NO20181485A1

NO20181485A1 - Coupling System for use in a Mooring System

Info

Publication number: NO20181485A1
Application number: NO20181485A
Authority: NO
Inventors: Kenneth Milde
Original assignee: Carl Stahl As
Priority date: 2018-11-21
Filing date: 2018-11-21
Publication date: 2020-05-22

Description

Technical Field of the Invention

The present invention relates in general to a system used for mooring floating structures and a method for establishing such systems. More particularly, the invention relates to a coupling device used in a mooring system for floating structures subjected to pulling forces or tension in any and all directions, comprising a coupling element constructed as a circumferentially closed structure, such as a ring, where one or more units in the form of U-shaped tube thimbles are threaded onto the coupling element, linked with mooring lines. The invention also relates to a method and use of such coupling element for mooring lines in a mooring system that may be subjected to pulling forces in any and all directions.

Background of the Invention

A typical floating aqueous fish farm plant consists of a number of cages interconnected with neighbouring cages and arranged in a predefined array of floating cages. The farm plant is moored to anchoring points on the seabed and/or shore by means of a number of mooring lines, extending from the farm plant to the anchoring points.

A cage system in a floating aqueous fish farm plant and/or other type of floating plants required to be moored to the seabed and/shore require a mooring system comprising a large number of mooring lines pointing in horizontal and/or vertical direction and/or arranged in a sideways and/or downwards inclined or slanted direction. Such systems are often configured in such way that nodes of mooring lines are required, forming a number of local foci for the ends of the different types of lines or cables.

A typical cage comprises one or more floating collars, a net suspended from the collar(s), a mooring points for mooring the cage to one or more of the neighbouring cages and/or to anchor points on the seabed/shore.

For quite some time the aquaculture fish farm industry has expressed a desire to reduce use of steel components in the upper part of the water known as the splash zone, which is the first 15 meters downwards from the surface. The splash zone is the area where corrosion is most extreme and where the effect of waves and wind are largest. Strict regulations requires periodical inspection, such inspection requiring visual control. If tendency to severe corrosion, detrimental wear and tear, or the like is discovered, for example during such inspection, the affected component or components must be replaced. Commonly such visual inspections are preformed below sea level by divers or by remotely operated cameras. Replacement or repair is always performed by lifting the defect part out of the sea. Since it is a high degree of tension in the interconnecting line system that replacement of defect component(s) may be problematic or impossible, tension relieving system on board a surface vessel is employed for relieving tension in the various lines, enabling the required replacement or repairing operations. .

The purpose of the mooring system is to keep the floating structure in a fixed position, as well as to secure that the individual floating cages are retained in a spaced relation. The mooring system is dimensioned to secure the installation and consists of mooring lines in all four directions. Mooring lines are selected to match the type of environment they are to be used in, where weather, water current, and other properties of the surroundings are taken into consideration.

Previously, mooring systems consist of mooring lines attached to a large metal collar suspended with buoys in one end and to the anchors on the other end, said elements representing a risk for collision or interference between collar and nets when subjected to waves and heavy sea.

CN 2488289 Y describes a seawater aquiculture net cage assembly with a fixed frame structure, comprising a net cage and a mooring anchors with small floats and anchor ropes. Each net cage in the system includes a square framework which is arranged around each net cage, and four connecting rings or nodes used for fixing are respectively arranged at four angles of the framework. Dead wires and floats used for fastening the net cage and taking a certain angle are arranged at connecting ring; thereby, eight connecting points are arranged at the net cage whose four sides are opposite, capable of balancing the impact from the waves, greatly increasing the stabilization of the net cage in the ocean wave, changing ocean wave resistance stress structure of the net cage, hereby achieving the aim of protecting the net cage and extending the service time of the net cage. The fixing ring is also connected with mooring lines to the cage, to buoys, and to a fixing anchor connected to a small buoy. The connecting ring is provided with angled tie bolt cages of the securing wire.

