Abstract:
The invention provides improvements to the tensioner pads ( 513 ) which engage with the surface of elongate articles in tensioners such as used on offshore pipelaying and construction vessels to deploy products such as pipelines, cables and umbilicals, wherein tensioner pad assemblies ( 511 ) according to the invention may include; two or more tensioner pads and present a first tensioner pad to the product when in a first configuration and present a second tensioner pad to the product when in a second configuration; a split tensioner pad with a means ( 525 ) for controlling the separation between the portions ( 513   i   ,513   ii ) of the pad; and combinations thereof. The invention allows a tensioner to accommodate products of different shapes, sizes and materials without having to swap tensioner pad assemblies.

Description:
[0001]    The present invention relates to the field of tensioners such as used on offshore pipelaying and construction vessels to deploy elongate articles such as pipelines, cables and umbilicals. More specifically, the present invention concerns improvements to the tensioner pads which engage with the surface of elongate articles in track type tensioners and elements thereof. In a particular embodiment of the invention there is provided a tensioner pad assembly having a split tensioner pad with a means for controlling the separation between the portions of the pad to accommodate elongate articles of different diameters. 
       BACKGROUND TO THE INVENTION 
       [0002]      FIG. 1  illustrates in schematic form a typical pipelaying vessel  101  for laying product  103 , such as submarine oil or gas pipes, flexible pipelines and risers, electrical or umbilical cables, from an integrated deck-mounted reel  105 . The optimum lay speed and other process parameters are dependent on many factors such as vessel speed, sea state, product characteristics and water depth. Lay speed is regulated by one or more tensioners  107  whose speed is coordinated with the speed of rotation of the reel  105 . 
         [0003]    Further detail of a typical tensioner arrangement  207  is illustrated in  FIG. 2 . The product  203  is gripped between opposing tracks  209 , each of which comprises several tensioner pads  211  mounted on a chain (not shown). A dedicated drive system  213  operates the tensioner  207  in a forward or reverse mode to drive or brake deployment of the product—for example at the initial deployment stage the tensioner  207  is driven in a forward mode to drive the product  203  through the system and into the water and once the weight of the product exceeds the forces necessary to drive the product a braking force is applied to maintain control of the running of the product. 
         [0004]    Typically, the pads  211  comprise natural or synthetic rubber, polyurethane or steel, whereas the product  203  (or at least the outer surface of the product  203 ) comprises bare steel coated with corrosion resistant and insulation coatings such as Fusion Bonded Epoxy, Polyethylene, Polypropylene or Glass Syntactic Polyurethane. The surfaces of the pads  211  and/or of the product  203  may be smooth or textured for grip. 
         [0005]    A controlled squeeze pressure (on the product) is applied via the tensioner tracks  209  by biasing apparatus  215 . The resulting coefficient of friction between the pads  211  and the product  203  is dependent on the material of the pads  211  and of the product  203 , the surface of the pads  211  and of the product  203  and any texture thereon, and particularly the pressure between the surfaces which is dependent on the area of contact there between. 
         [0006]      FIG. 3  illustrates in schematic form three different types of pad  311 ; (a) with a small rubber pad portion  313   a  with a curved surface corresponding to a small product  303   a  represented in two-track mode typical of umbilical installation, (b) a large rubber pad portion  313   b  with a curved surface corresponding to a large product  303   b  represented in 4 track mode typical of rigid pipeline installation, and (c) a steel pad portion  313   c  with a v-shaped surface represented in 4 track mode typical of flexible pipeline installation. To optimise the coefficient of friction for specific lay projects, it will be understood that different pad materials and shapes must be used for different products. It is therefore necessary to change the pads on the tensioners when there is a significant change in product diameter, coating material or if installation parameters so dictate. Several such tensioner pad changes may occur during a pipelay campaign or indeed during a single pipelay trip. 
         [0007]      FIG. 4  illustrates in more detail a tensioner pad  413 , which is either directly connected to the tensioner chain  417  or mounted to a spring base which is attached to the tensioner chain  417  of the tensioner track (not shown but as previously illustrated). The spring base located between the tensioner pad  413  and the tensioner chain  417  comprise a number of spring elements  419  which provide resilience and bias the pad  413  towards the product  403 . Whether by selection of an appropriate material for the pad  413  and/or inclusion of such biasing means as said springs  419  the pad assembly  411  overall should be compliant to allow the pads to compress and/or retract so that changes in the diameter of the product can be accommodated. The diameter changes may arise from product outer diameter variations due to manufacturing tolerances, the presence of field joint coatings, diameter steps or transitions from one diameter to another. 
