A mooring assembly

Abstract

A mooring assembly (11; 11') for installation on a marine structure (4, 5, 6), above or below a water surface (7), comprises a main frame (101; 101') having a connecting portion (107) for connection to the marine structure. The assembly comprises a stopper device (112; 112'; 112") which is arranged in the main frame (101; 101'), and an elongate stopper member (104) which may be connected to a mooring chain or line. The stopper device (112; 112'; 112") is configured for interlocking with the elongate stopper member (104). The stopper device (112) comprises a housing (122) with a plurality of ratchet pawls (124) arranged in a circular chamber (138), wherein the pawls (124) are movably interconnected via a ring member (125) and biased towards each other by an elastic member (123), and each pawl comprises one or more ratchet teeth (133) for interaction with corresponding teeth (118) on the elongate stopper member (104).

Description

[0001] A MOORING ASSEMBLY

[0002] Technical field of the invention

[0003] This invention concerns mooring systems for marine structures such as floating platforms and vessels and structures that are designed for installation on a seabed or other underwater locations. More specifically, the invention concerns a mooring assembly as set out by the preamble of claim 1.

[0004] Background of the invention

[0005] Structures for supporting plants and equipment above a body water comprise structures that rely on buoyancy and float in the body of water, and structures that are resting on the bottom below the body of water. Examples of buoyant support structures are tension-leg platforms (TLPs), spar platforms, and semi-submersible platforms. Examples of support structures that are configured to be installed on — and in some cases penetrate — the seabed, are gravity-based foundations, jacket foundations, and monopiles. All of the above structure types have traditionally been used for supporting plants and equipment for producing and processing hydrocarbons from reservoirs in offshore, subterranean reservoirs. In more recent years, these structure types have increasingly found use also within the wind power industry.

[0006] Offshore regions of varying depths off coastlines offer tremendous potential as wind power resources. In deep-water regions (e.g., depths of approximately 120 meters or more), floating marine structures, commonly referred to as “platforms,” are typically used for exploration activities and the mounting of wind turbines. In shallower regions (e.g., depths of approximately 50 meters or less), fixed structures that are mounted to the sea floor are commonly used to mount wind turbines and provide platforms for various activities. For platforms installed in either depth or depths in between, determining how to reduce movement of such platforms to support wind turbines, can be challenging. In an open ocean, winds, waves, and currents often act simultaneously and exert forces on the marine platforms causing the platforms to move.

[0007] The present invention concerns technologies for minimizing movement of a fixed marine structure, such as an offshore wind turbine. Using the technologies described herein, a wind turbine may be mounted on a fixed marine platform that is constructed and mounted on — or partly embedded in — the seabed in water of any depth (e.g., shallow water (e.g., depth of less than 50 meters), intermediate depth water (e.g., depth of greater than 50 meters and less than 120 meters), and deep water (depth of greater than 120 meters)). In various examples, a wind turbine may be mounted on a fully restrained platform (FRP) monopile. A monopile is a pile structure that is driven into the seafloor and that may form a portion of or otherwise support a fixed marine platform, such as an FRP. As used herein, the term FRP refers to a platform that has motions restrained in 6 degrees -of-freedom (DOFs) and the term FRP-monopile refers to an FRP that includes a monopile.

[0008] For purposes of explanation, the main structural component of a platform can be viewed as a rigid body. Its motions may be characterized by and measured in 6 degrees-of- freedom (DOFs) including 3 translational DOFs (surge, sway, and heave) and 3 rotational DOFs (roll, pitch, and yaw). Environmental loads may apply force to the platform in one or more DOFs. Some of these loads are dynamic in nature, such as loads due to water waves, while others may be largely static, such as loads due to ocean current induced drag.

[0009] An example platform design philosophy is that in shallow waters, the environmental loads are mainly resisted by the lateral stiffness of the platform, which is designed to be “fixed.” One such example is the jacket platform which is a lattice structure with its legs extending into the earth. In deeper waters, however, the amount of material required for a fixed platform may be uneconomical and therefore floating platforms may be used. Platform concepts may be configured with a variety of technologies to resist and / or allow motion operating at some or all of the 6 DOFs’. For example, a fixed marine platform using a bottom-mounted driven pile structure may be configured to resist motion in all of the 6 DOFs; a tension-leg platform (TLP) may allow (at least to some extent) surge, sway, and yaw motions; while a semisubmersible platform may allow (at least to some extent) motion in all of the 6 DOFs.

[0010] In current wind engineering practice, fixed ocean platforms may be used for shallow water regions where the water depth is less than 50-60 meters and where wind, wave, and current forces may be relatively less than in deep water regions. However, fixed ocean platforms (e.g., FRP-monopiles) may also be used in deeper water regions (e.g., up to 200 meters) that are subject to greater wind, wave, and current forces.

[0011] For a wind turbine to function effectively, it is desirable that its host structure has as little movement as possible. A wind turbine is supported by a platform that attempts to minimize motions in all of its 6 DOFs may more effectively generate power than turbines mounted on platforms that do not restrain motion in all 6 DOFs. In the prior art, no known fixed platforms that possess such features have been effectively implemented in intermediate-depth waters to host wind turbines. As described herein, a fixed marine structure is disclosed that reduces and / or minimizes motions in shallow and intermediate-depth water (e.g., depths of up to 120 meters or more in mild environments). The disclosed structures may host one or more wind turbines and associated structures and equipment.

