WO2008139190A1

WO2008139190A1 - Apparatus for deploying underwater cables and methods of deployment of underwater cables

Info

Publication number: WO2008139190A1
Application number: PCT/GB2008/001658
Authority: WO
Inventors: Jeremy John Richard Featherstone
Original assignee: Blue Ocean Projects Ltd
Priority date: 2007-05-15
Filing date: 2008-05-14
Publication date: 2008-11-20
Also published as: GB0709274D0

Abstract

In renewable energy turbine farms, problems arise in routing cable to and from individual support structures in shallow water, especially around the base of the turbine, where scour may occur in the bed of the shallow water. Apparatus and a method are provided to deploy cable (100) to the bed of the shallow water, in which the cable is pulled in through a guide (10) by pulling-in a detachable device (2) attached to the cable, as well as a connector (3), which is connected to the pull-in device (2) and has a through-passageway (110a), and a protective sleeve (4), which is attached to the connector and also has a through- passageway (110b), until the connector fastens via a push-fit action to the guide on or adjacent the support structure, thereby also deploying the protective cable sleeve between the connector and the bed of the shallow water and providing a protected cable route between the guide and the bed of the shallow water. The protective sleeve means is formed from a series of interconnected successive sleeve shells and each interconnection may be corrodible.

Description

PATENT SPECIFICATION

TITLE:

APPARATUS FOR DEPLOYING UNDERWATER CABLES AND METHODS OF DEPLOYMENT OF UNDERWATER CABLES

DESCRIPTION:

TECHNICAL FIELD

The present invention relates to apparatus for deploying underwater cables and methods of deployment of underwater cables in shallow water. This invention particularly relates to deploying cables to a support structure disposed in shallow water, typically sea, river, estuary or lake. By shallow water is meant water typically up to about 200 metres deep. The support structure may for instance be embedded in the bed of the body of water or it may be moored, or gravity-based seated on the bed of the body of water.

The term "cable" throughout this specification should be taken to include any elongate device having a transmission function. Such elongate transmission devices are usually flexible. More specifically the cable may include power cable, risers, umbilicals, and combinations of any of these.

BACKGROUND OF THE INVENTION

Cables are often required to be routed underwater from a support structure and along the bed of the body of water, either to another support structure or ashore. Examples of cable which may be deployed according to the invention are umbilicals extending from an offshore hydrocarbon production platform structure to another platform or to a subsea structure such as a control valve, and power or control cables between offshore structures, and to the shore, for wave and tidal power projects.

The support structure to which the cable is deployed may comprise a renewable energy turbine. For example, cable may be deployed to a wind turbine, which is desirable to be not only economically installed but also economically maintained after installation. Wind farms having tens and even hundreds of turbines are being used worldwide to produce electricity: the world's largest offshore wind farm has been planned to be built 12 miles off the Kent coast and will include 341 turbines. More particularly the present invention relates to both offshore wind turbines (10 or more than 10 km from land) and nearshore (less than 10 km from land) .

In such relatively shallow water where wind turbines are deployed there are various factors affecting stability of the turbines and of the power transmission cabling between wind turbines: these include movements of material on the bed of the body of water (seabed, riverbed or lakebed) owing to currents, waves and turbulence and the nature of movable material on the bed. Hitherto, rock has been brought and deposited by wind farm builders to cover unstable areas and protect cable for example.

Typically in such arrangements, cable is guided predominantly vertically down the inside or outside of the support structure, usually from an access platform above the surface of the water, in a pre-installed generally vertical rigid hollow guide conduit to a location adjacent the bed of the body of water. One common form of guide conduit is known as a "J- tube", having a predominantly vertical portion leading to a curved portion at its lower end, whereby the cable typically exits between 45 degrees and 0 degrees to the horizontal. An alternative guide conduit is an "I-tube" which is predominantly vertical only without a curved portion at the lower end.

Cable may be installed by pulling the end of the cable into the conduit using a pre-installed pulling wire or messenger wire at the bed end of the conduit so that the cable can then be pulled in from above, through the lower end of the conduit to the upper end of the conduit, where it can be hung off. In a wind farm, for example, each turbine may have two or more guide conduits, for communication with other turbines. Beyond the lower end of the guide conduit the cable usually lies along the bed of the body of water, buried 1-3 metres deep therein.

Problems have commonly occurred in the transition zone between the lower exit of the guide conduit and the bed of the body of water, both during installation, and during service. The following two examples demonstrate this .

On one offshore wind turbine project employing a J-tube for cable for transmitting power created by the wind turbine, cable laying "became time consuming because of the use of divers to locate and feed the cable up the J-tube, Due to strong tidal currents the divers could only work for short periods of slack water either side of the high and low tides, and then only in very benign wave climate" (DTI report URN 06/31a62 p5 on the Scroby Sands wind farm project) .

