WO1998057844A1

WO1998057844A1 - Arrangements in buoys, particularly buoys for cable anchor chains

Info

Publication number: WO1998057844A1
Application number: PCT/NO1998/000147
Authority: WO
Inventors: Steinar HØVRING; Odd HØVRING
Original assignee: Hoevring Steinar; Hoevring Odd
Priority date: 1997-06-16
Filing date: 1998-05-13
Publication date: 1998-12-23
Also published as: NO972785L; AU7791998A; NO972785D0

Abstract

A buoy (10) is connected to an anchor-provided anchor chain (18) of the type which, in an appropriate number, uppermost are attached to a pipelay vessel (whereby the buoys (10), are taking an inoperative position). The propulsion of the pipelay vessel is based on the fact that it pulls itself forwardly along anchor chains (18), and respective anchor chains (18) are released from the pipelay vessel as they (as a consequence of a certain advance part distance has been completed) no longer extend forwardly in said intentional direction of advance. Upon the release of each single cable anchor chain (18), the buoy (10) thereof becomes operative. A supply boat serves to haul up released anchor chains (18) with anchors via the buoys (10), in order to, thereafter, move them such that they once more attain a forwardly directed course in said intentional direction of advance for the pipelay vessel, and again are attached to the pipelay vessel which, at all times, pulls itself forwardly along the anchor chains (18) which, from their attachment places on board the pipelay vessel extend forwardly in the intentional general direction of advance thereof and where the respective buoy (10), for recovery purpose is assigned an elongated, rope-like additional element (16; 16, 16'), e.g. comprising a piece of wire, directly/indirectly connected to the buoy (10). In order to favour the recovery possibility of the additional element (16), it exhibits at least one float body (26) which makes it at least partly floating and easier to get hold of.

Description

ARRANGEMENTS IN BUOYS, PARTICULARLY BUOYS FOR CABLE ANCHOR CHAINS.

This invention relates to an arrangement in a buoy, particularly for an anchor chain, in which an elongated rope-like element, e.g. in the form of a piece of wire, is attached to the buoy for recovery purpose.

So-called pipelay vessels are used e.g. when laying oil/gas pipelines on the seabed.

Such pipelay vessels are temporarily anchored to the seabed by means of anchors from which anchor chains/wires extend up to the vessel. These anchor lines extend forwardly from the vessel in the intentional moving direction from in front of the forecastle and slopingly forwards from the sides of the vessel. The anchors are laid by means of a supply boat, the pipelay vessel pulling itself forwards by means of the anchor lines.

As soon as an anchor line provided with an anchor is uncapa- ble of being utilised any more for the advance of the pipelay vessel, because this anchor line no longer is pointing forwardly in the intentional direction of advance of the pipelay vessel, but e.g. straight down towards the seabed, it is the task of the supply boat to draw up the anchor with the line by means of a winch and, thereafter, to lay the anchor with the line out again in front of the pipelay vessel.

In this way, such anchor lines are in a position to provide the enormous forces for advancing required for laying oil and gas pipelines on the seabed.

Thus, when a buoy with its anchor chain is to be displaced for anchoring on another place on the seabed in front of the last anchoring place, as seen in the pipelay vessel's direction of advance, it is the task of the supply boat first to get hold of the buoy and, through the buoy, to winch the anchor chain with the anchor on board the supply boat.

Thus, from the view of the supply boat, one is referred to hook on with a boathook the elongated, rope-like element, wire or the like attached to the buoy and which is difficult to get hold of, i.a. because this piece of wire extends straight down into the sea. One has to manoeuvre the supply boat quite up to the buoy, in order to get hold of the piece of wire, as well as hauling the supply boat forwards towards the free end of the piece of wire. This recovery operation is exceedingly difficult to carry out during weather conditions including seaway and poor visibility.

Consequently, the object of the present invention has been to facilitate recovery of said buoy and, thus, anchor chain with anchor, said buoy being of the kind defined introductorily .

. Said object is realised by means of a buoy whose elongated rope-like element attached thereto being shaped and designed in accordance with the definitions appearing from the characterizing clause of claim 1.

Said elongated rope-like element, e.g. in the form of a piece of wire, attached to the buoy through one end ring thereof or in any other suitable way, is, according to the present invention, provided with float means in the form of at least one float.

Thus, at least one portion of the rope-like element is kept floating in the sea surface layer. This facilitates to a considerable extent the possibilities of getting hold of the rope-like element by means of a boathook, without having to manoeuvre the supply boat to the immediate proximity of the buoy; this representing a dangerous situation for the crew on board the supply boat in rough sea and high seaway, where the buoy may strike against the crew.

In its simplest, most general embodiment, the elongated ropelike element may be provided with one float giving rise to a large buoyant force and positioned e.g. adjacent the outer end of the element.

However, it is easier and quicker to grasp or grip the ropelike element satisfactorily when the same is provided with at least two spaced float bodies attached thereto representing marked extensions/thickenings on the built up rope-like ele- ment, as well as provided with at least one e.g. sleeve- shaped distancer representing a marked throat portion of the rope-like element. Then, such a rope-like element's outer portion will position itself at a certain distance from the buoy.

The elongated, rope-like element of the buoy may exhibit floats along its entire length or along a substantial portion thereof .

