Remaining method, lifting method, and remaining facility

Abstract

To provide a remaining method, a lifting method, and a remaining facility capable of having chains remain at sea bottom while suppressing twisting of the chains or capable of lifting the same from the sea bottom.SOLUTION: A remaining method for having a first chain C1 hung down from a first vessel 10 remain at sea bottom includes: a first attachment step for attaching a first twisting suppression member 40 in the vicinity of one end on the first vessel 10 side which is one end of the first chain C1; a hanging down step for hanging down the first chain C1 to which the first twisting suppression member 40 is attached at the first attachment step into the sea from the first vessel 10; and a remaining step for having the first chain C1 hung down at the hanging down step remain at the sea bottom.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a leaving method, a lifting method, and a leaving facility. [Background technology]

[0002] Conventionally, efforts have been made to suppress twisting of chains used for mooring floating structures and the like. Patent Document 1 discloses that twisting of the mooring chain is suppressed by using a dedicated windlass provided on a work boat. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-34650 A Summary of the Invention [Problem to be solved by the invention]

[0004] The chains that moor the floating structure may be left on the seabed until the floating structure arrives at the installation site. When leaving the chains on the seabed, it is necessary to suppress twisting of the chains using a method different from that described in Patent Document 1.

[0005] The present disclosure has been made in consideration of the above-mentioned circumstances, and aims to provide a leaving method, a lifting method, and leaving equipment that can leave a chain on the seabed or lift it from the seabed while preventing the chain from twisting. [Means for solving the problem]

[0006] A leaving method according to one embodiment of the present disclosure is a leaving method for leaving a first chain suspended from a first vessel on the seabed, and is characterized in that it includes a first installation step for attaching a first torsion suppression member to one end of the first chain near the end on the first vessel side, a hanging step for hanging the first chain with the first torsion suppression member attached in the first installation step from the first vessel into the sea, and a leaving step for leaving the first chain suspended in the hanging step on the seabed. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to provide a leaving method, a lifting method, and a leaving equipment that can leave a chain on the seabed or lift it up from the seabed while preventing the chain from twisting. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 10 is a schematic diagram of the process of hoisting or lifting a chain by a work vessel. [Figure 2] FIG. 2 is an overall view of the remaining equipment according to the embodiment. [Figure 3] FIG. 3 is an enlarged view of part III shown in FIG. 2. [Figure 4] This is a modified example of FIG. [Figure 5] 10A and 10B are diagrams showing a first connecting step and a hanging step. [Figure 6] FIG. [Figure 7] FIG. [Figure 8] FIG. 10 is a diagram showing the state in which the first chain has been left behind. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, a leaving method, a lifting method, and a leaving facility according to an embodiment of the present disclosure will be described with reference to the drawings. In this embodiment, a chain is left on the seabed using a leaving facility described later. Alternatively, the chain left on the seabed is lifted up using the leaving facility described later. The chain left on the seabed is used, for example, to moor a floating structure offshore after being lifted up from the seabed. Specifically, for example, the chain is left on the seabed using the leaving facility at the installation site of the floating structure. In this state, the chain is kept waiting until the floating structure arrives at the installation site. After the floating structure arrives, the chain is lifted up from the seabed. Then, the chain lifted up from the seabed is connected to the floating structure. This contributes to making it easier to flexibly determine the construction process of a floating structure, etc.

[0010] FIG. 1 is a schematic diagram of the process of hoisting or lifting a chain C by a work vessel B. Note that Figure 1 shows the work vessel B in states S1, S2, S3, and S4. The work vessel B in each of these states is the same work vessel B. That is, Figure 1 shows the process by which the state of the work vessel B changes over time from state S1 to S4, or from state S4 to S1. As shown in Fig. 1, the hanging or lifting of the chain C is performed, for example, by connecting one end of the chain C to a rope R that is lowered from a work vessel B. That is, in this embodiment, the hanging or lifting of the chain C refers to hanging or lifting up one end of the chain C. The hanging or lifting of the chain C is performed in a state where the other end of the chain C is supported in advance on the seabed SB by an anchor or the like (not shown).

[0011] In this embodiment, the suspension of the chain C begins in state S1 shown in FIG. 1, i.e., a state in which one end of the chain C is located on the work vessel B. As shown in states S1, S2, and S3, the rope R is let out from the work vessel B to move one end of the chain C downward, while the work vessel B is moved away from the other end of the chain C. In this way, the suspension of the chain C is carried out while the chain C extends in one direction on the seabed SB. Then, as shown in state S4, the entire chain C is brought into a state in which it extends along the seabed SB. In this state, the chain C is left on the seabed SB.

[0012] In this embodiment, the lifting of the chain C begins from state S4 shown in FIG. 1, i.e., a state in which the entire chain C is stretched along the seabed SB. As shown from state S4 to state S3 and state S2, the rope R is pulled up by the work vessel B, moving one end of the chain C upward, while the work vessel B moves closer to the other end of the chain C. In this way, the lifting of the chain C is performed while the chain C after being lifted returns to the state S1 described above. In other words, the lifting of the chain C is performed in the reverse order of the lifting of the chain C.