The Blyth Harbour offshore wind farm project suffered a serious problem in the transition zone. A J-tube was employed which was disposed down to close to the sea bed; the cable faulted because the "cable protection where the cable left the J- tube came loose and slipped down the cable. The current then caused the cable to wear on the end of the J-tube and the cable was cut through ... the cable was out of service for approximately three months". The cable was repaired with "support at the entrance to the J-tube provided by shaped cement-filled bags." The report concluded that "the detail of the cable entry is very important" (DTI report URN 04/1052 p5 "Blyth Harbour Wind Farm - Operational Aspects") .

Other problems occur around the base of the support structure on the bed of the body of water. The height of the J tube above the seabed may not be accurately known in advance of the cable installation not only because of intrinsic tolerances in the piling/ structure installation processes but also because there may be significant scour of the seabed local to the structure, especially around monopile (a single upright member embedded in the bed of the body of water) structures. Scour tends to take place when a structure is first installed on the seabed since local water currents are changed, usually increasing, by the new presence of the structure, which may result in loosening of seabed materials, stable prior to installation of the structure. Thus, seabed materials may be eroded, resulting in lowering of the seabed near the structure and a scour hole may develop around the base of the structure on the bed of the body of water. Scouring may not only destabilise the support structure but also leave the cable suspended at the exit from the guide conduit and the suspended portion of cable may strum (vibrate) and fail from fatigue or abrasion at contact points. This is a particular problem for wind turbines as the turbine would no longer export energy.

One solution has been to provide J-tubes to allow for adjustment of the final exit elevation and angle, including telescopic or hinged sections, which can be locked in place by divers after installation. Another solution is to protect the lower exit end of the J-tube as well as the base of the support structure with gravel or rock to avoid horizontal motion of the exit end of the J-tube and the exiting cable may be fixed on the seabed with dumped rock. At Blyth this was not done after the initial installation, resulting in costly repairs. The disadvantage of such solutions is that considerable costly diver intervention is generally required. It is an object of the invention to overcome drawbacks mentioned above.

SUMMARY OF THE INVENTION

According to one aspect of this invention we propose apparatus for deploying an underwater cable between a support structure disposed in shallow water and the bed of the shallow water, comprising: a connector comprising a forward portion and a rearward portion, the forward portion including a device to fasten, via a push-fit action, to a guide on or adjacent the support structure, the connector having a through-passageway, a cable pull-in device for attachment to the cable, the pull- in device also being connected to the connector via a detachable link for pulling cable through the guide and the connector, and, connected to the rearward portion of the connector, a protective sleeve, also having a through-passageway, for receiving the cable, to provide a protective cable route between the connector and the bed of the shallow water.

This apparatus allows efficient installation of both underwater cable and the attached protective cable sleeve onto the support structure in shallow water without the use of diver assistance. This results in a quick-deploy arrangement, allowing effective installation of cables on groups of support structures requiring en masse repetition of an installation procedure, such as for wind farms . This will result in savings in deployment time and costs. Moreover, a protective sleeve long enough to extend to the seabed once fully deployed may be obtained.

Furthermore, the through-passageways of the connector and sleeve may be in in-line communication to allow the passage of cable therethrough, so that the cable can be pulled highly effectively by the pull-in device through both the connector and the protective sleeve on detachment of the pull-in device, both to deploy a first portion of the cable to the support structure and to deploy a portion of cable following the first portion to the bed of the shallow water in the protected cable route. Thus, the quick-deploy arrangement provides an effective single procedure.

The guide may be a conduit on or adjacent the support structure; the guide conduit may have an upper exit and a lower exit. The guide conduit may comprise a predominantly vertical tube and the cable may extend out of the upper exit of the guide conduit to the support structure. Hence, the connector may also serve to centralise the cable within the guide conduit. The connector may be preassembled over the cable prior to deployment and may be attached to the pull-in device via a first attachment member, such as a shackle. The pull-in device may be attached to the cable via a second attachment member, such as a pulling eye, which is also attached to first attachment member.

The detachable link may comprise a frangible weak link which can be broken automatically while the cable is being pulled in. This further assists in hastening the installation operation. Thus, an effective installation on the support structure is possible together in the same procedure as effective deployment of the protective sleeve to the bed of the body of shallow water.

The protective sleeve may be articulated and comprise a series of successive, interconnected sleeve shells or units. This provides an adaptable sleeve, which may adopt elongate shapes according to variations in shape of the seabed.

Each interconnection of the sleeve shells may comprise corrodible interconnecting members, which allow the sleeve to become permanent or semi-permanent. This provides effective protection from external influences to the cable inside the sleeve. The interconnecting members may comprise a ball and socket arrangement or other pivotable arrangement. Once installed, the balls and sockets or other pivotable devices will corrode together and hence form a rigid pipe to act as the protective housing for the cable between the guide conduit, through the scour zone and onto the seabed.

The sleeve units and the interconnecting members may all be made from corrodible metal, such as cast iron. They may be lined with a low friction polymer, such as polyethylene to minimise the frictional forces during the cable pull through, or made from a single polymeric material such as polyurethane .

