This invention relates to apparatus for handling elongate members such as rigid and flexible pipelines, ropes or cables. The apparatus is of particular interest for use in the laying of rigid submarine pipelines, but may also be useful in laying flexible pipelines or as a winch for cables and ropes.

The invention relates to apparatus which, in its preferred embodiments, is suitable for diverting a pipeline about an arcuate path between an initial angle of orientation and a second angle of orientation. In a typical application of the invention, the apparatus might be used on a marine pipelaying vessel to divert a pipeline from an initial horizontal orientation to a final launch angle- at a substantial inclination to the horizontal. The diversion of the pipeline will generally involve plastic bending of the pipe, which in most cases would be followed by subsequent straightening, or at least partial straightening. However, the invention is also applicable in cases where the pipeline diversion involves elastic bending to a degree which does not exceed the yield limit of

the 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 180°, 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 an arcuate path around which said elongate members pass.

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

In accordance with a second aspect of the invention, there is provided apparatus for handling elongate members, comprising bearing means for supporting said elongate member, said bearing means defining a helicoidal, arcuate path around which said elongate members pass.

Preferably, said bearing means comprises a plurality of roller track assemblies mounted on a supporting structure and arranged in series to define said arcuate path.

The radius of curvature of the substantially arcuate

path may be substantially constant or may vary along the length of the path.

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

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

In preferred embodiments, the pipeline path is preferably configured to divert said elongate member through a net angle greater than 180°, and most preferably through a net angle equal to or greater than 270°.

Each of said roller track assemblies preferably includes an endless belt having a series of pads secured to the outer surface thereof for contacting said elongate member. In preferred embodiments, said

pads 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 third 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.

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

Preferably, a vessel in accordance with the third or fourth aspects 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 substantially arcuate path in a substantially vertical plane.

The vessel preferably further includes means for applying tension to said pipeline, and means for

controlling said tension to ensure that the bending of the pipeline at the point where it meets the sea bed is within the elastic yield limit of the pipe material.

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

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

In one such embodiment, means are provided for feeding the pipeline in a direction from the bow of the vessel towards the stern thereof and said apparatus is adapted to divert said pipeline through an angle of substantially 270° or greater, and typically less than or equal to 310°.

The pipeline may be diverted through one or more complete turns, in which case said apparatus is adapted to divert said pipeline through an angle greater than or equal to 270° plus an integer multiple of 360°, and typically less than or equal to 310° plus said integer multiple of 360°.

Alternatively, the vessel may include means for feeding the pipeline in a direction from the stern of the vessel towards the bow thereof and said apparatus is adapted to divert said pipeline through an angle of substantially 270° or less, and typically greater than or equal to 230°.

Again, the pipeline may be diverted through one or more

complete turns, in which case said apparatus is adapted to divert said pipeline through an angle less than or equal to 270° plus an integer multiple of 360°, and typically greater than or equal to 230° plus said integer multiple of 360°.

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

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

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

The plane of said substantially arcuate path may lie in a single plane, in which case the plane of the path is preferably disposed at an angle to the vertical plane including the horizontal pipeline assembly axis, and

the 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 fifth 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 commencing pipelay operations.

In accordance with a sixth 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

divert said pipeline to a desired launch angle, comprising the steps of stopping pipelaying operations, clamping the pipeline at a first location where the pipeline departs from said arcuate path, clamping the pipeline at a second location downstream of said first location in the direction of pipeline movement, cutting said pipeline at a location intermediate said first and second locations, displacing the pipeline passing around said arcuate path radially outwards from said arcuate path, passing an abandonment and recovery (A&R) cable around said arcuate path in the direction of normal pipeline movement around said path, and securing said A&R cable to the upstream end of the pipeline clamped at said second location.

