Floating body structure targeting transportation and installation of floating body type tension leg platform

Abstract

To provide a floating body structure for transportation and installation of a floating body type tension leg platform.SOLUTION: A floating body structure 1 includes controllable ballast tanks 6, 6' for varying its buoyancy and engaging means 9 engaging with leg unit 3 for maintaining necessary draft during transportation and installation. The floating structure includes a multiple number of floating structure parts intended to be positioned adjacent horizontally to each leg unit, the floating structure part includes the engaging means 9 for engaging with a means to be engaged provided on the leg unit, and thus, the engaging means is capable of loading the means to be engaged with downward force against the floating upward force in an action attitude of the floating body structure positioned horizontally lined up with the leg unit, and furthermore, the engaging means is installed to be capable of engaging with the means to be engaged even when one portion of the leg unit is positioned at a height above the sea level.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a floating structure intended for the transportation and installation of a floating Tension Leg Platform (TLP) having multiple legs radiating from a central point. [Background technology]

[0002] Part of the energy transition is the development of offshore wind farms, where the use of seabed fixed structures is the current state of the art. However, such fixed structures are limited to locations with limited water depth. As the demand for renewable energy is growing rapidly, industrial, large-scale solutions for floating offshore wind farms that can be used at greater depths are being researched. As a result, there is strong interest in the use of TLPs to support wind turbines, which can be moored (directly or indirectly) to the seabed using mooring lines (or tendons) attached to their legs. TLP-based wind turbine foundations have high potential in the offshore floating wind market due to their high power / weight ratio and small footprint.

[0003] In the installed and moored condition, the pre-tensioning of the tendons provides stability to the entire TLP system (wind turbine assembly including the TLP) as a result of the excess buoyancy of the TLP. In this installed condition, a low water surface area of ​​the TLP is desirable to limit the effects of wave loading, resulting in low motions and accelerations. Summary of the Invention [Problem to be solved by the invention]

[0004] However, during transportation and installation at the desired offshore wind farm site, the TLP system still lacks tendon restoring and stabilizing capabilities. Although in free draft the TLP system is stable, its seakeeping performance is limited and the dynamic range of stability is insufficient for safe transportation. During the subsequent installation (or removal, e.g. when the TLP system is decommissioned) phase, the TLP system is submerged and in the remaining limited water surface area, the TLP system becomes unstable due to its high center of gravity (mainly due to the wind turbines standing tall on top of the wind turbine tower) and the large overturning moments from wind drag loads.

[0005] Currently, TLPs are usually transported to the site on the deck of a large crane vessel or by adding external (temporary) buoyancy to the TIF legs to stabilize them for towing by tugboats.

[0006] Furthermore, currently TLPs are usually brought up to their installation draft by placing temporary water ballast inside them, however this requires a ballasting system for each individual TLP, making the construction of such TLPs very complex, thus increasing costs, and requiring the provision of mitigation measures to prevent a corrosive environment inside the TLP.

[0007] In view of the above, it is an object of the present invention to provide a floating structure intended for the transportation and installation of floating tension leg platforms, by means of which such transportation and installation can be carried out in a safe and reliable manner without the need for (any or excessive) additional systems and / or construction means for the TLP. [Means for solving the problem]

[0008] Thus, according to the present invention, such a floating structure comprises a controllable ballast tank for varying its buoyancy and engagement means for engaging with the legs of the TLP and maintaining it at the required draft during transportation and installation, the floating structure comprising a number of floating structure parts intended to be located horizontally adjacent to each leg of the TLP, the floating structure parts comprising engagement means for engaging with engageable means provided on said legs of the TLP, whereby, in the working attitude of the floating structure in which said floating structure parts are located horizontally alongside the legs of the TLP, the engagement means are able to load the engaged means with a downward force opposing the upward buoyancy of the TLP, the engagement means being further arranged so that they can engage with the engaged means in the above-mentioned manner even when at least a part of the legs of the TLP are located at a height above sea level.

[0009] The floating structure according to the invention offers the opportunity to transport and install the TLP in a safe and reliable (stable) manner. When the TLP (or TLP system, e.g. a TLP with a wind turbine) is in a floating position with at least part of its legs located at a height above the sea level, the floating structure with the respective floating structure parts (provided with engaging means) can be placed alongside the legs of the TLP, so that the engagement between the engaging means on the floating structure and the engaged means on the TLP starts when the floating structure is ballasted. It is therefore not necessary to provide a system by which the floating structure can be placed on the TLP (e.g. the TLP needs to be brought below the sea level). According to the invention, the floating structure can be engaged to the TLP in the desired way while the TLP is in its normal floating position (position due to buoyancy and weight without tendons).

