JPH0736660B2 - Submarine cable lifting method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for raising a submarine cable to an offshore, for example, a tower-like base.

[Prior Art] The conventional method was as follows (Figs. 4a and 4b).

In Figs. 4a and 4b, 12 is a seabed, 14 is the surface of the water, and 16 is a model of an offshore base (such as a steel tower). Cables are raised here. 18 is a winch, which is installed at the base 16 and used for raising the cable.

20 indicates a submarine cable, and 22 indicates a tube buoy (hereinafter referred to as a buoy).

The left side is the sending side of the submarine cable 20.

(1) First, when a submarine cable 20 is unwound and attached from a laying ship (not shown) to the submarine 12 and when it comes to an appropriate position near the starting point of the base 16, buoys 22 are attached to the submarine cable 20 at intervals of 2-3 m. The submarine cable 20 having the required length is attached and fed out by a caterpillar (not shown) to float on the water surface 14.

(2) Then, the tip of the submarine cable 20 is guided to the starting point of the base 16 by the outboard motor boat 30.

(3) While removing the buoy 22, the submarine cable 20 is lifted by the winch 18 installed above the base 16.

(4) Remove the last remaining buoy 22 from offshore (on the left side in the figure) in order to sink the submarine cable 20.

[Problems to be Solved by the Invention] (1) Since the buoyancy of the buoy 22 is small, the buoy 22 sinks into the water on the side where the buoy is attached.

When submerged, the volume is reduced by the water pressure, the buoyancy is further reduced, and the submarine cable 20 is further submerged, as shown in FIG. 4b.

(2) The buoy 22 in the A section (the buoy 22 is on the water surface 14) can be removed by normal (onshore) workers, but in the B section (buoy).
The buoy 22 (22 is underwater) can be removed only by a diver.

(3) When the water is deep (40 m or more), the buoy 22 near the seabed 12 cannot be removed by the surface diver, and a saturation diver is required.

Saturation divers are extremely limited in working time and working range, and work efficiency is greatly reduced.

Also, for example, a saturation diver who dive to a depth of 70 m cannot float up to a depth of 40 m to work (because of a diving disease).

Also, as mentioned above, the working range of the surface diver is up to a water depth of about 40 m. As a result, an irremovable buoy 22 may appear.

(4) In consideration of the above, the present invention allows the submarine cable to be attached without the help of a diver.

[Means for Solving the Problem] As shown in FIGS. 1a to 1d, (1) If it is assumed that a laying ship (not shown) goes straight, a submarine cable 20 to be laid out is located offshore. (2) Attach a large buoyancy buoy 24 that can hold the weight of the undersea cable 20 from the seabed 12 to the water surface 14 to the seabed cable 20 at the position where it is expected to reach the sea surface at the rising point D of (3) and then It is characterized in that the buoy 22 is attached only first and floated on the water surface 14.

[Explanation] (Figs. 1a to 1d) (1) As shown in Fig. 1a, the submarine cable 20 was unwound from a laying ship (not shown) and was attached to the base 16 while the submarine cable 20 was being installed. Similarly, the direction is changed when an appropriate position C before the standing point D is reached.

Then, at the point E where CD = CE, a large buoyancy buoy 24 is attached to the submarine cable 20.

In the past, the buoy 22 was attached from around the C point,
In this case, do not attach the buoy until the point E is reached.

(2) About the buoyancy of the large buoyancy buoy 24: As mentioned above, the submarine cable 20 from the seabed 12 to the water surface 14
Shall be able to hold the weight of.

That is, assuming that the water depth is am and the weight of the submarine cable 20 in water is b kg / m, one having a buoyancy of a · b kg or more is used.

For example, a cable of 6.6 kV × 3,240 mm ² has b = 20 kg / m. Therefore, if the water depth is a = 70 m, use buoyancy of 1400 kg or more.

Specifically, a hollow fender can be used.

(3) Then, for the submarine cable 20 (right in Fig. 1a), while attaching buoys to the submarine cable 20 at intervals of 2 to 3 m as usual, the submarine cable 20 is fed with a caterpillar,
Float the entire submarine cable 20 of the required length on the water surface 14 (No. 1a
Figure).