         [0008]    Nonetheless, flexibility is still significantly limited and tensioner pads must be changed for different product diameters or diameter variations for a single product, different load requirements and different product materials and surface finishes. Replacing pads with pads of another design or different performance can take in the region of 16 to 24 hours for each tensioner, and can only take place when the lay process is stopped. As the daily cost of running a pipelaying vessel is typically in the region of $500,000, taking the vessel out of operation for pad changeover has significant cost implications. Furthermore, packing and storage space on deck and handling are required for the tensioner pads that are not in use, and many different sets of pads are required to accommodate a full range of product sizes and materials. 
         [0009]    These problems are common to all operators involved in the laying or handling of more than one product specification with the same tensioner. 
         [0010]    Accordingly, it is an object of at least one aspect of the present invention to provide a tensioner pad assembly that reduces the requirement for an operator to carry multiple tensioner pads for different applications. 
         [0011]    Further aims and objects of the invention will become apparent from reading the following description. 
       SUMMARY OF THE INVENTION 
       [0012]    According to a first aspect of the invention there is provided a tensioner pad assembly for a track type tensioner, the tensioner pad assembly comprising a plurality of tensioner pads and configured to present a first of the tensioner pads to a product when in a first configuration and present a second of the tensioner pads to the product when in a second configuration. 
         [0013]    The above invention provides a means for accommodating different products which require different pads, e.g. different shapes, different sizes or different materials, without having to remove one set of tensioner pad assemblies to replace them with another set of tensioner pad assemblies. Again, product will be understood to relate to any suitable lay product. 
         [0014]    Most preferably, the second of the tensioner pads is held in a storage position when the tensioner pad assembly is in the first configuration, and/or vice versa. Optionally, the tensioner pad assembly comprises one or more supports configured to locate and/or support the first or second tensioner pad when in the storage position. Optionally, the one or more supports comprise a flexible, resilient and/or compressible material. Alternatively, the tensioner pad assembly may be arranged such that the tensioner pads themselves provide the tensioner pad assembly with flexibility, resilience and/or compressibility. 
         [0015]    Preferably two or more tensioner pads are mounted on opposing faces of one or more corresponding pad carriers. Optionally, the pad carriers are plates. 
         [0016]    Preferably, the tensioner pad assembly comprises a mounting frame, the mounting frame providing a means for translating the tensioner pad assembly between the first configuration and the second configuration. To this end, the mounting frame may comprise one or more arms or linkages, to which the tensioner pads or corresponding pad carriers are connected. Preferably, the one or more tensioner pads or corresponding pad carriers are hingedly mounted on the mounting frame via one or more arms or linkages. 
         [0017]    Most preferably, the mounting frame further provides a means for attaching the tensioner pad assembly to a tensioner. Optionally, the mounting frame is connectable directly to a chain or track of a tensioner. 
         [0018]    In a preferred embodiment of the first aspect of the invention, the tensioner pad assembly comprises four tensioner pads, and is configured to present a first of the tensioner pads to the product when in a first configuration, a second of the tensioner pads to the product when in a second configuration, a third of the tensioner pads to the product when in a third configuration, and the fourth of the tensioner pads to the product when in a fourth configuration. 
         [0019]    Preferably, the first and second tensioner pads are mounted on a first pad carrier, which may be a plate, and the third and fourth tensioner pads are mounted on a second pad carrier, which may also be a plate. 
         [0020]    Optionally, the tensioner pad assembly further comprises one or more supports configured to locate and/or support the remaining tensioner pads when one of the tensioner pads is presented to the product, and optionally provide the tensioner pad assembly with flexibility, resilience and/or compressibility. Alternatively, or additionally, the tensioner pad assembly is arranged such that the remaining tensioner pads provide the tensioner pad assembly with flexibility, resilience and/or compressibility. 
         [0021]    According to a second aspect of the invention there is provided a tensioner pad assembly for a track type tensioner, the tensioner pad assembly comprising a plurality of tensioner pads and configured to present a first of the tensioner pads to a product when in a first configuration and present a second of the tensioner pads to the product when in a second configuration, and one or more of the tensioner pads comprising a first pad portion, a second pad portion, and a separating means arranged to control a separation between the first pad portion and the second pad portion. 
         [0022]    Embodiments of the second aspect of the invention may comprise features corresponding to the preferred or optional features of the first aspect of the invention or vice versa. 
