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

Abstract

This invention provides a method for simultaneously laying three or more flexible, elongated members on the seabed from a mounting vessel. [Solution] A method for simultaneously laying multiple long members on the seabed from a ship, comprising: a) arranging a first flexible long member 9a and a second flexible long member 9b in parallel, and arranging optical fiber cables 11 between, above, or below the first flexible long member 9a and the second flexible long member 9b, and advancing them to a first binding device B1; b) binding the first flexible long member 9a, the second flexible long member 9b, and the optical fiber cables 11 to form a first cable bundle 13; c) advancing the first cable bundle 13 and the third flexible long member 9c to a second binding device B2; d) binding the first cable bundle 13 and the third flexible long member 9c to form a second cable bundle 15; and e) lowering the second cable bundle 15 toward the seabed.

Description

TECHNICAL FIELD

[0001] The present disclosure generally relates to laying flexible long members such as power cables from an installation vessel to the seabed.

BACKGROUND ART

[0002] Submarine cables are installed from marine vessels such as cable laying ships or barges. In many cases, the submarine cables are fed from drums or turntables to the seabed via curved chutes or laying wheels arranged on the vessel. Therefore, the submarine cables are bent when laid on the chutes. When the submarine cables land on the seabed, they are bent in a direction generally opposite to the direction on the chutes or laying wheels.

[0003] In recent years, power cable systems have begun to be designed to include three Direct Current (DC) submarine power cables that connect two points of a power generation system. One is for the positive electrode, one is for the negative electrode, and one is a metal return cable core. Such a cable system may further include a submarine optical fiber cable extending outward along the length direction of the submarine power cables. This introduces new installation complexity compared to a cable system comprising two High Voltage Direct Current (HVDC) cables and one optical fiber cable. This is particularly true considering that installing all submarine cables connecting two points at the same time has the advantage of saving installation time, thereby reducing the risk of changing weather conditions at sea and the associated costs. Another advantage is that only a single trenching or burial operation is required, rather than two separate trenches, resulting in less seabed disturbance, which means less environmental impact and reduced impact on benthic organisms.

SUMMARY OF THE INVENTION

[0004] The common simultaneous installation of multiple cables can be achieved by bundling all submarine cables together and lowering them into the water together. Lowering cables in a planar configuration, i.e., aligned side by side in a single plane, is problematic because it is difficult to maintain catenary stability. Cables with lower specific gravity tend to deviate from their alignment with other cables, creating 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 bottom. This results in a mismatch in the lengths of the power cables. With respect to the curve formed by the bundle, the inner power cables are compressed and the outer power cables are stretched. If the bundle is tight, this can create large compressive and tensile forces on individual cables within the bundle, and can increase the complexity during the installation process.

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

[0006] Therefore, a method is provided for simultaneously laying multiple long members on the seabed from an installation vessel, the method comprising: a) arranging a first flexible long member and a second flexible long member in parallel, and arranging fiber optic cables between, above, or below the first flexible long member and the second flexible long member, and advancing them to a first bundling device; b) bundling the first flexible long member, the second flexible long member, and the fiber optic cables to form a first cable bundle; c) advancing the first cable bundle and the third flexible long member to a second bundling device; d) bundling the first cable bundle and the third flexible long member to form a second cable bundle; and e) lowering the second cable bundle toward the seabed.

[0007] As a result, the flexible elongated members are maintained in their relative positions during the laying process, and therefore the second cable bundle exhibits catenary stability. Consequently, the risk of the fiber optic cables moving around within the second cable bundle is reduced.

[0008] Laying long members on the seabed includes both laying long members on the surface of the seabed and laying them below the surface of the seabed, and includes, for example, laying them in trenches formed by trenchers or seabed plows.

[0009] According to one embodiment, the first flexible elongated member and the second flexible elongated member have the same outer diameter.

[0010] The first flexible elongated member and the second flexible elongated member may have the same cross-sectional structure.

[0011] According to one embodiment, the third flexible elongated member has a smaller outer diameter than the first flexible elongated member and the second flexible elongated member.

[0012] The third flexible elongated member may have a different cross-sectional structure from the first flexible elongated member and the second flexible elongated member.

[0013] According to one embodiment, the first flexible elongated member is a first power cable, and the second flexible elongated member is a second power cable.