[0012] An offshore wind turbine is a wind turbine mounted on an offshore platform. In various disclosed examples, the offshore platform may be an FRP-monopile. Examples of FRP- monopiles can be found, for example, in U.S. Patent Application No. 17 / 249,676, filed 9 March 2021, and titled “Minimizing Movements of Offshore Wind Turbines,” the contents of which are herein incorporated by reference in their entirety and for all purposes.

[0013] An offshore wind turbine mounted on an FRP-monopile generally includes six main components: (1) a single pile (“monopile”) driven into the seafloor, (2) a wind tower to which a wind turbine is mounted, (3) a transition piece mounted to the monopile and to which the wind tower is mounted, (4) one or more anchors affixed to the seafloor, (5) one or more mooring lines affixed to the anchors and to one or both of the transition piece and the monopile, and (6) the wind turbine, which may include a nacelle (e.g., housing), a rotor hub, blades, and various other components. In addition to a wind turbine, other structures and equipment can also be mounted on a platform such as the disclosed FRP-monopile. The mooring lines may be connected to one or more connection components configured at the transition piece and / or monopile that may facilitate the application and adjustment of tension on the mooring lines. Using the techniques described herein, the motions in all of the 6 DOFs of an offshore wind turbine mounted on a fixed marine structure may be reduced and / or restrained. The motions referred to herein are those caused by various types of environmental loading. The external forces causing the motions include those from waves and ocean currents on the structure, from the moorings along with any part of the turbine and / or structure in contact with water, and from winds on any part of the structure above the sea surface.

[0014] Figure 1 illustrates an exemplary wind turbine system 1 supported by an FRP-monopile structure. The wind turbine system 1 may include a wind turbine 2 that may include a housing, a rotor hub, blades, and various other components associated with generating and / or collecting energy based on the rotation of one or more blades caused by wind forces. The wind turbine 2 may be mounted on, affixed to, or otherwise supported by a wind tower 3. The wind tower 3 may be mounted on, affixed to, or otherwise supported by a transition piece 4 that may in turn be mounted on, affixed to, or otherwise supported by a monopile 5. Alternatively, the wind tower 3 may be mounted on the monopile 5. Together the wind tower 3, the transition piece 4, and the monopile 5 may form an FRP-monopile 6 that supports the wind turbine 2. Each of the wind tower 3, the transition piece 4, and the monopile 5 may be constructed of one or more materials of any type and may include one to more portions and / or components configured for various purposes. For example, the materials used to construct each of the wind tower 3, the transition piece 4, and the monopile 5 may be substantially rigid and / or treated to withstand oceanic environmental conditions (e.g., long-term exposure to salt water, high winds, etc.). In a particular example, one or more buoyant structures may be configured at or otherwise affixed to a submerged portion of one or more of the transition piece 4 and the monopile 5 to compensate for forces that may be applied to such components, such as mooring loads.

[0015] The monopile 5 may be a single pile driven into the seafloor 8 and may be substantially (e.g., entirely) submerged. The monopile 5 may affix to the transition piece 4 underwater. The transition piece 4 may include portions below water and above the water surface 7, supporting the wind tower 3 substantially (e.g., entirely) above the water surface 7. One or more stability -enhancing components, such as moorings, may be affixed to the FRP-monopile 6. In examples, such components may be affixed to the transition piece 4 and / or to the monopile 5. For instance, one or more mooring lines 9 may be affixed or otherwise connected to the transition piece 4 and / or to the monopile 5. The mooring lines 9 may be affixed or otherwise attached to one or more anchors 10 that may be driven into or otherwise attached to the seafloor 8.

[0016] As described in more detail below, the individual mooring lines 9 may be connected to one or more connection components configured at the transition piece 4 and / or at the monopile 5 that may facilitate the application and adjustment of tension on the mooring lines. The mooring lines 9 may resist the environmental forces that may be applied to the FRP-monopile 6.

[0017] The FRP-monopile 6 may form a beam column “clamped” at a first end (e.g., driven into the seafloor 8) and carrying a pay load (e.g., the wind turbine 2) at the opposite end. The moorings lines 9 attached to the FRP-monopile 6 may form intermediate supports for this beam column. As an axially loaded structure configured in an oceanic environment, the FRP-monopile 6 may be subject to various steady and dynamic loads (e.g., from typical weather and less common weather events, such as storms). Such loads may be primarily lateral, for example resulting from winds, waves, and currents.

[0018] While the examples described herein may refer to FRP-monopiles used as supporting structures for wind turbines, the disclosed FRP-monopiles may be used to provide marine support for other objects, systems, and components, such as energy storage units, offshore substations, etc. Because the disclosed FRP-monopiles are not payload sensitive, FRP-monopiles as described herein may be scaled up and / or down as needed to support objects having a wide range of mass.

[0019] As described throughout the instant disclosure, mooring lines may be used to provide further stability to an FRP-monopile. Mooring lines may be configured to maintain tension, in some examples, within a tension range. Over time, such mooring lines may loosen due to dynamic forces (e.g., wind, waves, currents, etc.). This loosening may result in mooring line tension falling outside of a design tension range, therefore reducing the ability of the loosened mooring lines to mitigate motion in the 6 DOFs. While re-tensioning systems and techniques have been successfully implemented for land-based applications and for floating marine platforms, these systems and techniques have not been successfully implemented for mooring lines used to stabilize fixed marine structures.