         [0023]    According to a third aspect of the invention, there is provided a tensioner pad assembly for a track type tensioner, the tensioner pad assembly comprising a tensioner pad comprising a first pad portion, a second pad portion, and a separating means arranged to control a separation between the first pad portion and the second pad portion. 
         [0024]    The above invention provides a means for accommodating different product diameters without requiring multiple separate tensioner pad assemblies. In conventional pipe lay systems, when switching from a small pipe diameter to a large pipe diameter, it is usually necessary to replace all of the tensioner pads in the pipe tensioner. However, the invention allows the same tensioner pads to be used by increasing (or decreasing) the separation between discrete portions of a single tensioner pad. A track type tensioner may be a pipe tensioner used in the handling or laying of pipes or for other elongate articles such as umbilicals and cables. 
         [0025]    Optionally, the separating means permits continuous adjustment of the separation between the first and second pad portions. 
         [0026]    Optionally, the separating means comprises one or more threaded rods. Preferably, the separating means comprises at least one threaded rod extending between the first pad portion and second pad portion. Alternatively, the separating means comprises one or more hydraulic cylinders. Further alternatively, the separating means comprises one or more linear positioners, such as micrometers. 
         [0027]    Alternatively, the separating means permits discrete adjustment of the separation between the first and second pad portions. 
         [0028]    Optionally, the separating means comprises a number of apertures in positions corresponding to different separations between the first pad portion and the second pad portion, the apertures adapted to receive at least one retaining member which holds the first pad portion and the second pad portion at the corresponding separation. The retaining member may, for example, be a rod or a threaded bolt. 
         [0029]    Still further alternatively, the separation means comprises a number of slots in the first and second pad portions which define a corresponding number of separations, and at least one retaining member adapted to be received in one or more of the slots to hold the first and second pad portions at the corresponding separation. Optionally, the retaining member comprises a rod. Preferably, the rod is pivotally mounted in the tensioner pad assembly. Preferably, the rod is pivotally mounted at a first end and is adapted to receive a retaining member at a second end. 
         [0030]    Alternatively, the separating means comprises one or more hydraulic cylinders. Further alternatively, the separating means comprises one or more linear positioners, such as micrometers. 
         [0031]    Preferably, the first pad portion, the second pad portion and/or a plate supporting the first and second pad portions comprise corresponding channels or grooves to align and/or guide the first and second pad portions when moved by the separating means. 
         [0032]    Optionally, the pad portions are provided with inclination adjustment means to control the inclination of a contact surface of the pad portions. Preferably, the inclination adjustment means comprises one or more rotatable discs having at least a one sloping face contacting a surface of the pad portion. The sloping face is preferably an upper face contacting a lower face of the pad portion, or alternatively is a lower face contacting a plate or pad carrier. Preferably, a plurality of rotatable discs are interconnected so as to transfer rotation from one disc to the next. The rotatable discs may be rotated using a removable key, via a worm drive, or other equivalent means. 
         [0033]    In a preferred embodiment of the third aspect of the invention, the inclination adjustment means is configured to adjust between a pad angle (i.e. the angle between contacting faces of the pad portions) of  140  degrees and a pad angle of  160  degrees. 
         [0034]    Embodiments of the third aspect of the invention may comprise features corresponding to the preferred or optional features of the first or second aspects of the invention or vice versa. 
         [0035]    According to a fourth aspect of the invention there is provided a tensioner comprising a plurality of tracks, each of the tracks comprising a plurality of tensioner pad assemblies according to the first, second and/or third aspects. 
         [0036]    Embodiments of the fourth aspect of the invention may comprise features corresponding to the preferred or optional features of the first, second or third aspects of the invention or vice versa. 
         [0037]    According to a fifth aspect of the invention there is provided a method of reconfiguring the tensioner of the fourth aspect comprising adjusting the separation between the first pad portion and the second pad portion of the first or third aspect, or translating the tensioner pad assembly of the second or third aspect between one configuration and another configuration, in order to accommodate a particular product. 
         [0038]    Embodiments of the fifth aspect of the invention may comprise features corresponding to the preferred or optional features of the first to fourth aspects of the invention or vice versa. 
         [0039]    According to a sixth aspect of the invention there is provided a method of laying a product comprising driving or braking the tracks of a tensioner according to the fourth aspect to control the speed at which the product is deployed. 
