Patent Description:
As explained in <CIT> to the Applicant, flexible elongate elements such as flexible pipelines are most commonly laid underwater by an installation vessel that firstly spools the element onto a reel or carousel. During installation offshore, the element is unspooled from the reel or carousel and is then overboarded into the sea to hang from the vessel as a catenary. Rigid pipelines can also be laid by this reel-lay technique if the pipeline is straightened after unspooling to reverse plastic deformation imparted to the pipeline by spooling. In this respect, the invention is primarily concerned with flexible elements such as flexible pipelines but in a broad sense, the principles of the invention can also be used with rigid pipelines launched into the sea along an upright launch axis.

Between unspooling and overboarding, the elongate element passes over structures that guide the element, such as a tower, a chute or a ramp, and through various items of equipment that may contribute to hold-back tension, such as aligners, straighteners or tensioners. The inclination of a tower, chute or ramp may be adjustable, for example on a vessel fitted with a tilting lay tower whose inclination may depart from the vertical.

Frictional hold-back devices such as tensioners or friction clamps can be used to support the suspended weight of an elongate element. Examples of such devices may be found in <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>. However, the reliance of such devices upon friction means that there is nothing else to hold the element if it starts to slip through the device, for example because the outer surface of the element has a poor surface finish or is wet or oily. Also, hold-back devices have to be moved away from the launch axis of the element to allow laterally-protruding equipment that is wider than the remainder of the element, such as accessories or modules, to be attached to the element and to allow such equipment to bypass the hold-back device in the launch direction.

Installation of elongate elements on the seabed in deep water requires the installation vessel to have sufficient hang-off capacity to support the weight of the long catenary that is suspended in the water column between the vessel and the seabed. Usually, hang-off systems are used to keep the upper end of the element supported at deck level for connection to equipment such as in-line modules before deployment and also for connection between ends of pipeline sections during an installation campaign. In those situations, the element has to be suspended temporarily without moving in the launch direction.

<CIT> describes a device for supporting a connection tip of a flexible pipe. The device includes a holding table in which an insert is placed, said holding table comprising an axial passage that forms a tapered interior space. The device also comprises an inserted part for holding the tip, said part comprising a means for fitting onto the entire periphery of tips of different outer diameters.

It is conventional for a laterally protruding hang-off feature of an elongate element to be engaged mechanically with a hang-off plate or bushing on the pipelaying vessel. The element may hang from such a hang-off structure through a moonpool of the vessel or over the side or stern of the vessel. The laterally protruding hang-off feature that abuts a shoulder of the hang-off bushing may be a flanged collar or another item of equipment that is wider than the remainder of the element, such as an accessory or a module attached to the element. This provides a steady and reliable mechanical connection between the element and the laying equipment of the vessel.

For example, a hang-off collar may be a metallic part of the elongate element that defines a radially-projecting flange or ring. Examples are a forged radially-projecting ring that is incorporated into the element, or forgings comprising such rings that are attached to an end of the element or incorporated at intervals along the element. Other specific examples of equipment that has a greater diameter than the remainder of the element are a connector, an end fitting or an armour pot.

An example of a conventional hang-off system of the prior art is shown in <FIG> of the accompanying drawings. An elongate element <NUM> that is exemplified here as a flexible pipeline extends along a generally vertical launch axis as it passes through the hang-off system <NUM>. The hang-off system <NUM> comprises a tubular support structure <NUM> whose inner opening flares downwardly to accommodate bending of the elongate element <NUM>.

The elongate element <NUM> carries an armour pot <NUM> as an example of a laterally-protruding hang-off feature. The element <NUM> further comprises a vertebrae bend restrictor <NUM> extending from the armour pot <NUM>.

The open top of the tubular support structure <NUM> is closed by a hang-off bushing <NUM> that is assembled in two halves around the elongate element <NUM> and so has a central hole <NUM> to accommodate the element <NUM>.

A simple hang-off bushing <NUM> like that shown in <FIG> can only accommodate one diameter of elongate element <NUM>: in other words, a hang-off bushing <NUM> cannot be purpose-designed as a universal hang-off insert for all such elements <NUM>. Consequently, it is conventional to use one of a selection of split hang-off inserts <NUM> as an adaptor between a specific element <NUM> and a hang-off bushing <NUM>. The inner edge region of the hang-off bushing <NUM> around the central hole <NUM> serves as a shoulder upon which the hang-off insert <NUM> rests.

