AU701870B2 - Apparatus for handling elongate members - Google Patents

Description

-1 WO 96/30686 PCT/GB96/00638 1 "Apparatus for Handling Elongate Members" 2 3 This invention relates to apparatus for handling 4 elongate members such as rigid and flexible pipelines, ropes or cables. The apparatus is of particular 6 interest for use in the laying of rigid submarine 7 pipelines, but may also be useful in laying flexible 8 pipelines or as a winch for cables and ropes.

9 The invention relates to apparatus which, in its 11 preferred embodiments, is suitable for diverting a 12 pipeline about an arcuate path between an initial angle 13 of orientation and a second angle of orientation. In a 14 typical application of the invention, the apparatus might be used on a marine pipelaying vessel to divert a 16 pipeline from an initial horizontal orientation to a 17 final launch angle at a substantial inclination to the 18 horizontal. The diversion of the pipeline will 19 generally involve plastic bending of the pipe, which in most cases would be followed by subsequent 21 straightening, or at least partial straightening.

22 However, the invention is also applicable in cases 23 where the pipeline diversion involves elastic bending 24 to a degree which does not exceed the yield limit of P:\OPER\KAT\51143-96 339- 7/1298 -2the pipeline material. It may also find application in the handling of other elongate members such as cables and ropes. In the preferred embodiments, the invention serves to divert the pipeline or other elongate member, initially upwardly, from the horizontal, through an angle greater than 1800, such that the elongate member crosses over itself. The invention is particularly, but not exclusively, applicable to the laying of large diameter pipe which it is not practicable to coil on a reel and which must therefore be assembled on the lay vessel.

In accordance with a first aspect of the invention there is provided apparatus for handling elongate members comprising a plurality of roller track assemblies mounted on a supporting structure and arranged in series to define a substantially arcuate path around which said elongate members pass, wherein the direction of travel of each of said roller track assemblies is oriented so as to be substantially parallel to said arcuate path and to the direction of travel of said elongate members along said path.

Preferably, said roller track assemblies are arranged so as to define a helicoidal path.

.Preferably, said elongate member is a pipeline and the apparatus is adapted to divert said Si• pipeline from an initial angle of orientation to a second angle of orientation.

20 Preferably, the pipeline is a rigid pipeline which is plastically bent by passing around said arcuate path.

*The radius of curvature of the substantially arcuate O V 0 0000.0 WO 96/30686 PCT/GB96/00638 3 1 path may be substantially constant or may vary along 2 the length of the path.

3 4 Preferably, each of said roller track assemblies has an outwardly facing, bearing surface. Preferably also, 6 said bearing surface is arcuate in longitudinal 7 profile. Preferably also, the radius of curvature of 8 said arcuate profile is less than the corresponding 9 radius of curvature of said substantially arcuate path.

11 One or more of said roller track assemblies may include 12 drive means such that those assemblies which include 13 drive means are adapted to apply tension to said 14 elongate member. One or more of said assemblies which include drive means may have associated therewith a 16 further, driven roller track assembly disposed on the 17 opposite side of said substantially arcuate path 18 therefrom, one or other or both of said driven assembly 19 and said further driven assembly being movable towards and away from the other so as to apply a compressive 21 force to said elongate member. The longitudinal lengths 22 of the roller track assemblies may vary along the 23 length of the path, preferably decreasing in the 24 direction of travel of the elongate member.

26 In preferred embodiments, the pipeline path is 27 preferably configured to divert said elongate member 28 through a net angle greater than 1800, and most 29 preferably through a net angle equal to or greater than 2700.

31 32 Each of said roller track assemblies preferably 33 includes an endless belt having a series of pads 34 secured to the outer surface thereof for contacting said elongate member. In preferred embodiments, said j P:\OPER\KAT\51143-96.339 7/12/98 -4pads include a plurality of grooves adapted to accommodate different types and sizes of elongate members.

The apparatus may be adapted to divert a pipeline from an initial angle of orientation to a second angle of orientation. In preferred embodiments, the pipeline is a rigid pipeline which is plastically bent by passing around said substantially arcuate path.

In accordance with a second aspect of the invention, there is provided a marine pipelaying vessel including apparatus for handling elongate members in accordance with the first aspect of the invention.

Preferably, a vessel in accordance with the second aspect of the invention includes a deck area, means on the deck area for aligning pipe sections along a substantially horizontal axis and connecting said pipe sections together to form a pipeline, and said apparatus is adapted for bending the pipeline to cause it to pass from said horizontal axis to a launch axis having a substantial inclination to the horizontal.

Preferably, said pipeline bending means is adapted to plastically bend the pipeline about a osubstantially arcuate path in a substantially vertical plane.

The vessel preferably further includes means for applying tension to said pipeline, and means for WO 96/30686 PCT/GB96/00638 1 controlling said tension to ensure that the bending of 2 the pipeline at the point where it meets the sea bed is 3 within the elastic yield limit of the pipe material.

4 Straightening means are preferably also provided 6 downstream of said bending means for at least partially 7 removing the bend in the pipeline.

8 9 In preferred embodiments said apparatus is adapted to bend said pipeline upwardly along a substantially 11 arcuate path and subsequently to bend said pipeline 12 downwardly to a final launch angle.

13 14 In one such embodiment, means are provided for feeding the pipeline in a direction from the bow of the vessel 16 towards the stern thereof and said apparatus is adapted 17 to divert said pipeline through an angle of 18 substantially 2700 or greater, and typically less than 19 or equal to 3100.

21 The pipeline may be diverted through one or more 22 complete turns, in which case said apparatus is adapted 23 to divert said pipeline through an angle greater than 24 or equal to 2700 plus an integer multiple of 3600, and typically less than or equal to 3100 plus said integer 26 multiple of 3600.

27 28 Alternatively, the vessel may include means for feeding 29 the pipeline in a direction from the stern of the vessel towards the bow thereof and said apparatus is 31 adapted to divert said pipeline through an angle of 32 substantially 2700 or less, and typically greater than 33 or equal to 2300.

34 Again, the pipeline may be diverted through one or more WO 96/30686 PCT/GB96/00638 6 1 complete turns, in which case said apparatus is adapted 2 to divert said pipeline through an angle less than or 3 equal to 2700 plus an integer multiple of 3600, and 4 typically greater than or equal to 2300 plus said integer multiple of 3600.

6 7 In these embodiments, the pipeline may be launched from 8 the side of the vessel over the stern or the bow of the 9 vessel, or via a moon-pool.

11 The vessel preferably also includes means for varying 12 the launch angle of the pipeline by varying the point 13 at which the pipeline departs from said substantially 14 arcuate path, straightening means for straightening said pipeline after it departs from said substantially 16 arcuate path, and pipe guide means through which said 17 pipeline passes after being straightened. Preferably, 18 said pipe guide means is adapted to be translated in a 19 fore and aft direction so as to vary the launch angle of the pipeline.

21 22 The vessel preferably also includes tensioning means 23 for applying tension to the pipeline, located upstream 24 of said pipeline supporting structure in the direction of pipeline travel, and/or tensioning means for 26 applying tension to the pipeline, located downstream of 27 said pipeline supporting structure in the direction of 28 pipeline travel, and/or said apparatus is adapted for 29 applying a braking force to said pipeline as it passes around said substantially arcuate path.

31 32 The plane of said substantially arcuate path may lie in 33 a single plane, in which case the plane of the path is 34 preferably disposed at an angle to the vertical plane including the horizontal pipeline assembly axis, and P:\OPER\KAT\51143-96.339 112/98 -7the vessel includes alignment means for diverting the pipeline in a horizontal plane into alignment with the plane of said substantially arcuate path prior to the pipeline engaging said substantially arcuate path. Most preferably, said alignment means is adapted to effect said horizontal diversion prior to said pipeline being diverted upwardly to engage said substantially arcuate path. Alternatively, said substantially arcuate path may be helicoidal, such that the pipeline is diverted horizontally as it passes around said path. In this case the upstream end of the substantially arcuate path in the direction of pipeline travel may be substantially colinear with the horizontal pipeline assembly axis.