[0010] During transportation and installation, the floating structure with its large overall length and limited surface area keeps the TLP in a stable position with good seakeeping properties (e.g. during transportation with its legs fully submerged). At the installation site (offshore wind farm), the floating structure is further lowered to the desired depth to allow the connection of mooring lines (tendons), after which the floating structure is de-ballasted and the TLP is stably moored by the mooring lines under tension due to its buoyancy.

[0011] The engaged means on the leg of the TLP may comprise fixed means, i.e. separate means provided on said leg, but it is also conceivable that a part of the leg which is part of its normal configuration (e.g. its upper surface) may define or act as the engaged means (so that the configuration of the TLP is not altered in that case).

[0012] For safety reasons, the engaging means may be provided with a member for improving adhesion between the engaging means and the engaged means, or with a member of soft material. Such a member for improving adhesion may include, for example, a vacuum pad or a magnet.

[0013] Alternatively or additionally, the floating structure may be provided with a locking member, such as a locking pin, for locking the engaging means to the engaged means. Such a locking member may cooperate with a dedicated member or part of the TLP.

[0014] To ensure optimal cooperation between the engaging means and the engaged means, at the intended interface with the engaged means, the engaging means may have a complementary shape to the engaged means, for example if the legs of the TLP are in the shape of a rounded tube (the upper surface of which defines the engaged means), the engaging means may have a similar rounded shape.

[0015] To further help avoid localized stresses between the engaging means and the engaged means, the underside of the engaging means may be provided with a material that is softer than the remainder of the engaging means, such as wood, plastic or rubber.

[0016] In a preferred embodiment, the engaging means comprises a protruding cam embodied and positioned to engage the engaged means.

[0017] When the cam is at a static position relative to the floating structure, the constructional complexity of the floating structure is minimized.

[0018] However, in alternative embodiments of the floating structure, the cam is movable relative to the floating structure, either vertically linearly or by horizontal and vertical rotation, preferably with a controlled or damped movement. Such a cam movement may be used in particular (but not exclusively) to control the manner in which the cam and the engaged means cooperate during coupling and decoupling of the floating structure to and from the TLP. Among other things, the controlled movement can compensate for relative movements between the floating structure (e.g. due to waves) and the TLP (which may for example be in a stationary position in a moored state) and prevent violent impacts between them. The cam movement can also be used to avoid collisions between the floating structure and the TLP in situations described at a later stage, in particular during decoupling between them.

[0019] In exceptional cases, for example to reduce drag during transport, vertical movement of the cam may also be used to lift the TLP (at least partially) out of the water.

[0020] As an alternative to the use of a protruding cam, the engaging means may comprise a recess in the floating body structural component (capable of receiving the engaged means of the TLP).

[0021] In a very particular embodiment, the floating structure according to the invention is provided with a release mechanism comprising a releasable locking member for releasing the floating structure from the TLP in a controlled manner.

[0022] For example, the releasable locking member may comprise a rope, cable, or piston-cylinder assembly having a first end releasably attached to one of the floating structure and the TLP and a second end releasably attached to the other of the floating structure and the TLP, and capable of controlling the distance between the first and second ends.

[0023] A controlled release of the Floating Structure from the TLP avoids any dangerous impact during this time. Without such a releasable fastening, the Floating Structure during de-ballasting, after being released from the TLP (e.g. when the TLP is installed and maintained at a desired position and depth by tendons), would start to move gradually (upwards) away from the TLP due to a gradual increase in its buoyancy. During the initial phase of such movement, since the distance between the stationary TLP and the upwardly moving Floating Structure is still moderate and the buoyancy of the Floating Structure is still limited, any uncontrolled movement of the Floating Structure (e.g. due to waves or other external factors) could result in an impact between the TLP and the Floating Structure, resulting in a significant risk of damage or a dangerous situation.

[0024] However, when using the controlled release mechanism according to the invention, the floating structure may already be (partially) de-ballasted, while the TLP remains (engaged) connected to the floating structure by the releasable locking members. Only when the floating structure is sufficiently de-ballasted (resulting in a large buoyancy), the locking members can be released or controlled to increase the distance between the first end and the second end, so that the floating structure moves upwards and away from the TLP. When this movement starts, since the floating structure already has a large buoyancy, it is very unlikely (or even impossible) for waves or other external influences to cause the floating structure to collide with the TLP.

