JP3354748B2 - Tanker tank structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, in a tanker tank structure, FIG.
(A) A single hull as shown in the cross section and a double hull as shown in FIG. All tank structures are designed in consideration of the liquid pressure of the liquid loaded in the tank, and the dimensions of the outer plate, the tank inner partition, the tank internal material, and the stiffener are smaller than those of the tank lower part. 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 joint VI between the outer plate (upper deck) and the tank inner wall VI
The part I is composed of an upper deck 1, a tank inner partition 2 and a tank internal material 3, as shown in the enlarged view of FIG. A stiffener 4 is disposed on the upper deck 1 and the partition wall 2 in the tank, and a stiffener 5 and a fall-preventing elbow plate 6 are also disposed on the structural member 3 in the tank.
In this type of tanker, the natural frequency of the lateral falling of the tank member 3 is generally sufficiently high when the liquid is empty, and there is no problem. In some cases, the tank 3 may be in the vibration frequency range of the propulsion device, and the tank structure 3 may be resonated by the sideways vibration to damage the tank structure. To prevent such damage to the tank structure,
It is necessary to devise a method of separating the natural frequency of the horizontal falling of the tank member 3 from the vibration frequency range of the propulsion device of the ship. Conventionally, as shown in FIG. By increasing the rigidity by adding the elbow plate 6, the natural circular frequency is increased.

[0003]

However, in such a conventional tank structure, a much larger number of fall-preventing elbow plates 6 are required in comparison with the fall-preventing elbow plates 6 which are originally required from the viewpoint of prevention of lateral fall. Therefore, the weight of the tank structure is increased and workability is reduced.

[0004] The present invention has been proposed in view of such circumstances, without the need to add an additional fall-prevention elbow plate,
It is an object of the present invention to provide an economical tanker tank structure in which a reduction in the natural circular frequency at the time of liquid contact is prevented and weight is reduced.

[0005]

In order to achieve the above object, the invention according to claim 1 is characterized in that an outer end is welded over both members of an upper deck of a tanker for storing or transporting a liquid and a partition inside the tank. And the three sides extending in parallel along the three members were welded to the tank inner partition, the tank inner material, and the tank inner material inner end combing, respectively. In a tank formed of a plurality of levels of horizontal rectangular stiffeners, the tanks having substantially the same diameter are respectively fixed slightly below the left and right corners of the upper combing of the internal components of the tank and extend in the front-rear direction at the lower end of the vertical pipe portion. One end of the horizontal pipe portion is connected in communication, the upper end is closed, and the lower end is opened, and the L-shaped tube is provided , and the L-shaped tube acts as a dynamic vibration absorber.

According to a second aspect of the present invention, in the first aspect, the following equation (1) is obtained from the closed upper end of the vertical pipe portion of the L-shaped pipe.
(Where ω ₀ = √ ｛[2G + K · (P ₀ + ρGD) ² / ρP ₀ H] / (l _L + aL / A) ) （(1) where, a: cross-sectional area of vertical pipe section 1 _L : length of liquid column of vertical pipe section 7 A: cross-sectional area of horizontal pipe section 8 L: length of horizontal pipe section 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 section 7 to the small hole 10 K: Air Specific heat ratio P ₀ : atmospheric pressure ρ: density of liquid 12 ω ₀ : natural circular frequency of the liquid column in the L-shaped tube).

[0007]

According to this structure, when the liquid is stored in the tank by arranging the L-shaped pipe, the liquid flows into the L-shaped pipe from the lower end opening, and each of the vertical pipe portions is formed. Since air is sealed in the upper end of the L-shaped tube ,
The effect as a dynamic vibration absorber occurs. Therefore, this L
Due to the reaction force of the force acting on the U-shaped pipe, it is possible to suppress the vibration of the tank internal material in the sideways direction.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, an embodiment of the present invention will be described. FIG. 1 is a front view showing an upper end corner portion of a tank internal material, FIG. 2 is a side view taken along the line II-II of FIG. FIG. 4 is an explanatory view showing the action of the L-shaped tube as a dynamic vibration absorber, FIG. 4 is a diagram showing the time-dependent changes in various mechanical quantities acting on each member in FIG. 1, and FIG. 5 is the L in FIG. It is a diagram showing the relationship between the vibration frequency of the U-shaped pipe and the vibration acceleration of the components inside the tank.

