JPH09193887A - Vibration controlled tank structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress damage of an inner material of a tank due to resonance with external vibration from a propulsion device, etc., by a simple means in a structure of the tank such as oil carrier. SOLUTION: Vessel-like partition members such as an upper vertical pipe 7 and a lower vertical pipe 8 are fixed on an inner material 3 of a tank, and a small hole 9 is formed in respective peripheral wall so that remaining air parts 13, 14 are formed when liquid is collected in the tank. The vibration in the inner material 3 in the tank is suppressed by a function of a dynamic vibration absorber which uses these air parts 13, 14 as spring elements and liquid in the vertical pipes 7, 8 as mass element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tank structure such as an oil tanker ship.

[0002]

2. Description of the Related Art A tank structure of an oil tanker vessel is composed of a hull outer plate 1, a tank inner partition wall 2, a horizontal tank inner structural member 3, etc., as shown in FIG. A stiffener 4 is provided on the outer plate 1 of the hull and a partition wall 2 inside the tank, and a stiffener 5 and an anti-tilt elbow plate 6 are also provided on the structural member 3 inside the tank.

[0003] Here, the lateral tumbling natural circular frequency of the in-tank structural member 3 is generally sufficiently high when there is no water, but there is no problem when the water is full (drainage), which decreases due to an increase in weight due to the water contact effect. In some cases, the propulsion device may exist in the vibration frequency range of the propulsion device, and the horizontal tank internal structure member 3 may exhibit a resonance phenomenon, resulting in damage to the tank internal structure. For this reason, it is necessary to devise a method of separating the lateral tilt natural circular frequency of the structural member 3 in the horizontal tank from the frequency range of the vibration force of the propulsion device of the ship. As a typical example of the conventional method, FIG. As shown, it is possible to increase the rigidity by increasing the fall prevention elbow plate 6 to increase the natural circular frequency of the inner structural member 3.

[0004]

However, in such a conventional method, a large number of tilt-preventing elbow plates 6, which are originally required from the viewpoint of preventing sideways tilt, are added to increase the rigidity. There is a problem that the weight of the structure is increased and the workability is deteriorated. The present invention has been proposed in view of such circumstances, and provides a vibration-proof tank structure capable of preventing an increase in vibration response at the time of contact with water without requiring an additional tilt-stop elbow plate. The purpose is to do.

[0005]

In order to achieve the above-mentioned object, a vibration-proof tank structure of the present invention comprises a tank for liquid storage having a tank internal material and a container fixed to the tank internal material. A container-shaped partition member, and a residual air portion can be formed inside the container-shaped partition member while allowing liquid to enter the container-shaped partition member when the liquid is stored in the tank. A small hole is provided in the peripheral wall portion of the partition member.

[0006] The arrangement and the like of the in-tank structural material and the shape of the container-shaped partitioning member are arbitrarily set. In one embodiment, the in-tank structural material of the tank extends along the inner surface of the tank. It is provided as a horizontal tank internal member made of a plate fixed in the horizontal direction, and the container-shaped partitioning member is provided in the horizontal tank internal member and is configured as a plurality of vertical pipes whose upper ends are closed. The small hole is provided on the peripheral wall of the vertical tube. Further, it is desirable that the plurality of vertical tubes are arranged in pairs so as to have liquid communication portions between them.

The upper and lower vertical pipes, which are vertically paired with each other, are provided as the plurality of vertical pipes, and the upper vertical pipe is
The outer periphery of the skirt is tightly fitted in the opening of the structural member in the horizontal direction and is erected on the structural member in the same tank so as to penetrate to the lower side of the opening, and the lower vertical pipe is the upper vertical pipe. There is a mode in which it is attached to the lower surface of the horizontal tank internal member so as to surround the lower end opening peripheral wall from below. further,
As the plurality of vertical tubes, the horizontal tank is provided with a long vertical tube and a short vertical tube that are arranged side by side on the structural member in the horizontal direction, and the liquid communication portion mutually connects the lower parts of the long vertical tube and the short vertical tube to each other. There is also a form provided as a communicating horizontal pipe, in which the small holes are provided in the lower peripheral walls of the long vertical pipe and the short vertical pipe and in the upper peripheral walls above the horizontal pipe.