[0013] In this embodiment, it is preferable to prevent twisting of the chain C when hanging or lifting the chain C. Here, the rope R connected to the chain C is, for example, a wire rope. The wire rope has, for example, a spiral braided structure. When the chain C is suspended or lifted, tension is applied to the wire rope due to the weight of the chain C and the weight of the wire rope itself. This stretches the braided structure of the wire rope, and the wire rope may rotate in a twisted manner around its longitudinal axis. When this rotation of the wire rope is transmitted to the chain C, it causes the chain C to twist.

[0014] In this embodiment, in order to prevent the chain C from twisting due to the above-mentioned causes, the chain C is hung or lifted as follows. First, the remaining equipment used for suspending or lifting the chain C in this embodiment will be described.

[0015] (Remaining equipment) FIG. 2 is an overall view of the remaining facility 1 according to the embodiment. The remaining facility 1 shown in Fig. 2 leaves a mooring chain 30 on the seabed SB to moor a floating structure offshore with the mooring chain 30. In this embodiment, the structure for mooring a floating structure offshore with the mooring chain 30 is, for example, a so-called catenary mooring structure. The mooring chain 30 in this embodiment refers to a chain C that is used to moor a floating structure. As shown in FIG. 2, the remaining facility 1 includes a first vessel 10, a wire rope 20, a mooring chain 30, and a first torsion suppression member 40.

[0016] The first vessel 10 is, for example, a known work vessel. In this embodiment, the first vessel 10 has a winch 10a. The winch 10a has a known configuration. The winch 10a winds up or pays out the wire rope 20 in the remaining facility 1. The wire rope 20 is wound around a winch 10a provided on the first ship 10. The wire rope 20 is connected to a mooring chain 30. In this manner, the wire rope 20 is used to suspend or lift the mooring chain 30. In this embodiment, the wire rope 20 has, for example, a spiral braided structure.

[0017] The mooring chain 30 is connected to the wire rope 20. Specifically, the wire rope 20 is connected to one end or near one end of the mooring chain 30. In this embodiment, near one end of the mooring chain 30 refers to the range from one end of the mooring chain 30 to the middle of the mooring chain 30. The first torsion suppression member 40 is attached to the wire rope 20 and the mooring chain 30. That is, in this embodiment, the mooring chain 30 and the wire rope 20 are connected via the first torsion suppression member 40. This prevents the torsion of the wire rope 20 from being transmitted to the mooring chain 30 even if the wire rope 20 is twisted. This prevents the mooring chain 30 from twisting. The first twist suppression member 40 will be described in detail below.

[0018] (Details of the first torsion suppression member) FIG. 3 is an enlarged view of part III shown in FIG. FIG. 4 is a modification of FIG. As shown in FIG. 3, the first twist suppression member 40 includes, for example, a horizontal bar 41 and a first rotation restraint jig 42.

[0019] As shown in Fig. 3, the horizontal bar 41 is a rod-like or plate-like member extending horizontally. The wire rope 20 and the mooring chain 30 are connected to the horizontal bar 41. That is, in this embodiment, the first ship 10 and the first torsion suppression member 40 are connected via the wire rope 20. The wire rope 20 and the mooring chain 30 are also connected via the horizontal bar 41.

[0020] As shown in Fig. 3, the horizontal bar 41 and the wire rope 20 are connected via, for example, a swivel SW. That is, the first torsion suppression member 40 and the wire rope 20 are connected via the swivel SW. The swivel SW has a known configuration. The swivel SW is attached to a first attachment portion 41a provided on the horizontal bar 41. By connecting the horizontal bar 41 and the wire rope 20 via the swivel SW, even if the wire rope 20 rotates and twists due to the weight of the chain C or its own weight, the rotation of the wire rope 20 can be absorbed by the swivel SW. This prevents the rotation of the wire rope 20 from being transmitted to the horizontal bar 41. This prevents the mooring chain 30 from twisting even if the wire rope 20 rotates. The swivel SW may not be necessary.

[0021] As shown in Figure 3, the horizontal bar 41 and the mooring chain 30 are connected via, for example, a carabiner CB and a round sling RS. The carabiner CB and the round sling RS have known configurations. The carabiner CB is attached to a second attachment portion 41b provided on the horizontal bar 41 via a shackle SH. The round sling RS is attached to the carabiner CB. This allows the horizontal bar 41 and the mooring chain 30 to be connected by hooking the round sling RS attached to the mooring chain 30 onto the carabiner CB. The roundsling RS is attached to one end of the mooring chain 30, as shown in Figure 3, for example. This allows the mooring chain 30 to be hoisted or lifted by moving up and down a horizontal bar 41 connected to the wire rope 20 with a winch 10a of the first ship 10. Alternatively, the roundsling RS may be attached near one end of the mooring chain 30, as shown in Figure 4. In this case, the one end of the mooring chain 30 may be suspended from the connection between the mooring chain 30 and the horizontal bar 41, as shown in Figure 4. The carabiner CB and round sling RS may be omitted. In other words, the mooring chain 30 and horizontal bar 41 may be connected by a structure different from the carabiner CB and round sling RS.