[0025] The distance between the ends of the locking members can be increased by winding a cable or rope or by lengthening a piston-cylinder assembly.

[0026] When the distance between the floating structure and the TLP has increased sufficiently, the locking member may be completely detached from at least one of the TLP or the floating structure (e.g. from the TLP so that the locking member remains connected to the floating structure and can be used again on another TLP).

[0027] Other measures may be provided to avoid collisions between the TLP and the floating structure. For example, the floating structure may be provided with means to ensure rapid release between the floating structure and the TLP, such as one or more dump valves for rapid discharge of ballast water. Such rapid discharge of ballast water results in a sudden and rapid increase in the buoyancy of the floating structure, which also helps to ensure that the floating structure moves away from (and not towards) the TLP.

[0028] Architecturally, the floating structure according to the invention may comprise a number of spaced apart columnar ballast tanks connected by connecting beams, the engagement means being provided on said ballast tanks.

[0029] This results in a very stable floating structure, not only during transportation and installation of the TLP, but also when floating alone. The stability is mainly due to the distance between the ballast tanks, which may each have a fairly limited surface area, but the distance and surface area can be designed to obtain good seakeeping characteristics.

[0030] In one embodiment, the bottom of each ballast tank is provided with feet that have a larger horizontal cross section than the rest of the ballast tank, which allows the floating structure to rest stably on the seabed (e.g. in a shallow harbour) when fully ballasted and when connected to the TLP (so that the TLP can be assembled with, for example, a wind turbine while remaining in a very stable position). The use of the feet also allows the floating structure to operate in shallow waters.

[0031] The feet may or may not include ballast chambers, and such feet may provide additional dynamic damping to the floating structure.

[0032] In a particular embodiment, the floating structure is intended for use with a three-legged TLP and comprises three ballast tanks arranged in a triangle (as viewed from above), with a first ballast tank at the apex of the triangle and two ballast tanks at adjacent corners of the triangle, each connected to the first ballast tank by a connecting beam.

[0033] The triangular open section allows the floating structure to sail around the midpoint of the TLP (e.g. the tower of a wind turbine) and float such that the ballast tanks contact towards the three legs of the TLP. Then, each leg (e.g. the tip) contacts the floating structure (e.g. the sidewall of a columnar ballast tank) and the engaging means (e.g. the cam) on the ballast tank is placed on the engaged means (e.g. the top surface) of the leg.

[0034] It is contemplated that the ballast tanks and tie beams may be decoupled from one another to allow for efficient transport and storage.

[0035] A floating structure according to the invention may include other features and provide other advantages, which are briefly described below in a non-limiting manner.

[0036] The floating structure basically adds a temporary tool to the TLP and gives it semi-submersible characteristics in terms of good seakeeping, stability and improved maneuverability. The floating structure with the engagement means can sail on the legs of the TLP and push the TLP down.

[0037] Widely spaced columnar ballast tanks, similar to semi-submersibles, provide greater stability to the entire system. This means that by concentrating buoyancy within the ballast tanks, the surface area is minimized. Minimizing the surface area helps reduce wave reaction. Furthermore, such columnar ballast tanks can provide excellent space for ballast water and associated pumps / equipment.

[0038] Using engagement means such as cams, the floating structure can be ballasted and lowered based on the effective buoyancy of the TLP to couple with the TLP, e.g. the TIFs on its legs. Here, the ballasting system of the floating structure is used to bring / lower the whole system (floating structure and TLP) to the installation depth, after which the disconnection of the floating structure from the TLP is essentially done by de-ballasting the floating structure. The floating structure is safely released from the TLP either by translation, rotation and / or vertical disconnection.

[0039] The floating structure can furthermore be used for the transport or storage of materials and equipment. For example, if tendon installation from the floating structure is required, the tendons and installation equipment can be mounted on the floating structure. However, the floating structure may also comprise a deck to accommodate other installation aids such as power packs, accommodations, small parts, small cranes, walkways, (drums with) tendons, etc. As mentioned before, additional equipment can be equipped on the floating structure for controlled disconnection after connection.

[0040] The floating structure design can be scalable to larger TLPs by substituting other sized beams for the connecting beams, updating ballast and pump volumes, changing column diameters and heights, etc.

