Removing method of and holding jig of mooring chain

Abstract

To provide a removing method of and a holding jig of a mooring chain capable of safely and efficiently removing a mooring chain mooring a floating structure.SOLUTION: A holding jig 1 with a projection 2 projecting from a ship end 21a of a hull 21 to a water area side is fixed to the hull 21. A mooring chain 31 is lifted above water to a middle part in the longitudinal direction using a crane 22, one chain element 32 located in the middle part in the longitudinal direction of the mooring chain 31 is inserted into a slit 3 formed in the projection 2 and open to the water area side, and the other chain element 32 connected above the one chain element 32 is kept engaged with the projection 2. Then, the mooring chain 31 on the tip side of the chain element 32 engaged with the projection 2 is extended and mounted on the hull 21, and a part extended on the hull 21 of the mooring chain 31 is cut. Finally, the mooring chain 31 on the rear end side of the cutting position is lifted onto the hull 21 using the crane 22.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a mooring chain removal method and a holding jig, and more specifically, to a mooring chain removal method and a holding jig that can safely and efficiently remove a mooring chain that moored a floating structure. [Background technology]

[0002] Floating structures such as buoys and wave gauges that are moored in water areas are connected to mooring chains, and mooring weights (sinkers and anchors) connected to the rear end of the mooring chains are placed on the bottom of the water. The removal of floating structures, mooring chains, and mooring weights is carried out using a crane such as a crane ship, but since the mooring chains are relatively long, it is difficult to lift the entire mooring chain onto the ship in one lifting operation. Therefore, in the past, the mooring chains were lifted up to the middle of their length together with the float near the ship's hull by a crane, and workers attached shackles, wires, etc. to the lifted mooring chains to secure them to the ship's hull. After that, the mooring chains were cut halfway along their length, and the floating structure and the cut mooring chains on the floating structure side were retrieved on board the ship. The mooring chain on the mooring weight side of the cut position was re-hoisted by a crane, and the mooring chain and mooring weight were removed by repeating the process of securing the mooring chain to the hull and cutting the mooring chain.

[0003] In the conventional removal method, workers had to approach the mooring chain while it was being lifted by the crane and attach shackles and wires to the mooring chain, which posed a safety issue. In addition, because the mooring chain is heavy and large, the shackles and wires used to secure the mooring chain are also large, which posed a problem in terms of workability. In addition, if oyster shells or other substances are attached to the mooring chain, it may be difficult to attach shackles and wires to the mooring chain, and work to remove the oyster shells or other substances attached to the mooring chain is also required.

[0004] Conventionally, various methods for removing floating structures connected to mooring lines, but not mooring chains, have been proposed (see, for example, Patent Document 1). In the removal method described in Patent Document 1, a work barge moored to the bottom of the water is placed to the side of the floating structure, and horizontal movement of the floating structure relative to the work barge is restricted using a horizontal restraining wire. The floating structure is then submerged to relax the tension mooring line, and the tension mooring line is cut underwater in this state, thereby removing the floating structure and the tension mooring line. When this method is applied to a floating structure connected to a mooring chain, the mooring chain is cut underwater, but since the nominal diameter (wire diameter) of the chain element of the mooring chain used to moor the floating structure is relatively large, it takes a relatively large amount of time and effort to cut the mooring chain underwater, and diving work is also required. In addition, this method also has the problem that it is difficult to recover the mooring chain on the mooring weight side onto the hull after cutting the mooring chain midway in the longitudinal direction. Therefore, there is room for improvement in the method of removing mooring chains. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-23233 A Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a mooring chain removal method and retaining jig that can safely and efficiently remove a mooring chain that moored a floating structure. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the method for removing a mooring chain of the present invention is a method for removing a mooring chain mooring a floating structure, which comprises the steps of: fixing a holding jig having a protrusion protruding from the end of the hull toward the water area to the hull; using a crane to lift up to the middle of the mooring chain in the longitudinal direction above the water; inserting one chain element located in the middle of the longitudinal direction of the mooring chain into a slit formed in the protrusion and opening toward the water area; engaging another chain element connected on top of that chain element with the protrusion; then extending the mooring chain further forward than the chain element engaged with the protrusion and placing it on the hull; cutting the portion of the mooring chain extending over the hull; and then using the crane to pull up the mooring chain aft of the cut position onto the hull.

