GB2538569A - Tensioner pad attachment - Google Patents

Abstract

A means for attaching tensioner pads to tensioners in a robust and reliable manner which also provides for quick and convenient removal and replacement comprises replacing conventional attachment arrangements such as permanent or semi-permanent bolting arrangements or retaining pin and safety pin arrangements with a magnetic attachment arrangement. Magnetic bosses 525 are provided on an interface plate 517 which can be permanently or semi-permanently attached to the tensioner chain or track, and they are received in corresponding recesses 529 on a base plate 527 of the tensioner pad 511.The magnetic bosses 525 can comprise permanent or rare earth magnets 531, such as neodymium or samarium-cobalt magnets. The magnets 531 are used to attach the tensioner pad 511 to a track or train. The magnets 531 can be retained in the bosses with use of a resin and/or a cap which may be bolted to the boss 525 through the magnet 531.

Description

1 Tensioner Pad Attachment 3 The present invention relates to the field of tensioners such as used on offshore pipelaying 4 and construction vessels to deploy elongate articles such as pipelines, cables and umbilicals. More specifically, the present invention concerns improvements to the 6 attachment of the tensioner pads, which engage with the surface of elongate articles in 7 track type tensioners, to the chains or tracks of the tensioners.

9 Background to the invention

11 Figure 1 illustrates in schematic form a typical pipelaying vessel 101 for laying product 12 103, such as submarine oil or gas pipes, flexible pipelines and risers, electrical or umbilical 13 cables, from an integrated deck-mounted reel 105. The optimum lay speed and other 14 process parameters are dependent on many factors such as vessel speed, sea state, 1 product characteristics and water depth. Lay speed is regulated by one or more 2 tensioners 107 whose speed is coordinated with the speed of rotation of the reel 105.

4 Further detail of a typical tensioner arrangement 207 is illustrated in Figure 2. The product 203 is gripped between opposing tracks 209, each of which comprises several tensioner 6 pads 211 mounted on a chain (not shown). A dedicated drive system 213 operates the 7 tensioner 207 in a forward or reverse mode to drive or brake deployment of the product - 8 for example at the initial deployment stage the tensioner 207 is driven in a forward mode to 9 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 11 maintain control of the running of the product.

13 Typically, the pads 211 comprise natural or synthetic rubber, polyurethane or steel, 14 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 16 Epoxy, Polyethylene, Polypropylene or Glass Syntactic Polyurethane. The surfaces of the 17 pads 211 and/or of the product 203 may be smooth or textured for grip.

19 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 21 product 203 is dependent on the material of the pads 211 and of the product 203, the 22 surface of the pads 211 and of the product 203 and any texture thereon, and particularly 23 the pressure between the surfaces which is dependent on the area of contact there 24 between.

26 Figure 3 illustrates in schematic form three different types of pad 311; (a) with a small 27 rubber pad portion 313a with a curved surface corresponding to a small product 303a 28 represented in two-track mode typical of umbilical installation, (b) a large rubber pad 29 portion 313b with a curved surface corresponding to a large product 303b represented in 4 track mode typical of rigid pipeline installation, and (c) a steel pad portion 313c with a v- 31 shaped surface represented in 4 track mode typical of flexible pipeline installation. To 32 optimise the coefficient of friction for specific lay projects, it will be understood that different 33 pad materials and shapes must be used for different products. It is therefore necessary to 34 change the pads on the tensioners when there is a significant change in product diameter, 1 coating material or if installation parameters so dictate. Several such tensioner pad 2 changes may occur during a pipelay campaign or indeed during a single pipelay trip.

4 Traditionally, tensioner pads have been through bolted to the tensioner chain or track.

Replacing pads with pads of another design or different performance can take in the 6 region of 24 hours for each tensioner, and can only take place when the lay process is 7 stopped. More modern solutions make use of transverse retaining pins such as illustrated 8 in Figure 4. A top casting 417 provides a mounting surface which receives a tensioner pad 9 (not shown). A retaining pin 419 is inserted through the tensioner pad via corresponding apertures 421 located at either side of the tensioner pad and the retaining pin 419 secured 11 using safety pins 423. The mounting surface comprises two bosses 425 which protrude 12 from the mounting surface and are received in corresponding apertures on the tensioner 13 pad. In use, the bosses 425 provide resistance against shear forces. Even in this more 14 modern arrangement, the process of changing a tensioner pad is time consuming; first one or both safety pins -which are typically R-clips or rings -are removed, then the retaining 16 pin removed, then the pad removed, then the new pad set, the retaining pin replaced and 17 the safety pin(s) replaced.

