JP6316354B2 - How to lay mooring chains - Google Patents

Description

The present invention relates to a mooring chain laying method for mooring a floating structure such as an oil plant on the ocean with a plurality of mooring chains.

As shown in FIG. 1, a large floating structure 2 such as an oil plant is moored offshore by a number of mooring chains 3 each having an anchor 4 at the tip.
Conventionally, when laying a plurality of mooring chains 3 for mooring a floating structure 2 on the sea floor, as shown in FIG. 6, first, in a state where a large number of mooring chains 3 are loaded on a carriage 50, The carriage 50 is moved to the construction area by a support vessel (not shown). Thereafter, the carriage 50 is moored by a plurality of mooring lines 53 for carriages. Further, after moving the hoist ship 51 to the construction area by a support ship (not shown), the hoist ship 51 is moored by a plurality of hoist ship mooring lines 54. The plurality of mooring lines 53 for mooring the base boat 50 are wound up or sent out, and the mooring lines 54 for hoisting ships that moor the hoist ship 51 are hoisted or sent out. And the hoisting ship 51 are adjusted. The mooring line 53 for the carrier and the mooring line 54 for the hoist ship are constituted by a chain, a wire rope, or the like.

  When the mooring chain 3 (see FIG. 1) on the trolley 50 is laid on the seabed after the trolley 50 and the hoisting ship 51 are moved to the construction area by each supporting ship, as shown in FIG. While the carriage 50 and the hoist ship 51 are brought close to each other, the anchor 4 (see FIG. 1) of the mooring chain 3 on the carriage 50 is lifted by the crane 52 of the hoist ship 51, and the anchor 4 is lowered into the sea. As shown in FIG. 7, the mooring chain 3 is unwound from the trolley 50 by separating the trolley 50 and the hoisting ship 51, and the mooring chain 3 is laid on the seabed for a predetermined length. Next, the trolley 50 and the hoist ship 51 are moved to the next position by each support ship, and the laying operation described above is repeated to lay the plurality of mooring chains 3 and 3 on the trolley 50 on the seabed.

However, this conventional method requires at least a base ship 50 on which the mooring chain 3 is loaded and a hoisting ship 51 having a crane 52, and each supporting ship for moving the base ship 50 and the hoisting ship 51 is also required. There is a risk that the construction cost will be high. Moreover, in this conventional method, it takes time for the positioning work for moving the carriage 50 and the hoist ship 51 to the predetermined position and the mooring work for the carriage 50 and the hoist ship 51, and the construction cost may be further increased. is there. Moreover, in this conventional method, since the anchor 4 is lowered at one point by the suspension wire of the crane 52 of the hoist ship 51, when the anchor 4 descends in the sea, the anchor 4 easily rotates around the suspension wire. The normal posture cannot be maintained.

  Therefore, Patent Document 1 discloses a method for installing a floating structure with a chain. The invention according to Patent Document 1 is configured as follows. That is, the structure is floated on the water, and the mooring chain is sequentially fed out by the crane while being moved by the support ship in a direction to release it from the work ship on which the mooring chain is mounted. Subsequently, when the deepest portion of the drawn mooring chain suspended in a U-shape reaches about 1/3, the feeding by the crane is stopped, and the mooring chain is fixed to the hull of the work ship every certain length. And hang it up and down in a zigzag shape. Subsequently, when the anchor is put into the water in this state, the anchor and the mooring chain connected to the anchor are settled and the respective lashes are released, and the mooring chain sinks with its upper end supported by the structure. And the bottom end comes to bottom.

JP 2010-228647 A

  However, even in the invention of Patent Document 1, a support ship for moving a structure or work ship is necessary, and the construction cost cannot be suppressed, and the above-described problems cannot be solved. Moreover, in the invention of Patent Document 1, the anchor is thrown into the sea and the anchor is settled by free fall, which is a problem from the viewpoint of safety and quality. In particular, in terms of quality, when the anchor is freely dropped, the mooring chain may be twisted, and the twisting of the mooring chain may lead to breakage of the mooring chain. Further, if the anchor is allowed to fall freely, there is a possibility that when the anchor is bottomed, the anchor is likely to bottom in a posture that adversely affects the holding force of the mooring chain, which may cause inconvenience.

The present invention has been made in view of such points, and an object of the present invention is to provide a method for laying a mooring chain that is good in terms of safety and quality by reducing the work time by reducing the work time.

