Technical field

Some examples relate to an offshore cable and a method for installing said offshore cable in an offshore location, and some examples relate to a method for increasing the buoyancy of an offshore cable, to a method for attaching a buoyancy member to an offshore cable and to a method and apparatus for offloading an offshore cable from a vessel.

Background art

In the field of offshore and marine engineering, there is often the requirement to install and secure structures in an offshore location, both subsea on the seabed and floating on the surface. To enable offshore power production, it is often necessary to anchor a floating power production plant at a floating surface location. For example, the use of floating wind turbines is becoming more and more common, and each floating wind turbine must be anchored in place to minimise any drift that it may otherwise experience as a result waves, tides, swells, or the like. Such floating power production plants may be designed to stay in place for a prolonged period, and therefore it is advantageous to be able to anchor them in place for a prolonged period of time. Similarly, in the production of hydrocarbons, it is often necessary to anchor an offshore vessel or floating platform in a position to enable production of hydrocarbons without the risk of damage to subsea equipment located below the vessel or floating platform.

Although it may be desirable to minimise movement of floating offshore equipment and platforms, some movement, both vertical and horizontal, is inevitable due to the rising and falling of tides, and sea and ocean swells. Therefore, floating offshore equipment must be designed to accommodate such movement without incurring damage.

One method of achieving this is to provide anchoring cables that are, to some degree slack. In doing so, as the floating offshore equipment/platform moves (due to tides, for example) the slack in the anchoring cables allows the offshore equipment/platform to move with the rising and falling tides while floating on the surface, thereby avoiding damage to the floating equipment/platform. Rather than storing slack cable on the sea floor, which may lead to damage of the cable, it is often designed to be buoyant, to some degree. This buoyancy allows it to be held subsea, in a location between the seabed and the surface, and it may be held, for example, in an S-bend configuration, which is able to "straighten out" when a longer length of anchoring cable is required, and curve when a shorter length of anchoring cable is required.

Cables are often made of material that is not naturally buoyant, and therefore it is necessary to attach buoyant members to the cabling to provide them with the required buoyancy. While providing benefits to a user when located subsea, the buoyant members may add an additional level of complexity to the installation of subsea cabling, because they can often be large and difficult to install. Further, there is a risk that the installation process damages the buoyant members, which can render them less effective, or possibly completely ineffective.

Summary

A first aspect of the disclosure relates to an apparatus for offloading an offshore cable from a vessel, comprising: a support structure; a conveyor mechanism mounted on the support structure, the conveyor mechanism comprising an endless member configurable to engage and axially displace a section of offshore cable; the conveyor mechanism being configured to engage a section of offshore cable so as to provide a curve in the section of offshore cable.

A second aspect of the disclosure relates to a method for offloading an offshore cable from a vessel, comprising; providing an offshore cable and an apparatus for offloading the offshore cable according to the first aspect on a vessel; mounting the offshore cable on the conveyor mechanism of the offloading apparatus; operating the offloading apparatus to engage the offshore cable and provide tension in the offshore cable; operating the offloading apparatus to move the offshore cable in an axial direction so as to offload the offshore cable from the vessel an to an offshore location.

A third aspect of the disclosure relates to a method for attaching a buoyancy member to an offshore cable on a vessel, comprising: providing an offshore cable and at least one buoyancy member on a vessel; locating the offshore cable in a tensioner to hold a portion of the offshore cable in tension on the vessel; locating the at least one buoyancy member on an attachment device, the attachment device being located adjacent the portion of the offshore cable in tension; using the attachment device to attach the at least one buoyancy member to the portion of the offshore cable in tension.

A fourth aspect of the disclosure relates to a method for increasing the buoyancy of an offshore cable, comprising: providing an offshore cable with a plurality of buoyancy members located thereon; locating an supplemental buoyancy member on at least one of the plurality of buoyancy members. A fifth aspect of the disclosure relates to an offshore cable for offshore installation from a vessel, wherein the offshore cable comprises: a plurality of buoyancy members located thereon, at least one of the buoyancy members being axially fixed relative to the offshore cable; a supplemental buoyancy member located on at least one of the plurality of buoyancy members.

A sixth aspect of the disclosure relates to an offshore cable for offshore installation from a vessel, wherein the offshore cable comprises: a plurality of buoyancy members located thereon, at least one of the buoyancy members being axially fixed relative to the offshore cable; a supplemental buoyancy member located on at least one of the plurality of buoyancy members.

A seventh aspect of the disclosure relates to an offshore cable for offshore installation from a vessel, wherein the offshore cable comprises: a plurality of buoyancy members located thereon; wherein at least two of the plurality of buoyancy members are fixed buoyancy members and are axially fixed relative to the offshore cable such that axial movement therealong is restricted; and wherein at least one of the plurality of buoyancy members is at least one moveable buoyancy member and is located on the offshore cable axially intermediate the at least two fixed buoyancy members.

An eighth aspect of the disclosure relates to an offshore cable for offshore installation from a vessel, the offshore cable comprising: a cable having a plurality of buoyancy members located thereon; each of the plurality of buoyancy members comprising a longitudinal axis, a circumferential surface and two axial surfaces, each of the two axial surfaces comprising a linearly extending portion, extending between the longitudinal axis and the circumferential surface at an oblique angle relative to the longitudinal axis such that the linearly extending portion of a first of the plurality of buoyancy members is configurable to engage the linearly extending portion of a second of the plurality of buoyancy members located adjacent the first buoyancy member upon bending of the cable.

A ninth aspect of the disclosure relates to a method for installing an offshore cable in an offshore location from a vessel, the method comprising: winding an offshore cable onto a cable storage apparatus, the offshore cable comprising a plurality of buoyancy members located thereon, such that a surface of a first of the plurality of buoyancy members engages a surface of a second of the plurality of buoyancy members; providing the cable storage apparatus with the wound offshore cable thereon on a vessel; applying tension to the wound offshore cable to unwind the offshore cable from the cable storage apparatus.

Brief descriptions of the drawines

Some examples are described herein and may be more fully appreciated by reference to the following illustrative and non-limiting detailed description of example embodiments of the present disclosure, when taken in conjunction with the accompanying drawings.

Figure 1 is a schematic illustration of buoyancy members located on an offshore cable.

Figures 2a and 2b are elevation views of a buoyancy member.

Figure 3 is a perspective view of an offshore cable wound on to a cable storage apparatus.

Figure 4 is an illustration of two buoyancy members on an offshore cable.

Figure 5 is a schematic illustration of a cable storage apparatus comprising buoyancy members held thereon.

Figure 6 is a further schematic illustration of a cable storage apparatus comprising buoyancy members held thereon.

Figure 7 is an illustration of layers of an offshore cable held on a cable storage apparatus.

Figures 8a and 8b illustrate a section of offshore cable in further detail.

Figures 9a and 9b are perspective illustrations of an offshore cable having buoyancy members and supplemental buoyancy members.

Figure 10 is a schematic illustration of a method for attaching a number of buoyancy members to an offshore cable.

Figure 11a illustrates a perspective view of an apparatus for offloading an offshore cable from a vessel.

Figure 11b illustrates a further detail of the apparatus of Figure 2A.

Figure 12 illustrates an elevation view showing parts of an apparatus for offloading an offshore cable from a vessel.

Detailed description

The present disclosure will now be described with reference to the accompanying drawings, in which some preferred examples of the disclosure are shown. The disclosure may, however, be embodied in other forms and should not be construed as limited to the herein disclosed examples. The disclosed examples are provided to fully convey the scope of the disclosure to the skilled person. The following description may use terms such as "horizontal", "vertical", "lateral", "back and forth", "up and down", "upper", "lower", "inner", "outer", "forward", "rear", etc. These terms generally refer to the views and orientations as shown in the drawings and that are associated with a normal use of the invention. The terms are used for the reader's convenience only and shall not be limiting.

The installation of offshore cables is often limited by weather windows as it is not possible to install these cables in harsh weather conditions. An increase in the speed of installation increases the number of cable installations, which may be achieved in any weather window and is therefore beneficial. Additionally, a more efficient way of storing the offshore cable or its raw materials for assembly on an installation vessel may reduce the number of installation vessels needed or increase the number of cable installations one installation vessel is capable of before restocking its supply of offshore cables or their raw materials.

One described example relates to a method for reducing the time taken to install an offshore cable is to transport the offshore cable with pre-attached buoyancy members, instead of assembling the offshore cable and the buoyancy member at the installation site. The transportation of an offshore cable with already attached buoyancy members preferably comprises a storage method that prevents damage to both the offshore cable and the buoyancy members. This method may also yield the advantage of not requiring an assembly apparatus, which may be used to assemble the buoyancy members and the offshore cable, thereby increasing the cargo space for the transportation of offshore cables with already attached buoyancy members.

According to a first described example, there is an offshore cable for offshore installation from a vessel, the offshore cable comprising: a cable having a plurality of buoyancy members located thereon; each of the plurality of buoyancy members comprising a longitudinal axis, a circumferential surface and two axial surfaces, each of the two axial surfaces comprising a linearly extending portion, extending between the longitudinal axis and the circumferential surface at an oblique angle relative to the longitudinal axis such that the linearly extending portion of a first of the plurality of buoyancy members is configurable to engage the linearly extending portion of a second of the plurality of buoyancy members located adjacent the first buoyancy member upon bending of the cable.

According to a second described example, there is a method for installing an offshore cable in an offshore location from a vessel, the method comprising: winding an offshore cable onto a cable storage apparatus, the offshore cable comprising a plurality of buoyancy members located thereon, such that a surface of a first of the plurality of buoyancy members engages a surface of a second of the plurality of buoyancy members; providing the cable storage apparatus with the wound offshore cable thereon on a vessel; applying tension to the wound offshore cable to unwind the offshore cable from the cable storage apparatus.

