Support and method for towing a load at sea

Abstract

A support for towing a load (20) at sea is disclosed. The support (10) comprises a first support element (100), the first support element (100) being rigid and extending from, at least, a first point (110) of the first support element (100) to a second point (120) of the first support element (100), the first point (110) being attachable to a vessel (30) and the second point (120) being attached to a second support element (200). The second support element (200) being rigid and connects the first support element (100) to at least two buoyancy parts (210, 220, 230, 235), the at least two buoyancy parts (210, 220, 230, 235) being arranged at a distance (240) between each other and, when in use, at least a section of the at least two buoyancy parts (210, 220, 230, 235) extends to below the sea surface (40). A tow line support (260) for a tow line (300) for towing the load (20), the tow line support (260) being arranged in the vicinity of the second point (120). A vessel and the support is also disclosed. A method of towing a load (20) at sea is disclosed. The method comprises attaching (710) the support to a vessel (30); attaching (720) a tow line (300) from the vessel (30) via the support to the load (20); adjusting (730) the length of the tow line (300) to a predetermined towing depth of the load (20) subsea; and towing (740) the load (20) by the vessel (30) pulling the load at sea.

Description

[0001] SUPPORT AND METHOD FOR TOWING A LOAD AT SEA

[0002] Technical Field

[0003] The present disclosure relates to a support for trailing a load at sea, a vessel with such a support, and a method for trailing a load at sea. More specifically the present disclosure relates to a vessel trailing a load subsea in the energy industry.

[0004] Background

[0005] The energy industry requires transportation of structures at sea. Transportation of a subsea structure by a vessel may result in damage, or even loss, to the load and damage to the vessel. One would like to use the existing fleet of vessels for towing loads at sea. Two examples of subsea towing are the Pencil Buoy method, see WO03074353A1, and the Moon Pool method where the tow line goes through a central opening of the vessel.

[0006] Towing of a structure subsea creates problems, such as, sufficient towing speed, influence of weather, routing of towing, load capacity of vessel and crane, movements of the load during, and caused by, towing, vessel, and sea, and load on the tow line. It is with these in mind that one seeks to improve towing a load at sea. Using a crane on a vessel for towing puts a limit on the load that can be towed because the crane has only a certain capacity.

[0007] A technical problem associated with the known methods of towing is how to dampen the load in the tow line. A further technical problem is that any solution must function without a possibility to fail, fulfil technical and legal requirements, and be easy to use. It is desirable that any solution is simple, not expensive to produce, and is reliable. It is further a technical problem to avoid cumbersome arrangements that are expensive to manufacture, use, or assemble.

[0008] Summary of the invention

[0009] It is an object of the present invention to provide a support for towing a load at sea, a vessel with such a support, and a method for towing a load at sea. This object can be achieved by the features as defined by the independent claim. Further enhancements are characterized by the dependent claims. The invention is defined by the claims.

[0010] According to one embodiment, a support for towing a load at sea, preferably subsea, is disclosed. The support 10 comprises a first support element 100, a second support element 200, and a tow line support 260. The a first support element 100 is rigid and extends from, at least, a first point 110 of the first support element 100 to a second point 120 of the first support element 100, the first point 110 being attachable to a vessel 30 and the second point 120 being attached to a second support element 200. The second support element 200 being rigid and connects the first support element 100 to at least two buoyancy parts 210, 220, 230, 235, the at least two buoyancy parts 210, 220, 230, 235 being arranged at a distance 240 between each other and, when in use, at least a section of the at least two buoyancy parts 210, 220, 230, 235 extends to below the sea surface 40. The tow line support 260 is for a tow line 300 for towing the load 20, the tow line support 260 being arranged in the vicinity of the second point 120. The support may be a passive heave compensator.

[0011] The support 10 may further comprising a coupling 400 arranged at the first point 110 and attachable, or attached, to the vessel 30, the coupling comprising three rotational degrees of freedom. The coupling 400 may further comprises a quick release mechanism for detaching the support from the vessel 30.