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

In the present application, the term "roller track assembly" is used to designate an assembly of generally known type in which an endless conveyor belt or track or chain or the like is mounted around a supporting chassis including end sprockets (driven or idle) and support rollers, in the manner of a caterpillar track. Roller track assemblies of this general type have been used in apparatus for straightening rigid pipelines,

for tensioning pipelines, cables, ropes etc., and for aligning pipelines. A typical straightener employs three-point straightening as is well known in the art and is discussed in US Patents Nos.3,237,438 and 3,372,461. Examples of roller track assemblies and their use in pipeline straightening are described in US Patents Nos. 3,855,835, 4,157,023, 4,243,345 and 4,260,287. Alternative "roller-track" type assemblies are also described in US Patents Nos. 4,230,421, 4,269,540, 4,297,054., 4,340,322 and 4,345,855, and further in US Patents Nos. 3,641,778, 3,680,342, Re 30,846 and 4,723,874. In general, the roller track assemblies are arranged on opposite sides of the pipe, and means are provided for positioning the tracks to impart a reverse bending force.

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

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figs. 1(a) and 1(b) are, respectively schematic side and plan views of a marine pipelaying vessel of a type in which apparatus in accordance with the invention may be employed;

Fig. 2 is a schematic side view illustrating the pipeline catenary between the vessel and the seabed for the embodiment of Figs. 1(a)

and 1 ( b ) ;

Fig. 3 is a schematic side view of a more detailed embodiment of a vessel similar to that of Figs. 1 and 2;

Fig. 4 is a plan view of the embodiment of Fig. 3;

Fig. 5 is an enlarged, partial side view of a pipeline diverting and launching mechanism of the embodiment of Fig. 3;

Fig. 6 is a plan view of the mechanism of Fig. 5;

Fig. 7 is a schematic side view of an embodiment of apparatus for handling elongate members in accordance with the invention;

Fig. 8 is a schematic plan view of one variant of the apparatus of Fig. 7;

Fig. 9 is a schematic side view of a more detailed example of an embodiment of apparatus for handling elongate members, in accordance with the invention;

Figs. 10(a) and 10(b) are, respectively, a schematic, transverse sectional view and a schematic side view of a first example of pipeline bearing arrangements for use in the apparatus of Figs. 7 to 9;

Figs. 11(a) and 11(b) are, respectively, a

schematic, transverse sectional view and a schematic side view of a second example of pipeline bearing arrangements for use in the apparatus of Figs. 7 to 9;

Figs. 12(a) and 12(b) are, respectively, a schematic, transverse sectional view and a schematic side view of a third example of pipeline bearing arrangements for use in the apparatus of Figβ. 7 to 9;

Figs. 13(a) and 13(b) are, respectively, a schematic, transverse sectional view and a schematic side view of a fourth example of pipeline bearing arrangements for use in the apparatus of Figs. 7 to 9;

Fig. 14 is a schematic side view of a further embodiment of apparatus for handling elongate members in accordance with the invention;

Fig. 15 is a schematic end view illustrating the helicoidal path defined by the apparatus of Fig. 14: and

Figs. 16(a) - (f) are schematic side views of a pipe diverter structure illustrating methods of feeding a pipeline around an arcuate diverter structure and subsequently displacing the pipeline from the diverter structure to allow the passage of an abandonment and recovery cable, in accordance with further aspects of the invention.

Before describing detailed embodiments of apparatus for

handling elongate members in accordance with the invention, examples of pipelaying vessels to which the invention may be applied will be described briefly, by way of background.

Figs. 1(a) and 1(b) show an embodiment of a marine pipelaying vessel which is particularly suited to deepwater operations, and includes a sheave, wheel or equivalent structure 40 for diverting the pipeline 42 through substantially 270° or more from the horizontal so as to enter the water substantially vertically or at some required angle. The wheel 40 might have a diameter of approximately 50 metres and is rotatably mounted adjacent one side of the vessel 44 on a support structure 46. Apparatus in accordance with the present invention may be employed to provide the pipeline diverting structure 40.

