JPS5932582A - Mooring method of buoyant body and apparatus thereof - Google Patents

Abstract

PURPOSE:To keep off the breakdown of a mooring rope, by installing an intermediate sinker, which is variable in its buoyancy, in an intermediate part of a mooring rope securing a buoyant body to a mooring point at the sea bottom, while increasing the buoyancy of the intermediate sinker as soon as mooring rope tension increases. CONSTITUTION:Each intermediate sinker 2 being variable in its buoyancy is installed in an intermediate part of a mooring rope 1 securing a buoyant body A to a mooring point B at the sea bottom. The intermediate sinker 2 has a buoyancy chamber inside and is variable in the capacity of its buoyancy chamber according to the tension, owing to the diaphragm of the buoyancy chamber connected to each of mooring ropes 1a and 1b. When the buoyant body A shifts in a direction going away from the mooring point B and tension acting on the mooring rope 1 increases, buoyance in the intermediate sinker 2 is increased whereby the intermediate sinker 2 goes upward, loosening the tension of the mooring rope 1. According to this method, the breakdown of the mooring rope due to waves, etc., can be effectively prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for mooring a floating body and an apparatus for implementing this method.

Various methods have been known for mooring floating bodies. That is, there are methods of mooring using a chain or the like for the mooring line and utilizing its weight, and methods of providing an intermediate buoy or intermediate sinker on the mooring line and mooring using the buoyancy and weight of these. In any case, the floating body is moored at a position that balances the mooring force exerted on it by wind pressure, tidal currents, etc. At this time, the mooring tension acting on the mooring line increases as the floating body moves away from the mooring point, and the increase is rapid when the mooring line is under tension. In addition to the above-mentioned drifting force, the floating body is subjected to motion displacement due to waves. Although this displacement is smaller than the displacement due to drifting force, it is repeated and changes rapidly. Therefore, when the floating body is moored far away from the mooring point and the mooring lines are under tension, if the floating body is subjected to wave displacement, the mooring lines will be subjected to a significant cyclic load, which will cause Mooring lines may break.

An object of the present invention is to provide a method and device for mooring a floating body that has mooring characteristics such that the mooring tension does not suddenly increase with respect to the displacement of the floating body, thereby preventing the mooring cable from breaking due to waves or the like. There is a particular thing.

In order to achieve the above object, the present invention provides an intermediate sinker with variable buoyancy in the middle of a mooring line that connects a floating body to a mooring point on the seabed, so that the floating body moves in a direction away from the mooring point and is moored. The invention is a method of mooring a floating body by increasing the buoyancy of an intermediate sinker when the tension acting on the cable increases. The buoyancy chamber consists of a first mooring line that connects the intermediate sinker and the floating body, and a $2 mooring line that connects the intermediate sinker and the floating body. When the tension acting on one end of the first and second mooring ropes increases, the moving part of the buoyancy chamber increases. It is attached to a movable part so that it can be moved in the direction of increasing volume.

According to this invention, when the floating body moves and the mooring line becomes tense, the tension acting on it increases, but as the tension of the mooring line increases, the buoyancy of the intermediate sinker increases.
The intermediate sinker floats up and loosens the tension on the mooring line, which suppresses the increase in tension on the mooring line, and provides mooring characteristics with a smaller rate of increase in tension relative to the displacement of the floating body compared to conventional ones. It is possible to prevent the mooring line from breaking due to waves or the like.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the moored state of the floating body.

The floating body (A) is tied to a mooring point (B) on the seabed by a mooring line (1) via an intermediate sinker (2). The mooring lines (1) include a first mooring line (1a) that connects the mooring point (inside the mooring point) and the intermediate sinker (2), and a second mooring line (113) that connects the intermediate sinker (2) and the floating body. ).

FIG. 2 shows the detailed structure of the intermediate sinker (2).

The intermediate sinker (2) is a buoyancy chamber with variable volume! 21) with variable buoyancy and consists of a cylindrical sinker body @ and two movable parts on the left and right. The sinker body has a thick peripheral wall so as to be a heavy part. The left and right movable parts (to) are both cylindrical with a bottom, and are slidably fitted onto the inner circumferential surface of the sinker body with their respective openings facing inward. In this way, a closed space is formed inside the sinker body by the left and right movable parts (to), creating a buoyancy chamber (2D) with variable volume.The sinker body has brackets (241 A sliding axial force is provided for each of the movable parts.
The first and second mooring lines (I
a) One end of (Ib) is attached to each. When these mooring lines (la) and (lb) are pulled in opposite directions, the left and right movable parts @ move in the direction away from each other.

This increases the volume of the buoyancy factor) and the intermediate sinker (
2) Buoyancy increases.