19 Such methods may reduce pad changeover times to somewhere in the region of 15 to 18 hours for each tensioner. However, the retaining pin consumes pad depth which results in 21 reduces pad performance and compromises field joint passage.

23 These problems are common to all operators involved in the laying or handling of more 24 than one product specification with the same tensioner. Accordingly, it is an object of at least one aspect of the present invention to provide a tensioner pad attachment that 26 obviates and/or mitigates one or more disadvantages of existing tensioner pad 27 attachments.

29 Further aims and objects of the invention will become apparent from reading the following

description.

1 Summary of the invention

3 According to a first aspect of the invention, there is provided a tensioner pad attachment 4 arrangement comprising; a first plate comprising one or more recesses; and 6 a second plate comprising one or more bosses corresponding to the recesses in 7 the first plate; 8 wherein the one or more bosses comprise one or more magnets to retain the first 9 plate to the second plate.

11 As described in the following detailed description, the term tensioner pad shall be 12 construed as including tensioner pads, straightener pads, alignment pads, flex-lay pads 13 and other similar pads for use on any type of installation vessel.

Preferably, the one or more magnets comprise a permanent magnet. Most preferably, the 16 one or more magnets comprise a rare earth magnet. Preferably, the one or more magnets 17 comprise a neodymium magnet. Alternatively, the one or more magnets comprise a 18 samarium-cobalt magnet.

Preferably, the second plate comprises two bosses, in which case the first plate may 21 comprise two recesses.

23 Preferably, the one or more magnets are housed within the one or more bosses.

24 Optionally, a magnet is retained in a boss using a resin. Alternatively, or additionally, the magnet is retained in the boss by a cap. The cap may be bolted to the boss, and may be 26 bolted through the magnet.

28 Preferably, the one or more bosses are retained in corresponding recesses in the second 29 plate. The one or more bosses may be retained using one or more bolts. Alternatively, or additionally, the one or more bosses may be retained using magnetic attraction.

32 Optionally, the one or more bosses are an interference fit with the recess. Alternatively, 33 the one or more bosses are an interference fit with a bore extending through the second 34 plate. The one or more bosses may comprise a shoulder which engages a stepped portion in the bore.

2 Preferably, the first plate is a base plate of a tensioner pad. Preferably, the second plate is 3 an interface plate for attachment to a chain or track of a tensioner.

Alternatively, the first plate is an interface plate for attachment to a chain or track of a 6 tensioner, in which case the second plate may be a base plate of a tensioner pad.

8 Preferably, the tensioner pad comprises a pad portion attached to the base plate.

9 Optionally, the pad portion at least partially encapsulates the base plate. Preferably, a bottom surface of the base plate is exposed. Alternatively, the bottom surface of the base 11 plate is substantially encapsulated, and the pad portion may comprise one or more 12 apertures which extend to the bottom surface of the base plate.

14 Preferably, the pad portion comprises moulded rubber.

16 Preferably, the interface plate comprises one or more apertures through which the 17 interface plate may be bolted to the chain or track of the tensioner.

19 Optionally, the interface plate comprises one or more resilient means. The resilient means may bias the tensioner pad towards a product. The resilient means may comprise a 21 spring, or may comprise a rubber portion.

23 The resilient means may be provided behind the bosses.

Preferably, the depth of the one or more recesses corresponds to the height of the one or 26 more bosses. Optionally, the depth of the one or more recesses is selected to achieve a 27 desired pull off force.

29 Optionally, the one or more recesses comprise a protrusion, and the one or more bosses may comprise a corresponding recess such that protrusion locates in the recess.

31 Preferably, the protrusion is integrally formed with the first plate. Alternatively, the 32 protrusion is attached to the first plate within the recess. Optionally, the protrusion 33 comprises a magnetically susceptible material, and the first plate may comprise a material 34 which is not magnetically susceptible.

1 According to a second aspect of the invention, there is provided a method of attaching a 2 tensioner pad to a track or chain of a tensioner, the method comprising providing one or 3 more magnets to attach the tensioner pad to the track or chain.