The present invention relates to a mooring chain laying method according to claim 1 as a means for solving the above-mentioned problems. The mooring chain is moored on the ocean by a plurality of mooring chains. A mooring chain laying method in which
After the self-propelled hoist ship having self-propulsion capability and capable of loading the plurality of mooring chains is sailed to the construction area by itself, the self-propelled hoist ship is brought to a predetermined position in the construction area by a fixed point holding device. Holding the anchor of the mooring chain with the crane of the self-propelled hoist ship and suspending it in the sea, the mooring chain is put into the sea with a dedicated windlass provided for the self-propelled hoist ship. towards and out feed, the by-grounding the anchor, the equipped with underwater camera in the remote controlled unmanned underwater vehicle, check the wear bottom position and orientation of the anchor, is determined and the result to be good After that, a necessary holding force is secured to the mooring chain by applying a tensile force to the mooring chain and burying the anchor .
In the invention of claim 1, a plurality of mooring chains are loaded on a self-propelled hoist ship having self-propulsion capability, and the self-propelled hoist ship is navigated to a predetermined construction area by itself. Subsequently, in the construction sea area, the self-propelled hoist ship is positioned and held at a predetermined position by a fixed point holding device. That is, the fixed point holding device guides (positions) the self-propelled hoist ship to a predetermined position in the construction sea area based on information from a positioning device such as GPS, and then includes a plurality of propulsion devices provided in the self-propelled hoist ship. This is a system for controlling the self-propelled hoist ship to be held at the predetermined position by driving. Thus, since the self-propelled hoist ship is held at a predetermined position in the construction sea area by the fixed point holding device, it is not necessary to moor the self-propelled hoist ship by a plurality of mooring lines. And after positioning and holding the self-propelled hoist ship in a predetermined position in the construction sea area, the anchor of one mooring chain is lifted by a crane provided in the self-propelled hoist ship, While being suspended in the sea, the mooring chain can be sent out into the sea by a windlas provided in a self-propelled hoist ship. Thereby, generation | occurrence | production of the twist to a mooring chain can be suppressed, and a breakage | rupture of a mooring chain can be suppressed by extension. In addition, since the anchor descends toward the seabed by two-point suspension of the windlass and the suspension wire of the crane of the self-propelled hoist ship, the anchor posture is maintained normally, that is, the anchor rotates around the suspension wire. Can be suppressed. The windlaser is a device for sending out and winding up the mooring chain, and the self-propelled hoist ship is provided with a windlas dedicated to the mooring chain of the floating structure.
In addition, the anchor landing position and its posture will affect the holding force of the mooring chain necessary for mooring the floating structure. By applying a tensile force to the chain and burying the anchor, a necessary holding force can be secured for the mooring chain.

The invention relating to the laying method of the mooring chain according to claim 2 is the invention according to claim 1, wherein after the anchor is grounded and the anchor is separated from the suspension wire of the crane, the self-propelled hoist ship is operated by itself. And the mooring chain is sent out by the windlass for a predetermined length along with the movement.
According to the second aspect of the present invention, the mooring chain can be sent out for a predetermined length by the windlaser while the self-propelled hoist ship is moved by the propulsion device after the crane suspension wire is separated from the anchor anchored.

According to a third aspect of the invention of the mooring chain laying method, in the first or second aspect of the invention, when the mooring chain is sent into the sea by the windlass, the position and posture of the anchor are controlled by the crane operation. It is characterized by this.
In the invention of claim 3, the bottom position of the anchor and the posture at the bottom can be made normal.

According to the present invention, since a self-propelled hoisting ship having self-propulsion capability and capable of loading a plurality of mooring chains is adopted, a plurality of ships such as a base ship, a hoisting ship, and a support ship for navigating them are provided. do not need. In addition, the self-propelled hoist ship includes a fixed point holding device, and the self-propelled hoist vessel can be positioned and held at a predetermined position in the construction sea area by the fixed point holding device. There is no need to moor at. Thereby, construction time can be shortened compared with the past, and a construction cost can be reduced significantly by extension.
Moreover, according to the present invention, the self-propelled hoist ship is equipped with a windlass, and since the mooring chain is sent out into the sea by the windlass, compared to the conventional laying method by free fall of an anchor, Superior in safety and quality.

FIG. 1 is a schematic view showing a state in which a floating structure is moored by a plurality of mooring chains. FIG. 2 is a schematic side view of a mooring chain laying facility according to an embodiment of the present invention. FIG. 3 is a schematic plan view of a mooring chain laying facility according to an embodiment of the present invention. FIG. 4 is a view showing a state where the mooring chain is sent out for a predetermined length after the anchor has landed. FIG. 5 is a diagram showing a state where an anchor is embedded in the soil by applying a tensile force to the mooring chain. FIG. 6 is a diagram for explaining a conventional method of laying a mooring chain. FIG. 7 is a diagram for explaining a conventional method of laying a mooring chain, following FIG. 6.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to FIGS.
As shown in FIG. 1, a large floating structure 2 such as an oil plant is moored offshore by a plurality of mooring chains 3. An anchor 4 is provided at the tip of each mooring chain 3. A mooring chain laying facility 1 according to an embodiment of the present invention is for laying a plurality of mooring chains 3 for mooring a floating structure 2 on the seabed.