In accordance with a third aspect of the invention, there is provided a method of initiating pipelaying operations in a marine pipelaying system in which a pipeline is passed around an arcuate path in order to divert said pipeline to a desired launch angle, comprising the steps of securing a length of pipe which has been pre-bent to a radius of curvature substantially equal to the radius of curvature of said arcuate path to the downstream end of a pipeline which is to be passed around said arcuate path, securing an initiation cable to the downstream end of said pre-bent pipe length, pulling said pipeline around said arcuate path by means of said initiation cable, and detaching said initiation cable and said pre-bent pipe length prior to S: •"commencing pipelaying operations.

20 In accordance with a fourth aspect of the invention, there is provided a method of interrupting *pipelaying operations in a marine pipelaying system in which a pipeline is passed around an arcuate path in order to **go °*oo *oooo WO 96/30686 PCT/GB96/00638 8 1 divert said pipeline to a desired launch angle, 2 comprising the steps of stopping pipelaying operations, 3 clamping the pipeline at a first location where the 4 pipeline departs from said arcuate path, clamping the pipeline at a second location downstream of said first 6 location in the direction of pipeline movement, cutting 7 said pipeline at a location intermediate said first and 8 second locations, displacing the pipeline passing 9 around said arcuate path radially outwards from said arcuate path, passing an abandonment and recovery

(A&R)

11 cable around said arcuate path in the direction of 12 normal pipeline movement around said path, and securing 13 said A&R cable to the upstream end of the pipeline 14 clamped at said second location.

16 The outward displacement of the pipeline passing around 17 said arcuate path may be effected by relaxing the back 18 tension on said pipeline and or by feeding said 19 pipeline around said arcuate path. The outward displacement may be restrained by restraining means 21 mounted on a pipeline diverter structure defining said 22 arcuate path and located radially outwards from said 23 arcuate path. A straightener mechanism located 24 adjacent the point of departure of the pipeline from said arcuate path may be utilised to clamp the pipeline 26 at said first location.

27 28 In the present application, the term "roller track 29 assembly" is used to designate an assembly of generally known type in which an endless conveyor belt or track 31 or chain or the like is mounted around a supporting 32 chassis including end sprockets (driven or idle) and 33 support rollers, in the manner of a caterpillar track.

34 Roller track assemblies of this general type have been used in apparatus for straightening rigid pipelines, WO 96/30686 PCT/GB96/00638 9 1 for tensioning pipelines, cables, ropes etc., and for 2 aligning pipelines. A typical straightener employs 3 three-point straightening as is well known in the art 4 and is discussed in US Patents Nos.3,237,438 and 3,372,461. Examples of roller track assemblies and 6 their use in pipeline straightening are described in US 7 Patents Nos. 3,855,835, 4,157,023, 4,243,345 and 8 4,260,287. Alternative "roller-track" type assemblies 9 are also described in US Patents Nos. 4,230,421, 4,269,540, 4,297,054, 4,340,322 and 4,345,855, and 11 further in US Patents Nos. 3,641,778, 3,680,342, Re 12 30,846 and 4,723,874. In general, the roller track 13 assemblies are arranged on opposite sides of the pipe, 14 and means are provided for positioning the tracks to impart a reverse bending force.

16 17 A typical tensioner may suitably comprise two similar 18 roller track assemblies engaging the elongate member on 19 opposite sides thereof and means, such as hydraulic motors, for driving the tracks to apply a braking force 21 to the elongate member.

22 23 Embodiments of the present invention will now be 24 described, by way of example only, with reference to the accompanying drawings, in which: 26 27 Figs. l(a) and l(b) are, respectively 28 schematic side and plan views of a marine 29 pipelaying vessel of a type in which apparatus in accordance with the invention 31 may be employed; 32 33 Fig. 2 is a schematic side view illustrating 34 the pipeline catenary between the vessel and the seabed for the embodiment of Figs. l(a) WO 96/30686 PCT/GB96/00638 1 and l(b); 2 3 Fig. 3 is a schematic side view of a more 4 detailed embodiment of a vessel similar to that of Figs. 1 and 2; 6 7 Fig. 4 is a plan view of the embodiment of 8 Fig. 3; 9 Fig. 5 is an enlarged, partial side view of a 11 pipeline diverting and launching mechanism of 12 the embodiment of Fig. 3; 13 14 Fig. 6 is a plan view of the mechanism of Fig. 16 17 Fig. 7 is a schematic side view of an 18 embodiment of apparatus for handling elongate 19 members in accordance with the invention; 21 Fig. 8 is a schematic plan view of one 22 variant of the apparatus of Fig. 7; 23 24 Fig. 9 is a schematic side view of a more detailed example of an embodiment of 26 apparatus for handling elongate members, in 27 accordance with the invention; 28 29 Figs. 10(a) and 10(b) are, respectively, a schematic, transverse sectional view and a 31 schematic side view of a first example of 32 pipeline bearing arrangements for use in the 33 apparatus of Figs. 7 to 9; 34 Figs. 11(a) and 11(b) are, respectively, a WO 96/30686 PCT/GB96/00638 11 1 schematic, transverse sectional view and a 2 schematic side view of a second example of 3 pipeline bearing arrangements for use in the 4 apparatus of Figs. 7 to 9; 6 Figs. 12(a) and 12(b) are, respectively, a 7 schematic, transverse sectional view and a 8 schematic side view of a third example of 9 pipeline bearing arrangements for use in the apparatus of Figs. 7 to 9; 11 12 Figs. 13(a) and 13(b) are, respectively, a 13 schematic, transverse sectional view and a 14 schematic side view of a fourth example of pipeline bearing arrangements for use in the 16 apparatus of Figs. 7 to 9; 17 18 Fig. 14 is a schematic side view of a further 19 embodiment of apparatus for handling elongate members in accordance with the invention; 21 22 Fig. 15 is a schematic end view illustrating 23 the helicoidal path defined by the apparatus 24 of Fig. 14: and 26 Figs. 16(a) are schematic side views of 27 a pipe diverter structure illustrating 28 methods of feeding a pipeline around an 29 arcuate diverter structure and subsequently displacing the pipeline from the diverter 31 structure to allow the passage of an 32 abandonment and recovery cable, in accordance 33 with further aspects of the invention.

34 Before describing detailed embodiments of apparatus for WO 96/30686 PCT/GB96/00638 12 1 handling elongate members in accordance with the 2 invention, examples of pipelaying vessels to which the 3 invention may be applied will be described briefly, by 4 way of background.

6 Figs. l(a) and l(b) show an embodiment of a marine 7 pipelaying vessel which is particularly suited to 8 deepwater operations, and includes a sheave, wheel or 9 equivalent structure 40 for diverting the pipeline 42 through substantially 2700 or more from the horizontal 11 so as to enter the water substantially vertically or at 12 some required angle. The wheel 40 might have a diameter 13 of approximately 50 metres and is rotatably mounted 14 adjacent one side of the vessel 44 on a support structure 46. Apparatus in accordance with the present 16 invention may be employed to provide the pipeline 17 diverting structure 18 19 Where the vessel is used for laying rigid pipeline which is plastically deformed whilst passing around the 21 pipeline diverter structure 40, the support structure 22 46 may also support straightening means (not shown, 23 suitably of any of a number of types known in the art) 24 for straightening the pipeline 42 as it leaves the diverter structure 40, and abandonment and recovery 26 equipment (ie pipeline clamps and winches and the 27 like), as is well known in the art. For very high 28 pipeline tensions, A&R operations may involve the use 29 of a drill string (rather than a cable), which may be deployed from a short derrick disposed above the 31 pipeline departure point.

32 33 Since the pipeline leaving the diverter structure 34 must cross the horizontal path of the pipeline being fed onto the diverter structure, arrangements must be WO 96/30686 PCT/GB96/00638 13 1 made to allow the pipeline to cross itself without 2 clashing.

3 4 If the pipeline path defined by the diverter structure lies in a single plane (as would be the case if the 6 pipeline path extends around the rim of a circular 7 wheel, for example) the plane of the diverter structure 8 40 is set at a slight angle to the vertical plane 9 including the horizontal pipeline path, and the horizontal pipeline path is curved slightly as it 11 approaches the wheel rim, as is best seen in Fig. l(b).