[0008] In order to achieve the above-mentioned objective, the mooring chain holding jig of the present invention is a mooring chain holding jig used to remove a mooring chain that moored a floating structure, and is characterized in that it has a protrusion that protrudes from the end of the hull toward the water area, and a slit that opens toward the water area is formed in the protrusion, and one chain element located midway along the length of the mooring chain is inserted into the slit, and another chain element connected on top of the chain element is engaged with the protrusion. Effect of the Invention

[0009] According to the present invention, a holding jig having a protruding portion protruding from the end of the hull toward the water area is fixed to the hull. A crane is used to lift the mooring chain to the middle of its length above the water, and one chain element located in the middle of the length of the mooring chain is inserted into a slit formed in the protruding portion and opening toward the water area, and another chain element connected above the chain element is engaged with the protruding portion, so that the mooring chain can be held by the holding jig. This operation does not require an operator to approach the mooring chain in the lifted state, and can be easily performed by operating the crane. Thereafter, the mooring chain on the tip side (floating structure side) of the chain element engaged with the protruding portion is placed on the hull so that it extends, and the part of the mooring chain extending over the hull is cut, so that the mooring chain can be safely cut on the hull. Since the middle of the mooring chain is held by the holding jig, when the mooring chain is cut, the mooring chain on the rear end side (mooring weight side) of the cut position does not fall into the water. Therefore, the mooring chain on the rear end side of the cut position can be easily and efficiently pulled up onto the ship by a crane, so that the mooring chain mooring the floating structure can be safely and efficiently removed. [Brief description of the drawings]

[0010] [Figure 1] 1 is an explanatory diagram showing a schematic plan view of a ship equipped with a mooring chain holding jig of the present invention, moored near a floating structure; FIG. [Diagram 2] FIG. 2 is an enlarged view of the holding jig of FIG. [Diagram 3] FIG. 3 is a view taken along the arrow A in FIG. 2. [Figure 4] FIG. 3 is a view taken along the arrow B in FIG. 2. [Diagram 5] FIG. 2 is an explanatory diagram showing a schematic side view of a floating structure and mooring chains hoisted above the water up to the middle of their longitudinal direction by a crane mounted on a ship. [Figure 6] This is an explanatory diagram showing a schematic front view of the state in which, from the state shown in Figure 5, one chain element located midway along the length of the mooring chain is inserted into a slit formed in the protrusion, and another chain element connected on top of that chain element is engaged with the protrusion. [Figure 7]7 is an explanatory diagram showing a schematic plan view of the state in which the mooring chain on the tip side of the chain element engaged with the protrusion is extended and placed on the hull from the state shown in FIG. 6. [Figure 8] FIG. 8 is an explanatory diagram showing a schematic plan view of the state in which the portion of the mooring chain extending over the hull in FIG. 7 has been cut away. [Figure 9] 9 is an explanatory diagram showing a schematic side view of the state in which a hoisting gear of a crane is connected to the mooring chain on the rear end side of the cut position from the state shown in FIG. 8. [Figure 10] 10 is an explanatory diagram showing a schematic side view of the state in which the mooring chain on the rear end side of the cut position in the state shown in FIG. 9 is lifted by a crane. [Figure 11] This is an explanatory diagram showing a schematic side view of the state in which the mooring chain and mooring anchor on the rear end side of the last cut position are lifted by a crane. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, a mooring chain removal method and a retaining jig of the present invention will be described based on the embodiment shown in the drawings.

[0012] As illustrated in Fig. 1, the mooring chain removal method of the present invention is a method for removing a mooring chain 31 mooring a floating structure 30, and the holding jig 1 of the present invention is used for removing the mooring chain 31 mooring the floating structure 30. Examples of the floating structure 30 include a buoy or wave gauge moored in a water area, and a floating offshore wind power generation facility. The tip of the mooring chain 31 is connected to the floating structure 30, and a mooring weight (mooring sinker or mooring anchor) 33 connected to the rear end of the mooring chain 31 is placed on the water bottom. In this embodiment, a mooring sinker is connected to the rear end of the mooring chain 31 as the mooring weight 33.

