JPH08295286A - Tank construction of tanker - Google Patents

Abstract

PURPOSE: To enable it to control any vibration in the sidelong tilting direction of a tank internal structural member in making an L-shaped pipe function as a dynamic vibration damper in time of the rolling or pitching of a tanker by attaching this L-shaped pipe, where one end of a horizontal pipe part is communicatingly connected to, and its lower end is opened, tight to somewhat the lower part of both symmetrical corner parts of an upper coaming for this tank internal structural member. CONSTITUTION: A tank construction of this tank has a tank internal structural member 3 extending on a transversal vertical plane welded with an outer end ranging over an upper deck 1 and a tank inner bulkhead 2, while plural stages of horizontal rectangular anti-bending members 4 and 5 are installed there. An L-shaped pipe conisting of one vertical pipe part 7 and a horizontal pipe part 8 being almost the same type whose one end opening is communicatingly attached tight to a lower opening of the former, and the other end is opened, is attached tight to somewhat the lower part of both symmetrical comer parts of an upper coaming of the tank internal structural member 3. With this constitution, when a liquid is stored in the tank, it is made to flow into the L-shaped pipe from the lower opening, and thereby air is sealed in an upper end of this L-shaped pipe, whereby this L-shaped pipe is made to function as a dynamic vibration damper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tanker tank structure.

[0002]

2. Description of the Related Art The tank structure of a tanker is conventionally shown in FIG.
A single hull as shown in the cross section (A) and a double hull as shown in FIG. In both tank structures, the tank is designed with consideration of the liquid pressure of the liquid to be loaded in the tank, and the dimensions of the outer plate, tank inner partition wall, tank inner structure and stiffener are the ones at the bottom of the tank. Is larger than the top of the tank, making it difficult to vibrate,
The upper part of the tank is relatively easy to vibrate. Here, the connecting portion VI between the outer plate (upper deck) and the tank inner bulkhead
As shown in the enlarged view of FIG. 7, the part I is composed of an upper deck 1, a tank inner partition wall 2 and a tank inner structural member 3. A stiffener 4 is provided on the upper deck 1 and the inner partition 2 of the tank, and a stiffener 5 and an anti-tilt elbow 6 are also provided on the in-tank structural member 3.
In this type of tanker, the swaying natural circular frequency of the in-tank structural member 3 is generally sufficiently high when the liquid is empty, and there is no problem. Since there is a case where the propulsion device has an exciting force frequency range, the tank structure 3 may be liable to resonate due to sideways vibration and damage the tank structure. In order to prevent such damage to the tank structure,
It is necessary to devise to separate the lateral tilt natural circular frequency of the in-tank structural member 3 from the vibration frequency range of the propulsion device of the ship. Conventionally, as shown in FIG. By increasing the elbow plate 6 and increasing the rigidity, the natural circular frequency is increased.

[0003]

However, in such a conventional tank structure, a large number of the tilt-preventing elbow plates 6 are required in comparison with the tilt-preventing elbow plates 6 originally required from the viewpoint of preventing the sideways falling. Therefore, the weight of the tank structure is increased and the workability is deteriorated.

The present invention has been proposed in view of the above circumstances, and does not require the addition of an anti-tilt elbow plate.
It is an object of the present invention to provide an economical tanker tank structure that reduces the weight by preventing the natural circular frequency from decreasing when it comes into contact with liquid.

[0005]

In order to achieve such an object, the invention of claim 1 is such that the outer end is welded over both members of the upper deck of a tanker for storing or transporting liquid and the tank inner partition. The tank internal member extending on the horizontal horizontal plane and the three sides extending in parallel along the three members are welded to the tank internal partition wall, the tank internal member and the tank internal member inner end combing, respectively. In a tank formed of a plurality of horizontal rectangular stiffeners, each of which is fixed slightly below the right and left corners of the upper combing of the structural member in the tank and has a substantially same diameter extending in the front-rear direction at the lower end of the vertical pipe part. It has an L-shaped pipe in which one end of the horizontal pipe portion is connected in communication and the upper end is closed and the lower end is opened. When the tanker sways, the L-shaped pipe acts as a dynamic vibration absorber. It is characterized by