[0012] The at least two buoyancy parts 210, 220, 230, 235 may be arranged opposite each other and the second support element 200 separates the at least two buoyancy parts 210, 220, 230, 235 by the distance 240, the distance 240 being perpendicular to a direction 250 of towing. The number of at least two buoyancy parts 210, 220, 230, 235 may be an even number with equal number of buoyancy parts opposite each other. The second support element 200 may extend in a horizontal direction when in use. The at least two buoyancy parts 210, 220, 230, 235 may comprise at least two vertical part 230, 235 extending in a vertical direction, and at least two horizontal parts 210, 220 extending in a horizontal direction, each vertical part 230, 235 extending from the second support element 200 to one of the at least two horizontal parts 210, 220. When in use, at least a section of the at least two vertical parts 230, 235 may extend to below the sea surface 40. The at least two horizontal parts 210, 220 may extend mainly in a direction 250 of towing.

[0013] One or more of the at least two buoyancy parts 210, 220, 230, 235 may be adjustable buoyancy parts for adjusting buoyancy. Additional buoyancy parts may be added, for example attached to the outside of the at least two buoyancy parts 210, 220, 230, 235, to increase the buoyancy of the support.

[0014] The first support element 100 may further comprise a third buoyancy part 130 positioned in the vicinity of the first point 110. The tow line support 260 may comprise a block, the block being arranged with one rotational degree of freedom R1 arranged substantially parallel to the first support element 100. The support may further comprise a tow line 300 for towing the load 20. The tow line 300 may be attachable between an attachment point at the vessel 30, through the coupling 400, via the tow line support 260, to the load 20. The support may further comprising a guide 450 for the tow line 300 arranged before the coupling 400, in relation to a direction 250 of towing. The support may further comprising lines 600 attached to the support, the lines 600 being attachable to the vessel 30.

[0015] According to one embodiment, a vessel and the support, disclosed herein, are disclosed, where the vessel 30 comprises a winch 32 for the tow line 300. The first support element 100, the second support element 200, and the at least two buoyancy parts 210, 220, 230, 235 may be releasably connected to each other to form a modular support. This allows a modular construction of the support to allow the support to be configured for towing a specific load 20.

[0016] According to one embodiment, a method of towing a load 20 at sea is disclosed. The method comprises attaching 710 the support 10 according to any one of the embodiments disclosed herein to a vessel 30; attaching 720 a tow line 300 from the vessel 30 via the support to the load 20; adjusting 730 the length of the tow line 300 to a predetermined towing depth of the load 20 subsea; and towing 740 the load 20 by the vessel 30 pulling the load at sea.

[0017] The method may further comprise picking up the load 20 inshore, preferably from a barge 60, by placing the load 20 in between the at least two buoyancy parts 210, 220. The method may further comprise adjusting the buoyancy of the support. The method may further comprise attaching a line, in addition to the tow line 300, from the support to the load 20. The method may further comprise detaching the support from the vessel 30 and parking the support, with or without the load 20, at sea. The method may further comprise pulling the load 20 up, by the tow line 300, in between the at least two buoyancy parts 210, 220. The method may further comprise lowering the load 20 to the seabed at an offshore site by reeling out the tow line 300.

[0018] The above embodiments provides one or more solutions to the problems and disadvantages with the background art. Other technical advantages of the present disclosure will be readily apparent to one skilled in the art from the following description and claims. Various embodiments of the present application obtain only a subset of the advantages set forth. No one advantage is critical to the embodiments. Any claimed embodiment may be technically combined with any other claimed embodiment or embodiments.

[0019] Brief description of the drawings

[0020] The following drawings illustrate exemplary embodiments of the disclosure and serve to explain, by way of example, the principles of the disclosure:

[0021] Figure 1 is a diagrammatic and schematic illustration of a support according to an exemplary embodiment of the disclosure;

[0022] Figure 2 is a diagrammatic and schematic illustration of a support, viewed from the side, according to an exemplary embodiment of the disclosure;

[0023] Figure 3 is a diagrammatic and schematic illustration of a support, viewed in the opposite direction of towing, according to an exemplary embodiment of the disclosure;

[0024] Figure 4 is a diagrammatic and schematic illustration of a section from figure 2, cut along the tow line, of a support according to an exemplary embodiment of the disclosure;

[0025] Figure 5 is a diagrammatic and schematic illustration of a support during loading of a load at sea according to an exemplary embodiment of the disclosure;

[0026] Figures 6 and 7 are a diagrammatic and schematic illustrations of a support towing a load at sea according to an exemplary embodiment of the disclosure; and

[0027] Figure 8 is a diagrammatic illustration of a method for towing a load at sea according to an exemplary embodiment of the disclosure.