The hang-off insert <NUM> is made of semi-circular or half-moon parts machined from steel, whose internal curvature matches the external curvature of a particular elongate element <NUM>. The two parts of the hang-off insert <NUM> are bolted together around the element <NUM> to lie between the element <NUM> and the hang-off bushing <NUM>. The armour pot <NUM> sits on the hang-off insert <NUM>. This transfers the weight of the element <NUM> to the hang-off bushing <NUM> through the hang-off insert <NUM>.

As noted above, the armour pot <NUM> is just an example of a hang-off feature protruding laterally from the elongate element <NUM>. Such a feature may be provided by any other equipment that has a greater diameter than the remainder of the element <NUM>, or by a flanged collar protruding radially from the element <NUM>.

An installation vessel may have to cater for elongate elements <NUM> of many different diameters during routine operations. Each diameter of element <NUM> requires a different hang-off insert <NUM>. Consequently, around fifty different hang-off inserts <NUM> may be required per vessel. This involves a high cost of design and fabrication and requires a large area of deck space on the vessel to store multiple hang-off inserts <NUM> onboard.

Alternatively, there is a risk of expensive downtime to fabricate or obtain a specific hang-off insert <NUM> if such an insert is not kept onboard.

To mitigate these drawbacks of conventional prior art, <CIT> discloses a hang-off insert in the form of a circular loop that comprises circumferentially-spaced support segments. Collectively, the segments define a substantially planar support face of the insert and have respective radially inner faces that define an inner radius of the loop. The radially inner faces of the support segments can be positioned at various radial positions to determine the inner radius of the loop and hence to adapt the circumference of the loop to suit different diameters of elongate subsea elements.

With the hang-off insert supported by a hang-off structure of the vessel, a laterally-protruding hang-off feature of the elongate element extending through the loop may be rested on the support face to transfer suspended weight loads through the insert to the hang-off structure.

<FIG> illustrates a hang-off system <NUM> comprising a hang-off insert <NUM> as taught by <CIT>, in place of the rigid split hang-off insert <NUM> of the prior art as shown in <FIG>. Otherwise, the hang-off system <NUM> of <FIG> is similar to the hang-off system <NUM> of <FIG>, so like numerals are used for like features.

The hang-off insert <NUM> is tightened around and encircles an elongate element <NUM>, again exemplified here as a flexible pipeline of circular cross-section that extends along a generally vertical launch axis as it passes through the hang-off system <NUM>.

As in the hang-off system <NUM> shown in <FIG>, the hang-off system <NUM> shown in <FIG> comprises a tubular support structure <NUM> whose open top may be closed by a hang-off bushing <NUM> that is assembled in two halves around the elongate element <NUM>. The hang-off bushing <NUM> has a central hole <NUM> to accommodate the elongate element <NUM>.

The inner edge region of the hang-off bushing <NUM> around the central hole <NUM> serves as a shoulder upon which the hang-off insert <NUM> rests. In use of the invention, a laterally-protruding hang-off feature of the elongate element <NUM> such as an armour pot <NUM> as shown in <FIG> (which has been omitted from <FIG> for clarity) rests in turn on the hang-off insert <NUM> to transfer loads of the elongate element <NUM> through the hang-off insert <NUM> to the hang-off bushing <NUM>.

Against this background, the invention resides in a hang-off system comprising at least one support block that is movable forwardly toward a launch axis for engagement with an elongate element being laid from a vessel into water. The or each support block comprises an array of plates that together define an engagement face of the support block and are movable relative to each other to conform a contour of the engagement face to a contour of the element. Each plate comprises mutually parallel upright side faces joined by an upper face that is narrower than either of the side faces of that plate and the upper faces of the plates together define an upper face of the support block.

Each plate may comprise a lower face that is parallel to the upper face, the lower faces of the plates together defining a lower face of the support block.

The side faces of each plate may also be joined by a front face, the front faces of the plates together defining the engagement face of the support block. The engagement face of the support block may be inclined forwardly and upwardly toward an upper leading edge of the block.