Each buoyancy member comprising a first and a second surface extending obliquely relative to the longitudinal axis of the buoyancy member, the first surface extending from a first axial end of the buoyancy member towards the axial centre of the buoyancy member, and the second surface extending from a second axial end of the buoyancy member towards the axial centre of the buoyancy member.

Figure 1 shows an offshore cable 100 with at least one attached buoyancy member 110a-d (in this case, four buoyancy members 110a-d). The offshore cable 100 may, although not exclusively, be used for transportation of energy or communication signals, or for mooring, and may have mechanical properties suitable for its purpose. To assist in the understanding of the skilled reader, the offshore cable 100 is illustrated with a longitudinal axis 101. The at least one buoyancy member 110a-d is attached to the offshore cable 100, preferably by clamping the at least one buoyancy member 110a-d to the offshore cable, the person skilled in the art may also use any other appropriate means, such as gluing or welding the at least one buoyancy member 110a-d on the offshore cable 100. Alternatively, the offshore cable 100 and the at least one buoyancy member 110a-d may comprise fastening means to attach the at least one buoyancy member 110a-d to the offshore cable 100 or the at least one buoyancy member 110a-d may be formed from at least 2 parts which, when assembled, form an annular shape enclosing the offshore cable 100 and thereby attaching the at least one buoyancy member 110a-d to the offshore cable 100. In this example, the at least one buoyancy member 110a-d comprises an extruded shape, e.g. a cylinder or a cuboid, which may facilitate manufacture of the at least one buoyancy member than other more complex shapes, and may comprise a longitudinal axis that makes location of such buoyancy members 110a-d onto cable 100 simpler. Preferably, the at least one buoyancy member 110a-d comprises a positive buoyancy, more preferably the at least one buoyancy member 110a-d is made of a buoyant material. Knowing the buoyancy of the material of each buoyancy member 110a-d, a user may be able to provide buoyancy members having a desired level of buoyancy. In this way, the buoyancy of the offshore cable 100 with the buoyancy members 110a-d attached may be precisely controlled.

Figure 2a is an illustration of an elevation view of one of the at least one buoyancy members 110a-d showing some internal detail. The buoyancy member 110 comprises a longitudinal axis 114 and is preferably rotationally symmetrical around the longitudinal axis 114, as in this example. The shown buoyancy member 110 is rotationally symmetrical around the longitudinal axis 114, other shapes of buoyancy member 110 may also be possible as the skilled reader will understand. The buoyancy member 110 preferably has axial surfaces that do not extend perpendicularly to the longitudinal axis 114, but rather at an angle to the perpendicular. Having such surfaces extending at an angle may facilitate winding of the buoyancy member on a cable storage apparatus 130, which will be further explained in the following description. The longitudinal length L of the buoyancy member 110 generally decreases radially, such that the length L of the buoyancy member 110 is greater nearer the longitudinal axis 114 and gradually becomes reduced in the radial direction away from the longitudinal axis 114. As can be seen in Figure 2a, the side/axial surface of the buoyancy member has a radial taper from the longitudinal axis 114 to the radially outer surface of the buoyancy member 110. The axial surfaces may be formed such that a radially inner portion 111 has a greater longitudinal length L than a radially outer portion 112 resulting the radially decreasing longitudinal length L. The axial surface may extend in a linear direction from the inner portion 111 to the outer portion 112, either along the partial or whole radial length of the axial surface. In some other examples, a part of the axial surface may extend radially in a non-linear manner, such as a cured manner. Preferably the longitudinal length L may gradually decrease as this may facilitate, for example, the positioning of one buoyancy member 110 adjacent another buoyancy member 110, for example in use or for the purposes of stacking for transport, or when wound onto a storage member, as will be described in greater detail in the following description.

The buoyancy member 110 comprises an opening 113 for the offshore cable 100. In this example, the opening is circular in cross-section and is located on the longitudinal axis 114 (i.e. is co-axial with the longitudinal axis), resulting in the offshore cable 100 and the at least one buoyancy member 110 forming a cylindrically symmetrical unit about the longitudinal axis 114. In Figure 2a, the through-bore 113 is shown in broken outline and indicates a through bore 113 extending entirely through the buoyancy member 110. The through-bore 113 of Figure 2a decreases in diameter until the longitudinal centre of the buoyancy member 110, and then increases again towards the opposite axial surface of the buoyancy member 110. As such, the through-bore 113 has the shape of two frustum cones with the smaller diameter face positioned end-to-end, and may be symmetrical in a plane perpendicular to the longitudinal axis 114. The person skilled in the art will understand, that after boring the top and bottom surface of the buoyancy member 110 may not have the indicated side-view shape but rather have a flat surface extending along the boring as shown in Figure 2b, such that the opening is in the form of a cylindrical bore that extends through the buoyancy member 110. Preferably, the edges of the opening 113 are rounded to reduce the possibility of damage to a cable coming into contact therewith (e.g. an offshore cable). When locating the buoyancy member 110 at its centre 115 on the offshore cable 100, e.g. by clamping, gluing, welding, fastening means or the like, the geometry of the opening and/or the through-bore may enable the cable to bend to some degree inside of the buoyancy member 110 and may facilitate winding on a cable storage apparatus 130 with a lower winding radius saving storage space and/or may distribute the winding curvature equally over the offshore cable 100 between two adjacent buoyancy members 110, which may result in reduced stress on the offshore cable 100 and may prevent damage to the offshore cable 100.

Figure 2b shows the buoyancy member 110 of Figure 2a with a through-bore 113 and rounded edges at the opening of the through-bore 113 from a sectional side view. The broken lines show the outer boundaries of the opening of through-bore 113 in hidden detail, while the solid line indicates the respective outer boundaries of the buoyancy member 110 of the sectional side view.

The through-bore 113 may have any shape suitable for fitting the offshore cable 100 and for locating (e.g. attaching) the buoyancy member 110 on the offshore cable 100. The buoyancy member 110 may also be attached at any other position, if the chosen attachment mechanism facilitates this. For example, there may be an opening that is not located on the longitudinal axis, or an opening that is located parallel to the longitudinal axis, that may be used for location of the buoyancy member 110 on an offshore cable. Preferably, the buoyancy member 110 is created by assembling at least two parts. In this way the buoyancy member 110 may be easily attached at any position of the offshore cable 100, for example by positioning each of the parts of the buoyancy member 110 around the offshore cable 100. The at least two parts of the buoyancy member 110 may have a clamping mechanism or may be glued, welded, tied or bound together to form the buoyancy member 110. The assembly of the buoyancy member 110 and the attachment of the buoyancy member 110 to an offshore cable may be done simultaneously, i.e. the buoyancy member 110 may be assembled at the desired position around the offshore cable 100 and attached with the chosen attachment means.

Figure 3 shows an offshore cable 100 with multiple buoyancy members 110 attached and wound up on a cable storage apparatus 130. The cable storage apparatus 130 may e.g. be installed on a vessel (not shown) to bring the offshore cable 100 to its installation site. The cable storage apparatus 130 may preferably be a storage drum, however, any other known storage system may be equally applicable. Winding of the cable may be achieved by rotating the storage drum to form tension in the cable and spool the cable thereon, if a storage drum is used. In the shown Figure 3, a partial layer of winding of offshore cable 100 is held upon the cable storage apparatus 130, wherein the wound section of cable 100 has attached buoyancy members 110. This configuration provides permits the offshore cable 100, with buoyancy members attached thereto, to be wound directly onto the cable storage apparatus 130. Layers of the offshore cable 100 with attached buoyancy members 110 may be wound on top of each other, without causing harm to the offshore cable 100 or the buoyancy members 110 upon unwinding for subsequent use. Additionally the geometry of the buoyancy members 110 may facilitate the winding of the offshore cable 100 or may reduce the probability of damaging either of the buoyancy members 110 or the offshore cable 100 by providing a geometry of buoyancy members that may more easily fit together when wound, as has already been mentioned and will be further described with Figures 5-7.

When storing the offshore cable 100 on the cable storage apparatus 130 the distance D between two neighbouring buoyancy members 110 may be important. For example, the distance between two neighbouring buoyancy members 110 may be important to the degree of buoyancy provided to a particular section of the offshore cable, and/or the distance between the buoyancy members may be important when winding the cable on a cable storage apparatus 130 Figure 4 shows two neighbouring buoyancy members 110a, b attached onto an offshore cable 100. The offshore cable 100 is illustrated as a double line in this Figure to facilitate the reader's comprehension of the placement of planes 141a, b of the buoyancy members 110a, b, which are located perpendicular to the longitudinal axis of the offshore cable 100 and aligned with the widest part of one axial face of each buoyancy member 110.

Here, the distance D between two neighbouring buoyancy members 110 is considered to be the distance measured along the offshore cable 100 between each of the planes 141a, b, where the offshore cable 100 is arranged in a straight configuration. It should be noted that, while the distance D is illustrated here to be roughly equal to the length of one buoyancy member, it may also be the case in some examples that the value of D is zero, such that the adjacent buoyancy members are in abutment. Having abutting adjacent buoyancy members may provide advantages in terms of spooling the buoyancy members as well as securing the buoyancy members on the offshore cable while restricting axial movement of the buoyancy members.