The one or more magnets may be provided on an interface plate, which may be 6 permanently or semi-permanently attached to the track or chain. The one or more 7 magnets may be provided in corresponding bosses which provide shear resistance 8 between the tensioner pad and the track or chain.

Optionally, the method comprises receiving the one or more magnets in one or more 11 corresponding recesses. Preferably, the recesses are provided in the tensioner pad, in 12 which case the magnets may be provided on the track or chain. Alternatively, the 13 recesses may be provided on the track or chain, in which case the magnets may be 14 provided on the tensioner pad.

16 The magnets may be provided in a plate. Likewise the recesses may be provided in a 17 plate. The plate may comprise a base plate of the tensioner pad. The plate may comprise 18 an interface plate for permanent or semi-permanent attachment to the track or chain.

Optionally, the method comprises selecting a depth of recess to achieve a desired pull off 21 force.

23 In a particular embodiment of the second aspect, the method comprises attaching a 24 tensioner pad comprising a base plate to an interface plate permanently or semi-permanently attached to a track or chain of a tensioner, wherein one or more magnetic 26 bosses on the interface plate are received in one or more recesses in the tensioner pad.

28 Embodiments of the second aspect of the invention may comprise features corresponding 29 to the preferred or optional features of any other aspect of the invention or vice versa.

31 According to a third aspect of the invention, there is provided a method of retrofitting for an 32 attachment arrangement according to the first aspect, the method comprising providing 33 one or more magnetic bosses on one or more interface plates attached to a track or chain 34 of a tensioner.

1 Optionally, the method comprises replacing one or more shear discs with one or more 2 magnetic bosses. Alternatively, or additionally, the method comprises machining the one 3 or more interface plates to provide recesses to receive one or more magnetic bosses.

4 Further alternatively, the method comprises replacing one or more top castings with one or more interface plates according to the first aspect.

7 Optionally, the method comprises providing one or more recesses corresponding to the 8 one or more magnetic bosses in a base plate of one or more tensioner pads.

In a particular embodiment, the method may comprise removing a retaining pin from a top 11 casting, removing a tensioner pad, replacing one or more shear discs with magnetic 12 bosses, and setting a tensioner pad comprising one or more recesses on the top casting.

14 Embodiments of the third aspect of the invention may comprise features corresponding to the preferred or optional features of any other aspect of the invention or vice versa.

17 According to a fourth aspect of the invention, there is provided a tensioner interface plate 18 comprising one or more magnetic bosses. The tensioner interface plate may comprise a 19 second plate according to the first aspect.

21 According to a fifth aspect of the invention, there is provided a tensioner pad comprising 22 one or more recesses on a bottom face. The tensioner pad may comprise a first plate 23 according to the first aspect.

Embodiments of the fourth and fifth aspects of the invention may therefore comprise 26 features corresponding to the preferred or optional features of the first aspect of the 27 invention.

29 According to a sixth aspect of the invention, there is provided a tensioner comprising a plurality of interface plates attached to a track or chain, wherein the interface plates 31 comprise one or more magnetic bosses.

33 The tensioner may further comprise a corresponding plurality of tensioner pads comprising 34 recesses which receive and retain corresponding magnetic bosses on corresponding interface plates.

2 The tensioner preferably comprises a plurality of tracks or chains.

4 Embodiments of the sixth aspect of the invention may comprise features corresponding to the preferred or optional features of any other aspect of the invention or vice versa.

7 According to a seventh aspect of the invention, there is provided a method of laying a 8 product comprising driving or braking the tracks of a tensioner according to the sixth 9 aspect to control the speed at which the product is deployed 11 Embodiments of the seventh aspect of the invention may comprise features corresponding 12 to the preferred or optional features of any other aspect of the invention or vice versa.

14 According to an eighth aspect of the invention, there is provided a pad attachment for a tensioner pad, straightener pad, aligner pad or flex-lay pad, characterised in that the 16 attachment comprises one or more magnets. The one or more magnets may be disposed 17 on one or more component parts of the tensioner pad attachment. For example, one or 18 more magnets may be provided on a retaining pin and/or receiving portions corresponding 19 to the retaining pin. Preferably, the one or more magnets retain the pad on a respective apparatus, which may be a tensioner, straightener, aligner, or the like.

22 Embodiments of the eighth aspect of the invention may comprise features corresponding 23 to the preferred or optional features of any other aspect of the invention or vice versa.