The front face of each plate may be shaped to define a facet that is angled acutely relative to a plane of a side face. The facets of one subset of the plates may be in mirror relation to the facets of another subset of the plates, such that the facets of both of those subsets face toward the launch axis. The subsets may be separated by an upright plane that bisects the support block and that contains the launch axis.

The plates can be moved relative to each other in respective upright planes, which planes may be mutually parallel and parallel to a plane containing the launch axis.

A housing may constrain the plates against movement transverse to the forward direction. For example, the housing may comprise side walls disposed on respective sides of the support block that constrain lateral movement of the plates. The housing may further comprise a top wall disposed above the support block that constrains upward movement of the plate. The housing may define an aperture through which the support block can be advanced forwardly from the housing.

Actuators may act on the block portions to drive forward movement of the block portions. It is also possible for the block portions to be biased forwardly, for example by springs.

Conveniently, the support block can be mounted on a jaw of a hang-off bushing, for example via a housing fixed to that jaw. The support block may be movable relative to the jaw of the hang-off bushing. For example, the support block may be movable forwardly or be pivotable about horizontal and/or vertical axes relative to the jaw of the hang-off bushing.

The inventive concept embraces a lay system or a vessel comprising the hang-off system of the invention. The inventive concept also extends to a corresponding method of hanging-off an elongate element being laid from a vessel into water. The method comprises advancing first and second portions of a support block into contact with the element beneath an outwardly-projecting formation of the element wherein the first and second portions are advanced in parallel planes; effecting relative displacement between those portions to conform a contour of the support block to an abutting contour of the elongate element; and hanging-off the element from the portions of the support block in contact with an underside of the outwardly-projecting formation.

Relative displacement between the portions of the support block may take place after bringing the first portion into contact with the element. For example, the first portion of the support block may be advanced into contact with the element and then, with the first portion stationary relative to the element, the second portion of the support block may be advanced into contact with the element. Alternatively, relative displacement between the portions of the support block may take place before bringing either portion into contact with the element. In either case, relative displacement may involve advancing a leading edge of the second portion beyond a leading edge of the first portion.

The portions of the support block are preferably advanced in directions parallel to an upright plane containing a launch axis of the element. The portions of the support block are preferably constrained against transverse movement and/or upward movement.

Movement of the portions of the support block may be driven individually. The portions of the support block may be biased toward the element, in which case relative movement between the portions may be effected against that bias.

The support block may be moved with and/or relative to a supporting jaw of a hang-off bushing, for example by translational movement or pivotal movement of the support block about horizontal and/or vertical axes relative to the supporting jaw.

Whilst the adaptable hang-off insert of <CIT> has significant advantages over the multiple hang-off inserts required by conventional prior art, the inventors have now addressed the problem of adapting a hang-off-system from a different perspective. Specifically, they have explored a fresh approach in which the hang-off structure itself can adapt to suit elongate elements of different diameters, without necessarily requiring an adaptable insert.

The invention contemplates that a hang-off structure such as a hang-off bushing can comprise a series or set of plates assembled in parallel to form a supporting block. Each plate can move independently of other plates of the set to change the shape of the block, particularly the shape or curvature of a face or an upper edge of the block that abuts an elongate element to be supported by the block. This adapts a leading end or edge of the set to complement the external diameter or shape of the element, which may include a fitting on the element such as an end fitting of a flexible pipeline.

Like <CIT>, the invention solves the problem of providing a supporting interface between a hang-off structure and pipelines or other elongate elements, or their fittings, that are not standardised and so may have various shapes and diameters.

The invention provides a versatile alternative to hang-off inserts of the prior art. The solution of the invention can comply with a wide range of diameters of elongate elements that may be suspended from a hang-off structure and ensures a reliable mechanical interface between equipment of the element and the hang-off structure.