12 This horizontal diversion of the pipeline path to allow 13 the pipe to cross itself is advantageously carried out 14 at the entry of the pipe to the wheel rather than after its departure therefrom, since the required curvature 16 of the pipe can be controlled using a horizontal track 17 on the deck of the vessel, and the lower pipeline 18 tension before feeding around the wheel allows tighter 19 curvature.

21 However, certain embodiments of the present invention 22 allow the diverter structure to define a helicoidal 23 path which itself diverts the pipeline sideways, as 24 shall be described in greater detail below, so that the pipeline may cross itself without the need for this 26 prior horizontal diversion.

27 28 This pipelaying vessel is suited to the application of 29 high pipeline tensions, required for deepwater laying, without resort to expensive track-type tensioners, by 31 means of: first and second fixed pipeline clamps (not 32 shown) before and after the wheel 40 on the horizontal 33 and vertical pipeline paths respectively; a horizontal 34 moving clamp (not shown) located before the first fixed clamp, for lowering the pipeline joint by joint; and by WO 96/30686 PCT/GB96/00638 14 1 driving the wheel. With a correctly profiled wheel rim, 2 the wheel can be made to transmit the full lay tension 3 required. However, in practice a degree of back tension 4 would always be maintained. Possible alternative strategies for applying the required tension will be 6 discussed further below.

7 8 Fig. 2 illustrates a typical profile of the catenary 9 curve of a pipeline extending between the vessel 44 at the surface 48 and the seabed 50. This embodiment is 11 suited to the use of an adapted tanker as the lay 12 vessel, having a very large clear deck area for the 13 assembly of pipe stalks and large capacity for the 14 storage of pipe joints below decks.

16 The pipeline path defined by the diverter structure 17 may comprise the rim of a wheel mounted for rotation 18 about a central hub, or other means such as a static 19 structure having rollers or an endless belt conveyor for supporting the pipeline as it is diverted through 21 the required angle. Advantageously, the pipeline path 22 may be defined by apparatus in accordance with the 23 present invention, as shall be described further below.

24 Figs. 3 to 6 illustrate a further developed embodiment 26 of a pipelay vessel incorporating a pipelay system 27 similar in general concept to that of Figs. 1 and 2.

28 29 The vessel of Figs. 3 to 6 includes a pipeline diverter structure generally designated by the reference numeral 31 100, mounted at the stern of the vessel. The structure 32 100 is adapted to divert the pipeline 102 about an 33 arcuate path through an adjustable angle of 34 substantially 270' or more, as in the embodiment of Fig.

i. This provides a pipeline launch angle which is WO 96/30686 PCT/GB96/00638 1 variable up to 900. The arcuate pipeline path is defined 2 by a curved structure 104 (circular in this example), 3 which shall be referred to herein, for convenience, as 4 a "wheel".

6 As in the embodiment of Fig. 1, the wheel 104 might, 7 for example, comprise a pipeline supporting conveyor 8 extending around the peripheral rim of a static 9 circular structure. The pipeline conveyor may comprise a series of idle rollers having their axes of rotation 11 extending at right angles to the direction of pipeline 12 travel. Alternatively, the conveyor might comprise a 13 continuous, endless belt or chain type conveyor 14 encircling the supporting structure. An endless belt conveyor of this type may be driven or may be idle.

16 Pipeline conveyors of these types are known in the art, 17 as used in the pipe bearing portions of straighteners, 18 tensioners, aligners and stingers, and the like, and 19 shall not be described in greater detail herein. It will be appreciated that, again, the pipeline diverter 21 could also be implemented with a wheel which rotates 22 about a central axis, as discussed above in relation to 23 Fig. 1. Again, however, the wheel 104 might 24 advantageously be provided by apparatus in accordance with the present invention, as shall be described 26 below.

27 28 Also, the wheel 104 might alternatively be mounted at 29 the bow of the vessel, in which case the angle through which the pipeline is diverted would be less than 270' 31 for launch angles less than 90*; ie the adjustability of 32 the exit angle of the pipeline 102 from the wheel 104 33 would be in the opposite direction from that 34 illustrated in the present example.

WO 96/30686 PCT/GB96/00638 16 1 In the case where the pipeline supporting surface of 2 the wheel comprises a roller type conveyor, the rollers 3 of the conveyor, and hence the "wheel" itself, would be 4 freely rotatable (ie "idling" or "freewheeling") and the path of the roller type conveyor need extend around 6 the periphery of the circular supporting structure only 7 through substantially 2700 plus an additional angle to 8 accommodate any desired variability of the pipeline 9 launch angle, rather than through the full 360' of the circular structure. In the case where the pipeline 11 supporting structure comprises an endless belt conveyor 12 or the rim of a rotatable wheel, the belt conveyor or 13 wheel may either be driven (for example, by one or more 14 drive sprockets, not shown) or freely rotatable, depending upon the pipeline tensioning arrangements 16 which are to be employed (as shall be discussed further 17 below). This is also the case where the pipeline 18 diverter is provided by apparatus in accordance with 19 the present invention.

21 In the case of the roller or endless belt conveyor, or 22 apparatus in accordance with the present invention, it 23 will be understood that the pipeline path need not be 24 circular, and may have a varying curvature. For example, the radius of curvature of the pipeline path 26 might increase between the pipeline inlet end and the 27 pipeline outlet end of the pipeline path. The term 28 "wheel" is used for convenience in the present 29 discussion, but will be understood to embrace these possible variations of curved pipeline diverter 31 structures.

32 33 It will be noted that in the embodiments of Figs. 1 and 34 3 to 6, the diversion of the pipeline between the horizontal and the final launch angle is always in the WO 96/30686 PCT/GB96/00638 17 1 same direction, although the degree of curvature may 2 vary along the pipeline path.

3 4 As in Fig. 1, the pipeline 102 is assembled on the deck of the vessel, as shall be described further below, 6 passes around the wheel 104 and crosses itself prior to 7 launch. As seen in Fig. 6, the plane of the wheel 104 8 is disposed at a slight angle to the vertical plane 9 including the centreline of the vessel to allow the pipe to cross itself, as discussed above in relation to 11 Fig. i. Again, as indicated above, the use of the 12 present invention allows a helicoidal pipeline path to 13 be defined, obviating the need for the wheel to be 14 disposed at an angle.

16 In this example the pipeline is launched through a 17 moonpool 106 adjacent the stern of the vessel, rather 18 than from the side of the vessel as in Fig. 1.

19 Alternatively, the moonpool 106 might be extended to the stern of the vessel so that the pipeline is 21 effectively launched through a slot formed in the 22 stern. As indicated above, similar arrangements might 23 be employed with the pipeline diverter structure 24 located at the bow of the vessel.

26 The wheel 104 might be approximately 60 metres in 27 diameter, the overall vessel length being approximately 28 300 metres with a beam of approximately 42 metres. A 29 metre diameter wheel allows the laying of rigid steel pipe up to about 30 inches (762 mm) outside diameter.

31 In this example, the rearward rim of the wheel 104 is 32 cantilevered over the stern of the vessel, allowing the 33 pipelaying mechanism also to be used as a heavy lift 34 mechanism. The vessel may also be equipped with a conventional pipelay stinger 108 extending from the WO 96/30686 PCT/GB96100638 18 1 stern, allowing conventional "S-lay" pipelaying 2 independent of the wheel 104. This would be suitable 3 for operations in shallow waters.

4 The pipeline 102 to be laid by the vessel is assembled 6 from individual "joints" of pipe to form "stalks", 7 typically 12 joints in length. The stalks are welded 8 together prior to being passed around the wheel 104.

9 The deck space of the vessel is utilised to ensure that the pipe stalks are assembled and tie-in welds 11 connecting the stalks together are completed at a rate 12 which does not impede the pipelaying operation of the 13 vessel.