The invention of claim 2 is the same as that of claim 1, in which the following formula (1) is applied from the closed upper end of the vertical tube portion of the L-shaped tube.
It was equipped with a small hole that was drilled down by a height H determined by (however, ω ₀ = √ {[2G + K · (P ₀ + ρGD) ² / ρP ₀ H] / (l _L + aL / A )} (1) where, a: cross-sectional area of the vertical pipe portion l _L : length of liquid column of the vertical pipe portion A: cross-sectional area of the horizontal pipe portion L: length of the horizontal pipe portion 8 D: Depth from the liquid level of the liquid in the tank to the liquid level of the liquid 12 remaining in the L-shaped pipe G: Gravity acceleration H: Depth from the upper end of the vertical pipe portion 7 to the small hole 10 K: Air Specific heat ratio P ₀ : atmospheric pressure ρ: density of the liquid 12 ω ₀ : natural circular frequency of the liquid column in the L-shaped tube).

[0007]

According to this structure, by disposing the L-shaped pipe, when the liquid is stored in the tank, the liquid flows into the L-shaped pipe from the lower end opening and each vertical pipe portion thereof. Since air is enclosed in the upper end of this L-shaped tube,
The effect as a dynamic vibration absorber occurs when the hull is pitched. Therefore, the reaction force of the force acting on the L-shaped pipe can suppress the vibration of the in-tank structural member in the sideways direction.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a front view showing an upper end corner portion of a structural member in a tank, FIG. 2 is a side view taken along the line II-II of FIG. 1, and FIG. 2 is an explanatory view showing the action of the L-shaped tube as a dynamic vibration absorber, FIG. 4 is a diagram showing changes over time in mechanical quantities acting on the respective members of FIG. 1, and FIG. 5 is L of FIG. FIG. 6 is a diagram showing the relationship between the frequency of vibration due to the V-shaped tube and the vibration acceleration of the structural members in the tank.

In the above drawing, the same reference numerals as those in FIG. 7 indicate the same members as those in the same drawing. First, in FIGS. 1 and 2, each of the L-shaped pipes on the port side and the starboard side is of equal length. The vertical pipe portion 7 is composed of a vertical pipe portion 7 and a horizontal pipe portion 8 of which the one end opening is fixedly connected to each lower end opening thereof and the other end is opened. It is fixed on the vertical vertical plane of the in-tank structural member 3 near the top of No. 3.

Here, the upper ends of the vertical tube portions 7 are closed. Further, the vertical pipe portion 7 and the horizontal pipe portion 8 are provided with small holes 10 as shown in FIG. As shown in the figure, the small holes are basically provided at the outer communication portion between the vertical pipe portion 7 and the horizontal pipe portion 8 or at an intermediate position of the vertical pipe portion 7, but other places may be provided as needed. Can also be provided. When the liquid 9 is stored in such a tank, the liquid 9 flows into the L-shaped pipe from the open end of the horizontal pipe portion 8. However, since the upper end of the vertical pipe portion is closed, the air remains inside the upper end of the vertical pipe portion 7, and is compressed by the liquid pressure of the liquid 9 and enclosed in the upper end portion of the vertical pipe portion 7.

In such an L-shaped tube, as shown in FIG. 3, a one-degree-of-freedom vibration system in which the remaining enclosed air 11 is used as a spring element and the liquid 12 in the L-shaped tube is used as a mass element is formed. It The natural circular frequency ω ₀ of this vibration system is given by the equation (1) assuming that the structure has a bilaterally symmetrical structure for simplicity. ω ₀ = √ {[2G + K ・ (P ₀ + ρGD) ² / ρP ₀ H] / (l _L + aL / A)} (1) where a: cross-sectional area of the vertical tube portion 7 l _L : vertical Length of liquid column of pipe portion A: Cross-sectional area of horizontal pipe portion L: Length of horizontal pipe portion D: From liquid surface of liquid in tank to liquid surface of liquid 12 remaining in L-shaped pipe Depth G: Gravitational acceleration H: Depth from the upper end of the vertical tube portion 7 to the small hole 10 K: Specific heat ratio of air P ₀ : Atmospheric pressure ρ: Density of liquid 12 ω ₀ : Liquid column in L-shaped tube Is the natural circular frequency of). According to the equation (1), the dimensions of the vertical pipe portion 7 and the horizontal pipe portion 8 and the small holes 10 are adjusted so that the natural frequency of the L-shaped pipe matches the natural frequency of the lateral falling vibration of the in-tank structural member 3. The position and tank level have been determined. Further, H can be obtained by back calculation if the set natural frequency ω ₀ is determined in the equation (1). Here, the position H of the small hole 10 is 0 <H <Hmax.
(Fig. 3) is selected. However, the position of this small hole determines the initial volume of the enclosed air, and this has an important effect that the resonance frequency of the liquid column of the L-shaped tube can be determined.

