A method for simultaneously laying multiple elongated, flexible members on the seabed.

Abstract

This invention provides a method for simultaneously laying three or more elongated, flexible members on the seabed from a ship. [Solution] The method includes a) advancing all individual elongated flexible members to a first position where a group of elongated flexible members is formed; b) advancing the group of elongated flexible members to a second position and twisting the group of elongated flexible members in a first direction to obtain a section of elongated flexible members twisted in the first direction; c) binding a portion of the section of elongated flexible members twisted in the first direction at the second position; d) advancing the group of elongated flexible members from the first position to the second position and twisting them in a second direction opposite to the first direction to obtain a section of elongated flexible members twisted in a second direction following the section of elongated members twisted in the first direction; and e) binding a portion of the section of elongated flexible members twisted in the second direction at the second position, and repeating steps a) to e) until the entire length of the elongated flexible members is laid on the seabed in an alternating twisted configuration.

Description

[Technical Field]

[0001] This disclosure generally relates to laying elongated, flexible members such as power cables on the seabed from a ship. [Background technology]

[0002] Submarine cables are laid from vessels such as cable-laying ships or barges. In most cases, submarine cables are fed from a drum or turntable down to the seabed via a curved chute or laying wheel positioned on the vessel. Therefore, the submarine cable is bent as it enters the chute. When it lands on the seabed, it is bent in roughly the opposite direction to its direction on the chute or laying wheel.

[0003] In recent years, power cable systems have begun to be designed to include three direct current (DC) submarine power cables connecting two points in a power generation system: one for the positive terminal, one for the negative terminal, and one for redundancy. Such cable systems may also include submarine fiber optic cables extending outward along the longitudinal direction of the submarine power cables. This introduces new installation complexity compared to cable systems with two high-voltage direct current (HVDC) cables and one fiber optic cable, especially considering the advantages of installing all submarine cables connecting the two points simultaneously, as this saves installation time and reduces the risk and associated costs of changing weather conditions at sea. Another advantage is that it requires only one trench or burial campaign instead of two separate trenches, resulting in less disturbance to the seabed, which means a smaller environmental impact and reduced impact on benthic organisms. [Overview of the Initiative]

[0004] The common simultaneous installation of multiple cables can be achieved by bundling all submarine cables together and lowering them into the water. Lowering cables is problematic when they are arranged in a flat configuration, i.e., side by side in a single plane, because maintaining catenary stability is difficult. Cables with lower specific gravity tend to move out of alignment with other cables, posing a risk of damaging fiber optic cables. In a trefoil configuration, where one power cable is above another, the bundle is bent on the chute and at the landing point. This results in a mismatch in the lengths of the power cables. The inner power cables are compressed and the outer power cables are stretched by the curve formed by the bundle. In a tightly bundled bundle, this can result in significant compressive and tensile forces on individual cables within the bundle, potentially increasing the complexity of the installation process.

[0005] With the foregoing in mind, the object of this disclosure is to provide a method for simultaneously laying three or more elongated flexible members on the seabed from a ship, which solves or at least mitigates the problems of the prior art.

[0006] Therefore, a method for simultaneously laying three or more elongated flexible members on the seabed from a ship, comprising: a) advancing all individual elongated flexible members to a first position where they are gathered to form a group of elongated flexible members; b) advancing the group of elongated flexible members from the first position to a second position at a first distance from the first position, and twisting the group of elongated flexible members at least once in a first direction between the first and second positions to obtain a section of elongated flexible members twisted in the first direction; and c) at the second position, the elongated flexible section twisted in the first direction A method is provided which includes d) tying together at least a portion of the group of members, and e) advancing the group of elongated flexible members from a first position to a second position, and twisting them at least twice in a second direction opposite to the first direction between the first and second positions to obtain a group of elongated flexible members twisted in a second direction following a group of elongated members twisted in the first direction, and e) tying together at least a portion of the group of elongated flexible members twisted in the second direction at the second position, and repeating steps a) to e) until the entire length of the elongated flexible members is laid on the seabed in an alternating twisted configuration.

[0007] This method allows for the deployment of multiple elongated flexible members from a deployment vessel to the seabed in a stable "bundle" configuration, enabling burial / post-burial protection without the complexity of trench excavation / burial tools. The alternating SZ or ZS twisting of the group of elongated flexible members can restrict the relative axial movement between individual elongated flexible members.