[0028] Detailed description

[0029] Figures 1 to 7 are diagrammatic and schematic illustrations of a support 10 for towing a load 20 at sea. The load 20 and the vessel 30 in the figures are only schematically illustrated. Figures 1 to 3 illustrate the support 10, and figure 4 is a detail of the support 10. Figure 4 shows the area marked with A in figure 2. Figures 5 to 7 illustrate how the load 20 may be handled using the support 10 and a vessel 30. Figure 6 illustrates two loads 20, one load 20 illustrates towing in shallow water, the other load 20 illustrates towing in deeper water. Figure 8 is a schematic illustration of a method according to an embodiment.

[0030] Figure 1 illustrates a support for towing a load 20 at sea. The support 10 comprises a first support element 100, a second support element 200, and a tow line support 260. The first support element 100 is rigid and extends from, at least, a first point 110 of the first support element 100 to a second point 120 of the first support element 100. The first point 110 is attachable to a vessel 30 and the second point 120 is attached to the second support element 200. The second support element 200 is rigid and connects the first support element 100 to at least two buoyancy parts 210, 220, 230, 235. The at least two buoyancy parts 210, 220, 230, 235 are arranged at a distance 240 between each other. When in use, at least a section of the at least two buoyancy parts 210, 220, 230, 235 extends to below the sea surface 40. The tow line support 260 is for a tow line 300 for towing the load 20, for example a wire, rope, or chain. The tow line support 260 being arranged in the vicinity of the second point 120.

[0031] The load 20 may be very heavy, for example weighing over a thousand tons in air. The load 20 may be large and bulky. It may be a subsea element, for example for an offshore installation or a subsea installation. The load 20 may be a storage tank, empty or filled. The support 10 may function as a heave compensator, a passive heave compensator, for the load 20. The vertical force in a tow line 300 is taken up by the support 10 and not transferred onto the vessel 30. The equipment, for example a crane or a winch, on the vessel 30 need only to take up the horizontal force in the tow line 300 according to at least one embodiment disclosed herein. The support 10 may also dampen the forces acting along the tow line 300. The support 10 floats on the sea and can, as explained herein, swing about its attachment to, and relative to, the vessel 30. This dampens any movements in the tow line 300 caused by the vessel 30 or the load 20 and is taken up by the support 10. The support 10 allows a vessel 30 to tow a heavy load 20 in a controlled manner.

[0032] As illustrated in figures 1 to 3, the first support element 100 is rigid, and may be an inflexible structure, for example a steel cylinder or pipe or a hollow reinforced structure made out of metal. The first support element 100 is not a tow line, nor a wire or a cable. The first support element 100 may be an elongate member extending from the first point 110 to the second point 120, as illustrated from the vessel 30 to the second support element 200. The extension may be configured to ensure that the tow line 300 is far enough from the vessel 30, for example to avoid the tow line 300 to contact a propeller of the vessel 30. The extension may be configured to ensure that the support 10 can swing adequately around the first point 110 attached to the vessel 30 for dampening any forces acting along the tow line 300. The first support member 100 and the second support element 200 are attached to each other, for example permanently attached, such as welded, to each other at the second point 120. They may be releasably attached to each other, for example bolted to each other. This allows the second support element 200 to be interchanged, and therefore the support can be configured for a specific load 20. The first support member 100 extends between the vessel 30 and the second support member 200. The first support member 100 may extend in the direction 250 of towing and the second support member 200 may extend in a direction that is perpendicular to the direction 250 of towing. The second support member 200 is rigid and is not a tow line, nor a wire or a cable. The second support member 200 may extend in the horizontal direction and at each end of the second support member 200 may the at least two buoyancy parts 210, 220, 230, 235 be arranged substantially extending in a vertical direction. As illustrated in figures 1 to 3, the second support member 200 may extend in a horizontal direction, and at each end thereof may at least two vertical parts 230, 235 be arranged and extend in a vertical direction. To each vertical part 230, 235 may be arranged each one or more of the at least two buoyancy parts 210, 220. This may take form substantial as an upsidedown II shape to which the first support member 100 connects at the middle of the II and the two legs of the II is L shaped.

