GB2286647A

GB2286647A - Pipeline straightening apparatus

Info

Publication number: GB2286647A
Application number: GB9501764A
Authority: GB
Inventors: Robert George Martin
Original assignee: Stena Offshore Ltd
Current assignee: Technip UK Ltd
Priority date: 1994-02-11
Filing date: 1995-01-30
Publication date: 1995-08-23
Anticipated expiration: 2015-01-30
Also published as: GB9501764D0; GB2286647B

Abstract

Pipeline straightening apparatus comprises a first, main straightening roll assembly (26) facing one side of the pipeline (12), a second straightening roll assembly (28) located upstream of the main roll (26) facing the opposite side of the pipeline (12), and a third straightening roll assembly (30) located downstream of the main roll (26) also facing said opposite side of the pipeline (12), said straightening rolls being operable to effect straightening of the pipeline passing therebetween. The apparatus includes pipeline clamping/braking means comprising a brake shoe (32) located between said second and third straightener rolls (28, 30) on the opposite side of said pipeline path from said main straightener roll (26) and actuator means (46, 48) adapted for moving the shoe (32) in a direction substantially perpendicular to the pipeline path towards and away from the pipeline; and/or each of said first, second and third roll assemblies being mounted in a supporting frame for pivotable movement about respective first, second and third pivot axes (34, 36, 38) extending substantially through the longitudinal centres of the respective roll assemblies and substantially at right angles to the plane of pipeline bending. <IMAGE>

Description

Improvements in or relating to Pipeline Straightening The present invention relates to apparatus for straightening rigid walled pipeline, such as steel pipeline in marine pipelaying operations, which has been plastically deformed; e.g. by spooling onto a storage reel or by bending about a diverter shoe or the like in the course of a laying operation.

The apparatus and methods disclosed herein are particularly, but not exclusively, applicable for use in the context of the pipelaying apparatus and methods disclosed in the present applicant's co-pending UK Patent Application No. 9322424.4, filed 30 October 1993. This prior Application discloses a pipelaying system whereby a drilling vessel may be adapted for pipelaying operations by means of a pipe storage reel mounted on its deck, a pipeline diverter shoe located at a height on the drilling derrick and a straightener assembly suspended from the derrick below the diverter shoe, whereby the pipeline may be straightened and laid via the moonpool of the vessel. This arrangement allows the same vessel to be used for both drilling and pipelay operations, providing the possibility of exploitation of marginal hydrocarbon deposits.

Figs. 1 and 2 of the accompanying drawings show the derrick 10 of a drilling vessel adapted for pipelaying operations as described above. The pipeline 12 to be laid is fed from a storage reel (not shown), about an arcuate diverter shoe 16 mounted at a height on the derrick 10, and through a straightener assembly 14, embodying the present invention, which is suspended from existing crane hook 18 below the diverter shoe 16.

The straightener assembly 14 may be raised and lowered by means of the crane hook 18 between an uppermost position adjacent the diverter shoe 16 and a lowermost position at the mouth of the moonpool (not shown) at the bottom of the derrick 10.

The apparatus operates to straighten the pipeline 12 as follows: Firstly, with the straightening assembly 14 open and at its uppermost position, a tugger cable (not shown) is fed from a tugger winch (not shown, mounted below deck), through a pipeline clamp (not shown, mounted in the moonpool) and the straightening assembly 14, and around the diverter shoe 16 for attachment to the free end of the pipeline 12 emerging from the storage reel.

The tugger winch is then operated to pull the cable and pipeline 12 over the shoe 16, and through the straightener 14 until the pipeline 12 protrudes approximately 5 metres below the straightener 14, at which point the tugger cable is disconnected.

The straightener 14 is closed and clamped to the pipeline 12 and is lowered to its lowermost position, where it is clamped by the pipeline clamp, and an initiation cable (not shown) is attached. The straightener 14 is then unclamped from the pipeline 12, and is returned to its uppermost position, thereby straightening the length of pipe extending between the uppermost and lowermost positions (typically a length of about 24 metres).

The clamp is released, the straightener 14 is again clamped to the pipeline 12 and lowered therewith to its lowermost position, the clamp re-engages the pipeline 12, the straightener 14 is unclamped, and returned to its uppermost position to straighten the next length of pipe.

This cycle of operations is repeated until the free end of the pipe achieves vertical stab-in of the initiation head at a stab-in assembly located on the sea bed, guided by the initiation cable, which extends from the end of the pipe 12, through the stab-in assembly and back to an abandonment and recovery winch (not shown, mounted below deck). Once stab-in' is achieved the initiation cable is detached and the vessel proceeds with the pipelay, straightening the pipeline 12 as it is unspooled from the reel in the same manner as described above.