14 The length of the vessel is sufficient to accommodate 16 two assembled stalks laid end to end. As seen in Fig.

17 9, a first assembled stalk 110 extends along the 18 centreline of the vessel from the bow of the vessel to 19 a first weld station 112. A second assembled stalk 114 extends along the centreline of the vessel from the 21 first weld station 112 to a second weld station 116, 22 adjacent the wheel 104. The stalks 110, 114 are 23 supported and aligned by a plurality of adjustable 24 shoes 118 disposed along the length of the deck. The forward end of the first pipe stalk 110 is supported by 26 an extension 119 of the deck projecting forwards from 27 the bow of the vessel.

28 29 The stalks are fabricated from individual pipe joints in first and second stalk fabrication lines 120, 122 31 extending along either side of the sternward half of 32 the vessel parallel to the second stalk 116. Assembled 33 stalks are transported forward to first and second 34 repair lines 124, 126, extending along either side of the forward half of the vessel, parallel to the first WO 96/30686 PCT/GB96/00638 19 1 pipe stalk 110, where faults are identified and made 2 good by mobile repair stations 128, 130 adapted to 3 travel backwards and forwards along the lengths of the 4 repair lines 124, 126. From the repair lines 124, 126, the stalks are moved inwardly to first and second 6 storage areas 132, 134 between the repair lines 124, 7 126 and the first stalk 110, where a plurality of 8 assembled stalks may be stored prior to being 9 transported to the main, central "firing line" when required.

11 12 In operation of the vessel, a supply of stalks would be 13 fabricated and stored in areas 132, 134 prior to 14 commencement of pipelaying. Pipelaying would commence by an initial stalk being loaded into the forward 16 section of the firing line (the position occupied by 17 the first stalk 110 in the Fig. transported 18 sternwards to the position occupied by the second stalk 19 114 and then pulled around the wheel 104 by an initiation cable (as is known generally in the art), 21 until its forward end reaches the second weld station 22 116. This initial stalk is then clamped by means of a 23 clamping mechanism 136 disposed between the second weld 24 station 116 and the wheel 104.

26 The next stalk would then be loaded into the forward 27 section of the firing line and moved sternwards until 28 its leading end reaches the second weld station 116 and 29 its trailing end is aligned with the first weld station 112. A further stalk is then loaded into the forward 31 section of the firing line with its leading end at the 32 first weld station. Tie-in welds can then be made 33 simultaneously between the initial stalk and the next 34 stalk at the second weld station 116 and between the next stalk and the further stalk at the first weld WO 96/30686 PCT/GB96/00638 1 station 112. Non-destructive testing (NDT) and field- 2 coating of the tie-in welds are also carried out at the 3 weld stations 112, 116. Once welding, testing and 4 coating are complete, the initial stalk can be unclamped and the assembled pipeline fed around the 6 wheel 104. As soon as the pipeline clears the forward 7 section of firing line, another stalk can be loaded and 8 transported forward behind the welded pipeline, 9 whereafter a further stalk may be loaded into the forward section of the firing line.

11 12 Once the trailing end of the welded pipeline reaches 13 the second weld station, the pipeline is clamped as 14 before and welding of the next two stalks may commence.

Simultaneously, new stalks are being assembled in the 16 fabrication lines 120, 122 and tested/repaired in the 17 repair lines 124, 126, to replace those which have been 18 loaded from storage into the firing line. This process 19 is repeated in cyclical fashion throughout the pipelaying operation.

21 22 Stocks of pipe joints for the fabrication lines 120, 23 122 are stored in racks 138 between the firing line and 24 the fabrication lines 120, 122. Additional stocks 140 are held below deck, accessed by hatches 142. In 26 practice, the vessel would be continuously supplied 27 with pipe by support vessels so that the pipe required 28 for fabrication would normally always be supplied from 29 the deck racks 138, the below-deck stocks 140 being held in reserve in case of interruptions in supply.

31 32 First and second cranes 144, 146 are mounted on a first 33 travelling gantry 148, which straddles the fabrication 34 lines 120, 122, for loading pipe onto the vessel from port and starboard. A further utility crane 150 is WO 96/30686 PCT/GB96/00638 21 1 mounted on a second travelling gantry 152 which 2 straddles the repair lines 124, 126. An accommodation 3 block 154 for personnel also straddles the repair lines 4 124, 126 at the bow of the vessel, and supports a helicopter landing deck 156.

6 7 The vessel is propelled and dynamically positioned by 8 variable azimuth thrusters 158.

9 The pipeline diverting mechanism will now be described 11 in greater detail, with reference to Figs. 5 and 6 of 12 the drawings.

13 14 Figs. 5 and 6 show one example of pipeline diverting apparatus including clamping, aligning and 16 straightening apparatus associated with the diverter 17 wheel 104 of Figs. 3 and 4, and an arrangement for 18 varying the launch angle of the pipeline. As seen in 19 the drawings, the pipeline 102 emerges from the second weld station 116, incorporating NDT/coating station 21 160, and passes through the clamp 136. The pipeline 102 22 must thereafter be bent in a horizontal plane for 23 alignment with the rim of the wheel 104, which is set 24 at an angle to the vessel centreline as previously described, before being deflected upwardly in a 26 vertical plane to engage the rim of the wheel.

27 28 The horizontal alignment apparatus comprises first, 29 second and third roller track assemblies 162, 164, 166 of a type generally known from existing pipeline 31 straightening and tensioning apparatus. The first, 32 forward section aligner 162 is positioned immediately 33 aft of the clamp 136 on the same side of the pipeline 34 102 as the forward edge of the wheel 104. The second, mid-section aligner 164 is located aft of the first WO 96/30686 PCT/GB96/00638 22 1 aligner 162 on the opposite side of the pipeline 102 2 from the first aligner 162. The pipe-engaging surface 3 of the second aligner 164 is profiled to define the 4 curvature required to bend the pipeline 102 into alignment with the wheel rim. The third, aft section 6 aligner 166 is located aft of the second aligner 164 on 7 the same side of the pipeline as the first aligner 162.

8 The second aligner 164 is relatively longer than the 9 first and third aligners 162, 166, which provide reaction points for the pipeline to be bent to the 11 curvature of the second aligner 164. It is desirable 12 for the horizontal alignment of the pipeline 102 to be 13 performed prior to any vertical deflection thereof.

14 The vertical deflection apparatus comprises first and 16 second roller track assemblies 168, 170 located below 17 the pipeline 102. The first deflector 168 is 18 substantially horizontal and may be positioned adjacent 19 the third aligner 166. The second deflector 170 is inclined slightly upwards in the direction of pipeline 21 travel and deflects the pipeline 102 upwardly to engage 22 the wheel rim.

23 24 After passing around the wheel 104, the pipeline 102 must, in general, be at least partially straightened 26 before being launched from the vessel. In this example, 27 pipeline straightening is performed by first and second 28 straightener shoes 172, 174, which comprise further 29 roller track assemblies. The first straightener shoe 172 is located on the opposite side of the pipeline 102 31 from the wheel rim, downstream from the point where the 32 pipeline 102 leaves the wheel rim in the direction of 33 pipeline travel. The second straightener shoe 174 is 34 located on the opposite side of the pipeline 102 from the first shoe 172, downstream thereof. The two WO 96/30686 PCT/GB9600638 23 1 straightener shoes 172, 174 together with the wheel rim 2 itself define a three-point straightening mechanism of 3 a type which is generally well known in the art. This 4 straightening mechanism straightens the plastic bending of the pipeline in the vertical plane induced by the 6 passage of the pipeline around the wheel 104. Any 7 horizontal plastic bending induced by the aligners 162, 8 164, 166 is removed by the tension on the pipeline 102 9 as it passes around the wheel 104.

11 After being straightened, the pipeline 102 passes 12 through an anode application and welding station 177 13 and a primary clamp/pipe guide 178 before entering the 14 water. In this example, the primary clamp/pipe guide 178 is gimbal-mounted between a pair of guide rails 180 16 located on the port and starboard sides of the moonpool 17 106. The pipeline launch angle is variable by moving 18 the primary clamp/pipe guide 178 fore and aft along the 19 guide rails 180.