When the vertical tube structure as described above is arranged, when the liquid is stored in the tank, the liquid also flows into the vertical tube through the small holes and the air is above each vertical tube. Is enclosed, the effect as a dynamic vibration absorber is generated by the mass of liquid inside each vertical tube and the spring element of residual air. Therefore, the reaction force of the force acting on the vertical pipe structure can suppress the vibration of the horizontal tank structure material.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of an anti-vibration tank structure according to the present invention will be described with reference to the drawings. FIG. 1 is a lateral cross-sectional view of a main part of the anti-vibration tank structure as the first embodiment.
FIG. 4 is a lateral cross-sectional view of an essential part of a vibration-proof tank structure as a second embodiment, and FIGS. 3 and 4 are schematic views illustrating the mechanism of the first embodiment and the second embodiment, respectively.

In the first embodiment shown in FIG. 1, a liquid storage tank in an oil tank ship is formed inside a hull outer plate 1 so as to be partitioned by a partition wall, and a horizontal plate connected to the outer plate 1 and the partition wall. Directional tank internal structure 3 is provided, and for vibration isolation of the tank internal structure 3, an upper vertical pipe 7 and a lower vertical pipe 8 as a container-shaped partitioning member having a small hole 9 in a peripheral wall portion The upper air portion 13 and the lower air portion 14 as residual air portions can be formed as shown in FIG. That is, the upper vertical pipe 7 is erected on the internal structure member 3 of the tank so that the outer periphery of the skirt is tightly fitted to the opening of the internal structure member 3 of the horizontal direction and penetrates to the lower part of the same. Vertical tube 8 is upper vertical tube 7
It is attached to the lower surface of the horizontal tank internal structural member 3 so as to surround the lower end opening peripheral wall from below.

Further, in the vibration-proof tank structure as the second embodiment of the present invention, as shown in FIG. 2, in the liquid storage tank formed inside the hull outer plate 1 of the oil tanker vessel, the horizontal tank is used. A long vertical pipe as a container-shaped partition member for the inner structural material 3.
10 and a short vertical pipe 11 are arranged side by side in a pair, and horizontal pipes 12 are provided to connect the lower portions of the vertical pipes 10 and 11 to each other, and the vertical pipes 10 and 11 are closed. In order to accurately form the upper air portion 13 and the lower air portion 14 as the residual air portion at the upper end portion when storing the liquid in the tank, as shown in FIG. A hole 9 is formed. That is, the small holes 9 are formed in the lower peripheral walls of the long vertical pipes 10 and the short vertical pipes 11 and in the upper peripheral walls above the horizontal pipes 12, respectively.
Are formed.

Here, when the liquid is stored in the tank structure, in both the first and second embodiments, the inside of each of the vertical pipes 8 to 11 and the communication pipe are provided through the small holes 9. The liquid also flows into the horizontal pipe 12. However, a part of the air inside each of the vertical tubes 8 to 11 remains inside the vertical tubes and is compressed by the liquid to be enclosed in the upper portion of each vertical tube. That is, as shown in FIGS. 3 and 4, in the first embodiment, the upper air portion 13 is formed at the upper end portion of the upper vertical pipe 7, and the lower air portion 14 is formed at the upper end portion of the lower vertical pipe 8. Also the second
In the embodiment, the upper air portion 13 and the short vertical pipe are provided at the upper end of the long vertical pipe 10.
Lower air portions 14 are formed on the upper ends of the respective portions 11.

At this time, a one-degree-of-freedom system is formed in which the enclosed air remaining in each of the air portions 13 and 14 serves as a spring element and the liquid in the vertical pipe and the horizontal pipe serves as a mass element. The natural circular frequency ω ₀ of this vibration system is given by the formula [1].