[0041] Finally, while the transportation and stationary maintenance of the floating structure is generally performed by tugboats (in line with normal offshore installation methods and for low maintenance costs), it is also possible to equip the floating structure with DP (stationary positioning) means.

[0042] The invention will now be described with reference to the following drawings: [Brief description of the drawings]

[0043] [Figure 1] FIG. 2 is a perspective view of an embodiment of a floating structure coupled to a TLP. [Diagram 2] FIG. 13 is a perspective view of an embodiment of a floating structure coupled to a TLP with a wind turbine. [Diagram 3] FIG. 13 is a schematic diagram showing the use of a support member between the floating structure and the TLP. [Figure 4] 13A and 13B show the use of a locking member. [Figure 5a] 1 shows three different embodiments of the cam. [Figure 5b] 1 shows three different embodiments of the cam. [Figure 5c] 1 shows three different embodiments of the cam. [Figure 6] FIG. 2 shows a schematic diagram of a vertically movable cam. [Figure 7] 1A-1D show schematic diagrams of three different embodiments with rotatable cams. [Figure 8] 13A-13C show an embodiment having a releasable locking member. [Figure 9] FIG. 1 illustrates the use of a dump valve. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] Figures 1 and 2 show two different views of an embodiment of a floating structure 1 according to the invention (hereinafter referred to as TIF - Transportation and Installation Frame -), which is intended for the transportation and installation of a floating Tension Leg Platform (TLP) 2 (the tower is only shown in Figure 2) having a number of legs 3 radiating from a central point, such as the tower (or central column) 4 of a wind turbine 5.

[0045] The TIF1 comprises a number (here three) of spaced apart, controllable columnar ballast tanks 6, 6' for varying its buoyancy. The ballast tanks 6, 6' are arranged in a triangle (as viewed from above) with a first ballast tank 6' at the top of the triangle and two ballast tanks 6 at adjacent corners of the triangle. Each ballast tank 6 is connected only to the first ballast tank 6' by a respective horizontal tie beam 7, and not to each other. This leaves open spaces between the ballast tanks 6 and between the tie beams 7 for receiving the TLP2.

[0046] At the bottom of each ballast tank 6,6' there is provided a foot 8 having a larger horizontal cross section than the remainder of the ballast tank 6,6'.

[0047] In the embodiment shown, the TIF 1 is intended for use with a three-legged TLP 2 and therefore includes three ballast tanks 6, 6'. For use with a TLP having a different number of legs 3, the TIF may include a different corresponding number of ballast tanks. The number of connecting beams 7 may vary as well.

[0048] Each ballast tank 6, 6' is provided with an engagement means, which in the illustrated embodiment is embodied as a cam 9 for engaging with the upper surface (the upper surface functioning as the engagement means) of a corresponding one of the legs 3 of the TLP 2 in the TIF region.

[0049] In other embodiments not shown, the cam may engage other parts of the leg 3 of the TLP 2. As an alternative to the cam 9, a recess (schematically shown in dashed lines at 10 in Figure 1) may be provided for receiving (part of) the leg 3.

[0050] The cam 9 is used to maintain the TLP 2 at the required draft during transportation and installation procedures as will be explained at a later stage.

[0051] As can be seen, the TIF1 thus comprises parts (in particular ballast tanks 6, 6') intended to be positioned horizontally adjacent to each leg 3 of the TLP2, and these parts are provided with cams 9 for engaging the legs 3 of the TLP2, such that in the working position of the TIF1, in which said parts are positioned horizontally alongside the legs 3 of the TLP2, the cams 9 can load the legs 3 with a downward force that counteracts the upward buoyant force of the TLP2.

[0052] The cam 9 is further positioned such that it can engage the leg 3 of the TLP 2 in the manner described above even when the leg 3 is at least partially located at an elevation above sea level.

[0053] Figure 2 further shows that the TIF 1 may comprise a structure 11 for carrying objects 12 such as materials and equipment. The ballast tanks 6, 6' may also support additional equipment or other objects, such as for example a crane 13 (only shown in Figure 2).

[0054] As shown in figure 3, the cam 9 can be provided with a member 14 for example to improve adhesion between the cam 9 and the leg 3, in which case such member 14 can comprise for example a vacuum pad or a magnet. Alternatively, said member 14 can also be made of a soft material (for example wood, plastic or rubber) to avoid high local stresses.

