IE46029B1

IE46029B1 - Apparatus for supporting pipelines

Info

Publication number: IE46029B1
Application number: IE11478A
Authority: IE
Original assignee: Snam Progetti
Priority date: 1977-01-18
Filing date: 1978-01-18
Publication date: 1983-01-26
Also published as: DE2802111B2; BE863039A; DE2802111A1; DK15878A; AU3232078A; FR2377567A1; IE780114L; BR7800345A; DK144665B; AU511844B2; GB1564493A; JPS5390017A; IT1078683B; DE2802111C3; FR2377567B1; NL7800626A; CA1086288A; DK144665C; LU78875A1; NL173093B

Abstract

A compact structure is disclosed for supporting a pipeline suspended over a sea bottom vale. The structure has a triangular outline, the sloping side of the triangle being a guideway of a wedge slidable unidirectionally, that is only upwards, until contacting the pipe to be supported. Actuating mechanisms are provided for the movable members of the triangular structure. The entire structure is mounted on a base plate and can be towed by a subsea vehicle until reaching the correct position.

Description

LAWS OF THE ITALIAN REPUBLIC, OF CORSO VENEZIA, 16, MILAN, ITALY.

Price 9 Op 6 0 2 9 This invention relates to an apparatus which may be used for supporting a submerged pipeline over a depression in a submarine bed; the apparatus may be used not only to support the pipeline but also to impart thereto an optimum predetermined configuration.

The sea bed is usually not completely flat, but usually includes obstacles of various types such as rock projections or fissures or depressions of varying sizes and depth, where a pipeline would be in a suspended state. When laying pipelines in shallow water it has been possible to avoid the pipeline being unduly suspended over such depressions but it is not always possible to prevent this when laying pipelines in deep water. When a pipeline becomes suspended over a wide depression the pipeline can kink or bend, and in extreme cases the pipeline can break.

Patent Specification No. 45718 described and claims an apparatus for use in supporting a pipeline suspended over a depression in a sea bed, the apparatus comprising:(a) a recoverable service component which is suitable for lowering from a surface vessel by a support cable to the submerged pipeline to be - 2 46029 supported, the service component being provided with guides to allow the service component to be slid along two parallel guide cables stretched in use between the surface vessel and the pipeline; and (b) a support component releasably connectible below the service component and provided with a clamp for clamping the support component around the pipeline, and with at least two support legs which can in use be extended onto or into the sea bed; wherein the service component is provided with coupling means for coupling it to, and release from, the support component, locking means for locking and releasing the support legs relative to the support component, and actuatable means for operating the clamp of the support component.

According to the present invention, there is provided an apparatus suitable for supporting a submerged pipeline over a depression in a submarine bed, which apparatus comprises a rigid structure equipped with positioning means for abutting the pipeline when the apparatus and pipeline are correctly positioned relative to each other, with movable supporting means which is different from the positioning means and is for supporting from below and upwardly urging the pipeline .with a non-return holding mechanism for holding in position the movable supporting means whilst permitting further upward movement of the movable supporting means, and with resting means for resting on the submarine bed; the arrangement of the apparatus being such that, in use, the apparatus is moved across a submarine bed until the positioning means abuts the pipeline, after which the movable supporting means is moved upwards so as to urge upwardly and to support from below the pipeline.

The present invention provides a simple, practical and cheap way of reliably supporting a pipeline suspended over a depression in a submarine bed, and the apparatus of the present invention may even be used to modify the configuration of the suspended section of the pipeline.

The apparatus of the present invention may thus be a simple rigid - 3 4 6 0 2 9 structure which does not need to be guided onto the pipeline laid in deep water in the manner of the support component of the apparatus described in Patent Specification No. 45718 . Instead, the apparatus of the present invention merely requires to be lowered onto the sea bed from a surface vessel (such as a servicing barge) and then pushed by a submarine vehicle beneath the pipeline to be supported, after which the apparatus can be actuated so as to support the pipeline from underneath with supporting means which can be displaced upwards with a force the magnitude of which can be adjusted.

Conveniently the apparatus is provided with one or more floodable and blowable buoyancy tank, such that with the apparatus submerged and the buoyancy tank(s) at least partially flooded, the apparent weight in water of the apparatus is zero. This assists in moving the apparatus under water.