[0020] For example, the various systems and techniques available for re-tensioning in floating structures typically involve large increases or decreases in tension, preventing the fine tension adjustment often needed for FRP-monopile mooring lines. The various systems and techniques available for re-tensioning in land-based structures typically use less robust stabilizing components due to land-based structures being subject to lower axial loads (e.g., lower levels of motion in the 6 DOFs). FRP-monopile structures require stabilizing systems and techniques that address the higher axial loads to which such structures are subject while providing finer tension adjustment. The FRP-monopile structure stabilizing systems and techniques described herein address these issues while providing safer, easier, and more cost-effective means of applying and adjusting tension in the environments in which such structures are typically located.

[0021] Examples of mooring assemblies having devices for controlling tension in mooring lines on an FRP-monopile can be found, for example, in U.S. Provisional Patent Application Number 63 / 266,989, titled “Mooring Systems for Fixed Marine Structures,” fded 21 January 2022, the contents of which are herein incorporated by reference in their entirety and for all purposes.

[0022] The prior art also includes US 2016 / 0137267 Al, which describes method of supporting a chain stopper on a vessel, a chain stopper assembly for a vessel, and a vessel. The method of supporting a chain stopper on a vessel may comprise the steps of connecting a swivel element to the support structure on the vessel such that the swivel element is pivotable around a first axis perpendicular to a substantially horizontal axis; and coupling a chain stopper element to the swivel element such that the chain stopper element is pivotable relative to the swivel element around the substantially horizontal axis. The chain stopper section comprises a longitudinal structure, for example a square or rectangular fabricated structure, which includes a pivoting chain pawl for locking the mooring line or chain in place. The prior art also includes US 7926436 B2, which describes a chain support hinged on two perpendicular axes which allows chain movement in two perpendicular planes. The chain support arrangement allows the chain to be pulled through the center of the apparatus to a desired length after which the chain is removably secured to the chain support.

[0023] The prior art also includes WO 2015 / 136183 Al, which describes a chain stopper for a floating unit, comprising a cradle engaging with a floating unit, a male member received inside the cradle, and a guiding conduit cooperating with the male member, arranged to guide the links of a chain. The cradle and male member comprise projections mutually arranged to form a ball-and-socket joint.

[0024] The prior art also includes EP 4048859 Bl, which describes a mounting device for an elongate member, comprising an elongate housing having an internal passageway; an elongate sleeve located within the internal passageway and being configured for longitudinal movement along the passageway; a plurality of ball -receiving recesses in the wall of the internal passageway, each recess having a ball-guiding surface inclined to the passageway longitudinal axis; a plurality of apertures in the sleeve; a ball located in each of the ball-receiving recesses and engaged with a respective aperture in the sleeve, the balls and the apertures being configured to allow the balls to project partially through the apertures but to prevent balls from passing through; biasing means configured to bias the sleeve in a direction to urge the balls to project radially inwardly through their respective apertures in the sleeve and into the internal passageway.

[0025] The prior art also includes GB 2534595 A, which describes an apparatus for anchoring a buoyant assembly to a submerged anchorage. The apparatus comprises a receptacle adapted for mounting to the buoyant assembly, an elongate member passable through the receptacle between first and second sides of the receptacle and a mooring line attached to the elongate member. The elongate member is passable through the receptacle in first and second opposing axial directions and the mooring line is connectable to the submerged anchorage. The receptacle is operable in a first mode, in which the receptacle inhibits passage of the elongate member through the receptacle in at least one of the axial directions, and a second mode, in which the receptacle permits passage of the elongate member through the receptacle in both axial directions. The prior art also includes GB 2551716 A, which describes a mooring connector adapted for release under load from a complementary connector.

[0026] Summary of the invention

[0027] The invention is set forth and characterized in the main claim, while the dependent claims describe other characteristics of the invention.

[0028] It is thus provided a mooring assembly for installation on a marine structure, above or below a water surface, comprising a main frame having a connecting portion for connection to the marine structure, wherein a stopper device comprises a plurality of movable support members and is arranged in the main frame, characterized by

[0029] - an elongate stopper member comprising a first end with a gripping portion, a second end configured for connection to a mooring chain or mooring line, and an intermediate engagement portion with a plurality of protrusions that are configured for releasable connection with corresponding movable support members in the stopper device; wherein the stopper device and the elongate stopper member are configured for releasable interlocking.

[0030] In one embodiment, the stopper device comprises a housing with a plurality of said movable support members arranged in a chamber, wherein the support members are movably interconnected via a ring member and biased towards each other by an elastic member, and each support member comprises one or more ratchet teeth for interaction with corresponding protrusions on the elongate stopper member. The ring member comprises a rigid material and functions as a fulcrum for each support member, whereby the support members may rotate about the ring member.

[0031] In one embodiment, each support member comprises a curved, lower support region and the chamber comprises a correspondingly curved support seat, and each support member comprises a lever arm configured for abutment against a control member which is operable between an unlocked position in which support member movement is possible and a locked position in which support member movement is not possible.

[0032] In one embodiment, the stopper device comprises a plurality of wedge-shaped support members movably arranged in a housing, and each support member comprises a wedgeshape and is configured to slide against a corresponding slanted surface in the housing. In one embodiment, said protrusions comprise a plurality of ratchet teeth configured for mating interaction with teeth on the movable support members.

[0033] In one embodiment, the stopper device comprises a spherical support portion in a stopper device housing, whereby the stopper device may be aligned with the elongate stopper member as it is being pulled into the stopper device.

[0034] In one embodiment, the mooring assembly comprises a pull-in-and-tensioner assembly arranged in the main frame, between the stopper device and the connecting portion, and comprises means for gripping at least a portion of the elongate stopper member.