Figure 5 illustrates a cable storage apparatus 130, here a storage drum, with an arrangement of multiple buoyancy members 110. To create the necessary curvature to enable winding of the offshore cable 100 upon the cable storage apparatus 130, the offshore cable 100 with the attached buoyancy members 110 bends around the circumference of the storage drum 130. This may be achieved by having a distance D (e.g. D equal to the width of one buoyancy member, 90%, 80% or some fraction of the width of a buoyancy member) between each buoyancy member on the offshore cable 100 to prevent interference (e.g. friction or compression between parts of adjacent buoyancy members 110) between the buoyancy members 110 as the offshore cable 100 is bent around the circumference of the storage apparatus 130. Alternatively or additionally, the buoyancy members 110 may be designed to permit bending of the offshore cable 100 by comprising a conical through-bore 113 (see Figures 2a and 2b). A close-packed arrangement may also be possible, wherein the multiple buoyancy members 110 are in contact with each other, with the distance D being zero or substantially zero, as is illustrated in Figure 5. Having a small or zero distance D may enable a high degree of buoyancy of offshore cable 100, by permitting all, or substantially all of a length of the offshore cable 100 to be supported by buoyancy members 110, which may be highly desirable in some cases.

As can be seen from Figure 5, the axial surfaces of each buoyancy member 110 extends at a non-zero angle relative to a plane perpendicular to the longitudinal axis of each buoyancy member 110, and at a non-zero angle with respect to the border planes 141a, b, as described in relation to Figure 4. Having the axial surfaces of each buoyancy member 110 extending at an angle relative to the plane perpendicular to the longitudinal axis of the buoyancy member 110 (e.g. having the axial surfaces being sloping surfaces) may enable the arrangement of buoyancy members 110 in abutment on the offshore cable 100 (i.e. where the distance D is zero, or substantially zero) in an circular arc on the cable storage apparatus 130 while minimising friction or compression between each adjacent buoyancy member 110, and thereby may enable a stress-free (or at least a reduced-stress) winding of the offshore cable 100 and the buoyancy members 110 on the cable storage apparatus 130, thereby reducing the risk of damage to both components. Additionally, and as shown in Figure 5, the shape of the buoyancy members 110 may permit a radially facing surface of the buoyancy members to abut the storage apparatus (shown in Figure 5 as the interface at 132) , which may improve the stability of the buoyancy members 110 when mounted on the storage apparatus 130. In some examples, it may be beneficial to maximise the area of interface between each buoyancy member 110 and the storage apparatus 130, as this may decrease stress concentrations in each of the buoyancy members 110 as a result of tension in the offshore cable 100. Therefore the non-zero angle at which the axial surfaces of the buoyancy member extend relative to the perpendicular plane may be selected so as to be large enough to enable each buoyancy member 110 to fit together in an arc in contact with the storage apparatus 130, but not so large so as to significantly reduce the area of interface 132 between each buoyancy member 110 and the storage apparatus 130. The angle may therefore be considered to be a small angle.

Although shown as being a cylindrical drum, the cable storage apparatus 130 may have a non-cylindrical shape which may still enable buoyancy members to be wound thereon, for example the cable storage apparatus 130 may have an extruded oval shape. It may be possible to produce or provide a particular shape of buoyancy member 110 depending on the characteristics of the cable storage apparatus 130. For example, where the cable storage apparatus 130 has a smaller diameter, then it may be useful to have buoyancy members 110 having axial surfaces extending at a greater angle to the plane perpendicular to the longitudinal axis, as previously described, as this may enable increased bending of the offshore cable without interference between adjacent buoyancy members 110. Similarly, it where the cable storage apparatus 130 has a larger diameter, then it may be possible to have buoyancy members 110 having axial surfaces extending at a smaller angle, which may permit the larger buoyancy members 110 to be used, which may additionally provide increased buoyancy, for example, in addition to the aforementioned advantages.

Figure 6 shows the same arrangement as Figure 5 with the offshore cable 100 shown. As can be seen, the buoyancy members 110 have a shape, i.e. have axial surfaces shaped to fit the curvature of the cable storage apparatus 130. The buoyancy members 110 are attached to the offshore cable 100 at their respective centres and the offshore cable 100 may bend to have an equally distributed curvature as has been mentioned before.

Tension may be applied to the offshore cable 100 when unwinding the offshore cable 100 with the attached buoyancy members 110 from the cable storage apparatus 130. The tension may be applied with a tensioning apparatus 140, which may be mounted on the deck of a vessel, for example. When using a tensioning apparatus 140, the installation of the offshore cable 100 may be facilitated by locating the unwound portion of the offshore cable 100 in an offshore location with the tensioning apparatus 140 as the offshore cable 100 is unwound. Preferably, the tensioning apparatus 140 axially moves the offshore cable 100 so as to position the offshore cable 100 in a desired offshore location, thereby reducing the installation time. Additionally, the offshore cable 100 may be installed by locating the unwound portion of the offshore cable 100 in an offshore location via direct unwinding from the vessel, possibly reducing the installation time. To prevent damage to any of the offshore cable 100, the buoyancy members 110 or the cable storage apparatus 130, it may be advantageous to keep the layers of the offshore cable 100 with the attached buoyancy members 110 separate from one another, for example to prevent the buoyancy members 110 of one layer may becoming stuck or wedged between the buoyancy members 110 of another layer which may cause unacceptably high friction or tension when unwinding the offshore cable 100. A reeling speed of the offshore cable 100 from the cable storage apparatus 130 of e.g. O.lm/s, 0.2m/s or 0.14m/s (500m/hour) may be possible without causing potential damage to the offshore cable 100, the buoyancy members 110 or the cable storage apparatus 130, and having the offshore cable 100 wound as is described may facilitate overall reduced reeling or unwinding time by removing the need to repeatedly cease reeling or unwinding to attach buoyancy members to the offshore cable.

Figure 7 illustrates multiple buoyancy members 110 attached to an offshore cable 100 wound in two layers on a cable storage apparatus 130. For improved visibility, only one buoyancy member 110 of the outer layer and only a section of the cable storage apparatus 130 with the wound up offshore cable 100 is shown. The buoyancy members 110 advantageously comprise a shape which allows them to match the curvature of the cable storage apparatus 130 and are more advantageously arranged in such an arrangement as shown in Figure 7. As is shown in Figure 7, between two neighbouring buoyancy members 110 is a gap 134 located between the radially-outer section of the neighbouring buoyancy members 110 caused by the bending of the offshore cable 100 around the shape of the cable storage apparatus 130. Here, an increase in the distance D between the neighbouring buoyancy members 110 may also increase the width of the gap. The width of the gap advantageously is not more the longitudinal length Lof the buoyancy members 110, measured at the outermost radial position of the buoyancy members 110 (i.e. the narrowest or shortest length of each of the buoyancy members 110). In this way, the buoyancy members IlOe of an outer layer are not able to position themselves between the buoyancy members 110a,b,c,d of an inner layer, preventing the buoyancy members 110a-e from getting wedged or stuck and thereby preventing damage to the buoyancy members 110, or delaying the installation when unreeling the offshore cable 100 with the buoyancy members 110a-e from the cable storage apparatus 130.

The attachment of the buoyancy members 110 onto the offshore cable 100 may be axially fixed. This may e.g. facilitate the attachment process or may facilitate the winding of the offshore cable 100 onto the cable storage apparatus 130. The buoyancy members 110 may also be rigidly fixed to the offshore cable 100, as this may facilitate the attachment process or may facilitate winding/reeling of the offshore cable 100 onto/off the cable storage apparatus 130. Alternatively, some of the plurality of buoyancy members 110 may be axially fixed or rigidly fixed onto the offshore cable 100 while other buoyancy members 110 may be arranged in at least one group of axially movable buoyancy members located between, and held in place by, the fixed buoyancy members 110. An axially moveable buoyancy member may refer to a buoyancy member that is able to be moved axially along the offshore cable because it is not axially fixed thereto (e.g. there is a free engagement between the moveable buoyancy member 110 and the offshore cable 100, with no clamping or fixing arrangement therebetween). In some examples a moveable buoyancy member 110 may be simply threaded onto an offshore cable 100 e.g. via a through-bore in the buoyancy member 110). In the case where at least one of the buoyancy members is axially moveable on the offshore cable 100, the buoyancy members 110 may be arranged on the offshore cable 100 such that the distance D between the buoyancy members is zero, or approximately or substantially zero. In this configuration, the axially fixed buoyancy members 110 may hold the axially moveable buoyancy members 110 in place, effectively preventing axial movement thereof. This arrangement may facilitate a simpler and quicker construction, as only some of the buoyancy members 110 have to be attached axia I ly/rigidly fixed to the offshore cable 100.

The person skilled in the art will understand that it may be advantageous to construct any of the multiple types of buoyancy members 110 with the same shape to facilitate mass production, however, any buoyancy member may be created with another shape as this may e.g. facilitate any of the attachment process, the winding process, the reeling process or may be advantageous to obtain the desired buoyancy.

