JPH08324687A - Explosive structure of tank - Google Patents

Abstract

PURPOSE: To provide an explosive structure of hazardous goods tank which can be securely exploded regardless of conditions of the roof strength or the like. CONSTITUTION: This tank is provided with a tank body cylindrically formed with side plates 3 erected on a foundation, an external roof plate 5a covering a specified scope from the upper end of the tank body to the center of tank, a cylindrical member 8 erected on the whole periphery of the external roof plate 5a at the end of the tank center side of the external roof plate 5a, and an internal roof plate 5b connected to the upper end of the cylindrical member 8 to cover the opening of the tank body. When the inner pressure of the tank body exceeds a specified value, the connected part of the cylindrical member 8 and the internal roof plate 5b is broken by explosion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an explosive structure for a tank for storing liquid dangerous substances.

[0002]

2. Description of the Related Art In a fixed roof type storage tank for storing dangerous substances such as oil, when the pressure in the tank rises abnormally due to the explosion of dangerous substances, the gas or vapor inside is discharged to the upper part. It is required that the structure be able to. Such a structure is generally called an explosive structure. FIG. 5 is an explanatory view showing the structure of a fixed roof tank of a general detonation structure,
FIG. 6 is an enlarged view of part A in FIG. As shown in FIGS. 5 and 6, the fixed roof tank has a bottom plate 2 on the tank foundation 1.
Is installed, the side plate 3 is erected on the outer peripheral portion of the bottom plate 2, and a dome-shaped roof plate 5 is attached via a top angle 4 attached to the upper end of the side plate 3. A storage liquid 6 such as oil is stored inside the tank.

In FIG. 6, a hatched portion (side plate portion W
c, the portion of the roof plate portion Wh) is a portion (hereinafter referred to as "top ring") that strongly resists the radiation, and the roof plate 5 and the top angle are caused by the buckling of the top ring. The welded part with No. 4 breaks and the detonation occurs.

FIG. 7 is an explanatory view for explaining the mechanism of detonation of a general fixed roof tank constructed as described above, and FIG. 8 is an enlarged view of portion B in FIG. Next, the mechanism of detonation will be described based on FIGS. 7 and 8. In the space above the stored liquid 6 inside the fixed roof tank as described above, a mixed gas of vaporized storage liquid 6 and vapor and air is always present. Therefore, if the mixed gas is ignited for some reason, the gas 7 due to the explosion increases the pressure inside the fixed roof tank, and the pressure causes the fixed roof tank to expand as shown by the broken line in FIG. 7. Therefore, the top angle 4 is deformed by being pulled inward (direction in which the diameter is reduced) by the roof plate 5 '. For this reason,
The top ring buckles and the roof plate 5
That is, the welded part between the top angle 4 and the top angle 4 is broken, and detonation occurs. The state of this detonation is shown in FIG. in this way,
If the pressure inside the tank can be released to the upper part, the fire can be stopped only inside the tank, and it is also possible to minimize the burning of other tanks.

By the way, in order for the top ring to buckle, it is necessary that the cross-sectional area of the top ring is smaller than a certain value, and when such a condition is satisfied, the internal pressure of the fixed roof tank is increased. Then, the deformation is increased, and the top ring buckles and breaks, resulting in detonation. On the other hand, when the effective area of the top ring is larger than the predetermined value, the deformation of the top ring is small, buckling failure does not occur, and the explosion does not occur. In this case, the lower end of the tank side plate 3 is lifted as shown by the broken line in FIG. 10 due to the abrupt increase in tank internal pressure, and the joint between the side plate 3 and the bottom plate 2 becomes
Will emerge from. At this time, the portion of the bottom plate 2 close to the side plate 3 loses the supporting force of the foundation 1 and receives an excessive load, so that it is deformed and cut, and the stored liquid 6 flows out of the tank into the oil levee as shown in FIG. Becomes In this situation, if there are other tanks in the dike,
The tank will be involved in the fire and the damage to the fire will be increased.

[0006]

By the way, there is also a type of fixed roof tank in which a predetermined pressure is applied to the inside of the tank in order to reduce evaporation of the stored liquid. The roof of this type of tank is required by design to have a relatively large roof slope corresponding to the internal pressure. In this case, the roof bone that supports the load of the roof plate,
In many cases, a truss roof structure (roof slope 1/6 to 1/5) or a spherical roof structure (roof curvature tank diameter 0.8 to 1.2 times) is used. At this time, the cross section of the top ring needs to have a large top angle cross-sectional area that constitutes the top ring in order to support the loads such as the roof weight and snow load and to support those loads at the upper part of the side plate. In such a case,
Even if the pressure rises due to an explosion in the tank, there are many cases where the top ring has a large cross-sectional area and is difficult to deform (explosive). In other words, the cross-sectional area of the top ring is determined not only based on the construction of the detonation structure, but also by taking into consideration the roof weight and other loads, so the cross-sectional area of the top ring is detonated. The tank is inevitably larger than the cross-sectional area of the structure, which means that the tank will not necessarily have an explosive structure (the joint between the side plate and the bottom plate can be lifted) will be designed.

Therefore, in the case of newly installing a tank in which the cross-sectional area of such a top ring must be large,
It is necessary to install anchor bolts on the bottom of the tank to prevent the bottom plate from rising when an internal explosion occurs. However, in order to install the anchor bolts, it is necessary to install a heavy concrete ring just below the side plate to support the anchor bolts. Becomes higher. However, it is very uneconomical to raise the basic cost as a countermeasure for the explosion of a tank fire that is unlikely to occur while the tank is in use. Also, since the concept of the detonating mechanism has not been established in the past, there are many cases where tanks that do not have a detonating structure are constructed without the equipment such as anchor bolts because of the large cross-sectional area of the top ring. In the event of a flammable explosion, there is concern about the spread of fire damage.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a detonation structure of a tank which can surely detonate regardless of conditions such as roof strength.

[0009]

A tank detonation structure according to the present invention comprises a tank body formed by side plates erected on a foundation and a predetermined range extending from the upper end of the tank body toward the center of the tank. An outer roof plate to cover, a cylindrical member that is provided upright over the entire circumference of the outer roof plate at an end of the outer roof plate on the center side of the tank, and is joined to an upper end of the cylindrical member, An inner roof plate covering the opening of the tank main body is provided, and when the internal pressure of the tank main body exceeds a predetermined value due to an explosion or the like, the joint between the tubular member and the inner roof plate is broken. It was designed to detonate.

Further, a flange is provided on the upper end of the tubular member.

[0011]

In the tank detonation structure configured as described above, if the internal pressure of the tank rises due to an explosion or the like,
A tensile force is generated as a film force on the inner roof plate. The tensile force causes the tubular member to receive a compressive force in the circumferential direction, and when the compressive force exceeds a predetermined value, the tubular member buckles. As a result, a fracture occurs at the joint between the inner roof plate and the tubular member, resulting in detonation.

By providing the flange portion on the upper end of the tubular member, the tubular member and the inner roof plate can be easily joined.

[0013]

1 is a sectional view of an embodiment of the present invention, FIG. 2 is a plan view of the same embodiment of the present invention, and FIG. 3 is a C of FIG.
FIG. 12 is an enlarged view of a part, and the same parts as those of FIGS. In the figure, 5a is an outer roof plate that covers a predetermined range from the upper end of the side plate 3 toward the center of the tank (a range with a distance L from the joint with the top angle toward the center of the tank), and 8 is an outer roof plate 5a. It is a tubular member installed over the entire circumference of the end portion on the center side of the tank, and is composed of a tubular portion 8a and an outward flange 8b provided on the upper end portion of the tubular portion 8a. The height of the tubular portion 8a is set to be much lower than the diameter of the tubular member 8 as shown in the figure. 5b is an inner roof plate whose outer peripheral end is joined to the outward flange 8b to cover the tank opening.

The structure of the tubular member 8 supports only the roof plate, and it is not necessary to support the roof frame as in the conventional example, and it can be determined by considering only the radiation. it can. Therefore, in the case of a structure which is hard to be detonated like the spherical roof structure mentioned in the conventional example, it is possible to surely detonate by reducing the cross-sectional area of the tubular member 8. Further, the tensile force generated on the roof plate due to the increase in the tank internal pressure can be calculated by a normal design calculation, and the buckling strength of the tubular member 8 can also be designed based on the tensile force of the roof plate 5, so that the design can be performed. Very easy.