[0012] Considering a case where the natural frequency of the tank structural member 3 is resonated due to the fluctuation of the liquid coin caused by the pitching while the tanker is moving, if the vibration force in this case is F, the vibration is generated. As for the relationship between the force F and the vibration displacement y of the in-tank structural member 3, as shown in FIGS. 4A and 4B, the phase of the vibration displacement y is delayed by 90 ° with respect to the exciting force F.

Next, the vibration displacement x of the liquid 12 in the L-shaped tube, which is generated by the vibration displacement of the in-tank structural member 3, is also generated by the above-described vibration system as shown in FIG.
The phase is further delayed by 90 ° with respect to the vibration displacement y of. At this time, the acting force F _c acts on the in-tank structural member 3 as a reaction of the inertial force F ₁ generated in the liquid 12 in the L-shaped tube. Here, F _I = M · [d (dx / dt) / (dt)] (2) F _c = −F _I (2) where M: L-shaped pipe Effective mass of the liquid 12 x = Vibration displacement of the liquid 12 in the L-shaped tube From the equation (2), F _c = −F _I = −M · [d (dx / dt) / (dt)] = Mω ² x (3) where ω = lateral tilt natural circular frequency of the in-tank structural member 3, that is, the acting force F _c and the liquid 1 in the communication pipe from the formula (3).
It can be seen that the vibration displacement x of No. 2 has the same phase (see (D) of the same figure).

To summarize the above, as shown in FIG. 4, the acting force F _c has a phase opposite to that of the exciting force F. That is, since the acting force F _C acts in the direction of canceling the exciting force F, the effective exciting force F + F _C on the tank structure is the exciting force indicated by the broken line as shown by the solid line in FIG. It can be made sufficiently smaller than F. Therefore, the vibration response of this tank structure can be made sufficiently smaller than that without the L-shaped tube.

The effect of the present invention is compared with the effect of the conventional tank structure as shown in FIG. That is, the broken line 13 in the same figure is a curve representing the vibration acceleration of the in-tank structural member 3 of the conventional non-countermeasure structure shown in FIG. 7, and the alternate long and short dash line 14 in FIG. In the case of the structure, the solid line 15 shows the case of the tank structure of the present invention shown in FIG. In the conventional structure shown in FIG. 7, in order to increase its natural frequency, a large number of anti-tilt elbow plates 6 are required, and the new natural frequency may resonate with another vibration force. The remaining. On the other hand, in the tank structure of the present invention, the vibration response can be suppressed as a whole, and there is no fear of a resonance phenomenon with another vibration force.

[0016]

As described above, the tank structure of the present invention is
By arranging the L-shaped pipe with the upper end closed, it is possible to suppress the vibration response of the structural material inside the tank. Therefore, the structural material inside the tank is simpler than the conventional structure and highly reliable. It is possible to prevent the occurrence of damage due to the resonance phenomenon.

In short, according to the first aspect of the present invention, there is provided a tank internal member extending on a horizontal vertical plane having an outer end welded over both members of the upper deck of a tanker for storing or carrying a liquid and the tank internal partition. A tank formed by a plurality of horizontal rectangular stiffeners having three sides extending in parallel along the above-mentioned three members welded to the inner partition wall of the tank, the inner structural material of the same tank and the inner end combing of the inner structural material of the tank. At
One end of a horizontal pipe part of approximately the same diameter extending in the front-rear direction is communicatively connected to the lower end of the vertical pipe part, which is fixed slightly below the left and right corners of the upper combing of the structural material in the tank, and the upper end is formed. Equipped with an L-shaped tube that is closed and opens at the lower end. When the tanker rocks, the L-shaped tube acts as a dynamic vibration absorber, without the need for an additional elbow plate. , Preventing the decrease of the natural circular frequency when wetted,
INDUSTRIAL APPLICABILITY The present invention is extremely useful industrially because it provides an economical tanker tank structure for reducing weight.