Several of these coupling elements are used in a mooring system. The introduction of a coupling element adds balance to the mooring system, ensuring that the float collars are on a somewhat fixed distance from each other, yet still safely secured. Various alternatives to the steel ring are used in current mooring systems. Most widely used is a mooring plate, which is a round galvanized steel plate with holes.

In a typical mooring system, every float collar is attached to a mooring plate on all four sides using a fibre rope in a type of crowfoot configuration where three ropes are connected to the float collar and the other end of these three ropes are connected at the mooring plate. The mooring plates in the middle of the farm will thusly be surrounded with float collars and will have four collars attached to every plate. The mooring plates on the edges of the farm will have float collars on one side and will always have two collars attached to every plate. The mooring plates on the corners of the farm, will always only have one collar attached to it.

The mooring plates are also interconnected with straight fibre rope mooring lines in order to add the stability needed. These lines make up a square for every float collar in the system. The mooring plates on the edges as well as the mooring plates on the corners will also have mooring lines that stretch to the bottom of the water body where they are bolted, attached to an anchor, or fastened in another suitable way. These same plates are also attached to a buoy which holds the frame at a given depth, normally between seven and ten meters below the sea level. This system allows a build-up of a farm with as many float collars as needed, in any direction. Any line attached to any mooring plate will be fastened using several more steel components, such as shackles, thimbles, links and chains.

Thimbles are used to increase the contact surface between the rope/mooring line and the coupling element, and to protect the lines, in order to reduce the strain and the gnaw on the rope. In prior art, there are known steel and plastic thimbles.

Traditionally, steel thimbles are used to form a closed loop or an eye. It is also known to use tube thimbles made of plastic material. Here the tube thimble is given a general U-shape with straight and parallel legs and a curved bottom region, and where the outer bottom surface of the U-shaped thimble is removed, enabling a rope or a wire more easily to be thread in through one of the legs and to be bent and threaded in through the other leg from the opposite end, whereupon the rope or wire end is spliced to form a closed loop or thimble eye. When a rope or wire with such tube thimble of plastic material, fixed to for example a ring, is tensioned, the thimble legs tend to be bent inward towards each other, whereby the legs of the thimble and the U-shaped bottom tend to be pressed towards each other, deformed to a more or less V-shape around the rig at the thimble bottom, thus forming an abrupt and weakened point shaped transfer zone. A detrimental effect of this behaviour is that the loop end of the rope or wire may be more pointed, reducing the thimble effect and exposing the wire or rope to an increased wear and tear, thus creating a possible weak link in the system rather than enhancing the mooring system.

A possible drawback with thimbles made of steel or plastic material is that they are not form stable if subjected to high tension in the lines. Contrary to thimbles of plastic material, which regain the original shape when the tension in the line is relieved, steel thimbles tend to retain the deformed shape. This may have a detrimental effect on the wire or rope reducing the protecting property of the thimble.

Since prior art technology requires high maintenance costs and frequent quality assurance, as well as higher risk of component failure that may lead to escaping of fish,it is a need for an improved system for establishing multiple connections in a mooring system with several mooring lines interconnected and jointed in a mooring node, avoiding the drawbacks of the prior art solution.

Summary of the present Invention

A major object of the present invention is to provide a connecting points or nodes between a structure and one or more lines, able to withstand large tension in the line(s) and in the nodes without having any deforming impact on the connection or nodes between the structure and the at least one line or wire and without to any degree affecting possible intended spread in various directions of the lines or wires from the nodes.

Another major object of the invention is to configure and design a thimble device system and choosing a thimble material having properties allowing the thimble device system to regain its initial shape and configuration when the tension in the line ceases.

Another major object of the invention is to provide a thimble device allowing connection to a structure, where the thimble device allows for several lines or wires to be connected substantially at one single contact point on the structure and also configured to withstand large tension in the line(s) without to any substantial degrees being deformed and also maintaining a line or wire configuration allowing the various lines or wires to be allowing

.An object of the present invention is to reduce or remove the disadvantages of the prior art solutions by eliminating or at least substantially remove the need for using the metal parts or elements in the mooring system, thereby also eliminating failure caused by corrosion, and sharp edges associated with the mooring system in the splash zone.