[0013] The length of the mooring chain 31 used to moor the floating structure 30 and the size of the chain elements 32 that make up the mooring chain 31 vary depending on conditions such as the size of the floating structure 30 and the water depth of the water area where the floating structure 30 is installed, but the longitudinal length of the mooring chain 31 is, for example, about 30 m to 400 m. The nominal diameter (wire diameter) of the chain elements 32 that make up the mooring chain 31 is, for example, about 5 cm to 16 cm, the longitudinal length of the chain elements 32 is, for example, about 30 cm to 110 cm, and the outer width of the chain elements 32 is, for example, about 18 cm to 70 cm.

[0014] As illustrated in Fig. 1, the holding jig 1 is installed on a hull 21 such as a ship 20 or a barge equipped with a crane 22. In this embodiment, the holding jig 1 is installed on the hull 21 (on the deck) of the ship 20. As illustrated in Figs. 2 to 4, the holding jig 1 has a protruding portion 2 that protrudes from a ship end 21a of the hull 21 towards the water area. A slit 3 that opens towards the water area is formed in the protruding portion 2.

[0015] The holding jig 1 in this embodiment is configured to have a pair of rod-shaped steel materials 4 and fixing parts 5 that fix the pair of steel materials 4 to the hull 21. The pair of steel materials 4 extend in the width direction of the hull 21. The leading end side of each steel material 4 protrudes from the end 21a of the hull 21 toward the water area, and the rear end side of each steel material 4 is disposed on the hull 21. In this embodiment, the rear end side of the pair of steel materials 4 is placed on the deck of the hull 21. The rear end side of each steel material 4 is fixed to the deck of the hull 21 by fixing parts 5 provided at multiple locations.

[0016] In this embodiment, the portions of the pair of steel materials 4 protruding from the ship end 21a of the hull 21 toward the water area constitute the protruding portion 2 of the holding jig 1. Two steel materials 4 are arranged at a distance from each other in the longitudinal direction of the ship 20, and the gap between the two steel materials 4 protruding from the ship end 21a toward the water area forms the slit 3 of the protruding portion 2.

[0017] In this embodiment, solid steel materials 4 having a rectangular cross section are used. For example, shaped steel may be used as the steel material 4. In this embodiment, spacing materials made by joining a plurality of steel materials together are fitted into a plurality of locations between the pair of steel materials 4 as the fixing parts 5, and each spacing material is joined by welding to the portion of the pair of steel materials 4 disposed on the hull 21 and to the deck of the hull 21. Furthermore, steel materials are disposed at a plurality of locations on each side of the pair of steel materials 4 as the fixing parts 5, and these steel materials are joined by welding to the portion of the pair of steel materials 4 disposed on the hull 21 and to the deck of the hull 21.

[0018] As illustrated in Figs. 2 to 4, in this embodiment, an opening / closing mechanism 6 is provided that switches the opening at the tip of the slit 3 between an open state and a closed state. In this embodiment, the opening / closing mechanism 6 is provided at the protruding tip of the protruding part 2, and the opening / closing mechanism 6 is configured to have an opening / closing bar 6a that is rotatable with respect to the protruding part 2. When the opening / closing bar 6a is extended in the ship's length direction so as to cross the opening at the tip of the slit 3, the opening at the tip of the slit 3 is closed by the opening / closing bar 6a. When the opening / closing bar 6a is rotated 180 degrees from that state to a state in which the opening / closing bar 6a extends in the ship's length direction outside the opening at the tip of the slit 3, the opening at the tip of the slit 3 is opened.