[0014] According to one embodiment, the first power cable is a first DC power cable, and the second power cable is a second DC power cable.

[0015] The first DC power cable may be a first HVDC power cable. The second DC power cable may be a second HVDC power cable.

[0016] According to one embodiment, the third flexible elongated member is a metal return cable.

[0017] For example, the first power cable may be a first alternating current (AC) power cable.

[0018] For example, the second power cable may be a second AC power cable.

[0019] According to one embodiment, step b) includes spirally winding a binding material around a first flexible elongated member, a second flexible elongated member, and an optical fiber cable in a first twisting direction, and step d) includes spirally winding a binding material around a first cable bundle and a third flexible elongated member in a second twisting direction opposite to the first direction.

[0020] The first twist direction is either S or Z, and the second twist direction is Z if the first twist direction is S, and S if the first twist direction is Z.

[0021] According to one embodiment, in step d), the first cable bundle and the third flexible elongated member are bundled together such that the first flexible elongated member, the second flexible elongated member, and the third flexible elongated member are arranged flat within the second cable bundle.

[0022] According to one embodiment, the installation vessel is a cable-laying vessel.

[0023] In general, all terms used in the claims should be interpreted according to their common meaning in the art unless otherwise expressly defined herein. All references to “an element, apparatus, component, means,” etc., should be interpreted openly as referring to at least one example of such element, apparatus, component, means, etc., unless otherwise expressly defined.

[0024] Specific embodiments of the concept of the present invention will be described below with reference to the attached drawings as an example. [Brief explanation of the drawing]

[0025] [Figure 1] This is a plan view showing an example of the aft deck of an installation vessel. [Figure 2] This is a diagram showing cross-sections at different positions along the length direction of a flexible long member extending on the aft deck. [Figure 3] This is a diagram showing cross-sections at different positions along the length direction of a flexible long member extending on the aft deck. [Figure 4] This is a flowchart of a method for simultaneously laying a plurality of flexible long members from an installation vessel to the seabed. [Mode for Carrying Out the Invention]

[0026] The inventive concept will be described in more detail below with reference to the accompanying drawings, in which exemplary embodiments are shown. However, the inventive concept may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Throughout the description, the same numerals refer to the same elements.

[0027] Figure 1 is a plan view of the aft deck 3 of the installation vessel 1.

[0028] The installation vessel 1 may be, for example, a cable laying vessel or a cable laying barge.

[0029] The installation vessel 1 has a chute or a laying wheel 7. The chute or laying wheel 7 may be provided at the stern 5 of the installation vessel 1.

[0030] The installation vessel 1 is configured to simultaneously lay three flexible long members and one optical fiber cable to the seabed via the chute or laying wheel 7. The flexible long elements may be power cables, in particular submarine power cables, flexible pipelines, flexible umbilicals, or communication cables.

[0031] In the case of power cables, the first and second flexible elongated members may be DC cables such as HVDC cables, and the third of the three flexible elongated members may be a metal return cable or a redundant cable. In this case, the first and second flexible elongated members may have the same outer diameter, and the third flexible elongated member may have a smaller outer diameter than the first and second flexible elongated members. In another example, the first, second, and third flexible elongated members may be AC ​​cables.

[0032] In the example described herein, three flexible elongated members are laid simultaneously on the seabed from the installation vessel 1. Furthermore, fiber optic cables are laid on the seabed together with the flexible elongated members.

[0033] The installation vessel 1 may be equipped with multiple track tensioners, i.e., tension-applying devices. The track tensioners may be located on the aft deck 3. Each track tensioner may be, for example, a track tensioner or a capstan wheel.

[0034] In this example, the number of laying tensioners is three, i.e., one for each flexible elongated member. In other examples, fewer laying tensioners may be needed to advance three flexible elongated members. For example, in one example, two flexible elongated members may be arranged in a piggyback configuration and advanced along the aft deck by a single laying tensioner, such as a twin cable / product tensioning device. In this case, fewer than three laying tensioners would be required.

[0035] The installation vessel 1 may also be provided with a plurality of fastening devices B1 and B2 located on the aft deck 3. In this example, the installation vessel 1 is provided with a first fastening device B1 and a second fastening device B2. The first fastening device B1 and the second fastening device B2 are located on the aft deck 3.