[0055] Referring to FIG. 4, a locking member 15 such as a locking pin for locking the engaging means (cam 9) to the engaged means (leg 3) may be provided.

[0056] At the intended interface with the engaged means (leg 3), the engaging means (cam 9) preferably has a complementary shape to the engaged means in order to ensure optimal transmission of forces between them, as shown diagrammatically in three different embodiments in Figure 5. In Figure 5a, the upper surface of the leg 3 is flat, as is the lower end of the cam 9. In Figure 5b, both are rounded in a similar manner, and in Figure 5c, there are two spaced apart cams 9 whose lower ends are located at different heights to match the sloping upper surface of the leg 3.

[0057] In the above-mentioned embodiment, the cam 9 has a stationary position relative to the TIF 1 (here relative to the ballast tanks 6, 6'). However, alternatively, the cam 9 may be movable relative to the TIF 1 linearly in the vertical direction V (Figure 6) to a raised position 9' out of engagement with the legs 3, or by a vertical upward rotation R (Figure 7a), or by a vertical inward rotation R, for example into a receiving opening (not shown) of the ballast tanks 6, 6' (Figure 7b), or by a horizontal rotation R (Figure 7c), respectively, to a new position 9' out of engagement with the legs 3.

[0058] In particular, the movement capability of the cam 9 allows for rapid and sufficient decoupling between the TIF1 and the TLP2, especially during the decoupling process.

[0059] The cam 9 may be movable with controlled or damped movement (particularly vertically), for example to compensate for relative movement between the TLP2 and the TIF1.

[0060] The TLP2 is typically fabricated at a shipyard and then transported to a marshalling yard where it is offloaded and anchored in or near a shallow water port. The TIF1 with its Cam9 floats over the anchored TLP and moves the TLP quayside or to a prepared seabed where it can be delivered by ballasting to the seabed or an artificial support structure.

[0061] The unique design of the foot 8 (enlarged horizontal section) allows the TIF to operate in shallow waters, making optimal use of space in and near the coastal areas.

[0062] The triangular or V-shaped open space of the TIF1 defined by the ballast tanks 6, 6' and the connecting beam 7 allows the TIF1 to sail around the central column of the TLP (e.g. tower 4), float alongside the legs 3 and float the cams 9 above the legs 3. Steering of the TIF1 can be achieved by its own propulsion means or by the use of tugs.

[0063] The tip of each leg 3 contacts the corresponding side wall of the cylindrical ballast tank 6,6' thus ensuring the correct relative position between the TIF1 and the TLP2.

[0064] The TIF1 is then ballasted by filling the ballast tanks 6, 6' and the cam 9 is lowered until it engages the legs 3 of the TLP2. By controlling the ballasting (i.e. negative buoyancy) of the TIF1, one can control the force with which the cam 9 loads the legs 3 of the TLP2 downwards (opposite the buoyancy of the TLP) and thus the draft of the entire TIF / TLP assembly. Additional connection means such as cables or mechanical connections may be used between the TIF1 and TLP2 for added safety during towing / transport.

[0065] During transport, TLP2 and TIF1 are connected and therefore considered as a single floating unit. The main function of TIF1 is to provide additional stability to TLP2, optionally equipped with wind turbines 5, for optimal seaworthiness.

[0066] Typically, during such transportation, the TLP legs 3 are fully submerged. Typically, the central column of the TLP (tower 4) and the three columnar ballast tanks 6, 6' of the TIF1 are partially submerged, providing surface area to all ballast tanks 6, 6'. The surface area and its distribution are designed such that the natural periods of heave and pitch / roll are out of sync with the prevailing wind and swell wave periods. As a result, the complete assembly (TIF1, TLP2, and optionally wind turbine 5) has sufficient stability.

[0067] As previously mentioned, propulsion for the TIF 1 can be provided externally by tugboats or by propellers mounted on the TIF. Multiple tugboats may be required for speed and heading control.

[0068] The purpose of the propulsion is to transport the entire assembly to the installation site in moderate sea conditions. Important design criteria are the maximum acceleration to which the wind turbine 5 will be subjected, and the towing speed, the latter related to the overall drag. Drag resistance is reduced by the rounded vertical cylindrical ballast tanks 6, 6' and the smoothly shaped feet 8. It is also designed to be seaworthy, able to "stand" unexpected adverse weather conditions and stay within the wind turbine motion limits, providing robustness to the TIF1 operation scheme.