The invention improves safety because it requires no work to be performed under a suspended load. The invention also generates a considerable cost saving. By reducing the setup time for each hang-off operation by <NUM>% to <NUM>%, the invention could, on aggregate, save hundreds of thousands of US dollars of operational cost per vessel, per year. There is also a saving in the cost of fabricating bespoke hang-off inserts as sometimes required in the conventional prior art. Unlike the hang-off inserts of the prior art, apparatus of the invention can be assembled and disassembled, if ever necessary, without impacting the critical path of a laying operation. Also, preliminary results suggest that in comparison with a prior art solution, the invention could reduce loads on key components by <NUM>% to <NUM>%. The invention is a hang-off system according to claim <NUM> and a method of hanging-off an elongate element according to claim <NUM>. Advantageous embodiments of the invention are defined in the dependent claims.

Embodiments of the invention provide a device for supporting a formation on a pipeline or other elongate element, such as a head or a termination of a flexible pipeline, during installation from a vertical or tiltable lay system, the device comprising at least two partial support boxes, each box comprising a plurality of vertical plates, each plate being able to slide horizontally to adjust the position of the top of the plate to the shape and diameter of the formation on the pipeline.

The plates may be biased or forced in the direction of the pipeline, for example by a hydraulic circuit, by jacks or by springs. The plates can also be tilted slightly in a vertical plane.

Each box may comprise four or five walls and one open side through which the plates can slide. The number of plates in a box may be determined by filling in the width of the open side with the sum of the thicknesses of the plates. The plates may be fully packed in the box.

The plates need not necessarily all have identical thickness. For example, outer or outermost plates may be thicker than inner or innermost plates, or vice versa.

The boxes may be mounted on mountings such as gimbals, pivots or rubber pads that are arranged to accommodate any misalignment of the flexible pipeline with the normal launch direction.

Embodiments of the invention also implement a method for supporting a formation of a flexible pipeline during installation from a vertical or tiltable lay system. The method comprises: providing boxes containing a plurality of vertical support plates; guiding the support plates around the trajectory of the flexible pipeline; adjusting the transverse positions of the plates by sliding them inside or relative to the respective boxes until the plates are in contact with the flexible pipeline or a bottom part of the formation; and then abutting the bottom of the formation with the top of the plates.

Thus, in embodiments of the invention, a hang-off system comprises support blocks that are movable toward a launch axis for engagement with an elongate element, such as a flexible pipeline, being laid from a vessel into water. Each support block comprises an array of plates or other block portions that together define an engagement face of the support block, adapted to engage the element. The plates are movable relative to each other to bring a contour of the engagement face into conformity with a contour of the element. Each plate comprises upright side faces joined by an upper face that is narrower than either of the side faces of that plate and the upper faces of the plates together define an upper face of the support block.

Reference has already been made to <FIG> of the drawings to illustrate hang-off systems known in the prior art. In those drawings:.

In order that the invention may be more readily understood, reference will now be made, by way of example, to the remainder of the accompanying drawings, in which:.

Referring firstly to <FIG> of the drawings, support blocks <NUM> of the invention are held in respective housings <NUM> mounted on respective jaw sections of a hang-off bushing <NUM>. The support blocks <NUM> are therefore in mutual opposition around an elongate element <NUM> supported by the hang-off bushing <NUM>, the element <NUM> in this example being a flexible pipeline <NUM> surrounded by an end fitting <NUM>.

The pipeline <NUM> is coaxial with an upright launch axis <NUM> that is nominally vertical but may depart from the vertical, for example when laying a pipeline <NUM> from a tiltable lay tower of a vessel. In that case, the hang-off bushing <NUM> could, correspondingly, depart from a horizontal plane to remain orthogonal to the launch axis <NUM>.

In the arrangement shown, there are two support blocks <NUM> equiangularly spaced around the launch axis <NUM>, hence at an angle of <NUM>° relative to each other. In other arrangements, there could be more support blocks <NUM>, for example three or four support blocks <NUM> at angles of <NUM>° or <NUM>° to neighbouring support blocks <NUM> around the launch axis <NUM>.

When advanced telescopically from within its housing <NUM> in a forward direction, that being a radially inward direction toward the launch axis <NUM>, an end of each block <NUM> protrudes from its housing <NUM> in cantilever fashion and overhangs a central hole <NUM> in the bushing <NUM>. A front face <NUM> of the protruding end of the block <NUM> engages with the pipeline <NUM>, thus being an engagement face of the block <NUM>. Specifically, an upper leading edge <NUM> of the front face <NUM> engages under a radially protruding flange <NUM> of the end fitting <NUM>.