In the above figure, the same reference numerals as those in FIG. 7 denote the same members as those in the figure. First, in FIGS. 1 and 2, each of the L-shaped pipes on the port side and the starboard side has the same length. The vertical pipe portion 7 is composed of a horizontal pipe portion 8 having substantially the same diameter as the vertical pipe portion 7, and one end opening is fixedly connected to each lower end opening and the other end is opened. 3 is fixed on the vertical surface of the tank internal member 3 near the top of the tank 3.

Here, the upper ends of the vertical pipe portions 7 are closed. Further, small holes 10 are provided in the vertical pipe section 7 and the horizontal pipe section 8 as shown in FIG. The small hole is basically provided at an outer communication part between the vertical pipe part 7 and the horizontal pipe part 8 or at an intermediate position of the vertical pipe part 7 as shown in FIG. 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 section 8. However, since the upper end of the vertical pipe is closed, air remains inside the upper end of the vertical pipe 7 and is compressed by the liquid pressure of the liquid 9 and sealed in the upper end of the vertical pipe 7.

As shown in FIG. 3, a single-degree-of-freedom vibration system is formed in such an L-shaped tube using the remaining sealed air 11 as a spring element and the liquid 12 in the L-shaped tube as a mass element. You. The natural circular frequency ω ₀ of this vibration system is given by Expression (1) assuming a symmetric 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 part l _L : vertical Length of liquid column of pipe 7 A: Cross-sectional area of horizontal pipe 8 L: Length of horizontal pipe 8 D: From liquid level of liquid in tank to liquid level of liquid 12 remaining in L-shaped pipe G: gravity acceleration H: depth from the upper end of the vertical pipe section 7 to the small hole 10 K: specific heat ratio of air P ₀ : atmospheric pressure ρ: density of the liquid 12 ω ₀ : liquid column in the L-shaped pipe 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 size of the small hole 10 are set so that the natural frequency of the L-shaped pipe matches the natural frequency of the sideways vibration of the tank internal member 3. The position and tank level have been determined. H can be obtained by back calculation if the set natural frequency ω ₀ is determined in equation (1). Here, the position H of the small hole 10 is 0 <H <Hmax.
(FIG. 3). However, the position of the small hole determines the initial volume of the sealed air, and thus has an important effect that the resonance frequency of the liquid column of the L-shaped tube can be determined.

Now, during the operation of the tanker , the tank interior material 3
Considering the case where the natural frequency of side-to-side resonance resonates, assuming that the vibrating force in this case is F, the relationship between the vibrating force F and the vibration displacement y of the in-tank material 3 is as shown in FIGS. As shown in B), the phase of the vibration displacement y is delayed by 90 ° with respect to the excitation force F.

Next, the vibration displacement x of the liquid 12 in the L-shaped pipe caused by the vibration displacement of the tank internal material 3 is also determined by the above-described vibration system, as shown in FIG.
The phase is further delayed by 90 ° with respect to the vibration displacement y. At this time acting force F _c is applied to the tank Uchigamae material 3 as a reaction of the inertia force F ₁ generated in the liquid 12 of the L-shaped tube. Here, F _I = M · [d (dx / dt) / (dt)] (2) F _c = −F _I (2) where M: L-shaped pipe X = vibration displacement of liquid 12 in L-shaped tube From equation (2), F _c = −F _I = −M · [d (dx / dt) / (dt)] = Mω ² x · ... (3) where, omega = falling down laterally natural circular frequency of the tank Uchigamae material 3, that is in phase with the vibration displacement x of the acting force F _c and the communicating pipe liquid 12 from the equation (3) (D in the same figure)
reference).

In summary, as shown in FIG. 4, the acting force F _c has the opposite phase to the vibrating force F. That is, since the acting force F _C acts in a direction to cancel the vibratory force F, the effective excitation force F + F _C to the tank structure, as shown in solid line in FIG. (E), vibratory force indicated by a broken line It can be made sufficiently smaller than F. Therefore, the vibration response of the present tank structure can be made sufficiently small as compared with the case where there is no L-shaped pipe.

FIG. 5 shows a comparison between the effect of the present invention and the effect of the conventional tank structure. That is, the broken line 13 in the figure is a curve representing the vibration acceleration of the tank material 3 of the conventional unmeasured structure shown in FIG. 7, and the dashed line 14 is the conventional measure in which the fall-preventing elbow plate 6 is added in the figure. In the case of the structure, the solid line 15 indicates the case of the tank structure of the present invention shown in FIG. 1, respectively. In the conventional structure shown in FIG. 7, a large number of fall-preventing elbow plates 6 are required to increase the natural frequency, 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 whose upper end is closed, the vibration response of the tank interior material can be suppressed, so that the tank interior material is simpler and more reliable than the conventional structure. The occurrence of damage due to the resonance phenomenon can be prevented.