## EQU1 ## ω ₀ = √ {G (1 + α) + K / ρ (P ₁ / h ₁ + P ₂ / h ₂
Α)} / (H ₁ + αH ₂ + βL) where α = A ₁ / A ₂ , β = A ₁ / a where H ₁ and A ₁ are the water level and disconnection of the upper vertical pipe 7 or the long vertical pipe 10. Area H ₂ , A ₂ : Water level and cross-sectional area of lower vertical pipe 8 or short vertical pipe L, a: Distance between upper vertical pipe 7 and lower vertical pipe 8 and cross-sectional area of open hole between both vertical pipes (In the case of the first embodiment): Horizontal pipe
Length and cross-sectional area of 12 (in the case of the second embodiment) P ₁ , h ₁ : pressure and height of the upper air portion 13 P ₂ , h ₂ : pressure and height of the lower air portion 14 (above FIG. 3 and (See Fig. 4) K: Specific heat ratio of air ρ: Density of liquid G: Gravitational acceleration Then, the dimensions of the vertical tubes 7, 8, 10, 11 and the height of the small holes 9 are obtained by the formula [1]. Natural circular frequency ω _{0 of} vertical tube structure
Is set so as to match the natural circular frequency of the sideways vibration of the structural member 3 in the horizontal direction.

Now, considering the case where the horizontal tilt natural circular frequency of the horizontal tank structure member 3 resonates, the exciting force F in this case and the horizontal tilt direction of the horizontal tank structure member 3, that is, the vertical up and down direction. The relationship with the directional vibration displacement y is shown in (a) and (b) of Fig. 5.
As shown in the figure, the phase of the vibration displacement y is 90 ° with respect to the excitation force F.
Be late. Next, the vibration displacement x of the center of gravity of the liquid in the vertical pipe, which is induced by the vibration displacement of the structural material 3 in the horizontal tank, resonates in the vibration system formed by the liquid in the vertical pipe as described above. As shown in (c), the phase is delayed by 90 ° with respect to the vibration displacement y of the horizontal tank structure member 3. At this time, if the inertial force generated in the liquid in the vertical pipe is F _I , its reaction force F _C
Acts on the structural member 3 in the horizontal direction.

Here, F _I and F _C are obtained by the equations [2] and [3].

[Formula 2] F _I = M · (d ² x / dt ² )

[Equation 3] F _C = −F _I However, M: Effective mass of the liquid in the vertical tube structure [Equation 2] and [Equation 3] Equation [Equation 4] is established.

## EQU4 ## F _C = -F _I = M (d ² x / dt ² ) = Mω ² x where ω is the horizontal tilt natural circular frequency of the horizontal tank structure member 3

That is, from the equation [4], the acting force F _C and the vibration displacement x of the center of gravity of the liquid in the vertical pipe are in the same phase as shown in FIG. 5 (d). Summarizing the above, as shown in FIG. 5, the acting force F _C has a phase opposite to the exciting force F. Therefore, since the acting force F _C acts in the direction of canceling the exciting force F, the effective exciting force F + F _C becomes smaller than the actual exciting force F.
Therefore, the vibration response of the horizontal tank structure member 3 can be reduced as compared with the case where the vertical tube structure is not provided.

The effect of the present invention as described above is schematically shown in FIG. 6 in comparison with the effect of the conventional method. In the figure,
The broken line 15 is a curve representing the vibration acceleration of the structural material in the horizontal tank of the unmeasured structure, the one-dot chain line 16 shows the case of the conventional countermeasure structure in which the fall prevention elbow plate 6 is added, and the solid line 17 is the vibration damping of the present invention It shows the case of a mold tank structure. In the structure based on the conventional measures, a large number of tilt-preventing elbow plates 6 are required to increase the natural circular frequency, and there is a possibility that the new natural circular frequency resonates with another vibration force. It was In contrast,
With the tank structure of the present invention, the vibration response can be suppressed as a whole, and there is no concern about a resonance phenomenon with another vibrating force, and this is also effective.