Illustrated in Figures 8a and 8b is a further example of an offshore cable having buoyancy members 110 located thereon. In this example, a plurality of buoyancy members 110 are located on the offshore cable 100 such that each buoyancy member is in contact with each adjacent buoyancy member. According to this example, some of the buoyancy members 110 may be considered to be fixed buoyancy members 110a, which are axially fixed to the offshore cable 100 by a fixing member 150 (i.e. axially fixed so that axial movement of the buoyancy members 110 relative to the offshore cable is not permitted, or is restricted). The fixing member may be, for example, a friction clamp, which may be positioned between the offshore cable 100 and the buoyancy member 110. The friction clamp may simply be a ring of material, such as a metal or rubber, which is able to fit securely round the offshore cable 100, and provide sufficient friction between the offshore cable 110 and the buoyancy member as to prevent or restrict relative axial movement between the offshore cable 100 and the buoyancy member 110. Such a fixing member may be locatable or fixable onto the offshore cable 100 in a quick and simple manner (e.g. by threading and tightening the fixing member onto the offshore cable 100), while also providing sufficient friction for the purposes of axially securing a buoyancy member 110 to the offshore cable 100. As illustrated, the fixing member 150 is located in the through bore of the buoyancy member 110 and positioned between a radially inner surface of the buoyancy member 110 and the offshore cable 100. In this example, the fixing member 150 has an axially central location along the length of the buoyancy member 110, although the skilled person will appreciate that other locations of the fixing member 150 maybe acceptable. Also illustrated in Figure 8a are a number of buoyancy members 110 that are not axially fixed to the offshore cable 100 and are therefore axially moveable thereon. However, as each of the buoyancy members 110 in this example are in contact with each adjacent buoyancy member 110, then axial movement of each of the axially moveable buoyancy members is prevented, or at least substantially restricted, as a result of their engagement with each adjacent buoyancy member 110. Figure 8b illustrates a longer section of the offshore cable 100 of Figure 8a, and illustrates three buoyancy members 110 that are axially fixed to the offshore cable 100 with a number of axially moveable buoyancy members 110 being positioned between each pair of axially fixed buoyancy members. In the example of Figure 8a, 1 in 10 of the buoyancy members 110 is shown as being axially fixed on the offshore cable 100, although the skilled reader will realise that other frequencies of axially fixed buoyancy members 150 may be used, such as 1 in 5, 1 in 15, or the like. In addition, it may be possible to have a uniform distribution of axially fixed buoyancy members 150 along the length of the offshore cable 100, or a non- uniform distribution. As in Figure 8a, each of the buoyancy members 110 is in contact with each adjacent buoyancy member 110. As such, axial movement of the moveable buoyancy members 110 is restricted or prevented. Having the configuration shown in Figures 8a and 8b may allow a quicker and cheaper construction of an offshore cable 100 with buoyancy members 110 located thereon, by requiring only some of the buoyancy members to be axially fixed thereon, while still adequately securing the buoyancy members on the offshore cable 100. The offshore cable 100 with buoyancy members mounted thereon 110 as described may be directly wound onto a spool or other cable storage apparatus, thereby removing the need to cease spooling or unwinding of the offshore cable 100 during operations to attach buoyancy members.

Various further inventive aspects and examples according to the present disclosure will now be summarized in the following clauses:

CLAUSE A1. An offshore cable (100) for offshore installation from a vessel, the offshore cable comprising: a cable (100) having a plurality of buoyancy members (110) located thereon; each of the plurality of buoyancy members (110) comprising a longitudinal axis (101), a circumferential surface and two axial surfaces, each of the two axial surfaces comprising a linearly extending portion, extending between the longitudinal axis and the circumferential surface at an oblique angle relative to the longitudinal axis such that the linearly extending portion of a first of the plurality of buoyancy members (110) is configurable to engage the linearly extending portion of a second of the plurality of buoyancy members (110) located adjacent the first buoyancy member (110) upon bending of the cable.

CLAUSE A2. The offshore cable (100) of clause Al, wherein the linearly extending portion of each of the two axial surfaces is oriented such that the axial length (L) of each of the buoyancy members decreases with increasing radial length, from the longitudinal axis to the circumferential surface, such that a radially inner portion (111) of each buoyancy member (110) has a greater axial length (L) than a radially outer portion (112). CLAUSE A3. The offshore cable (100) according to clause A1 or A2, wherein the longitudinal axis of at least one of the plurality of buoyancy members (110) is co-axial with the longitudinal axis of the cable (100).

CLAUSE A4. The offshore cable (100) according to any preceding clause, wherein the offshore cable (100) is wound onto a storage structure.

CLAUSE A5. The offshore cable (100) according to clause A4, wherein the offshore cable is wound such that the first of the plurality of buoyancy members engages the second of the plurality of buoyancy members at the linearly extending portion.

CLAUSE A6. The offshore cable (100) according to any preceding clause, wherein each of the plurality of buoyancy members (110) comprises an extruded shape, such as a cylinder or cuboid.

CLAUSE A7. The offshore cable (100) according to any preceding clause, wherein each of the plurality of buoyancy members (110) comprises an opening (113) for location of the offshore cable (100) therein for the offshore cable (100) which is aligned with the longitudinal axis (114) of each of the plurality of buoyancy members (110).

CLAUSE A8. The offshore cable (100) according to any preceding clause, wherein each of the buoyancy members (110) has the same shape.

CLAUSE A9. The offshore cable (100) according to clause A8, wherein the width (D) of the gap between two neighbouring buoyancy members (110) is smaller than 1 times, 0.9 times or 0.8 times the axial length (L) of each of the buoyancy members (110) measured at the radially outermost position of the buoyancy members (110).

CLAUSE A10. The offshore cable (100) according to any preceding clause, wherein each of the plurality of buoyancy members (110) are axially fixed relative to the offshore cable (100).

CLAUSE A11. The offshore cable (100) according to any of clauses A1 to A9, wherein at least two of the plurality of buoyancy members (110) are axially fixed to the subsea cable (100) and at least one other of the plurality of buoyancy members (110) is arranged between the at least two axially fixed buoyancy members (110).

CLAUSE A12. The offshore cable (100) according to any preceding clause, wherein the buoyancy members (110) are made of a buoyant material. CLAUSE A13. The offshore cable (100) according to any preceding clause, wherein each of the plurality of buoyancy members (110) is axially symmetrical about the longitudinal axis (101) of the offshore cable (100).

CLAUSE A14. A method for installing an offshore cable (100) in an offshore location from a vessel, the method comprising: winding an offshore cable (100) onto a cable storage apparatus (130), the offshore cable comprising a plurality of buoyancy members (11) located thereon, such that a surface of a first of the plurality of buoyancy members (11) engages a surface of a second of the plurality of buoyancy members (11); providing the cable storage apparatus (130) with the wound offshore cable thereon on a vessel; applying tension to the wound offshore cable (100) to unwind the offshore cable from the cable storage apparatus (130).

CLAUSE A15. The method according to clause A14, comprising using a tensioning apparatus (140) to apply a tension to the wound offshore cable (100) to unwind the offshore cable (100) from the cable storage apparatus (130).

CLAUSE A16. The method according to clause A15, comprising using the tensioning apparatus (140) to locate the unwound portion of the offshore cable (100) in an offshore location.

CLAUSE A17. The method according to clause A16, comprising using the tensioning apparatus (140) to axially move the offshore cable (100) so as to position the offshore cable (100) in an offshore location.

CLAUSE A18. The method according to any of clauses A14 to A17, comprising locating the unwound portion of the offshore cable (100) in an offshore location via direct unwinding from the vessel.

CLAUSE A19. The method according to any of clauses A14 to A18, wherein the offshore cable (100) is reeled from the cable storage apparatus (130) at a speed of 0.1m/s, 0.2m/s or 0.5m/s.

CLAUSE A20. An offshore cable (100) for offshore installation from a vessel, wherein the offshore cable (100) comprises: a plurality of buoyancy members (110) located thereon; wherein at least two of the plurality of buoyancy members (110) are fixed buoyancy members and are axially fixed relative to the offshore cable such that axial movement therealong is restricted; and wherein at least one of the plurality of buoyancy members is at least one moveable buoyancy member and is located on the offshore cable axially intermediate the at least two fixed buoyancy members.

CLAUSE A21. The offshore cable of clause A20, wherein the axial movement of the at least one moveable buoyancy member relative to the offshore cable is restricted by the at least two fixed buoyancy members.

CLAUSE A22. The offshore cable of clauses A20 or A21, wherein each of the at least two fixed buoyancy members is in contact with at least one of the at least one moveable buoyancy member.

CLAUSE A23. The offshore cable of any of clauses A20 to A22, wherein each of the plurality of buoyancy members is in contact with two other of the plurality of buoyancy members, and the axial movement of the at least one moveable buoyancy member relative to the offshore cable is restricted by the moveable buoyancy member being in contact with two of the plurality of buoyancy members.

CLAUSE A24. The offshore cable of any of clauses A20 to A23, wherein each of the fixed buoyancy members is axially fixed to the offshore cable by a friction clamp.

CLAUSE A25. The offshore cable of any of clauses A20 to A24, wherein each of the plurality of buoyancy members (110) comprises a longitudinal axis (101), a circumferential surface and two axial surfaces, each of the two axial surfaces comprising a linearly extending portion, extending between the longitudinal axis and the circumferential surface at an oblique angle relative to the longitudinal axis such that the linearly extending portion of a first of the plurality of buoyancy members (110) is configurable to engage the linearly extending portion of a second of the plurality of buoyancy members (110) located adjacent the first buoyancy member (110) upon bending of the cable.

According to a third described example, there is a method for increasing the buoyancy of an offshore cable, comprising: providing an offshore cable with a plurality of buoyancy members located thereon; locating an supplemental buoyancy member on at least one of the plurality of buoyancy members.

According to a fourth described example, there is an offshore cable for offshore installation from a vessel, wherein the offshore cable comprises: a plurality of buoyancy members located thereon, at least one of the buoyancy members being axially fixed relative to the offshore cable; a supplemental buoyancy member located on at least one of the plurality of buoyancy members.

An offshore cable may be produced having a plurality of buoyancy members located thereon. The buoyancy members may assist to provide buoyancy to the offshore cable such that, in cases where the offshore cable (or a section or sections of the offshore cable) has a positive buoyancy, the offshore cable is able to float on the surface of a body of water, such as a sea or ocean surface. In some cases, buoyancy members may be used to provide an offshore cable (or a section or sections of the offshore cable) with a neutral buoyancy such that they are able to be suspended in a body of water without sinking or floating to the surface.

During use of such an offshore cable, there may be cases in which the buoyancy of the offshore cable is desired to be changed. One way of providing a change in buoyancy is to provide a supplemental buoyancy member that may be attached to the offshore cable, and in particular to the existing buoyancy members of an offshore cable. This may allow a user to easily vary the buoyancy of an offshore cable, and may provide a means for varying the buoyancy of only selected sections of an offshore cable.