  As shown in FIGS. 2 and 3, the laying equipment 1 according to this embodiment includes a self-propelled hoist ship 7. The self-propelled hoist ship 7 has a self-propulsion capability and can navigate by itself. The self-propelled hoist ship 7 has a space where a plurality of mooring chains 3 can be loaded on the ship. The self-propelled hoist ship 7 includes a crane 8 that lifts the anchor 4 of the mooring chain 3. The anchor 4 of the mooring chain 3 is connected to the tip of a suspension wire 9 extending from the crane 8 via a connecting device (not shown). For example, when the water depth in the construction sea area is approximately 30 m or more, the suspension wire 9 of the crane 8 and the anchor 4 are connected by a connecting device that can be disconnected by remote operation. On the other hand, when the water depth in the construction sea area is shallower than 30 m and is shallow, the suspension wire 9 of the crane 8 and the anchor 4 are connected by a connecting device that can be manually disconnected by a diver.

  The self-propelled hoist ship 7 includes a fixed point holding device 15. The fixed point holding device 15 is provided in the GPS positioning device 16 that guides (positions) the self-propelled hoist ship 7 to a predetermined position in the construction sea area, and the self-propelled hoist vessel 7. The plurality of propulsion devices 17 are moved to a position and held at the position. The GPS positioning device 16 is capable of grasping the position of the self-propelled hoist ship 7 by receiving signals from a plurality of positioning satellites 19 by a receiver 20 provided in the self-propelled hoist ship 7.

  A plurality of propulsion devices 17 (thrusters) are provided in the self-propelled hoist ship 7. By driving each propulsion device 17 appropriately selected, the self-propelled hoist ship 7 can be propelled in the lateral direction (left-right direction toward the traveling direction by the main power). It is also possible to make a turn based on a certain position by driving each propulsion device 17 appropriately selected. Furthermore, it is also possible to hold the self-propelled hoist ship 7 in a predetermined position by driving each propulsion device 17 appropriately selected.

  The self-propelled hoist ship 7 includes a windlass 23. The windlass 23 is provided exclusively for the mooring chain 3 for mooring the floating structure 2, and is a device for sending out and winding up the mooring chain 3 on the self-propelled hoist ship 7. The windlass 23 is not provided for a chain mooring the self-propelled hoist ship 7. The self-propelled hoist ship 7 includes a remotely operated unmanned submersible (Remotely operated vehicle) (not shown). The unmanned submersible is equipped with an underwater camera. The unmanned submersible is operated by remote control in the self-propelled hoist ship 7.

Next, a method of laying a plurality of mooring chains 3 on the sea floor using the laying equipment 1 according to the embodiment of the present invention will be described.
First, a plurality of mooring chains 3 are loaded on the self-propelled hoist ship 7, and the self-propelled hoist ship 7 is made to sail to the construction sea area by itself. An anchor 4 is connected to each mooring chain 3 via a connecting device.
Next, the self-propelled hoist ship 7 is positioned at a predetermined position in the construction sea area by the fixed point holding device 15. That is, the self-propelled hoist ship 7 moves to a predetermined position in the construction sea area by driving a plurality of propulsion devices 17 provided in the self-propelled hoist ship 7 based on information from the positioning device 16, and then performs a plurality of propulsion. The device 17 is held in that position by driving.

Next, the anchor 4 of the mooring chain 3 is lifted by the crane 8 provided in the self-propelled hoist ship 7, and is moored by the windlass 23 provided in the self-propelled hoist ship 7 while the anchor 4 is suspended in the sea. Send the chain 3 toward the sea. In addition, the mooring chain 3 is sent out into the sea from either the left-right direction toward the traveling direction by the main power of the self-propelled hoist ship 7, for example. At this time, the position and posture of the anchor 4 (in particular, rotation around the suspension wire 9 of the anchor 4) is controlled by crane operation. The position and orientation of the anchor 4 are confirmed directly or indirectly (for example, confirming the tip position of the crane 8) by a positioning device such as GPS.
In this way, the mooring chain 3 is sent out into the sea by the windlass 23, and the anchor 4 is connected to the suspension wire 9 of the crane 4 so that the anchor 4 descends toward the seabed by so-called two-point suspension. The posture of the anchor 4 can be maintained normally. Moreover, by using the windlass 23, the mooring chain 3 can be laid on the seabed without causing twisting or the like.