According to another aspect of the invention, there is provided a tensioner pad attachment 26 arrangement substantially as herein described with reference to Figures 6 to 8.

28 According to a further aspect of the invention, there is provided a tensioner pad 29 substantially as herein described with reference to Figures 6 to 8.

31 According to yet further aspect of the invention, there is provided an interface plate 32 substantially as herein described with reference to Figures 6 to 8.

1 Brief description of the drawings

3 Aspects and advantages of the present invention will become apparent upon reading the 4 following detailed description and upon reference to the following drawings (like reference numerals referring to like features) in which: 7 Figure 1 illustrates a typical pipelay vessel according to the prior art; 9 Figure 2 illustrates a typical track type pipe tensioner according to the prior art; 11 Figure 3 illustrates a number of typical tensioner pads according to the prior art; 13 Figure 4 illustrates a typical tensioner pad mounting arrangement according to the prior 14 art; 16 Figure 5 illustrates a tensioner pad attachment arrangement according to an embodiment 17 of the present invention, prior to attachment; 19 Figure 6 illustrates a perspective view from (a) above and (b) below the tensioner pad attachment arrangement shown in Figure 5 after attachment; 22 Figure 7 illustrates a tensioner pad according to another embodiment of the present 23 invention, including a cross-sectional view; and Figure 8 illustrates an interface plate corresponding to the tensioner pad shown in Figure 26 7, also including cross sectional views of portions thereof.

1 Detailed Description

3 As discussed in the background to the invention above, operators are required to carry out 4 lengthy tensioner pad changeovers to accommodate different products, different product sizes, different product materials and different product configurations. As intimated in the 6 foregoing summary of the invention, while the invention is exemplified by reference to a 7 tensioner pad, the invention finds equivalent utility in relation to straightener pads, 8 alignment pads, flex-lay pads and other similar pads which may be used on any type of 9 installation vessel, whether s-lay, j-lay, reel-lay, flex-lay or a combination thereof.

Accordingly, references to tensioner pads and tensioners shall be understood to 11 encompass all of the above.

13 An embodiment of the present invention is illustrated in Figure 5 which addresses at least 14 some of the limitations of the prior art. An improved tensioner pad attachment arrangement is shown which comprises a tensioner pad 511 which itself comprises a pad 16 portion 513 mounted on a base plate 527.

18 An interface plate 517 is provided which attaches directly to the tensioner chain or track 19 (not shown). The interface plate 517 may be permanently attached thereto and a number of apertures are provided through which the interface plate 517 may be bolted to the chain 21 or track.

23 On a pad-facing surface of the interface plate 517 there are located two bosses 525.

24 During attachment, the bosses 525 are received in corresponding recesses 529 on the base plate 527 of the tensioner pad 511. In addition to providing robust location and shear 26 force transmission, the bosses 525 are provided with rare earth magnets 531 which 27 securely retain the tensioner pad 511 to the interface plate 517 and hence the chain or 28 track.

This arrangement does away with the need for retaining pins and safety pins as required 31 by the most modern of attachment arrangements. Note however that such retaining pins 32 may still be used to supplement the attachment provided by the magnetic bosses. Such 33 retaining pins may themselves be provided with one or more magnetic portions to do away 34 with the need for safety pins.

1 In this example, the rare earth magnets 531 are samarium cobalt. In another example, 2 neodymium magnets are employed. Rare earth magnets produce significant attraction 3 forces which are sufficient to hold the tensioner pad 511 to the interface plate 517 while in 4 use. Tensioner pads according to the invention will typically weigh less than 15 kg and the typical pull off force per magnet -accounting for reduction by stainless steel interface plate 6 517 -may be on the order of 45 kg.

8 It is advantageous if the magnets 531 are encapsulated or housed within the bosses 525, 9 which provides protection against impact and/or abrasion, although they can simply be retained within the bosses. By providing a localised magnetic field, there is no cumulative 11 effect of multiple magnets, so behaviour and performance within the larger system can be 12 predicted and controlled.

14 The magnetic bosses 525 may be retained in recesses formed in the interface plate 517 using bolts but may be retained in the recesses by magnetic attraction only.