21 When the pipeline launch angle is varied from 90', the 22 point at which the pipeline 102 departs from the wheel 23 rim moves farther round the circumference of the wheel 24 rim (ie the pipeline is diverted through more than 2700). Accordingly, the straightener shoes 172, 174 must 26 also be moved as shown. For this purpose, the 27 straightener shoes 172, 174 may suitably be mounted on 28 a carriage (not shown) adapted to travel around the 29 wheel rim. This is easier to accomplish in a static structure having a peripheral roller or endless belt 31 conveyor, or comprising apparatus in accordance with 32 the present invention, than it would be in a wheel 33 which rotates about a central hub.

34 The degree of possible variation in the pipeline launch WO 96/30686 PCT/GB96/00638 24 1 angle depends upon the extent to which the wheel 104 is 2 angled relative to the vessel centreline. The shallower 3 the launch angle, the greater becomes the required 4 angle between the plane of the wheel 104 and the vertical plane through the vessel centreline, in order 6 to allow the pipeline to cross itself without clashing.

7 A 60 to 100 wheel offset angle is contemplated, allowing 8 the pipeline launch angle to be varied in a range of 9 the order of 900 to 50'. This corresponds to the pipeline being diverted through an angle in the range 11 270' to 3100 for a stern-launching vessel as 12 illustrated, or 2700 to 2300 for a bow-launching vessel.

13 14 Where the pipeline path is helicoidal, the path itself displaces the pipeline horizontally so that the 16 upstream end of the pipeline path may be colinear with 17 the horizontal pipeline assembly axis.

18 19 The vessel also includes apparatus for "abandonment and recovery" of the pipeline 102, which is not 21 illustrated in the present example. This might 22 typically include a carousel located below deck for 23 storage of an A&R cable, which can be passed around the 24 wheel 104 for connection to a free end of the pipeline 102 during A&R operations, and an A&R winch for 26 driving the A&R cable. For large diameter pipelines and 27 high pipeline tensions involved in the type of 28 operations for which the present vessel is particularly 29 intended, the A&R cable might itself comprise a flexible pipeline of known type. The pipeline diverter 31 apparatus may itself function as the A&R winch, the 32 apparatus in accordance with the present invention 33 being particularly well suited for this purpose.

34 When "abandoning" the pipeline 102, it would be clamped WO 96/30686 PCT/GB9600638 1 by the primary clamp 178 and cut at a point immediately 2 above the primary clamp 178. The A&R cable would then 3 be connected to clamped end of the pipeline, which may 4 then be unclamped and lowered into the water as required. During recovery operations, the free end of a 6 previously abandoned pipeline would be connected to the 7 A&R cable and pulled up to be clamped by the primary 8 clamp 178, where it would be re-welded to the end of a 9 pipeline passing around the wheel 104 and through the straightener 172, 174, at the welding station 177.

11 12 The wheel 104 may preferably include a second arcuate 13 path (not shown) for passage of the A&R cable alongside 14 the pipeline 102, allowing the pipeline to remain in situ on the wheel during A&R operations. Alternatively, 16 the wheel may include an arrangement of supporting 17 hooks or the like, into which the pipeline might be 18 sprung to allow passage of the A&R cable along the 19 existing pipeline path. Such an arrangement is described in more detail below.

21 22 The pipeline tension required for pipelaying operations 23 can be applied in a number of different ways. The 24 tension may be considered in terms of "back tension"; that is, the tension applied to the horizontal pipeline 26 before it engages the wheel 104; and "lay tension"; 27 that is, the tension in the pipeline as it departs from 28 the wheel 104. The lay tension must be maintained at or 29 above a predetermined value to maintain the bending radius of the pipe in the "sag bend region" prior to 31 touch down at or above the minimum value required to 32 prevent yielding of the pipeline.

33 34 If the wheel 104 is allowed to idle or "free-wheel", then the full lay tension may be provided by the back WO 96/30686 PCT/GB96/00638 26 1 tension applied to the horizontal pipe, or by a 2 tensioning mechanism applied to the pipeline after it 3 departs from the wheel. Alternatively, the full lay 4 tension could be applied by a braking force applied to the wheel 104. In practice, it is likely to be 6 desirable to exploit the "capstan effect" created by 7 the passage of the pipeline around the curved pipeline 8 supporting surface of the wheel 104, for which purpose 9 the wheel would have to be driven (or the pipeline braked by other means) and some degree of back tension 11 would always be required. This "capstan effect" could 12 be enhanced by passing the pipeline through multiple 13 turns about the wheel 104 (ie through 630' or more), 14 although this would entail significantly greater mechanical complexity. Combinations of any or all of 16 these alternatives are possible.

17 18 Tension may be applied to the pipeline before or after 19 the wheel 104 by any suitable means such as combinations of static and moving clamps as previously 21 discussed in relation to Fig. i, or caterpillar-track 22 type tensioners ("roller track assemblies") of a type 23 which are generally well known in the art. The use of a 24 tensioning mechanism upstream of the second weld station 116 in the direction of pipeline travel is 26 desirable, since this may also be employed in S-lay 27 operations using the conventional stinger 108.

28 29 The pipelay vessels described herein are also suitable for the laying of flexible pipelines and small diameter 31 pipelines which may be diverted through the various 32 embodiments of arcuate paths without plastic 33 deformation. In the case of Figs. 1 and 3 to 6, the 34 curvature imparted by the diverter wheels would match the direction of curvature of the required catenary.

WO 96/30686 PCT/GB9600638 27 1 Embodiments of apparatus in accordance with the present 2 invention will now be described with reference to Figs.

3 7 to 13. These embodiments will be described with 4 particular reference to their use in marine pipelaying vessels of the type described above in relation to 6 Figs. 1 to 6. However, it will be understood that the 7 apparatus may also find application in the handling of 8 other types of elongate members, such as flexible 9 pipelines, cables and ropes.

11 Referring now to Fig. 7, a pipeline diverter structure 12 suitable for use on the vessels of Figs. 1 to 6 13 comprises a structure 200 upon which are mounted a 14 plurality of roller track assemblies 202, 204, 206, 208 arranged end to end in series such that their outwardly 16 facing surfaces define a curved pipeline path. In this 17 example, the path is generally part-circular, at least 18 when viewed from the side. Each of the roller track 19 assemblies comprises an endless belt, track or chain 209 extending around a chassis 210 having end sprockets 21 212, 214, as is well known in the art. A series of 22 supporting rollers (not shown) are provided between the 23 end sprockets 212, 214 to support the belt 209 and to 24 define the profile of its outwardly facing, pipesupporting surface. The pipe-supporting surface of the 26 belt 209 is provided by a series of pads secured to the 27 belt, as is generally well known in the art and as 28 shall be described in greater detail below. The 29 pipeline is designated by the numeral 216.

31 The path defined by the roller track assemblies may 32 have a substantially constant radius of curvature or 33 the radius of curvature may vary along the length of 34 the path. If the path lies in a single plane, as with the rim of a wheel, then in use of the apparatus as a WO 96/30686 PCT/GB96/00638 28 1 pipeline diverter on board a vessel as shown in Figs. 1 2 to 6, the plane of the pipeline path would have to be 3 set at an angle to the vertical plane including the 4 horizontal pipeline axis, and horizontal diverter means would be required to divert the pipeline into alignment 6 with the path, as in Figs. 5 and 6.

7 8 However, if the apparatus is configured to define a 9 helicoidal path, then the path may initially be colinear with the pipeline axis and the helicoidal path 11 will shift the pipeline sideways allowing it to cross 12 itself upon exiting the apparatus. This is illustrated 13 in Fig. 8, which shows a plan view of the path taken by 14 a pipeline 218 around a diverter such as that shown in Fig. 7. A first portion 218a of the pipeline extends 16 from an assembly line and is bent upwardly through 900 17 around the lower arc of the pipeline path; a second 18 portion 218b is bent through a further 1800 about the 19 upper arc of the path and simultaneously shifted sideways by the helicoidal pitch of the path; and a 21 final portion 218c is bent through a further angle (if 22 required) to its final launch angle, extending 23 substantially parallel to said first portion 218a when 24 viewed from above. In this example the pipeline 218 is launched via a moonpool 220, located between first and 26 second stalk fabrication lines 222, 224, as in Fig. 4.