[0019] In this embodiment, a guide portion 7 for guiding the mooring chain 31 to the slit 3 is further provided on the protruding tip side of the protruding portion 2. The guide portion 7 in this embodiment is composed of a pair of metal plate members 7a that protrude and extend from the ship end 21a of the hull 21 toward the water area. The plate members 7a are respectively arranged on one side and the other side of the slit 3 in the ship's length direction. Support members 8 that support the respective plate members 7a are provided on the ship side of the hull 21. Each support member 8 is fixed to the ship side of the hull 21. The plate member 7a is fixed on the support member 8, and the end of the plate member 7a on the ship side of the hull 21 is joined to the ship end 21a of the hull 21 by welding. In this embodiment, the protruding portion 2 is arranged on the plate member 7a. The plate member 7a is not arranged below the slit 3.

[0020] The guide portion 7 is formed with a guide groove 7b for guiding the mooring chain 31 (chain element 32) to the opening of the slit 3. The guide groove 7b is structured such that the opening width increases from the opening of the slit 3 toward the tip side of the guide portion 7. That is, the opening width at the tip side of the guide portion 7 is set wider than the opening width of the slit 3. In other words, the guide groove 7b is structured such that it tapers from the tip side of the guide portion 7 toward the opening of the slit 3. As illustrated in FIG. 4, in this embodiment, a pair of reinforcing plates 9 for reinforcing the protrusion 2 are provided on the sides below the slit 3. The reinforcing plates 9 extend in the vertical direction and are fixed to the ship side of the hull 21.

[0021] 6, the width dimension SW of the slit 3 formed in the protrusion 2 is set to be wider than the nominal diameter (wire diameter) d of the chain element 32 constituting the mooring chain 31 to be removed, and narrower than the outer width B of the chain element 32. The width dimension SW of the slit 3 may be set to be, for example, 1.2 to 2.5 times, more preferably 1.2 to 2.0 times, the nominal diameter d of the chain element 32 constituting the mooring chain 31 to be removed. In other words, the width dimension SW of the slit 3 may be set to be about 1.5 cm to 15 cm wider than the nominal diameter d of the chain element 32.

[0022] Next, a method for removing the mooring chains 31 mooring the floating structure 30 using the holding jig 1 will be described.

[0023] As illustrated in Fig. 1, a ship 20 (or a barge) equipped with a crane 22 is moored in waters near a floating structure 30 to be removed. As illustrated in Figs. 1 to 4, a holding jig 1 having a protrusion 2 protruding from a ship end 21a of a hull 21 of the ship 20 into the waters is fixed to the hull 21.

[0024] Specifically, in this embodiment, first, the support member 8 is joined and fixed to the ship side of the hull 21. Next, the plate member 7a constituting the guide portion 7 is placed on the support member 8, and the plate member 7a is joined and fixed to the ship end 21a of the hull 21 and the support member 8. Next, the rear end side of the pair of steel materials 4 constituting the holding jig 1 is placed on the deck of the hull 21, and the front end side of the pair of steel materials 4 constituting the protruding portion 2 and the opening and closing mechanism 6 are placed on the plate member 7a. Fixing parts 5 are provided at multiple points on the rear end side of the pair of steel materials 4, and the rear end side of the pair of steel materials 4 is fixed to the hull 21. The work of installing the holding jig 1, the guide portion 7, and the like on the hull 21 may be performed after the ship 20 is stopped in waters near the floating structure 30 to be removed, or the holding jig 1 may be installed on the hull 21 in advance before the ship 20 sails.

[0025] Next, as shown in Fig. 5, the mooring chain 31 is hoisted above the water using the crane 22 up to the middle of its length. In the first hoisting, a hoisting tool 24 used to hoist the floating structure 30 is connected to the lower end of a hoisting wire 23 suspended from the crane 22. The hoisting tool 24 is then connected to the floating structure 30, and the floating structure 30 and the mooring chain 31 connected to the floating structure 30 are hoisted above the water near the holding jig 1 by the crane 22. The opening and closing bar 6a of the opening and closing mechanism 6 is left in a state of extending in the ship length direction outside the opening at the tip of the slit 3, and the opening of the slit 3 is left in an open state.