Where the vessel is used for laying rigid pipeline which is plastically deformed whilst passing around the pipeline diverter structure 40, the support structure 46 may also support straightening means (not shown, suitably of any of a number of types known in the art) for straightening the pipeline 42 as it leaves the diverter structure 40, and abandonment and recovery (A&R) equipment (ie pipeline clamps and winches and the like), as is well known in the art. For very high pipeline tensions, A&R operations may involve the use of a drill string (rather than a cable), which may be deployed from a short derrick disposed above the pipeline departure point.

Since the pipeline leaving the diverter structure 40 must cross the horizontal path of the pipeline being fed onto the diverter structure, arrangements must be

made to allow the pipeline to cross itself without clashing.

If the pipeline path defined by the diverter structure lies in a single plane (as would be the case if the pipeline path extends around the rim of a circular wheel, for example) the plane of the diverter structure 40 is set at a slight angle to the vertical plane including the horizontal pipeline path, and the horizontal pipeline path is curved slightly as it approaches the wheel rim, as is best seen in Fig. 1(b). This horizontal diversion of the pipeline path to allow the pipe to cross itself is advantageously carried out at the entry of the pipe to the wheel rather than after its departure therefrom, since the required curvature of the pipe can be controlled using a horizontal track on the deck of the vessel, and the lower pipeline tension before feeding around the wheel allows tighter curvature.

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

This pipelaying vessel is suited to the application of high pipeline tensions, required for deepwater laying, without resort to expensive track-type tensioners, by means of: first and second fixed pipeline clamps (not shown) before and after the wheel 40 on the horizontal and vertical pipeline paths respectively; a horizontal moving clamp (not shown) located before the first fixed clamp, for lowering the pipeline joint by joint; and by

driving the wheel. With a correctly profiled wheel rim, the wheel can be made to transmit the full lay tension required. However, in practice a degree of back tension would always be maintained. Possible alternative strategies for applying the required tension will be discussed further below.

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

The pipeline path defined by the diverter structure 40 may comprise the rim of a wheel mounted for rotation about a central hub, or other means such as a static structure having rollers or an endless belt conveyor for supporting the pipeline as it is diverted through the required angle. Advantageously, the pipeline path may be defined by apparatus in accordance with the present invention, as shall be described further below.

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

The vessel of Figs. 3 to 6 includes a pipeline diverter structure generally designated by the reference numeral 100, mounted at the stern of the vessel. The structure 100 is adapted to divert the pipeline 102 about an arcuate path through an adjustable angle of substantially 270° or more, as in the embodiment of Fig. 1. This provides a pipeline launch angle which is

variable up to 90°. The arcuate pipeline path is defined by a curved structure 104 (circular in this example), which shall be referred to herein, for convenience, as a "wheel" .

As in the embodiment of Fig. 1, the wheel 104 might, for example, comprise a pipeline supporting conveyor extending around the peripheral rim of a static circular structure. The pipeline conveyor may comprise a series of idle rollers having their axes of rotation extending at right angles to the direction of pipeline travel. Alternatively, the conveyor might comprise a continuous, endless belt or chain type conveyor encircling the supporting structure. An endless belt conveyor of this type may be driven or may be idle. Pipeline conveyors of these types are known in the art, as used in the pipe bearing portions of straighteners, tensioners, aligners and stingers, and the like, and shall not be described in greater detail herein. It will be appreciated that, again, the pipeline diverter could also be implemented with a wheel which rotates about a central axis, as discussed above in relation to Fig. 1. Again, however, the wheel 104 might advantageously be provided by apparatus in accordance with the present invention, as shall be described below.