[0033] The at least two buoyancy parts 210, 220, 230, 235 may render the support 10 buoyant at sea. The second support element 200 may extend in a horizontal direction that is perpendicular to the direction 250 of towing. At least one buoyant part 210, 230 may be at one end of the second support element 200 and at least one other buoyant part 220, 235 may be at the opposite end of the second support element 200. This may arrange the at least two buoyancy parts 210, 220, 230, 235 at a distance 240 between each other. This is best illustrated in figure 1. The same number of buoyancy parts 210, 220, 230, 235 may be on each side of the second support element 200. It may be sufficient with only one buoyancy part 230 on one side of the second support element 200 and only one buoyancy part 235 on the other side. The distance 240 may be larger than a width of the load 20. The at least two buoyancy parts 210, 220, 230, 235 may be arranged such that they are in the sea when the support 10 is in use. The distance 240 between the at least two buoyancy parts 210, 220, 230, 235 may be configured to give the support 10 stability and provide efficient damping. The second support element 200 may extend from the first support element 100, mainly above the sea surface 40 when in use, to the at least two buoyancy parts 210220, 230, 235. This may allow the support 10, when in use, to comprise at least a section of the at least two buoyancy parts 210 220, 230, 235 extending to below the sea surface 40.

[0034] The tow line support 260 may be arranged at the connection of the first support element 100 and the second support element 200. The second point 120 is at the connection of the first support element 100 and the second support element 200. The tow line support 260 may be arranged on the second support element 200, preferably in the middle between the at least two buoyancy parts 210, 220, 230, 235. The tow line support 260 may be arranged on the support 10 as far away from the vessel 30 as possible. The tow line support 260 may be arranged substantially above the at least two buoyancy parts 210, 220, 230, 235 for maximising heave compensation and damping. The tow line support 260 may be arranged half way of the distance perpendicular to the towing direction 250 and between the at least two buoyancy parts 210, 220, 230, 235, preferably the second point 120 is also located there. As illustrated in the figures, the tow line support 260 may be for guiding a tow line 300 from the vessel 30, via the tow line support 260, to the load 20. The tow line support 260 may be arranged such that it together with the tow line 300 can take up the vertical load component of the load 20 without any interference by any other parts of the support 10. The tow line support 260 may be a sheave block.

[0035] As best illustrated in figures 1 and 4, the support 10 may further comprise a coupling 400 arranged at the first point 110. The coupling 400 may be attachable, or attached, to the vessel 30. The coupling 400 couples the support 10 and vessel 30 together. The coupling 400 comprising three rotational degrees of freedom, R1 , R2, R3 as illustrated in figure 1. The coupling 400 may be part of the vessel 30, for example permanently arranged on the vessel 30. The coupling 400 may be part of the support 10, for example permanently arranged at the first point 110 of the support 10. The coupling 400 allows the support 10 to rotate in three rotational degrees of freedom R1 , R2, R3. The three rotational degrees of freedom R1 , R2, R3 are perpendicular to each other, as may best be taken from figures 1 and 4. The three rotational degrees of freedom R1, R2, and R3 may correspond to roll R1, yaw R2, and pitch R3, of the vessel 30. The support 10 may rotate in the three rotational degrees of freedom R1 , R2, R3, relative to the vessel 30, when coupled to the vessel 30. The coupling 400 may be made up from a number of gimbals, each gimbal providing one rotational degree of freedom. The coupling 400 may further comprise a quick release mechanism for detaching the support 10 from the vessel 30. The quick release mechanism may be used for disconnecting the support 10 from the vessel 30, for example in case of emergency. The quick release mechanism may be operated from the vessel 30. The quick release mechanism may disconnect the support 10 at the first point 110.

[0036] The at least two buoyancy parts 210, 220, 230, 235 may be arranged opposite each other, in the direction perpendicular to the direction 250 of towing. The second support element 200 may separate the at least two buoyancy parts 210, 220, 230, 235 the distance 240. The distance 240 being perpendicular to a direction 250 of towing. The at least two buoyancy parts 210, 220, 230, 235 may be at outer sides of the second support element 200, the second support element 200 separating the at least two buoyancy parts 210, 220, 230, 235 the distance 240 perpendicular to the trailing direction. The same number of buoyancy parts 210, 220, 230, 235 on each side may be configured to fit the load 20 between them.