(4) Attach the tip of the submarine cable 20 to the base 16 by the outboard motor boat 30.
To the standing point D of No.18 and remove the buoy 22 while
Raises the submarine cable 20 to the base 16 (Fig. 1b,
This is the same as before). Reference numeral 19 indicates a wire for pulling up.

(5) Only the large buoyancy buoy 24 remains at the end (Fig. 1c),
Then remove it and sunk the submarine cable 20 to complete the installation without the help of a diver (Fig. 1d).

[Mounting position of large buoyancy buoy 24] As described above, the large buoyancy buoy 24 is shown in Fig. 1a as CD = CE.
It is important to attach it to the position where If this position is not good, the following problems will occur.

(1) As shown in Fig. 2a, if CE '<CD: Even after the submarine cable 20 has been lifted up, the submarine cable 20 with the buoy 22 remains on the water surface 14 (Fig. 2b).

This buoy 22 can be removed by a normal worker (not a diver).

However, when the buoy 22 is removed, the result is as shown in Fig. 2c, and when the large buoyancy buoy 24 is removed in this state, the submarine cable 20
There is a high possibility that a kink will occur (because the submarine cable 20 has a curl).

(2) In case of CE ″> CD as shown in Fig. 3a: The submarine cable 20 has been lifted up and before the large buoyancy buoy 24 is removed, a kink has already occurred in the submarine cable 20 as shown in Fig. 3b. There is a possibility that

[Advantages of the Invention] Assuming that a laying ship is going straight, if the submarine cable to be unwound and laid is expected to reach the sea surface at the uplifting point of the offshore base, the submarine cable will be moved from the seabed to the water surface. Since a large buoyancy buoy capable of holding the weight of the submarine cable up to is attached, and then a normal buoy is attached only first to float on the water surface, the following effects are obtained.

(1) When the submarine cable 20 has been lifted up, all buoys 22 have been removed and the large buoyancy buoys 24 are at the base.
You are at the point of contact with 16 rising points D.

Moreover, the length of the submarine cable 20 on the delivery side from the large buoyancy buoy 24 is in a state of no excess or deficiency. Therefore, in that state, the large buoyancy buoy 24 can be immediately removed. Even if the large buoyancy buoy 24 is removed, there is no concern that a kink will occur in the submarine cable 20.

(2) The cable on the sending side from the large buoyancy buoy 24 has a buoy.
Since 22 is not attached, neither the saturation diver nor the surface diver is required even in the deep sea, and there is no restriction on the raising of the cable.

(3) All buoys 22 that must be removed are on the water surface
Since it is in 14, it can be removed by ordinary workers and does not require a diver.

[Brief description of drawings]

FIGS. 1a to 1d are explanatory views showing an embodiment of the method of the present invention in the order of steps, FIGS. 2a to 2c are explanatory views when the mounting position of the large buoyancy buoy 24 is inappropriate, 3a and 3b are explanatory views of another case where the mounting position of the large buoyancy buoy 24 is improper, and FIGS. 4a and 4b are explanatory views showing the conventional construction method in the order of steps. 12: Seabed, 14: Water surface, 16: Base 18: Winch, 20: Submarine cable, 22: Buoy 24: Large buoyancy buoy, 30: Outboard motor boat

Claims (1)

[Claims] 1. When a submarine cable is unwound from a laying ship and laid, and when it reaches an appropriate position near the launching point of an offshore base, a buoy is attached to the submarine cable to cover the entire length of the submarine cable on the water surface. Floating the submarine cable at the base of the base by an outboard motor boat; lifting the submarine cable to the base while removing the buoy; removing the remaining buoy In the submarine cable hoisting method including the step of sinking the submarine cable, when assuming that the laying ship goes straight ahead, the submarine cable to be laid out is laid on the sea surface at the hoisting point of the offshore base. At the position you expect to reach,
A large buoyancy buoy that can hold the weight of the submarine cable from the seabed to the water surface is attached to the submarine cable, and then the buoy is attached only first to float on the water surface,
Submarine cable hoisting method.