         [0040]    Embodiments of the sixth aspect of the invention may comprise features corresponding to the preferred or optional features of the first to fifth aspects of the invention or vice versa. 
         [0041]    According to a seventh aspect of the invention, an existing track type tensioner can be retrofitted by replacing existing tensioner pads with tensioner pad assemblies according to any of the first to third aspects of the invention. 
         [0042]    The existing tensioner pads may already have been removed; otherwise the existing tensioner pads may first be removed prior to fitting the inventive tensioner pad assemblies. 
         [0043]    Embodiments of the seventh aspect of the invention may comprise features corresponding to the preferred or optional features of the first to sixth aspects of the invention or vice versa. 
         [0044]    According to another aspect of the invention, there is provided a tensioner pad assembly for a track type tensioner, a tensioner comprising one or more tensioner pad assemblies, a method of reconfiguring such a tensioner, or a method of laying a product using such a tensioner, substantially as herein described with reference to  FIGS. 5 to 20 . 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0045]    Aspects and advantages of the present invention will become apparent upon reading the following detailed description and upon reference to the following drawings (like reference numerals referring to like features) in which: 
           [0046]      FIG. 1  is a schematic representation of a typical pipelay vessel according to the prior art; 
           [0047]      FIG. 2  is a schematic representation of a typical track type pipe tensioner according to the prior art; 
           [0048]      FIG. 3  is a schematic representation of a number of typical tensioner pads according to the prior art; 
           [0049]      FIG. 4  is a schematic representation of a typical tensioner pad mounting arrangement according to the prior art; 
           [0050]      FIG. 5  is a schematic representation of a tensioner pad assembly according to an embodiment of the present invention; 
           [0051]      FIG. 6  is a schematic representation illustrating two tensioner pad assemblies according to an embodiment of the invention gripping a pipe; 
           [0052]      FIG. 7  is a schematic representation illustrating the pipe diameter adjustment achievable using the lateral separation adjustment mechanism of the tensioner pad assembly of  FIG. 5 ; 
           [0053]      FIG. 8  is a schematic representation illustrating the tensioner pad assembly of  FIG. 5  replacing typical tensioner pads according to the prior art in a pipe tensioner track; 
           [0054]      FIG. 9  is a schematic representation illustrating a tensioner pad assembly with an alternative arrangement for adjusting the lateral separation of the tensioner pad portions; 
           [0055]      FIG. 10  is a schematic representation illustrating a tensioner pad assembly with a further alternative arrangement for adjusting the lateral separation of the tensioner pad portions; 
           [0056]      FIG. 11  is a schematic representation of an alternative tensioner pad assembly according to another embodiment of the present invention; 
           [0057]      FIG. 12  is a schematic representation of the tensioner pad assembly of  FIG. 11  in a number of different configurations according to an embodiment of the present invention; 
           [0058]      FIG. 13  is a schematic representation illustrating a tensioner pad assembly according to an alternative embodiment of the present invention; 
           [0059]      FIG. 14  is a schematic representation illustrating a tensioner pad assembly according to another alternative embodiment of the present invention; 
           [0060]      FIG. 15  is a schematic representation illustrating a tensioner pad assembly according to a further alternative embodiment of the present invention in a first configuration; 
           [0061]      FIG. 16  is a schematic representation illustrating the tensioner pad assembly of  FIG. 15  moving between the first configuration and a second configuration; 
           [0062]      FIG. 17  is a schematic representation illustrating two tensioner pad assemblies of  FIG. 15  and  FIG. 16  gripping a pipe in the second configuration; 
           [0063]      FIG. 18  is a schematic representation illustrating detail of the angular adjustment mechanism of the tensioner pad assembly of  FIG. 15  and  FIG. 16 ; 
           [0064]      FIG. 19  is a schematic representation illustrating further detail of the angular adjustment mechanism detailed in  FIG. 18 ; and 
           [0065]      FIG. 20  is a schematic representation illustrating the angular adjustment effected by the angular adjustment mechanism shown in  FIG. 18  and  FIG. 19 . 