[0008] For example, one of the elongated flexible members may have a lower specific gravity than the other elongated flexible members.

[0009] According to one embodiment, in steps b) and d), the group of elongated flexible members is advanced in the direction toward the stern of the vessel on which it is installed.

[0010] According to one embodiment, the first distance is equal to or greater than the catenary length of one of the groups of elongated flexible members extending from the installation vessel toward the seabed. The catenary length is the length of the catenary line that the group of elongated flexible members follows from the exit point of the installation vessel toward the landing point on the seabed. Thus, in this example, the length of each section of elongated member group twisted in the first / second direction is equal to or greater than the catenary length, and each of them is made integral by being bound at its endpoints in steps c) and e).

[0011] If the first distance is equal to or greater than the catenary length, the bundling of the elongated flexible members may be performed along a limited length, for example, less than half of the first length, along a section of elongated flexible members twisted in the first / second direction. For example, if the laying depth is 30 m and the catenary length is 45-50 m, the bundling may be performed over a distance of 2-5 m, or less than 10 m along a section of elongated flexible members twisted in the first / second direction. If the first distance is shorter than the catenary length, continuous bundling may be preferred to obtain a stable bundle of elongated flexible members.

[0012] According to one embodiment, the installation vessel includes N spaced-apart rotating device stations arranged on the deck, the first of which is located in a first position, and the other N-1 rotating device stations are located between the first and second positions, and a group of elongated flexible members is advanced through the rotating device stations, and the group of elongated flexible members is twisted 1 / N times at each rotating device station.

[0013] According to one embodiment, N=3.

[0014] Alternatively, N may be greater than 3, depending on how much twisting should occur at each rotating device station.

[0015] N rotating device stations are distributed sequentially on the deck, and the distance between each pair of adjacent rotating device stations may be equal.

[0016] According to one example, the N rotating device stations may be movable on a track or the like so as to assist in rotating the group of elongated flexible members by moving together with the group of elongated flexible members.

[0017] According to one embodiment, the installation vessel comprises a laying tensioner that advances individual elongated flexible members toward the first position.

[0018] According to one embodiment, each laying tensioner advances a respective one of the individual elongated flexible members toward the first position.

[0019] According to one embodiment, a first one and a second one of the elongated flexible members are DC cables, and a third one of the elongated flexible members is a metallic return cable. The metallic return cable may have a lower specific gravity than that of the first and second elongated flexible members.

[0020] According to one embodiment, the installation vessel is a cable-laying vessel.

[0021] According to one embodiment, step a) comprises advancing an optical fiber cable having an outer diameter smaller than that of the elongated flexible member to a first position where it is grouped together with the elongated flexible member, and the optical fiber cable grouped together with the elongated flexible member is subjected to steps a) to e) and repetitions thereof.

[0022] According to one example, step a) comprises advancing an optical fiber cable having an outer diameter smaller than that of the elongated flexible member to any of the N rotating device stations subsequent to the first position, for example the second, third, or N-th rotating device station, prior to the second position, where it is grouped together with the group of elongated flexible members. Therefore, the optical fiber cable is grouped together with the group of elongated flexible members at a point later than the first rotating device station. Accordingly, the optical fiber cable is not twisted as much as the group of elongated flexible members.

[0023] According to one embodiment, there are three elongated flexible members, and in step a), the three individual elongated flexible members are grouped together in a trefoil configuration.

[0024] In general, all terms used in the claims shall be interpreted in accordance with their ordinary meaning in the relevant art, unless explicitly defined otherwise herein. All references to "a / an / the element, apparatus, component, means" or the like shall be interpreted openly as referring to at least one instance of the element, apparatus, component, means or the like, unless explicitly stated otherwise.