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 outer ends welded to both members of an upper deck of a tanker for storing or transporting liquid and an inner partition of the tank. A tank formed by a plurality of levels of horizontal rectangular stiffeners welded to the inner wall of the tank, the inner material of the tank, and the inner end combing of the inner material of the tank, the three sides extending in parallel along the three members. At
One end of a horizontal pipe part of approximately the same diameter, which is fixed slightly below the left and right corners of the upper combing of the tank internal material and extends in the front-rear direction to the lower end of the vertical pipe part, is connected in communicative fashion and the upper end is lower the obstruction comprises a L-shaped tube which is open, the L
By letting the T-shaped tube act as a dynamic vibration absorber,
The present invention is extremely industrially applicable because an economical tanker tank structure that reduces the natural frequency at the time of liquid contact and prevents weight is obtained without the need for an additional fall-preventing arm plate. It is useful.

According to the second aspect of the present invention, in the first aspect, the following formula (1) is obtained from the closed upper end of the vertical pipe portion of the L-shaped pipe.
The tank structure of the tanker is characterized by having a small hole drilled at a position below the height H determined by the formula (where ω ₀ = √ ｛[2G + K · (P ₀ + ρGD) ² / ρP ₀ H) ] / (l _L + aL / A) ａ (1) where, a: cross-sectional area of vertical pipe 7 l _L : liquid level of vertical pipe 7 A: cross-sectional area of horizontal pipe 8 L: horizontal pipe Length of part 8 D: Depth from liquid level of liquid in tank to liquid level of liquid 12 remaining in L-shaped pipe G: Gravity acceleration H: Depth from upper end of vertical pipe part 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 the liquid column in the L-shaped pipe) The present invention is extremely useful in industry since an economical tanker tank structure for preventing the lowering of the natural circular frequency at the time of liquid contact and reducing the weight is obtained.

[Brief description of the 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.

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

FIG. 4 is a diagram showing changes with time of various mechanical quantities acting on each member of FIG. 1;

FIG. 5 is a diagram showing the relationship between the frequency and the acceleration of the tank internal material according to the present invention.

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

7 is an enlarged view showing the structure of a joint VII between the upper deck and the longitudinal partition wall in FIG. 6;

[Explanation of symbols]

REFERENCE SIGNS LIST 1 outer plate (upper deck) 2 tank inner partition wall 3 tank inner member 4 stiffener 5 stiffener 6 fall-preventing elbow plate 7 vertical pipe 8 horizontal pipe 9 liquid 10 small hole 11 sealed air (air chamber) 12 L-shaped in-pipe liquid 13 Vibration response curve of tank material of conventional structure in FIG. 7 14 Vibration response curve of internal material when elbow plate is added to tank of conventional structure in FIG. 15 15 Structure of the present invention in FIG. Response curve of the tank internal material

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B63B 3/56 B63B 25/08

Claims (2)

(57) [Claims] 1. A tank internal member extending on a horizontal vertical plane having an outer end welded to both members of an upper deck of a tanker for storing or transporting liquid and an inner partition wall of the tank, and parallel to the three members. In a tank, three sides of which are formed by a plurality of horizontal rectangular stiffeners welded to the inner wall of the tank, the inner material of the tank, and the inner end combing of the inner material of the tank, respectively, One end of a horizontal pipe part of approximately the same diameter, which is fixed slightly below the left and right corners of the upper combing and extends in the front-rear direction and is connected to the lower end of the vertical pipe part, is closed at the upper end and opened at the lower end A tank structure for a tanker, comprising an L-shaped tube , wherein the L-shaped tube acts as a dynamic vibration absorber. 2. The method according to claim 1, further comprising a small hole formed at a position below a closed upper end of the vertical pipe portion of the L-shaped pipe by a height H determined by the following equation (1). Tank structure (however, ω ₀ = √ ｛[2G + K · (P ₀ + ρGD) ² / ρP ₀ H] / (l _L + aL / A)｝ (1) where a: vertical pipe 1 _L : Length of liquid column of vertical pipe 7 A: Cross-sectional area of horizontal pipe 8 L: Length of horizontal pipe 8 D: L-shaped pipe from liquid level of liquid in tank 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 the liquid 12 ₀ : the natural circular frequency of the liquid column in the L-shaped tube).