A LESS HARDWARE MOORING SYSTEM, PROCESS AND USES
THEREOF
Field of Invention:
The invention is in field of mooring systems. More particularly, to a less hardware mooring system used to hold the aquaculture fish farm against disturbing forces due to wind, wave, current and other forces due to marine traffic.
Background of Invention:
From the past decades fish production is growing every year. Aquaculture fish production is growing fast to compensate for world fish food need. To keep aquaculture fish farm at one station, good mooring system required. High forces and moments from wind, wave and current acts on the cage and try to move it away from its position. Therefore strong mooring system plays an important role. Specifically present invention relates to a method of using less hardware in the mooring system. Conventional mooring system consists of many steel components such as shackles, connecting plate etc. These components eventually deteriorate due to corrosion and require frequent inspection. These factors cause extra operational cost. When using ropes with eye splice, abovementioned problems can be eliminated and the system will last long.
Less hardware mooring systems have become widely recognised over last few years for their excellent performance over conventional mooring systems having steel components. They have several advantages over conventional system such as no corrosion, less frequent inspection etc. The term "less hardware" broadly applies to any combination of ropes, endless rings, rope with spliced eye, usually used to replace steel components. The materials may include, for example, HDPE or Dyneema® ropes or combination thereof.
Generally, conventional mooring systems consists of metal components such as connecting plate, D-shackle, thimble, master link etc. Over the period of time these components undergo corrosion and needs repair. Since the system operates in high current, wind and wave, environmental forces are high. As the steel components may reduce their strength due to corrosion they may fail during operation. Some of the work to overcome these problems has been published. However, despite significant advancement in technology, need continues for efficient ways to obtain further improvement in mooring system design. Such a need is met by present invention described herein.
Brief Description of Drawings:
Figure 1 shows the fish farming facility and the components of the mooring system in a view from top.
Figure 2 shows the side view of the facility and the components of mooring system. Figure 3 shows the perspective view of the facility and components of mooring system.
Figure 4 shows schematically the rope-in-rope connection of mooring lines.
Figure 5 shows schematically the connection between connecting element, grid line and cage mooring line (eye-in-eye connection).
Detailed Description of Drawings:
In the drawings, the reference numeral (1) indicates a less hardware mooring system for floating structure. The mooring system includes anchor lines (2), grid lines (3), net-cage mooring lines (4), buoy lines (5) and connecting element (6). The mooring system (1) holds the net cage (10) fixed in position. Figure 2 further shows floating collar (7). In Figure 2 and Figure 3, the net cage (10) is shown with additional labelling and views.
The anchor lines (2) at their first end are connected to chain (11) at its first end. At the second end of chain (11), is connected to anchor (12) resting on sea-bed (13). The chain (11) is heavy and it rests on seabed. This is why anchor line (2) is not
subjected to jerks. The chain (11) is lifted up when there is tension in anchor line
(2) and sometimes when the tension raise in anchor line (2), all the length of chain (11) gets lifted from sea-bed (13). At their second end, anchor line (2) is attached to connecting element (6). The connecting element (6) is a special arrangement of ropes. Accordingly, two ropes are joined together by crossing one another and forming a locking arrangement consisting of rope-in-rope connection between them. This node in mooring system experiences heavy loading therefore high strength ropes to be used. At the four ends of connecting element spliced eyes are to be formed for connection to other ropes. Connection between connecting element (6) and anchor line (2) is made of ropes which in turn are made of polymer material. The end of connecting element (6) and anchor line (2) are spliced and formed into an eye shape. These eyes were covered with protective fabric made of polyester material. These eyes were then joined together as if it is forming a chain. In figure 5 one or more anchor lines (2) are attached to connecting element (6). There is no restriction on number of anchor lines (2) to be attached to connecting element (6). In the drawings, the connecting element (6) is shown rectangular; however, it can take any shape due to forces acting on attached lines and since it is flexible.
The grid line (3) extends from one connecting element (6) to other connecting element and so on. Grid lines (3) form a network of ropes around the net cage (10). The connecting element (6) and grid lines (3) are submerged below water level upto few meter so that a vessel can pass without any obstruction. Two or more grid lines
(3) attach to connecting element (6). The grid lines (3) are spliced to form an eye. Similarly connecting element (6) formed of ropes (rope-in-rope connection) also spliced to form eyes at its four ends. This is shown in Figure 4 and Figure 5.