The pipeline straightening technique described above is as disclosed in UK Patent Application No. 9322424.4, wherein the straightener assembly may be any one of a number of known types.

The present invention provides a pipe straightening arrangement which is particularly suited for use in a pipelaying system of the type described above, and which may also find application in other situations where pipeline straightening is required.

In accordance with the invention there is provided pipeline straightening apparatus comprising a first, main straightening roll assembly having a pipeline contacting surface facing one side of the pipeline, in use, a second straightening roll assembly located upstream relative to the main roll in the pipeline feeding direction and having a pipeline contacting surface facing the opposite side of the pipeline, in use, and a third straightening roll assembly located downstream relative to the main roll in the pipeline feeding direction and having a pipeline contacting surface also facing said opposite side of the pipeline, said first, second and third straightening rolls being operable to engage a pipeline passing therebetween in order to effect straightening of said pipeline; said apparatus further including pipeline clamping/braking means comprising at least one brake shoe located between said second and third straightener rolls on the opposite side of said pipeline path from said main straightener roll and actuator means adapted for moving said shoe in a direction substantially perpendicular to said pipeline path towards and away from the pipeline contacting surface of said main straightener roll.

Preferably, each of said first, second and third roll assemblies are mounted in a supporting frame for pivotable movement about respective first, second and third pivot axes extending substantially through the longitudinal centres of the respective roll assemblies and substantially at right angles to the plane of pipeline bending.

Preferably also, said supporting frame comprises first and second side plates disposed in spaced, substantially parallel relationship, said straightener rolls and clamping/braking means being located therebetween.

Preferably also, said second, upstream roll assembly is further adapted for pivotable movement about a fourth axis located away from the longitudinal centre thereof and extending substantially at right angles to the plane of pipeline bending whereby the position of said second roll may be adjusted relative to the pipeline path.

Preferably also, said fourth axis is coincident with said first axis, said second roll being mounted between first and second swing arms for pivotable movement about said second axis and said swing arms being mounted for pivotable movement about said fourth axis.

Preferably also, the position of said second roll relative to said pipeline path is controlled by actuator means operably connected to said swing arms.

Preferably also, said brake shoe is pivotably connected at a lowermost end thereof about a fifth pivot axis between first ends of third and fourth swing arms disposed on either side of said third straightener roll, second ends of said third and fourth swing arms being pivotable about said third pivot axis.

Preferably also, said pipeline contacting surface of said main roll assembly is arcuate in longitudinal profile.

Preferably also, said pipeline contacting surfaces of said second and third rolls are substantially rectilinear in longitudinal profile.

In accordance with a second aspect of the invention there is provided pipeline straightening apparatus comprising a first, main straightening roll assembly having a pipeline contacting surface facing one side of the pipeline, in use, a second straightening roll assembly located upstream relative to the main roll in the pipeline feeding direction and having a pipeline contacting surface facing the opposite side of the pipeline, in use, and a third straightening roll assembly located downstream relative to the main roll in the pipeline feeding direction and having a pipeline contacting surface also facing said opposite side of the pipeline, said first, second and third straightening rolls being operable to engage a pipeline passing therebetween in order to effect straightening of said pipeline; each of said first, second and third roll assemblies being mounted in a supporting frame for pivotable movement about respective first, second and third pivot axes extending substantially through the longitudinal centres of the respective roll assemblies and substantially at right angles to the plane of pipeline bending.

Preferably, said apparatus further includes pipeline clamping/braking means comprising at least one brake shoe located between said second and third straightener rolls on the opposite side of said pipeline path from said main straightener roll and actuator means adapted for moving said shoe in a direction substantially perpendicular to said pipeline path towards and away from the pipeline contacting surface of said main straightener roll.

Further preferred features of the second aspect of the invention are the same as defined above in relation to the first aspect.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a first side view of pipeline straightening apparatus embodying the invention suspended from the derrick of a drilling vessel adapted for pipeline laying operations, viewed in a direction perpendicular to the plane of pipeline bending; Fig. 2 is a second side view of the apparatus and derrick of Fig. 1 viewed along the plane of pipeline bending; Fig. 3 is a first schematic side view of the apparatus of Fig. 1 viewed along the plane of pipeline bending; Fig. 4 is a second schematic side view of the apparatus of Fig 1 viewed in a direction perpendicular to the plane of pipeline bending; Fig. 5 is a side view of a roller track assembly being the first of three straightening rolls of the apparatus of Figs.