According to one preferred embodiment of the apparatus of the present invention, the structure has a triangular outline and includes two parallel triangular frames, the positioning means being formed by an inclined side of each of the triangular frames, each of these two inclined sides being provided on their mutually opposing faces with a rack, the movable supporting means being formed by a wedge which is guidably slidable along these inclined sides, the ' non-return holding mechanism being formed by two non-return pawls which, supported by the wedge, are cooperable with the racks, and the resting means being composed by a base plate secured to the base of the triangular structure.

Preferably, in this embodiment the apparatus also includes a cable or other flexible elongate element which at one end is secured to the wedge and which passes around two freely rotatable pulleys one mounted intermediate opposing one end regions of the inclined sides and the other mounted intermediate opposing opposite end regions of the inclined sides.

In a modification of this embodiment of the invention, instead of causing the wedge to move under the action of the cable and pulley system, the - 4 46029 wedge may be caused to move along the inclined sides by an adjustable spring mechanicsm or by a hydraulic and/or pneumatic mechanism.

The embodiment with the triangular structure can only be satisfactorily used if the sea bed, irrespective of whether it is muddy, sandy or rocky is regular enough to provide adequate support for a wide base plate associated with this embodiment of the apparatus and also if the distance from the sea bed to the suspended pipeline does not exceed, at the point at which the pipeline must be supported, the height attainable by the inclined side of the triangular structure.

Another embodiment of the apparatus of the present invention may be used when the distance from the sea bed to the suspended pipeline to be supported is somewhat greater; in this embodiment of the apparatus, the structure has a body equipped with a hydraulic and/or pneumatic ram with the piston thereof intended to be disposed vertically, the positioning means being composed by two upwardly directed rods which, hinged to two sides of the body and connected each through calibrated springs, to an actuation mechanism for the hydraulic and/or pneumatic ram, in use actuate the ram only when they both come into contact with the suspended pipeline, the movable supporting means being formed by the piston of the ram which piston, being movable upwards, is equipped with racks arranged on opposite faces of the piston and terminates in a support block for supporting from beneath the suspended pipeline and the non-return holding mechanism being non-return pawls which, supported by the body, are cooperable with the racks of the piston.

In use of this embodiment of the apparatus, the apparatus is moved across the sea bed until both rods come into contact with the suspended pipeline whereupon the ram is actuated to cause the suspended pipeline to be moved upwards to the desired position.

The resting means may be a wide base plate secured to the bottom wall of the body. If, however, the sra bed is rathtr rne'en and rocky, the resting means may instead, be composed by four legs which can be telescopically - 5 46029 adjusted as to their height and are hinged at one end region to the bottom wall of the body, the opposite end regions of the legs being connected to each other pairwise by two adjustable clevis.

In the event that the sea bed is muddy or sandy, the resting means may be composed by four telescopically adjustable legs each of which is hinged at one end region to the bottom wall of the body and, at the other end, to a base plate, the four base plates being, in their turn, hinged to one another along two sides thereof.

In this manner the four base plates may form a single articulated base which can readily be adapted to the unevenness of the sea bed.

In a modification of this embodiment of the invention, the ram may be replaced by an adjustable spring mechanism for urging the piston upwards to support the pipeline.

For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:Figure 1 is a view towards one side of one embodiment of an apparatus according to the present invention; Figure 2 is a view towards an adjacent side of the embodiment of Figure 1; Figure 3 is a view towards one side of a different embodiment of an apparatus according to the present invention; and Figure 4 is a view towards an adjacent side of the embodiment of Figure 3.

Referring first to the embodiment shown in Figures 1 and 2, the rigid structure 1 has the shape of a triangle, most of which lies below a pipeline 2 which is suspended above a depression in a sea bed. The structure 1 includes two triangular frames which are parallel to each other and spaced apart from each other; each of these frames is composed of an inclined beam or side 3, a base beam or side 4 and a bracing beam or side 5. Reinforcing - 5 4 6029 struts 6 extend between the inclined beam or side 3 and the base beam or side 4, and connecting struts 7 (shown in Figure 2) extend between the reinforcing struts 6 and also between other parts of the frames.