[0069] It is conceivable to configure the TIF1 to include a lifting mechanism (see crane 13 in Figure 2) that can transport the TLP2 once it has been lifted (fully or partially) out of the water, thereby reducing the drag of the entire system.

[0070] The ballast water in the ballast tanks 6, 6' is used to increase the draft of the entire system upon arrival at the installation site. Ballasting can be done on arrival at the site or, under certain weather conditions, can be started during transport. TIF1 is ballasted slightly deeper than the installation depth target of TLP2. This allows for the installation and attachment of the tendons. The length of the tendons will vary depending on the location and position. An extension or installation wire is connected to the top of the tendon to guide it to the tendon connection at the leg TIF of TLP2.

[0071] The tendons are either pre-laid (pre-laid mooring system) or installed starting from the TIF1, in which case the tendon materials and the necessary installation equipment are installed on the deck of the TIF (see structure 11 in Figure 2). A large "deck" space is an important feature of this TIF1, allowing safe passage, installations and storage of installations 12 and small parts.

[0072] TIF1 provides great stability to the whole system, which is essential when connecting the tendons. It minimizes the relative movement between the pre-installed tendon and the tendon connection at leg 3 of TLP2. In theory, this improves the weather window of the connection and safety during work. If the tendons are installed starting from TIF1, the relative movement between the bottom of the tendon and the anchor point is minimized.

[0073] After connection, TIF1 begins de-ballasting and slowly moves upwards, placing the tendon in tension. This continues until the tendon is loaded to the target pre-tension level. At that point, TIF1 with cam 9 begins to separate from leg 3 of TLP2. TIF1 continues de-ballasting at a carefully designed pace so that the separation between TIF1 and TLP2 remains safe; or more accurately, the separation generally increases fast enough so that the probability of re-contact is low.

[0074] During the first stage of separation between TIF1 and TLP2, TIF1 is still moderately buoyant and there is a risk that external influences (e.g. waves) could cause TIF1 to collide with TLP2 (TLP remains stationary due to the tendons).

[0075] Therefore, for reliability, robustness and safety, further facilities may be added to TIF1 to release TLP2 from TIF1 in a controlled manner. This may be any release mechanism with a releasable locking member. Such a mechanism may also be used to cause horizontal decoupling. The application of soft contact materials to TIF1 may also be an option.

[0076] FIG. 8 shows diagrammatically one embodiment of such a release mechanism, in which a releasable locking member 16 (e.g. a rope, cable or piston-cylinder assembly) is provided, the first end 16′ of which is releasably attached to the (ballast tanks 6, 6′ of the) TIF1 and the second end 16″ of which is attached to the (leg 3 of) the TLP2 (which is moored by a tendon 17). The locking member 16 initially keeps the TIF1 in firm contact with the TLP2 until the TIF1 has been sufficiently de-ballasted to obtain a significant excess buoyancy. The locking member 16 may then be released (e.g. at the second end 16″) and the TIF1 moves upwards at a faster pace without the risk of collision with the TLP2. It is also possible for the locking member 16 to remain connected to both TIF1 and TLP for a while and for example use a winch (schematically indicated at 18 in FIG. 8 ) to increase its length (between ends 16' and 16") so that TIF1 moves steadily upwards and away from TLP2. Alternatively, part 18 may be the piston housing of a piston-cylinder assembly, in which case 16 represents the piston rod.

[0077] If the separation between TIF1 and TLP2 in the vertical and horizontal directions is sufficient, TIF1 can be moved away from TLP2. Also, the cam 9 can be moved away to a safe position. When TIF1 is out of the installation location, the installation of TLP2 is completed.

[0078] As a further aid to the safe and rapid release of the TIF1 from the TLP2, additional means may be provided, such as one or more dump valves 19 for rapidly draining ballast water from the ballast tanks 6, 6' of the TIF1.

[0079] After TLP2 is installed, TIF1 can be towed back to port. Prior to this voyage, TIF1 can have its draft optimized (by ballasting or de-ballasting) for the expected sea and wind conditions. As a result, TIF1 has sufficient stability to be towed back in moderate and moderately harsh conditions.

[0080] Upon reaching its final destination, the draft can be reduced, allowing TIF1 to be moved to shallower areas for further work or storage. Special feet 8 also allow a shallow draft, allowing TIF1 to be placed on the (flattened) seabed.