In a retracted or rest configuration, each block <NUM> is approximately cuboidal, comprising a planar upper face <NUM>, a planar lower face <NUM> parallel to the upper face <NUM>, and planar side faces <NUM> parallel to each other and orthogonal to the upper and lower faces <NUM>, <NUM>. The upper and lower faces <NUM>, <NUM> are both nominally horizontal to match the plane of the hang-off bushing <NUM>. The block <NUM> is of squat or shallow proportions, with the upper and lower faces <NUM>, <NUM> being substantially larger than the side faces <NUM>. In this example, however, the block <NUM> departs from a cuboidal shape in that its front face <NUM> is not orthogonal to the other faces <NUM>, <NUM>, <NUM>. Instead, the front face <NUM> is inclined forwardly in an upward direction from the lower face <NUM> to the upper face <NUM>. Thus, the upper face <NUM> of the block <NUM> is longer or deeper from front to back than the lower face <NUM>. The resulting chamfered profile of the front face <NUM> better transfers loads from the end fitting <NUM> to the hang-off bushing <NUM>. Also, as will be described later, the front face <NUM> of the block <NUM> is contoured and hence non-planar.

By virtue of the invention, the shape or contour of the block <NUM> and particularly its front face <NUM> reconfigures or adapts to match, complement or conform to the external shape or contour of the end fitting <NUM>, especially the radius of curvature of the end fitting <NUM>. Thus, the front face <NUM> adopts a female or concave contour in response to encountering the male or convex contour of the end fitting <NUM> when the block <NUM> is moved toward the launch axis <NUM>. To enable reconfiguration in this way, each block <NUM> is divided into block portions that can move relative to each other. Specifically, each block <NUM> comprises an array of planar support elements being rigid leaves or plates <NUM>, suitably made of steel. Each plate <NUM> can move relative to neighbouring plates <NUM> of the array in directions parallel to the upper, lower and side faces <NUM> of the block <NUM>, hence forwardly and rearwardly.

The plates <NUM> are arranged in a horizontal stack, lying in upright, nominally vertical planes that are parallel to each other and to the forward direction in which the block <NUM> advances from the housing <NUM> toward the launch axis <NUM>. The planes of the plates <NUM> are also substantially parallel to an upright plane <NUM> containing the launch axis <NUM> as shown in <FIG>. The plates <NUM> are all substantially identical to each other although, as will be explained, subsets of the plates <NUM> may have contoured front faces <NUM> that are oppositely handed or mirrored to suit the shape of the pipeline <NUM> on opposite sides of the plane <NUM> containing the launch axis <NUM>.

<FIG> show that like the block <NUM>, each plate <NUM> is approximately cuboidal, comprising a planar upper face <NUM>, a planar lower face <NUM> parallel to the upper face <NUM>, and planar side faces <NUM> parallel to each other and orthogonal to the upper and lower faces <NUM>, <NUM>. The planes of the side faces <NUM> correspond to the planes of the plates <NUM>. The front face <NUM> of each plate <NUM> is inclined forwardly in an upward direction to lend the aforementioned chamfered profile to the block <NUM>.

The upper and lower faces <NUM>, <NUM> of the plates <NUM> all lie in respective nominally horizontal common planes so that, collectively, the upper and lower faces <NUM>, <NUM> of the plates <NUM> together define the upper and lower faces <NUM>, <NUM> of the block <NUM>. The side faces <NUM> of the plates <NUM> correspond to the side faces <NUM> of the block <NUM>; indeed, the outermost plates <NUM> of the array define the side faces <NUM> of the block <NUM>. In this instance, however, the plates <NUM> are thin in a lateral direction orthogonal to the side faces <NUM>, in that their upper and lower faces <NUM>, <NUM> are much smaller than the side faces <NUM>. In this example, the side faces <NUM> of neighbouring plates <NUM> abut with sliding contact between them.