[0026] Next, the crane 22 is operated to move the mooring chain 31 hoisted above the water toward the holding jig 1, and as shown in Fig. 6, one chain element 32 located midway along the length of the mooring chain 31 is inserted into a slit 3 formed in the protruding part 2 of the holding jig 1 and opening to the water side, and another chain element 32 connected above that chain element 32 is brought into a state of being engaged (hooked) with the protruding part 2. At this time, the workers on the hull 21 wait in a safe place away from the holding jig 1.

[0027] In this embodiment, the crane 22 is operated to position the middle of the mooring chain 31 hoisted above the water inside the guide groove 7b of the guide section 7, and the middle of the mooring chain 31 is moved along the guide groove 7b toward the opening of the slit 3, so that the mooring chain 31 is guided to the opening of the slit 3. Then, one chain element 32 located halfway along the length of the mooring chain 31 is inserted into the slit 3, and another chain element 32 connected above that chain element 32 is engaged with the protrusion 2.

[0028] Next, as illustrated in FIG. 7, the crane 22 is operated to extend and place the mooring chain 31 on the tip side (floating structure 30 side) of the chain element 32 engaged with the protruding portion 2 onto the hull 21. In the first lifting, the floating structure 30 is placed on the hull 21, and the mooring chain 31 connected to the floating structure 30 is extended and placed on the hull 21. Then, the opening of the slit 3 is closed by the opening / closing mechanism 6 provided on the protruding tip of the protruding portion 2. In this embodiment, the worker rotates the opening / closing bar 6a 180 degrees to extend the opening / closing bar 6a in the ship length direction so as to cross the opening at the tip of the slit 3, thereby closing the opening of the slit 3. It is preferable for the worker to wait in a safe location away from the floating structure 30 and the mooring chain 31 until the tip end of the mooring chain 31 is placed on the hull 21, and then operate the opening and closing mechanism 6 after the tip end of the mooring chain 31 is placed on the hull 21.

[0029] As illustrated in Fig. 7, in this embodiment, the portion of the mooring chain 31 extending over the hull 21 is moored to the hull 21 by a mooring device 10 installed on the hull 21. The main body of the mooring device 10 is fixed to the hull 21, and the mooring line 10a reeled out from the mooring device 10 is connected to a chain element 32 of the mooring chain 31 placed on the hull 21. In this embodiment, two mooring devices 10 are provided, and two points of the mooring chain 31 extending over the hull 21 are moored to the hull 21. The number and arrangement of the mooring devices 10 can be appropriately determined depending on the size of the mooring chain 31, etc. For example, only one mooring device 10 can be provided, or two or more mooring devices 10 can be provided.

[0030] Next, as shown in FIG. 8, the portion of the mooring chain 31 extending over the hull 21 is cut by gas cutting or the like. The cutting position of the mooring chain 31 can be determined as appropriate, but it is preferable to cut the mooring chain 31 at a position on the tip side (toward the center of the hull) of the position where it is anchored by the anchoring device 10. By the above-mentioned work, the floating structure 30 and the mooring chain 31 on the tip side of the cutting position can be recovered onto the hull 21 and removed from the water area. Thereafter, the mooring chain 31 recovered onto the hull 21 is moved from the position where it was placed to another position. Even after the mooring chain 31 is cut, one chain element 32 of the mooring chain 31 on the rear end side of the cutting position remains engaged with the protruding portion 2, so that the mooring chain 31 on the rear end side does not fall into the water and remains held by the holding jig 1 (protruding portion 2). In addition, in this embodiment, the mooring chain 31 on the rear end side of the cutting position is kept in a mooring state by the mooring device 10, so that the mooring chain 31 on the rear end side is prevented from moving when the mooring chain 31 is cut.

[0031] Next, as shown in FIG. 9, the hoist 24 attached to the lower end of the hoist wire 23 suspended from the crane 22 is replaced with the hoist 24 used to hoist the mooring chain 31. Then, the chain element 32 at the tip of the mooring chain 31 on the rear side of the cut position is connected to the hoist 24. After that, the opening / closing mechanism 6 is operated to open the opening of the slit 3. In this embodiment, the worker rotates the opening / closing bar 6a 180 degrees to extend the opening / closing bar 6a in the ship length direction outside the opening at the tip of the slit 3, thereby opening the opening of the slit 3. Then, the connection between the mooring rope 10a unwound from the mooring device 10 and the chain element 32 of the mooring chain 31 on the rear side placed on the hull 21 is released. After operating the opening / closing mechanism 6 and releasing the connection between the mooring rope 10a and the chain element 32, the worker retreats to a safe place away from the mooring chain 31 on the rear side of the cut position.