[0037] The second support element 200 extends in a horizontal direction, when in use. The at least two buoyancy parts 210, 220, 230, 235 may comprise at least two vertical parts 230, 235 extending in a vertical direction and at least two horizontal parts 210, 220 extending in a horizontal direction, each vertical part 230, 235 extending from the second support element 200 to one of the at least two horizontal parts 210, 220. When in use, at least a section of the at least two vertical parts 230, 235 may extend to below the sea surface 40 and the at least two horizontal parts 210, 220 may extend mainly in a direction 250 of towing. As may best be taken from figures 1 to 3, the second support element 200 may extend in a horizontal direction and two vertical parts 230, 235 may extend in a vertical direction. Each vertical part 230, 235 may extend down from the second support element 200 and connect to one buoyancy part 210 or 220. Each of the two vertical parts 230, 235 may extend to below the sea surface 40, and thereby arrange each horizontal part 210, 220 to be below the sea surface 40, at least during towing a load 20. The vertical parts 230, 235 may be arranged wider than the load 20, and the horizontal parts 210, 220 may also be arranged wider than the load 20. This allows the support 10 to have the load 20 close to the first support element 100 and close to the tow line support 260. In this way the load 20 can be handled in shallow waters, and picked up, or delivered with at least a part of the load 20 above the sea surface 20. This is illustrated in figure 5. Here a load 20 is held by a barge 60, for example on a support of the barge 60 or hanging from the barge 60. The barge 60 can be raised or lowered allowing the load 20 to best be received by the support 10. The at least two horizontal buoyancy parts 210, 220 may extend mainly in the direction 250 of towing, they may be longer in the direction 250 of towing than any other direction. This is illustrated in figures 1 to 3. This provides improved damping, increased heave compensation, and good stability with little resistance when towing. The horizontal buoyancy parts 210, 220 may be detachably connected to the vertical parts 230, 235. More than one horizontal part may be connected to one vertical part. The horizontal parts 210, 220 and the vertical parts 230, 235 may together comprise a larger volume than the rest of the support 10. For example if the support 10 is constructed mainly out of hollow cylinders, then the diameter of the hollow cylinders may be larger for the at least two buoyancy parts 210, 220, 230, 235, compared with the diameter of the first support element 100.

[0038] According to one embodiment, one or more of the at least two buoyancy parts 210, 220, 230, 235 may be adjustable buoyancy parts 210, 220, 230, 235 for adjusting the buoyancy of the support 10, when at sea. The buoyancy parts 210, 220, 230, 235 may be adjustable, for example, by adding buoyancy volume, by variable ballast means, or a combination of the two. The buoyancy parts 210, 220, 230, 235 may be adjustable by being exchangeable, allowing buoyancy parts 210, 220, 230, 235 of different volumes to be used. For example, only the at least two horizontal parts (210, 220) may be exchangeable. The buoyancy parts 210, 220, 230, 235 may be adjustable by being inflatable to different volumes. The support 10 may comprise an active buoyancy control means for controlling the buoyancy of one or more of the at least two buoyancy parts 210, 220, 230, 235. For example, the support 10 may comprise additional buoyancy elements, for example sponsons, that may be added or attached to the outside of the at least two buoyancy parts 210, 220, 230, 235 to increase the buoyancy of the support 10.

[0039] The first support element 100, the second support element 200, and the at least two buoyancy parts 210, 220, 230, 235 may be releasably connected to each other to form a modular support. At least two of the at least two buoyancy parts 210, 220, 230, 235 may be releasably connected to each other. The at least two buoyancy parts 210, 220, 230, 235 may be releasably connected the second support element 200. The coupling 400 may be releasably connected to the first support element 100. At least one of the first point 110 or second point 120 may comprise a releasable connection. A modular support 10 allow the elements of the support 10 to be exchanged with elements of different dimensions. A support 10 being modular allows the support 10 to be configured easily to different loads 20. The first support element 100 may further comprises a third buoyancy part 130 positioned in the vicinity of the first point 110. The third buoyancy part 130 may be integrated in the first support element 100 and positioned in the vicinity of the first point 110. The three buoyancy parts 130, 210, 220 may be used for parking the support 10 at sea. The three buoyancy parts 130, 210, 220 may each be positioned in a corner of a triangle in a horizontal footprint of the support 10. The support 10 may float at least partly above the sea surface 40 allowing access to the support 10. The support 10 may be visible from a vessel 30 and may be connected to, or disconnected from, a vessel 30. The support 10 may be anchored at sea.

[0040] According to one embodiment the at least two buoyancy parts 210, 220, 230, 235 may be parts of one single buoy. The single buoy may extend in a direction that is substantially perpendicular to the direction 250 of towing. The single buoy may connect two, or more, vertical parts 230, 235 to the second support element 200. When in use, the single buoy may be at least partly below the sea surface 40.