The block <NUM> is a close sliding fit in the housing <NUM>, substantially filling the width and height of an aperture <NUM> of the housing <NUM> defined by a top wall <NUM> and side walls <NUM> of the housing <NUM>, and in this case also by the hang-off bushing <NUM> that defines a base of the housing <NUM>. Specifically, the housing <NUM> comprises upright side walls <NUM> outboard of, and in close sliding contact with, the outermost plates <NUM> of the array. Between them, the side walls <NUM> of the housing <NUM> thereby hold the plates <NUM> together in close sliding contact, so that the individual plates <NUM> are supported by neighbouring plates <NUM> of the block <NUM> and will not collapse, tilt or buckle under compressive loads applied by the suspended weight of the pipeline <NUM>. Those loads are shared by the plates <NUM> in contact with the underside of the flange <NUM> of the fitting <NUM> and are transferred through the block <NUM> from the upper face <NUM> to the lower face <NUM> of the block <NUM> and from there to the hang-off bushing <NUM>.

On an inner face, the side walls <NUM> correspond in height to the plates <NUM>. The side walls <NUM> are joined by a top wall <NUM>, shown in shadow in <FIG> and <FIG> and in dashed lines in <FIG>, that is parallel to the hang-off bushing <NUM> and therefore to the upper face <NUM> of the block <NUM>. The plates <NUM> are a sliding fit between the hang-off bushing <NUM> and the underside of the top wall <NUM>. Thus, there is a sliding fit between the upper face <NUM> of the block <NUM> and the underside of the top wall <NUM> and an additional sliding fit between the lower face <NUM> of the block <NUM> and the upper surface of the hang-off bushing <NUM>. These small sliding clearances prevent the block <NUM> or the plates <NUM> pivoting about a lateral axis under the downward weight load applied by the pipeline <NUM>.

In this example, the housing <NUM> is closed by an optional back wall <NUM> that is orthogonal to the side walls <NUM>, the top wall <NUM> and the hang-off bushing <NUM>. The back wall <NUM> stiffens the housing <NUM> and leaves space on its forward side for plates <NUM> of the block <NUM> to retract into the housing <NUM> but does not interact directly with the plates <NUM>. In other examples to be described with reference to later drawings, the housing <NUM> has a bottom wall <NUM> between the side walls <NUM>, independent of the hang-off bushing <NUM>. In those examples, the plates <NUM> are a sliding fit between the underside of the top wall <NUM> and the upper side of the bottom wall <NUM>. Thus, there is a sliding fit between the lower face <NUM> of the block <NUM> and the upper side of the bottom wall <NUM>.

<FIG> show the ability of the block <NUM> to adapt to the circular-section shape of the fitting <NUM>, and to adapt to fittings <NUM> of different diameters. In particular, <FIG> shows the front face <NUM> of the block <NUM> shaped to complement a relatively wide fitting <NUM> whereas <FIG> shows the front face <NUM> of the block <NUM> shaped to complement a relative narrow fitting <NUM>. These drawings show the central position of the upright plane <NUM> that bisects the block <NUM> and that extends in the forward direction to contain the launch axis <NUM> shown in the preceding drawings. Plates <NUM> of the block <NUM> are retracted into the housing <NUM> to an extent determined by the curvature of the fitting <NUM>, with plates <NUM> closer to the plane <NUM> therefore being retracted more than plates <NUM> further from the plane <NUM>. The outermost plates <NUM> in <FIG> lie outside the radius of the fitting <NUM> and so are fully extended in the forward direction, although they would be retracted to some extent if the fitting <NUM> was any wider. Conversely, where the fitting <NUM> is relatively narrow as shown in <FIG>, more of the outer plates <NUM> are fully extended.

<FIG> show one of the plates <NUM> in isolation. The forward and upward inclination of the front face <NUM> is plainly apparent, as is the cuboidal relation of the other faces <NUM>, <NUM>, <NUM>. These drawings also show that the upper end of the front face <NUM> comprises a forward extension <NUM> of the upper face <NUM> defining the upper leading edge <NUM> of the plate <NUM>. In three dimensions, the forward extension <NUM> is prism-shaped, comprising a facet <NUM> and a stress-reducing chamfer <NUM> in respective nominally vertical planes that are orthogonal to the upper face <NUM>. The facet <NUM> and the chamfer <NUM> meet at an upright edge <NUM> that is also orthogonal to the upper face <NUM> and that intersects the upper face <NUM> at the leading edge <NUM>.