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

In the case where the pipeline supporting surface of the wheel comprises a roller type conveyor, the rollers of the conveyor, and hence the "wheel" itself, would be freely rotatable (ie "idling" or "freewheeling") and the path of the roller type conveyor need extend around the periphery of the circular supporting structure only through substantially 270° plus an additional angle to accommodate any desired variability of the pipeline launch angle, rather than through the full 360° of the circular structure.* In the case where the pipeline supporting structure comprises an endless belt conveyor or the rim of a rotatable wheel, the belt conveyor or wheel may either be driven (for example, by one or more drive sprockets, not shown) or freely rotatable, depending upon the pipeline tensioning arrangements which are to be employed (as shall be discussed further below) . This is also the case where the pipeline diverter is provided by apparatus in accordance with the present invention.

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

It will be noted that in the embodiments of Figs. 1 and 3 to 6, the diversion of the pipeline between the horizontal and the final launch angle is always in the

same direction, although the degree of curvature may vary along the pipeline path.

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

In this example the pipeline is launched through a moonpool 106 adjacent the stern of the vessel, rather than from the side of the vessel as in Fig. 1. Alternatively, the moonpool 106 might be extended to the stern of the vessel so that the pipeline is effectively launched through a slot formed in the stern. As indicated above, similar arrangements might be employed with the pipeline diverter structure located at the bow of the vessel.

The wheel 104 might be approximately 60 metres in diameter, the overall vessel length being approximately 300 metres with a beam of approximately 42 metres. A 60 metre diameter wheel allows the laying of rigid steel pipe up to about 30 inches (762 mm) outside diameter. In this example, the rearward rim of the wheel 104 is cantilevered over the stern of the vessel, allowing the pipelaying mechanism also to be used as a heavy lift mechanism. The vessel may also be equipped with a conventional pipelay stinger 108 extending from the

stern, allowing conventional "S-lay" pipelaying independent of the wheel 104. This would be suitable for operations in shallow waters.

The pipeline 102 to be laid by the vessel is assembled from individual "joints" of pipe to form "stalks", typically 12 joints in length. The stalks are welded together prior to being passed around the wheel 104. The deck space of the vessel is utilised to ensure that the pipe stalks are assembled and tie-in welds connecting the stalks together are completed at a rate which does not impede the pipelaying operation of the vessel.

The length of the vessel is sufficient to accommodate two assembled stalks laid end to end. As seen in Fig. 9, a first assembled stalk 110 extends along the centreline of the vessel from the bow of the vessel to a first weld station 112. A second assembled stalk 114 extends along the centreline of the vessel from the first weld station 112 to a second weld station 116, adjacent the wheel 104. The stalks 110, 114 are supported and aligned by a plurality of adjustable shoes 118 disposed along the length of the deck. The forward end of the first pipe stalk 110 is supported by an extension 119 of the deck projecting forwards from the bow of the vessel.

The stalks are fabricated from individual pipe joints in first and second stalk fabrication lines 120, 122 extending along either side of the sternward half of the vessel parallel to the second stalk 116. Assembled stalks are transported forward to first and second repair lines 124, 126, extending along either side of the forward half of the vessel, parallel to the first

pipe stalk 110, where faults are identified and made good by mobile repair stations 128, 130 adapted to travel backwards and forwards along the lengths of the repair lines 124, 126. From the repair lines 124, 126, the stalks are moved inwardly to first and second storage areas 132, 134 between the repair lines 124, 126 and the first stalk 110, where a plurality of assembled stalks may be stored prior to being transported to the main, central "firing line" when required.

In operation of the vessel, a supply of stalks would be fabricated and stored in areas 132, 134 prior to commencement of pipelaying. Pipelaying would commence by an initial stalk being loaded into the forward section of the firing line (the position occupied by the first stalk 110 in the Fig. 9), transported sternwards to the position occupied by the second stalk 114 and then pulled around the wheel 104 by an initiation cable (as is known generally in the art), until its forward end reaches the second weld station 116. This initial stalk is then clamped by means of a clamping mechanism 136 disposed between the second weld station 116 and the wheel 104.