[0036] The first fastening device B1 and the second fastening device B2 are positioned one fore and aft of each other in the direction toward the stern 5, that is, in the stern direction, parallel to the central longitudinal axis of the installation vessel 1. The fastening devices B1 and B2 are positioned one fore and aft of each other between the laying tensioner and the chute or laying wheel 7 of the installation vessel 1.

[0037] The first binding device B1 and the second binding device B2 may be arranged in a straight line relative to each other.

[0038] The first binding device B1 and the second binding device B2 may be arranged in a straight line with the chute or laying wheel 7.

[0039] The first fastening device B1 is located at a first position on the aft deck 3. The first fastening device B1 is located closer to the laying tensioner than the second fastening device B2. The second fastening device B2 is located closer to the chute or laying wheel 7 than the first fastening device B1.

[0040] For example, the second fastening device B2 may be wider or broader than the first fastening device B1 in the direction from port to starboard. Alternatively or additionally, the first fastening device B1 and the second fastening device B2 may be offset from each other in the direction from port to starboard, but may overlap in the direction toward the stern 5 along an axis parallel to the central longitudinal axis of the ship 1 on which it is installed.

[0041] Installation vessel 1 may include one or more storage units, such as cable drums, turntables, or cable carousels, for storing flexible elongated members to be laid on the seabed. The flexible elongated members are fed from one or more storage units to bundling devices B1 to B2 by a laying tensioner, as will be described in more detail below.

[0042] Referring to Figures 1 to 4, the method for simultaneously laying multiple flexible elongated members 9a, 9b, and 9c together with the optical fiber cable 11 from the installation vessel 1 to the seabed will be described below.

[0043] In step a), the first flexible elongated member 9a and the second flexible elongated member 9b are advanced to the first bundling device B1 with the optical fiber cable 11 positioned between, above, or below the first flexible elongated member 9a and the second flexible elongated member 9b.

[0044] The first flexible elongated member 9a, the second flexible elongated member 9b, and the optical fiber cable 11 are advanced parallel to each other.

[0045] The first flexible elongated member 9a and the second flexible elongated member 9b may be advanced by one or more laying tensioners.

[0046] The first flexible elongated member 9a and the second flexible elongated member 9b may abut or touch each other when they are advanced side by side toward the first binding device B1. Since the optical fiber cable 11 is located above or below the first flexible elongated member 9a and the second flexible elongated member 9b, the first flexible elongated member 9a, the second flexible elongated member 9b, and the optical fiber cable 11 are arranged in a trefoil configuration.

[0047] The first flexible elongated member 9a, the second flexible elongated member 9b, and the optical fiber cable 11 may be advanced toward the first bundling device B1, while the third flexible elongated member 9c is advanced toward the second bundling device B2.

[0048] In the example shown in Figure 1, the third flexible elongated member 9c is advanced adjacent to the second flexible elongated member 9b, parallel to the first flexible elongated member 9a, the second flexible elongated member 9b, and the optical fiber cable 11.

[0049] The third flexible elongated member 9c may be advanced by a laying tensioner.

[0050] In step b), the first flexible elongated member 9a, the second flexible elongated member 9b, and the optical fiber cable 11 are bundled together by the first bundling device B1 to form the first cable bundle 13.

[0051] The fastening may be performed using fastening materials 14 such as silo wrap / high-strength cling film, elastic strap bands, or polymer yarn.

[0052] The bundling in step b) may be performed continuously along the entire length of the first flexible elongated member 9a, the second flexible elongated member 9b, and the optical fiber cable 11, which are lowered to the seabed.

[0053] The bundling in step b) may include spirally wrapping the bundling material 14 around the first flexible elongated member 9a, the second flexible elongated member 9b, and the optical fiber cable 11 in the first twisting direction.

[0054] Figure 2 shows a cross-section of the first cable bundle 13 as seen in the direction of the stern 5, at a position behind the first binding device B1 and in front of the second binding device B2. The first flexible elongated member 9a, the second flexible elongated member 9b, and the optical fiber cable 11 are arranged in a trefoil configuration. The first flexible elongated member 9a, the second flexible elongated member 9b, and the optical fiber cable 11 are bound together with binding material 14.