The forward portion may be at one end of the connector and the rearward portion at the other end of the connector. The protective sleeve may also act as a bend limiter, which avoids over-bending the cable.

The connector may further include an abutment surface between the connection to the guide on the forward portion and the connection to the sleeve on the rearward portion, for abutting the guide and for limiting forward movement of the connector through the guide, thereby locating the connector in the guide.

The fastening device may include at least one releasable fastening member, which is releasable from a first position, in which the connector is movable through the guide, to a second position, in which the connector is fastened to the guide, so as to co-operate with the guide to hold the weight of the connector and the sleeve connected to the connector.

The at least one releasable fastening member may be provided by a plurality of sprung latches on the connector, actuated on pulling-in the connector (and co-operative with an abutment surface on the guide or with the internal sidewall of the guide) or an external clamp.

The guide conduit may comprise a predominantly vertical tube. The guide conduit may comprise an I-tube or a J-tube. The pull-in device works effectively in combination with the guide conduit and provides a protected routeway for the cable from the guide conduit.

The support structure to which the cable is deployed may comprise a renewable energy turbine. In particular, the above apparatus may be effectively employed for use in routing underwater cable to and/or from and/or between offshore/nearshore wind, wave or tidal turbines. Furthermore, the protective sleeve may extend from the lower exit of the guide conduit at least onto the bed of the body of water. Moreover, the protective sleeve may extend through the potential scour zone around the support structure. This further assists in protecting the cable and in providing reliable cabling. Thus, the assembly may comprise apparatus as above described, in which the connector is connected with a guide on or adjacent a support structure in shallow water and the protective sleeve and cable received therein are deployed between the guide and the bed of a body of shallow water.

According to another aspect of the invention, we propose a method of deploying a cable in a protected cable route between a support structure deployed in shallow water and the bed of the shallow water, comprising: pulling-in a detachable device attached to the cable, a connector, which is connected to the pull-in device and has a through-passageway, and a protective sleeve, which is attached to the connector and also has a through-passageway, until the connector fastens via a push-fit action to a guide on or adjacent the support structure, thereby also deploying the protective cable sleeve between the connector and the bed of the shallow water, thus providing a protected cable route between the connector and the bed of the shallow water.

Thus, a protected cable route may be effectively obtained by the above pulling-in procedure according to the invention, providing protection from the support structure all the way to the bed of the bed of shallow water. With this method, efficient installation of both underwater cable and an attached protective cable sleeve onto a support structure is possible in shallow water without or with little diver assistance. Thus, a single quick-deploy procedure is allowed. This has the benefit of allowing effective installation of cables on groups of support structures requiring en masse repetition of an installation procedure, such as for wind farms. This will result in savings in deployment time and costs.

The method may further comprise pulling in the connector until an abutment surface thereon abuts an abutment surface on the guide, thereby limiting onward movement of the connector.

The method may further comprise pulling in the connector until at least one releasable fastening member on the connector is released and acts on the connector so as to co-operate with the support structure to hold the weight of the connector and the sleeve and thereby fasten the connector and the sleeve to the connector.

The method may further comprise pulling-in the cable further until the pull-in device is detached. The detachable link may comprise a weak link which can be broken automatically while the cable is being pulled through the guide conduit. This further assists in hastening the installation operation.

The method may further comprise pulling-in the cable further and allowing the cable to be pulled out of the guide, which may be a conduit, and hung off at the support structure.

The connector may be preassembled over the cable prior to deployment. The method may further comprise laying the cable and the protective sleeve so as to together lie on the bed of the shallow water.

Hence, not only may both the cable and the cable protector sleeve may be each highly effectively deployed to the support structure but also a protected cable route may be provided together in the same procedure to the bed of the shallow water. Moreover, this may be achieved in a single quick-deploy-quick- install operation. This will allow the procedure to be replicated efficiently for a group of structures such as turbines in an offshore/ nearshore wind farms.

The method may further comprise laying the cable and the protective sleeve together through the potential scour zone around the support structure. Thus, the cable sleeve offers effective protection to the cable through the scour zone on the seabed. The weight of the sleeve during pull-in may be supported temporarily by an additional line and/or a buoy.

We also propose apparatus for deploying an underwater cable between a support structure disposed in shallow water and the bed of the shallow water, the support structure including a cable guide conduit having an upper exit and a lower exit, comprising: a connector to fasten, via a push-fit action, to the guide conduit, the connector having a through-passageway, a cable pull-in device for attachment to the cable and movable through the guide conduit, the deployment device being connected to the connector via a detachable link, and, a protective sleeve having a through-passageway for housing the cable to provide a protected cable route between the connector and the bed of the shallow water, the through-passageways being in communication so that the cable can be pulled by the deployment device through both the connector and the protective sleeve on detachment of the deployment device, both so as to deploy the cable to the support structure via the guide conduit and to the bed of the shallow water in the protected cable route. We further propose apparatus for deploying an underwater cable between a support means disposed in shallow water and the bed of the shallow water, comprising: connector means comprising a forward portion and a rearward portion, the forward portion including a device to fasten, via a push-fit action, to guide means on or adjacent the support means, the connector means having a through-passageway, cable pull-in means for attachment to the cable, the pull-in device also being connected to the connector means via detachable link means for pulling cable through the guide means and the connector means, and, connected to the rearward portion of the connector means, protective sleeve means, also having a through-passageway, for receiving the cable, to provide a protective cable route between the connector means and the bed of the shallow water.