[0035] In one embodiment, the pull-in-and-tensioner assembly comprises a hollow jack with an outer housing and an inner housing slidably arranged in the outer housing, and the inner housing comprises a through-going, axial, bore through which the elongate stopper member may pass, and comprises ratchet pawls.

[0036] In one embodiment, the housing comprises a support portion for a mating portion on the pull-in-and tensioner assembly, whereby the pull-in-and tensioner assembly and the stopper device are interconnected and effectively form one structure during operation.

[0037] In one embodiment, the mooring assembly comprises a guide structure, and the guide structure is detachable from the main frame, and the stopper device is arranged between the guide structure and the connecting portion.

[0038] In one embodiment , the movable support members are pawls. In one embodiment, the movable support members are arranged such that they define a channel through which said intermediate engagement portion on the elongate stopper member may be passed.

[0039] Brief description of the drawings

[0040] These and other characteristics of the invention will become clear from the following description of embodiments of the invention, given as non-restrictive examples, with reference to the attached schematic drawings that are not necessarily to scale, wherein:

[0041] Figure 1 is a schematic drawing of an exemplary fully restrained platform (FRP) for supporting a wind turbine, in accordance with examples of the present invention; Figure 2 is a schematic drawing illustrating a portion of a monopile, mooring lines, and a mooring line tensioning system, in accordance with the present invention;

[0042] Figure 3 is a schematic drawing illustrating a first embodiment of a mooring assembly according to the invention;

[0043] Figure 4 illustrates the mooring assembly illustrated in figure 3 in a partly assembled state, comprising a main frame, and a stopper device and a guide structure connected to a main frame;

[0044] Figure 5 illustrates a pull-in-and-tensioner assembly which is part of the mooring assembly illustrated in figure 3, in a tension control configuration;

[0045] Figure 6 corresponds to figure 5, and illustrates the pull-in-and-tensioner assembly in a pull-in configuration;

[0046] Figure 7 illustrates an actuator which is part of the pull-in-and-tensioner assembly illustrates in figures 5 and 6, and shows the actuator in (a) an extended state and (b) a retracted state;

[0047] Figure 8 illustrates a support frame which is part of the pull-in-and-tensioner assembly illustrated in figures 5 and 6;

[0048] Figure 9 illustrates a guide frame which is part of the pull-in-and-tensioner assembly illustrated in figures 5 and 6;

[0049] Figure 10 illustrates the mooring assembly illustrated in figure 3 in the process of being connected to — or removed from — a marine structure, such as an FRP- monopile, above or below a water surface;

[0050] Figure 11 illustrates the mooring assembly illustrated in figure 3 installed on a marine structure and the pull-in-and-tensioner assembly being arranged in a pull-in configuration and connected to a pull-in line which is connected to an elongate stopper member;

[0051] Figure 12 corresponds to figure 11 and shows the elongate stopper member having been pulled through the stopper device; Figure 13 corresponds to figure 12 and shows that the pull-in line has been disconnected and the actuator having gripped a portion of the elongate stopper member;

[0052] Figure 14 corresponds to figure 13 and shows that the actuator has advanced (i.e. pulled) the elongate stopper member towards the marine structure and thus tightened the mooring line which is attached to the elongate stopper member;

[0053] Figure 15 corresponds to figure 14 and shows the pull-in-and-tensioner assembly in the process of being removed from the main frame and the elongate stopper member being connected to the stopper device;

[0054] Figure 16 is an enlarged view of the section marked “A” in figure 15;

[0055] Figure 17 is a perspective view of an embodiment of an elongate stopper member according to the invention;

[0056] Figure 18 is an enlarged view side view of a first end of the elongate stopper member illustrated in figure 17;

[0057] Figure 19 is a perspective and partly transparent view of a simplified version of a first embodiment of a stopper device;

[0058] Figure 20 is a section view of the stopper device illustrated in figure 19, taken along the dotted line in figure 19;

[0059] Figures 21a and 21b are perspective views of the elongate stopper member inserted through the first embodiment of a stopper device, figure 21a illustrating the stopper device in an open state in which the elongate stopper member may move in the stopper device and figure 21b illustrating the stopper device in a closed state in which the elongate stopper member is locked by pawls in the stopper device;

[0060] Figure 22 is a sectional drawing corresponding to figure 21b;

[0061] Figure 23 is a schematic drawing of movable support element in the form of a pawl in the stopper device as illustrated in figures 21a,b and 22, in a closed (locked) state in which the elongate stopper member is locked by a movable support element; Figures 24-26 correspond to figure 23, but illustrate a pull-in operation in which the elongate stopper member is being moved (i.e. pulled) as indicated by the upward- pointing arrow.