[0055] The third flexible elongated member 9c bypasses the first binding device B1. Therefore, the third flexible elongated member 9c is not bound to the first flexible elongated member 9a, the second flexible elongated member 9b, and the optical fiber cable 11 by the first binding device B1.

[0056] In step c), the first cable bundle 13 and the third flexible elongated member 9c are advanced to the second binding device B2.

[0057] When the third flexible elongated member 9c and the first cable bundle 13 are advanced toward the second binding device B2, the third flexible elongated member 9c may abut against or come into contact with the first cable bundle 13.

[0058] In step d), the first cable bundle 13 and the third flexible elongated member 9c are bound together to form the second cable bundle 15.

[0059] The fastening may be performed using a fastening material 17 such as silo wrap / high-strength cling film, elastic strap band, or polymer yarn.

[0060] The binding in step d) may be performed continuously along the entire length of the first cable bundle 13 and the third flexible elongated member 9c that are lowered toward the seabed.

[0061] Step d) may include spirally winding the binding material 17 around the first cable bundle 13 and the third flexible elongated member 9c in a second twisting direction opposite to the first direction. Alternatively, step d) may include spirally winding the binding material around the first cable bundle 13 and the third flexible elongated member 9c in the first twisting direction. In this case, the binding in steps b) and d) may include spirally winding the binding material in the same direction.

[0062] Figure 3 shows a cross-section of the second cable bundle 15 viewed from behind the second binding device B2, towards the stern 5. In the second cable bundle 15, the first flexible elongated member 9a, the second flexible elongated member 9b, and the third flexible elongated member 9c are arranged in a flat configuration. The first cable bundle 13 and the third flexible elongated member 9c are bound together with binding material 17.

[0063] In step e), the second cable bundle 15 is lowered to the seabed. The second cable bundle 15 may be lowered from the installation vessel 1 toward the seabed via a chute or laying wheel 7.

[0064] The concept of the present invention has been described above primarily with reference to a few examples. However, as will be readily apparent to those skilled in the art, 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 multiple long members (9a, 9b, 9c) on the seabed from a mounting vessel, a) The first flexible elongated member (9a) and the second flexible elongated member (9b) are arranged in parallel, and the optical fiber cable (11) is positioned between, above, or below the first flexible elongated member (9a) and the second flexible elongated member (9b), and the two are advanced to the first bundling device (B1). b) The first flexible elongated member (9a), the second flexible elongated member (9b), and the optical fiber cable (11) are bundled together to form a first cable bundle (13), c) Moving the first cable bundle (13) and the third flexible elongated member (9c) forward to the second binding device (B2), d) The first cable bundle (13) and the third flexible elongated member (9c) are bound together to form a second cable bundle (15), e) A method comprising lowering the second cable bundle (15) toward the seabed.

2. The method according to claim 1, wherein the first flexible elongated member (9a) and the second flexible elongated member (9b) have the same outer diameter.

3. The method according to claim 1 or 2, wherein the third flexible elongated member (9c) has a smaller outer diameter than the first flexible elongated member (9a) and the second flexible elongated member (9b).

4. The method according to any one of claims 1 to 3, wherein the first flexible elongated member (9a) is a first power cable and the second flexible elongated member (9b) is a second power cable.

5. The method according to claim 4, wherein the first power cable is a first DC power cable and the second power cable is a second DC power cable.

6. The method according to any one of claims 1 to 5, wherein the third flexible elongated member (9c) is a metal return cable.

7. The method according to any one of claims 1 to 6, wherein the bundling in step b) includes spirally winding a bundling material (14) around the first flexible elongated member (9a), the second flexible elongated member (9b), and the optical fiber cable (11) in a first twisting direction, and step d) includes spirally winding a bundling material (17) around the first cable bundle (13) and the third flexible elongated member (9c) in a second twisting direction opposite to the first direction.

8. The method according to any one of claims 1 to 7, wherein in step d), the first cable bundle (13) and the third flexible elongated member (9c) are fastened together such that the first flexible elongated member (9a), the second flexible elongated member (9b), and the third flexible elongated member (9c) are arranged flat within the second cable bundle (15).

9. The method according to any one of claims 1 to 8, wherein the installation vessel (1) is a cable laying vessel.

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