17 As described above, the process of changing a tensioner pad according to the prior art is 18 time consuming; first one or both safety pins are removed, then the retaining pin removed, 19 then the pad removed, then the new pad set, the retaining ring replaced and the safety pin(s) replaced. In accordance with the present invention, the process of changing a 21 tensioner pad is now reduced to two steps; remove the old pad; and set the new pad. This 22 is anticipated to reduce tensioner pad changeover times by around 50%; i.e. to 23 somewhere in the region of 9 hours. When balanced against current estimated vessel 24 costs at $250,000 per day, this represents a $94,000 saving per instance. With an estimated changeover every fortnight, this equates to an estimated annual saving of $2.4m 26 and a significant increase in utilisation.

28 Note that while the examples above describe the use of two magnetic bosses, it is 29 envisaged that any number of magnetic bosses may be employed. Also, where the examples above refer to rare earth magnets samarium cobalt and neodymium, any other 31 permanent magnets or combinations thereof may be employed. In fact, any magnet 32 capable of retaining a tensioner pad on the corresponding interface plate will be 33 understood to fall within the scope of the present invention.

1 The arrangement described above particularly lends itself to retro-fitting. For example the 2 bosses 425 shown in the prior art arrangement in Figure 4 may be removed and replaced 3 with magnetic bosses 525 as shown in Figure 5. This would allow the tensioner pad 511 4 shown in Figure 5 to be attached to the top casting 417 shown in Figure 4, and the retaining pin 419 and safety pins 423 can be dispensed with. If the bosses 425 are 6 integrally formed with the casting 417 the casting can be replaced or alternatively 7 machined to provide recesses for magnetic bosses 525. This would permit existing 8 tensioner pads which utilise retaining pins to be used if desired or appropriate.

In the embodiment shown in Figure 5, the tensioner pad 511 comprises a moulded rubber 11 pad 513 and the base plate 527 is encapsulated within the rubber pad 513; with the 12 exception of the bottom surface which is exposed and comprises the recesses 529.

13 Figure 6 shows a perspective view of the tensioner pad 511 located on the interface plate 14 517, with dotted lines to identify the encapsulated base plate 527.

16 As noted above, the interface plate 517 is bolted onto the tensioner chain or track (not 17 shown). The magnetic bosses 525 or shear discs are visible on the underside of the 18 interface plate 517, although in alternative arrangements the magnetic bosses 525 may be 19 located in blind bores on the pad-facing surface of the interface plate 517. Also, without deviating from the scope of the present invention, the magnetic bosses or shear discs may 21 instead be located on the base plate of the tensioner pad and received in corresponding 22 recesses on the interface plate.

24 Rather than exposing all or substantially all of the bottom surface of the base plate, it is foreseen that substantially all of the bottom surface of the base plate is also encapsulated, 26 in which case apertures may be provided in the rubber on the bottom surface of the 27 tensioner pad which correspond with the recesses (or bosses as per the variant suggested 28 above). The magnetic bosses are then received in the recesses in the base plate via the 29 apertures in the rubber. This may provide further advantages in that the rubber thus sandwiched between the base plate and the interface plate provides resilience and/or 31 biases the tensioner pad 513 towards the product.

33 It is also foreseen that springs or some other corresponding resilient means may be 34 provided in the recess or recesses in the interface plate which retain the magnetic bosses, 1 beneath the magnetic bosses, so as to provide resilience and/or to bias the tensioner pad 2 513 towards the product.

4 The pull off force required to remove the tensioner pad 511 from the interface plate 517 is inversely proportional to the thickness of any air gap between the base plate 527 and the 6 magnetic bosses 525. Accordingly, by appropriate selection of the depth of the recesses 7 529 with respect to the height of the magnetic bosses 525, the pull off force required to 8 remove the tensioner pad 511 from the interface plate 517 can be predetermined.

The skilled person will understand from the generality of the foregoing description that the 11 tensioner pad attachment arrangements described herein are not limited to any particular 12 lay technique, and may be employed in J-lay, S-lay, Reel-lay and Flex-lay applications, 13 and of course lay techniques which may be developed in the future which rely on 14 tensioners with discrete tensioner pads.

16 Once a track-type pipe tensioner has been retro-fitted with the inventive interface plates - 17 or indeed produced with the inventive interface plates -all future pad changeover 18 operations can be carried out far more quickly than previously possible. This results in 19 significantly less vessel down-time and may allow the changeover to be performed during a single operating shift by a single team which has benefits in consistency as well. Knock- 21 on benefits follow in scheduling, because the changeover times are so much shorter.