       
    
    
     DETAILED DESCRIPTION 
       [0066]    As discussed in the background to the invention above, operators are required to carry multiple tensioner pads to accommodate different products, different product sizes, different product materials and different product configurations. An embodiment of the present invention is illustrated in  FIG. 5  which overcomes this problem with the prior art. An improved tensioner pad assembly  511  is shown which comprises a tensioner pad  513  which itself comprises two separate pad portions  513   i , 513   ii  which are moveable laterally across the face of pad plate  514  to adjust the separation there between. The separation is controlled by way of a threaded rod  525  which extends between the pad portions  513   i , 513   ii  and is accessible, and therefore may be adjusted, from the side. Rotation of the threaded rod  525  in a first direction causes the pad portions  513   i , 513   ii  to move apart and rotation of the threaded rod  525  in the opposite direction causes the pad portions  513   i , 513   ii  to move together. The pad portions  513   i , 513   ii  comprise elongate fingers which are received in corresponding grooves in the pad plate  514 , aligning and guiding the pad portions  513   i , 513   ii  during adjustment. In  FIG. 5 , the pad plate  514  is mounted on a spring base  517  which comprises a number of springs  519  which provide resilience and bias the tensioner pad  513  towards the product. The spring base  517  is mountable on the chain  512  of a tensioner track  509  as illustrated in  FIG. 8 , which shows a number of tensioner pad assemblies  511  according to the present invention. 
         [0067]      FIG. 6  shows two such improved tensioner pad assemblies  511  disposed on either side of a product  503 . The pad portions  513   i , 513   ii  have been set at a separation suitable for the diameter of the product  503 . However, as above, the separation of the pad portions  513   i , 513   ii  can be adjusted and this allows a single tensioner pad assembly  511  to accommodate different product diameters.  FIG. 7  illustrates how accommodating a relatively minor pad portion travel allows for a significant range of product diameters to be handled. For example, within a travel of 70 mm, pipe diameters between 190 mm and 420 mm can be accommodated—without the need to change pads. The dashed lines indicate the position of the pad portions  513   i , 513   ii  for a 190 mm diameter product and the solid lines indicate the position of the pad portions  513   i , 513   ii  for the larger 420 mm product. 
         [0068]    The applicant has realised that in the case of conventional tensioner pads (and particularly those of a v-shape), as product diameter increases the points of contact between the product and the pad move outward. Rather than having to change to larger pads as larger products are deployed, the applicant has proposed that the one-piece pad be replaced with a two-piece pad, said pieces being moveable apart from (or towards) one another to offer adequate contact with the product where it is needed (and where it would have been provided by an appropriately selected single continuous pad)—saving on material costs on what would otherwise be a substantially larger pad for a large diameter pipe, without the interference between neighbouring pads that would otherwise limit how small a diameter of product could be accommodated. 
         [0069]    An alternative tensioner pad assembly  611  is illustrated in  FIG. 9 , and illustrates an alternative arrangement for adjusting or setting the separation between the pad portions  613   i , 613   ii . As described above, the pad portions  613   i , 613   ii  comprise elongate fingers which are received in corresponding grooves in the pad plate  614 , aligning and guiding the pad portions  613   i , 613   ii  during lateral adjustment. In this embodiment, each of these fingers comprises an aperture  626  which can receive a pin, rod, bolt or the like. A number of corresponding apertures (not visible) are provided in the pad plate  614  and allow the pad portions  613   i , 613   ii  to be fixed—by insertion of a pin, rod, bolt or the like through the apertures  626  in the fingers and into the apertures in the pad plate  614 .  FIGS. 6(   a )-( c ) show three separate pad configurations which correspond to three different sets of apertures in the pad plate  614 . 
         [0070]    Of course, there need not be apertures in the pad plate  614  and/or instead of receiving the pins, rods, bolts or the like in such apertures the separation could be set by use of a bolt or the like which is urged into frictional contact with the pad plate  614  (through the apertures in the fingers of the pad portions  613   i , 613   ii ) to hold the pad portions  613   i , 613   ii  in place. 
         [0071]    A further alternative tensioner pad assembly  711  is illustrated in  FIG. 10 , in which one of the pad portions has been made invisible for the purposes of illustration. Pad portion  713   i  can be seen, as in previously described embodiments, fingers which are received in and guided by corresponding grooves in the pad plate  714 . In this particular embodiment, a rod  728  is hingedly attached at one end and is received in a corresponding slot  729  in the pad plate  714  which extends across the grooves and the fingers. Each of the fingers is provided with a number of slots  726  which can be aligned with the slot  729  in the pad plate  714  such that there is a continuous slot into which the rod  728  can be lowered. Selection of a different finger slot  726  will provide a different separation between the pad portions. In this embodiment, there are provided three slots  729  however any number of slots can be provided to provide the desired range of pad separations to accommodate a desired range of product diameters. When lowered, the rod  728  can be retained by a pin, rod, bolt or the like. 