Such supplemental buoyancy members may be attached, for example, when unwinding a section of offshore cable from a spool or other storage arrangement, the offshore cable may already have buoyancy members attached, and the supplemental buoyancy member may be attached thereto.

Illustrated in Figures 9a and 9b is an offshore cable (not shown for clarity) having a longitudinal axis 201. Located on the offshore cable are a plurality of buoyancy members 210. The buoyancy members 210 are generally cylindrical in shape, with their longitudinal axes aligned with the longitudinal axis 201 of the offshore cable. As is shown, each of the buoyancy members 210 comprises a cylindrical through-bore extending the length of each of the buoyancy members 210 and also aligned with the longitudinal axis 201 of the offshore cable. In use, the offshore cable may extend through the through-bore of each of the buoyancy members 210, such that the buoyancy members 210 may be located (e.g. secured, or affixed) to the offshore cable. As a result of each of the buoyancy members 210 having a through- bore, the buoyancy members 210 may be considered to have the shape of an annular cylinder.

According to this example, at least one of the buoyancy members 210 may be axially fixed relative to the offshore cable. In Figure 9a, two of the buoyancy members 210a are axially fixed to the offshore cable, although in other examples more than two buoyancy members may be fixed to the offshore cable, and this number may increase with increasing length of the offshore cable. The buoyancy members 210a may be axially fixed to the offshore cable by any appropriate means. In this example, the buoyancy members 210a are axially fixed to the offshore cable by means of a cable attachment arrangement 220. The cable attachment arrangement 220 may be or comprise a ring (as in this example) or a clamp and may engage a radially inner surface 222 of the buoyancy members 210a (see Figure 9b). As in this example, the radially inner surface 222 may comprise a surface feature 224 for engagement of the attachment arrangement 220 therewith. Here, the attachment feature is in the form of an annular depression extending circumferentially along the inner surface 222 of the buoyancy members 210a, and which may be engaged by the attachment arrangement 220 to locate (e.g. secure, affix, or the like) the buoyancy member 210a onto the offshore cable. In this case, where the attachment arrangement 220 is in the form of a ring (or generally annular structure), the ring may fit into the circumferential depression of the buoyancy member 210a to axially fix the buoyancy member 210a to the offshore cable. Once the buoyancy member 210a is fixed to the offshore cable, axial movement of the buoyancy member 210 along the offshore cable is restricted or prevented. The attachment arrangement 220 may affix to the offshore cable (e.g. by clamping, bonding, or the like) or may be integrally formed with the offshore cable.

Illustrated in Figures 9a and 9b is a supplemental attachment arrangement 228. In this case, the supplemental attachment arrangement 228 is a ring. The ring may engage a radially outer surface of the buoyancy members 210a, and the buoyancy members 210a may comprise an attachment surface feature on their radially outer surface for engagement of the supplemental attachment arrangement 228. In this example, the attachment surface feature is in the form of a circumferentially extending annular depression 226, and the supplemental attachment arrangement 228 is configurable to fit into the surface feature so as to engage the supplemental attachment arrangement 228 with the surface feature.

Also illustrated is a supplemental buoyancy member 230. Here, the supplemental buoyancy member 230 is generally cylindrical in shape, and comprises a through-bore that extends in line with the longitudinal axis of the supplemental buoyancy member 230. As such, the supplemental buoyancy member 230 has an annular shape and may be considered to be an annular cylinder. In this example, the supplemental buoyancy member comprises a surface feature 232 on a radially inner surface thereof. The surface feature may be used to facilitate engagement of the supplemental buoyancy member 230 with the supplemental attachment arrangement 228. Here, the supplemental attachment arrangement 228 is able to fit into the surface feature so as to engage the supplemental attachment arrangement 228 with the surface feature, and locate (e.g. secure, affix, or the like) the supplemental buoyancy member 230 on the buoyancy member 210a. By attaching the supplemental buoyancy member 230 to the buoyancy member 210a, a user may be able to increase the buoyancy of the offshore cable in a simple manner.

Although, in Figure 9a, only buoyancy members 210a are shown as having an attachment surface feature 226, any of the buoyancy members 210 may have an attachment surface feature, and therefore may be suitable for attaching a supplemental buoyancy member 230 thereto. In addition, although each of the buoyancy members 210/210a, 230 are illustrated as having a single surface feature 224, 226, 232, each of the buoyancy members may comprise more than one surface feature 224, 226, 232. In some examples, a single supplemental buoyancy member 230 may comprise a plurality of surface features 232 that enable attachment of the supplemental buoyancy member 230 to more than one buoyancy member 210. In addition, although the surface features 224, 226, 232 are illustrated as having an axially central location on the buoyancy members, other non-axially centred locations are equally possible.

In this example, only one half of each of the buoyancy members 210 and the supplemental buoyancy members 230 is shown. The buoyancy members 210 and the supplemental buoyancy members 230 may be comprised of two halves (which may be identical) to fit around the entire circumference of the offshore cable. Alternatively, the buoyancy members 210 and/or the supplemental buoyancy member 230 may comprise a single part, or may be comprised of more than two parts, e.g. three or more parts that are able to be fitted together to fit around the entire circumference of the offshore cable.

The attachment arrangement 220 and the supplemental attachment arrangement 228 may be secured to the respective buoyancy member 210a, 230 by means of a friction between the attachment arrangement 220, 228 and the buoyancy member 210a, 230, or may be secured by means of a snap-fit style connection. In other examples, the attachment arrangements 220, 228 may be held in place by bonding, such as chemical bonding, or may be screwed or bolted into place.

The supplemental buoyancy member 230 may be able to be selectively detached (e.g. unfixed) from the buoyancy member 210a on which it is located. This may enable a user to easily vary the buoyancy of the offshore cable, if required. The supplemental buoyancy 230 member may be removed by any appropriate means, for example by applying a radially directed force to the supplemental buoyancy member 230, or by applying a torsional force to the supplemental buoyancy member, for example a torsional force about the longitudinal axis of the supplemental buoyancy member 230.

The buoyancy members 210a that are fixed may vary in buoyancy compared to a nonfixed buoyancy member 210, and in some examples the fixed buoyancy members 210a may be substantially less buoyant, or not buoyant, compared to a non-fixed buoyancy member 210. In such examples, the fixed buoyancy member 210 may essentially be a fixing member 210a, useful for affixing a supplementary buoyancy member 230 thereto and/or useful for preventing or restricting axial movement of the non-fixed buoyancy members 210. The fixed buoyancy member 210a may be constructed from a different material compared to the nonfixed buoyancy members

In the example of Figure 9a, approximately 1 in 10 of the buoyancy members 210a are illustrated as having attachment surface features 226 suitable for attaching a supplemental buoyancy member 230 thereto. However, the skilled person will understand that other ratios of attachment features 226 to buoyancy members 210 may be possible. In addition, there may be an attachment surface feature 226 located on exactly 1 in 10 (or 1 in x number) of buoyancy members 210, or an inexact number of buoyancy members 210 such that the distribution of surface features 226 is not uniform along the length of the offshore cable.

Various further inventive aspects and examples according to the present disclosure will now be summarized in the following clauses: CLAUSE B1. A method for increasing the buoyancy of an offshore cable, comprising: providing an offshore cable with a plurality of buoyancy members located thereon; locating an supplemental buoyancy member on at least one of the plurality of buoyancy members.

CLAUSE B2. The method of clause Bl, comprising locating the supplemental buoyancy member on one of the plurality of buoyancy members, the one of the plurality of buoyancy members being axially fixed to the offshore cable.

CLAUSE B3. The method of clause Bl or B2, wherein the plurality of buoyancy members are cylindrical in shape and are axially aligned with the longitudinal axis of the offshore cable, and the supplemental buoyancy member comprises an annular cylindrical shape and is axially aligned with the longitudinal axis of the offshore cable.

CLAUSE B4. The method of clause B3, comprising providing an attachment arrangement on at least one of: a radially outer surface of at least one of the plurality of buoyancy members for attachment of the supplemental buoyancy member thereto; and a radially inner surface of the supplemental buoyancy member for attachment of the at least one of the plurality of buoyancy members thereto.

CLAUSE B5. The method of clause B4, comprising providing the attachment arrangement on at least one of: a surface feature located on the radially outer surface of the at least one of the plurality of buoyancy members; and a surface feature located on the radially inner surface of the supplemental buoyancy member.

CLAUSE B6. The method of clause B5, wherein the surface feature is an annular groove or depression.

CLAUSE B7. The method of any of clauses B4 to B6, comprising engaging both the at least one of the plurality of buoyancy members and the supplemental buoyancy member with the attachment arrangement.

CLAUSE B8. An offshore cable (100) for offshore installation from a vessel, wherein the offshore cable (100) comprises: a plurality of buoyancy members (110) located thereon, at least one of the buoyancy members (110) being axially fixed relative to the offshore cable (100); a supplemental buoyancy member located on at least one of the plurality of buoyancy members. CLAUSE B9. The offshore cable of clause B8, wherein the plurality of buoyancy members are cylindrical in shape and are axially aligned with the longitudinal axis of the offshore cable, and the supplemental buoyancy member comprises an annular cylindrical shape and is axially aligned with the longitudinal axis of the offshore cable.

CLAUSE B10. The offshore cable of clause B8 or B9, wherein the supplemental buoyancy member has a greater axial length than at least one of the plurality of buoyancy members.

CLAUSE B11. The offshore cable of any of clauses B8 to B10, wherein the supplemental buoyancy member has an axial length approximately equal to the length of four of the plurality of buoyancy members.

CLAUSE B12. The offshore cable of any of clauses Bl to Bll, wherein the supplemental buoyancy member is selectively fixable to the at least one of the plurality of buoyancy members.