The angle of the facet <NUM> relative to the plane of the side face <NUM> reflects the curvature of the fitting <NUM> on opposite sides of the central plane shown in <FIG>. Thus, the plates <NUM> of the block <NUM> are arranged in two subsets divided by the central upright plane <NUM>, with the facets <NUM> of one subset in mirrored relation to the facets <NUM> of the other subset. Specifically, the facets <NUM> of both subsets face inwardly, facing approximately toward the launch axis <NUM> in parallel directions that will intersect the circumference of a fitting <NUM> wide enough to encounter their plates <NUM>.

As best appreciated in the plan views of <FIG> and <FIG>, the oppositely angled facets <NUM> on opposite sides of the central upright plane <NUM> approximate to, or at least approach, tangential relationship with the circumference of the fitting <NUM>. This increases the area of contact between the forward extensions <NUM> of the plates <NUM> and the underside of the flange <NUM>, helpfully reducing stress when the block <NUM> bears the weight load of the pipeline <NUM> suspended from the fitting <NUM>. The large number of plates <NUM> and the slimness of the plates <NUM> also helps to follow the curvature of the fitting <NUM> more closely and to maximise the area of load-supporting contact.

<FIG> and <FIG> show that the plates <NUM> could be driven forwardly from the housing <NUM> and into engagement with the fitting <NUM> by individual actuators <NUM> acting on the back of each plate <NUM>. In that case, the housing <NUM> can remain stationary while the plates <NUM> and hence the block <NUM> advance relative to the housing <NUM>.

In an alternative approach shown in <FIG> and <FIG>, the plates <NUM> are biased forwardly by respective springs <NUM>. The springs <NUM> could of course take forms other than the coils springs shown schematically here. When the housing <NUM> carrying the extended plates <NUM> is moved forwardly, the plates <NUM> encountering the fitting <NUM> retract into the housing <NUM> to an extent determined by the curvature of the fitting <NUM>. The springs <NUM> compress as the associated plates <NUM> retract.

Actuators <NUM> shown in <FIG> and <FIG> or springs <NUM> shown in <FIG> and <FIG> may react against the aforementioned optional back wall <NUM> of the housing <NUM>.

It will be apparent from <FIG>, <FIG>, <FIG> and <FIG> that the block <NUM> is firstly advanced forwardly until the leading edge <NUM> of the front face <NUM> comes into contact with the fitting <NUM>, with contact initially being between the innermost plates <NUM> and the circumference of the fitting <NUM> closest to the central plane <NUM>. The block <NUM> then begins to conform to the shape of the fitting <NUM> as the innermost plates <NUM> remain stationary while plates <NUM> outboard of them continue to advance forwardly with continued forward movement of the remainder of the block <NUM>. Moving outwardly from the central plane <NUM>, the plates <NUM> successively contact the circumference of the fitting <NUM> and therefore cannot advance further as the plates <NUM> outboard of them continue to advance forwardly. The result is that the leading edge <NUM> of the front face <NUM> has a stepped concavity corresponding to the convexity of the fitting <NUM>. Eventually, any outermost plates <NUM> that do not intersect the circumference of the fitting <NUM> stop in alignment with a line that intersects the launch axis <NUM>.

The housings <NUM> can be moved forwardly in accordance with <FIG> and <FIG> in various ways. For example, <FIG> shows the housings <NUM> fixed to respective jaws of the hang-off-bushing <NUM> to be moved forwardly as the jaws are brought together. Alternatively, the housings <NUM> can be moved relative to the jaws of the hang-off bushing <NUM>, for example on rails <NUM> mounted on the respective jaws and extending in the forward direction as shown in <FIG> also show a bottom wall <NUM> of the housing <NUM> that is distinct from the hang-off-bushing <NUM> as mentioned previously.