[0022] As shown in Figure 3, when the horizontal bar 41 is located in the sea, it is subjected to resistance from seawater. This prevents the horizontal bar 41 from rotating around the vertical axis. Furthermore, by preventing the horizontal bar 41 from rotating around the vertical axis, it is possible to more reliably prevent the mooring chain 30 connected to the horizontal bar 41 from twisting. That is, in this embodiment, the first twist suppressing member 40 suppresses twisting of the first chain C1 by receiving resistance from seawater, for example.

[0023] As described above, one end or the vicinity of one end of the mooring chain 30 is connected to the carabiner CB and roundsling RS attached to the second attachment portion 41b, as shown in Figure 3 or 4. The second attachment portion 41b is provided, for example, at the horizontal center of the horizontal bar 41. The first attachment portion 41a is located on the opposite side of the second attachment portion 41b with the horizontal bar 41 in between. Here, as shown in FIGS. 3 and 4, one side of the horizontal bar 41 relative to the second mounting portion 41b in the horizontal direction is referred to as one side 41A, and the other side is referred to as the other side 41B. In this embodiment, the water resistance experienced by one side 41A around the vertical axis is approximately equal to the water resistance experienced by the other side 41B around the vertical axis. That is, the difference between the water resistance experienced by one side 41A around the vertical axis and the water resistance experienced by the other side 41B around the vertical axis is 90% or less. This more reliably prevents the horizontal bar 41 from rotating around the vertical axis. Furthermore, if the shapes of the one side 41A and the other side 41B of the horizontal bar 41 are the same, the surface areas of the one side 41A and the other side 41B are the same, and therefore the water resistance of the one side 41A and the other side 41B may be considered equal. The water resistance can be measured, for example, by attaching a water pressure gauge to the surface of the horizontal bar 41. In other words, in this embodiment, the position of the first torsion suppression member 40 where one end or the vicinity of one end of the mooring chain 30 is attached is a position where the resistance of seawater experienced by the part of the first torsion suppression member 40 on one side of the position where one end or the vicinity of one end of the mooring chain 30 is attached is approximately equal to the resistance of seawater experienced by the part of the first torsion suppression member 40 on the other side of the position where one end or the vicinity of one end of the mooring chain 30 is attached.

[0024] The first rotation restraint jig 42 is a rope attached to the end of the horizontal bar 41. Alternatively, a chain may be used for the first rotation restraint jig 42. As shown in FIG. 2, the first rotation restraint jig 42 is connected to the second boat 11. This allows the horizontal bar 41 to be supported by the second boat 11 and the first rotation restraint jig 42. This makes it possible to more reliably prevent the horizontal bar 41 from rotating around the vertical axis. In this embodiment, the first rotation constraint jig 42 is connected to both ends of the horizontal bar 41, as shown in Fig. 2, for example. Alternatively, the first rotation constraint jig 42 may be provided at only one end of the horizontal bar 41. Alternatively, the first rotation constraint jig 42 may not be provided. The remaining facility 1 according to this embodiment is configured by the above components.

[0025] (Retention method) Next, a chain retention method according to this embodiment will be described. The retention equipment 1 has been described as a system for retaining a mooring chain 30, but it is not limited to the mooring chain 30. Chains used for any other purpose may also be retained by the following method. FIG. 5 is a diagram showing the first connecting step and the hanging step. FIG. 6 is a diagram showing the leaving step. FIG. 7 is a diagram showing the removal process. FIG. 8 is a diagram showing a state in which the placement of the first chain C1 has been completed. In the following description, it is assumed that the leaving equipment 1 according to this embodiment is used to leave a first chain C1 on the seabed SB instead of the mooring chain 30. In this embodiment, the first chain C1 is, for example, one of multiple chains C left on the seabed SB. The mooring chain 30 may also be left by the following method. Also, only one chain C may be left on the seabed SB. The following description of the leaving method will be given assuming that the first chain C1 suspended from the first ship 10 is left on the seabed SB.