[0081] The invention is not limited to the described embodiments, but may vary widely within the scope of the invention as defined by the appended claims.

[0082] [Additional note 1] A floating structure (1) for the transportation and installation of a floating tension leg platform (TLP) (2) having a plurality of legs (3) radiating from a central point (4), comprising: The floating structure comprises: a controllable ballast tank (6, 6') for varying the buoyancy of said ballast tank; Engagement means (9) for engaging the legs (3) of the TLP and maintaining the TLP at a required draft during transportation and installation; Equipped with the floating structure comprises a plurality of floating structure components for positioning horizontally adjacent to each leg (3) of the TLP; The floating structure component is provided with the engaging means (9) for engaging with the engaged means provided on the leg (3) of the TLP (2), so that in an operating attitude of the floating structure in which the floating structure component is horizontally positioned alongside the leg of the TLP, the engaging means can apply a load to the engaged means with a downward force that opposes the upward buoyancy of the TLP, The engaging means (9) is further arranged such that it can engage with the engaged means in the aforementioned manner even when at least a portion of the leg (3) of the TLP is located at an elevation above sea level. [Additional note 2] The floating structure according to claim 1, wherein the engaging means (9) is provided with a member (14) for improving adhesion between the engaging means and the engaged means, or a member made of a soft material. [Additional note 3] 3. The floating structure according to claim 2, wherein the member (14) includes a vacuum pad or a magnet. [Additional note 4] The floating structure according to any one of claims 1 to 3, further comprising a locking member (15) such as a locking pin for locking the engaging means (9) to the engaged means. [Additional note 5] 5. The floating structure according to any one of claims 1 to 4, wherein the engaging means (9) has a shape complementary to the engaged means at a planned boundary surface with the engaged means. [Additional note 6] The floating structure according to any one of appended items 1 to 5, wherein the engagement means (9) is arranged to engage with an upper surface of the leg portion (3) of the TLP (2). [Additional note 7] The floating structure according to any one of claims 1 to 6, wherein the engaging means (9) comprises a protruding cam arranged to engage with the engaged means. [Additional note 8] 8. The floating structure according to claim 7, wherein the cam (9) has a stationary attitude relative to the floating structure (1). [Additional note 9] 8. The floating structure according to claim 7, wherein the cam (9) is movable relative to the floating structure (1) linearly in a vertical direction (V) or by rotation (R) in a horizontal or vertical direction. [Additional Note 10] 10. The floating structure according to claim 9, wherein the cam (9) is movable with controlled or damped movement. [Additional Note 11] The floating structure according to any one of claims 1 to 6, wherein the engagement means (9) comprises a recess (10) in the floating structure component. [Additional Note 12] 12. The floating structure according to any one of claims 1 to 11, wherein a release mechanism is provided comprising a releasable locking member (16) for releasing the floating structure (1) from the TLP (2) in a controlled manner. [Additional Note 13] The floating structure described in claim 12, wherein the releasable locking member (16) comprises a rope, cable, or a piston-cylinder assembly, a first end (16') of the locking member being releasably attached to one of the floating structure and the TLP, and a second end (16") of the locking member being releasably attached to the other of the floating structure and the TLP, and wherein the distance between the first end and the second end can be controlled. [Additional Note 14] 14. The floating structure according to any one of claims 1 to 13, wherein means are provided to ensure rapid release between the floating structure (1) and the TLP (2), such as one or more dump valves (19) for rapid discharge of ballast water. [Additional Note 15] 15. The floating structure according to any one of appended claims 1 to 14, wherein the floating structure comprises a number of spaced apart columnar ballast tanks (6, 6') connected by a connecting beam (7), and the engagement means (9) is provided in the ballast tanks. [Additional Note 16] The floating structure according to claim 15, wherein a foot (8) having a horizontal cross section larger than that of the remaining part of the ballast tank is provided at the bottom of each of the ballast tanks (6, 6'). [Additional Note 17] 17. The floating structure according to claim 15 or 16, intended for use with a three-legged TLP (2), comprising three ballast tanks (6, 6') arranged in a triangular shape, with a first ballast tank (6') at the apex of the triangle and two ballast tanks (6) at adjacent corners of the triangle, each of the two ballast tanks being connected to the first ballast tank by a connecting beam (7). [Additional Note 18] 18. The floating structure according to any one of claims 15 to 17, wherein the ballast tanks (6, 6') and the connecting beam (7) are detachable from each other. [Explanation of symbols]

