JPH0610519B2 - Triple shell liquid storage tank - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a triple shell storage tank for storing a low temperature liquefied gas such as LNG or LPG.

<Prior Art> As a liquid storage tank of this type, a double shell storage tank C made up of a steel inner tank A and an outer tank B as shown in FIG. 2 is generally used.

This double-shell storage tank C has a structure in which a heat insulating material D is interposed between the inner and outer tanks A and B, and a liquid barrier E is built around the liquid storage tank C so as to cope with liquid leakage.

<Problems to be Solved by the Present Invention> The conventional liquid storage tank has the following problems.

(B) Since the liquid storage tank is made of steel, there is a high risk that cracks will occur due to concentration of temperature stress in the welded portion.

(B) Since ordinary steel is used for the outer tub B which is the outer cover, the strength against outer flying objects is insufficient.

(C) Since the heat resistance is insufficient, problems remain in terms of safety against external fires and keeping the stored liquid at a constant temperature.

(D) The liquid barrier E is provided, but when the outer tank B is covered and the liquid leaks, the gas diffuses over a wide range.

(E) Since expensive steel material excellent in low temperature brittleness is used, the construction cost becomes high.

(F) In addition, as a storage tank with a three-tank structure, the actual construction of Sho 51-988
The tank of Japanese Patent No. 13 is known.

This tank has a structure in which tanks having different diameters are concentrically arranged, the inside is divided into three chambers, and liquid is dispersed and stored in each tank.

However, in this type of storage tank, there is a risk of liquid leakage if the outer tank is damaged, and it is necessary to install a separate dike.

(G) Further, it is disclosed in Japanese Utility Model Laid-Open No. 59-22399 that the body of the storage tank is made of concrete.

In this storage tank, the lower part of the inner tank and the lower part of the outer tank are placed on the bottom plate to share the bottom plate, and a liquid barrier with a bottom plate is arranged outside the outer tank.

Therefore, in this type of storage tank, if the outer and bottom slabs of the bottom plate of the liquid barrier are damaged due to uneven settlement, there is a risk of liquid leaking from the inner tank.

(H) In addition, an inner tank in which the bottom plate, side wall, and ceiling are integrally formed,
A double-shell liquid storage tank in which a bottom plate, a side wall, and a ceiling of an inner tank are surrounded by an outer tank and made of concrete is disclosed in JP-A-60-88.
It is disclosed in Japanese Patent Publication No. 297.

Since the outer tank also functions as the outer tank, this liquid tank is a double-shell type so far from the viewpoint of preventing liquid leakage and gas diffusion when the inner tank is damaged, and safety against external flying damage. It is highly evaluated as compared to the liquid storage tank.

On the other hand, in view of the geographical conditions that earthquakes frequently occur and the large size of the storage tanks due to the plan to increase the amount of stockpiling, a storage tank with extremely high qualitative safety is desired under all circumstances. ing.

<Object of the present invention> The present invention has been made in view of the above points, and the object of the present invention is to reliably prevent liquid leakage and to safely store low-temperature liquefied gas under all circumstances. , To provide a triple shell reservoir.

<Structure of the Present Invention> An embodiment of the present invention will be described below with reference to the drawings.

<1> Overall Structure of Liquid Storage Tank FIG. 1 shows a triple-shell liquid storage tank.

This liquid storage tank has a triple-shell structure composed of three independent completely sealed shells, and is composed of an inner tank 1, an intermediate tank 2 and an outer tank 3 from the inner side.

Each of the tanks 1, 2, and 3 is made of RC concrete or PC concrete having excellent strength.

<B> Inner Tank The inner tank 1 is a liquid storage tank having excellent air-tightness and liquid-tightness.

A skin plate 11 may be provided on the outer periphery of the inner tank 1 as needed.

This inner tank 1 is placed on the floor slab 21 of the intermediate tank 2 via the bearing tank 4 so as to follow the contraction deformation of the liquid storage tank at the time of cooldown, and is placed on the intermediate tank 2 via the movement preventing ring 12. Fix it.

An annular space is secured between the side walls of the tanks 1 and 2.

The concrete skeleton bears the stress generated due to the temperature decrease in the inner tank 1, and the skin plate 11 has airtightness and liquidtightness.
Will be borne by.

Therefore, the skin plate 11 is not required to have high strength,
Inexpensive materials can be used.

<C> Intermediate Tank The intermediate tank 2 is a high-dac type liquid-proof basin, and is placed on the floor 31 of the outer container 3 through the bearing layer 5 that follows shrinkage deformation during cooldown of the liquid storage tank. , Is fixed to the outer container 3 via the movement preventing ring 22.