1 to 4; Fig. 6 is a side view of a roller track assembly used for the second and third of the three straightening rolls of Figs 1 to 4; Fig. 7 is a side view of the apparatus similar to that of Fig. 4 engaging a first pipeline of relatively large diameter; Fig. 8 is a side view of the apparatus similar to that of Fig. 4 engaging a first pipeline of relatively small diameter; Figs. 9(a) and 9(b) are side views similar to Fig. 7 showing the operation of the apparatus with a pipeline of relatively large diameter; and Figs. 10(a) and 10(b) are side views similar to Fig. 8 showing the operation of the apparatus with a pipeline of relatively small diameter.

Referring now to the drawings, Figs. 1 and 2 show a pipeline straightening apparatus 14 embodying the invention installed as part of a pipelaying system as described above. The purpose of the straightener assembly 14 is to impart a reverse bending force to the pipeline 12 sufficient to overcome the curvature imparted to the pipeline 12 by plastic deformation thereof during spooling onto the storage reel and/or bending around the diverter shoe 16. For this purpose three reaction points are required to be exerted on the pipe, the two end points acting in one direction and the intermediate point acting in the opposite direction, such that all three forces are substantially co-planar in the plane of bending.

A variety of "three-point straighteners" of this general type are known from the prior art, for example from US Patents Nos. 3,237,438; 3,641,778; 3,680,342; 3,712,100; 3,855,835; 3,982,402 (RE 30,846); 4,157,023; 4,230,421; 4,243,345; 4,260,287; 4,260,287 and 4,687,376. These prior art straighteners generally fall into two categories: straighteners which use arrangements of individual rollers (as seen in US Patents Nos. 3,855,835; 4,157,023; 4,243,345 and 4,260,287), most often used in "portable reel" systems where storage reels and associated apparatus for laying relatively small diameter pipes are temporarily installed on existing vessels; and "roller track" type straighteners which use up to five caterpillar type track assemblies for straightening and/or tensioning relatively large pipelines on purpose-built or permanently adapted vessels (as seen, for example, in US Patents Nos. 3,680,342; 3,982,402 (RE 30,846); 4,230,421; 4,269,540 and 4,687,376). The present invention is concerned with the latter roller track type of straightener. Reference is made particularly to US Patent No. 3,680,342 for a detailed disclosure of roller track assemblies of the type employed in such straightener systems, and suitable also for use in the present invention. Further reference will be made to particular details of such roller track assemblies in the course of the following description.

Referring now to Figs. 3 to 6 of the drawings, straightener apparatus 14 embodying the invention comprises a self-contained assembly in which all of the major components are mounted between first and second side plates 20, 22, the assembly 14 having a padeye 24 located at an upper end thereof whereby it may be suspended in use, for example from the crane hook 18 of the derrick 10 as seen in Figs. 1 and 2. The main components of the apparatus comprise a first, main roller track assembly, or "straightening roll", a second, upper roller track assembly 28, a third, lower roller track assembly 30 and a pipeline braking/clamping shoe 32. In use, the pipeline 12 passes through the assembly 14 between the main roll 26, disposed on one side of the pipeline path, and the upper and lower rolls 28, 30 disposed on the opposite side of the pipeline path and respectively upstream and downstream of the main roll 26 in the direction of pipeline unspooling. The braking/clamping shoe 32 is located between the upper and lower straightener rolls 28, 30, facing the pipeline contacting surface of the main roll 26.

Each of the first, second and third straightener rolls 26, 28, 30 are mounted for pivotable movement about respective pivot axes 34, 36, 38, extending substantially through the longitudinal centres of the respective straightener rolls 26, 28, 30 perpendicular to the plane of pipeline curvature (i.e. perpendicular to the side plates 20, 22).

The first and third straightener rolls 26, 30 are pivotably mounted between the side plates 20, 22. The second roll 28 is pivotably mounted between a pair of swing arms 40, of which only one is visible in the drawings, the swing arms 40 themselves being pivotable about a fourth pivot axis, which is conveniently coincident with the first pivot axis 34 of the first roll 26. The first and third rolls 26, 30 are thus pivotably movable about their respective pivot axes 34, 38, whilst the second roll is pivotable about its pivot axis 36 and movable towards and away from the pipeline path by pivoting movement of the swing arms 40 about the first axis 34.

