SE2450114A1 - A cable laying vessel - Google Patents

Abstract

A cable laying vessel (10) for installing of a submarine power cable (16) from a work deck (14) of the vessel (10), the cable laying vessel (14) comprising cable storage structure (22) for storing of cable lengths on the vessel (10);a chute (28) for guiding the cable (16), the chute (28) being vertically elevated from a horizontal plane defined by the work deck (14), the chute (28) comprising a vertically oriented chute exit mouth (30); a cable path (18) formed between the cable storage structure (22) and the chute exit mouth; a plurality of cable tensioners (24) arranged along the cable path (18), downstream of the cable storage structure (22), for applying radial force to the cable (16), and an underbender arrangement (26) arranged downstream of all the cable tensioners (24) arranged along the cable path (18), and forward of the chute (28), the underbender arrangement (26) being movable between a first position and a second position. Wherein, in the first position, the underbender arrangement (26) is aligned with the cable path (18), and wherein, in the second position, the underbender arrangement (26) is moved away from the cable path (18).

Description

A CABLE LAYING VESSEL Technical field The present disclosure relates to a cable laying vessel. ln particular, the disclosure relates to a cable laying vessel for installing of submarine power cables from a deck of the vessel.

Background Dynamic submarine power cables are often connected to floating offshore structures, such as floating wind turbines, whereby they are subjected to constant movement. By using ancillaries, such buoyancy members and clamps, the cable can be provided with a configuration which allows it to better adapt to these movements.

For allowing the ancillaries to be attached to the cable from the cable laying vessel, an elevated chute may be used which allows the cable to extend in a vertical configuration above the work deck, whereby the ancillaries can be attached to the cable from the vessel at this vertical section.

To hold the weight of the cable, tensioners are conventionally arranged at the slope leading up to the elevated chute.

When jointing of the cable is required, the cable is released from the tensioners and lifted down onto a work deck of the vessel where jointing is performed.

However, it has been realized that the lifting of the cable onto and from the work deck may be both complicated and time consuming. Specifically, in previously known vessels, the workability may be low during heavy weather. There is thus need for an improved cable laying vessel which allows jointing to be performed more efficiently.

Summary ln view of the above, an object of the present disclosure is to provide an improved cable laying vessel for submarine power cables. The cable laying vessel of the present disclosure may be particularly useful for installing submarine power cables with ancillaries, such as dynamic power cables.

According to a first aspect of the present disclosure, a cable laying vessel for installing of a submarine power cable from a work deck of the vessel is disclosed, the cable laying vessel comprising a cable storage structure for storing of cable lengths on the vessel; a chute for guiding the submarine power cable, the chute being vertically elevated from a horizontal plane defined by the work deck, the chute comprising a vertically oriented chute exit mouth; a cable path formed between the cable storage structure and the chute exit mouth; a plurality of cable tensioners arranged along the cable path, downstream of the cable storage structure, for applying radial force to the submarine power cable and; an underbender arrangement arranged downstream of all the cable tensioners arranged along the cable path, and forward of the chute, the underbender arrangement being movable between a first position and a second position. ln the first position, the underbender arrangement is aligned with the cable path, and wherein, in the second position, the underbender arrangement is moved away from the cable path.

By arranging the tensioners closer to the bow of the vessel, and instead providing an underbender arrangement along a ramp leading up to the chute in the aft direction, for load support and guiding of the cable, several benefits may be provided. Firstly, by providing the tensioners separate from the chute, the same tensioners may be used also for laying operations where the elevated chute is not used, such as for laying cables without ancillaries. Furthermore, as the underbender arrangement is adapted to be operated between the first position, being a closed position, and a second position, being an open position, the cable can be lifted from its position under the movable underbender arrangement as the underbender is in the open position. Thereby the jointing process may be performed in-line, without lifting the cable onto the work deck, thus achieving a more efficient jointing process.

According one embodiment, the underbender arrangement comprises at least one roller.

The roller is arranged to contact the cable from above during cable laying, such that the transition of the cable to the chute may be performed smoothly and with low risk of damaging the cable. The underbender arrangement may comprise a plurality of rollers, such as 30 rollers or more.

According to one embodiment, the underbender arrangement may comprise several groups of rollers, the groups of rollers being movable independently from each other between the first position and the second position.

According one embodiment, the underbender arrangement is hydraulically controllable between the first position and the second position.

Hereby, a robust system for controlling the underbender arrangement may be provided. ln alternative embodiments, the underbender arrangement may be pneumatically, electrically, or mechanically controlled.