[0032] Next, the mooring chain 31 on the rear end side of the cut position is lifted by the crane 22, and the crane 22 is operated to move the lifted mooring chain 31 in a direction away from the protruding portion 2, thereby removing the chain element 32 that was engaged with the protruding portion 2 from the protruding portion 2. Then, as illustrated in FIG. 10, the mooring chain 31 connected to the mooring weight 33 is lifted up to the middle of its length above the water by the crane 22. Thereafter, the mooring chain 31 is inserted into the slit 3 to be engaged with the protruding portion 2, the mooring chain 31 on the tip side of the chain element 32 engaged with the protruding portion 2 is extended and placed on the hull 21, and the part of the mooring chain 31 that is extended above the hull 21 is cut, and the middle of the length of the mooring chain 31 is retrieved onto the hull 21 and removed from the water area.

[0033] The above-mentioned series of operations is repeated until the length of the mooring chain 31 connected to the mooring weight 33 becomes shorter to a certain extent. Then, as shown in Fig. 11, finally, the mooring chain 31 and the mooring weight 33 on the rear end side from the cut position are pulled up and collected onto the hull 21 by the crane 22, and the removal of the floating structure 30, the mooring chain 31 and the mooring weight 33 is completed.

[0034] Thus, according to the present invention, by fixing the holding jig 1 having the protrusion 2 to the end 21a of the hull 21 of the ship 20 or barge, the mooring chain 31 can be hoisted above the water up to the middle of its length using the crane 22, one chain element 32 located midway along the length of the mooring chain 31 can be inserted into the slit 3 formed in the protrusion 2, and another chain element 32 connected above that chain element 32 can be engaged with the protrusion 2, thereby holding the mooring chain 31 with the holding jig 1 (protrusion 2). This operation does not require an operator to approach the mooring chain 31 in the hoisted state, and can be performed easily and safely by operating the crane 22.

[0035] Thereafter, the mooring chain 31 on the tip side of the chain element 32 engaged with the protruding portion 2 is extended and placed on the hull 21, and the portion of the mooring chain 31 extending on the hull 21 is cut, so that the cutting operation of the mooring chain 31 can be easily and safely performed on the hull 21. Since the middle of the mooring chain 31 in the longitudinal direction is held by the holding jig 1, when the mooring chain 31 is cut, the mooring chain 31 on the rear end side of the cutting position does not fall into the water. Therefore, the operation of connecting the hoisting tool 24 of the crane 22 to the mooring chain 31 on the rear end side of the cutting position can also be easily and safely performed on the hull 21. Since the mooring chain 31 on the rear end side of the cutting position is held by the holding jig 1, the operation of lifting the mooring chain 31 on the rear end side of the cutting position onto the hull 21 by the crane 22 can also be easily and efficiently performed. Thus, although the holding jig 1 has a relatively simple configuration, it is extremely useful because its use allows the mooring chains 31 mooring the floating structure 30 to be removed safely and efficiently.

[0036] As in this embodiment, the holding jig 1 can be constructed very simply by configuring it with a pair of steel materials 4 spaced apart. Setting the width dimension SW of the slit 3 of the protruding portion 2 to a value between 1.2 and 2.0 times the nominal diameter d of the chain element 32 constituting the mooring chain 31 to be removed makes it easier to smoothly insert the chain element 32 into the slit 3, and also greatly reduces the risk that another chain element 32 connected above the chain element 32 inserted into the slit 3 will fall downward from the slit 3.

[0037] The holding jig 1 only needs to have a protruding portion 2 that protrudes from the end 21a of the hull 21 toward the water area and can engage the mooring chain 31, and a slit 3 formed in the protruding portion 2 and into which the chain element 32 of the mooring chain 31 can be inserted, and the configuration of the holding jig 1 is not limited to the configuration of the embodiment exemplified above, but can have various other configurations. For example, the holding jig 1 can be formed of a plate-like member in which the slit 3 is formed.