CLAUSE B13.The offshore cable of clause B12, comprising unfixing the supplemental buoyancy member from the at least one of the plurality of buoyancy members.

According to a fifth described example, there is a method for attaching a buoyancy member to an offshore cable on a vessel, comprising: providing an offshore cable and at least one buoyancy member on a vessel; locating the offshore cable in a tensioner to hold a portion of the offshore cable in tension on the vessel; locating the at least one buoyancy member on an attachment arrangement, the attachment arrangement being located adjacent the portion of the offshore cable in tension; using the attachment arrangement to attach the at least one buoyancy member to the portion of the offshore cable in tension.

According to a sixth described example there is an apparatus for offloading an offshore cable from a vessel, comprising: a support structure; a conveyor mechanism mounted on the support structure, the conveyor mechanism comprising an endless member configurable to engage and axially displace a section of offshore cable; the conveyor mechanism being configured to engage a section of offshore cable so as to provide a curve in the section of offshore cable.

Such a method may permit an improved way of providing an offshore cable having buoyancy members attached, compared to what is currently available. For example, the method may permit a user to attach a buoyancy member to an offshore cable when both the buoyancy member are positioned on a vessel through use of an attachment arrangement. The attachment arrangement may permit a user to attach the buoyancy member without having to physically handle the buoyancy member. As such, the method may permit a user to attach a buoyancy member in a safer and less laborious way than would otherwise be possible, for example if the user were to have to physically handle the buoyancy member themselves. In particular, this may be a concern if the buoyancy members and/or the offshore cable are particularly large and/or heavy, as this may increase the difficulty for a user in handling the buoyancy members, and the likelihood of injury being cased to a user as a result of handling the buoyancy members.

As will be described, in some examples a user may be able to control the attachment mechanism remotely. This may further decrease the likelihood of injury to a user by permitting a user to attach a buoyancy member to an offshore cable without having to by physically near the offshore cable or the buoyancy member.

Figure 10 schematically illustrates a method for attaching a number of buoyancy members 312 to an offshore cable 14 on the deck of a vessel 322. Although not shown, a tensioner, or similar device for holding the offshore cable 314 in tension, may be located on the deck of the vessel 322 to hold the offshore cable 314 in tension during installation of the buoyancy members 312 thereon. As will be described in more detail in the following paragraphs, the tensioner may be located on the vessel and hold a section of the offshore cable 314 in a horizontal, or approximately horizontal, orientation, while a section of the offshore cable 314 may be hung off the deck of the vessel 322. Tension in the offshore cable 314 may then be achieved by holding a horizontal section of the cable in a tensioner, and allowing the weight of the offshore cable 314 to provide tension therein.

Only a small section of the offshore cable 314 is illustrated for the purposes of clarity. However, the central axis 316 illustrating the axial extension of the offshore cable is illustrated. In this illustration, each of the buoyancy members 312 is substantially cylindrical in shape, and each have an identical shape. Having buoyancy members made of parts of an identical shape may assist in the manufacturing process of the buoyancy members, as it may enable parts to be manufactured more quickly and for lower cost than if each part had a different geometry. However, the skilled reader will understand that other shapes of buoyancy member may be possible, for example other extruded shapes such as a cuboid or triangular prism shapes. Further, the skilled reader will understand that it is not necessary for each of the buoyancy members 312 to be identical in shape. In some examples, having buoyancy members of differing shapes may be beneficial, as it may permit a user to impart differing levels of buoyancy on different sections of the offshore cable, depending on how the geometry of the buoyancy member affects its buoyancy. In addition, the shape of the buoyancy member may affect its handling, and the ability of a user to offload the buoyancy member from a vessel to an offshore location, which may vary depending on the particular structure of the vessel, for example. As shown in this example, several buoyancy members 312 are located on the offshore cable 314, and in this example, the buoyancy members 312 are evenly axially spaced therealong. An even spacing of buoyancy members along the cable 314 may provide a consistent level of buoyancy along the length of the cable 314. An even buoyancy may prevent some sections of the cable 314 from sinking or floating more than other sections, when the offshore cable 314 is in an offshore location, which may prevent the cable from bending excessively, thereby causing damage to the cable. As described in relation to previous examples, although in contrast with this example, the buoyancy members 312 may be positioned on the offshore cable such that each buoyancy member is in contact with each adjacent buoyancy member.

In some examples, the buoyancy members 312 may be arranged on the offshore cable 314 so as to have an uneven spacing along the offshore cable 314. In alternative examples, the buoyancy members 312 may be arranged in groups along the offshore cable 314, with each group comprising a plurality of buoyancy members 312, optionally evenly spaced therealong, and the spacing between the groups of buoyancy members 312 on the offshore cable 314 being at least larger than the spacing between each of the buoyancy members 312 within each group.

Each of the buoyancy members 314 is located on the offshore cable 314 using an attachment device 318. Although not shown in detail, the attachment device may be mechanical and/or robotic in nature, and may for example be an attachment device as described in other examples herein. In addition, the attachment device 318 may be able to be controlled remotely. As such, the attachment device 318 may enable the user to have a high degree of control over the movement and attachment of a buoyancy member 312 to an offshore cable, without having to physically handle the buoyancy member 312. In some examples, the attachment device 318 may be automated to some degree, for example where parts of the attachment process are repetitive or are identical for each buoyancy member 312 (e.g. where each buoyancy member is of an identical geometry). This may permit the process of locating a buoyancy member 312 on an offshore cable 314 to be completed more quickly.

In this example, the attachment device 318 is illustrated as being located adjacent (in this case laterally adjacent) to the offshore cable 314. Although the attachment device 318 is located in Figure 10 on a single side of the offshore cable 314, it may be possible to have an attachment device 318 that is located on either side of the offshore cable 314, which may permit the buoyancy member to be mounted more easily on the offshore cable 314. In such an example, the axial location of each part of the attachment device 318 relative to the offshore cable 314 may be the same.

Illustrated in Figure 10, one buoyancy member 312 is in the process of being located on the offshore cable 314. As shown, the buoyancy member 312 comprises two parts 312a, 312b prior to being located on the offshore cable 314. The two parts 312a, 312b may then be attached or fastened together in order to locate the buoyancy member 312 on the offshore cable 314. The two parts 312a, 312b may be attached or fastened by any appropriate means. For example, the two parts 312a, 312b may be bolted or tied together. In some examples, each of the two parts may comprise a mating surface, and each mating surface may comprise a surface profile which may assist in attaching each of the two parts 312a, 312b together. For example, each part may comprise a dovetail-shaped mating profile 312a, 312b which may fit together to permit attachment of each of the two parts 312a, 312b of the buoyancy members. Although the buoyancy member 312 being located on the offshore cable 314 is illustrated as being constructed of two parts, the skilled reader will understand that it may be possible to construct buoyancy members 312 of any number of a plurality of parts. For example, a buoyancy member 312 may be constructed of three, four or more parts. Having a buoyancy member 312 constructed by a plurality of parts may provide the user benefits such as improving the handling of the buoyancy members 312 prior to installation by allowing the buoyancy members 312 to be transported to a vessel in a more compact configuration. Alternatively or additionally, having buoyancy members 312 constructed of a plurality of parts may provide a user with more flexibility regarding the buoyancy of each module 312 once fully constructed, as (in some examples) it may be possible to construct buoyancy members 312 from a plurality of parts, each part having a different buoyancy.

In order to attach each part of the buoyancy member 312 to the offshore cable 314, the attachment mechanism may comprise a gripping mechanism 320 in order to grip a part 312a, 312b of each buoyancy member. It can be seen in Figure 10 that the gripping mechanism 320 is in the form of a bracket or arm that is able to engage an outer surface of the buoyancy member 312. Gripping of the buoyancy member 312 in by this method may be permitted by operating a gripping arm, or two gripping arms, as pincirs, which may be moved relative to one another to grip the buoyancy member 312. Where the attachment device 318 is located on either side of the offshore cable 314, then there may be two gripping mechanisms 320. In this scenario, each of the gripping mechanisms 320 may grip one part 312a, 312b of each buoyancy member. The two gripping mechanisms 320 may be coordinated so as to bring the two parts 312a, 312b of each buoyancy member 312 together for attachment together.

In the example of Figure 10, the attachment device 318 is able to move each of the parts 312a, 312b of the buoyancy member 312 in a lateral direction in relation to the offshore cable 314. Each of the parts 312a, 312b of the buoyancy member 312 may initially be positioned or mounted on the attachment device 318, and then be moved in a lateral direction (relative to the offshore cable 314) to be brought into engagement. Once each part of the buoyancy member 312 has been brought into engagement, then each part may be attached together to form the entire buoyancy member 312, and may be secured on the offshore cable 314. The attachment mechanism 318 may additionally axially secure the buoyancy member 312 on the offshore cable 314 i.e. secured such that axial movement of the buoyancy member 312 along the offshore cable 314 is not possible. Axially securing the buoyancy member 312 on the offshore cable 314 may be achieved by, for example, providing a fixing member (not shown) on the offshore cable 314 which may be fixed to the offshore cable 314 and may protrude therefrom, abutting against an axially-facing side of the buoyancy member 312 (e.g. where the buoyancy member 312 is cylindrical, the fixing member may abut against a flat, axially-facing side of the buoyancy member). This type of fixing member may be considered to be a fixing collar or bracket on the offshore cable 314. Alternatively or additionally, the buoyancy member 312 itself may comprise a fixing member (not shown) which may prevent axial movement of the buoyancy member 312 on the offshore cable 314. A fixing member comprised (e.g. attached or mounted) on the buoyancy member 312 may be in the form of a collar or bracket. In some examples, both the offshore cable 314 and the buoyancy member 312 may comprise parts of a fixing member, which engage or couple together to prevent axial movement of the buoyancy member 312 on the offshore cable 314.