[0041] The tow line support 260 may comprises a block, for the tow line 300. The block may be a sheave block. The block may be arranged with one rotational degree of freedom R1 arranged substantially parallel to the first support element 100. This is best shown in figure 1. In addition to the block’s own rotation, the block may be arranged with the one rotational degree of freedom R1 , where the one rotational degree of freedom R1 may be arranged substantially parallel to the direction 250 of towing. This may be substantially parallel to the first support element 100.

[0042] The support may further comprise a tow line 300 for towing the load 20. The tow line 300 may be attachable from an attachment point at the vessel 30, through the coupling 400, via the cable support 230, to the load 20. The attachment point at the vessel 30 may be a winch 32 or a crane. The tow line 300 may go through the coupling 400 as best illustrated in figure 4. The tow line 300 may go substantially through the intersection of all three rotational degrees of freedom R1, R2, R3, for example through the rotational degree that is substantially parallel to the tow line 300. The tow line 300 may go through an opening of the first support element 100, in the vicinity of the first point 110. As may be taken from figure 4, the tow line 300 does not come in contact with the support, other than the tow line support 260. As the support 10 moves, rotates about the three rotational degrees of freedom, the tow line support 260 and the entry of the tow line 300 at the vicinity of the first point 110 keeps the tow line 300 aligned with the support 10. Therefore the tow line 300 does not come into contact with the support 10, or the first support element 100. The tow line 300 may go through a section of the inside of the first support element 100. The section of the first support element 100 may be hollow, have two openings, and allow the tow line to pass there through.

[0043] The support 10 may further comprising a guide 450 for the tow line 300 arranged before the coupling 400, in relation to the direction 250 of towing. As best illustrated in figure 4, the guide 450 is on one side of the coupling 400, and the support 10 is on the other side of the coupling 400. The guide 450 is preferably close to the coupling 400 and directing the tow line 300 through the centre of the coupling 400. The guide 450 may be, for example, a roller box or a fairlead. The guide 450 may have four rollers forming a square around the tow line 300.

[0044] The support 10 may further comprising lines 600 attached to the support 10, the lines 600 being attachable to the vessel 30, as illustrated in figure 5. The lines 600 may be flexible lines, for example ropes or wires. One or more lines 600 may be attached at the support 10 and at the vessel 30, to ensure that the support 10 is not moving too much in the horizontal plane relative to the vessel 30. The lines 600 may prevent the support 10 to come into contact with the vessel 30. For example when the vessel 30 is still, the lines 600 may prevent the support 10 from drifting and rotating on the sea surface 40 and hitting the vessel 30. The support 10 may comprise one or more attachments 610 for the lines 600, as illustrated in figures 1 to 3, for example two on the first support element 100, and two on the second support element 200.

[0045] As best illustrated in figures 5 to 7, a vessel 30 may comprise the support 10 as described herein. The vessel 30 may comprise a winch 32, or a crane, for the tow line 300. The vessel 30 may tow the support 10 behind the vessel 30, with the tow line 300 attached to the vessel 30 and going, via the tow line support 260, to the load 20. The support 10 may be connected to the vessel 30 by using the coupling 400. The guide 450 and the coupling 400 may be part of the vessel 30, or may be part of the support 10.

[0046] A method of towing a load 20 at sea is disclosed. The method comprises the following steps as illustrated in figure 8 taken in any order as long as it makes technical sense. Attaching 710 the support 10, according to any one embodiment described herein, to a vessel 30. This may be done by using the coupling 400. Attaching 720 a tow line 300 from the vessel 30 via the support 10 to the load 20. Adjusting 730 the length of the tow line 300 to a predetermined towing depth of the load 20 subsea. Towing 740 the load 20 by the vessel 30 pulling the load at sea. The load 20 may be towed subsea. The load 20 may be lowered to the seabed at a predetermined site by reeling out the tow line 300.