[0038] As in this embodiment, by providing the opening / closing mechanism 6 and inserting one chain element 32 of the mooring chain 31 into the slit 3 of the protruding portion 2 and then closing the opening of the slit 3 by the opening / closing mechanism 6, it is possible to more reliably prevent the middle of the longitudinal direction of the mooring chain 31 from coming off the protruding portion 2. Therefore, by providing the opening / closing mechanism 6, the safety of the work of removing the mooring chain 31 is improved. If the opening / closing mechanism 6 is configured with a rotatable opening / closing bar 6a as in this embodiment, the opening / closing mechanism 6 can be configured very simply. In this embodiment, the opening / closing mechanism 6 is manually operated by an operator, but for example, the opening / closing mechanism 6 can be configured to be remotely operated by a remote controller. Configuring the opening / closing mechanism 6 to be remotely operated is more advantageous in improving the safety of the operator.

[0039] The opening / closing mechanism 6 may have any structure as long as it can switch the opening of the slit 3 between an open state and a closed state, and the structure of the opening / closing mechanism 6 is not limited to the structure of the embodiment exemplified above, and may have various other structures. In the holding jig 1 of the present invention, when one chain element 32 of the mooring chain 31 is inserted into the slit 3 and another chain element 32 connected on top of that chain element 32 is engaged with the protruding part 2, the mooring chain 31 is unlikely to come off the protruding part 2 in the middle of its longitudinal direction, so that even if the opening / closing mechanism 6 is not provided, it is possible to safely remove the mooring chain 31. Therefore, in the present invention, the opening / closing mechanism 6 can be provided arbitrarily as necessary.

[0040] As in this embodiment, providing a guide section 7 for guiding the mooring chain 31 into the slit 3 on the protruding tip side of the protruding section 2 is advantageous in improving the efficiency of the work of inserting the chain element 32 of the mooring chain 31, which has been hoisted above the water by the crane 22, into the slit 3. As in this embodiment, the guide section 7 can be configured very simply by configuring it with a plate member 7a provided with a guide groove 7b. Also, as in this embodiment, if the plate member 7a constituting the guide section 7 is supported by a support member 8, it becomes possible for a worker to operate the opening / closing mechanism 6 while standing on the plate member 7a, which is advantageous in improving the workability of the removal work.

[0041] The guide portion 7 may have any configuration as long as it can guide the mooring chain 31 into the slit 3, and the structure and shape of the guide portion 7 are not limited to the configurations of the embodiments exemplified above, and various other configurations are possible. In the present invention, the guide portion 7 can be provided arbitrarily as necessary.

[0042] As in this embodiment, after the mooring chain 31 at the tip end is placed on the hull 21, the part of the mooring chain 31 extending over the hull 21 is anchored to the hull 21 by the anchoring device 10 installed on the hull 21, and then the part of the mooring chain 31 extending over the hull 21 is cut, which is advantageous for safely cutting the mooring chain 31. When cutting the mooring chain 31, if the mooring chain 31 on the rear end side of the cutting position is anchored by the anchoring device 10, the movement of the mooring chain 31 on the rear end side after cutting can be more reliably suppressed by the anchoring device 10, which is even more advantageous for safely cutting the mooring chain 31. By anchoring the part of the mooring chain 31 extending over the hull 21 to the hull 21 by the anchoring device 10, the load on the protruding part 2 of the holding jig 1 can also be reduced.

[0043] In addition, in the holding jig 1 of the present invention, when the chain element 32 of the mooring chain 31 is locked to the protruding portion 2, the mooring chain 31 is unlikely to come off the protruding portion 2 midway in the longitudinal direction, so it is possible to safely remove the mooring chain 31 even when the fastening device 10 is not used. Therefore, in the present invention, the fastening device 10 can be provided arbitrarily as necessary.