[0062] Figure 27 corresponds to figure 23, but illustrates a step in a paying-out sequence;

[0063] Figure 28 corresponds to figure 23, but illustrates a step in a locking sequence;

[0064] Figures 29 and 30 correspond to figure 23, but illustrate steps in an opening sequence;

[0065] Figure 31 correspond to figure 23, but illustrates the stopper device in an open (unlocked) state in which the elongate stopper member may move uninterrupted by the pawl;

[0066] Figure 32 is a perspective and partly transparent view of a simplified version of a second embodiment of a stopper device;

[0067] Figure 33 is a section view of the stopper device illustrated in figure 32, taken along the dotted line in figure 32;

[0068] Figure 34 is a schematic illustration of a variant of the support frame;

[0069] Figures 35 and 36 illustrate the variant of the support frame illustrated in figure 34, in a tensioning operation on an elongate stopper member installed in a stopper device;

[0070] Figure 37 is a schematic illustration of a second embodiment of a main frame and stopper device of a second embodiment of the mooring assembly according to the invention;

[0071] Figure 38 is an enlarged view of the section marked “B” in figure 37;

[0072] Figure 39 is a schematic illustration of a pull-in operation using the second embodiment of the mooring assembly, wherein the second embodiment of the mooring assembly comprises the second embodiment of the stopper device and a second embodiment of a pull-in-and-tensioner assembly; Figure 40 is a schematic and partly transparent view of the second embodiment of the pull-in-and-tensioner assembly as illustrated in figure 39, in a retracted position (pawls in the lower position) and an extended position (movable support elements in the upper position);

[0073] Figure 41 corresponds to figure 39 and illustrates a tensioning operation using the second embodiment of the mooring assembly;

[0074] Figure 42 is an enlarged view of the section marked “C” in figure 41; and

[0075] Figure 43 is a schematic view of the second embodiment of the pull-in-and- tensioner assembly being lifted out of — or into — the second embodiment of the mooring assembly, and the elongate stopper member being locked by the second embodiment of the stopper device.

[0076] Detailed description of embodiments of the invention

[0077] The following description may use terms such as “horizontal”, “vertical”, “lateral”, “back and forth”, “up and down”, ’’upper”, “lower”, “inner”, “outer”, “forward”, “rear”, etc. These terms generally refer to the views and orientations as shown in the drawings and that are associated with a normal use of the invention. The terms are used for the reader’s convenience only and shall not be limiting.

[0078] Figure 2 illustrates a mooring line system for mitigating motion at an FRP-monopile, in which an FRP-monopile 6 is driven into or otherwise attached to a seafloor 8. At least a portion of the FRP-monopile 6 may be below the water surface 7, while another portion may be above the water surface. The FRP-monopile 6 illustrated in figure 2 may be a transition piece (e.g., a transition piece 4 as shown in figure 1), a monopile (e.g., a monopile 5 as shown in figure 1), one or more other portions of an FRP-monopile, or any combination thereof. A mooring line 9 extending between the FRP-monopile and a seafloor anchor 10 may be used to mitigate forces or motions applied to the FRP- monopile 6. Note that in this example, a single mooring line 9 is illustrated for exemplary purposes, but multiple mooring lines and their associated components may typically be installed at an FRP-monopile. Although not illustrated, the mooring line 9 may include a mooring line segment that is substantially above the water surface 7, a mooring line segment that is substantially below the water surface, and a connector (not shown) that may connect the mooring line segments.

[0079] A mooring assembly 11 is mounted on or otherwise attached to the FRP-monopile 6. In the example illustrated in figure 2, the mooring assembly 11 is mounted to the FRP- monopile 6 substantially above the water surface 7 (in which case it may be referred to as a Top Mooring Assembly; TMA), but it should be understood that the mooring assembly 11 may be attached to any marine structure above or below the water surface. In the illustrated embodiment, the mooring assembly 11 is mounted to a mooring porch

[0080] 12 which is affixed to the FRP-monopile 6, but it should be understood that the mooring assembly 11 may be mounted directly to the FRP-monopile 6, including the transition piece 4 or the monopile 5, or to any other marine structure. The mooring porch 12 may be welded or otherwise permanently and non-detachably affixed to the FRP-monopile 6.

[0081] Referring to figures 3 and 4, the mooring assembly 11 according to the invention comprises in a first embodiment a main frame 101 which in the illustrated embodiment comprises an elongate structure having a connecting portion 107 (for connection to a marine structure) at one end and a detachable guide structure 108 at the other end. A pull-in-and-tensioner assembly 13 is movably and removably arranged in the main frame, and a stopper device 112 is arranged between the pull-in-and-tensioner assembly

[0082] 13 and the guide structure 108.

[0083] Referring to figure 5, the pull-in-and-tensioner assembly 13 comprises in the first embodiment a linear actuator 102 - for example a hydraulically powered actuator - which may be rotatably connected to the main frame 101 at a pivot support 106 (e.g. a shaft) and comprises an extendible connector member 109 - for example a collet connector. The connection member movement (extension, retraction) is illustrated in figure 7. A guide frame 15 (see also figure 9) is connected to the actuator 102 via a connecting member 20 - for example a clamp, and comprises a sheave 105 and a rotatable interface portion 21 to the pivot support 106. A support frame 14 (see also figure 8) comprises a rotatable interface portion 16 to the pivot support 106, lifting lugs 114a, b, a support portion 18 configured for resting on a portion of the main frame 101, and a pivot actuator 17 connected to the guide frame 15 (see reference number 22 in figure 9). The support frame 14 also comprises a releasable locking device 19 - for example a pair of bolts or pins that may extended into corresponding holes 111 one on either side of the main frame 101 (see figure 4). Therefore, when the pivot actuator 17 is extended, as illustrated in figure 6, the pull-in-and-tensioner assembly 13 is in a pull-in configuration (see, for example, figure 11), and when the pivot actuator 17 is retracted, as illustrated in figure 5, the pull-in-and-tensioner assembly 13 is in a tensioner configuration (see, for example, figure 13).

[0084] The mooring assembly 11 may be connected to the marine structure above or below the water surface. For example, the main frame 101, with the guide structure 108 and stopper device 112, may be installed on the marine structure before transport to the intended offshore location, and the pull-in-and-tensioner assembly 13 may be installed when the mooring operations are about to begin.