In the opposing surfaces of the inclined sides 3 of the structure 1 are formed longitudinal grooves 8 for tongues 9 extending from the ends of a wedge 10, and in the same opposing surfaces there are racks 11 intended to cooperate with two non-return pawls 12 hinged to the wedge 10 and biassed by spring 13 so that the wedge 10 can rise along the inclined sides 3 but cannot slip backwards. To the upper side of the wedge 10 is secured a cable 14 which passes round a freely rotatable pulley 15 mounted on an axle 16 extending between the upper end regions of the inclined sides of the structure, and around a second freely rotatable pulley 17 mounted on an axle 18 supported by the lower end regions of the inclined sides 3. The other end of the cable 14 is secured to a ring 19. Beneath the base beams or slides 4 of the triangular structure 1 is affixed a wide base plate 20 which has upturned end regions 21 to facilitate the dragging of the structure on the sea bed.

In operation of the apparatus illustrated in Figures 1 and 2, the apparatus is positioned on the sea bed near the suspended pipeline and is then dragged or pushed by a submarine vehicle until the pipeline 2 abuts the inclined beams or sides 3 of the structure 1. The ring 19 is then pulled away from the structure 1, for example by means of the same submarine vehicle or by means of some other equipment carried by the structure 1, which causes the wedge 10 to be moved upwards along the inclined sides 3 which, in turn, causes the pipeline to be moved upwards and slightly to one side, although it is possible for the whole apparatus to be moved towards the ring 19 whilst the wedge 10 is moving up the inclined sides 3 so that, whilst the pipeline 2 is being moved upwards, it is not being displaced laterally. The pipeline 2 is moved upwards by the desired extent and in this connection it is worth - 7 46029 remarking that before bringing the apparatus into position, it will probably have been necessary to survey the pipeline and determine the stresses experienced by the pipeline, with a view to ascertaining the forces required to limit undue strain on the pipeline. The upward thrust of the wedge can be made equal to the forces calculated to minimise strain on the pipeline.

Referring now to Figures 3 and 4 of the drawings, a central part of the apparatus is a rigid structure in the form of a body 22 which is provided with a vertically disposed hydraulic or pneumatic ram 23. The piston of the ram supports at its free, upper end a support block 25 which has, viewed from one end, a cross-section like a V, and has, when viewed at right angles, an arcuate profile so that it is suitable for supporting pipelines of different diameters. On opposing surfaces of the piston 24 are racks which are cooperable with non-return pawls 27 biassed by springs and hinged to the body 22, in a manner such that the piston can be moved upwards but is prevented from moving downwards.

Two long positioning rods 28, which point upwards, are hinged near to their lower end regions by pins 29/stirrups 30 which are integral with two opposing sides of the body 22 and are connected, through calibrated springs 31 to an actuating mechanism of the ram 23 which mechanism is shown diagrammatically by the dotted lines 32. This mechanism acts on two inlet valves (not shown) for the ram 23 of the fluid under pressure contained in reservoirs 33 carried by the body 22, which valves are opened by the positioning rods 28 when both abut the suspended pipeline 2 and are rotated about their pins 29 by further dragging of the apparatus by a submarine vehicle. Also shown in Figure 3 are rings 34 for connecting the apparatus to the submarine vehicle used to drag the apparatus along the sea bed.

A wide base plate 35 (shown as broken lines in Figures 3 and 4) may be affixed to the base 36 of the body 22 for supporting the body on the submarine bed. As an alternative to the base plate 35, there may be fixed to the base 36 - 8 >46029 a plate 37 to which are hinged, via pins 38, four telescopically adjustable legs the length of which may be varied. Each leg is formed by a rod 39 having bores 40 and hinged at the pins 38 to the plate 37, and also by a hollow body 41 in which the rod 39 is inserted and is secured in position by a through-pin 42 passing through one of the bores 40 in the rod 39. The free lower ends of the hollow bodies 41 may then be mutually connected pair wise by adjustable clevis 43 (diagrammatically indicated by the broken lines in Figure 3). A further alternative is that in which the lower ends of the hollow bodies 41 are hinged by pins 44 to brackets 45 welded in the centre regions of four base plates 46, 47, 48 and 49. The four base plates 46 to 49 are hinged mutually along two of their sides so as to form, in effect, a single articulated base plate. More particularly, the base plate 47 is hinged to the adjoining plate 46 by a pin 50 parallel to the axis of the pipeline 2 and is also hinged to the adjoining plate 49 (see Figure 4) through the pin 51 which is perpendicular to and displaced from the axis of the pipeline 2.

Also shown in Figures 3 and 4 is a buoyancy tank 52 which is provided with a view to annulling the residual weight in water of the apparatus so as to facilitate the towing by a submarine vehicle of the apparatus to the desired site.