         [0072]    Although a number of specific arrangements for adjusting, controlling and setting the separation of the pad portions are described above (and below), it will be understood that any arrangement for adjusting, controlling and/or setting the separation of the pad portions will allow the benefits of the invention to be realised. 
         [0073]    Another embodiment of the present invention is illustrated in  FIG. 11 . An improved tensioner pad assembly  811  is shown which comprises four separate tensioner pads  813   a , 813   b , 813   c , 813   d  of different configurations to accommodate different products  803 . In this particular embodiment, pads  813   a  and  813   b  are mounted on opposite faces of a first pad plate  814   a,  and pads  813   c  and  813   d  are mounted on opposite faces of a second pad plate  814   b.    
         [0074]    Each pad plate  814   a  and  814   b  is mounted such that it can be flipped to present a different tensioner pad  813   a  or  813   b,    813   c  or  813   d  (respectively) towards the product  803 . Furthermore, the pad plates  814   a , 814   b  are so mounted that they may change places, the result being that the improved tensioner pad assembly  811  can be configured and repeatedly reconfigured so as to provide the effect of having four separate tensioner pads but without requiring the removal and replacement in order to accommodate different lay products. 
         [0075]    In the illustrated embodiment, the plates  814   a , 814   b  are connected to the attachment  817  by way of a number of arms or linkages (indicated by reference number  821 ) which permit flipping and rotation of the plates  814   a , 814   b  while retaining the plates  814   a , 814   b  within a compact arrangement. However, it will be recognised that a number of alternative arrangements may be employed to realise the flipping and/or reversal of the tensioner pads  813   a , 813   b , 813   c , 813   d —for example the plates  814   a , 814   b  could be connected or attached to one another and/or to the attachment  817  by clips which are unclipped and reclipped once the plates  814   a , 814   b  have been flipped and/or swapped round. 
         [0076]      FIG. 12  illustrates, again in schematic form, the different tensioner pad configurations that can be realised using the improved tensioner pad assembly  811  illustrated in  FIG. 11 , which allows the single device of the invention to accommodate four different lay products  803   a,    803   b,    803   c  and  803   d.  In this embodiment, four different sizes of a similar product can be accommodated by providing different sized pads; it is also envisaged that pads of same or similar size but comprising different materials and/or different shapes (e.g. v-shapes) could be employed to accommodate same size but different material products.  FIG. 14  illustrates how the plates and pads may be flipped and/or swapped using the above-mentioned arms or linkages. 
         [0077]    As illustrated in  FIG. 4  and described in the background to the invention, it is beneficial to employ springs (e.g.  419 ) in tensioner pad assemblies to provide resilience and flexibility to accommodate changes in product diameter as it is laid. In the embodiment of the invention illustrated in  FIGS. 11 and 12 , the same functionality may be provided by employing optional supports or spacers  823  disposed between the plates  814   a  and  814   b  and between the lowermost plate  814   a  or  814   b  and the attachment  817 . These spacers  823  not only help to locate and hold the plates  814   a  and  814   b  (and of course the attached tensioner pads  813   a , 813   b , 813   c , 813   d ) relative to one another and/or provide structural support to the improved tensioner pad assembly  811 , but if the spacers  823  are comprised of a flexible, resilient and/or compressible material they may act in a similar manner as the springs and allow radial (with respect to a cross-section of the product) displacement of the pad  813   a , 813   b , 813   c , 813   d  presented to the product  803   a , 803   b , 803   c , 803   d  (respectively). 
         [0078]    As shown in  FIG. 13 , an improved tensioner pad assembly  911  according to the invention can be provided with such functionality without the need for two spacers, and this can be achieved with one spacer  923  disposed between the plates  914   a , 914   b.  In fact, this spacer  923  can be solid, and the resilience, flexibility and/or compressibility required to allow radial displacement of the outermost pad ( 913   a  in this embodiment) provided by the combined or aggregated resilience, flexibility and/or compressibility of the four tensioner pads  913   a , 913   b , 913   c , 913   d.  Of course, it will be realised that this can be achieved even without the provision of one or more spacers. 
         [0079]      FIG. 13  also illustrates (most evident in the side view) an alternative to the arrangement of arms or linkages (indicated by reference number  921 ) to that presented in  FIG. 11 , which also allows for the flipping and/or swapping of pad plates  914   a , 914   b.    