[0085] Figure 10 illustrates the mooring assembly 11 in the process of being connected to — or removed from — a marine structure, via support lines 23. A guidewire 24 may be used to ensure that the connecting portion 107 on the mooring assembly 11 is connected to the connecting portion 25 on the marine structure. The pivoting connection between the mooring assembly 11 and the marine structure is per se known in the art.

[0086] In figure 11, a pull-in procedure has commenced, in that the pull-in-and-tensioner assembly 13 is arranged in the pull-in configuration, and a pull-in line 26 is run through the guide structure 108 and the stopper device 112 and over the sheave 105 in the guide frame. The pull-in line 26 is connected to an elongate stopper member 104 which is connected to a mooring chain or line (not shown in figure 11). The pull-in line 26 may be controlled from the marine structure itself (reference number 26’ in figure 11) or from a nearby support vessel (not shown), as indicated by reference number 26” in figure 11.

[0087] In figure 12, the elongate stopper member 104 has been pulled through the stopper device 112, and is locked for backward movement (i.e., away from the mooring device) in a manner which is described below. Therefore, the mooring chain 27 and / or line 9 is supported entirely by the stopper device 112. It should be understood that the elongate stopper member 104 may be connected directly to the mooring line 9 (figure 2), and not necessarily via a chain. In figure 13, the pull-in line has been disconnected and the pull-in-and-tensioner assembly 13 has been reconfigured to the tensioner configuration. The linear actuator 102 has been activated to extend the connector member 109 such that it is gripping the free end of the elongate stopper member 104. Retracting the connector member 109, as shown in figure 14, thus advances the elongate stopper member 104 through the stopper device 112 and thereby causes tension in the mooring chain 27 and / or line 9 to increase.

[0088] In figure 15, the pull-in-and-tensioner assembly 13 has been removed from the main frame 101, and the elongate stopper member 104 is connected to and supported by the stopper device 112, see also figure 16.

[0089] Referring to figures 17 and 18, the elongate stopper member 104 comprises in the illustrated embodiment a rod having a first end 115 with a gripping portion 116 configured for releasable connection with the connector member 109 on the linear actuator 102, and a second end 120 with a connection portion 121 for connection to the mooring chain 27 or line 9 (not shown in figures 17 and 18), and an intermediate engagement portion 117. In the illustrated embodiment, the gripping portion 116 has a frusto-conical shape with a maximum diameter which is smaller than the engagement portion 117 diameter (which is constant), and comprises a plurality of ratchet teeth 119. The intermediate engagement portion 117 comprises a plurality of protrusions (ridges and valleys) 118. In the illustrated embodiment, these protrusions 118 are ratchet teeth. Ratchet teeth are per se known in the art, i.e., uniform but asymmetrical, with each tooth having a moderate slope on one edge and a much steeper slope on the other edge, as seen in figures 17 and 18.

[0090] It should be understood that the elongate stopper member may have other shapes than that of a rod or mandrel and may have other cross-sectional shapes (e.g. non-circular, polygonal). The elongate stopper member is made of a material suitable for the intended purpose and is a rigid member. As a non-limiting example (not illustrated), the elongate stopper member may have a square cross-section with ratchet teeth arranged on two opposite sides.

[0091] Figures 19 and 20 illustrate principles of the first embodiment of a stopper device 112.

[0092] A plurality of movable support members 124, in the illustrated embodiment in the form of ratchet pawls 124, is arranged in a chamber 138 in a housing 122 and are arranged such that they define a channel 151 (through which the intermediate engagement portion 117 on the elongate stopper member may be passed). Each support member (e.g. pawl) 124 comprises a curved, lower support region 134, and the chamber 138 comprises a correspondingly curved support portion - or seat - 135. The pawls 124 are movably interconnected via a ring member 125 extending through the pawls as shown in figure 20. The ring member 125 comprises a rigid material, for example spring steel, and functions as a fulcrum for each pawl: the pawl may rotate about the ring member 125. The stopper device 112 also comprises an elastic member 123 which is formed as a ring and extends around the plurality of pawls 124, in an upper region of each pawl. The elastic member 123 may be a steel spring, for example a coil spring. Each pawl comprises a lever arm 131. The pawls are thus pivotable around the ring member 125 and is biased towards the position illustrated in figure 20 (referred to as a closed, or locked, position) by the elastic member. Referring additionally to figures 21a, 21b, 30, the first embodiment of a stopper device 112 comprises a control member 130, in the illustrated embodiment in the shape of a ring. The control member 130 is operable between an unlocked position in which pawl movement is possible, and a locked position in which pawl movement is not possible. Figures 23-28 show the control member 130 in an unlocked position, figures 22 and 31 show the control member 130 in a locked position, and figures 29, 30 show the control member 130 in an intermediate position.

[0093] Figures 21a and 21b show the elongate stopper member 104 inserted through the channel 151 in the first embodiment of a stopper device 112. In figure 21a, the stopper device in an open state, i.e., the pawls are not in contact with the elongate stopper member and the elongate stopper member may move in the stopper device. In figure 21b, the stopper device is in a closed state, with the pawls in the positions as shown in figures 20 and 22, and the elongate stopper member is locked by pawls.

[0094] Figure 23 illustrates a closed (locked) state in which the elongate stopper member is locked by a pawl. Figures 24-26 illustrate a pull-in operation in which the elongate stopper member is being moved (i.e. pulled) as indicated by the upward-pointing arrow. Figure 27 illustrates a step in a paying-out sequence. Figure 28 illustrates a step in a locking sequence. Figures 29 and 30 illustrate steps in an opening sequence. Figure 31 illustrates the stopper device in an open (unlocked) state in which the elongate stopper member may move uninterrupted by the pawl.