Another object of the present invention is to provide a mooring system where use of steel elements in the mooring system is eliminated, or at least substantially reduced and where the risk of deformation of the thimbles are eliminated, or at least substantially reduced, removing the risk for corrosion and failure of mooring elements at least in the spash zone.

Yet another object of the invention is to provide a thimble configuration retaining its intended shape even when subjected to maximum design tension in the lines.

Another objective of the invention is to provide a system that has longer intervals between necessary or required maintenance than for prior art technology.

There is also an object of the present invention to provide a system that has no sharp edges that can cause consequential rupture in a fish net or other embodiments connected to the floating installation, even when the mooring lines are subjected to large tension.

Yet another object of the present invention is to provide a coupling element in a mooring system that can withstand strain from forces in any and all directions.

Further, there is an object of the present invention is to provide a coupling element that can withstand strain from mooring lines in all four wind directions.

Another object of the present invention is to provide a singular fastening point on the coupling element for several mooring lines having a spread out at different angles and directions

There is an objective of the invention to provide a system where said thimbles can be made out of a plastic material, such as polyurethane.

Another objective of the invention is to provide a method for fastening the thimbles to the coupling element where one or more thimbles are threaded onto the coupling element before a mooring line or a rope is inserted and then spliced together to create a loop.

Another objective of the present invention is to provide a method where the system can be used in a fish farm to keep floating installations in a more or less fixed position and where the connecting system can be connected to several different elements such as anchors, buoys, floating collars etc.

A further object of the present invention is to provide a coupling element that can be used for all type of environment, where weather, water current, or other properties of the surroundings.

The objects are achieved by a mooring and thimble system as further defied by the independent claims, while embodiments, alterative and variants are defied by the dependent claims.

According to the invention it is provided a coupling device used in a mooring system for a floating structure, subjected to pulling forces or tension in any and all directions, comprising of a coupling element constructed as a circumferentially closed structure, such as a ring, where one or more units in the form of U-shaped tube thimbles, linked with a line, wire or rope, are threaded onto the coupling element. The system comprises at least one of said one or more units of U-shaped tube thimbles being in the form of two or more U-shaped tube thimbles, arranged substantially in parallel and fixed together along the U-shape end of the thimbles, and where a bushing plate, forming an integrated and unitary part of the thimble, is formed and positioned on an inner surface of the U-shaped tube thimbles, intended to face towards and to be in movable contact with a corresponding surface on the closed structure when fixed on the closed structure, preferably forming a single point of attachment in respect of the closed structure.

According to an embodiment a width of the bushing plate correspond to a width of the U-shaped tube thimbles at their closed bottom end and that a length of the bushing plates corresponds to the corresponding width of the assembled U-shaped tube thimbles.

The bushing plate may preferably, but not necessary, be curved both lengthwise and crosswise, both crosswise and lengthwise curvature being adapted to corresponding contact surface of the closed structure.

Moreover, according to an embodiment, a pair of legs of one of the in the assembled U-shaped tube thimbles form an angle with the legs of the neighbouring U-shaped tube thimbles, the angle being configured to match an ideal angle for a mooring line, when assembled..

The closed structure is in the form of a ring with a radius R and having a circular cross section with a radius r, the crosswise and lengthwise curves of the bushing being adapted to correspondingly curved surfaces of the ring, and the legs of a thimble inward until the legs touch or almost touch each other, creating an eye in the thimble.

The coupling device may for example be made from a plastic material, such as polyurethane.

According to one embodiment, the invention described is a system where two or more thimbles can be fixed to unitary body together forming an integrated, each arranged in a parallel relation to create a singular fastening point and where the inside of the u-shape of the thimbles are made of a bushing that matches the diameter of the coupling element, and where the angle between the thimbles are fixed to match the ideal angle for mooring lines in different directions.

Preferably, the legs of the thimbles narrows inward until the legs touch or almost touch each other, creating an eye or a loop of the thimble.