The next stalk would then be loaded into the forward section of the firing line and moved sternwards until its leading end reaches the second weld station 116 and its trailing end is aligned with the first weld station 112. A further stalk is then loaded into the forward section of the firing line with its leading end at the first weld station. Tie-in welds can then be made simultaneously between the initial stalk and the next stalk at the second weld station 116 and between the next stalk and the further stalk at the first weld

station 112. Non-destructive testing (NDT) and field- coating of the tie-in welds are also carried out at the weld stations 112, 116. Once welding, testing and coating are complete, the initial stalk can be undamped and the assembled pipeline fed around the wheel 104. As soon as the pipeline clears the forward section of firing line, another stalk can be loaded and transported forward behind the welded pipeline, whereafter a further stalk may be loaded into the forward section of the firing line.

Once the trailing end of the welded pipeline reaches the second weld station, the pipeline is clamped as before and welding of the next two stalks may commence. Simultaneously, new stalks are being assembled in the fabrication lines 120, 122 and tested/repaired in the repair lines 124, 126, to replace those which have been loaded from storage into the firing line. This process is repeated in cyclical fashion throughout the pipelaying operation.

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

First and second cranes 144, 146 are mounted on a first travelling gantry 148, which straddles the fabrication lines 120, 122, for loading pipe onto the vessel from port and starboard. A further utility crane 150 is

mounted on a second travelling gantry 152 which straddles the repair lines 124, 126. An accommodation block 154 for personnel also straddles the repair lines 124, 126 at the bow of the vessel, and supports a helicopter landing deck 156.

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

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

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

The horizontal alignment apparatus comprises first, second and third roller track assemblies 162, 164, 166 of a type generally known from existing pipeline straightening and tensioning apparatus. The first, forward section aligner 162 is positioned immediately aft of the clamp 136 on the same side of the pipeline 102 as the forward edge of the wheel 104. The second, mid-section aligner 164 is located aft of the first

aligner 162 on the opposite side of the pipeline 102 from the first aligner 162. The pipe-engaging surface of the second aligner 164 is profiled to define the curvature required to bend the pipeline 102 into alignment with the wheel rim. The third, aft section aligner 166 is located aft of the second aligner 164 on the same side of the pipeline as the first aligner 162. ' The second aligner 164 is relatively longer than the first and third aligners 162, 166, which provide reaction points for the pipeline to be bent to the curvature of the second aligner 164. It is desirable for the horizontal alignment of the pipeline 102 to be performed prior to any vertical deflection thereof.

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

After passing around the wheel 104, the pipeline 102 must, in general, be at least partially straightened before being launched from the vessel. In this example, pipeline straightening is performed by first and second straightener shoes 172, 174, which comprise further roller track assemblies. The first straightener shoe 172 is located on the opposite side of the pipeline 102 from the wheel rim, downstream from the point where the pipeline 102 leaves the wheel rim in the direction of pipeline travel. The second straightener shoe 174 is located on the opposite side of the pipeline 102 from the first shoe 172, downstream thereof. The two

straightener shoes 172, 174 together with the wheel rim itself define a three-point straightening mechanism of a type which is generally well known in the art. This straightening mechanism straightens the plastic bending of the pipeline in the vertical plane induced by the passage of the pipeline around the wheel 104. Any horizontal plastic bending induced by the aligners 162, 164, 166 is removed by the tension on the pipeline 102 as it passes around the wheel 104.

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

When the pipeline launch angle is varied from 90°, the point at which the pipeline 102 departs from the wheel rim moves farther round the circumference of the wheel rim (ie the pipeline is diverted through more than 270°). Accordingly, the straightener shoes 172, 174 must also be moved as shown. For this purpose, the straightener shoes 172, 174 may suitably be mounted on a carriage (not shown) adapted to travel around the wheel rim. This is easier to accomplish in a static structure having a peripheral roller or endless belt conveyor, or comprising apparatus in accordance with the present invention, than it would be in a wheel which rotates about a central hub.