The detachable link means may comprise a frangible link which can be broken automatically while the cable is being pulled in.

The protective sleeve means may comprise a series of interconnected successive sleeve shells. Each interconnection of the sleeve units may comprise corrodible interconnecting means.

The forward portion may be at one end of the connector means and the rearward portion at the other end of the connector means. The connector means may further include means providing an abutment surface between the connection to the guide means on the forward portion and the connection to the sleeve means on the rearward portion, for abutting the guide means and for limiting forward movement of the connector means through the guide means, thereby locating the connector means in the guide means .

The fastening means may include at least one releasable fastening means, which is releasable from a first position, in which the connector means is movable through the guide means, to a second position, in which the connector means is fastened to the guide means, so as to co-operate with the guide means to hold the weight of the connector means and the sleeve means connected to the connector means.

The apparatus may be for routing underwater cable to and/or from and/or between of f shore/nearshore wind, wave or tidal turbines .

We further propose an a s s embly compri s ing a support structure in shallow water , a cable guide conduit on or adj acent the support structure and having an upper exit and a lower exit ; a connector including a through-aperture and fastened at one end to the lower exit of the guide conduit via a push-fit action; and a protective sleeve connected to the connector and having a through-aperture in communication with the through- aperture of the connector so as to provide a protective cable route between the connector and the bed of the shallow water.

The protective sleeve may comprise a series of interconnected successive sleeve units, the sleeve extending from the lower exit of the guide conduit at least onto the bed of the body of water.

The features described above offer improved ease of installation, with greatly reduced dependency on diver intervention compared to existing methods. It also offers improved protection during operational life of the cable. There are likely to be considerable savings in deployment time, which is very beneficial for mass installations such as renewable energy turbines, for example wind farms.

References in the specification to seabeds should be taken to cover the beds of other bodies of shallow water, for example a lakebed or riverbed. BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described by way of example, referring to the drawings (not to scale), in which:

Figure 1 is a diagrammatic sectional view of apparatus for deploying an underwater cable, including a pull-in device, and having a connector and a protective sleeve, attached to a guide conduit, which is disposed on or adjacent a support structure disposed in shallow water;

Figure 2 shows in more detail the pull-in device and a second embodiment of the connector, with the leading end of the protective sleeve and the cable attached to the connector and pull-in device (the rest of the sleeve and the guide tube are omitted) ;

Figure 2a is a diagrammatic sectional view showing the forward end of the cable only, with a cable grip fastening mechanism for the cable to the pull-in device; Figure 3 shows in detail a frangible pin device for use to link the pull-in device and the connector;

Figure 4 is a diagrammatic exploded view showing the connector and adjoining protective sleeve portion;

Figures 5, 6 and 7 illustrate a cable deployment apparatus, a static support structure, with a guide conduit, on the seabed and illustrate a method of cable deployment to the guide conduit and the support structure;

Figure 8 shows a sectional detailed view of the connector and adjoining protective sleeve portion of Figures 2, 3 and 4 engaged in the guide conduit of Figure 1;

Figure 9 shows a sectional detailed view of second embodiment of a connector employed in the cable deployment apparatus according to the invention;

Figure 10 shows a sectional detailed view of a third embodiment of a connector employed in the cable deployment apparatus according to the invention;

Figure 11 is a flow chart illustrating the steps of a method of cable deployment according to the invention; and

Figure 12 shows an optional temporary support line fitted to a cable protector sleeve for use with the cable deployment apparatus of the earlier Figures.

BEST MODES OF CARRYING OUT THE INVENTION

Referring to Figure 1, cable deployment apparatus (1) consists of a pull-in device (2), a connector (3) and a sleeve (4) . This apparatus (1) is employed to deploy a cylindrical power transmission cable from a shallow water support structure (500), for example as shown in Figures 5 to 7, belonging to a wind turbine. A predominantly vertical I-tube (10), acting as a guide conduit with a cylindrical through-passageway (110) along the tube, is externally attached to the side of the support structure via brackets (7), as shown in Figures 5 to 7. The arrow F throughout the figures indicates the direction of pull-in of cable .

In the first embodiment, shown in Figure 1, the lower end of the I-tube (10) is terminated with a peripheral flange (9) onto which is bolted a circumferential latching ring (11). In this embodiment the latching ring includes a downwardly-flared guide cone (13) .