FIG. 3 shows a modification of the intermediate sinker. In this modification, a spring that acts as a restoring force for the movable parts is installed inside the buoyancy chamber (211).Instead of this spring, the movable parts move in the direction of separating them from each other. Other elastic materials may be provided that have the function of

Now, as the floating body (5) moves away from the mooring point (of the mooring point), the mooring line (1) becomes taut and the tension acting on it increases. When this tension increases, the buoyancy of the intermediate sinker (2) increases as described above, so the intermediate sinker (2) floats up and the tension on the mooring line (1) is relaxed.

This acts to reduce the tension in the mooring line (1). This suppresses an increase in the tension of the mooring rope (1).

In addition, in the second embodiment, the case where one intermediate sinker is installed has been described, but the present invention is not limited to this, and as shown in FIG. It is also possible to provide an intermediate sinker (2).

The above-mentioned tension increase suppressing effect will be explained in more detail using a simple model shown in FIG. Assuming that the horizontal change of the floating body (8) is ΔX1, the underwater weight of the intermediate sinker (2) is W1, the force that pulls the floating body (8) in the horizontal direction is Tx, and the tension of the mooring rope is T, the following relational expressions are derived. However, the mooring ropes have the same length, l, and the angle with the vertical line is θ.

Tx--fist tanθ---t21 ΔX"" 21-s inθ 0.・(
3) Here, the buoyant force of the intermediate sinker (2) is B, and if this buoyant force B is proportional to the tension T of the mooring line (1) as shown in the following equation (5), then the intermediate sinker (2) The underwater weight W of is shown by Kaya 6 formula.

B yo -T ---+51W=W
A- to T---(6 squares, WA
is the true weight of the intermediate sinker (2).

When Kaya's six expressions are substituted into the first to second and fourth expressions and rearranged, each relational expression is transformed as shown below.

Also, from the first equation and the seventh equation, the first equation that shows the change in the underwater weight W
Equation 0 is derived.

Here, we derive the 11th equation with the 7th equation as θ-20.

Then, the tension T of the mooring rope and its horizontal component 6 and 7. By changing the value of 42 in this way, that is, by changing the weight of the intermediate sinker, the mooring characteristics can be changed.

Figure 8 shows the mooring characteristics obtained in this way, with the horizontal axis representing the displacement of the floating body from the mooring point (ΔX), and the vertical axis representing the force pulling the floating body in the horizontal direction (TX), and the relationship between the two. In Fig. 8, the curve cA)Φ) shows the case where the underwater weight of the intermediate sinker is constant and its size varies.

Curve G), on the other hand, shows the case where the buoyancy of the intermediate sinker changes from small to large and therefore its underwater weight changes from large to small. These curves GA) CB) (C
), curve (C) has a gentle slope compared to curve (A) (13). This means that
This shows that the rapid increase in tension due to the movement of the floating body is suppressed, and the mooring property has a small tension increase rate in response to changes in the floating body. Therefore, even if the floating body is displaced by waves, etc., the mooring The width of the repeated load acting on the cable is reduced, and its breakage is prevented.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is a side view showing a floating body in a moored state, FIG. 2 is a sectional view of a vertical joint of an intermediate sinker, and FIG. 3 is a sectional view of the same showing a modified example of the intermediate sinker. , Fig. 4 is a side view showing other mooring conditions, Fig. 5 is an explanatory diagram of the mooring model, Figs. 6 and 7 are graphs showing changes in mooring characteristics, and Fig. 8 is a graph showing mooring characteristics. be. (1) 0. Mooring rope ((1aX1b)e...first and second mooring rope), +2) I.. Intermediate sinker, C1).
Φ・buoyancy chamber, (support) l・sinker body, I2:3)...
・Movable parts, (tilt...floating body, (B)...mooring point. Applicants for the above patents: 4 people other than Hitachi Zosen Corporation. 5. Figure 6. Figure 7. Figure 8.

Claims (2)

[Claims] (1) An intermediate sinker (2) with variable buoyancy is installed in the middle of the mooring line (1) that connects the floating body (5) to the mooring point CB) on the seabed, so that the floating body (5) can be moved far away from the mooring point CB). A method for mooring a floating body, in which the floating body (5) is moored by increasing the buoyancy of the intermediate sinker (2) when the tension acting on the mooring line (1) increases as it moves in that direction. (2) An intermediate sinker (2) having a buoyancy chamber (21), a first mooring line (1a) connecting this intermediate sinker (2) and a mooring point CB on the seabed, and a first mooring line (1a) connecting the intermediate sinker (2) and a floating prisoner. and a second mooring rope (1b) that connects the
The buoyancy chamber CD above is the sinker body.
It is formed to have a variable volume by a movable part that is movably provided on the first and second mooring lines (la) (
At least one end of at least one of lb) is attached to the movable part c23) so as to move the movable part c23) in a direction in which the volume of the buoyancy chamber t21+ increases when the tension acting on the movable part c23) increases. A mooring device for a floating body.