27 28 If all of the roller track assemblies are idle, then 29 the apparatus serves simply as a guide to divert the pipeline, and any required tension must be applied by 31 other means upstream and/or downstream of the 32 apparatus. In preferred embodiments, some or all of the 33 roller track assemblies are driven so that the 34 apparatus provides at least a proportion of the required tension. Most preferably, a degree of back WO 96/30686 PCT/GB96/00638 29 1 tension is provided by tensioning means upstream of the 2 apparatus in the direction of pipeline travel, enabling 3 the "capstan effect" of the apparatus to be exploited.

4 Where tension is applied by the apparatus, such tension 6 may be applied simply by friction between the pipeline 7 and the pipeline supporting pads of the belts of the 8 driven roller track assemblies, or one or more of the 9 roller track assemblies may comprise tensioners having second roller track assemblies disposed on the opposite 11 side of the pipeline, such as assemblies 226 disposed 12 opposite assemblies 206, 208 in Fig. 7. In this case 13 one or both of the inner assemblies 206, 208 and outer 14 assemblies 226 would be mounted to be movable in the radial direction to apply tensioning forces to the 16 pipeline. The other roller track assemblies 202, 204 17 may also be adjustable in the radial direction, if 18 required.

19 In general, the tension on the pipeline will be lowest 21 on entering the apparatus and highest at the point of 22 departure from the apparatus. In the example of Fig. 7, 23 each roller track assembly is driven, and each 24 contributes to the tension applied to the pipeline. In this example, the last six roller track assemblies 202 26 are configured such that each contributes a first, 27 substantially equal tensile force (eg 180 tonnes each), 28 the four assemblies 204 upstream of the last six are 29 configured such that each contributes a second, substantially equal tensile force (eg 120 tonnes each), 31 and the two tensioner assemblies 206, 208, 226 are 32 configured such that each contributes a third, 33 substantially equal tensile force (eg 320 tonnes each).

34 In the absence of external, opposed roller track WO 96/30686 PCT/GB96/00638 1 assemblies, the tension contributed by each of the 2 roller track assemblies 202, 204 is a function of the 3 friction between the belts 209 of the assemblies and 4 the pipeline 216. The friction in turn is proportional to the tension in the pipeline and the angle subtended 6 by the assemblies (ie the length of the assemblies).

7 Accordingly, the lengths of the assemblies 202, 204 8 vary around the pipeline path, decreasing progressively 9 in the direction of travel of the pipeline.

11 The pipeline supporting surfaces of the roller track 12 assemblies have an arcuate, longitudinal profile, the 13 radius of curvature thereof preferably being slightly 14 smaller than the corresponding radius of the pipeline path as such; eg the radius of curvature of the 16 assemblies might be 29.5 metres for a path radius of 17 metres.

18 19 Fig. 9 shows a further example of a pipeline diverter structure embodying the invention, in which the series 21 of roller track assemblies 228 are mounted on a 22 structure 230, which is in turn supported by a 23 framework 232 mounted on a truss 234. In this case, 24 every second roller track assembly 228 in the first 2700 of the pipeline path has a corresponding external, 26 opposed roller track assembly 236, and additional 27 assemblies 238 extend the path beyond 2700 to provide 28 additional support for the pipeline 240 when the 29 pipeline launch angle is less than 900. The pipeline path may lie in a single plane or may be helicoidal.

31 The drawing also shows a gimbal-mounted clamping 32 assembly 242, similar to that of Fig. 5. In this case a 33 three-roll straightener assembly 244 is mounted on the 34 clamp assembly 242, rather than on the diverter structure itself as in Fig. 5. This straightener WO 96/30686 PCT/GB96/00638 31 1 arrangement may also be employed with the other types 2 of diverters described herein, as may the arrangement 3 of the framework 232 and truss 234.

4 Fig. 14 shows a further, preferred example of a 6 pipeline diverter structure embodying the invention. In 7 this case there are no external tensioner assemblies.

8 Otherwise the arrangement is broadly similar to that of 9 Fig. 7, with a first set of seven roller track assemblies 246 each contributing a first tensile force, 11 a second set of two roller track assemblies 248 each 12 contributing a second tensile force, less than the 13 first tensile force, and a third set of two roller 14 track assemblies 250 each contributing a third tensile force, less than the second tensile force. Fig. 15 is 16 an end view illustrating the helicoidal path of the 17 pipeline 252. A similar arrangement of roller track 18 assemblies might also be used to define a pipeline path 19 lying in a single plane.

21 Figs. 10 to 13 show arrangements of pipeline support 22 pads suitable for use with endless belts of the roller 23 track assemblies of pipeline diverter apparatus in 24 accordance with the invention, including the embodiments of Figs. 7, 9 and 14. These examples are 26 all configured to accommodate one or more A&R cables in 27 addition to or in place of the pipeline.

28 29 In Figs. 10(a) and 10(b), the support pad 254 is mounted on the chain or belt 256 of the roller track 31 assembly, and has a transverse, sectional profile 32 including a central groove 258 which is generally part 33 circular in cross-section to accommodate the pipeline 34 260. The lowermost part of the groove 258 includes a Vshaped notch 262 which may accommodate an A&R cable WO 96/30686 PCT/GB96/00638 32 1 264. The V-shaped configuration allows cables of 2 different diameters to be seated, as indicated in the 3 drawing by a smaller diameter cable 266. Additional 4 grooves 268, 270 on either side of the central groove 258 may accommodate additional cables 272, 274. This 6 example also shows the use of "diabolo" type rollers 7 276 of an external, opposed tensioner assembly bearing 8 on the outer surface of the pipeline 260.

9 Figs. 11(a) and 11(b) show a second example in which 11 the pad 278 again has a main, part-circular groove 280 12 to accommodate the pipeline 260, with additional part- 13 circular grooves 284, 286, 288 formed in the main 14 groove 280 to accommodate either a pair of cables 290 of equal diameter or a single, smaller diameter cable 16 292. The belt and diabolo rollers are again designated 17 by numerals 256 and 276 respectively.

18 19 Figs. 12(a) and 12(b) show an arrangement similar to that of Fig. 10, and like parts are designated by like 21 numerals. In this case the diabolo rollers 276 of Fig.

22 10 are replaced by an endless belt 294 of an external, 23 opposed tensioner, which itself has pipeline contacting 24 pads 296 secured thereto (omitted from the side view of Fig. Figs. 13(a) and 13(b) correspond to Fig.

26 11 in the same way that Fig. 12 relates to Fig. 27 28 The pads 254, 278 may typically be about 300 mm in 29 length. Where the lengths of the roller track assemblies vary around the pipeline path, it is 31 preferred that the lengths of individual roller track 32 assemblies are selected so as to allow standard pad 33 sizes to be used.

34 Figs. 16(a) illustrate procedures for feeding a WO 96/30686 PCT/GB96/00638 33 1 pipeline around a diverter structure and for 2 subsequently "springing" the pipeline out of its normal 3 path to allow the deployment of an A&R cable, or the 4 like, without the need for completely removing the pipeline from the diverter structure. It is 6 particularly preferred that these procedures be 7 employed with a structure such as that illustrated in 8 Figs. 14 and 15, employing multiple roller track 9 assemblies to define a helicoidal path, but they are also applicable to other types of arcuate diverter 11 structures as described herein. The following 12 description assumes a helicoidal pipeline path. A 13 planar path would also require horizontal diversion of 14 the pipeline as it engages the diverter structure, as previously described.

16 17 In Figs. 16(a) the pipeline is designated by 18 reference numeral 300, the roller track assemblies 19 defining the arcuate pipeline path by numeral 302, first and second straightener tracks by numerals 304, 21 306, an initial roller track assembly for diverting the 22 pipeline vertically into engagement with the pipeline 23 path by numeral 308, and a main pipeline clamp by 24 numeral 310. All of these parts correspond to features of previously described embodiments. Figs. 16(a) (f) 26 also show an initiation cable 312, a pre-bent pipe 27 joint 314 and a plurality of "hooks" 316 disposed 28 around the pipeline path. The initiation cable 312 29 passes around the pipeline path, between the straightener tracks 304, 306 and around a sheave 318 to 31 a suitable winch (not shown).