In order to effect adjustment of the position of the second roll 28 relative to the pipeline path, a hydraulic or pneumatic cylinder 42, or other suitable actuator means, is mounted between the side plates 20, 22, with its working end connected to the free ends of the swing arms 40 remote from their pivot axis 34. The central pivot pin of the second straightener roll 28 extends into arcuate guide slots 44 formed in the side plates 20, 22, of which only one is visible in the drawings, to guide and limit the movement of the swing arms 40.

The position of the swing arm pivot axis may be varied from that shown. It is generally desirable for the axis to be downstream of the second roll 28 on the opposite side of the pipeline path therefrom, and to be at a sufficient distance from the second roll 28 to provide a reasonable lever arm. It is structurally convenient and advantageous for the swing arms 40 to pivot about the same axis as the main roll 26, but this is not essential to the operation of the apparatus.

The braking/clamping shoe 32 is mounted on second and third hydraulic or pneumatic cylinders 46, 48 mounted between the side plates 20, 22, or other suitable actuator means, for movement in a direction substantially perpendicular to the pipeline path in the plane of pipeline bending. The lowermost end of the brake shoe 32 is pivotably connected about a fifth pivot axis 43 between first ends of a further pair of swing arms 41, of which only one is visible in the drawings, the other ends of the swing arms 41, which are disposed on either side of the third straightener roll 30, are pivoted about the third pivot axis 38 about which the third roll 30 itself pivots.

As previously indicated, the straightener rolls 26, 28 and 30 are of a generally known type, comprising an endless caterpillar type roller track 50, 52 rotatable around the periphery of a supporting structure 54, 56.

The tracks 50, 52 each comprise a plurality of linked blocks having a transverse arcuate or v-shaped profile (not shown) for seating against the pipeline surface.

The pipe contacting portions of the blocks may be faced with polyurethane or the like to protect the pipeline.

Reference is made to US Patent No. 3,680,342 for a more detailed discussion of these and other aspects of straightener rolls of this type. It should also be understood that the caterpillar tracks 50, 52 might be replaced by a series of discrete rollers rotatably mounted in the support structures 54, 56 along the pipeline facing side thereof, as is also known in the art.

The braking/clamping shoe 32 may have a similar configuration to one of the blocks of the caterpillar tracks 50, 52, but being relatively larger, particularly in terms of longitudinal length.

The main straightener roll 26 is generally longer than the second and third rolls 28, 30, and the pipe contacting face 58 thereof is preferably arcuate in longitudinal profile. The radius of longitudinal curvature of the face 58 may be fixed at a value which suits a range of pipeline diameters, or the roll assembly may be adapted to allow variation of the radius of curvature so as to be optimised for particular pipeline diameters. A straightener roll having variable curvature is disclosed in US Patent No.

4,687,376. The second and third straightener rolls 28, 30 are relatively shorter than the main roll 26 and their pipeline contacting faces are substantially rectilinear in longitudinal profile.

The braking/clamping shoe 32, in cooperation with the main roll 26, performs pipeline clamping and braking functions, so that the straightener rolls 26, 28 and 30 may be unpowered (i.e. their tracks or rollers do not have to be driven) and only the second roll 28 need be movable relative to the pipeline path so as to adjust the apparatus for straightening pipelines of different diameters. Prior art straighteners include adjustable, powered straightener rolls which may perform clamping and tensioning/braking functions in addition to straightening. The present apparatus provides a simplified arrangement which is less costly to construct and which is relatively simpler and quicker to set up in comparison with prior art systems.

In use of the present apparatus in the pipelaying system illustrated in Figs. 1 and 2, the braking/clamping shoe 32 serves firstly for clamping the pipeline 12 while the straightener is initially lowered from its upper position to its lower position, and subsequently to tension the pipeline during the straightening phase of each cycle of operation.

Figs. 7 and 8 show side views of the apparatus of Figs.

3 to 6 adjusted for six inch and two inch diameter pipelines respectively by appropriate adjustment of the pistons of the roll and brake shoe cylinders 42, 46, 48. The relative positions of the second straightener roll 28, swing arms 40 and brake shoe 32 can be seen by comparison of the drawings. Figs. 9 and 10 show the "snap-action" operation of the apparatus in engaging the pipeline after initial feeding through the apparatus, again for six and two inch diameter pipelines respectively. In each case the second roll 28 and brake shoe 32 are initially retracted clear of the pipeline path, allowing the pipeline 12 to be fed through the apparatus. The first cylinder 42 and the brake cylinders 48, 50 are then operated to bring the second roll 28 and brake shoe 32 into engagement with the pipeline 12 as required. The three straightener rolls 26, 28, 30 pivot about their respective axes to orient themselves with the pipeline.