Referring to Figures 2 and 4, the connector (3) has a generally cylindrical body, made from identical hemi-cylindrical shells (31a and 31b), which circumferentially wholly surrounds a longitudinal portion of the cable. The connector (2) has a portion (5) at its forward end (8a) and another portion 6) at its rearward end (8b), with an intermediate portion (7) between the forward and rearward portions (5, 6) . The forward end portion (5) of the connector is fastened to the support structure (500) and the rearward end portion (6) is attached to a protective sleeve (4) provided by an articulated bend limiter for protecting the cable. As indicated in Figure 8, the forward end portion (5) of the connector (3) has a conical leading nose section (32), to ease entry into the lower end (14) of the aforementioned I-tube (10) on the support structure (500), a plurality of forwardly tapered retractable sprung latching members or dogs (33), and an external circumferential skirt providing a leading abutment surface (34).

At its downward end the connector has a ball joint connection

(35) to the first protective shell (41), provided by mating corrodible cast iron identical half-spherical ball joint connections (35a, 35b) (see Figure 4) .

Figures 1 and 2 illustrate in more detail how the successive shells (41) of the sleeve are connected to the connector (3) and then link together to form the central longitudinal passageway (110) for surrounding the cable. The protective bend limiter (4) is provided by a series of individual identical interconnecting sleeve shell units (41) , themselves each provided by a pair of inter-engaging, complementary, hemicylindrical corrodible cast iron shells (41a, 41b) , for providing continuous circumferential protection. These shells

(41) each have a ball joint (42) at their forward end, formed by mating corrodible cast iron identical half-spherical ball joint connections (42a, 42b), with an internal recess (43) provided by identical internal half-recesses (43a) and (43b) . At their rearward ends the shells (41) each have a smaller ball joint (44), formed by smaller mating corrodible cast iron identical half-spherical ball joint connections (44a, 44b); the downward end ball joints (44) are each seated in the respective forward end recess (43) of the following shell in order to link adjacent shells (41) .

The split half shells (41a, 41b) are assembled over the cable (100) a distance of typically a couple of metres from the cable end to be pulled in to the guide conduit, and connected together by co-operative pairs of bolts and nuts (47, 48), here made of stainless steel.

The assembled series of shells (41) forms a protective cable sleeve (4), for example as shown in Figures 2 and 5. The connector (3) and the protective sleeve (4) have in-line communicating cylindrical through-passageways (110a, 110b) providing a hollow longitudinal portion (110), shown in Figure

2a, through which the cable can freely slide. The corrodible nature of the sleeve allows a permanent or semi-permanent protective unitary cover structure around the cable to be formed.

In Figures 2 and 4 only the first one or two cable protectors (41) are shown for simplicity; in practice the number of cable protectors (41) will depend on the distance required to be covered application but could range up to many hundreds, with a typical average number of around twenty. A typical length for each protective shell may be from around 200 to around 700 mm.

In one effective arrangement a sufficient number of protective shells (41) is provided to form a 180 degree segment, when the bend limiter apparatus is at or near the lock out radius, as this will lead to a balanced vertical entry angle of the connector (3) into the lower end of the I-tube during installation. In Figure 6, ten protective shells (41) are shown, forming a semi-circle during laying and they are shown laid out in Figure 7, joining the support structure (500) to the bed (B) of the shallow water.

The cable protectors half-shells (41a, 41b) may alternatively be made from carbon or stainless steel or a polymer such as polyurethane. The cable is free to slide within the articulated sections. This may be facilitated by lining the inside of each half shell with a low friction material such as polyethylene.

The assembly of articulated shells (41) "locks out" at a radius equal or greater than the minimum permitted bend radius for the cable. The shells (41) also protect the cable from other external influences such as mechanical impact or seabed current or wave induced vibration damage, and provide additional weight and hence increased stability in seabed currents. All these features reduce the risk of damage to the cable.

As seen in Figure 2, at the leading end (19) of the cable the pull-in device (2) includes a pulling eye (16), which may be provided by fashioning the ends of the internal cable armour wires into an eye, or by the use of a conventional cable grip (also known as a pulling stocking, Kellums grip or Chinese fingers) applied over the cable end, or it may be a pulling head secured on the end of the cable armour wires. If the pull-in device (2) is kept within the diameter of the cable, a unitary connector may be employed, rather than two split halves (31a, 31b) .

The pull-in device (2) also includes a pull-in shackle (17) attached to the pulling eye (16) as well as a plurality of additional actuation wires (18) also attached to the pull-in shackle, leading to the fastening device.

Another cable fastening mechanism is illustrated in Figure 2A, in which a stocking (20) tightly fits over the forward end (19) of the cable and is attached to the pulling eye (16) via a joining member (21) . The pull-in wires (18) are each attached to respective eyes via respective joining members (22) . Each wire (18) is terminated at the connector end into a swage socket (35) (shown in Figure 3) , in a guide rod (36) (this may be cylindrical, square or rectangular in cross section) and is linked to the connector via a longitudinally-disposed, weak link shear pin (37) designed to shear at a certain preset axial tension in the wire (see Figures 2 and 3) .