[0026] The remaining method according to this embodiment includes a first attachment step, a first connection step, a hanging step, a remaining step, and a removal step. 2, 3, or 4, the first attachment step is a step of attaching the first twist suppression member 40 to one end of the first chain C1, that is, the end on the side of the first boat 10, or near that end. In this embodiment, the vicinity of one end of the first chain C1 refers to the range from one end of the first chain C1 to the middle of the first chain C1. Specifically, in the first attachment step, as shown in Figure 3 or Figure 4, a roundsling RS attached to one end or near one end of the first chain C1 is attached to a carabiner CB attached to the horizontal bar 41 of the first torsion suppression member 40. In this embodiment, the first attachment step is performed, for example, on the first ship 10. By performing the first attachment step, the first chain C1 can be suspended by the wire rope 20. When performing the first attachment step, it is preferable that the first torsion suppression member 40 and the wire rope 20 are connected via a swivel SW. That is, when performing the first attachment step, it is preferable that the horizontal bar 41 of the first torsion suppression member 40 and the wire rope 20 are connected via a swivel SW in advance. At this time, the first rotation restraint jig 42 is not attached to the horizontal bar 41. The horizontal bar 41 and the first rotation restraint jig 42 are connected in the first connection step described below. By the first attachment step, the first vessel 10 and the first torsion suppressing member 40 are connected via the wire rope 20 as shown in FIG. 2, FIG. 3, or FIG.

[0027] 5, the first connecting step is a step of connecting a first rotation restraint jig 42 to the first torsion suppression member 40. That is, in the first connecting step, one end of the first rotation restraint jig 42 is connected to one end or both ends of the horizontal bar 41 of the first torsion suppression member 40. In this embodiment, one end of the first rotation restraint jig 42 is connected to both ends of the horizontal bar 41. In this embodiment, the first connecting step is performed on the first ship 10, for example. In the first connecting step, the other end of each of the first rotation restraint jigs 42 is connected to the second board 11. This allows the first rotation restraint jigs 42 and the second board 11 to support the horizontal bar 41 through the first torsion suppression member 40.

[0028] 5 and 6, the hanging process is a process of hanging the first chain C1, to which the first torsion suppression member 40 has been attached in the first attachment process, into the sea from the first ship 10. That is, in the hanging process, the wire rope 20 is let out from the winch 10a provided on the first ship 10. In this way, the first chain C1 is hung by the winch 10a provided on the first ship 10 via the wire rope 20. At this time, in the hanging process, the first torsion suppression member 40 is prevented from rotating around the vertical axis by receiving resistance from seawater and by being supported by the first rotation restraint jig 42. This suppresses twisting of the first chain C1. Furthermore, in the lifting process, as the wire rope 20 is let out from the winch 10a, it is preferable that the first vessel 10 moves away from the other end of the first chain C1 supported on the seabed SB by an anchor or the like, as shown in states S1 to S3 in Figure 1. It is also preferable that the second vessel 11 moves in the same manner as the first vessel 10 moves.

[0029] The leaving step is a step of leaving the first chain C1 suspended in the hanging step on the seabed SB. That is, as shown in Figures 5 and 6, the first chain C1 is hung until one end of the first chain C1, i.e., the end of the first chain C1 on the horizontal bar 41 side, or the vicinity of one end of the first chain C1, i.e., the connection portion between the first chain C1 and the horizontal bar 41, comes into contact with the seabed SB. In this way, in the leaving step, the one end of the first chain C1 suspended in the hanging step is left on the seabed SB. Note that whether or not the one end or the vicinity of the one end of the first chain C1 has come into contact with the seabed SB may be determined, for example, by using an underwater robot ROV (Remotely Operated Vehicle) to measure the situation around the seabed SB or by checking remote images of the area around the seabed SB. Furthermore, for example, when the hoisting load of the winch 10a suspending the first chain C1 becomes small, it may be determined that one end or the vicinity of one end of the first chain C1 has come into contact with the seabed SB. In this case, in order to reduce the impact on work on the seabed caused by the up and down movement of the first ship 10 located on the sea due to waves or the like, the first torsion suppression member 40 in addition to the first chain C1 may come into contact with the seabed SB.

[0030] 7 and 8, the detaching step is a step of detaching the first twist suppressing member 40 from the first chain C1 after the leaving step. In this embodiment, the detaching step is performed underwater. In this embodiment, the underwater operations including the first connecting step and the removing step may be performed by an underwater robot ROV, for example, as shown in FIGS. The first chain C1 is left behind through the above steps.

[0031] (Lifting method) Next, a lifting method for lifting the first chain C1 left behind on the seabed SB by the above-mentioned leaving method will be described. The hanging method according to this embodiment is the reverse of the above-described leaving method, and includes at least a lifting step. That is, first, after the above-mentioned detachment process, the first chain C1 is left on the seabed SB, and then the first torsion suppression member 40 or the second torsion suppression member is attached to one end or near one end of the first chain C1. This work is performed, for example, by an underwater robot ROV, as in the above-mentioned detachment process, as shown in Fig. 8. Then, the wire rope 20 is wound up by the winch 10a of the first ship 10, thereby lifting up one end of the first chain C1.