As noted previously, the preceding embodiments contemplate that the plates <NUM> of the block <NUM> may be identical apart from mirroring the facets <NUM> of their forward extensions <NUM>. However, this is not necessarily the case. In this respect, <FIG> shows a simplified variant in which the block <NUM> has fewer plates <NUM>, and facets <NUM> that vary in angle relative to the side faces <NUM> in accordance with the lateral distance from the central upright plane <NUM>. Specifically, the facets <NUM> of the outer plates <NUM> are at a smaller or more acute angle to the side faces <NUM> than the facets <NUM> of the inner plates <NUM>. Thus, the inclination of the plates <NUM> more closely matches the curvature of the fitting <NUM> and maximises the area of load-bearing contact with the flange <NUM>, even though there are fewer plates <NUM> in the block <NUM>.

<FIG> shows another variant in which plates <NUM> of the block <NUM> vary in accordance with lateral distance from the central upright plane <NUM>. In this instance, outer plates <NUM> are thicker than inner plates <NUM> in a lateral direction, transverse to the forward direction. Thus, the outer plates <NUM> have greater resistance to deformation, such as twisting, under downward weight loads and so are better able to support the thinner inner plates <NUM> closer to the central plane <NUM> when the block <NUM> is advanced forwardly from the housing <NUM>.

If the plates <NUM> are strong enough, an alternative arrangement may be possible in which the outer plates <NUM> are thinner than the inner plates <NUM>, the better to follow the curvature of the fitting <NUM> away from the central plane <NUM>. It would of course be possible to combine the approaches of <FIG> and <FIG> by varying the angle of the facets <NUM> relative to the side faces <NUM> and by varying the thicknesses of the plates <NUM> in accordance with the distance from the central plane <NUM>.

Moving on to <FIG>, this shows a variant in which the housing <NUM> is not fixed rigidly but can instead pivot relative to the hang-off bushing <NUM>. For example, the housing <NUM> can be mounted to the hang-off bushing <NUM> via elastomeric mounts <NUM>, gimbals or other pivot arrangements. Pivotal movement of the housing <NUM> may thereby be permitted about horizontal and/or vertical axes. This allows the housing <NUM> to realign to reorient the block <NUM> when compensating for slight misalignment between the launch axis <NUM> and the hang-off system. Movement of the housing <NUM> relative to the hang-off bushing <NUM> can be passive in response to the block <NUM> encountering the fitting <NUM> or can be active, in the sense of being driven by actuators to compensate for misalignment between the launch axis <NUM> and the hang-off system.

Turning finally to <FIG>, this shows that the plates <NUM> need not necessarily only move in horizontal directions orthogonal to the launch axis <NUM>. Here, the housings <NUM> and the plates <NUM> are tilted downwardly toward the launch axis <NUM>, for example to use gravity to assist deployment of the plates <NUM> from the housings <NUM>.

The plates <NUM> may also tilt, or be driven to tilt, in vertical planes to compensate for slight tilting of the supported part or poor planarity of the interface. For example, blocks <NUM> or plates <NUM> on one side of the launch axis <NUM> could be tilted slightly downwardly and blocks <NUM> or plates <NUM> on an opposite side of the launch axis <NUM> could be tilted slightly upwardly, potentially with matching inclination to the horizontal. Another approach to this issue would be to lower a block <NUM> and/or to raise a block <NUM> relative to other blocks <NUM> to compensate for a slightly misaligned pipeline.

Many other variations are possible within the inventive concept. For example, the plates <NUM> need not be in sliding contact with each other and/or with the housing <NUM> and could be supported for movement in another way, for example on individual rails or individual bearings. Indeed, the housing <NUM> may not be necessary if the plates <NUM> are supported in a different way, for example with individual supports. Also, the plates <NUM> need not necessarily be parallel and could, for example, converge on the launch axis <NUM> in plan view while remaining in substantially vertical planes.

Claim 1:
A hang-off system comprising at least one support block (<NUM>) that is movable forwardly toward a launch axis (<NUM>) for engagement with an elongate element (<NUM>) being laid from a vessel into water, wherein:
the or each support block (<NUM>) comprises an array of plates (<NUM>) that together define an engagement face of the support block and are movable relative to each other to conform a contour of the engagement face to a contour of the element;
each plate (<NUM>) comprises mutually parallel upright side faces (<NUM>) joined by an upper (<NUM>) face that is narrower than either of the side faces of that plate; and
the upper faces (<NUM>) of the plates together define an upper face of the support block (<NUM>).