         [0080]    While the invention has been demonstrated by way of examples showing four different tensioner pads, it will be recognised that the benefits of the invention can be realised with any number of tensioner pads greater than one (for example, two as illustrated in the following embodiment). However, it is envisaged that an embodiment comprising a single tensioner pad may still benefit from the inventive concept by allowing the corresponding plate to be flipped to protect the tensioner pad and outwardly present a blank face of the plate. This configuration might be employed during transport, and the plate(s) flipped when the corresponding tensioner is to be used. 
         [0081]    A further alternative embodiment of the invention is presented in  FIG. 15 , which illustrates an improved tensioner pad assembly  1011  comprising two tensioner pads  1013   a , 1013   b  mounted on opposite faces of a single pad plate  1014 . The pad plate  1014  is flippable to present either tensioner pad  1013   a , 1013   b  towards the lay product (not shown in  FIG. 15 ), by way of arms  1021  which are pivotally mounted to the pad plate  1014  at one end and pivotally mounted to the attachment  1017  (which is in turn attached to the track chain—not shown—of a pipe tensioner) to allow reversal of the pad plate  1014  as illustrated in  FIG. 16  (which shows an intermediate stage in the flipping/reversal process). 
         [0082]    Similarly to the tensioner pad  513  described above in relation to  FIG. 5 , the tensioner pads  1013   a , 1013   b  can be seen to comprise distinct and separate pad portions  1013   ai , 1013   aii  and  1013   bi , 1013   bii  (respectively). The pad portions  1013   ai , 1013   aii , 1013   bi , 1013   bii  are moveable laterally across the faces of the pad plate  1014  so as to adjust the separation there between. The separation is adjusted and/or controlled by way of threaded rods  1025   a , 1025   b  mounted on or in the pad plate  1014  and extending through both of the pad portions  1013   ai , 1013   aii  and  1013   bi , 1013   bii  (respectively).
       Rotation of the threaded rods  1025   a  and  1025   b  in a first direction causes the pad portions  1013   ai , 1013   aii  and  1013   bi , 1013   bii  to move apart and rotation of the threaded rods  1025   a  and  1025   b  in a second direction (opposite sense to the first) causes the pad portions  1013   ai , 1013   aii  and  1013   bi , 1013   bii  to move towards one another. Of course the threaded rods  1025   a , 1025   b  can be operated independently of one another, although they could be linked. Corresponding channels or grooves on contacting surfaces of the pad plate  1014  and the pad portions  1013   ai , 1013   aii  and  1013   bi , 1013   bii  align and/or guide the pad portions  1013   ai , 1013   aii  and  1013   bi , 1013   bii  during movement to prevent twisting.       
 
         [0084]    In a similar manner, the contacting faces of the pad plate  1014 , arm  1021  and attachment  1017  (see region marked “A”) have corresponding channels or grooves to aid in alignment and to prevent twisting and/or displacement of the arms either during flipping (such as shown in  FIG. 16 ) or when fixed in position in a first configuration (with tensioner pad  1013   a  presented to the product) or a second configuration (with tensioner pad  1013   b  presented to the product—such as shown in  FIG. 15 ). 
         [0085]    In a similar arrangement to that illustrated in  FIG. 6 ,  FIG. 11  illustrates two such improved tensioner pad assemblies  1011  disposed on either side of a product  1003 . Comparing the configuration of the tensioner pad portions  1013   ai  and  1013   aii  in  FIG. 17  to the configuration of the tensioner pad portions  1013   ai  and  1013   aii  in  FIGS. 15 and 16 , it can be seen that they have been brought closer together in order to accommodate a product  1003  of relatively small diameter. 
         [0086]    The improved tensioner pad assemblies  1011  shown in  FIG. 17  can also be flipped so as to present the similarly configured, but having larger tensioner pad portions  1013   bi  and  1013   bii , tensioner pads  1013   b.  Such improved tensioner pad assemblies  1011  can therefore accommodate a first range of product diameters with first tensioner pads  1013   a  and a second range of product diameters with second tensioner pads  1013   b.    
         [0087]    Accordingly, with a single improved tensioner pad assembly in accordance with such an embodiment of the invention, pipe diameters between (say) 100 mm and 630 mm can be accommodated—again without the need to change pads. In conventional arrangements, at least three or four sets of pads would be required to achieve the same operational range—without the flexibility to ensure intermediate product sizes are provided with the same support as can be provided by the moveable pad portions  1013   ai , 1013   aii  and  1013   bi , 1013   bii.    