[0032] The second torsion suppressing member has, for example, the same configuration as the first torsion suppressing member 40. That is, in the hanging step, the first torsion suppressing member 40 used in the above-described remaining method may be used as is, or a second torsion suppressing member different from the first torsion suppressing member 40 may be used. Furthermore, in the lifting process, as the wire rope 20 is wound up by the winch 10a, it is preferable that the first vessel 10 moves so as to approach the other end of the first chain C1 supported on the seabed SB by an anchor or the like, as shown from state S4 to states S3 and S2 in Figure 1. It is also preferable that the second vessel 11 moves in the same manner as the first vessel 10 moves. In this manner, the first chain C1 is lifted. After the first chain C1 is lifted, one end of the first chain C1 is connected to, for example, a floating structure. In order to make it easier to connect one end of the first chain C1 to the floating structure, a work chain may be provided at one end of the first chain C1. The work chain may be, for example, an excess length of the first chain C1. The work chain may be cut and removed after the first chain C1 is connected to the floating structure.

[0033] As described above, according to the leaving method of this embodiment, in the first attaching step, the first torsion suppression member 40 is attached near one end of the first chain C1. In the hanging step, the first chain C1 with the attached first torsion suppression member 40 is hung into the sea from the first ship 10. Then, in the leaving step, the first chain C1 is left behind on the seabed SB. By attaching the first torsion suppression member 40 to the first chain C1 in advance in this way, twisting of the first chain C1 can be prevented when the first chain C1 is hung into the sea. Therefore, the first chain C1 can be left behind on the seabed SB while twisting of the first chain C1 is prevented.

[0034] Furthermore, the first torsion suppressing member 40 receives resistance from seawater, thereby suppressing twisting of the first chain C1. This makes it possible to reduce the force required to support the first torsion suppressing member 40, which is necessary to suppress twisting of the first chain C1, for example. This allows the structure of the first torsion suppressing member 40 to be simplified. This makes it possible to reduce the cost of the first torsion suppressing member 40, for example.

[0035] Furthermore, the position of the first torsion suppression member 40 where the vicinity of one end of the first chain C1 is attached is a position where the seawater resistance experienced by the portion of the first torsion suppression member 40 on one side of the position where the vicinity of one end of the first chain C1 is attached is approximately equal to the seawater resistance experienced by the portion of the first torsion suppression member 40 on the other side of the position where the vicinity of one end of the first chain C1 is attached. This more reliably prevents the first torsion suppression member 40 from rotating due to seawater resistance when the first chain C1 is suspended in the sea. Therefore, it is possible to more reliably prevent twisting of the first chain C1.

[0036] Furthermore, in the first connecting step, a first rotation restraining jig 42 is connected to the first torsion suppression member 40. This makes it possible to more reliably prevent the first torsion suppression member 40 from rotating in the sea when the first chain C1 is suspended in the sea. Therefore, the first torsion suppression member 40 can more reliably prevent the first chain C1 from twisting.

[0037] Furthermore, the first rotation restraint jig 42 connected to the first torsion suppression member 40 in the first connecting step is connected to the second vessel 11. This more reliably ensures the function of the first rotation restraint jig 42 to prevent the first torsion suppression member 40 from rotating in the sea. This more reliably prevents the first chain C1 from twisting.

[0038] The first vessel 10 and the first torsion suppression member 40 are connected via a wire rope 20. This allows the position of the first torsion suppression member 40 in the sea to be controlled by the wire rope 20. Furthermore, using the wire rope 20 makes the work easier than, for example, when the first vessel 10 and the first torsion suppression member 40 are connected via a chain or the like.

[0039] Furthermore, in the suspending process, the first chain C1 is suspended via the wire rope 20 using the winch 10a provided on the first ship 10. In this way, by suspending the first chain C1 using the winch 10a via the wire rope 20, the work of suspending the first chain C1 can be easily performed.

[0040] Furthermore, the first torsion suppression member 40 and the wire rope 20 are connected via a swivel SW. This prevents the first torsion suppression member 40 from rotating in the sea in conjunction with the twisting of the wire rope 20, even if the wire rope 20 is twisted during a suspension process or the like. This prevents the twisting of the wire rope 20 from being transmitted to the first chain C1. This further ensures that the first chain C1 is prevented from twisting.

[0041] Here, the first chain C1 may be used, for example, as a mooring rope for a floating structure or the like. Therefore, in the leaving step, one end of the first chain C1 suspended in the hanging step is left on the seabed SB. For example, by leaving the first chain C1 at the installation location of the floating structure, etc., the first chain C1 can be made to wait on the seabed SB until the floating structure, etc. arrives at the installation location. This makes it easier to determine the timing for pre-installing the first chain C1 as desired. This makes it easier to flexibly determine the construction process for the floating structure, etc.

[0042] Furthermore, after the leaving step, in the removing step, the first torsion suppression member 40 is removed from the first chain C1. As a result, even if the first rotation restraining jig 42, a swivel SW, etc. are attached to the first torsion suppression member 40, the first chain C1 can be left behind on the seabed SB simply by removing the first torsion suppression member 40 from the first chain C1. This reduces the effort required for leaving the first chain C1 on the seabed SB.