According to the invention of claim 2, in claim 1, from the closed upper end of the vertical tube portion of the L-shaped tube, the following formula (1)
Tanker tank structure characterized by having a small hole drilled at a position below the height H determined by (where ω ₀ = √ {[2G + K · (P ₀ + ρGD) ² / ρP ₀ H ] / (l _L + aL / A)} (1) where, a: cross-sectional area of the vertical pipe portion l _L : liquid level of the vertical pipe portion A: cross-sectional area of the horizontal pipe portion L: horizontal pipe Length of portion 8 D: Depth from liquid surface of liquid in tank to liquid surface of liquid 12 remaining in L-shaped pipe G: Gravity acceleration H: Depth from upper end of vertical pipe portion 7 to small hole 10 K: specific heat ratio of air P ₀ : atmospheric pressure ρ: density of liquid 12 ω ₀ : natural circular frequency of liquid column in L-shaped tube) The present invention is extremely useful industrially because it provides an economical tanker tank structure that reduces the weight by preventing the natural circular frequency from decreasing during liquid contact.

[Brief description of drawings]

FIG. 1 is a partial front view showing a tank structure according to an embodiment of the present invention.

FIG. 2 is a side view taken along the line II-II of FIG.

FIG. 3 is a side view showing the mechanical quantities of the L-shaped tube of FIG.

FIG. 4 is a diagram showing changes over time in mechanical quantities acting on each member of FIG. 1.

FIG. 5 is a diagram showing a relationship between a frequency and an acceleration of a structural member in a tank according to the present invention.

FIG. 6 is a cross-sectional view showing a tank of a conventional tanker.

7 is an enlarged view showing the structure of a connecting portion VII between the upper deck and the longitudinal bulkhead of FIG.

[Explanation of symbols]

1 Outer Plate (Upper Deck) 2 Tank Inner Partition 3 Tank Internal Material 4 Stiffener 5 Stiffener 6 Tilt-stop elbow 7 Vertical Pipe 8 Horizontal Pipe 9 Liquid 10 Small Hole 11 Enclosed Air (Air Chamber) 12 Liquid in L-shaped pipe 13 Vibration response curve of the structural material in the tank of the conventional structure of FIG. 14 14 Vibration response curve of the internal material of the conventional structure of FIG. 7 when an elbow plate is added 15 The structure of the present invention of FIG. Response curve of structural material in tank

Claims (2)

[Claims] 1. A tank internal member extending on a horizontal vertical plane having outer ends welded across both members of an upper deck of a tanker for storing or carrying a liquid and its internal partition wall, and parallel to the above three members. In the tank in which the three sides extending horizontally are formed by a plurality of horizontal rectangular stiffeners welded to the inner partition wall of the tank, the inner structural material of the same tank and the inner end combing of the inner material of the internal tank, One end of a horizontal pipe part of approximately the same diameter extending in the front-rear direction is communicatively connected to the lower end of the vertical pipe part that is fixed slightly below the left and right corners of the upper combing, and the upper end is closed and the lower end is open. A tanker tank structure, comprising an L-shaped pipe, wherein the L-shaped pipe acts as a dynamic vibration absorber when the tanker rocks. 2. The small hole according to claim 1, wherein the L-shaped pipe has a small hole formed at a position lower by a height H determined by the following formula (1) from the closed upper end of the vertical pipe portion. Tank structure of tanker (however, ω ₀ = √ {[2G + K · (P ₀ + ρGD) ² / ρP ₀ H] / (l _L + aL / A)} (1) where a: vertical pipe Cross-sectional area of section 7 _{L L} : Length of liquid column of vertical tube section A: Cross-sectional area of horizontal tube section 8 L: Length of horizontal tube section 8 D: From liquid surface of liquid in tank to L-shaped tube To the liquid surface of the liquid 12 remaining in the space G: Gravity acceleration H: Depth from the upper end of the vertical tube portion 7 to the small hole 10 K: Specific heat ratio of air P ₀ : Atmospheric pressure ρ: Density of liquid 12 ω ₀ : the natural circular frequency of the liquid column in the L-shaped tube).