The guide rods (36) are intended to fit into recesses (49) in the connector so that any side loads are absorbed into the body of the engaging piece. Such side loads may be due to misalignment during engagement. Hence shear pins (37) are subjected to axial load only, which increases once the connector is correctly aligned inside the I-tube.

The connector is for example made of carbon steel or stainless steel, or may be made from a polymer such as polyurethane . The I-tube is for example made of carbon steel and has an internal diameter 500-70mm, typically 300mm, with a wall thickness of around 20mm. The cable (100) diameter may typically be in the range 60mm to 180mm. The support wire (18) diameter may typically be in the range 6mm to 25mm. As shown in Figures 5 to 7, the end of the cable (100) to be installed on the support structure (500) is prepared on the deck of a cable lay vessel (51) .

The sequence of deployment of the cable (100) using the deployment device (1) onto the support structure (500) is as follows :

The lower end (70) of a deployment messenger line (50) (which has been pre-installed in the I-tube) is passed to the cable lay vessel (51) and joined to the pull-in shackle (17) (see Figure 5) .

Tension is now increased on the messenger line (50) (this is done either via a winch on the support structure (500) or by a tow wire connected from the surface end of the messenger line over a roller quadrant (not shown) or sheave block (not shown) , back to the cable lay vessel). The deployment device (2) and attached cable (100) are over-boarded and pulled in towards the support structure (500) until the connector (3) enters the bottom exit (14) of the I-tube, referring to Figure 6. The resilient latch dogs (33) are squeezed in as they pass over the latching ring, and then released outwards once they pass beyond the latching ring (11). This provides a quick-connect, quick-install push-fit action. Referring to Figure 8, as the messenger line (50) is now pulled further in, the abutment reaction surface (34) comes into contact with bottom face (38) of the I-tube latching ring (11).

The tension in the pin wires (18) between the pull-in shackle (17) and the connector (3) rises until the frangible pins (37) break. The combination of the connector (3) and sleeve (4) then drops a short distance (typically about 5mm-44mm) under gravity until the latching dogs (33) are engaged against the top face

(39) of the latching ring (11) (see Figure 8) and is left behind.

Now the pull-in shackle (17) is no longer connected to the connector (3) and, after the messenger line (50) is pulled in further, the cable (100) is pulled through the connector (3) and the articulated bend limiter (4), until the pull-in shackle (17) and leading cable end (19) come out of the top exit (27) of the

I-tube (10), which may be adjacent an access platform (not shown) on the support structure. The cable (100) at the top of the I- tube can now be terminated ( ^λhung off ) by conventional means, and the messenger line (50) disconnected.

As seen in Figures 6 and 12, during the pull in process the weight of the tail end of the articulated bend limiter (4) may be supported by a temporary line (55) held under tension at the cable installation vessel (51) . Prior to launch, the temporary line (55) is fed through an eye (56) fitted to a circumferential strap (57) which is able to rotate around the articulated bend limiter (4) . This helps to minimise the pull force required to pull the cable (100) through the articulated bend limiter (4). A buoy (not shown) may be used in place of, or in addition to, the temporary line. Once the pull in is completed, the temporary line (or buoy) is let go at one end on the vessel and then pulled out through the eye (56) and recovered back to the installation vessel .

The cable installation vessel (51) now starts to move away from the support structure (5) so as to lay the cable (100) away from the structure (5) and as a result the articulated bend limiter (4) falls to the seabed (see Figure 7).

Typically the cable will be buried into the seabed from the end of the articulated bend limiter/cable protector section. The articulated bend limiter/cable protector (4) may be made from a corrodible material, such as cast iron or carbon steel, in order that the ends corrode together in service to form a rigid conduit pipe shaped accordance to the cable.

Thus, as illustrated in Figure 11, in summary the steps of the above method are as follows:

STEP 1 pulling, with a pull-in device (2), a deployment cable (50) into the lower exit (14) of the guide conduit (10),

STEP 2 connecting the leading end (19) of the cable (100) to be deployed to the trailing end (70) of the deployment cable (50) ,

STEP 3 pulling the deployment cable (50) through the guide conduit (10) until the connector (3) fastens via a quick-connect push-fit action onto the guide conduit, thereby at the same time also deploying the protective cable sleeve (4) between the connector and the bed of the shallow water and providing a protected cable route between the guide conduit and the bed,

and

STEP 4 pulling the deployment cable (50) further through the guide conduit until the pull-in device (2) is detached from the connector (3) and until the leading end (19) of the cable (100) is pulled out of the upper exit (27) of the guide conduit.

Therefore, with the method described above it is possible to both install the cable into the guide conduit with little or no diver intervention and to apply protection around the cable from the guide conduit to the seabed without diver intervention. Hence protection has been achieved in a single quick-deploy procedure with and more or less simultaneously with installation, thus ensuring that the cable is protected throughout the transition zone between the lower end of the guide conduit and the seabed.