23 There are also safety benefits as there are no loose parts and there is a corresponding 24 reduced risk of dropping components and the damage and/or injury that such accidents can involve because the magnetic bosses immediately hold the tensioner pads in place 26 without the need to insert retaining pins or make other fastenings.

28 Figure 7 includes a cross-sectional view through an alternative tensioner pad 611, and 29 Figure 8 includes a cross sectional view through portions of a corresponding interface plate 617. The interface plate 617 is provided with countersunk bores 649 to allow the 31 interface plate 617 to be bolted onto a tensioner chain or track.

33 In this embodiment, the recess 629 can be seen to include a cylindrical protrusion 633 on 34 the end face of the recess 629. This protrusion 633 corresponds to a recess 635 on the magnetic boss 625 on the interface plate 617. When the magnetic boss 625 is received in 1 the recess 629, the protrusion 633 is received in the recess 635. This assists in proper 2 location of the boss 625 in the recess 629, and may provide additional shear transfer.

4 The magnetic boss 625 in this embodiment can be seen to be received in a stepped bore through the interface plate 617. It is inserted through the back surface of the interface 6 plate 617 and the bore extends through to the pad-facing surface from which the boss 625 7 protrudes. A shoulder 641 engages a step 643 in the bore -this prevents the magnetic 8 boss 625 from being pulled out of the interface plate 617 when the tensioner pad 611 is 9 pulled off, and the magnetic boss 625 is an interference fit with the bore to prevent it from falling out when the tensioner pad 611 is not in place.

12 The magnetic boss 625 houses a magnet 631 which is retained in the boss 625 with a 13 resin 645 and a cap 647 which is bolted to the body of the boss 625 through the magnet 14 631. The boss 625 and components thereof are machined from stainless steel.

16 Note that in the embodiment above the protrusion 633 is integral to the metallic base plate 17 627. However, such a protrusion could be attached to the base plate instead, which would 18 enable the base plate to be constructed of a non-metallic and/or non-magnetically 19 susceptible material, and rely on the protrusion for attachment to the magnetic boss.

21 In each of the embodiments and variations discussed above, a magnetic component or 22 magnetic components protrude from an interface plate (or in contemplated variants from a 23 base plate of the tensioner pad). It is foreseen that the magnetic component or magnetic 24 components could instead be located in recesses which receive metallic protrusions or bosses. It is also foreseen that the magnetic component or magnetic components could 26 be flush with or embedded in a surface of an interface plate and/or a base plate of a 27 tensioner pad. In such variants, shear transfer between the base plate and interface plate 28 may be provided by additional engagement means therebetween, such as pins and 29 apertures, bosses and recesses, elongate members and slots, or a recess in the interface plate which receives and retains substantially all of the base plate.

32 The invention provides a means for attaching tensioner pads to tensioners in a robust and 33 reliable manner which also provides for quick and convenient removal and replacement.

34 This is achieved by replacing conventional attachment arrangements such as permanent or semi-permanent bolting arrangements or retaining pin and safety pin arrangements with 1 a magnetic attachment arrangement. In a preferred embodiment, magnetic bosses are 2 provided on an interface plate which is permanently or semi-permanently attached to the 3 tensioner chain or track, and received in corresponding recesses on a base plate of the 4 tensioner pad.

6 Note that the term semi-permanent alludes to attachments which are not necessarily 7 permanent, but are not temporary in the sense that they are likely to remain in place for at 8 least one pad changeover operation.

As used herein, the terms bottom, lower, below and the like are descriptive of a feature 11 that is located towards a first end/side of an apparatus, system or component while the 12 terms top, upper, above and the like are descriptive of a feature that is located towards a 13 second, opposing end/side of the apparatus, system or component.

Throughout the specification, unless the context demands otherwise, the terms 'comprise' 16 or 'include', or variations such as 'comprises' or 'comprising', 'includes' or 'including' will be 17 understood to imply the inclusion of a stated integer or group of integers, but not the 18 exclusion of any other integer or group of integers.

The foregoing description of the invention has been presented for the purposes of 21 illustration and description and is not intended to be exhaustive or to limit the invention to 22 the precise form disclosed. The described embodiments were chosen and described in 23 order to best explain the principles of the invention and its practical application to thereby 24 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, 26 further modifications or improvements may be incorporated without departing from the 27 scope of the invention as defined by the appended claims.