The degree of possible variation in the pipeline launch

angle depends upon the extent to which the wheel 104 is angled relative to the vessel centreline. The shallower the launch angle, the greater becomes the required angle between the plane of the wheel 104 and the vertical plane through the vessel centreline, in order to allow the pipeline to cross itself without clashing. A 6° to 10° wheel offset angle is contemplated, allowing the pipeline launch angle to be varied in a range of the order of 90° to 50°. This corresponds to the pipeline being diverted through an angle in the range 270° to 310° for a stern-launching vessel as illustrated, or 270° to 230° for a bow-launching vessel.

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

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

When "abandoning" the pipeline 102, it would be clamped

by the primary clamp 178 and cut at a point immediately above the primary clamp 178. The A&R cable would then be connected to clamped end of the pipeline, which may then be undamped and lowered into the water as required. During recovery operations, the free end of a previously abandoned pipeline would be connected to the A&R cable and pulled up to be clamped by the primary clamp 178, where it would be re-welded to the end of a pipeline passing around the wheel 104 and through the straightener 172, 174, at the welding station 177.

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

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

If the wheel 104 is allowed to idle or "free-wheel", then the full lay tension may be provided by the back

tension applied to the horizontal pipe, or by a tensioning mechanism applied to the pipeline after it departs from the wheel. Alternatively, the full lay tension could be applied by a braking force applied to the wheel 104. In practice, it is likely to be desirable to exploit the "capstan effect" created by the passage of the pipeline around the curved pipeline supporting surface of the wheel 104, for which purpose the wheel would have to be driven (or the pipeline braked by other means) and some degree of back tension would always be required. This "capstan effect" could be enhanced by passing the pipeline through multiple turns about the wheel 104 (ie through 630° or more), although this would entail significantly greater mechanical complexity. Combinations of any or all of these alternatives are possible.

Tension may be applied to the pipeline before or after the wheel 104 by any suitable means such as combinations of static and moving clamps as previously discussed in relation to Fig. 1, or caterpillar-track type tensioners ("roller track assemblies") of a type which are generally well known in the art. The use of a tensioning mechanism upstream of the second weld station 116 in the direction of pipeline travel is desirable, since this may also be employed in S-lay operations using the conventional stinger 108.

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

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

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

The path defined by the roller track assemblies may have a substantially constant radius of curvature or the radius of curvature may vary along the length of 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

pipeline diverter on board a vessel as shown in Figs. 1 to 6, the plane of the pipeline path would have to be set at an angle to the vertical plane including the horizontal pipeline axis, and horizontal diverter means would be required to divert the pipeline into alignment with the path, as in Figs. 5 and 6.

However, if the apparatus is configured to define a helicoidal path, then the path may initially be colinear with the pipeline axis and the helicoidal path will shift the pipeline sideways allowing it to cross itself upon exiting the apparatus. This is illustrated in Fig. 8, which shows a plan view of the path taken by a pipeline 218 around a diverter such as that shown in Fig. 7. A first portion 218a of the pipeline extends from an assembly line and is bent upwardly through 90° around the lower arc of the pipeline path; a second portion 218b is bent through a further 180° about the upper arc of the path and simultaneously shifted sideways by the helicoidal pitch of the path; and a final portion 218c is bent through a further angle (if required) to its final launch angle, extending substantially parallel to said first portion 218a when viewed from above. In this example the pipeline 218 is launched via a moonpool 220, located between first and second stalk fabrication lines 222, 224, as in Fig. 4.

If all of the roller track assemblies are idle, then the apparatus serves simply as a guide to divert the pipeline, and any required tension must be applied by other means upstream and/or downstream of the apparatus. In preferred embodiments, some or all of the roller track assemblies are driven so that the apparatus provides at least a proportion of the required tension. Most preferably, a degree of back

tension is provided by tensioning means upstream of the apparatus in the direction of pipeline travel, enabling the "capstan effect" of the apparatus to be exploited.