With the above apparatus and method of deployment, the difficulty of the distance of the lower end of the guide conduit from the seabed is overcome. Furthermore, the cable has been bent within the bend limiter only, so there is minimal risk of violating the minimum bend radius of the cable during installation onto the structure.

In the above embodiment a latching system is described in which where sprung latch dogs are mounted on the male connector (3) . However other arrangements may be employed: one option is to mount the sprung dogs radially on the female I- tube, to then engage under a lip on the male engaging piece. Another would be to change the shape of the connector (3) such that it has sprung dogs mounted externally, so that they engage on an external rather than internal latching ring on the I-tube, which allows a smaller I-tube to be used and may provide better access for removal but also may be more prone to picking up silt or other seabed sediment during deployment.

Δ second embodiment of connector is shown in Figure 9. The principle of operation of the apparatus and frangible weak link is similar to that described above, except that there is no flange at the lower exit of the guide conduit (10) but the connector has an external circumferential flange (54) to limit upward movement of the connector. The sprung latches (33) engage with the inside peripheral wall (72) of the I-tube, as shown in

Figure 9. Thus, again there is a quick-connect, quick-install push-fit action.

In this case the sprung dogs may again be discrete members as described above, or they may be circumferential sprung discs, either metallic or any other material. The retractable releasable fastening members are all intended to move inwardly on movement of the connector into the guide conduit and enable the pull-in device, cable and connector to slide together up the I-tube until the abutment face (34) engages with the confronting abutment surface (55) of the lower edge (55) of the I-tube, and then to be sufficiently strong to resist any downward force and avoid downward movement, hence holding the weight of the connector (3) and bend limiter (4) in place. Figure 10 shows another embodiment of connector in which in this case no sprung latching is used. In this embodiment, the connector again has a circumferential flange (54) and the I-tube also has an external flange (60). Here the cable pull-in is done under external supervision (diver or remotely operated vehicle (ROV) ) , and the sleeve assembly is pulled in until the abutment surface (34) on the flange of the connector engages, or nearly engages, with the abutment face (61) lower edge of the flange (60) of the I-tube, but the pull in tension is kept below the tension required to break the weak link shear pins. Again there is a quick-install push-fit action.

The diver or ROV then attaches a clamp (65) or similar mechanical bolting, between the underside of the flange (34) of the connector (3) and the I-tube flange (60) to pull the two together and then hold the weight of the engaging piece (3) and bend limiter sleeve (4) in place. The pull in operation then continues, breaking the weak link shear pins (37) and pulling the cable up through the top end of the I-tube as described above.

The abovedescribed embodiments allowing quick-connect and quick-install of cable are suitable to be employed to deploy other types of cable to other support structures in relatively shallow water, generally up to about 200 metres deep. It should finally be noted that the cable sleeves may be provided so that cable protection extends through the transition zone, onto the seabed and on through the whole likely scour zone, whereafter it may be buried, for example by ROV. This not only provides a structure routing the cable but also protects the cable in the scour zone from rock or gravel dropped around the support structure to protect it. In some circumstances the cable protection may be intended to extend past the likely scour zone to provide permanent or semi-permanent cable protection.

Finally the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Therefore, the presently discussed embodiments are considered to be illustrative and not restrictive, the scope of the invention being indicated by the following claims.

Claims

1. Apparatus for deploying an underwater cable between a support structure disposed in shallow water and the bed of the shallow water, comprising: a connector comprising a forward portion and a rearward portion, the forward portion including a device to fasten, via a push-fit action, to a guide on or adjacent the support structure, the connector having a through-passageway, a cable pull-in device for attachment to the cable, the pull- in device also being connected to the connector via a detachable link for pulling cable through the guide and the connector, and, connected to the rearward portion of the connector, a protective sleeve, also having a through-passageway, for receiving the cable, to provide a protective cable route between the connector and the bed of the shallow water.

2. Apparatus according to claim 1, wherein the detachable link comprises a frangible link which can be broken automatically while the cable is being pulled in.

3. Apparatus according to claim 1 or 2, wherein the protective sleeve comprises a series of interconnected successive sleeve shells .

4. Apparatus according to claim 3, wherein each interconnection of the sleeve shells comprises corrodible interconnecting members.

5. Apparatus according to any preceding claim, wherein the forward portion is at one end of the connector and the rearward portion is at the other end of the connector.

6. Apparatus according to any preceding claim, wherein the connector further includes an abutment surface between the connection to the guide on the forward portion and the connection to the sleeve on the rearward portion, for abutting the guide and for limiting forward movement of the connector through the guide, thereby locating the connector in the guide.

7. Apparatus according to any preceding claim, wherein the fastening device includes at least one releasable fastening member, which is releasable from a first position, in which the connector is movable through the guide, to a second position, in which the connector is fastened to the guide, so as to co-operate with the guide to hold the weight of the connector and the sleeve connected to the connector.