The net cage mooring lines (4), hence after known as bridle lines extends from one connecting element (6) to floating collar (7). The bridle lines (4) at one end are connected to floating collar (7) and at their other end these line are connected to connecting element (6) by eye-in-eye or by direct woven connection of two or more ropes construction as shown in figure 5.
The buoy line (5) extends from connecting element (6) to a floating buoy (15) wherein the floating buoy (15) is on the water surface (14).
Detailed Description of Invention:
Described herein is a less hardware mooring system used for holding the aquaculture fish farm against disturbing forces due to wind, wave, current and other forces due to marine traffic. Specifically the invention relates to method of connecting net cage mooring lines, floating buoy lines (5) and anchor lines (2) together, wherein these are generally submerged in water and are continuously under the action of forces.
The present invention relates to the connecting element (6) in the mooring system for floating structures, wherein the mooring system constitutes atleast one anchor line and two other lines which extends in different directions, in different plane and the connecting element (6) being constructed by flexible ropes.
In accordance with above embodiment, grid lines, net cage mooring lines and anchor lines are connected to connecting element (6) by spliced eye-in-eye or by direct woven connection of two or more ropes connection.
A fish farm facility comprises of many components. These are net bag, floating collar, lifesaving equipments such as rafts and mooring system. The fish farm facility is constituted by two or more cages. The mooring system of the facility constitute of series of anchors at the sea bed. To the anchors, one end of heavy chains is connected. The chains are generally lying on seabed and restrict vertical movement. Other end of chain is connected to one end of a line whose other end is connected to the connecting element submerged in water. The line is generally a rope made of polymer material. This line is known as anchor line (2). There can be more than one anchor lines connected to the connecting element (6). At each
connecting element (6) a floating buoy (15) is connected via buoy rope whose one end is connected to the connecting element (6) and other end to the floating buoy (15). The floating buoy (15) helps to keep grid lines (3) at desired water depth. Every cage is surrounded by grid of ropes. The ropes are connected to each other at different nodes. Therefore, for example a grid line (3) at the end of the fish farm facility has one end connected to one connecting element (6) and other end is connected to other connecting element (6) and so on. Further from the connecting element atleast one line is connected to cage structure. Generally two lines from the connecting element are connected to floating collar (7). This helps in sharing load between two lines and station keeping.
Conventional mooring systems consists of metal components such as connecting plate, D-shackle, thimble, master link etc. Over the period of time these components undergo corrosion and needs repair. As the system operates in high current, wind and wave, therefore environmental forces are high. As the steel components may reduce their strength due to corrosion they may fail during operation.
Therefore, in an embodiment, instead of using metal and metal alloys as connecting element, flexible ropes are used as connecting elements (6). More specifically, the connecting element (6) is constructed by rope-in-rope construction. To the connecting element anchor line (2), grid line (3), buoy line (5) and cage structure mooring lines or bridles (4) are attached. The lines can be attached directly to the connecting element (6) by their spliced eye-in-eye or by direct woven connection of two or more ropes connection method. To avoid rope-to-rope friction smaller spliced eye was formed on cage structure mooring lines (4).
In accordance with above embodiment, the connecting element (6) is a special arrangement of ropes. Two ropes joined together by crossing one another and forming a locking arrangement between them. This node in mooring system experiences heavy loading therefore high strength ropes to be used. At the four ends of connecting element spliced eyes are to be formed for connection to other ropes.
Connection between connecting element (6) and anchor line (2) is made of ropes. Said ropes are made of polymer material. The end of connecting element (6) and anchor line (2) are spliced and formed into an eye shape. These eyes were covered with protective fabric made of polyester material. These eyes were then joined together as if it is forming a chain.
The connecting element of the invention includes two ropes crossing each other to form rope-in-rope connection. In accordance with above embodiment, grid lines, net cage mooring lines and anchor lines are connected to connecting element (6) by spliced eye-in-eye or by direct woven connection of two or more ropes connection. In another embodiment, the invention relates to the method of setting up mooring system for floating structures, wherein the floating structure is moored to sea-bed by anchor lines.
There are two options on how to connect floating buoy (15) to connecting element (6). The first option is use of ropes. At first end the buoy line (5) is attached to connecting element (6) by forming loop connection and at the other end, it is attached to floating buoy (15) by forming round rope by endless sling. The second option is use of round sling. The method is similar to explained above. There is slight modification at the buoy end.
Present invention is described for sea water, but the invention is equally suitable for lakes, inland waters and brackish waters as well. As an example of floating structure, fish farm facility is described here. Other floating structures may include floating platforms, offshore wind turbines and offshore floating oil platforms etc.