A fixing member for axially securing a buoyancy member 312 on the offshore cable 314 may additionally by configured to prevent rotational movement of the buoyancy member 312 relative to the offshore cable 314. For example, a fixing member may be rigidly fixed to the offshore cable 314 such that neither axial nor rotational movement of the fixing member is possible. Said fixing member may additionally be rigidly fixed to the buoyancy member 312 to prevent axial and rotational movement thereof. In some examples, one or each of the buoyancy members 312 may comprise a profile for engagement of a fixing member, to assist in attaching and securing the buoyancy members 312 to the offshore cable 314. A fixing member may be secured to a buoyancy member by any appropriate means, for example a fixing member may be chemically bonded, bolted, or the like, to a buoyancy member 312.

Once the buoyancy member 312 has been secured to the offshore cable 314, the offshore cable 314 with the buoyancy member 312 attached may then be moved in an axial direction. Axial movement of the offshore cable 314 may be achieved by operating a tensioner or similar device to allow the cable to move axially along the deck of the vessel 322 under its own weight. Moving the offshore cable 314 in an axial direction may then permit a further buoyancy member 312 (e.g. a second buoyancy member) to be attached to the offshore cable 314, which may be done using the method as already described. Such a process may then be repeated until a desired number of buoyancy members 312 have been attached to the offshore cable 314. A user may be able to adjust the axial spacing between each of the buoyancy members 312 on the offshore cable 314 by varying the degree of axial movement of the offshore cable 314 after each buoyancy member 312 has been attached. In this example, each of the buoyancy members 312 are evenly spaced along the offshore cable 314. However, in other examples other spacings may be provided depending on the desires of the user. For example, it may be beneficial to have unevenly spaced buoyancy members 312, or it may be beneficial to have multiple groups of, for example 5, 10 or more buoyancy members that are evenly spaced. Having flexibility over the spacing of the buoyancy members 312 on the offshore cable 314 may permit a user to adapt the buoyancy of the offshore cable 314 according to their specific needs. For example, the user may require that some sections of the offshore cable 314 are more buoyant than others. It may then be possible to attach more, or a greater density of, buoyancy members to these sections, and fewer buoyancy members to other sections.

In moving the offshore cable 314 axially, both the offshore cable 314 and the buoyancy member 312 may be moved towards an offshore location, which may a location of installation of an offshore structure, such as an offshore power generation plant (e.g. a wind turbine), and away from the deck of a vessel 322. Although not shown, the vessel may comprise a structure to assist in directing the offshore cable 314 from the deck of the vessel 322 to the offshore location. For example, there may be a slide or chute-type structure on the deck of the vessel 322 to assist in lowering the offshore cable 314 from the deck of the vessel 322 to an offshore location. Such a structure may assist in lowering the cable 314 to the offshore location without exceeding the minimum bend radius of the offshore cable 314, and thereby avoiding any damage being caused to the offshore cable 314.

As the offshore cable 314 is moved axially, the orientation of the offshore cable 314 may be changed as it is moved from the deck of a vessel 322 to an offshore location. In this example, the offshore cable, while on the deck of the vessel 322, is generally horizontally oriented. As the offshore cable 314 is moved to an offshore location, the orientation of the cable is changed. Here, the offshore cable 314 is hung off the vessel, such that the orientation of the cable 314 changes from being approximately horizontally oriented to being vertically oriented, with a bent section 326 of offshore cable 314 located between the horizontally and vertically oriented sections 324, 328. The vertical section may then be positioned from a vessel to an offshore location as desired. The skilled reader will understand that, while the horizontal section 324 is illustrated in the horizontal orientation in this example, other orientations may be possible. For example, the actual orientation of the offshore cable 314 in the section 324 on the deck of the vessel 322 may depend on the orientation of the deck of the vessel 322 itself, which may have an incline.

Another illustrated aspect is an apparatus for offloading an offshore cable from a vessel, comprising: a support structure; a conveyor mechanism mounted on the support structure, the conveyor mechanism comprising an endless member configurable to engage and axially displace a section of offshore cable; the conveyor mechanism being configured to engage a section of offshore cable so as to provide a curve in the section of offshore cable.

Figure Ila is a perspective view of one example of an apparatus for offloading an offshore cable 410. The apparatus 410 comprises a support structure 430, which supports a conveyor mechanism 432. In Figure Ila, the conveyor mechanism 432 comprises an endless member 434 in the form of a conveyor belt, which is mounted on the support structure 430.

The support structure 430 comprises a frame 436 which may be used to secure the apparatus 410 in a desired location. For example, the frame 436 may be used to secure the apparatus 410 to the deck of a vessel (not shown). The support structure 430 additionally supports the conveyor belt of the conveyor mechanism 432 in this example, and secures the conveyor mechanism 432 in the desired orientation in relation to the desired location e.g. the deck of a vessel.

In this example, the conveyor mechanism 432 comprises a simple endless member 434, without surface features thereon. The endless member 434 is segmented in this example, which assists in permitting the endless belt to conform to the shape of the support structure 430. The skilled person will understand that other forms of endless member 434 may be possible, such as endless members 434 that are not segmented, or that have surface features thereon, as will be described herein.

As illustrated, the conveyor mechanism 432 comprises a flat section 438, which may be generally horizontally oriented relative to the location in which the conveyor mechanism 432 is located, such as on the deck of a vessel. The flat section 438 is immediately adjacent a curved section 440, which gradually changes the orientation of the conveyor mechanism from the horizontally oriented flat section 438 to a vertically oriented section 442. The curved section 440 has the effect of lowering the offshore cable 414 as it moves with the conveyor mechanism 432, and therefore the curved section 440 may be considered to have a vertical curve. In use, an offshore cable (not shown in Figure Ila) may be positioned on the flat section 438 of the conveyor mechanism 432. The endless member 434 of the conveyor mechanism 432 may move in a direction from the flat section 434 to the vertical section 442, and an offshore cable may be positioned thereon such that the longitudinal axis of the offshore cable is aligned with the direction of motion of conveyor mechanism 432 in this section. As such, an offshore cable positioned on the endless member 434 may be moved axially, and at the same time reoriented from having a horizontal orientation when positioned on the horizontal section 438 to being vertically oriented when positioned on the vertical section 442. Thus, the offshore cable may be positioned easily on the horizontal section 438, for example by a user, and then may be moved axially such that its orientation is changed to vertical by the conveyor mechanism 432.

As described in relation to Figure 10, orienting an offshore cable vertically may facilitate positioning of said offshore cable in an offshore location. For example, the conveyor mechanism 432 may be positioned near the edge of the deck of a vessel, and the conveyor mechanism may be used to offload the offshore cable by permitting it to vertically hang off the edge of the deck of a vessel, for positioning in an offshore location.

In transitioning between the horizontal section 438 and the vertical section 442 is the curved section 440. The curved section may be shaped so that an offshore cable positioned on the conveyor mechanism is reoriented from the horizontal orientation to the vertical orientation without exceeding the minimum bend radius of the offshore cable, thus avoiding damage to the offshore cable. The user may be aware of the minimum bend radius of an offshore cable, as the offshore cable may be rated to inform the user of this information. Knowing the minimum bend radius of an offshore cable, the user will be informed as to whether the apparatus 410 is appropriate for offloading said offshore cable from a vessel.

In addition to reorienting an offshore cable, the apparatus 410 may grip the offshore cable to some degree, as will be described in further detail in relation to the following Figures. It may be necessary for the apparatus 410 to grip the cable, e.g. in the section of the conveyor mechanism extending from the horizontal section 438 to the vertical section 442 to prevent slippage of an offshore cable as it is unloaded from a vessel. In the example of Figure Ila, the change in gradient of the curved section 440 gradually increases in the direction from the horizontal section 438 to the vertical section 442. The gradual increase of the change in gradient of the conveyor mechanism 432 may assist to provide additional grip to an offshore cable mounted thereon, in use.

Although not shown, the conveyor mechanism 432 may be driven by any appropriate means. For example, the apparatus may comprise a motor (not shown) for the purposes of moving the endless belt 434 of the conveyor mechanism 432.

Figure lib illustrates a further example of an endless member 434 of the conveyor mechanism 432. In this example, the endless member 434 is in the form of an endless chain. Here, the endless member 434 comprises a first chain 444 and a second chain 446, with the first chain 444 being parallel to the second chain 446, and the first and second chain being connected by a plurality of connecting members 448, such that a void 450 is formed between two adjacent connecting members 448 and the first and second chains 444, 446. In this example, the connecting members 448 are uniformly spaced along the endless member 434 at regular intervals. The spacing of the connecting members 448 is at least the axial length of a buoyancy member 412 that is located on an offshore cable 414 to be offloaded, and may correspond to the spacing of the buoyancy members 412 on the offshore cable 414. For example, the spacing of the connecting members 448 may be approximately equal to the axial length of a buoyancy member 412 plus the axial length between each buoyancy member on the offshore cable 414.

In use, and as illustrated in Figure 11b, each buoyancy member 412 on the offshore cable 414 may be positioned between two connecting members 448, located in a void 450. The connecting members 448 may come into contact with the offshore cable 414 and optionally the buoyancy members 412 (e.g. an axial surface of the buoyancy members 412). In this way, the conveyor mechanism 432 may provide additional grip to an offshore cable 412 by being able to contact both the offshore cable 414 and the buoyancy members 412 located thereon. This configuration may reduce stress or compression on the buoyancy members 412 caused as a result of tension in the offshore cable 414 forcing the buoyancy member 412 against the conveyor mechanism 432, which may reduce damage to buoyancy members during, for example, offloading from a vessel (not shown).