Further, an airtight / liquid-tight roof plate 23 is provided on the upper part of the annular space defined by the side wall of the intermediate tank 2 and the side wall of the inner tank 1 having a height sufficient to prevent liquid leakage, and the intermediate tank 2 is sealed. Secure the sex.

When the intermediate tank 2 is stored in the outer tank 3, the cold insulating material 6 is interposed between the floor slab, the side wall and the roof of both tanks 2 and 3.

As the cold insulating material 6, for example, polyurethane foam or polystyrene foam can be used.

<D> Outer tank The outer tank 3 is a completely sealed shell for the purpose of the foundation and outer cover of the entire liquid storage tank.

The outer tank 3 has significantly improved fire resistance and strength against external flying objects, as compared with the conventional steel jacket.

A heater 33 is installed in the floor slab 31 to prevent the ground from freezing.

A skin plate 32 may be provided on the inner circumference of the outer tub 3.

<Operation><A> Airtightness and liquid-tightness Even if the inner tank 1 is cracked and the liquid leaks, the intermediate tank 2 can maintain the airtightness and liquid-tightness.

Even in the worst case where the intermediate tank 2 is damaged, the outer tank 3 functions as a secondary liquid preventive solution and the leakage of the liquid can be reliably prevented.

In particular, concrete is known to have increased strength in a cryogenic state, so that the airtightness and liquidtightness of the liquid storage tank are improved.

Further, since the annular space formed between the side walls of the inner tank 2 and the intermediate tank 3 is sealed, the amount of dangerous boil-off gas generated when the stored liquid leaks can be suppressed to a very small amount.

<B> Durability Since the outer tank 3 is made of concrete, it has superior fire resistance and toughness against flying objects compared to steel.

<C> Heat retention The inner tank 1 and the intermediate layer 2 have an external heat insulation structure due to the interposition of the heat insulating material 6.

Therefore, the temperature is constantly maintained close to the liquid temperature, and excessive temperature stress is prevented from being generated in the member.

<Effects of the Present Invention> Since the present invention is as described above, the following effects can be obtained.

(B) By having the two tanks, the intermediate tank and the outer tank, also have the function of the liquid-proof basin, good air-tightness and liquid-tightness can be secured, and the safety against leakage can be significantly improved.

(B) Since the outer cover is made of high-strength concrete, it has excellent durability and does not require maintenance such as painting as compared with the conventional steel outer cover.

(C) Effective use of the land can be achieved by eliminating the need for liquid barriers around the liquid storage tank.

(D) By forming the liquid storage layer formed of RC concrete or PC concrete having excellent strength into a triple structure,
Performance against external force and heat retention are significantly improved.

(E) Even if uneven settlement occurs on the ground that supports the storage tank, RC
Each tank made of concrete or PC concrete is not easily damaged.

If the bottom plate of the outer tank is damaged due to uneven settlement, the bottom plate of the intermediate tank can replace the bottom plate of the outer tank to protect the inner tank, and both bottom plates of the outer tank and the intermediate tank are damaged. Even in this case, since the inner tank itself has a bottom plate, there is no fear of liquid leakage.

Also, even if the bottom plate of the opposite inner tank is damaged, the bottom plate of the intermediate tank will function instead, and if the bottom plate of the intermediate tank is also damaged, the outer tank will function as a liquid proof.

As described above, according to the present invention, not only the side wall but also the bottom slab is tripled, so that the low temperature liquefied gas can be stored extremely safely in all situations.

[Brief description of drawings]

 1 is a sectional view of a triple-shell liquid storage tank according to the present invention. FIG. 2 is an explanatory view of a conventional liquid storage tank.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-88297 (JP, A) JP-A-59-164499 (JP, A) Actually opened 60-54900 (JP, U) Actually opened 60- 101294 (JP, U) Actually open 51-98813 (JP, U) Actually open 59-20098 (JP, U) Actually open 59-22399 (JP, U)

Claims (1)

[Claims] 1. A sealed inner tank for storing low-temperature liquefied gas, in which a bottom slab, a side wall and a ceiling are integrally formed independently, and an independent sealed liquid levee that surrounds and accommodates the inner slab and side wall. It consists of an intermediate tank for use and an independent sealed outer tank that encloses and houses the bottom plate and side walls of the intermediate tank and the ceiling of the inner tank. A cooler is attached to the entire inner surface of the outer tank, and Triple shell liquid storage tank with each slab, side wall and ceiling made of RC concrete or PC concrete.