The straightening apparatus as herein described has significant advantages in terms of its simplicity of construction and operation, and its configuration as a relatively compact, self-contained assembly is advantageous, being readily portable for installation as part of the temporary adaptation of a vessel for pipelaying operations and requiring external power supplies only for the swing arm and brake shoe actuators.

Improvements and modifications may be incorporated without departing from the scope of the invention.

Claims

1. Pipeline straightening apparatus comprising a first, main straightening roll assembly having a pipeline contacting surface facing one side of the pipeline, in use, a second straightening roll assembly located upstream relative to the main roll in the pipeline feeding direction and having a pipeline contacting surface facing the opposite side of the pipeline, in use, and a third straightening roll assembly located downstream relative to the main roll in the pipeline feeding direction and having a pipeline contacting surface also facing said opposite side of the pipeline, said first, second and third straightening rolls being operable to engage a pipeline passing therebetween in order to effect straightening of said pipeline; said apparatus further including pipeline clamping/braking means comprising at least one brake shoe located between said second and third straightener rolls on the opposite side of said pipeline path from said main straightener roll and actuator means adapted for moving said shoe in a direction substantially perpendicular to said pipeline path towards and away from the pipeline contacting surface of said main straightener roll.

2. Pipeline straightening apparatus as claimed in Claim 1, wherein each of said first, second and third roll assemblies are mounted in a supporting frame for pivotable movement about respective first, second and third pivot axes extending substantially through the longitudinal centres of the respective roll assemblies and substantially at right angles to the plane of pipeline bending.

3. Pipeline straightening apparatus comprising a first, main straightening roll assembly having a pipeline contacting surface facing one side of the pipeline, in use, a second straightening roll assembly located upstream relative to the main roll in the pipeline feeding direction and having a pipeline contacting surface facing the opposite side of the pipeline, in use, and a third straightening roll assembly located downstream relative to the main roll in the pipeline feeding direction and having a pipeline contacting surface also facing said opposite side of the pipeline, said first, second and third straightening rolls being operable to engage a pipeline passing therebetween in order to effect straightening of said pipeline; each of said first, second and third roll assemblies being mounted in a supporting frame for pivotable movement about respective first, second and third pivot axes extending substantially through the longitudinal centres of the respective roll assemblies and substantially at right angles to the plane of pipeline bending.

4. Pipeline straightening apparatus as claimed in Claim 3, further including pipeline clamping/braking means comprising at least one brake shoe located between said second and third straightener rolls on the opposite side of said pipeline path from said main straightener roll and actuator means adapted for moving said shoe in a direction substantially perpendicular to said pipeline path towards and away from the pipeline contacting surface of said main straightener roll.

5. Pipeline straightening apparatus as claimed in Claim 2, Claim 4, wherein said supporting frame comprises first and second side plates disposed in spaced, substantially parallel relationship, said straightener rolls and clamping/braking means being located therebetween.

6. Pipeline straightening apparatus as claimed in any one of Claims 2, 3, 4 or 5, wherein said second, upstream roll assembly is further adapted for pivotable movement about a fourth axis located away from the longitudinal centre thereof and extending substantially at right angles to the plane of pipeline bending whereby the position of said second roll may be adjusted relative to the pipeline path.

7. Pipeline straightening apparatus as claimed in Claim 6, wherein said fourth axis is coincident with said first axis, said second roll being mounted between first and second swing arms for pivotable movement about said second axis and said swing arms being mounted for pivotable movement about said fourth axis.

8. Pipeline straightening apparatus as claimed in Claim 7, wherein the position of said second roll relative to said pipeline path is controlled by actuator means operably connected to said swing arms.

9. Pipeline straightening apparatus as claimed in Claim 7 or Claim 8 when dependent from Claim 2, Claim 4 or Claim 5, wherein said brake shoe is pivotably connected at a lowermost end thereof about a fifth pivot axis between first ends of third and fourth swing arms disposed on either side of said third straightener roll, second ends of said third and fourth swing arms being pivotable about said third pivot axis.

10. Pipeline straightening apparatus as claimed in any preceding Claim, wherein said pipeline contacting surface of said main roll assembly is arcuate in longitudinal profile.

11. Pipeline straightening apparatus as claimed in any preceding Claim, wherein said pipeline contacting surfaces of said second and third rolls are substantially rectilinear in longitudinal profile.

12. Pipeline straightening apparatus substantially as hereinbefore described with reference to the accompanying drawings.