         [0088]    As noted above, the skilled person will readily appreciate that any manner or means of adjusting and/or controlling the separation of the pad portions may be employed, and that the provision of a threaded rod as illustrated on  FIGS. 15 to 17  is simply one realisation. The pad portions may instead be positioned using one or more hydraulic cylinders (aka pistons) or the like, using linear positioners such as micrometers, or other equivalent means. 
         [0089]    It will of course also be clear from the present disclosure that the benefits of the adjustable and/or controllable pad portion separation can be realised separately from the benefits of the flipping pad plate; accordingly, it will be understood that the invention finds utility in tensioner pad assemblies consisting of a single tensioner pad—although for the purposes of illustrating the invention it is helpful to describe the additional and combined benefits of having adjustable and/or controllable pad portion separation and being able to accommodate two or more different such tensioner pads in a single tensioner pad assembly. Furthermore, it will be realised that any number of such adjustable and/or controllable tensioner pads can be employed in a single improved tensioner pad assembly according to the present invention; for example four such tensioner pads could be employed in an improved tensioner pad otherwise substantially as described with reference to  FIGS. 11 to 14 . 
         [0090]      FIGS. 18 and 19  show further detail of pad portion  1013   aii  which has been adapted to provide additional adjustment to the angle of the by way of multiple inclined circular discs  1027 . Rotation of these discs, which in this particular embodiment are interconnected, allow adjustment of the angle between opposing pad portions  1013   aii  and  1013   ai  between (for example) 140 degrees and 160 degrees (as shown in  FIG. 20 ). In this embodiment, the discs comprise a keyed hole  1029  into which a corresponding key can be inserted to effect the required rotation. If interconnected, only one of the discs needs to be rotated. Of course, other means of effecting rotation can be employed, for example the use of a longitudinal worm drive—in which case the discs in opposing pad portions can be driven at the same time and by the same amount. Appropriate selection of pad shape and disc size and slope angle may provide different and/or lesser or greater operational ranges. 
         [0091]    Note that in  FIGS. 18 and 20  the discs  1027  are shown as having sloping upper faces whereas in  FIG. 19  the discs  1127  have flat upper faces but sloping lower faces (not visible) which will be understood to provide the same effect. 
         [0092]    Accordingly, when combined with the previously described embodiments, the invention may provide a single improved tensioner pad that is not only capable of handling pipe diameters ranging from (for example) 100 mm to 630 mm, but able to provide v-angles ranging between (for example) 140 degrees and 160 degrees—again without having to change tensioner pads. Currently, one would expect that such operational flexibility could only be obtained with at least 7 different sets of tensioner pads—and these would in any case still not be capable of adjustment to accommodate intermediate pipe diameters and/or different desired v-angles. 
         [0093]    There are several benefits that the claimed invention in its varied embodiments (examples of which are described above) provide in relation to the prior art. For example, once a track-type pipe tensioner has been retro-fitted with the inventive tensioner pad assemblies it may be that the tensioner pads need never be changed again, other than to remedy wear and tear, yet the pipe tensioner will still be able to accommodate the full range of pipe product diameters and materials for a particular job or series of jobs. There is also a significant space saving because multiple sets of tensioner pads do not need to be stored on the vessel, other than any spares that are deemed appropriate to carry. Furthermore, it is expected that a full set of tensioner pad assemblies, according to the invention, can be reconfigured (by flipping, adjusting pad portion separation and/or pad portion angle) in around  3  hours which is significantly less vessel down-time and also allows the changeover to be performed during a single operating shift by a single team which has benefits in consistency as well. Knock-on benefits follow in scheduling, because the changeover times are so much shorter. 
         [0094]    There are also safety benefits as there are no loose parts and manual handling of heavy parts is not necessary, and a corresponding reduced risk of dropping components and the damage and/or injury that such accidents can involve. 
         [0095]    In particular embodiments, pad rubbers which are not in contact with the product being laid provide additional compliance to the tensioner pad overall which not only compensates for the lack of spring blocks used by the prior art (although spring blocks can be employed without departing from the scope of invention) but in actual fact may be more effective than spring blocks. 
         [0096]    Throughout the specification, unless the context demands otherwise, the terms ‘comprise’ or ‘include’, or variations such as ‘comprises’ or ‘comprising’, ‘includes’ or ‘including’ will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers. 
         [0097]    The foregoing description of the invention has been presented for the purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed. The described embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilise the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore, further modifications or improvements may be incorporated without departing from the scope of the invention as defined by the appended claims.