32 33 At the commencement of pipelaying operations, the 34 pipeline 300 is established onto the diverter structure as follows.

WO 96/30686 PCT/B96/00638 34 1 As seen in Fig. 16(a), a pipe joint (typically 12m in 2 length) which has been pre-bent substantially to the 3 curvature of the pipeline path is welded to the 4 downstream end of a first pipestalk 300a. The initiation cable 312 (in this example, a 76mm wire) is 6 passed around the diverter structure and secured to the 7 downstream end of the pre-bent pipe joint 314, which is 8 located slightly upstream of the initial roller track 9 308. The pre-bent pipe joint 314 is shown in Fig.

16(a) with its plane of curvature perpendicular to the 11 deck of the vessel.

12 13 In order to bring the pre-bent pipe joint 314 into 14 initial engagement with first of the diverter track assemblies 302, the first pipestalk 300a is rotated 16 through 900 about its longitudinal axis so that the 17 plane of curvature of the pre-bent joint 314 is 18 parallel to the deck of the vessel, and the pipeline 19 300 is pulled in the downstream direction until the pre-bent joint 314 lies below the first diverter track 21 302, as indicated by the dashed lines in Fig. 16(b).

22 The pipestalk 300a is then rotated back to its original 23 orientation, such that the plane of curvature of the 24 pre-bent pipe joint 314 is again perpendicular to the deck and engages the surface of the first diverter 26 track 302, as also shown in Fig. 16(b). A second 27 pipestalk 300b is then fed along the firing line and 28 welded to the upstream end of the first pipestalk 300a.

29 The first stalk 300a is preferably relatively shorter than subsequent stalks in order to facilitate the 31 rotation described above.

32 33 The pipeline 300 is then pulled around the diverter 34 structure until the pre-bent joint 314 reaches the straightener rolls 304, 306, which are opened as shown WO 96/30686 PCT/GB96/00638 1 in Fig. 16(c) such that the pre-bent joint may pass 2 therebetween without yielding. With the straightener 3 rolls 304, 306 open, the pipeline 300 is pulled through 4 until its downstream end clears the downstream end of the second straightener roll 306, and the straightener 6 rolls 304, 306 are closed on the pipeline as shown in 7 Fig. 16(d). At this point the initiation cable 312 is 8 detached and the pre-bent pipe joint 314 is cut off the 9 downstream end of the pipeline 300 for subsequent reuse. Thereafter, pipelaying proper may commence, with 11 the pipeline 300 typically being guided to its starting 12 point on the seabed by means of a further initiation 13 cable and winch (not shown) as is well known in the 14 art.

16 During the course of pipelaying it may be necessary, 17 from time to time, to "abandon" the pipeline and 18 subsequently to "recover" the abandoned end of the 19 pipeline in order to resume pipelaying. Such abandonment and recovery procedures are well 21 known in the art, and involve attaching an A&R cable to 22 the upstream end of the pipeline, which is then lowered 23 to the seabed and marked by a buoy for subsequent 24 recovery, again using the A&R cable. In use of the pipelaying system as described herein, it is desirable 26 to utilise the pipe diverter structure as an A&R 27 capstan, with the A&R cable passing around the diverter 28 structure. It is also desirable to cut the pipe for 29 abandonment purposes immediately above the main pipeline clamp 310. Figs. 16(e) and 16(f) illustrate 31 a procedure allowing this to be accomplished without 32 having to withdraw the pipeline 300 upstream of the 33 main clamp 310 from the diverter structure.

34 In accordance with this procedure, the first WO 96/30686 PCT/GB96/00638 36 1 straightener track 304 is braked and the pipeline 300 2 is clamped thereto by any suitable means 320. The main 3 clamp 310 is also activated to clamp the pipeline 4 downstream of the straightener. The pipeline 300 may then be cut between the second straightener roll 306 6 and the main clamp 310. The pipeline 300c passing 7 around the diverter structure is then displaced 8 radially outwards from the pipeline path around the 9 diverter by relaxing the back tension on the pipeline and/or feeding the pipe towards its clamped end at the 11 first straightener roll 304, such that the pipeline 12 300c "springs" outwards from the path. The 13 straightener rolls 304, 306 may be opened to facilitate 14 this. The outward movement of the pipeline 300c is restrained by the hooks 316, which are mounted around 16 the pipeline path, spaced outwardly from the roller 17 track assemblies 316 to allow the pipeline 300c to 18 spring outwards by an appropriate distance (suitably 19 21 Once the pipeline 300c has been displaced from its 22 normal path, the A&R cable 322 may be passed around the 23 diverter structure along the pipeline path and secured 24 to the upstream end of the pipeline 300d held in the main clamp 310 as seen in Fig. 16(f). The initial 26 roller track assembly 308 may be lowered for this 27 purpose, if necessary. The A&R cable 322 may then be 28 deployed to lower the pipeline 300d to the seabed.

29 Subsequent recovery of the pipeline involves the 31 reversal of this procedure, with the abandoned pipe 32 300d being pulled back up from the seabed and held in 33 the main clamp 310. The A&R cable 322 is then 34 withdrawn from the diverter structure, back tension applied to the pipeline 300c extending around the P:\OPER\KAT\51143 96.339 7/12/98 -37diverter structure to re-seat it on the roller track assemblies 302, and the downstream end of the pipeline 300c re-welded to the upstream end of the recovered pipeline 300d. Pipelaying operations may then be resumed.

Whilst the invention has been described particularly in relation to diverter structures for laying rigid marine pipelines in which the pipeline is diverted through an angle greater than 180° so as to cross over itself prior to entering the water, it will be appreciated that the invention may equally be applied to diverter structures for rigid pipelines in which the pipeline path defined by the apparatus has a different configuration. As previously indicated, the invention may also be applied as a diverter and/or tensioner for flexible pipelines, ropes, cables, etc., or as a type of winch.

Modifications may be made to the foregoing embodiments within the scope of the present invention.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

S

*ooo

Claims (8)