[0025] Next, specific embodiments of the inventive concept will be described by way of example with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] [Figure 1] It is a plan view of an example of a stern deck of an installation vessel. [Figure 2] It is a plan view of the stern deck having an elongated flexible member extending along the stern deck. [Figure 3A] It is a diagram showing cross-sections at different positions along the longitudinal direction of an elongated flexible member extending on the stern deck. [Figure 3B] It is a diagram showing cross-sections at different positions along the longitudinal direction of an elongated flexible member extending on the stern deck. [Figure 3C] It is a diagram showing cross-sections at different positions along the longitudinal direction of an elongated flexible member extending on the stern deck. [Figure 3D] It is a diagram showing cross-sections at different positions along the longitudinal direction of an elongated flexible member extending on the stern deck. [Figure 3E] It is a diagram showing cross-sections at different positions along the longitudinal direction of an elongated flexible member extending on the stern deck. [Figure 3F] It is a diagram showing cross-sections at different positions along the longitudinal direction of an elongated flexible member extending on the stern deck. [Figure 4] This diagram schematically shows an example of a rotating device station S on the aft deck. [Figure 5] This is a flowchart illustrating a method for simultaneously laying three or more elongated, flexible members on the seabed from a mounting vessel. [Modes for carrying out the invention]

[0027] Next, the concept of the present invention will be fully described below with reference to the accompanying drawings illustrating exemplary embodiments. However, the concept of the present invention can be embodied in many different forms and should not be construed as being limited to the embodiments described herein. Rather, these embodiments are provided as examples to make this disclosure sufficient and complete and to fully convey the scope of the concept of the present invention to those skilled in the art. Throughout this description, the same reference numerals refer to the same elements.

[0028] Figure 1 is a plan view of the aft deck 3 of the installed vessel 1.

[0029] The installation vessel 1 may be, for example, a cable-laying vessel or a cable-laying barge.

[0030] The installation vessel 1 has a chute or laying wheel 7. The chute or laying wheel 7 may be located at the stern 5 of the installation vessel 1.

[0031] The installation vessel 1 is configured to simultaneously lay three or more elongated flexible members on the seabed via a chute or laying wheel 7. The elongated flexible elements may be power cables, flexible pipelines, flexible umbilicals, or communication cables.

[0032] In the case of a power cable, the first and second elongated flexible members may be DC cables such as HVDC cables, and the third of the three elongated flexible members may be a metal return cable.

[0033] In the example described herein, three elongated flexible members are laid simultaneously on the seabed from the installation vessel 1. Furthermore, fiber optic cables may be laid on the seabed together with the elongated flexible members.

[0034] The installation vessel 1 may be equipped with a plurality of track tensioners or tensioning devices, T1 to T3. The track tensioners T1 to T3 may be located on the aft deck 3. Each track tensioner T1 to T3 may be, for example, a track tensioner or a capstan wheel.

[0035] In this example, there are three laying tensioners T1-T3, i.e., one for each elongated flexible member. In other examples, fewer laying tensioners may be needed to advance three elongated flexible members, or more than three laying tensioners may be needed if more than three elongated flexible members are to be installed simultaneously. For example, in some examples, two elongated flexible members may be arranged in a piggyback configuration and advanced along the rear deck by a single laying tensioner T1, T2, or T3, such as a twin cable / product tensioning device. In this case, fewer laying tensioners are needed than the number of elongated flexible members to be installed simultaneously.

[0036] The installed vessel 1 further comprises multiple rotating device stations S1~S N It may also be equipped with the following. Rotating device stations S1 to SN are located on the aft deck 3.

[0037] Rotating device station S1~S N These are arranged sequentially in the direction toward the stern 5, i.e., towards the stern, relative to the laid tensioners T1 to T3. Rotating device stations S1 to S N These are sequentially positioned between the laying tensioners T1 to T3 and the chute or laying wheel 7 of the installation vessel 1.

[0038] The rotating device stations S1 to SN may be arranged in a line relative to each other.

[0039] Rotating device stations S1 to SN may be arranged in a line with the chute or laying wheel 7.

[0040] The rotating device stations S1 to SN may be positioned to move in conjunction with the chute or laying wheel 7 during installation.

[0041] The rotating device stations S1 to SN and the chute or laying wheel 7 may be aligned with each other, that is, they may be arranged sequentially in a straight line toward the stern 5.

[0042] According to this example, the rotating device stations S1~S N The number N is 3, but more generally, N can be equal to or greater than 3.