[0047] The method may further comprising picking up the load 20 inshore, preferably from a barge 60, by placing the load 20 in between the at least two buoyancy parts 210, 220, as best illustrated in figure 5. The barge 60 may support the load 20 by load support 62 and the support 10 may pick up the load 20 from the barge 60. The barge 60 may support the load 20 with a barge line 64. The load 20 may be lowered or raised by the barge line 64 to allow the support 10 to pick up the load 20 from the barge. The barge 60 may be lowered or raised by changing the buoyancy of the barge 60. This raises and lowers the load 20 attached to the barge 60. Inshore, in shallow water, the load 20 may be picked up and towed offshore. The support 10 may be able to hold the load 20 between the at least two buoyancy parts 210, 220 and this may allow the support 10 to tow a load 20 in very shallow water. The support 10 may pick up the load 20 from a barge 60, for example as illustrated in figure 5. The barge 60 may hold the load 20 to be picked up. A vessel 30 with the support 10 may put the support 10 with at least one of the at least two buoyancy parts 210, 220, 230, 235 on either side of the load 20. This allows the load 20 to be held by the barge 60 very close to the sea surface 40 when the load 20 is to be picked up. The support 10 allows the tow line 300 to be connected from the load 20, via the support 10, to the vessel 30. Subsequently the vessel 30 can leave the barge 60 and tow the load 20. When the vessel is further offshore, at deeper water, then the tow line 300 may be reeled out so that the load 20 is towed at a predetermined depth subsea. This is best illustrated in figure 6, where the load 20 is illustrated close to the support 10 when the load 20 is towed in shallow water, and the load 20 is illustrated away, deeper, from the support 10 when the load 20 is towed in deeper water.

[0048] The method may further comprise adjusting the buoyancy of the support 10. The buoyancy of the support 10 may be adjusted depending on the load 20 that will be towed. The at least two buoyancy parts 210, 220 may be made more or less buoyant by changing their volume and / or adding ballast.

[0049] The method may further comprise attaching a line 310, in addition to the tow line 300, from the support to the load 20, as illustrated in figure 7. The line 310 may be attached on the vessel 30 and go via the support 10 to the load 20. The line 310 may be used as a safety line and / or as a guide line. The line 310 may be used to hang of the load 20 from the support 10 without using the tow line 300 going from the vessel 30 to the load 20. In this way the load 20 can be connected to the support 10 without the use of a winch or crane on the vessel 30. The use of the line 310 directly from the support 10 to the load 20 allows the winch 32 or crane to be used for other operations.

[0050] Figures 6 and 7 illustrates how the support 10 dampens any load in the tow line 300. The support 10 may swing as the load 20 is towed subsea. The support 10 floats on the sea and can, as explained herein, swing about its attachment to, and relative to, the vessel 30. The support 10 may rotate in the three rotational degrees of freedom R1, R2, R3, relative to the vessel 30, when coupled to the vessel 30. This dampens any movements in the tow line 300 caused by the vessel 30 or the load 20 and is taken up by the support 10. Figure 6 illustrates the support 10 higher up than in figure 7. The support 10 allows a vessel 30 to tow a heavy load 20 in a controlled manner and with less strain on the vessel 30.

[0051] The method may further comprise detaching the support 10 from the vessel 30 and parking the support 10, with or without the load 20, at sea. The support 10 may float by itself at sea. The support 10 may float with the load 20 at sea. If the vessel 30 is need for some urgent issue and must stop towing, then the vessel 30 may park the support 10 at sea, with or without the load 20 attached to only the support 10. The support 10 may be moored inshore at a buoy or at a quayside to save space limitations on land when the support 10 is not in use.

[0052] The method may further comprise pulling the load 20 up, by the tow line 300, in between the at least two buoyancy parts 210, 220, 230, 235. By pulling the load 20 up between two of the vertical parts 230, 235 and / or the at least two buoyancy parts 210, 220 on either side of the load 20 the load 20 may be towed in very shallow water. This may also allow the load 20 to be picked up from a barge 60 very close to the sea surface 40.

[0053] The method may further comprise lowering the load 20 to the seabed at an offshore site by reeling out the tow line 300. When the vessel 30 arrives at a site with the support 10 and the load 20, then the vessel 30 may stop towing and unreel the tow line 300. Hereby the load 20 may be placed on the seabed. The support 10 being coupled to the vessel 30 provides a stable and secure support 10 that may lower and place the load 20 at the seabed while dampening the load 20, without damaging the load 20.