[0044] In the embodiment exemplified above, a case where one mooring chain 31 is connected to the floating structure 30 has been exemplified, but for example, even when multiple mooring chains 31 are connected to the floating structure 30, the multiple mooring chains 31 can be removed using the holding jig 1 in a similar manner. Specifically, for example, when multiple mooring chains 31 are removed using one holding jig 1, first, one of the multiple mooring chains 31 is engaged with the protruding portion 2 of the holding jig 1, and the mooring chain 31 engaged with the floating structure 30 and the protruding portion 2 is extended and placed on the hull 21. At this time, the tip sides of the other mooring chains 31 connected to the floating structure 30 are also placed on the hull 21.

[0045] Then, the first mooring chain 31 and the mooring weight 33 connected to the mooring chain 31 are retrieved onto the hull 21 in the same manner as the above-mentioned work procedure. After that, the hoisting tool 24 of the crane 22 is connected to the middle of the second mooring chain 31 connected to the floating structure 30 and placed on the hull 21 in the longitudinal direction, and the chain element 32 on the tip side (floating structure 30) of the chain element 32 to which the hoisting tool 24 is connected is cut. Then, the mooring chain 31 on the rear end side (mooring weight 33 side) of the chain element 32 to which the hoisting tool 24 is connected is lifted by the crane 22 near the holding jig 1, and the middle of the second mooring chain 31 in the longitudinal direction is engaged with the protruding part 2 of the holding jig 1. After that, the second mooring chain 31 and the mooring weight 33 connected to the mooring chain 31 are retrieved onto the hull 21 in the same manner as the above-mentioned work procedure. By repeating the above-mentioned operations, even when multiple mooring chains 31 are connected to the floating structure 30, multiple mooring chains 31 can be safely and efficiently removed using one holding jig 1. Note that, for example, multiple holding jigs 1 can be provided on the hull 21, and the recovery and removal of multiple mooring chains 31 can be performed in parallel using each holding jig 1.

[0046] In the embodiment illustrated above, the mooring chain 31 is hoisted using a crane 22 mounted on a hull 21 on which the holding jig 1 is provided. However, the mooring chain 31 can also be hoisted using, for example, a crane 22 mounted on a hull 21 other than the hull 21 on which the holding jig 1 is provided, or a crane 22 mounted on an above-water structure. [Explanation of symbols]

[0047] 1 Holding fixture 2 Protrusion 3 Slit 4 Steel material 5 Fixed part 6 Opening and closing mechanism 6a Opening and closing bar 7 Guide section 7a Plate member 7b Guide groove 8 Support member 9 Reinforcement plate 10 Locking device 10a Tether 20 ships 21 Hull 21a end 22 Crane 23 Suspension wire 24 Hanging equipment 30 Floating Structures 31 Mooring chain 32 Chain Element 33 Mooring weight

Claims

1. A method for removing mooring chains that moor a floating structure, comprising the steps of: A method for removing a mooring chain, comprising the steps of: fixing a retaining jig having a protrusion that protrudes from the end of the hull into the water area, using a crane to lift the mooring chain up to the middle of its length above the water, inserting one chain element located midway along the length of the mooring chain into a slit formed in the protrusion and opening toward the water area, engaging another chain element connected on top of that chain element with the protrusion, then extending the mooring chain further forward than the chain element engaged with the protrusion and placing it on the hull, cutting the portion of the mooring chain extending over the hull, and then using the crane to pull up the mooring chain aft of the cut position onto the hull.

2. The method for removing a mooring chain according to claim 1, further comprising the step of: inserting one of the chain elements into the slit, and then closing the opening of the slit by an opening / closing mechanism.

3. 3. A method for removing a mooring chain according to claim 1 or 2, wherein a guide portion for guiding the mooring chain into the slit is provided on the protruding tip side of the protruding portion.

4. A mooring chain holding jig used to remove a mooring chain that moored a floating structure, A mooring chain holding jig characterized by having a protrusion that protrudes from the end of the hull into the water area, a slit that opens onto the water area side, a chain element located midway along the length of the mooring chain being inserted into the slit, and another chain element connected on top of the chain element being engaged with the protrusion.

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