[0095] Each pawl 124 comprises preferably two teeth 133, whereby the load imposed by the elongate stopper member 104 - and its protrusions (e.g. ratchet teeth) 118 - is distributed. Figure 23 illustrates how the pair of pawl teeth 133 support segments or respective ratchet teeth 118 on the elongate stopper member (ratchet rod) 104.

[0096] In the illustrated embodiment, the stopper device 112 and the elongate stopper member 104 thus constitute a ratchet assembly that allows continuous linear motion in only one direction while preventing motion in the opposite direction. The illustrated elongate stopper member 104 is in the shape of a ratchet rod and has a cylindrical shape and comprises a plurality of teeth 118, and a plurality of pivoting, spring-loaded pawls 124 with pawl teeth 133 that are configured for engaging the ratchet rod teeth 118. As described above, the pawl comprises two abutment portions that are configured for interaction with — and supporting — a corresponding tooth on the rack. The teeth are uniform but asymmetrical, with each tooth having a moderate slope on one edge and a much steeper slope on the other edge.

[0097] When the elongate stopper member 104 (i.e. the ratchet rod) is moving in the unrestricted (i.e., in the drawings, upward) direction, the pawls 124 pivot and slides up and over the ratchet rod teeth 118, with the elastic member 124 forcing the pawl teeth into the depression between the ratchet rod teeth as the rod passes the pawls. When the ratchet rod moves in the opposite (in the drawings, downward) direction, however, the pawls catch against the steeply sloped edge of the ratchet rod teeth and thus preventing any further motion in that direction.

[0098] Referring again to figure 23, each pawl 124 is resting in the curved support portion - or seat - 135 in the housing 122. When the elongate stopper member 104 is moved (in the drawings, upward) for example in a tensioning operation, the pawls are lifted out of the seat 134. This distance d between the seat 135 and the curved, lower support region 134 of the pawl, can clearly be seen as increasing in figures 24-26 as the elongate stopper member 104 moves upward. As the pawls’ upward motion is limited by the lever arm 131 abutting against the control member 130 (which is in the unlocked position), the pawls are forced to pivot outward - away from the elongate stopper member 104. The distance d. between the seat 135 and the support region 134 is diminishing when the elongate stopper member is moved in the other direction and is reduced zero when the pawls are in the locked closed position (figure 23) or locked open position (figure 28).

[0099] The ring member 125, which extends through the pawls as described above, ensures that the plurality of pawls move synchronously; that is, a force imposed on one pawl (for example by the elongate stopper member) is transferred via the ring member 125 to adjacent pawls.

[0100] Referring now to figures 32 and 33, a second embodiment of a stopper device 112’ comprises a plurality of movable support members 127, in the illustrated embodiment in the form of wedge-shaped pawls, arranged in a housing 126. The support members 127 are arranged such that they define a channel 152 (through which the elongate stopper member may be passed).

[0101] Each support member (e.g. pawl) 127 comprises a guide rail 128 which is configured to slide in a corresponding guide track in the housing. The pawls comprise teeth 129 and a wedge-shaped surface that is sliding against a corresponding slanted surface in the housing 126. So while the stopper device 112 of the first embodiment (described above) may be termed as spring-loaded ratchet device, the stopper device 112’ of the second embodiment may be termed a gravity-based ratchet device.

[0102] Figures 34-36 illustrate a variant of the support frame 14’ which is useful for tensioning and re-tensioning of an elongate stopper member installed in a stopper device. The support frame is connected to the actuator via a clamp device 28.

[0103] Referring now to figures 37-43, a mooring assembly 11’ according to a second embodiment of the invention comprises a main frame 101’, a stopper device 112”, a guide sheave 31, a detachable guide structure 108, and a pull-in-and tensioner assembly 13’. The main frame lOl’comprises a receptacle 29 for the guide sheave 31, and may be connected to the marine structure via a mooring porch 12 (i.e. above water). The stopper device 112” may be of a type described above, but comprises in addition a spherical support portion 30 in which the stopper device housing 122’ may move. As illustrated in e.g. figure 38, the housing 122’ and the support portion 30 comprise complementary spherical surfaces. This configuration allows the stopper device 112” to be aligned with the elongate stopper member (e.g., ratchet rod) as it is being pulled into the stopper device and thus mitigating bending forces from the elongate stopper member.

[0104] The housing 122’ also comprises a support portion 136 for the pull-in-and tensioner assembly 13’ (see figure 38), and the pull-in-and tensioner assembly 13’ comprises a mating portion 137 (see figure 40). In use, as illustrated in figures 41 and 42, the mating portion 137 is received in the support portion 136, whereby the pull-in-and tensioner assembly 13’ and the stopper device 112” is interconnected and effectively is one structure. As the stopper device 112” moves in the spherical support 30, the pull-in-and tensioner assembly 13’ moves correspondingly.

[0105] Referring to figure 40, the pull-in-and tensioner assembly 13’ comprises in the illustrated embodiment a hollow jack with an outer housing 140 and an inner housing 141 slidably arranged in the outer housing. The inner housing comprises a through- going, axial, bore through which the elongate stopper member may pass, and comprises ratchet pawls 139, in a configuration corresponding to one of the embodiments described above. Therefore, a reciprocal motion of the inner housing 141, as indicated in figure 41, will thus move the elongate stopper member (e.g. ratchet rod) and provide tension in the mooring chain or line.