[0043] In one example, when the number of elongated flexible members is 3, N=3. In some examples, N = the number of elongated flexible members laid simultaneously as a group from the installation vessel 1. Rotating device stations S1~S N The number N generally depends on the amount of twisting that must be done at each station to cause the group of elongated flexible members to rotate at least once completely before being laid from the installation vessel 1. This may depend on the available space on the installation vessel 1, the design of the elongated flexible members, and the available equipment on the installation vessel 1.

[0044] The first rotating device station S1 is located in the first position on the aft deck 3. The first rotating device station S1 is located in the first position on the aft deck 3. N Of these, it is located closest to the installation tensioners T1 to T3.

[0045] Adjacent rotating device stations S1~S NThe distance between any arbitrary pair may be equal. Therefore, for example, the distance between the first rotating device station S1 and the second rotating device station S2 closest to the laying tensioners T1~T3 may be D, and the distance between the second rotating device station S2 and the third rotating device station S N may also be D. In general, the distance between any pair of adjacent rotating device stations Sn and Sn+1 may be D.

[0046] The installation vessel 1 comprises a machine M arranged on an aft deck 3. The machine M may be a wrapping machine, a strapping machine or a bunching machine.

[0047] The second position may be arranged at a first distance L from the first position. According to one example, the first distance L may be equal, approximately equal, or greater than the catenary length of one group of elongated flexible members extending from the installation vessel 1 toward the seabed during installation. Here, "approximately equal" means a range of 90 to 110% of the catenary length.

[0048] The machine M may be arranged in a line with rotating device stations S1~S N . The machine M may be arranged between the stern 5 and the N-th rotating device station S closest to the chute or laying wheel 7 N . Rotating device stations S1~S N , the machine M, and the chute or laying wheel 7 form a row for laying elongated flexible members on the seabed.

[0049] The installation vessel 1 may comprise one or more storage units such as cable drums, turntables, or cable carousels for storing elongated flexible members to be laid on the seabed. The elongated flexible members are fed from one or more storage units to rotating device stations S1~S N by the laying tensioners T1~T3, as will be described in more detail below.

[0050] Referring to Figures 2 to 5, the following will be explained: a method for simultaneously laying three or more elongated flexible members A, B, and C on the seabed from the installation vessel 1.

[0051] In step a), all individual elongated flexible members A to C are advanced to a first position where they are gathered together to form a group of elongated flexible members A to C.

[0052] The elongated flexible members A to C may be advanced by the laying tensioners T1 to T3. For example, each elongated flexible member A to C may be advanced to a first position by the corresponding laying tensioners T1 to T3.

[0053] The group of elongated flexible members may initially be arranged in a flat configuration before reaching the first rotating device station S1, as shown in Figure 3A at position P1. The group of elongated flexible members may also be laid in a trefoil configuration before reaching the first rotating device station S1. This may be done, for example, by guiding one of the elongated flexible members A-C, which are in a flat configuration, onto the other two elongated flexible members A-C so that it is lifted above the two elongated flexible members A-C, or it may be naturally provided by positioning a laying tensioner. For example, one laying tensioner may be positioned higher than the others to raise elongated flexible member A-C above the other elongated flexible members A-C.

[0054] In step b), the group 15 of elongated flexible members A to C is advanced from the first position to the second position. At the same time, the group 15 of elongated flexible members is twisted at least once in the first direction between the first position and the second position to obtain a section 21 of elongated flexible members twisted in the first direction.

[0055] The twisting is done at the rotating device station S1~S N This may be done by each rotating device station S1~S NThis partially twists the group 15 of elongated flexible members A to C, thereby causing the group 15 of elongated flexible members A to C to rotate completely at least once between the first position and the second position, that is, between the first rotating device station S1 and the machine M.

[0056] In the example shown in Figures 2-3E, the group 15 of elongated flexible members A-C is located at the rotating device stations S1-S N It is advanced through each rotating device station S1~S N It is twisted by 1 / 3 of a turn, or 120 degrees.