According one embodiment, the chute has a curved shape.

Hereby, the cable is guided from a substantially horizontal orientation at the top of the chute, to a vertical orientation at the chute exit mouth, while the bending radius of the cable may be limited by the curve of the chute, thus preventing damage of the cable.

According one embodiment, in the first position of the underbender arrangement, the cable is allowed to be guided along the underbender arrangement.

Hereby, the underbender arrangement contacts and supports the cable during laying, thus allowing for the tensioners to be arranged further away from the point where the cable enters the water.

According one embodiment, the cable laying vessel further comprises a jointing habitat, the jointing habitat being arranged between the cable tensioners and the underbender arrangement along the cable path.

The jointing habitat allows the cable to be protected during the jointing. The jointing habitat further allows for the jointing of the submarine power cable to be performed under controlled conditions to ensure the quality of the joint. For example, the jointing habitat may be provided with electric power supply, air Conditioner and dehumidifier.

The jointing habitat may be vertically elevated from a horizontal plane defined by the work deck, such that the cable is allowed to be lifted into the jointing habitat. ln one embodiment, the jointing habitat is removably arranged on the work deck such that it may be removed from the vessel. Thereby, a modular cable laying vessel may be provided.

The size of the joint habitat should at least be sufficient for allowing the jointing to be performed, such as 4><17 m.

According one embodiment, the jointing habitat comprises a floor having an elongated opening extending in a direction of the cable path, such that a section of the submarine power cable is allowed to be lifted into the jointing habitat.

Hereby, the cable may be allowed to be lifted straight up into the jointing habitat, thus providing for in-line jointing while minimizing the distance that the cable must be moved for the jointing.

According one embodiment, in the second position of the underbender arrangement, the cable is allowed to be lifted into the jointing habitat.

According one embodiment, the cable laying vessel further comprises a worktable arranged in the plane formed by the work deck, the worktable comprising a worktable opening being vertically aligned with the chute exit mouth.

Hereby, ancillaries such as buoyancy members and clamps may be attached to the cable below the chute, and vertically aligned with the position where the cable enters the water.

According to one embodiments, the worktable may be horizontally openable such that the ancillaries are allowed to pass once they have been attached to the cable above the worktable. A locking mechanism may be used to lock the worktable in the open or closed position.

Furthermore, the worktable may be tiltable around a horizontal axis, such that it can be stoved away when no work is performed from it. Thereby, the worktable may be protected during transit of the vessel.

Brief Description of the Drawinqs These and other aspects of the present inventive concept will now be described in more detail, with reference to the appended drawings showing an example embodiment of the inventive concept, wherein: Fig. 1 schematically i||ustrates a side view of a rear portion of a cable laying vessel according to an embodiment.

Fig. 2 schematically i||ustrates a perspective view of a part of the cable laying vessel of Fig. 1.

Fig. 3 shows a first position of an underbender arrangement of a cable laying vessel according to an embodiment.

Fig. 4 shows the underbender arrangement of Fig. 3 in a second position.

Detailed Description of Example Embodiments ln the present detailed description, various embodiments of the invention are described.

Fig. 1 schematically i||ustrates a side view of cable laying vessel 10 according to an embodiment of the present disclosure. The cable laying vessel 10 comprises a hull 12 and a work deck 14, the work deck 14 extending atop of the hull 12. The surface of the work deck 14 defines a horizontal plane P.

A submarine power cable 16 extends along a cable path 18. The cable path 18 is defined as the path which the cable 16 follows during installation of, and operation on, the cable 16 during the cable installation. The cable path 18 is thus not fixed, but may be displaced in e.g. a direction perpendicular to the extension of the horizontal plane, that is, in a generally vertical direction, such as when jointing is to be performed on the cable 16.

The cable path 18 starts at a cable storage structure 22. The cable storage structure 22 is adapted to store cable lengths. The cable storage structure may further be adapted to feed out the cable 16, such as by a turntable. The cable storage structure 22 may be arranged on top of the work deck 14 and/or below the work deck 14.

The cable 16 supplied from the cable storage structure 22 is guided along the cable path 18 to a plurality of cable tensioners 24, an underbender arrangement 26 and a chute 28 that is vertically elevate relative to the work deck 14, comprising an exit mouth 30. The cable path 18 thus extends from the cable storage structure 22 to the exit mouth 30. The cable tensioners 24, the underbender arrangement 26 and the chute 28 are sequentially arranged along the cable path 16 from the cable storage structure 22 to the exit mouth 30.