[0043] Furthermore, according to the above-described lifting method, after the removal step, in the lifting step, the first torsion suppression member 40 or the second torsion suppression member is attached near one end of the first chain C1, and one end of the first chain C1 is lifted. In this way, by attaching the first torsion suppression member 40 or the second torsion suppression member to the first chain C1 in advance, twisting of the first chain C1 can be suppressed when the end of the first chain C1 is lifted from the seabed SB. Therefore, the first chain C1 can be lifted from the seabed SB while suppressing twisting of the first chain C1.

[0044] Furthermore, according to the above-described remaining facility 1, in order to moor the floating structure on the ocean with the mooring chains 30, the mooring chains 30 are left on the seabed SB. This allows the mooring chains 30 to wait on the seabed SB until the floating structure arrives at the mooring location. This makes it easier to determine the timing for pre-installing the mooring chains 30 as desired. This makes it easier to flexibly determine the construction process for the floating structure. The remaining facility 1 also includes a first vessel 10 having a winch 10a, a wire rope 20 wound around the winch 10a, a mooring chain 30 connected to the wire rope 20, and a first torsion suppression member 40 attached to the mooring chain 30. As the first vessel 10 is equipped with the winch 10a and the wire rope 20 is wound around the winch 10a, the mooring chain 30 can be lowered to the seabed SB using the wire rope 20 and the winch 10a. Therefore, for example, in comparison with the case where the mooring chain 30 is lowered using a chain and a windlass, i.e., the case where the mooring chain 30 is lowered using the winch 10a and the wire rope 20, for example, an anchor chain stored in a chain locker of the first vessel 10 is connected to the mooring chain 30 and the mooring chain 30 is lowered by this anchor chain, or the case where the mooring chain 30 is lowered using a crane and a windlass, i.e., the case where the mooring chain 30 connected to the anchor chain is lowered using a crane, the seabed work involved in lowering the mooring chain 30 can be facilitated. Furthermore, by attaching the first torsion suppression member 40 to the mooring chain 30, for example, the transmission of the rotation of the wire rope 20 to the mooring chain 30 can be suppressed. Therefore, the mooring chain 30 can be left on the seabed SB while suppressing twisting of the mooring chain 30.

[0045] The technical scope of the present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present disclosure. For example, the first torsion suppression member 40 may suppress twisting of the first chain C1 not by relying on the resistance of seawater, but only by being supported by the first rotation restraint jig 42. In this case, the position of the first torsion suppression member 40 where one end or the vicinity of one end of the first chain C1 is attached may be determined arbitrarily. Furthermore, the first torsion suppression member 40 does not necessarily have to be provided with the first rotation restraint jig 42. Furthermore, when one end of the first rotation restraint jig 42 is attached to the horizontal bar 41 of the first torsion suppression member 40, the other end of the first rotation restraint jig 42 may not be connected to the second vessel 11, but may be connected to an anchor or the like (not shown), for example. Furthermore, the first vessel 10 and the first torsion suppression member 40 may be connected by any rope-like member other than the wire rope 20, a chain, or the like. Furthermore, the first torsion suppression member 40 and the wire rope 20 may be connected via any structure other than a swivel. Furthermore, to make it easier for the horizontal bar 41 to receive resistance from seawater, the surface area of ​​the horizontally facing surface of the horizontal bar 41 that faces in a direction perpendicular to the direction in which the horizontal bar 41 extends may be increased. For example, the widths of one side 41A and the other side 41B, which will be described later, may be made larger than the portions of the horizontal bar 41 where the first mounting portion 41a and the second mounting portion 41b are provided.

[0046] In addition, within the scope of the present disclosure, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described modified examples may be combined as appropriate.

[0047] (Addendum) The leaving method, the lifting method, and the leaving equipment according to the above-described embodiments can be understood, for example, as follows.

[0048] <1> A leaving method according to one embodiment of the present disclosure is a leaving method for leaving a first chain suspended from a first vessel on the seabed, and is characterized in that it includes a first installation step for attaching a first torsion suppression member to one end of the first chain near the end on the first vessel side, a hanging step for hanging the first chain with the first torsion suppression member attached in the first installation step from the first vessel into the sea, and a leaving step for leaving the first chain suspended in the hanging step on the seabed.

[0049] According to the above-described leaving method, in the first attachment step, a first torsion suppression member is attached near one end of the first chain. In the hanging step, the first chain with the attached first torsion suppression member is hung from the first vessel into the sea. Then, in the leaving step, the first chain is left on the seabed. In this way, by attaching the first torsion suppression member to the first chain in advance, twisting of the first chain can be prevented when the first chain is hung into the sea. Therefore, the first chain can be left on the seabed while twisting of the first chain is prevented.

[0050] <2> the above <1> In the remaining method according to the above, a configuration may be adopted in which the first twist suppressing member suppresses twisting of the first chain by receiving resistance from seawater.