The node system according to the present invention does not need as frequent maintenance and replacement of part of the nodes and mooring system. Moreover, the system is robust and not prone to corrosion. A further advantage is that system is form stable and allow a single contact point for a spread of lines in different directions, still avoiding collapse of the thimble when subjected to high tension.

A major advantage of the invention is that the thimble configuration due to the properties of the thimble material or combination of materials used; and the configuration, dimensions and shape of the thimble units may withstand large tensional forces in the lines and regain its original shape and configuration once the tension in the lines ceases, thus avoiding more or less permanent deformation, all due to its flexible properties.

Yet another advantage is that the system reduces the risk for failure of the node and thus eliminated or at least substantially reduced risk for causing damage to the cage itself.

.

Brief Description of the Drawings

Embodiments of the present invention will now be described, by way of example only, with reference to the following drawings wherein:

Figure 1 shows schematically an overview of an aquaculture fish farming plant, comprising a number of interconnected cages, moored in a mooring system;

Figure 2 shows schematically a typical connecting element in the form of a ring shaped node peripherally arranged at one side of the plant and with a configuration of connected mooring line, an anchor line and three interconnecting lines provided with different types of thimbles and closed end loops or eyes Figure 3 shows schematically one embodiment of a connecting element, intended to be used in a node system according to the present invention;

Figure 4 shows schematically an embodiment with an integrated three tube thimble configuration according to the present invention, connected in parallel to each other, forming an integrated multi-thimble unit, all in according to the present invention; and

Figure 5 shows schematically a perspective of the coupling element with an assembled integrated multi-thimble unit configuration, consisting of three tube thimbles attached on the connecting element.

Detailed Description of the Invention

In the following, an embodiment of the invention shall be described in further detail, used in connection with mooring of a aquaculture cage assembly 10 in a marine environment. The assembly or plant 10 shown in Figure 1 comprises six cages 11, arranged in two interconnected rows 12, each of the two rows 12 containing three cages 11. The cages 11 are interconnected by an array of connection lines 13,14, forming a rectangular framework for mooring of the cages 11. The interconnecting lines 13,14 are interconnected at nodes 15, the nodes 15 also functioning as attachment points for mooring lines 18 for mooring the cages 11 and as attachment points for anchor lines 16 extending between the nodes 15 and anchors 17 on the seabed. According to the embodiment shown, the anchor lines 16 extend from the nodes 15 positioned along the outer periphery of the plant 10. For clarity, only one cage 11 is shown, while the position of the other cages is indicated by rings, the cages being of a type having a circular shape and may comprise one or more hollow floating rings (not shown), forming suspension for the net .

As further indicated in Figure 1, the cage 11 shown is connected to the four nodes 15 by means of three mooring lines 18 at each point. The configuration of the nodes 15 shall be described in further details below in connection with Figures 2 and 4.

As shown in Figure 1, every cage 11 is attached to a node 15 by means of mooring lines 18. The mooring lines 18 extend between nodes at each of the four corners of the framework formed by the interconnecting lines 13,14, and the cage 11. The lines 18 may for example a fibre rope attachment of a crowfoot type configuration where three ropes or lines 18 are connected to attachment points (not shown) on the float collar (not shown) from which the net of the cage 11 is suspended and the other end of these three ropes are fixed at a corresponding node 15. The nodes 15 in the middle of the farm plant, i.e. between the two rows of cages 11 shown will thusly be surrounded with float collars and will have four floating collars attached to them in addition to the four interconnecting lines 13,14. The nodes 15 along the peripheral sides of the farm 10 will have float collars on one side and will have two cages 11 attached to every node 15. The nodes 15 at the corners of the farm, will only have one float cage 11 attached to it together with two interconnecting lines 13,14 and two anchor lines 16. The nodes 15 are also interconnected with straight fibre rope interconnecting mooring lines 13,14 in order to add the stability needed. These lines13,14 make up a square for every cage 11 in the system. The nodes 15 along the periphery as well as the nodes 15 at the corners will also have anchoring lines 16 extending to the seabed, fixed to an anchor 17, or fastened in another suitable way. Each of the nodes 15 is also each attached to a buoy 20 (only one buoy is shown). The buoys like the rest of the mooring system are configured to have the necessary strength for the intended use and purpose. This system is flexible and may be assembled with a large number of cages, expanding the size of the plant lengthwise and/or crosswise, achieved merely by adding numbers of interconnecting lines 13,14, nodes 15, cages 11 and anchor lines 16 with corresponding anchors 17.