In operation, the piston 24 of the ram 23 is initially fully retracted and the apparatus, once in position on a submarine bed, is dragged towards the suspended pipeline by a submarine vehicle. When the rods 28 abut the pipeline 2, further movement of the apparatus 22 by means of the submarine vehicle causes the rods 28 to rotate about the pins 29 which causes the actuation of the mechanism 32, thus causing the piston 24 to be forced from the ram 23. The upward movement of the piston 24 causes it to abut the underside of the pipeline 22 and then to cause the pipeline to be moved upwards to the desired position. This upward movement can continue until the thrust exerted by the ram is equal to the calculated stress, using a pressure which has been preselected in the two reservoirs. Thus, knowing the - 9 correction of the pipeline required, the apparatus can be made to function automatically without needing the operation of external controls during the elevation of the suspended pipeline 2.

Claims

1. An apparatus suitable for supporting a submerged pipeline over a depression in a submarine bed, which apparatus comprises a rigid structure equipped with positioning means for abutting the pipeline when the apparatus and pipeline are correctly positioned relative to each other, with movable supporting means which is different from the positioning means and is for supporting from below and upwardly urging the pipeline, with a non-return holding mechanism for holding in position the movable supporting means whilst permitting further upward movement of the movable supporting means, and with resting means for resting on submarine bed; the arrangement of tho apparatus being such that, in use, the apparatus is moved across a submarine bed until the positioning means abuts the pipeline, after which the movable supporting means is moved upwards so as to urge upwardly and to support from below the pipeline.

2. An apparatus according to Claim 1, wherein the apparatus is provided with one or more floodable and blowable buoyancy tank such that, with the apparatus submerged in water and with the tank(s) at least partially flooded, the apparent weight in water of the apparatus is zero.

3. An apparatus according to Claim 1 or 2, wherein the structure has a triangular outline and includes two parallel triangular frames, the positioning means being formed by an inclined side of each of the triangular frames, each of these two sides being provided on their mutually opposing faces with a rack, the movable supporting means being formed by a wedge which is guidably slidable along these inclined sides, the non-return holding mechanism being formed by two non-return pawls which.supported by the wedge, are cooperable with the racks, and the resting means being composed by a base plate secured to the base of the triangular structure. - 10 46629

4. An apparatus according to Claim 3, which also includes a cable or other flexible elongate element which at one end is secured to the wedge and which passes around two freely rotatable pulleys one mounted intermediate opposing one end regions of the inclined sides and the other mounted intermediate opposing opposite end regions of the inclined sides.

5. An apparatus according to Claim 3, which also includes an adjustable spring mechanism for causing the wedge to move along the inclined sides.

6. An apparatus according to Claim 3, which also includes a hydraulic and/or pneumatic mechanism for causing the wedge to move along the inclined sides.

7. An apparatus according to Claim 1 or 2, wherein the structure has a body equipped with a hydraulic and/or pneumatic ram with the piston thereof intended to be disposed vertically, the positioning means being composed by two upwardly directed rods which, hinged to two sides of the body and connected each through calibrated springs to an actuation mechanism for the hydraulic and/or pneumatic ram, in use actuate the ram only when they both come into contact with the suspended pipeline, the movable supporting means being formed by the piston of the ram which piston, being movable upwards, is equipped with racks arranged on opposite faces of the piston and terminates in a support block for supporting from beneath the suspended pipeline, and the non-return holding mechanism being non-return pawls which, supported by the body, are cooperable with the racks of the piston.

8. An apparatus according to Claim 7, wherein the resting means is a base plate secured to the bottom wall of the body.

9. An apparatus according to Claim 7, wherein the resting means are composed by four legs which can be telescopically adjusted as to their height and are hinged at one end region to the bottom wall of the body the opposite end regions of the legs being connected to each other pairwise by two adjustable clevis. - 11 5

10. An apparatus according to Claim 7, wherein the resting means are composed by four telescopically adjustable legs each of which is hinged at one end region to the bottom wall of the body and, at the other end, to a base plate, the four base plates being, in their turn, hinged to one another along two sides thereof.

11. A modification of an apparatus according to any of Claims 7 to 10, wherein the ram is replaced by an adjustable spring mechanism for urging a piston upwards to support the pipeline.

12. An apparatus suitable for supporting a submerged pipeline over a depression in a submarine bed, substantially as hereinbefore described with reference to, and as illustrated in, Figures 1 and 2 or Figures 3 and 4 of the accompanying drawings.