Such a built up additional element will of course have a certain stiffness and will be floating in its entire length. If the additional element for the buoy is built up on a ropelike element having thickening individual parts and intermediate narrowing individual parts threaded thereon, the thickening parts individual may be typical buoyance bodies in the form of cork, the intermediate distancers narrowing the cross-section of the additional element, possibly may be made from plastics or similar, preferably flexible material.

In all embodiments of the invention, a ring or a loop (eye) may advantageously be disposed preferably at the end of the additional element. This loop may be attached thereon, or it may be made through splicing at the end of an additional element in the form of a piece of wire. Then, it is possible first to hoist the additional element on board the supply boat, and to place there the hook of the heaving line so that it engages directly into said loop which gives optimal engagement possibilities for safe and secure connection during the subsequent hoisting of the buoy up on deck.

A non-restricting exemplary embodiment of a buoy having a rope-like additional element assigned thereto is diagrammati- cally shown in the drawing, in which the sole figure illustrates a buoy assigned a rope-like additional element taking a position of use, in which the buoy floats halfway immersed in the surface layer of the sea, while the rope-like additional element assigned thereto adapted to facilitate the recovery of the buoy, floats in said sea surface layer.

Reference- is made to the figure of the drawing where an approximately ellipsoidal buoy 10 is in the form of a hollow piece having an annular fastener 12 and 14 at each of its two ends.

The upper end ring 12 of the buoy 10 is connected to a connecting portion (wire) 16' included in an elongated, ropelike additional element to the buoy 10, generally denoted at 16, said additional element, both in its known version and in its shape and design according to the invention, is adapted to facilitate the recovery of the buoy and, thus, the recovery of the anchor chain 18 connected to the buoy 10.

A disc-shaped, first float 20 is coupled to the additional element 16 which has the form of a wire piece extending to an end loop 24 which may be spliced of the twined wire strands of the end portion.

The additional element 16 has been made floating and allotted an irregular course in the longitudinal direction, in order to facilitate that a hook at the end of a casting line or a boathook finds hold for buoy recovery purposes.

According to the embodiment shown, this has been achieved in that, outside said piece of wire 16', cross-section- increasing float bodies 26 and intermediate cross-section- reducing distancers 28, have been threaded thereon (and/or attached thereto) , as referred to the finished, built up additional element for the buoy 10.

The distancers 28 will also represent a cross-sectional increase in proportion of the original wire. A floating addi- tional element 16 is easier to get hold of with one of the tools mentioned; the same goes for such an element having a larger thickness than the original wire, and the same manifest itself for an additional element with alternating narrow and broad portions distributed in the longitudinal direction.

Claims

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1. Arrangement in buoy (10) , especially for an anchor- provided anchor chain (18) of the kind which, in a suitable number, uppermost are attached to a pipelay vessel pulling itself forwardly along these during pipeline laying operations, and wherein respective anchor chains (18) are released from the pipelay vessel as they (as a consequence of having carried out a certain propulsion/advance extent) no longer extend forwardly in said intentional advance direction, so that the respective buoy (10) becomes operative upon the release of said anchor chain (18) , no longer usable, a supply boat serving to haul up released anchor chains (18) with anchors through the buoys (10) , in order to, thereafter, displacing them such that they again extend forwardly in said intentional advance direction for the pipelay vessel and to again attach them to the pipelay vessel which, at all times, pulls itself forwardly, utilising those anchor chains (18) which, from their fastening place on board the pipelay vessel extend forwardly in the intentional general advancing direc- tion thereof, and wherein the respective buoy (10) for recovery purpose is assigned an elongated, rope-like additional element (16; 16,16) directly/indirectly connected to the buoy, and e.g. in the form of a line exhibiting at least one float body, c h a r a c t e r i z e d i n that the line is a steel wire rope (16; 16,16') possessing the necessary rigidity of not twining itself around the buoy (10) , and onto which have been threaded a plurality of successive floats (26) , possibly with intermediate, sleeve-shaped spacer pieces (28) threaded thereon, said parts (26, 28) threaded thereon favouring the stiffness and rigidity properties of the steel wire rope (16; 16,16'), protecting it from damages due to external forces acting during the recovery operations, but without influencing the flexibility of the steel wire rope, so that this with floats (26) and intermediate sleeve-shaped spacer pieces (28) threaded thereon, can be coiled up on a winch.

2. Arrangement as set forth in claim 1, c h a r a c t e r i z e d i n that the additional element (16,16') has a portion (16') without any float, with which it is directly connected to the buoy (10) , while the remaining portion of the additional element (16) is provided with floats (26; 26, 28) along its full longitudinal extent or along substantially the full extent thereof.

3. Arrangement as set forth in claim 2, c h a r a c t e r i z e d i n that said remaining portion of the addi- tional element (16) has an irregular course in the longitudinal direction, exhibiting cross-sectional thickenings (26) and intermediate cross- sectional narrowings (28) and wherein, at least the thickenings (26) , have a smaller density than sea water and secure that at least one part of the additional element (16) holds itself floating in sea water.

4. Arrangement as set forth in claim 3 , c h a r a c t e r i z e d i n that said narrowings (28) are constituted by the sleeve-shaped spacer pieces which may consist of a material having a density corresponding to the density of the sea water or insignificantly exceeding that value, the additional element (16) as a whole constituting a buoyancy body securing that at least one portion is kept floating in sea water.

5. Arrangement as set forth in claim 2, c h a r a c - t e r i z e d i n that a large annular or disc-shaped float body (20) has been mounted in between the additional element's portion (16') without any floats and the portion thereof provided with floats.