[0051] Furthermore, the first torsion suppressing member receives resistance from seawater, thereby suppressing twisting of the first chain. This, for example, can reduce the force required to support the first torsion suppressing member in order to suppress twisting of the first chain. This allows the structure of the first torsion suppressing member to be simplified. This, for example, can reduce the cost of the first torsion suppressing member.

[0052] <3> the above <1> or <2> In the remaining method according to the present invention, a configuration may be adopted in which the position of the first torsion suppression member where the vicinity of one end is attached is a position where the resistance of seawater experienced by the part of the first torsion suppression member on one side of the position is approximately equal to the resistance of seawater experienced by the part of the first torsion suppression member on the other side of the position.

[0053] Furthermore, the position of the first torsion suppressing member where the vicinity of one end of the first chain is attached is a position where the seawater resistance experienced by the portion of the first torsion suppressing member on one side of the position where the vicinity of one end of the first chain is attached is approximately equal to the seawater resistance experienced by the portion of the first torsion suppressing member on the other side of the position where the vicinity of one end of the first chain is attached. This more reliably prevents the first torsion suppressing member from rotating due to seawater resistance when the first chain is suspended in the sea. Therefore, more reliably prevents twisting of the first chain.

[0054] <4> the above <1> from <3> In the remaining method according to any one of the above aspects, a configuration may be adopted in which the remaining method further includes a first connecting step of connecting a first rotation restraining jig to the first torsion suppression member.

[0055] Furthermore, in the first connecting step, a first rotation restraining jig is connected to the first torsion suppression member. This makes it possible to more reliably prevent the first torsion suppression member from rotating in the sea when the first chain is suspended in the sea. Therefore, the first torsion suppression member can more reliably prevent the first chain from twisting.

[0056] <5> the above <4> In the remaining method according to the above, a configuration may be adopted in which the first rotation restraint jig is connected to a second ship.

[0057] Furthermore, the first rotation restraint jig connected to the first torsion suppression member in the first connecting step is connected to the second vessel. This more reliably ensures the function of the first rotation restraint jig to prevent the first torsion suppression member from rotating in the sea. This further reliably prevents twisting of the first chain.

[0058] <6> the above <1> from <5> In the remaining method according to any one of the above aspects, a configuration may be adopted in which the first vessel and the first torsion suppression member are connected via a wire rope.

[0059] The first vessel and the first torsion suppression member are connected via a wire rope. This allows the position of the first torsion suppression member underwater to be controlled by the wire rope. Using the wire rope also makes the work easier than, for example, when the first vessel and the first torsion suppression member are connected via a chain or the like.

[0060] <7> the above <6> In the method for leaving behind the cargo, a configuration may be adopted in which, in the hanging process, the first chain is hung via the wire rope using a winch provided on the first ship.

[0061] In the suspending step, the first chain is suspended via a wire rope using a winch provided on the first ship. In this way, suspending the first chain using a winch via a wire rope makes it easy to suspend the first chain.

[0062] <8> the above <6> or <7> In the remaining method according to the above, a configuration may be adopted in which the first torsion suppression member and the wire rope are connected via a swivel.

[0063] Furthermore, the first torsion suppression member and the wire rope are connected via a swivel. This prevents the first torsion suppression member from rotating in the sea in conjunction with the twisting of the wire rope, even if the wire rope is twisted during a suspension process or the like. This prevents the twisting of the wire rope from being transmitted to the first chain. This further ensures that the first chain is prevented from twisting.

[0064] <9> the above <1> from <8> In the leaving method according to any one of the above aspects, a configuration may be adopted in which, in the leaving step, the one end of the first chain suspended in the hanging step is left on the seabed.

[0065] Here, the first chain may be used, for example, as a mooring rope for a floating structure or the like. Therefore, in the leaving step, one end of the first chain suspended in the hanging step is left on the seabed. For example, by leaving the first chain at the installation location of the floating structure, etc., the first chain can be made to wait on the seabed until the floating structure, etc. arrives at the installation location. This makes it easier to determine the timing for pre-installing the first chain as desired. This makes it easier to flexibly determine the construction process for the floating structure, etc.

[0066] <10> the above <1> from <9> In the remaining method according to any one of the above aspects, a configuration may be adopted in which the remaining method further includes, after the leaving step, a removing step of removing the first twist suppressing member from the first chain.

[0067] Furthermore, after the leaving step, the first torsion suppression member is removed from the first chain in the removing step. As a result, even if, for example, a first rotation restraining jig, a swivel, etc. are attached to the first torsion suppression member, the first chain can be left on the seabed simply by removing the first torsion suppression member from the first chain. This reduces the effort required for leaving the first chain on the seabed.

[0068] <11> A lifting method according to one aspect of the present disclosure includes the steps of: <10> The lifting method for lifting the first chain left behind by the leaving method according to the above-mentioned method is characterized in that after the removal process, it includes a lifting process of attaching the first torsion suppression member or the second torsion suppression member near the one end and lifting the one end.