[0106] It should be understood that the pull-in-and tensioner assembly 13’ of the second embodiment may also be used in the main frame 101 of the first embodiment.

[0107] A commonality for all of the embodiments described above is that the invented mooring assembly provides for a robust and simple pull-in and tension control functionality. The inventive concept may be summarized as a “pull-through” and “click-to-connect” functionality. The ratchet device provides improved pre-tension and re-tensioning performance, as the ratchets allows for smaller steps in these processes. Also, the pull- in-and tensioner assembly may easily be removed when the mooring operation has been completed, and be reinstalled when re-tensioning is required. Although the mooring assembly according to the invention has been described in relation to an FRP-monopile, it is equally applicable to other marine installations and vessels.

[0108] In the embodiments described above, necessary elements such as power cables, hydraulic lines, actuators, load-cells and other sensors, may have been omitted as these are not required in order for the skilled person’s understanding of the invention.

[0109] Also, material types and material properties required for the mooring assembly according to the invention have not been specified, as the skilled person will know such design criteria for a given application.

[0110] In the embodiments described above, various features and details are shown in combination. The fact that several features are described with respect to a particular example should not be construed as implying that those features by necessity have to be included together in all embodiments of the invention. Conversely, features that are described with reference to different embodiments should not be construed as mutually exclusive. As a person skilled in the art readily will understand, embodiments that incorporate any subset of features described herein and that are not expressly interdependent have been contemplated by the inventor and are part of the intended disclosure. However, explicit description of all such embodiments would not contribute to the understanding of the principles of the invention, and consequently some permutations of features have been omitted for the sake of simplicity or brevity.

Claims

Claims1. A mooring assembly (11; 11’) for installation on a marine structure (4, 5, 6), above or below a water surface (7), comprising a main frame (101; 101’) having a connecting portion (107) for connection to the marine structure, wherein a stopper device (112; 112’; 112”) comprises a plurality of movable support members (124; 127) and is arranged in the main frame (101; 101’), characterized by- an elongate stopper member (104) comprising a first end (115) with a gripping portion (116), a second end (120) configured for connection to a mooring chain or mooring line, and an intermediate engagement portion (117) with a plurality of protrusions (118) that are configured for releasable connection with corresponding movable support members (124; 127) in the stopper device; wherein the stopper device (112; 112’; 112”) and the elongate stopper member (104) are configured for releasable interlocking.

2. The mooring assembly of claim 1, wherein the stopper device (112) comprises a housing (122) with a plurality of said movable support members (124) arranged in a chamber (138), wherein the support members (124) are movably interconnected via a ring member (125) and biased towards each other by an elastic member (123), and each support member comprises one or more teeth (133) for interaction with corresponding protrusions (118) on the elongate stopper member (104).

3. The mooring assembly of claim 2, wherein the ring member (125) comprises a rigid material and functions as a fulcrum for each support member, whereby the support member may rotate about the ring member (125).

4. The mooring assembly of claim 2 or claim 3, wherein each support member (124) comprises a curved, lower support region (134) and the chamber (138) comprises a correspondingly curved support seat (135), and each support member comprises a lever arm (131) configured for abutment against a control member (130) which is operable between an unlocked position in which support member movement is possible and a locked position in which support member movement is not possible.

5. The mooring assembly of claim 1, wherein the stopper device (112’) comprises a plurality of wedge-shaped support members (127) movably arranged in a housing (126),and each support member (127) comprises a wedge-shape and is configured to slide against a corresponding slanted surface in the housing (126).

6. The mooring assembly of any one of claims 1-5, wherein said protrusions comprise a plurality of ratchet teeth (118) configured for mating interaction with teeth on the movable support members (124; 127).

7. The mooring assembly of any one of claims 1-6, wherein the stopper device (112”) comprises a spherical support portion (30) in a stopper device housing (122’), whereby the stopper device (112”) may be aligned with the elongate stopper member (104) as it is being pulled into the stopper device.

8. The mooring assembly of any one of claims 1-7, further comprising a pull-in- and-tensioner assembly (13; 13’) arranged in the main frame, between the stopper device (112; 112’; 112”) and the connecting portion (107), and comprises means for gripping (109; 139) at least a portion of the elongate stopper member (104).

9. The mooring assembly of claim 8, wherein the pull-in-and-tensioner assembly (13’) comprises a hollow jack with an outer housing (140) and an inner housing (141) slidably arranged in the outer housing, and wherein the inner housing comprises a through-going, axial, bore through which the elongate stopper member may pass, and comprises ratchet pawls (139).

10. The mooring assembly of claim 9, wherein the housing (122’) comprises a support portion (136) for a mating portion (137) on the pull-in-and tensioner assembly (13’), whereby the pull-in-and tensioner assembly (13’) and the stopper device (112”) are interconnected and effectively form one structure during operation.

11. The mooring assembly of any one of claims 1-9, further comprising a guide structure (108), wherein the guide structure (108) is detachable from the main frame (101; 101’), and the stopper device (112; 112’; 112”) is arranged between the guide structure (108) and the connecting portion (107).

12. The mooring assembly of any one of claims 5-11, wherein the movable support members (124; 127) are pawls.

13. The mooring assembly of any one of claims 1-12, wherein the movable support members (124; 127) are arranged such that they define a channel (151; 152) through which said intermediate engagement portion (117) on the elongate stopper member may be passed.

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