The cable tensioners 24 are arranged on the work deck 14 and provide a pressure on the cable 16 from at least two, such as at least four, directions. The cable tensioners 24 are arranged to provide a radial force and a hold back force to the cable 16. The applied pressure should be high enough to hold the load of the cable 10 as it hangs vertically from the chute 28 and extends down to the seabed. ln one example, the cable tensioners 24 may be adapted to hold a weight of 35 tonnes, such as 45 tonnes or more.

The cable tensioners 24 may comprise one or more pairs of tracks for applying pressure to the cable 16. For example, eight pairs of tracks may be disposed along the cable path 18. The position of the tracks may be adjusted, for example hydraulically or electrically, to provide a controlled pressure for gripping the cable 16. The tracks may further be rotatably controlled to allow for feeding of the cable 16 along the cable path 18. ln other embodiments the cable tensioners 24 may comprise wheels instead of the tracks.

The underbender arrangement 26 is arranged downstream of the cable tensioners 24 and upstream of the vertically elevated chute 28 along the cable path 18. The cable path 18 between the cable tensioners 24 and the underbender arrangement 26 is essentially parallel to the horizontal plane P defined by the work deck 14. The cable path 18 between the underbender arrangement 26 and the chute 28 is sloping upwards. The underbender arrangement 26 is thus arranged to support the cable 16 at the transition between a horizontal section and the sloping section of the cable path 18. The underbender arrangement 26 has a curved shape for limiting the bending radius of the cable 16 during the transition.

The underbender arrangement 26 is movable between a first position and a second position. ln the first position, the underbender arrangement 26 is aligned with the cable path 18. A cable 16 arranged along the cable path 18 may thus be guided along the underbender arrangement 26 in the first position. ln the second position of the underbender arrangement 26, the underbender arrangement 26 is moved away from the cable path 18. When the underbender arrangement 26 is moved away from the cable path 18 it is no longer able to contact the cable 16 from above. ln the second position of the underbender arrangement, the cable 16 is thus allowed to be lifted to a position above the underbender arrangement 26 whereby jointing may be performed.

Ajointing habitat 34 is further arranged along the cable path 18. The jointing habitat is vertically elevated from the horizontal plane P defined by the work deck 14. The jointing habitat 34 is aligned with the cable path 18, such that the cable 16 is allowed to be lifted straight up into the jointing habitat 34.

Fig. 2 is a perspective view showing some parts of the cable laying vessel 10. Here, the jointing habitat 34 is arranged just upstream of the underbender arrangement 26 along the cable path 18. The jointing habitat 34 has the shape of a container. The floor of the jointing habitat 34 has an elongated opening 36 extending in a direction of the cable path 18, from one end to an opposite end of the jointing habitat 34. Each of the two side walls of the jointing habitat 34 being arranged along the cable path 18 also comprises openings being connected with the floor opening 36. Thereby, the cable 16 is allowed to be lifted straight up into the jointing habitat 34. The jointing can thus be performed in line, and there is no need to transfer the cable 16 onto the work deck 14. During the jointing operation, the openings of the jointing habitat may be closed and/or sealed to create a protected space within the jointing habitat 34 for the jointing.

Fig. 2 further shows a worktable 38 arranged below, and vertically aligned with, the exit mouth 30 of the chute 28. The worktable 38 allows for ancillaries, such as buoyancy members and clamps, to be installed on the cable 26. The installation is thus allowed to be performed at a position from which the ancillaries can be readily lowered into the water after installation.

The worktable 38 comprises a worktable opening 40 through which the cable 16 and the ancillaries are allowed to pass. The worktable 38 may be divided into first and second worktable parts 38a, 38b disposed on respective sides of the worktable opening 40. The worktable parts 38a, 38b are displaceable from and towards each other in a direction parallel to the horizontal plane P, such that the size of the worktable opening 40 may be varied. Thus, the worktable parts 38a, 38b may be arranged closer to each other during installation of the ancillaries on the cable 16 and displaced further away from each other when lowering the ancillaries into the water.

Fig. 3 shows the underbender arrangement 26 in its first position. The underbender arrangement comprises a plurality of rollers 32. The rollers 32 are arranged in the cable path 18, above the cable 16, such that the cable 16 is contacted by the rollers 32.