Figure 12 illustrates a further example of an endless member 534 of a conveyor mechanism. In this example, the endless member 534 may be or comprise and endless belt or an endless chain, and has a plurality of surface features protruding therefrom 552.

The endless member 534 of this example is shown as mounted on the conveyor mechanism of Figure 9a, although the skilled reader will understand that other configurations of the endless member 534 (and of the endless members of Figure Ila and lib) may be possible allowing the endless members to be mounted on structures that are different (e.g. differently shaped) to those described.

Here, the surface features 552 are in the form of fins that extend from the endless member 534. In this example, each of the surface features 552 comprises a base which is attached to the endless member 534, and a tip. The lateral width of the surface features 552 is approximately equal to the lateral width of the endless member 534, such that each of the surface features 552 located thereon span the width of the endless member 534, as can be seen in Figure 10. At the tip of each of the surface features 552 is located a notch 554, which may be semicircular in shape, and may be configured to engage an offshore cable, which may assist to prevent lateral movement of the offshore cable when it is mounted on the endless member 534, as well as improving the grip of the endless member 534 on an offshore cable by increasing the surface contact between the endless member 534 and an offshore cable.

As illustrated, here the surface features are thicker at the base, and gradually narrow towards the tip. An offshore cable 514 is illustrated which comprises buoyancy members 512 thereon. In this example, the buoyancy members 512 are evenly spaced along the length of the offshore cable 514 and the surface features 522 are evenly spaced along the length of the endless member 534 such that, when the offshore cable 514 is mounted on the endless member 534, a buoyancy member is positioned between every two surface features 522. In the illustration of Figure 10, offshore cable 514 is engaged in the notch 554, although the skilled person will understand that there may also be engagement between an axial surface of a buoyancy member 512 and an axially-facing surface of one of the surface features 522. In this configuration, the engagement between the endless member 534 and the offshore cable 514 may be improved, and slippage of the offshore cable 514 on the endless member 534 may be limited by the surface features 552 (for example, because a buoyancy member 512 may abut a surface feature 552). Further, and as is visible in Figure 12, there is no contact between the radially outer surface of the buoyancy members 512 and the endless member 534, which may greatly reduce or prevent compressive forces acting on the buoyancy members 512 as described in relation to Figure 11b.

In this example, the endless member 534 may move the offshore cable 514 in the direction of arrow 556. As with previous examples, endless member 534 comprises a flat horizontal section 538, a curved section 540, and a vertical section 542, for reorienting the offshore cable 514 from a horizontal configuration to a vertical configuration. As can also be seen in Figure 12, the offshore cable at the vertical section 542 is oriented at an angle from vertical. The skilled person will therefore understand that the terms "horizontal" and "vertical" are not used in an exact sense, but rather in an approximate and relative sense, and that therefore the offshore cable may not be located exactly horizontally in the horizontal section 438, 538 or exactly vertical 442, 542, but rather approaching these orientations.

Although not illustrated, there may be an attachment device for locating buoyancy members 512 on the offshore cable 514 located axially prior to the endless member 534 of Figure 12 (in Figure 12, located to the left of the illustration), before the offshore cable 514 is mounted on the endless member 534.

Various further inventive aspects and examples according to the present disclosure will now be summarized in the following clauses:

CLAUSE C1. An apparatus for offloading an offshore cable from a vessel, comprising: a support structure; a conveyor mechanism mounted on the support structure, the conveyor mechanism comprising an endless member configurable to engage and axially displace a section of offshore cable; the conveyor mechanism being configured to engage a section of offshore cable so as to provide a curve in the section of offshore cable.

CLAUSE C2. The apparatus of clause C1, wherein the curve in the section of offshore cable is a vertical curve such that at least one portion of the section of offshore cable has a different vertical elevation than a second portion of the section of offshore cable.

CLAUSE C3. The apparatus of clauses C1 or C2, wherein the endless member comprises at least one of an endless belt and an endless chain.

CLAUSE C4. The apparatus of clause C3, wherein endless member of the conveyor mechanism comprises a curved section for providing a curve in a section of offshore cable that is engaged by the curved section.

CLAUSE C5. The apparatus of clause C4, wherein the curved section of the conveyor mechanism provides a vertical curve in an engaged section greater than a predetermined curve radius of an engaged section of offshore cable.

CLAUSE C6. The apparatus of any of any preceding clause, wherein the conveyor mechanism is configurable to engage a section of offshore cable having a plurality of buoyancy members positioned axially therealong, the plurality of buoyancy members being equally spaced along the section of offshore cable.

CLAUSE C7. The apparatus of any preceding clause, wherein the conveyor mechanism comprises a plurality of protrusions for engaging a section of offshore cable.

CLAUSE C8. The apparatus of clause C7, wherein each of the plurality of protrusions is in the form of a fin.

CLAUSE C9. The apparatus of clause C8, wherein each fin comprises a receiving portion for receiving the section of offshore cable.

CLAUSE C10. The apparatus of clause C9, wherein the receiving portion is in the form of a notch configured to receive a section of offshore cable.

CLAUSE C11. The apparatus of any of clauses C7 to C10, wherein the conveyor mechanism is configurable to engage a section of offshore cable having a plurality of buoyancy members positioned axially and evenly spaced therealong, and each of the plurality of protrusions are arranged on the conveyor mechanism such that one of the plurality of protrusions is positionable between a pair of adjacent buoyancy members of the plurality of buoyancy members.

CLAUSE C12. The apparatus of any of clauses C7 to C11, wherein each of the plurality of protrusions comprises an engagement surface for engaging the section of offshore cable.

CLAUSE C13. The apparatus of clause C1l or C12, wherein each of the plurality of protrusions comprise an engagement surface for engaging at least one of the plurality of buoyancy members, and wherein each of the buoyancy members comprises a corresponding engagement surface for engaging at least one of the plurality of protrusions.

CLAUSE C14. The apparatus of any preceding clause, wherein the conveyor mechanism is configured to provide a curve in the section of offshore cable such that the longitudinal axis of the section of offshore cable directly before or after the curve is vertically oriented.

CLAUSE C15. The apparatus of any preceding clause, wherein the conveyor mechanism comprises a vertically curved section (440) to support a section of offshore cable to permit said section of offshore cable to curve under its own weight.

CLAUSE C16. A method for offloading an offshore cable from a vessel, comprising; providing an offshore cable and an apparatus for offloading the offshore cable according to clause C1 on a vessel; mounting the offshore cable on the conveyor mechanism of the offloading apparatus; operating the offloading apparatus to engage the offshore cable and provide tension in the offshore cable; operating the offloading apparatus to move the offshore cable in an axial direction so as to offload the offshore cable from the vessel an to an offshore location.

CLAUSE C17. The method of clause C16, comprising operating the offloading apparatus to orient the longitudinal axis of the offshore cable in a vertical orientation.

CLAUSE C18. The method of clauses C16 or C17, wherein the conveyor mechanism comprises a plurality of protrusions and the offshore cable comprises a plurality of buoyancy members mounted thereon, and operating the offloading apparatus so as to engage at least one of the plurality of buoyancy members with at least one of the plurality of protrusions.

CLAUSE C19. The method of any of clauses C16 to C18 wherein the conveyor mechanism comprises a plurality of protrusions and the offshore cable comprises a plurality of buoyancy members mounted thereon, and mounting the offshore cable onto the conveyor mechanism such that at least one of the plurality of protrusions is located between at least two of the plurality of buoyancy members.

CLAUSE C20. A method for attaching a buoyancy member to an offshore cable on a vessel, comprising: providing an offshore cable and at least one buoyancy member on a vessel; locating the offshore cable in a tensioner to hold a portion of the offshore cable in tension on the vessel; locating the at least one buoyancy member on an attachment device, the attachment device being located adjacent the portion of the offshore cable in tension; using the attachment device to attach the at least one buoyancy member to the portion of the offshore cable in tension.

CLAUSE C21. A method according to clause C20, wherein the at least one buoyancy member is provided in at least two parts, optionally wherein the two parts are identical parts.

CLAUSE C22. A method according to clause C21, wherein the attachment device comprises a first and a second attachment device, and wherein the first attachment device and the second attachment device are each located adjacent the portion of the offshore cable in tension, and using the first attachment device to attach a first of the at least two parts of the buoyancy member, and using the second attachment device to attach a second of the at least two parts of the buoyancy member.

CLAUSE C23. A method according to clause C22, wherein the first and second attachment devices are located on opposite sides of the offshore cable.

CLAUES C24. A method according to any of clauses C20 to C23, comprising remotely operating the attachment device to attach the at least one buoyancy member to the offshore cable.

CLAUSE C25. A method according to any of clauses C20 to C24, wherein the attachment device is a robotic mechanical attachment device.

CLAUSE C26. A method according to any of clauses C20 to C25, wherein the attachment device is an automated attachment device.

CLAUSE C27. A method according to any of clauses C20 to C26, comprising using the attachment device to attach a second buoyancy member to the portion of the offshore cable in tension.

CLAUSE C28. A method according to any of clauses C20 to C27, comprising using the tensioner to move the offshore cable in an axial direction; and using the attachment device to attach a second buoyancy member to the portion of the offshore cable in tension, the second buoyancy member having a different axial location to the first buoyancy member.

The person skilled in the art realizes that the present disclosure is not limited to the preferred embodiments described above. The person skilled in the art further realizes that modifications and variations are possible within the scope of the appended claims. For example, features disclosed in relation to one aspect may be used in combination with a separate aspect such as an offshore cable as described in relation to Figure 1 being used in combination with the apparatus of Figure 11. Additionally, variations to the disclosed examples can be understood and effected by the skilled person in practicing the claimed disclosure, from a study of the drawings, the disclosure, and the appended claims.