One end of each of the interconnecting lines 13,14, mooring lines 18 and anchor lines 16 are as shown in more detail, moveably attached together at the nodes 15. Referring to Figure 2, one embodiment of a node 15 shall now be discussed in further details.

According to the embodiment shown in Figure 2, two different looped groups of line ends are shown. One of the groups are single thimble loops or eyes 23, such line ends being the ends of either the interconnected lines 13,14 and/or the anchor lines 16, while the other group comprises a plurality of interconnected thimble loops or eyes 18 for connecting the cage 11 with the frame of interconnected lines 13,14 at the joint between two interconnecting lines 13.14. The configuration of an embodiment of the second group of thimbles shall be described below in relation to Figures 3 and 4.

Reference is made to Figures 3 and 4, where one embodiment of the thimble group according to the present invention will be described in more details. As indicated above, the present invention is configured to replace the prior art steel, mooring plates and steel thimbles, used in connection nodes 15 in a mooring system of an aquaculture farming plant 10, for example configured as shown in Figure 1. According to the invention, such system comprises an intertying body 21 shown here in the form of a closed ring shaped structure, for example formed as a closed ring with circular or oval shape, ref. Figure 3 The purpose of the ring shaped body 24 is to interconnect the various lines 13,14,16,18 in a secure way, thus serving as a connection point.

Figure 4 shows schematically a view of an embodiment of a multi-thimble solution 25 according to the invention. According to the embodiment shown, the multi-thimble solution 25 comprises three separate U-shaped tube thimbles 26, arranged side by side and rigidly fixed together. The thimbles 25,26 are preferably made of a plastic material, such as polyurethane, known to withstand the aggressive sea conditions in the splash zone, The system according to the present application has no sharp edges that could cause damage to the net or to the fibre ropes. Due to this construction, the interval for periodic inspections is much longer than for the prior art mooring plates and other products used in this part or mooring systems.

Each of the thimbles 25,26 comprises has a general U-shape hollow tube 27, where a part of the material of the tube 27 at the bottom of the U-shaped thimble 25,26 is cut-off, providing access to the outer bottom surface of the U-shaped tube thimble 2526, making it easier to thread a rope or wire through the thimble 25,26 for forming a loop or a closed eye at the end of the respective line.

According to one embodiment of the present invention two or more U-shaped thimbles 26 may be arranged side by side, rigidly fixed together at the lower region of the U-shaped thimbles 25,26, forming a one unitary, integrated body. This may be achieved as part of the moulding process of the multiple thimble unit 25, or by welding or gluing individual units together. According to the present invention a bushing 29 may be arranged across the inner curved bottom of the U-shaped tube thimble/the multiple U-shaped tube thimble. ,25. The purpose and configuration of the bushing 29 is to prevent the bottom part of the U-shaped tube thimble unit 25,26 from becoming deformed when subjected to large tension on the associate line(s).

The bushing 29 forms an integrated part of the thimble 25,26 and is \given a shape and configuration adapted to the shape and form of the inner curved part of the thimble(s) 25,26 on the one side and the form and shape of the intertying body on the opposite side. According to one embodiment the bushing 29 is formed in the moulding process of the thimble variant in question, thus forming an integrated, homogeneous part of the thimble 25,26.