Next, after anchoring the anchor 4, the unmanned submersible is moved in the sea by the operator operating the self-propelled hoist ship 7, and the anchor 4 is attached by the underwater camera provided in the unmanned submersible. Check the bottom position and the posture when landing. The bottoming position of the anchor 4 and the posture at the bottoming affect the holding force of the mooring chain 3 necessary for mooring the floating structure 2. In addition, if the bottom position of the anchor 4 and the posture at the time of bottoming are not preferable as confirmed by the underwater camera of the unmanned submersible, the grounding position and the posture at the time of bottoming are returned to the work process that can be corrected and laid. Work will start again.
Next, after confirming that the anchor 4 has reached the predetermined position, the connection between the suspension wire 9 of the crane 8 and the anchor 4 by the connecting device is released. When the water depth in the construction sea area is approximately 30 m or more, the connection device is disconnected by remote control. On the other hand, when the water depth of the construction sea area is shallower than 30 m, the connection device is normally manually disconnected by a diver.

Next, from the state of FIG. 4 (a), the propulsion device 17 appropriately selected of the self-propelled hoist ship 7 is driven to move the self-propelled hoist ship 7 in the lateral direction (to the traveling direction by the main power). The mooring chain 3 is sent out for a predetermined length by the windlass 23 along with this movement (state shown in FIG. 4B). Thereby, the installation of one mooring chain 3 on the seabed is completed.
Next, the above-described operation steps are sequentially repeated for the plurality of mooring chains 3 on the self-propelled hoist ship 7, and the laying of all the mooring chains 3 is completed.

  Finally, a holding force test is performed on all mooring chains 3. That is, from the state of FIG. 5A, a tensile force is applied to each mooring chain 3 in the direction of the arrow. As a result, the anchor 4 is buried in the seabed soil (the state shown in FIG. 5B), and has a holding force (resistance force) necessary to moor the floating structure 2 with respect to the mooring chain 3. be able to. In addition, when the attitude | position at the time of bottoming of the anchor 4 is unpreferable, even if it gives tensile force to the mooring chain 3, since the anchor 4 is not buried in soil, it cannot have a predetermined holding force.

  As described above, in the embodiment of the present invention, after the self-propelled hoist ship 7 loaded with a plurality of mooring chains 3 is sailed to the construction area by itself, the self-propelled hoist ship 7 is fixed by the fixed point holding device 15. Can be positioned and held at a predetermined position in the construction sea area. This eliminates the need for a plurality of ships such as a trolley, a hoist ship, and a support ship for navigating them, and does not require a mooring operation for mooring the self-propelled hoist ship 7 as in the prior art. As a result, it is possible to significantly reduce the time required to position and hold the at a predetermined position in the construction sea area, so that the construction cost can be greatly reduced as compared with the conventional case.

  In the embodiment of the present invention, the anchor chain 3 is sent out to the sea by a dedicated windlass 23 while the anchor 4 is suspended in the sea by the crane 8. Thereby, in terms of safety and quality, it is superior to the conventional one. That is, in the embodiment of the present invention, the position and posture of the anchor 4 are controlled by the crane operation while the mooring chain 3 is sent out by the windlass 23, so that the anchor 4 can be bottomed at a normal position and posture. . Moreover, generation | occurrence | production of the twist to the mooring chain 3 can be suppressed, and by extension, the fracture | rupture of the mooring chain 3 can be suppressed.

  Furthermore, in the embodiment of the present invention, the bottom position and bottom posture of the anchor 4 that affect the holding force of the mooring chain 3 are confirmed in advance by the underwater camera provided in the unmanned submersible. Can be efficiently performed.

  DESCRIPTION OF SYMBOLS 1 Laying equipment, 2 Floating structure, 3 Mooring chain, 4 Anchor, 7 Self-propelled hoist ship, 8 Crane, 15 Fixed point holding device, 23 Windlass

Claims (3)

A mooring chain laying method for laying each mooring chain on the sea floor in order to moor a floating structure on the ocean with a plurality of mooring chains,
After the self-propelled hoist ship having self-propulsion capability and capable of loading the plurality of mooring chains is sailed to the construction area by itself, the self-propelled hoist ship is brought to a predetermined position in the construction area by a fixed point holding device. Hold
The anchor of the mooring chain is lifted by the crane of the self-propelled hoist ship and suspended in the sea, and the mooring chain is sent out into the sea by a dedicated windlass provided in the self-propelled hoist ship. Then, after anchoring the anchor and confirming the anchoring position and posture of the anchor with an underwater camera mounted on a remote control unmanned submersible, the result is determined to be good, A method for laying a mooring chain , wherein a tensile force is applied to the mooring chain and the anchor is buried to secure a necessary holding force for the mooring chain.   After anchoring the anchor and separating the anchor from the suspension wire of the crane, the self-propelled hoist ship is moved by itself, and the mooring chain is moved by the windlass with a predetermined length along with the movement. 2. The mooring chain laying method according to claim 1, wherein the mooring chain is sent out.   3. The mooring chain laying method according to claim 1, wherein when the mooring chain is sent out into the sea by the windlass, the position and posture of the anchor are controlled by the crane operation.

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