[0054] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using the support and performing the methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

[0055] List of elements

[0056] 10 support

[0057] 20 load

[0058] 30 vessel

[0059] 32 winch

[0060] 40 sea surface

[0061] 60 barge

[0062] 62 barge support

[0063] 64 barge line

[0064] 100 first support element

[0065] 110 first point

[0066] 120 second point

[0067] 130 buoyancy part

[0068] 200 second support element

[0069] 210 buoyancy part

[0070] 220 buoyancy part

[0071] 230 intermediate part

[0072] 232 horizontal part

[0073] 234 vertical part

[0074] 240 distance

[0075] 250 direction of towing

[0076] 260 tow line support

[0077] 300 tow line

[0078] 400 coupling

[0079] 450 guide

[0080] 600 line

[0081] 610 attachments

Claims

Claims1 A support for towing a load (20) at sea, the support (10) comprising: a first support element (100), the first support element (100) being rigid and extending from, at least, a first point (110) of the first support element (100) to a second point (120) of the first support element (100), the first point (110) being attachable to a vessel (30) and the second point (120) being attached to a second support element (200); the second support element (200) being rigid and connects the first support element (100) to at least two buoyancy parts (210, 220, 230, 235), the at least two buoyancy parts (210, 220, 230, 235) being arranged at a distance (240) between each other and, when in use, at least a section of the at least two buoyancy parts (210, 220, 230, 235) extends to below the sea surface (40); and a tow line support (260) for a tow line (300) for towing the load (20), the tow line support (260) being arranged in the vicinity of the second point (120).2 The support according to claim 1 , further comprising a coupling (400) arranged at the first point (110) and attachable, or attached, to the vessel (30), the coupling comprising three rotational degrees of freedom.3 The support according to claim 2, wherein the coupling (400) further comprises a quick release mechanism for detaching the support from the vessel (30).4 The support according to any one of the preceding claims, wherein the at least two buoyancy parts (210, 220, 230, 235) are arranged opposite each other and the second support element (200) separates the at least two buoyancy parts (210, 220, 230, 235) by the distance (240), the distance (240) being perpendicular to a direction (250) of towing.5 The support according to claim 4, wherein the second support element (200) extends in a horizontal direction, when in use; the at least two buoyancy parts (210, 220, 230, 235) comprises at least two vertical parts (230, 235) extending in a vertical direction and at least two horizontal parts (210, 220) extending in a horizontal direction, each vertical part (230, 235) extending from the second support element(200) to one of the at least two horizontal parts (210, 220); and, when in use, at least a section of the at least two vertical parts (20, 235) extends to below the sea surface (40) and the at least two horizontal parts (210, 220) extend mainly in a direction (250) of towing.6 The support according to any one of the preceding claims, wherein one or more of the at least two buoyancy parts (210, 220, 230, 235) are adjustable buoyancy parts for adjusting buoyancy.7 The support according to any one of the preceding claims, wherein the first support element (100) further comprises a third buoyancy part (130) positioned in the vicinity of the first point (110).8 The support according to any one of the preceding claims, wherein the tow line support (260) comprises a block, the block being arranged with one rotational degree of freedom (R1) arranged substantially parallel to the first support element (100).9 The support according to any one of the preceding claims 2 to 8, further comprising a tow line (300) for towing the load (20), the tow line (300) being attachable between an attachment point at the vessel (30), through the coupling (400), via the tow line support (260), to the load (20).10 The support according to any one of the preceding claims, further comprising a guide (450) for the tow line (300) arranged before the coupling (400), in relation to a direction (250) of towing; and / or further comprising lines (600) attached to the support, the lines (600) being attachable to the vessel (30).11 The support according to any one of the preceding claims, wherein the first support element (100), the second support element (200), and the at least two buoyancy parts (210, 220, 230, 235) are releasably connected to each other to form a modular support.12 A vessel and the support according to any one of the preceding claims, the vessel (30) comprising a winch (32) for the tow line (300).13 A method of towing a load (20) at sea, the method comprising: attaching (710) the support according to any one of the preceding claims 1-11 to a vessel (30); attaching (720) a tow line (300) from the vessel (30) via the support to the load (20); adjusting (730) the length of the tow line (300) to a predetermined towing depth of the load (20) subsea; and towing (740) the load (20) by the vessel (30) pulling the load at sea.14 The method according to claim 13, further comprising picking up the load (20) inshore, preferably from a barge (60), by placing the load (20 in between the at least two buoyancy parts (210, 220).15 The method according to claim 13 or 14, further comprising adjusting the buoyancy of the support; and / or further comprising attaching a line, in addition to the tow line (300), from the support to the load (20); and / or further comprising detaching the support from the vessel (30) and parking the support, with or without the load (20), at sea; and / or further comprising pulling the load (20) up, by the tow line (300), in between the at least two buoyancy parts (210, 220); and / or further comprising lowering the load (20) to the seabed at an offshore site by reeling out the tow line (300).

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