[0057] As shown in Figure 4, in one exemplary implementation, each rotating device station S1~S N The stand or platform 16 mounted on the rear deck 3 and the group 15 of elongated flexible members A to C are connected to the rotating device stations S1 to S N It may be equipped with a roller or roller group 17 that facilitates forward movement beyond the threshold. The roller 17 may be a single roller, or the roller group may include twin rollers, or multiple / three or more rollers in a horizontal or inclined configuration. The roller or roller group 17 may be active or passive. Furthermore, each rotating device station S1~S N The rotating device station S1-S may include one or more actuators 19 configured to operate elongated flexible members A-C. One or more actuators 19 may be hydraulic, mechanical, and / or electric. One or more actuators 19 change the position of elongated flexible members A-C on, for example, rollers or roller groups 17 to control the rotating device station S1-S NThe above configuration is used to obtain partial twisting of the group 15 of elongated flexible members A to C. In the example of Figure 4, the left actuator 19 can be raised or lowered and has a repositionable manipulator 19a to engage with the leftmost elongated flexible member B. Similarly, the right actuator 19 can be raised or lowered and has a repositionable manipulator 19b to engage with the rightmost elongated flexible member C. Thus, the configuration of the three elongated flexible members A to C can be changed. In the example of Figure 4, the group of elongated flexible members A to C may be reconfigured from the trefoil configuration shown in Figure 3B at position P2 in Figure 2, before the first rotating device station S1, to the trefoil configuration shown in Figure 3C at position P3, after the first rotating device station S1.

[0058] In each of the remaining rotating device stations S2 to SN, the actuators and manipulators change the position of group 15 of the elongated flexible members A to C as group 15 is advanced through these rotating device stations S2 to SN, as shown in positions P4 to P5 in Figure 2 and in Figures 3D to 3E respectively, thereby giving group 15 of the elongated flexible elements A to C a partial twist.

[0059] When the group 15 of elongated flexible members A to C reaches the machine M, that is, when the group 15 has been advanced by a first distance L from the first position to the second position, the group 15 of elongated flexible members A to C has, as an example, been rotated completely once or completely two or more times.

[0060] In step c), at the second position P6 shown in Figures 2 and 3F, at least a portion of the elongated flexible member group section 21 twisted in the first direction is bound together. Machine M binds, bundles, wraps, or straps at least a portion of the elongated flexible member group section 21 twisted in the first direction in order to maintain the integrity of the group 15. The binding may be done with thread, for example, silo wrap / high-strength cling film, elastic strapping band, or polymer yarn.

[0061] The binding may be performed continuously along the entire length of the elongated flexible member group section 21 twisted in the first direction, or it may be performed only along a limited distance along the elongated flexible member group section 21 twisted in the first direction. Figure 2 shows an example in which the binding 25 is performed continuously.

[0062] In step d), the group 15 of elongated flexible members A to C is advanced from the first position to the second position, twisting the group 15 of elongated flexible members A to C at least two times in the second direction opposite to the first direction between the first and second positions. The first rotation rotates the group 15 of elongated flexible members back to its natural or original zero position, and the second rotation twists it one more turn beyond the original zero position. Thus, a section of elongated flexible members twisted in the second direction is obtained, following the section of elongated flexible members twisted in the first direction 21. As a result, the leading edge of the section of elongated flexible members twisted in the second direction 23 reaches the second position and the machine M at approximately the same time that the trailing edge of the section of elongated flexible members twisted in the first direction 21 is moving away from the chute or laying wheel 7.

[0063] In step e), at least a portion of the elongated flexible member group section 23 twisted in the second direction is bound at the second position. Machine M binds, wraps, or straps at least a portion of the elongated flexible member group section 23 twisted in the second direction in order to maintain the integrity of the group 15.

[0064] The binding may be performed continuously along the entire length of the elongated flexible member group section 23 twisted in the second direction, or it may be performed only along a limited distance along the elongated flexible member group section 23 twisted in the second direction.

[0065] Steps a) to e) are repeated until the entire length of the elongated flexible member is laid on the seabed in a twisted form, i.e., in an alternating SZ or ZS form.

[0066] In one example, step a) includes advancing an optical fiber cable having an outer diameter smaller than that of the elongated flexible members A to C to a first position where it is grouped together with the elongated flexible members A to C. Subsequently, the optical fiber cable grouped together with the elongated flexible members is subjected to steps a) to e), that is, the optical fiber cable is also subjected to the rotating device stations S1 to S N The fibers are twisted together and then bundled together with the group of elongated flexible members A to C by machine M at a second position. Thus, the optical fiber cable is also twisted together with the elongated flexible members A to C in a first direction over a first length L, and then twisted together with the elongated flexible members A to C in a second direction over a first length L. In this example as well, steps a) to e) are repeated until the entire length of the elongated flexible members A to C and the optical fiber cable is laid on the seabed in a twisted form.