1. 7. Apparatus as claimed in any preceding Claim, 1 wherein each of said roller track assemblies has an 2 outwardly facing, bearing surface. 3 4 8. Apparatus as claimed in Claim 7, wherein said bearing surface is arcuate in longitudinal profile. 6 7 9. Apparatus as claimed in Claim 8, wherein the 8 radius of curvature of said arcuate profile is less 9 than the corresponding radius of curvature of said substantially arcuate path. 11 12 10. Apparatus as claimed in any preceding Claim, 13 wherein at least one of said roller track assemblies 14 includes drive means such that said at least one assembly which includes drive means is adapted to apply 16 tension to said elongate member. 17 18 11. Apparatus as claimed in Claim 10, wherein said at 19 least one assembly which includes drive means has associated therewith a further, driven roller track 21 assembly disposed on the opposite side of said 22 substantially arcuate path therefrom, one or other or 23 both of said driven assembly and said further driven 24 assembly being movable towards and away from the other .oooo= 25 so as to apply a compressive force to said elongate 26 member. S 27 28 12. Apparatus as claimed in any preceding Claim, 29 wherein the longitudinal lengths of the roller track 30 assemblies vary along the length of the path. S 31 32 13. Apparatus as claimed in Claim 12, wherein the 33 longitudinal lengths of the roller track assemblies 34 decrease in the direction of travel of the elongate member. 1 14. Apparatus as claimed in any preceding Claim, 2 wherein said arcuate path is configured to divert said 3 elongate member through a net angle greater than 1800. 4
2. 15. Apparatus as claimed in Claim 14, wherein said 6 arcuate path is configured to divert said elongate 7 member through a net angle equal to or greater than 8 2700. 9
3. 16. Apparatus as claimed in any preceding Claim, 11 wherein each of said roller track assemblies includes 12 an endless belt having a series of pads secured to the 13 outer surface thereof for contacting said elongate 14 member. 16 17. Apparatus as claimed in Claim 16, wherein said 17 pads include a plurality of grooves adapted to 18 accommodate different types and sizes of elongate 19 members. 21 18. A marine pipelaying vessel including apparatus for 22 handling elongate members as claimed in any one of 23 Claims 1 to 17. 24
4. 19. A vessel as claimed in Claim 18, wherein said 26 vessel includes a deck area and means on the deck area 27 for aligning pipe sections along a substantially 28 horizontal axis and connecting said pipe sections 29 together to form a pipeline, and said apparatus is 30 adapted for bending the pipeline to cause it to pass 31 from said horizontal axis to a launch axis having a S32 substantial inclination to the horizontal. 9999 o 33 S34 20. A vessel as claimed in Claim 19, wherein said apparatus is adapted to plastically bend the pipeline 1 about a substantially arcuate path in a substantially 2 vertical plane. 3 4 21. A vessel as claimed in Claim 20, wherein the vessel further includes means for applying tension to 6 said pipeline, and means for controlling said tension 7 to ensure that the bending of the pipeline at the point 8 where it meets the sea bed is within the elastic yield 9 limit of the pipe material. 11 22. A vessel as claimed in Claim 21, further including 12 straightening means located downstream of said 13 apparatus for at least partially removing the bend in 14 the pipeline. 16 23. A vessel as claimed in any one of Claims 18 to 17 22, wherein said apparatus is adapted to bend said 18 pipeline upwardly along a substantially arcuate path 19 and subsequently to bend said pipeline downwardly to a final launch angle. 21 22 24. A vessel as claimed in Claim 23, further including 23 means for feeding the pipeline in a direction from the o. 24 bow of the vessel towards the stern thereof and said 25 apparatus is adapted to divert said pipeline through an 26 angle of substantially 2700 or greater. 27 28 25. A vessel as claimed in Claim 24, wherein said 29 apparatus is adapted to divert said pipeline through an angle no greater than 3100. 31 32 26. A vessel as claimed in Claim 24, wherein said 33 apparatus is adapted to divert the pipeline through at S: 34 least one complete turn. 1 27. A vessel as claimed in Claim 26, wherein said 2 apparatus is adapted to divert said pipeline through an 3 angle greater than or equal to 2700 plus an integer 4 multiple of 3600. 6 28. A vessel as claimed in Claim 27, wherein said 7 apparatus is adapted to divert said pipeline through an 8 angle no greater than 3100 plus said integer multiple of 9 3600. 11 29. A vessel as claimed in Claim 23, wherein said 12 vessel includes means for feeding the pipeline in a 13 direction from the stern of the vessel towards the bow 14 thereof and said apparatus is adapted to divert said pipeline through a net angle no greater than 270. 16 17 30. A vessel as claimed in Claim 29, wherein said 18 apparatus is adapted to divert said pipeline through an 19 angle not less than 2300. 21 31. A vessel as claimed in Claim 29, wherein said 22 apparatus is adapted to divert the pipeline through at 23 least one complete turn. 24 25 32. A vessel as claimed in Claim 31, wherein said 26 apparatus is adapted to divert said pipeline through an 27 angle no greater than 2700 plus an integer multiple of 28 360. 29 S 30 33. A vessel as claimed in Claim 32, wherein said 31 apparatus is adapted to divert said pipeline through an 32 angle, not less than 2300 plus said integer multiple of 33 360. 34
5. 34. A vessel as claimed in any one of Claims 23 to 33, 1 wherein said apparatus is adapted to launch said 2 pipeline from the side of the vessel or via a moon- 3 pool. 4
6. 35. A vessel as claimed in any one of Claims 24 to 28, 6 wherein said apparatus is adapted to launch said 7 pipeline over the stern of the vessel. 8 9 36. A vessel as claimed in any one of Claims 29 to 33, wherein said apparatus is adapted to launch said 11 pipeline over the bow of the vessel. 12 13 37. A vessel as claimed in any one of Claims 18 to 36, 14 further including means for varying the launch angle of the pipeline by varying the point at which the pipeline 16 departs from said substantially arcuate path, 17 straightening means for straightening said pipeline 18 after it departs from said substantially arcuate path, 19 and pipe guide means through which said pipeline passes after being straightened. 21 22 38. A vessel as claimed in Claim 37, wherein said pipe 23 guide means is adapted to be translated in a fore and 24 aft direction so as to vary the launch angle of the pipeline. 9 26 27 39. A vessel as claimed in any one of Claims 18 to 38, 28 further including tensioning means for applying tension 29 to the pipeline, located upstream of said apparatus in 30 the direction of pipeline travel. 31 32 40. A vessel as claimed in any one of Claims 18 to 39, S 33 further including tensioning means for applying tension 34 to the pipeline, located downstream of said apparatus in the direction of pipeline travel. 44 1 41. A vessel as claimed in any one of Claims 18 to 2 wherein said apparatus is adapted for applying a 3 braking force to said pipeline as it passes around said 4 substantially arcuate path. 6 42. A vessel as claimed in any of Claims 18 to 41, 7 wherein the plane of said substantially arcuate path 8 lies in a single plane, the plane of the path being 9 disposed at an angle to the vertical plane including the horizontal pipeline assembly axis, and the vessel 11 further includes alignment means for diverting the 12 pipeline in a horizontal plane into alignment with the 13 plane of said substantially arcuate path prior to the 14 pipeline engaging said substantially arcuate path. 16
7. 43. A vessel as claimed in Claim 42, wherein said 17 alignment means is adapted to effect said horizontal 18 diversion prior to said pipeline being diverted 19 upwardly to engage said substantially arcuate path. 21
8. 44. A vessel as claimed in any one of Claims 18 to 41, 22 wherein said substantially arcuate path is helicoidal, 23 such that the pipeline is diverted horizontally as it 24 passes around said path. S q 26 45. A vessel as claimed in Claim 44, wherein the 27 upstream end of the substantially arcuate path in the 28 direction of pipeline travel is substantially colinear 29 with the horizontal pipeline assembly axis. 31 46. A method of initiating pipelaying operations in a 32 marine pipelaying system in which a pipeline is passed 33 around an arcuate path, defined by apparatus as claimed 34 in any preceding Claim, in order to divert said pipeline to a desired launch angle, comprising the I 1 steps of securing a length of pipe which has been pre- 2 bent to a radius of curvature substantially equal to 3 the radius of curvature of said arcuate path to the 4 downstream end of a pipeline which is to be passed around said arcuate path, securing an initiation cable 6 to the downstream end of said pre-bent pipe length, 7 pulling said pipeline around said arcuate path by means 8 of said initiation cable, and detaching said initiation 9 cable and said pre-bent pipe length prior to commencing pipelay operations. 11 12 47. A method of interrupting pipelaying operations in 13 a marine pipelaying system in which a pipeline is 14 passed around an arcuate path, defined by apparatus as claimed in any one of Claims 1 to 45, in order to 16 divert said pipeline to a desired launch angle, 17 comprising the steps of stopping pipelaying operations, 18 clamping the pipeline at a first location where the 19 pipeline departs from said arcuate path, clamping the pipeline at a second location downstream of said first 21 location in the direction of pipeline movement, cutting 22 said pipeline at a location intermediate said first and 23 second locations, displacing the pipeline passing 24 around said arcuate path radially outwards from said 25 arcuate path, passing an abandonment and recovery (A&R) 926 cable around said arcuate path in the direction of 9 27 normal pipeline movement around said path, and securing 28 said A&R cable to the upstream end of the pipeline :9::99 29 clamped at said second location. _31 48. A method as claimed in Claim 47, wherein the 32 outward displacement of the pipeline passing around 33 said arcuate path is effected by relaxing the back 34 tension on said pipeline and/or by feeding said pipeline around said arcuate path. 46 1 49. A method as claimed in Claim 47 or Claim 48, 2 wherein the outward displacement of the pipeline is 3 restrained by restraining means mounted on a pipeline 4 diverter structure defining said arcuate path and located radially outwards from said arcuate path. 6 7 50. A method as claimed in any one of Claims 47 to 49, 8 wherein a straightener mechanism located adjacent the 9 point of departure of the pipeline from said arcuate path is utilised to clamp the pipeline at said first 11 location. 12 DATED this 7th day of December, 1998 COFLEXIP STENA OFFSHORE LIMITED By its Patent Attorneys Davies Collison Cave 0