[0018]

As described above, according to the vibration-proof tank structure of the present invention, a small hole is formed in the peripheral wall of the container-shaped partition member fixed to the internal structure of the tank so that the above-mentioned container can be stored when the liquid in the tank is stored. Since the residual air portion can be formed inside the cylindrical partitioning member, the vibration response of the in-tank structural material can be suppressed as a whole, and the occurrence of damage due to the resonance phenomenon of the in-tank structural material can be reduced compared to the conventional method. It can be prevented by a simple means while maintaining high reliability. Further, by adopting a vertical pipe as the container-shaped partitioning member, the work of mounting the vertical pipe on the in-tank structural material is facilitated, and it can be easily applied not only to a new ship but also to an existing oil tank ship. Then, a plurality of vertical pipes are communicated with each other and are arranged side by side on the structural member in the tank in pairs such as long vertical pipes and short vertical pipes, or in upper and lower vertical pipes such as upper and lower vertical pipes. Equipped,
The cooperative action of the residual air portions has the effect of more accurately performing the vibration damping action on the structural members in the tank.

[Brief description of the drawings]

FIG. 1 is a lateral cross-sectional view of a main part of a vibration-proof tank structure according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a main part of a vibration-proof tank structure according to a second embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating a mechanism of the tank structure of FIG.

FIG. 4 is a schematic diagram illustrating a mechanism of the tank structure of FIG.

5 (a) and 5 (b) are all diagrams for explaining the operation of the vibration-proof tank structure of the present invention.

FIG. 6 is a diagram comparing the effect of the anti-vibration tank structure of the present invention with a conventional method.

FIG. 7 is a horizontal sectional view showing a main part of a conventional tank structure.

FIG. 8 is a sectional view taken along the line AA in FIG. 7;

[Explanation of symbols]

 1 Hull outer plate 2 Tank inner partition wall 3 Horizontal tank inner structure 4, 5 Stiffener 6 Tilt-stop elbow plate 7 Upper vertical pipe 8 Lower vertical pipe 9 Small hole 10 Long vertical pipe 11 Short vertical pipe 12 Horizontal pipe 13 Upper part Air part 14 Lower air part 15 Vibration response curve of in-tank structural material of unstructured structure 16 Vibration response curve of in-tank structural material of conventional countermeasure structure 17 Vibration response curve of in-tank structural material of the present invention structure

Claims (5)

[Claims] 1. A liquid storage tank is provided with an internal tank structural member, and a container-shaped partition member fixed to the internal tank structural member. When the liquid is stored in the tank, the internal container member is placed inside the container-shaped partition member. A small hole is provided in the peripheral wall portion of the container-shaped partition member so that a residual air portion can be formed inside the container-shaped partition member while allowing the liquid infiltration. Tank structure. 2. The anti-vibration tank structure according to claim 1, wherein the tank inner structural member is provided as a horizontal tank inner structural member made of a plate-like member fixed horizontally along the inner surface of the tank. The container-shaped partitioning member is provided as a plurality of vertical pipes equipped with the horizontal tank internal member and closed at the upper end, and the small holes are provided in the peripheral wall of the vertical pipes. Anti-vibration tank structure. 3. The vibration-proof tank structure according to claim 2, wherein the plurality of vertical tubes are arranged in pairs so as to have liquid communication portions between them.
Anti-vibration tank structure. 4. The anti-vibration tank structure according to claim 3, further comprising an upper vertical tube and a lower vertical tube which are vertically paired as the plurality of vertical tubes, the upper vertical tube being the horizontal tank. The bottom of the upper vertical pipe is opened at the lower end of the upper vertical pipe while the outer periphery of the skirt is tightly fitted into the opening of the internal structural member and penetrates to the lower side of the opening. An anti-vibration tank structure, characterized in that it is attached to the lower surface of the horizontal tank structure so as to surround the peripheral wall from below. 5. The vibration-damping tank structure according to claim 3, further comprising a long vertical pipe and a short vertical pipe, which are arranged in parallel on the horizontal tank internal structural member, as the plurality of vertical pipes. A communicating portion is provided as a horizontal pipe that communicates the lower parts of the long vertical pipe and the short vertical pipe with each other, and the small holes are more than the lower peripheral walls of the long vertical pipe and the short vertical pipe and the horizontal pipe. An anti-vibration tank structure, which is provided on each upper peripheral wall above.