[0083] 1 floating structure, 2 floating tension leg platform, 3 legs, 4 tower, 5 wind turbine, 6 ballast tank, 6' ballast tank, 7 connecting beam, 8 foot, 9 cam, 10 recess, 11 structure, 12 object, equipment, 13 crane, 14 member, 15 locking member, 16 releasable locking member, 16' first end, 16" second end, 17 tendon, 18 winch, 19 dump valve, R rotation, V vertical

Claims

1. A floating structure (1) for the transportation and installation of a floating tension leg platform (TLP) (2) having a plurality of legs (3) radially extending from a central point (4), comprising: The floating structure comprises: a controllable ballast tank (6, 6') for varying the buoyancy of said ballast tank; Engagement means (9) for engaging the legs (3) of the TLP and for maintaining the TLP at a required draft during transportation and installation; Equipped with the floating structure comprises a plurality of floating structure components for positioning horizontally adjacent to each leg (3) of the TLP; the floating structure component comprises the engaging means (9) for engaging with the engaged means provided on the leg (3) of the TLP (2), whereby, in an operating attitude of the floating structure in which the floating structure component is positioned horizontally alongside the leg of the TLP, the engaging means can load the engaged means with a downward force that opposes the upward buoyancy of the TLP; The floating structure, further comprising: the engaging means (9) arranged such that it can engage with the engaged means in the aforementioned manner even when at least a portion of the leg (3) of the TLP is located at an elevation above sea level.

2. 2. The floating structure according to claim 1, wherein the engaging means (9) is provided with a member (14) for improving adhesion between the engaging means and the engaged means, or a member made of a soft material.

3. The floating structure of claim 2, wherein the members (14) include vacuum pads and magnets.

4. The floating structure according to claim 1, further comprising a locking member (15) such as a locking pin for locking the engaging means (9) to the engaged means.

5. The floating structure according to claim 1, wherein the engaging means (9) has a shape complementary to the engaged means at a planned interface with the engaged means.

6. 2. The floating structure according to claim 1, wherein the engagement means (9) are arranged to engage upper surfaces of the legs (3) of the TLPs (2).

7. 2. The floating structure according to claim 1, wherein the engaging means (9) comprises a protruding cam embodied and arranged to engage the engaged means.

8. 8. The floating structure according to claim 7, wherein the cam (9) has a stationary attitude relative to the floating structure (1).

9. 8. The floating structure according to claim 7, wherein the cam (9) is movable relative to the floating structure (1) linearly in a vertical direction (V) or by a horizontal or vertical rotation (R).

10. 10. The floating structure according to claim 9, wherein the cam (9) is movable with controlled or damped movement.

11. 2. The floating body structure according to claim 1, wherein the engagement means (9) comprises a recess (10) in the floating body structure part.

12. 2. The floating structure according to claim 1, wherein a release mechanism is provided comprising a releasable locking member (16) for releasing the floating structure (1) from the TLP (2) in a controlled manner.

13. 13. The floating structure of claim 12, wherein the releasable locking member (16) comprises a rope, cable, or a piston-cylinder assembly, a first end (16') of the locking member releasably attached to one of the floating structure and the TLP, and a second end (16") of the locking member releasably attached to the other of the floating structure and the TLP, and wherein a distance between the first and second ends of the locking member can be controlled.

14. 2. The floating structure according to claim 1, wherein means are provided to ensure rapid release between the floating structure (1) and the TLP (2), such as one or more dump valves (19) for rapid discharge of ballast water.

15. 2. The floating structure according to claim 1, comprising a number of spaced apart columnar ballast tanks (6, 6') connected by connecting beams (7), and the engagement means (9) are provided on the ballast tanks.

16. 16. A floating structure according to claim 15, wherein the bottom of each of the ballast tanks (6, 6') is provided with a foot (8) having a larger horizontal cross section than the remainder of the ballast tank.

17. 16. A floating structure as claimed in claim 15, intended for use with a three-legged TLP (2), comprising three ballast tanks (6, 6') arranged in a triangular shape, with a first ballast tank (6') at the apex of the triangle and two ballast tanks (6) at adjacent corners of the triangle, each of the two ballast tanks being connected to the first ballast tank by a connecting beam (7).

18. 16. The floating structure according to claim 15, wherein the ballast tanks (6, 6') and the connecting beam (7) are separable from each other.

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