8. Apparatus according to any preceding claim for use in routing underwater cable to and/or from and/or between offshore/nearshore wind, wave or tidal turbines.

9. Apparatus according to any preceding claim, wherein the guide comprises a guide conduit disposed on or adjacent the support structure and having an upper exit and a lower exit.

10. Apparatus according to claim 9, wherein the protective sleeve extends from the lower exit of the guide conduit at least onto the bed of the body of water.

11. An assembly comprising apparatus according to any preceding claim, in which the connector is connected with a guide on or adjacent a support structure in shallow water and the protective sleeve and cable received therein are deployed between the guide and the bed of a body of shallow water.

12. A method of deploying a cable in a protected cable route between a support structure deployed in shallow water and the bed of the shallow water, comprising: pulling-in a detachable device attached to the cable, a connector, which is connected to the pull-in device and has a through-passageway, and a protective sleeve, which is attached to the connector and also has a through-passageway, until the connector fastens via a push-fit action to a guide on or adjacent the support structure, thereby also deploying the protective cable sleeve between the connector and the bed of the shallow water, thus providing a protected cable route between the connector and the bed of the shallow water.

13. A method according to claim 12, further comprising pulling in the connector until an abutment surface thereon abuts an abutment surface on the guide, thereby limiting onward movement of the connector .

14. A method according to claim 13, further comprising pulling in the connector until at least one releasable fastening member on the connector is released and acts on the connector so as to cooperate with the support structure to hold the weight of the connector and the sleeve and thereby fasten the connector and the sleeve to the connector.

15. A method according to any one of claims 11 to 14, further comprising pulling-in the cable further until the pull-in device is detached.

16. A method according to claim 15, further comprising pulling-in the cable further and allowing the cable to be pulled out of the guide and hung off at the support structure.

17. Δ method according to any one of claims 12 to 16, further comprising laying the cable and the protective sleeve so as to together lie on the bed of the shallow water.

18. Apparatus for deploying an underwater cable between a support structure disposed in shallow water and the bed of the shallow water, the support structure including a cable guide conduit having an upper exit and a lower exit, comprising: a connector to fasten, via a push-fit action, to the guide conduit, the connector having a through-passageway, a cable pull-in device for attachment to the cable and movable through the guide conduit, the deployment device being connected to the connector via a detachable link, and, a protective sleeve having a through-passageway for housing the cable to provide a protected cable route between the connector and the bed of the shallow water, the through-passageways being in communication so that the cable can be pulled by the deployment device through both the connector and the protective sleeve on detachment of the deployment device, both so as to deploy the cable to the support structure via the guide conduit and to the bed of the shallow water in the protected cable route.

19. Apparatus for deploying an underwater cable between a support means disposed in shallow water and the bed of the shallow water, comprising: connector means comprising a forward portion and a rearward portion, the forward portion including means to fasten, via a push-fit action, to guide means on or adjacent the support means, the connector means having a through-passageway, cable pull-in means for attachment to the cable, the pull-in means also being connected to the connector means via detachable link means for pulling cable through the guide means and the connector means, and, connected to the rearward portion of the connector means, protective sleeve means, also having a through-passageway, for receiving the cable, to provide a protective cable route between the connector means and the bed of the shallow water.

20. Apparatus according to claim 19, wherein the detachable link means comprises a frangible link which can be broken automatically while the cable is being pulled in.

21. Apparatus according to claim 19, wherein the protective sleeve means comprises a series of interconnected successive sleeve shells.

22. Apparatus according to claim 21, wherein each interconnection of the sleeve shells comprises corrodible interconnecting means.

23. Apparatus according to claim 19, wherein the forward portion is at one end of the connector means and the rearward portion is at the other end of the connector means.

24. Apparatus according to claim 19, wherein the connector means further includes means providing an abutment surface between the connection to the guide means on the forward portion and the connection to the sleeve means on the rearward portion, for abutting the guide means and for limiting forward movement of the connector means through the guide means, thereby locating the connector means in the guide means.

25. Apparatus according to claim 19, wherein the fastening means includes at least one releasable fastening means, which is releasable from a first position, in which the connector means is movable through the guide means, to a second position, in which the connector means is fastened to the guide means, so as to cooperate with the guide means to hold the weight of the connector means and the sleeve means connected to the connector means.

26. Apparatus according to claim 19, for routing underwater cable to and/or from and/or between offshore/nearshore wind, wave or tidal turbines.

27. An assembly comprising a support structure in shallow water, a cable guide conduit on or adjacent the support structure and having an upper exit and a lower exit; a connector including a through-aperture and fastened at one end to the lower exit of the guide conduit via a push-fit action; and a protective sleeve connected to the connector and having a through-aperture in communication with the through-aperture of the connector so as to provide a protective cable route between the connector and the bed of the shallow water.

28. An assembly according to claim 27, wherein the protective sleeve comprises a series of interconnected successive sleeve units, the sleeve extending from the lower exit of the guide conduit at least onto the bed of the body of water.