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

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

In the absence of external, opposed roller track

assemblies, the tension contributed by each of the roller track assemblies 202, 204 is a function of the friction between the belts 209 of the assemblies and the pipeline 216. The friction in turn is proportional to the tension in the pipeline and the angle subtended by the assemblies (ie the length of the assemblies). Accordingly, the lengths of the assemblies 202, 204 vary around the pipeline path, decreasing progressively in the direction of travel of the pipeline.

The pipeline supporting surfaces of the roller track assemblies have an arcuate, longitudinal profile, the radius of curvature thereof preferably being slightly smaller than the corresponding radius of the pipeline path as such; eg the radius of curvature of the assemblies might be 29.5 metres for a path radius of 30 metres.

Fig. 9 shows a further example of a pipeline diverter structure embodying the invention, in which the series of roller track assemblies 228 are mounted on a structure 230, which is in turn supported by a framework 232 mounted on a truss 234. In this case, every second roller track assembly 228 in the first 270° of the pipeline path has a corresponding external, opposed roller track assembly 236, and additional assemblies 238 extend the path beyond 270° to provide additional support for the pipeline 240 when the pipeline launch angle is less than 90°. The pipeline path may lie in a single plane or may be helicoidal. The drawing also shows a gimbal-mounted clamping assembly 242, similar to that of Fig. 5. In this case a three-roll straightener assembly 244 is mounted on the clamp assembly 242, rather than on the diverter structure itself as in Fig. 5. This straightener

arrangement may also be employed with the other types of diverters described herein, as may the arrangement of the framework 232 and truss 234.

Fig. 14 shows a further, preferred example of a pipeline diverter structure embodying the invention. In this case there are no external tensioner assemblies. Otherwise the arrangement is broadly similar to that of Fig. 7, with a first set of seven roller track assemblies 246 each contributing a first tensile force, a second set of two roller track assemblies 248 each contributing a second tensile force, less than the first tensile force, and a third set of two roller track assemblies 250 each contributing a third tensile force, less than the second tensile force. Fig. 15 is an end view illustrating the helicoidal path of the pipeline 252. A similar arrangement of roller track assemblies might also be used to define a pipeline path lying in a single plane.

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

In Figs. 10(a) and 10(b), the support pad 254 is mounted on the chain or belt 256 of the roller track assembly, and has a transverse, sectional profile including a central groove 258 which is generally part circular in cross-section to accommodate the pipeline 260. The lowermost part of the groove 258 includes a V- shaped notch 262 which may accommodate an A&R cable

264. The V-shaped configuration allows cables of different diameters to be seated, as indicated in the drawing by a smaller diameter cable 266. Additional grooves 268, 270 on either side of the central groove 258 may accommodate additional cables 272, 274. This example also shows the use of "diabolo" type rollers 276 of an external, opposed tensioner assembly bearing on the outer surface of the pipeline 260.

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

Figs. 12(a) and 12(b) show an arrangement similar to that of Fig. 10, and like parts are designated by like numerals. In this case the diabolo rollers 276 of Fig. 10 are replaced by an endless belt 294 of an external, opposed tensioner, which itself has pipeline contacting pads 296 secured thereto (omitted from the side view of Fig. 12(b)). Figs. 13(a) and 13(b) correspond to Fig. 11 in the same way that Fig. 12 relates to Fig. 10.

The pads 254, 278 may typically be about 300 mm in length. Where the lengths of the roller track assemblies vary around the pipeline path, it is preferred that the lengths of individual roller track assemblies are selected so as to allow standard pad sizes to be used.

Figs. 16(a) - (f) illustrate procedures for feeding a

pipeline around a diverter structure and for subsequently "springing" the pipeline out of its normal path to allow the deployment of an A&R cable, or the like, without the need for completely removing the pipeline from the diverter structure. It is particularly preferred that these procedures be employed with a structure such as that illustrated in Figs. 14 and 15, employing multiple roller track assemblies to define a helicoidal path, but they are also applicable to other types of arcuate diverter structures as described herein. The following description assumes a helicoidal pipeline path. A planar path would also require horizontal diversion of the pipeline as it engages the diverter structure, as previously described.

