respective second hole 114,115 for receiving a second pin. In this embodiment, the second pin is secured by a tapped hole present within the cooperating half shell; the second pin being secured after deployment of the bend restrictor around one or more cables.

In an embodiment, the elements are moulded from structural polyurethane and as such do not require additional corrosion protection. Pins (such as pin 112) may be machined from super-duplex grade stainless steel, providing advantageous properties by the inclusion of both austenitic and ferritic structures.

Figure 2

Half shell 101 is shown in cross section in Figure 2. The half shell defines a central axis 201 surrounded by an axial void 202 which, when deployed, receives one or more umbilical cables.

When constructing a bend restricting assembly, a knuckle 203, defined by shells of a first element, is surrounded by a knuckle-void 204 of a cooperating element.

When the cooperating element has been closed, the knuckle is held securely but with a substantial tolerance, such that a degree of movement is possible. This degree of movement is specified to allow a predetermined degree of bending for the assembly as a whole.

As illustrated in Figure 2, the half shells are held together by the first pin 112 and the second pin 205. These are deployed in an axial orientation, parallel to the central axis 201.

Figure 3

The apparatus for restricting the bending of an underwater cable comprises a plurality of interlocking elements of the type illustrated in Figure 3. Each element is formed from a first half shell 301 and a second half shell 302. The first half shell 301 is secured to the second half shell 302 by an axial pin 303. In this way, it is possible for the first half shell 301 to hinge with respect to the second half shell 302 about the pin 303. Thus, this combination of two half shells secured by a single pin may represent a sub-assembly, suitable for transportation purposes.

When deployed, the first half shell 301 is also secured to the second half shell by a second securing means, not shown in Figure 3, circumferentially displaced, that is to say, displaced in the circumferential direction illustrated by arrow 304, from the first axial pin 303.

Figure 4

In many applications, the bend restricting assembly will be applied to the cable prior to the cable being deployed at sea. As illustrated in Figure 4, an operative receives an element having a first half shell 301 that is circumferentially displaced from a second half shell 302. The first half shell 301 is hinged with respect to the second half shell 302 by a radially displaced axial pin 303. The operative opens the element by opening the first half shell 301 with respect to the second half shell 302, about the pin 303.

After opening the element, a cable is positioned within the axial void 202 defined by the open element. The open element is then closed to encase the cable, thereby bringing a third radial face 401 of the first half shell 301 into contact with a fourth radial face 402 of the second half shell 302. The first half shell 301 is then secured to the second half shell 302.

Figure 5

As shown in Figure 5, an assembly 501 has been encased around a cable 502 by bringing the first half shell 301 into contact with the second half shell 302.

The first pin 303 was located in first holes formed in first castellations extending from a first radial surface of the first half shell, engaging with second holes formed in second castellations extending from a second radial surface of the second half shell. A threaded end portion of the first pin has engaged within a tapped portion of one of the half shells. Elements may be stored and transported in this configuration.

To enclose the element, each first half shell 301 includes third castellations 501, 502, 503 that extend circumferentially from a third radial surface 504, circumferentially displaced from the first radial surface. Each second half shell 302 includes fourth castellations 505, 506 that extend from a fourth radial surface 507 that opposes the third radial surface 504.

To close the assembly, the third castellations 501, 502, 503 are arranged to interdigitate with the fourth castellations 505, 506. Second holes in the third castellations align with second holes in the fourth castellations and a second pin 508 engages through these second holes. Again, castellation 501 may include a tapped hole for restraining a threaded portion of the second pin. Thus, in order to position an assembly 501 around a cable 502, it is only necessary to engage a single additional pin 508.

In this embodiment, each element includes a knuckle portion 509 having an outer engaging surface 510. Each element includes an overlapping portion defining an inner engaging surface, such that the closing step includes enclosing an adjacent knuckle portion within an overlapping portion, thereby constructing the assembly.

Figure 6

As shown in Figure 6, a first element 601 has been engaged around a cable 602. The first element 601 defines a knuckle portion 603 having an outer engaging surface. The first element 601 includes an overlapping portion 604 that defines an inner engaging surface 605.

In Figure 6, a second element 606 (in an open configuration) has been placed around the cable 602. This also has an overlapping portion 607 that has been arranged to enclose knuckle portion 603, thereby starting the construction of an assembly from these first two elements.

Figure 7

After positioning the second element 606 as shown in Figure 6, the element is closed about its first pin (similar to pin 303) such that overlapping portions 607 encloses knuckle portion 603. The second pin (substantially similar to pin 303) is then manually inserted and secured using an appropriate tool. Furthermore, having attached element 606, a further knuckle portion 701 is presented to facilitate the attachment of the next assembly.

Thus, in this way, an assembly can be constructed to any desired length prior to the deployment of a cable or after a cable has been deployed. For each element, in an embodiment, the operative is only required to secure a single pin, thereby significantly reducing material costs and significantly reducing the time involved for constructing the assembly. Furthermore, assembly time is reduced significantly when the apparatus is being deployed in challenging environments, such as when a vessel is at sea or when the bend restrictor is being retro-fitted to an existing underwater cable.

