JPH0125864B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a technology for installing a storage tank for storing low-temperature liquids such as LNG, and more specifically, a method for installing a semi-underground storage tank in which a storage tank completed in advance in a dock is towed to the site and installed. Regarding.

[B] Conventional technology Many storage tanks are constructed in coastal areas where construction equipment and personnel are disadvantageous, making it difficult to construct them.

Therefore, as a method of constructing a storage tank to simplify the construction, for example, Japanese Patent Laid-Open No. 57-172076 and Japanese Patent Laid-Open No. 57-172
The construction method disclosed in Publication No. 172078 is known.

In all of these construction methods, the storage tank is manufactured in an unfinished state on the land side in advance, taking into account weight reduction.
This method involves towing this to the site and submerging it.

[B] Problems with the conventional technology The conventional storage tank installation technology described above has the following problems.

(1) Although this method simplifies construction somewhat compared to the construction method of constructing a storage tank from scratch on site, it still requires on-site construction to complete the storage tank.

(2) Previously, a cavity was created in the walls of the storage tank to reduce weight for towing purposes.

After the storage tank is installed, these cavities are filled with concrete or sand to eliminate the cavities, but filling the cavities requires a lot of work.

[C] Purpose of the present invention The present invention has been made in order to solve the above-mentioned problems, and provides a method for constructing a storage tank that eliminates the need for the process of constructing a storage tank at the installation site and can significantly shorten the construction period. The purpose is to provide an installation method.

[D] Example The method of installing a storage tank according to the present invention will be described below with reference to the drawings, but first the structure of the storage tank (liquid storage tank) to be installed will be briefly described.

(1) Storage tank As shown in Figures 1 and 2, the storage tank 1 has a triple-shell structure consisting of an inner tank 2 for storing low-temperature liquid such as LNG, and an outer tank 3 with a double-shell structure for storing this inner tank 2. It is the body.

(2) Outer tank Outer tank 3 is a completely sealed box and is made of high-strength prestressed concrete, reinforced concrete, etc.

Furthermore, the outer tank 3 is a structure that has both the function of a barge and, after installation, the function of a liquid barrier for the storage tank.

The outer tank 3 has a bottom, sides, and upper part formed of a concrete double shell consisting of an inner shell 31 and an outer shell 32, and the inner space is formed by partition walls 3 having a double shell structure in the vertical and horizontal directions.
3 to form independent storage chambers 34.

(3) Inner tank The inner tank 2 is a completely sealed tank made of stainless steel or aluminum alloy, such as a membrane type or semi-membrane type tank.

This inner tank 2 is stored in the storage chamber 34 of the outer tank 3 via a heat insulating material 4.

The heat insulating material 4 is interposed over the entire area of the inner tank 2 using, for example, polyurethane foam.

The above is the outer tank 3 with the upper part released inside the dry dog.
After constructing a tank and storing the inner tank 2 inside this outer tank 3,
Construct the outer tank 3 by closing the upper opening. (3rd
(Figure) As a result, each inner tank 2 is housed independently within the outer tank 3, which is made of a double shell of concrete with excellent strength.

Next, a method of installing the storage tank 1 having the above structure will be explained.

(1) Towing the storage tank (Fig. 4) Launch the tank into the tank 1 built inside Drydog,
Towed on the sea.

At this time, ballast water such as seawater is introduced into the storage tank 1 to ensure stability during towing.

Since the outer tank 3 constituting the storage tank 1 is formed to have a double shell structure with excellent strength, even if the storage tank 1 is subjected to various external forces such as waves and wind force during towing, it can sufficiently resist.

(2) Preparation for installation Meanwhile, on the land side where the storage tank 1 is to be installed, preparations for installation are made by excavating an inlet-shaped trench 5 for guiding and installing the storage tank 1 to the land area.

This groove 5 is cut in consideration of width, depth, etc. so that the storage tank 1 can be introduced in a floating state.

(3) Bottoming out The towed storage tank 1 is guided into the excavated groove 5.

Next, the cut groove 5 is shut off, and water inside the cut groove 5 is drained.

As a result, the storage tank 1 gradually bottoms out in the cut groove 5.

(4) Backfilling When the storage tank 1 is completely brought to the bottom, backfilling 6 is performed in the space between the excavated trench 5 and the outer periphery of the storage tank 1 to complete the installation of the semi-underground storage tank 1.

[E] Effects Since the present invention is as explained above, the following effects can be expected.

(1) Conventional LNG storage tanks are large and heavy;
The present invention consists of an outer tank that is strong enough to withstand any impact during towing or installation, and an inner tank that stores LNG, etc. stored in the outer tank.

As a result, transportation by towing became possible.

(2) The outer tank has a double shell structure to provide strength.

Therefore, even when the tank is towed or operated as a storage tank, these external forces are not transmitted to the inner tank.

Furthermore, even if the outer shell is damaged due to impact on the outer tank, the inner shell reliably protects the inner tank, so there is no chance of liquid leakage.

(3) The double-walled outer tank is completely sealed, improving safety against gas and liquid leaks.

(4) Adopting a double-hull structure for the bottom plate increases rigidity, reduces the possibility of uneven settlement, and improves structural safety.

(5) The inside of the double shell of the outer tank can be used not only as a heating space, but also as a maintenance space where liquid leaks, gas leaks, etc. can be directly monitored.

(6) By using concrete that does not have low-temperature brittleness for the structure, it is possible to obtain secondary barriers and dikes with high structural reliability.

(7) The surrounding ground and the parts that come into contact with the outside air are made of concrete and are maintenance-free.

(8) