JPH0516158Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an explosion structure for a tank that stores crude oil or other flammable liquid.

[Conventional technology]

A tank for storing flammable liquids such as crude oil and LPG is a cone-shaped or dome-shaped tank with a central part protruding upward from the upper end of a peripheral wall 1 installed on the ground, as shown in the schematic cross section in Figure 4. Roofing board 2 is put on,
It is configured to store flammable liquid O such as crude oil inside.

In tanks that store this type of flammable liquid, if the internal pressure suddenly increases due to the effects of radiant heat from a fire near the tank and the tank explodes, the flammable liquid inside will be destroyed. This will spill into nearby areas and burn, causing a major secondary disaster. Therefore, in the event of an explosion, a structure is required in which only the roof plate 2 is torn off and the explosion is released upwards.

On the other hand, strong wind currents flowing above the tank generate a large negative pressure on the upper surface of the tank roof plate 2, but the roof plate 2 has the necessary strength so that it will not be torn off by this negative pressure. installation is required.

Conventionally, as shown in the enlarged cross-section of FIG. The outer peripheral edge of the roof plate 2 is placed on the upper surface of the approximately central portion, and fillet welding 4 is performed in the space having a triangular cross section formed by the end surface of the outer peripheral edge and the upper surface of the flange portion 3a to create an airtight state. It is welded as much as possible. And this welded part 4
The leg length l is made smaller than the thickness of the roof plate 2, so that when the tank explodes, the welded part 4 will be the first to break and explode upward.

[Problem that the invention attempts to solve]

However, in the above conventional structure, fillet welding must be used to weld the roof plate 2 and the flange part 3a, so it is necessary to maintain reliable airtightness while providing conditions that can easily break in the event of an explosion. There is a problem in that it is extremely difficult to weld the leg length as small as possible so as to provide strength enough to withstand the negative pressure acting on the weld, and requires a highly skilled technique.

Particularly, the flange portion 3a is
However, with the conventional mounting structure using fillet welding, even if the leg length l can be welded as small as possible, the triangular space 4 will be broken as described above. Since the welding is performed to fill the inside of the part, it is inevitable that the cross-sectional area of the welded part 4 becomes large, and as shown in FIG. 3a is also pulled in the same direction and deflected inward of the tank together with the peripheral wall 1, and as a result, the angle θ between the flange 3a and the roof plate 2 gradually becomes smaller, and in order to break the welded portion 4, it is necessary to The welded portion 4 is dependent only on the tensile force, and the notch effect that tears the welded portion 4 does not occur, which has the disadvantage that it is difficult to break.

This invention was made with the aim of solving the problems of the prior art described above, and provides a tank explosion structure with a welded part structure that can reliably lead to rupture in the event of an explosion.

[Means for solving problems]

In order to solve the above-mentioned problems of the prior art, the present invention has a flange projecting outward in the horizontal direction from the upper end of the peripheral wall installed on the foundation, and a roof plate is attached to the tip of the flange. It is characterized in that the outer peripheral edges are overlapped and additional welding is performed over the entire circumference spanning the overlapping end surfaces of these flange portions and roof plates.

[Effect]

With the above structure, in the event that the pressure inside the tank rises abnormally and an explosion occurs, the upward bulging deformation of the roof plates will cause a radial tensile force to act on the roof plates, causing the flange to is pulled into the tank alarm, and the peripheral part of the roof plate is displaced in the upward direction, so the angle between the flange and the roof plate suddenly increases, and this causes a tearing force to act on the weld, causing it to break easily. The blast wave is emitted upward from this fractured part, preventing the entire tank from being destroyed.

〔Example〕

Embodiments of this invention will be described below with reference to FIGS. 1 to 3, with the same reference numerals assigned to the same members as those in FIG. 5.

FIG. 1 shows an enlarged cross-section of the joint between the peripheral wall 1 and the roof plate 2 of the tank according to this invention.

A vertical flange portion 3b of an angle member 3 is fixed to the upper end of the peripheral wall portion 1 by welding or the like, and a horizontal flange portion 3a of this angle member 3 is provided to protrude toward the outside of the tank.

The outer peripheral edge of the roof plate 2 is overlapped with the outer end of the flange portion 3a, and the flange portion 3a and the roof plate 2
The overlapped ends are welded around the entire circumference by excess welding 5 to be airtightly fixed. Therefore, the shape of this welded portion 5 is similar to the outer end surface 3 of the flange portion 3a, as shown in FIG.
d and the outer circumferential end surface 2a of the roof sheet 2, the cross-sectional area is only the portion where the excess is applied, and the angle θ between the flange portion 3a and the roof sheet 2 becomes large. When force is applied, it becomes a form that is easy to break due to the notch effect.

Therefore, if the pressure inside the tank increases abnormally and leads to an explosion, the pressure inside the tank causes the roof plate 2 to bulge upwards as shown by the chain line in Figure 4 because it has a mid-height shape. , the peripheral portion of the roof sheet 2 receives a large tensile force toward the center. This tensile force q is tanθ=
If it is 1/16, then 16P×D/4 (where P is the internal pressure,
D is the inner diameter of the peripheral wall 1), so it is 16 times the tensile force p = (PD/4) applied upward to the periphery of the roof board 2, and this force causes the peripheral part of the roof board 2 to be pulled toward the center. It will be done. Also, as a reaction force to the upward force p due to the tank internal pressure acting on the tip of the flange 3a, the peripheral wall 1
The maximum value of the moment due to the downward force acting on the weld acts on the excess weld. As a result, as shown in Fig. 3, the roof sheet 2 pulls the flange portion 3a into the tank (in the direction of arrow A) and bends it, while the peripheral portion of the roof sheet 2 deforms in the upward direction. However, as a result of this, the angle θ increases instantaneously, and combined with the notch effect due to the notch on the inside (tension side) of the extra weld 5, the breaking force of the weld 5 sharply decreases. That is, since the welded part 5 is thinner than the plate thickness 2 due to excess welding, as the angle θ increases, lacerations immediately occur at the joint corners of the outer end surfaces 3d and 2a of the flange part 3a and the roof sheet 2. Welding part 5 from this part
easily ruptures and explodes upward.

Therefore, the welded portion between the flange portion 3a and the roof plate 2 will break first, and the tank peripheral wall portion 1 will not be destroyed, and the blast wave will flow horizontally and cause damage to nearby structures. In particular, secondary disasters such as flammable liquid in the tank leaking out and causing a fire are prevented.

In addition, as shown in FIG. 7a, the flange portion 3a is formed facing outward, and the outer peripheral edge of the roof plate 2 is placed halfway in the width direction of the flange portion 3a, and the end surface 2a of the outer peripheral edge is formed. In the case where fillet welding 4 is performed in the space having a triangular cross-section formed by the top surface of the flange part 3a and the top surface of the flange part 3a, and in the case where the fillet welding 4 is performed in the space formed by the top surface of the flange part 3a and the outer periphery of the roof plate 2, as shown in FIG. The relationship between the rupture performance at the time of an explosion and the airtight performance in the case where the overlapping end faces 3a and 2a are overlapped and the extra welding 5 is performed across these overlapping end faces 3a and 2a will be explained.

In order for the weld to break easily in the event of an explosion, the thickness l of the weld is required to be small, and in order to maintain airtightness, the length l ₁ of the weld is required to be long. Since the welding structure shown in Fig. 7a is a fillet weld, when the thickness l of the welded part 4 is reduced, the length l ₁ of the penetration part also becomes smaller, and the length l ₁ of the penetration part becomes smaller.
As the thickness 1 increases, the thickness 1 also increases, making it difficult to achieve both easy breakability and airtightness in the event of an explosion. On the other hand, in the welding structure shown in Fig. 7b, since the weld is an excess weld, it is possible to increase the length l ₁ of the penetration part while keeping the thickness l of the welded part thin, which reduces the ease of rupture in the event of an explosion. It is possible to easily achieve both airtightness.

[Effect of idea]

As explained above, this invention has a flange projecting outwardly from the upper end of the peripheral wall,
The outer edge of the roof plate is overlapped with the tip of this flange, and the overlapping edge of the flange and roof plate is welded all around, so the pressure inside the tank will not rise abnormally. Even if an explosion occurs,
When the roof plate bulges upward, the tensile force toward the center causes the flange to tilt inward into the tank, and at the same time, the internal pressure causes the roof plate to deform in an upward direction, causing the flange and roof plate to form As the angle θ increases, a notch effect acts on the weld,
In addition, this welded part is an overfill weld that spans the outer end surfaces of the flange part and the roof plate, so it is easy to cause lacerations. The explosion can be emitted upward from the fractured part of the weld, making it possible to reliably prevent damage from the blast as well as secondary disasters such as fires caused by the leakage of flammable liquid inside the tank.
Furthermore, unlike conventional fillet welding, welding can be performed without the need for highly skilled techniques, making it easier to construct the tank.

In addition, since this invention uses excess welding, the length of the penetration part can be increased while keeping the thickness of the welded part thin, making it easy to achieve both easy breakability and airtightness in the event of an explosion. be able to.

[Brief explanation of the drawing]

Fig. 1 is a vertical sectional view of the main part showing one embodiment of this invention, Fig. 2 is an enlarged sectional view of the welded part in Fig. 1, Fig. 3 is an explanatory diagram showing the state of deformation at the time of explosion, and Fig. 4 The figure is a schematic vertical cross-sectional view showing an example of a ground-mounted tank to which this invention is applied, Figure 5 is a vertical cross-sectional view showing a conventional roof plate mounting structure, and Figure 6 is a schematic longitudinal cross-sectional view showing an example of a ground-mounted tank to which this invention is applied. The explanatory diagram shown in FIG. 7 is a diagram illustrating the relationship between the rupture performance at the time of explosion and the airtightness performance. 1... Peripheral wall part, 2... Roof plate, 3a... Flange part, 5... Extra welding part.

Claims (1)

[Scope of utility model registration request] A flange portion is provided horizontally protruding outward from the upper end of the peripheral wall installed on the foundation, and the outer peripheral edge of the roof plate is overlapped with the tip of this flange portion, and these flange portions and the roof plate are overlapped. A tank explosion structure characterized by excess welding over the entire circumference spanning the mating end faces.