Fig. 4 shows the underbender arrangement 26 in its second position with the rollers 32 moved to one or two sides of the cable path 18. ln the shown embodiment, the underbender arrangement 26 comprises two sets of rollers 32, the two sets of rollers 32 being tilted in opposite directions when the underbender arrangement 26 is in its second position. The cable 16 is thus allowed to be lifted past the underbender arrangement 26 to allow for jointing of the cable 16 without needing to transport it onto the work deck 14. lt should be understood that the underbender arrangement 26 could also include only one set of rollers 32, or several sets of rollers 32 being tiltable in the same direction. ln Fig. 4 the jointing has already been performed, and the joint portion of the cable 16 is about to be lifted over the chute 28.

During use of the cable laying vessel 10, to lay a cable 16, the underbender arrangement 26 may be operated as follows. When no jointing is performed, the underbender arrangement 26 is in its first position, and the cable 16 runs along the cable path 18 below the underbender arrangement 26, that is, vertically between the underbender arrangement 26 and the work deck 14. When jointing is to be performed, the underbender arrangement 26 is moved to its second position. The movement to the second position may include tilting of the underbender arrangement 26, or a part of the underbender arrangement 26, around an axis of the underbender arrangement 26, the axis being parallel to the cable path 16. The tilting may be performed by a hydraulic actuator. Alternatively, the tilting may be performed by a lifting device, such as a crane. By tilting the underbender arrangement 26 around the axis such that the underbender arrangement 26 is no longer aligned with the cable path 18, the cable 16 is allowed to be lifted to a position above the underbender arrangement 26 using a lifting device. The lifting device may be a crane arranged on the work deck 14. Alternatively, the cable may be lifted using mechanical and/or electric lifting devices via static lifting points arranged in the ceiling of the jointing habitat 34. The cable 16 may thus be lifted to a position at which jointing is allowed to be performed on the cable 16, such as into the elevated jointing habitat 34. Once the cable 16 has been jointed, the lifting device again lifts the cable 16, to transfer the jointed cable section over the chute 28. Thereafter, the cable 16 is again moved to a position under the underbender arrangement 26, whereby the underbender arrangement 26 is moved back to its first position, such that the cable laying may continue.

Even though the solution has been described with reference to specific exemplifying embodiments thereof, many different alterations, modifications and the like will become apparent for those skilled in the art.

Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. ln the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims (1)

1.A cable laying vessel (10) for installing of a submarine power cable (16) from a work deck (14) of the vessel (1 O), the cable laying vessel (14) comprising: a cable storage structure (22) for storing of cable lengths on the vessel (10), a chute (28) for guiding the submarine power cable (16), the chute (28) being vertically elevated from a horizontal plane defined by the work deck (14), the chute (28) comprising a vertically oriented chute exit mouth (30), a cable path (18) formed between the cable storage structure (22) and the chute exit mouth, a plurality of cable tensioners (24) arranged along the cable path (18), downstream of the cable storage structure (22), for applying radial force to the submarine power cable (16), an underbender arrangement (26) arranged downstream of all the cable tensioners (24) arranged along the cable path (18), and forward of the chute (28), the underbender arrangement (26) being movable between a first position and a second position, wherein, in the first position, the underbender arrangement (26) is aligned with the cable path (18), and wherein, in the second position, the underbender arrangement (26) is moved away from the cable path (18). _ The cable laying vessel (10) according to claim 1, wherein the underbender arrangement (26) comprises at least one roller (32).The cable laying vessel (10) according to any one of claims 1-2, wherein the underbender arrangement (26) is hydraulically controllable between the first position and the second position. _ The cable laying vessel according to any one of claims 1-3, wherein the chute (28) has a curved shape. _ The cable laying vessel (10) according to any one of claims 1-4, wherein the underbender arrangement (26) has a curved shape. _ The cable laying vessel (10) according to any one of claims 1-wherein, in the first position of the underbender arrangement (26), the submarine power cable (16) is allowed to be guided along the underbender arrangement (26). _ The cable laying vessel (10) according to any one of claims 1-6 further comprising a jointing habitat (34), thejointing habitat (34) being arranged between the cable tensioners (24) and the underbender arrangement (26) along the cable path (18). _ The cable laying vessel (10) according to claim 7, wherein the jointing habitat (34) comprises a floor having an elongated opening (36) extending in a direction of the cable path (18), such that a section of the submarine power cable (16) is allowed to be lifted into the jointing habitat (34). _ The cable laying vessel (10) according to any one of claims 7-wherein, in the second position of the underbender (26), the submarine power cable (16) is allowed to be lifted into the jointing habitat (34). 10. The cable laying vessel (10) according to claim 9 further comprising a worktable (38) arranged in the plane (P) formed by the work deck (14), the worktable (38) comprising a worktable opening (40) being vertically aligned with the chute exit mouth (30).