FIG. 4 is an explanatory view for explaining the mechanism of detonation of this embodiment. Hereinafter, the mechanism of detonation of this embodiment will be described with reference to FIG. When an explosion occurs inside the tank and the internal pressure of the tank rises, a tensile force T that is a film force (a force that does not have directionality and goes in all plane directions) is generated on the roof plate 5. At this time, the tubular member 8 receives an upward tensile force T from the inner roof plate 5b over the entire circumference thereof. The tensile force T causes the cylindrical member 8 to be subjected to a circumferential compressive force. Then, when this compressive force exceeds a predetermined value,
The tubular member 8 buckles, the joint portion with the inner roof plate 5b is broken, and the explosion occurs. At this time, the top ring including the top angle 4 does not buckle because it has a large cross-sectional area.

According to this embodiment, with a simple structure,
A reliable explosion structure can be realized. Therefore, according to the structure shown in the present embodiment, not only when newly constructing a tank, but also for an existing tank that does not have an explosive structure, the explosive structure can be made by a simple modification work. Can increase the safety of. This will also increase the safety of petrochemical plants installed throughout the country,
It is a very important economic effect.

In the above embodiment, the tubular member 8 is installed at a position L from the outer peripheral edge of the outer roof plate toward the center of the tank. Should be set a little larger for the convenience of construction, while the value of L should be as small as possible for the efficiency of detonation. Therefore, it is preferable to set the value of L to the most appropriate value in consideration of construction convenience and efficiency of detonation.

[0018]

As described in detail above, in the present invention, the outer roof plate and the inner roof plate are joined together through the tubular member,
Since detonation is made to occur at this joint, even in the case of a roof that is unlikely to have an explosive structure such as a spherical roof structure, the detonation structure can be reliably achieved. Further, in the strength design of the tubular member, it is possible to focus only on the buckling strength due to the increase in the tank internal pressure, which facilitates the design.

Further, since the explosion proof structure is obtained only by installing the tubular member on the roof plate, it is not necessary to install the anchor bolts on the tank foundation, and the tank can be constructed on the usual inexpensive foundation. It is possible and economical.

Further, since the flange portion is provided on the upper end portion of the tubular member, the inner roof plate and the tubular member can be easily joined, and the workability is improved.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a plan view of one embodiment of the present invention.

FIG. 3 is an enlarged view of a C portion of FIG.

FIG. 4 is an explanatory diagram for explaining the mechanism of detonation according to the present embodiment.

FIG. 5 is an explanatory view showing a structure of a fixed roof tank having a general detonation structure.

6 is an enlarged view of part A in FIG.

FIG. 7 is an explanatory diagram for explaining a conventional mechanism for detonating a fixed roof tank.

FIG. 8 is an enlarged view of part B in FIG. 7.

FIG. 9 is an explanatory diagram for explaining an explosive state of a conventional general fixed roof tank.

FIG. 10 is an explanatory diagram showing a state in which the tank internal pressure has risen in a conventional general fixed roof tank.

FIG. 11 is an explanatory view showing a lower fractured state in a conventional general fixed roof tank.

[Explanation of symbols]

 1 foundation 2 bottom plate 3 side plate 4 top angle 5 roof plate 5a outer roof plate 5b inner roof plate 6 stored liquid 8 tubular member 8a tubular portion 8b outward flange

Claims (2)

[Claims] 1. A tank main body formed by side plates erected on a foundation, an outer roof plate covering a predetermined range from the upper end of the tank main body toward the tank center, and a tank center side end of the outer roof plate. A tubular member that is provided upright over the entire circumference of the outer roof plate, and an inner roof plate that is joined to the upper end of the tubular member and covers the opening of the tank body, An explosive structure for a tank, characterized in that when the internal pressure of the tank body exceeds a predetermined value, the joint between the tubular member and the inner roof plate is broken and detonates. 2. The explosive structure for a tank according to claim 1, wherein a flange portion is provided on an upper end portion of the tubular member.