Figure 8

In many deployments, it is possible for an assembly to be constructed on shore, as illustrated in Figure 8. A cable 801 has been surrounded by an assembly 802 of a plurality of interlocking elements. A portion of the assembly shown in Figure 8 is resting on the ground, while the opposite end is being maneuvered by lifting apparatus. This results in a bending moment being applied to the assembly. However, as shown in Figure 8, the degree of bending permitted is restricted and it is not possible for any bend to exhibit a radius of curvature less than a predetermined minimum radius 803. A tail end of the assembly is fitted with a tapered adaptor to prevent snagging. The adaptor provides a smooth transition from the outside diameter down to the cable.

Claims

Claims What we claim is:

1. Apparatus for restricting the bending of an underwater cable, comprising a plurality of interlocking elements each formed from a first halfshell circumferentially displaced from a second half-shell, wherein for each said element: a first half-shell is secured to a second half-shell by a first axial pin; and said first half-shell is also secured to said second half-shell by a second securing means circumferentially displaced from said first axial pin.

2. The apparatus of claim 1, wherein said second securing means includes a second axial pin circumferentially displaced from said first axial pin,

3. The apparatus of claim 1, wherein said interlocking elements are fabricated from moulded polyurethane and said first axial pin and said second axial pin are fabricated from super duplex stainless steel.

4. The apparatus of any of claims 1 to 3, wherein: each first half-shell includes first castellations that extend circumferentially from a first radial surface; each second half-shell includes second castellations that extend circumferentially from a second radial surface that opposes said first radial surface; said first castellations interdigitate with said second castellations; first holes in said first castellations align with first holes in said second castellations; and said first pin engages through said first holes.

5. The apparatus of claim 4, including a tapped hole for restraining a threaded portion of said first pin.

6. The apparatus of claim 4, wherein: each said first half-shell includes third castellations that extend circumferentially from a third radial surface, circumferentially displaced from said first radial surface; each said second half-shell includes fourth castellations that extend from a fourth radial surface that opposes said third radial surface; said third castellations interdigitate with said fourth castellations; second holes in said third castellations align with second holes in said fourth castellations; and said second pin engages through said second holes.

7. The apparatus of claim 6, including a tapped hole for restraining a threaded portion of said second pin.

8. A half-shell configured to interlock with a second half-shell to form an element, said element being configured to interlock with a similar element and so on to form a bend restrictor; comprising first castellations extending from a first radial surface, for interdigitation with similar from an interlocking element; and second castellations extending from a second radial surface, for interdigitation with similar from said interlocking element.

9. The half-shell of claim 8, wherein said first castellations include a first hole for receiving a first pin.

10. The half-shell of claim 8 or claim 9, wherein said second castellations include a second hole for receiving a second pin.

11. A method of applying a bend restricting assembly to a cable, comprising the steps of: receiving an element having a first half-shell circumferentially displaced from a second half-shell, wherein said first half-shell is hinged with respect to said second half shell by a first radially displaced axial pin; opening said element by opening said first half-shell with respect to said second half-shell; positioning said cable within an axial void defined by the open element; closing the element to encase said cable, thereby bringing a third radial face of the first half-shell into contact with a fourth radial face of the second half shell; and securing the first half-shell to the second half-shell.

12. The method of claim 11, wherein said axial pin is supported by: first holes formed in first castellations extending from a first radial surface of said first half-shell; and second holes formed in second castellations extending from a second radial surface of said second half shell.

13. The method of claim 12, wherein a threaded end portion of the first pin is engaged within a tapped portion of one of said half-shells.

14. The method of any of claims 11 to 13, wherein: each element includes a knuckle portion having an outer engaging surface; each element includes an overlapping portion defining an inner engaging surface; and said closing step includes enclosing an adjacent knuckle portion within an overlapping portion, thereby constructing said assembly.

15. The method of claim 14, wherein said step of constructing the assembly is performed on shore, prior to installation of a cable.

16. The method of claim 14, wherein said step of constructing said assembly is performed on a vessel prior to cable deployment.

17. The method of claim 14, wherein said step of constructing said assembly is performed under-water to an existing cable.

18. The method of any of claims 11 to 17, wherein the first halfshell is secured to the second half-shell by a second axial pin.

19. The method of claim 18, wherein said second axial pin is supported by: third holes formed in third castellations extending from a third radial surface of said first half-shell; and fourth holes formed in fourth castellations extending from a fourth radial surface of said second half-shell.

20. The method of claim 19, wherein a threaded end portion of the second axial pin is engaged within a tapped hole formed in one of said halfshells.

21. Apparatus for restricting the bending of an underwater cable, substantially as herein described, with reference to Figures 1, 2 and 3.

22. A method of applying a bend restricting assembly to a cable substantially as herein described, with reference to Figures 4 to 8.