[0069] According to the above lifting method, after the removal step, in the lifting step, a first torsion suppression member or a second torsion suppression member is attached near one end of the first chain, and the one end of the first chain is lifted. By attaching the first torsion suppression member or the second torsion suppression member to the first chain in advance in this way, twisting of the first chain can be suppressed when the end of the first chain is lifted from the seabed. Therefore, the first chain can be lifted from the seabed while suppressing twisting of the first chain.

[0070] <12> A remaining equipment according to one embodiment of the present disclosure is a remaining equipment that leaves a mooring chain on the seabed in order to moor a floating structure offshore with the mooring chain, and is characterized by comprising: a first vessel having a winch; a wire rope wound around the winch; the mooring chain connected to the wire rope; and a first torsion suppression member attached to the mooring chain.

[0071] According to the above-mentioned remaining equipment, the mooring chain is left on the seabed to moor the floating structure on the ocean. This allows the mooring chain to wait on the seabed until the floating structure arrives at the mooring location. This makes it easier to determine the timing for pre-installing the mooring chain as desired. This makes it easier to flexibly determine the construction process for the floating structure. The remaining equipment also includes a first vessel having a winch, a wire rope wound around the winch, a mooring chain connected to the wire rope, and a first torsion suppression member attached to the mooring chain. The first vessel is equipped with a winch and the wire rope wound around the winch, so that the mooring chain can be lowered to the seabed using the wire rope and winch. Therefore, compared to, for example, lowering the mooring chain using a chain and windlass (i.e., using a winch and wire rope to lower the mooring chain), seabed operations associated with lowering the mooring chain can be made easier than, for example, connecting an anchor chain stored in a chain locker on the first vessel to the mooring chain and lowering the mooring chain using this anchor chain, or using a crane and windlass (i.e., using a crane to lower the mooring chain connected to the anchor chain). Furthermore, by attaching the first torsion suppression member to the mooring chain, for example, it is possible to suppress the transmission of rotation of the wire rope to the mooring chain, thereby preventing twisting of the mooring chain and allowing the mooring chain to remain on the seabed. [Explanation of symbols]

[0072] 1 Remaining facilities 10 First Ship 10a winch 11 Second Ship 20 Wire Rope 30 Mooring Chain 40 First torsion suppression member 41 horizontal bar 41a First mounting part 41A One side 41b Second mounting part 41B Other side 42 First rotation restraint jig B Workboat C-Chain C1 First Chain CB Carabiner R rope RS Round Sling ROV Underwater Robot SW swivel

Claims

1. A method for leaving a first chain suspended from a first ship on a seabed, the method comprising: a first attachment step of attaching a first torsion suppression member to one end of the first chain near the end on the first ship side; a suspending step of suspending the first chain, to which the first torsion suppressing member has been attached in the first attachment step, from the first ship into the sea; a leaving step of leaving the first chain suspended in the suspension step on the seabed; Including, A method for leaving a mark.

2. The first torsion suppressing member receives resistance from seawater to suppress twisting of the first chain. The method according to claim 1 .

3. The position of the first torsion suppressing member where the vicinity of the one end is attached is a position where the resistance of seawater received by a portion of the first torsion suppressing member on one side of the position is substantially equal to the resistance of seawater received by a portion of the first torsion suppressing member on the other side of the position. The method according to claim 1 .

4. a first connecting step of connecting a first rotation restraining jig to the first torsion suppression member; The method of claim 1 further comprising:

5. The first rotation restraint jig is connected to a second vessel. The method according to claim 4, wherein the remaining part is a part of a container.

6. The first vessel and the first torsion suppression member are connected via a wire rope. The method according to any one of claims 1 to 5, wherein the remaining part is a part of a substrate.

7. In the suspending step, the first chain is suspended via the wire rope using a winch provided on the first ship. The method according to claim 6, wherein the remaining part is a part of a container.

8. The first torsion suppression member and the wire rope are connected via a swivel. The method according to claim 6, wherein the remaining part is a part of a container.

9. In the leaving step, the one end of the first chain suspended in the hanging step is left on the seabed. The method according to any one of claims 1 to 5, wherein the remaining part is a part of a substrate.

10. a removing step of removing the first twist suppressing member from the first chain after the leaving step; The method according to any one of claims 1 to 5, further comprising:

11. A lifting method for lifting the first chain left behind by the leaving method according to claim 10, comprising: a lifting step of attaching the first torsion suppression member or the second torsion suppression member to the vicinity of the one end after the removing step, and lifting the one end; A lifting method comprising:

12. A mooring facility for leaving a mooring chain on the seabed in order to moor a floating structure on the ocean, comprising: a first vessel having a winch; a wire rope wound around the winch; the mooring chain connected to the wire rope; a first torsion suppression member attached to the mooring chain; A remaining facility characterized by comprising:

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