GB2306608A

GB2306608A - Cable anchoring method and device

Info

Publication number: GB2306608A
Application number: GB9622661A
Authority: GB
Inventors: Jan Erik Karlsen; Knut Engli; Ove Svein Birkelund
Original assignee: Alcatel Kabel Norge AS
Current assignee: Alcatel Kabel Norge AS
Priority date: 1995-11-02
Filing date: 1996-10-31
Publication date: 1997-05-07
Anticipated expiration: 2016-10-31
Also published as: NO954377D0; GB2306608B; NO300748B1; FR2740850B1; GB9622661D0; NO954377L; FR2740850A1

Abstract

The method and device for dynamically and statically anchoring an elongated article (1) to a sea bed uses a wire (9) which is secured both to the sea bed and to anchoring means (7) arranged on the article. The anchoring means (7) is integrated with external longitudinal armour arranged around the core of the elongated article (1), by connecting with ends of the armour, squeezed by clamping cones, of adjacent parts of the article. The anchoring means (7) has as armour block (10) with a groove (11) supporting a ring (12) with a swivel (14) for the cable end. A second cable may have a swivel on the other side of the ring (12).

Description

CABLE ANCHORING METHOD AND DEVICE The present invention relates to installation of elongated articles from a surface vessel to a sea bed. It relates in particular to permanent installations and to the problem of preventing damage to an elongated article which is installed between a surface vessel and the sea bed. The elongated article may be a cable, an umbilical or the like comprising a core and outer protective layers including at least one layer of armour elements.

US 3,216,203 relates to an arrangement for submarine conveyance of fluids through a flexible pipe line. The pipe line is assumed to have a positive buoyancy and it may be maintained at a desired depth by anchoring the pipe line with several pairs of cables to sea bed structures. This publication does, however, not give any hints to how the cables could be attached to the pipe in order to prevent damages to the pipe.

The elongated article will normally follow an S-curve between a substantially vertical outlet from a vessel and a substantially horizontal installation on the sea bed. At a certain position between the vessel and the sea bed, the elongated article is suspended from buoyancy devices and at a lower position the elongated article is anchored to the sea bed. There is little risk of damaging the elongated article at the buoyancy device suspending position, but at the anchoring position there are forces acting on the elongated article in all directions and these forces are difficult to cope with.

The object of the invention is to provide means for anchoring an elongated article in a position mentioned - over a long time - without damaging the article. The main features of the invention are defined in the claims.

With the present invention we have obtained a reliable method and means for anchoring a cable or the like to a sea bed.

Above mentioned and other features and objects of the present invention will clearly appear from the following detailed description of embodiments of the invention taken in conjunction with the drawings, where Figure 1 illustrates an installation of an elongated article, Figure 2 illustrates the main principles of the invention, and Figure 3 illustrates details of an anchoring device.

In Figure 1 an armoured elongated article 1 is installed to follow an S-curve between a surface vessel (not shown) and a sea bed 2. The article 1 - hanging vertically from the vessel - is suspended at 3 by a buoyancy device 4. The most critical part of the article 1 is where it is anchored to the sea bed 2 by means of a wire 5 passing from a clump weight 6 to an anchoring device 7 arranged on the article 1.

Due to movements of the surface vessel and due to waves and sea currents the anchoring device will move, twist and turn in all directions all the time. The anchoring device must be capable of taking up all forces acting on the article 1 without damaging the article in any way. This is obtained by securing the device 7 to the armour 8 of the article and by allowing the anchoring device to move relatively freely in relation to the article. For more stability we may use a second anchoring wire 9, as shown.

Figure 2 illustrates the principles of the anchoring device 7 of Figure 1. The anchoring device includes an armour block 10 to which armour elements (not shown) of the elongated article 1 is secured. Details are shown in Figure 3. The block 10 is provided with a groove 11 accommodating a rotatable ring 12 to which an anchoring wire 13 is secured by means of a swivel arrangement 14. The elongated article 1 is provided with conventional bending restrictors 15 and 16 on both sides of the armour block 10.

The ring 12 is free to rotate in its groove 11 within the armour block 10, and so is the swivel 14 relatively to the ring 12. An additional anchoring wire may be attached to the other side of the ring 12 as shown in Figure 3.

In Figure 3 one embodiment of an anchoring device 20 is shown great detail. An elongated article 1 is provided with at least 3 layers of armour elements 21, 22 and 23. Two of the layers 22 and 23 are cut and all the element ends are squeezed between two sets of clamping cones 24, 25 and 26 by tightening screws 27 within an armour block 28. The open spaces 29 of the armour block are filled with a water repellent material to prevent corrosion.

The armour block 28 is provided with a groove 30 to accommodate a rotatable ring 31. The ring is provided with a swivel arrangement 32 also having a groove accommodating a ring 33 to which an anchoring wire 34 is secured. There is also provided a handling eye 35. Bending restrictors 36 and 37 are indicated. An additional similarly arranged anchoring wire 38 is indicated on the other side of the armour block 28, for increased stability.

The above detailed description of embodiments of this invention must be taken as examples only and should not be considered as limitations on the scope of protection. The number of armour layers can for instance be varied. The swivel arrangement 32 could be made spherical instead of cylindrical as shown. The bending restrictors could be attached by other means to the armour block.

Claims

Patent Claims:

1. Method for dynamically and statically anchoring an elongated article (1) which is installed between a surface vessel and a sea bed (2), using wire means (5;13;34) which are secured both to the sea bed and to anchoring means (7,20) arranged on the article, c h a r a c t e r i z e d b y integrating the anchoring means (7,20) with external longitudinal armour (8;21-23) arranged around the core of the elongated article (1).

2. Method according to claim 1, c h a r a c t e r i z e d b y integrating the anchoring means (7,20) with the armour (8;21-23) by interrupting at least one layer of armour elements (22,23) and interconnecting the anchoring device between the wire ends.

3. Method according to claims 1 or 2, c h a r a c t e r i z e d b y interconnecting the armour (21-23) with an armour block (10,28), said block having a groove (11,30) accommodating a rotatable ring (12,31) to which an anchoring wire (8,13,34) is secured via a swivel arrangement (14;32).

4. Method according to claims 1,2 or 3, c h a r a c t e r i z e d b y arranging an additional anchoring wire (38) between the anchoring means and the sea bed.

5. Dynamic/static means for anchoring an elongated article (1) to a sea bed (2), including wire means (5;13;34) which is secured both to the sea bed and to anchoring means (7,20) arranged on the article, c h a r a c t e r i z e d i n t h a t the anchoring means is integrated with external longitudinal armour (8;21-23) elements arranged around the core of the elongated article.

6. Anchoring means according to claim 5, c h a r a c t e r i z e d i n t h a t the anchoring means (7,20) is interconnected between ends of at least one interrupted layer of armour elements (22,23).

7. Anchoring means according to claims 5 or 6, c h a r a c t e r i z e d i n t h a t the anchoring means (7,20) includes an armour block (10,28) which is secured to the armour elements (21-23), said block having a groove (11;30) accommodating a rotatable ring (12;31) to which the anchoring wire (8;13;34) is secured via a swivel arrangement (14;32).

8. Anchoring means according to claims 5, 6 or 7, characterized in that the anchoring means (7,20) includes means for attaching an additional anchoring wire (9,38) to the elongated article.

9. Method according to claim 1 substantially as hereinbefore described with reference to the drawings.

10. Anchoring means according to claim 5 substantially as hereinbefore described and shown in any of the drawings.