[0067] In one example, the optical fiber cable is advanced just before the second position, i.e., after the final rotating device stations S1-SN, and joined to a group 15 of elongated flexible members after the final rotating device stations S1-SN. In this case, the optical fiber cable is not twisted together with the elongated flexible members.

[0068] The concept of the present invention has been described above primarily with reference to several examples. However, it will be readily apparent to those skilled in the art that other embodiments not disclosed above are also possible within the scope of the concept of the present invention as defined by the appended claims.

Claims

1. A method for simultaneously laying three or more elongated flexible members (A, B, C) on the seabed from a ship (1), a) Moving all the individual elongated flexible members (A, B, C) forward to a first position where they are gathered together to form a group (15) of elongated flexible members (A, B, C), b) The group (15) of elongated flexible members (A, B, C) is advanced from the first position to a second position located at a first distance (L) from the first position, and the group (15) of elongated flexible members (A, B, C) is twisted at least once in the first direction between the first position and the second position to obtain a section (21) of elongated flexible members twisted in the first direction. c) At the second position, at least a portion of the elongated flexible member group section (21) twisted in the first direction is bound together, d) The group (15) of elongated flexible members (A, B, C) is advanced from the first position to the second position, and the group (15) of elongated flexible members (A, B, C) is twisted at least two times in a second direction opposite to the first direction between the first position and the second position to obtain an elongated flexible member group section (23) twisted in the second direction following the elongated member group section (21) twisted in the first direction, e) At the second position, at least a portion of the elongated flexible member group section (23) twisted in the second direction is bound together, The process is repeated until the entire length of the elongated flexible members (A, B, C) is laid on the seabed in an alternating twisted configuration. Methods that include...

2. The method according to claim 1, wherein in steps b) and d), the group (15) of elongated flexible members (A, B, C) is advanced in a direction toward the stern (5) of the installation vessel (1).

3. The method according to claim 1 or 2, wherein the first distance (L) is equal to or greater than the catenary length of one of the group (15) of elongated flexible members (A, B, C) extending from the installation vessel (1) toward the seabed.

4. The method according to any one of claims 1 to 3, wherein the installation vessel includes N spaced-apart rotating device stations (S1, S2, SN) arranged on a deck (3), the first of the rotating device stations (S1) being located at the first position, the other N-1 rotating device stations (S2, SN) being located between the first position and the second position, the group (15) of elongated flexible members (A, B, C) being advanced through the rotating device stations (S1, S2, SN), and the group (15) of elongated flexible members (A, B, C) being twisted 1 / N times at each rotating device station (S1, S2, SN).

5. The method according to claim 4, wherein N = 3.

6. The method according to any one of claims 1 to 5, wherein the installation vessel (1) is equipped with laying tensioners (T1, T2, T3) that advance the individual elongated flexible members (A, B, C) toward the first position.

7. The method according to any one of claims 1 to 6, wherein each laying tensioner (T1, T2, T3) advances one of the individual elongated flexible members (A, B, C) toward the first position.

8. The method according to any one of claims 1 to 7, wherein the elongated flexible members (A, B, C) are power cables.

9. The method according to claim 8, wherein the first and second of the elongated flexible members (A, B, C) are DC cables, and the third of the elongated flexible members (A, B, C) is a metal return cable.

10. The method according to any one of claims 1 to 9, wherein the installation vessel (1) is a cable laying vessel.

11. The method according to any one of claims 1 to 10, wherein step a) includes advancing an optical fiber cable having an outer diameter smaller than that of the elongated flexible members (A, B, C) to the first position where it is grouped together with the elongated flexible members (A, B, C), and the optical fiber cable grouped together with the elongated flexible members (A, B, C) is subjected to steps a) to e) and its repetition.

12. The method according to any one of claims 1 to 11, wherein there are three elongated flexible members (A, B, C), and in step a), the three individual elongated flexible members (A, B, C) are grouped together in a trefoil configuration.

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