According to the multiple U-shaped tube thimble 25 shown in Figure 4, the bushing has a convex surface corresponding to the concave inner surface at the bottom of the multiple U-shaped tube thimble 25. The opposite surface of the bushing 29 has a concave surface, the curvature being adapted to fit around the corresponding inner curvature of the intertying body 21. The thickness of the bushing is chosen so as to give the sufficient rigidity of the thimbl325,26. The convex surface of the bushing 29 is completely matched to the undulated concave surface of the multiple U-shaped thimble 25, enhancing the rigidity of the thimble 25.

The length of the bushing 29 is longer than the total length along the concave surface of the multiple U-shaped tube thimble 26’, extending outside of each side of the multiple U-shaped tube thimble 25. The bushing 29 is also curved in lengthwise direction to adapt to the corresponding curvature of a ring shaped intertying body 21..

According to an embodiment, the legs 28 of the U-shaped thimbles 25,26 may point slightly towards each other in a direction towards the free end of the legs 28, thus allowing the thimbles 25,26 to be snapped onto the ring closed ring shaped boy 24 prior to threading and splicing the rope or wire, thus avoiding the thimbles 26 to drop unintentionally off the closed ring shape body 24, ref. Figure 4. As further indicated in Figure 4, the multi-thimble solution 25 is provided with a reinforcement and stiffening plate with a shape complimentary to the curvature of the inner bottom of the U-shaped individual thimbles 26.

Although a U-shaped tube formed thimble solution with a downwards and outwards open end is shown, it should be appreciated that a closed solution may be used. Moreover dimensions and angles of the thimbles and shape, curvature and dimensions of the bushing will be adapted to the forces appearing at the site of use and of the type of plant to be moored, allowing the same, possible standardized intertying body to be used.

It should also be appreciated that the intertying body may be configured to be split for entering completed eyes or loops of a line onto the intertying unit 21 without having ty mount the lines in situ at the plant of use.

It should also be noted that the construction, configuration or shape of or material used in the intertying body or ring 21 may be stainless steel, a polymer coated steel ring or other suitable, corrosion resisting material.

Claims

1. Coupling device used in a mooring system for floating structures (10), subjected to pulling forces or tension in any and all directions, comprising a coupling element (15) constructed as a circumferentially closed structure (21), such as a ring, where one or more units in the form of U-shaped tube thimbles (25,26) are threaded onto the coupling element (21), linked with mooring lines (13,14,15,) characterized in that

- at least one of said one or more units of U-shaped tube thimbles (25,26) comprises two or more U-shaped tube thimbles (25), arranged substantially in parallel and fixed together along the U-shape end of the thimbles (26), and - a bushing plate (29) fixed to an inner surface of the U-shaped tube thimbles (25,26) and forming an integrated part of the thimble , intended to face towards and being in contact with a corresponding surface on the closed structure (21) when fixed on the closed structure (21).

preferably forming a single point of attachment in respect of the closed structure (15).

2. Coupling according to claim 1, wherein a width of the bushing plate (29) correspond to a width of the U-shaped tube thimbles (25,26) at their closed bottom end and that a length of the bushing plates (29) corresponds to the corresponding width of the assembled U-shaped tube thimbles (25,26).

3. Coupling according to claim 1 or 2, wherein the bushing plate (29) is curved both lengthwise and crosswise, both crosswise and lengthwise curvature being adapted to corresponding contact surface of the closed structure (15).

4. Coupling according to one of the claims 1 to 3, wherein a pair of legs of one of the in the assembled U-shaped tube thimbles (25,26) form an angle with the legs (28) of the neighbouring U-shaped tube thimbles (26), the angle being configured to match an ideal angle for a mooring line (13,14,16,18,) when assembled..

5. Coupling according to claim 4, wherein the closed structure is in the form of a ring with a radius R and having a circular cross section with a radius r, the crosswise and lengthwise curves of the bushing being adapted to correspondingly curved surfaces of the ring.

.

6. Coupling device (X) according to claim 1 wherein the legs of a thimble (1) inward until the legs touch or almost touch each other, creating an eye in the thimble.

7. Coupling device (X) according to any of the preceding claims wherein the thimbles (1) are made from a plastic material, such as polyurethane.