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

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

As seen in Fig. 16(a), a pipe joint (typically 12m in length) which has been pre-bent substantially to the curvature of the pipeline path is welded to the downstream end of a first pipestalk 300a. The initiation cable 312 (in this example, a 76mm wire) is passed around the diverter structure and secured to the downstream end of the pre-bent pipe joint 314, which is located slightly upstream of the initial roller track 308. The pre-bent pipe joint 314 is shown in Fig. 16(a) with its plane of curvature perpendicular to the deck of the vessel.

In order to bring the pre-bent pipe joint 314 into initial engagement with first of the diverter track assemblies 302, the first pipestalk 300a is rotated through 90° about its longitudinal axis so that the plane of curvature of the pre-bent joint 314 is parallel to the deck of the vessel, and the pipeline 300 is pulled in the downstream direction until the pre-bent joint 314 lies below the first diverter track 302, as indicated by the dashed lines in Fig. 16(b). The pipestalk 300a is then rotated back to its original orientation, such that the plane of curvature of the pre-bent pipe joint 314 is again perpendicular to the deck and engages the surface of the first diverter track 302, as also shown in Fig. 16(b). A second pipestalk 300b is then fed along the firing line and welded to the upstream end of the first pipestalk 300a. The first stalk 300a is preferably relatively shorter than subsequent stalks in order to facilitate the rotation described above.

The pipeline 300 is then pulled around the diverter structure until the pre-bent joint 314 reaches the straightener rolls 304, 306, which are opened as shown

in Fig. 16(c) such that the pre-bent joint may pass therebetween without yielding. With the straightener rolls 304, 306 open, the pipeline 300 is pulled through until its downstream end clears the downstream end of the second straightener roll 306, and the straightener rolls 304, 306 are closed on the pipeline as shown in Fig. 16(d). At this point the initiation cable 312 is detached and the pre-bent pipe joint 314 is cut off the downstream end of the pipeline 300 for subsequent re- use. Thereafter, pipelaying proper may commence, with the pipeline 300 typically being guided to its starting point on the seabed by means of a further initiation cable and winch (not shown) as is well known in the art.

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

In accordance with this procedure, the first

straightener track 304 is braked and the pipeline 300 is clamped thereto by any suitable means 320. The main clamp 310 is also activated to clamp the pipeline downstream of the straightener. The pipeline 300 may then be cut between the second straightener roll 306 and the main clamp 310. The pipeline 300c passing around the diverter structure is then displaced radially outwards from the pipeline path around the diverter by relaxing the back tension on the pipeline and/or feeding the pipe towards its clamped end at the first straightener roll 304, such that the pipeline 300c "springs" outwards from the path. The straightener rolls 304, 306 may be opened to facilitate this. The outward movement of the pipeline 300c is restrained by the hooks 316, which are mounted around the pipeline path, spaced outwardly from the roller track assemblies 316 to allow the pipeline 300c to spring outwards by an appropriate distance (suitably 1.0m).

Once the pipeline 300c has been displaced from its normal path, the A&R cable 322 may be passed around the diverter structure along the pipeline path and secured to the upstream end of the pipeline 300d held in the main clamp 310 as seen in Fig. 16(f). The initial roller track assembly 308 may be lowered for this purpose, if necessary. The A&R cable 322 may then be deployed to lower the pipeline 300d to the seabed.

Subsequent recovery of the pipeline involves the reversal of this procedure, with the abandoned pipe 300d being pulled back up from the seabed and held in the main clamp 310. The A&R cable 322 is then withdrawn from the diverter structure, back tension applied to the pipeline 300c extending around the

diverter 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.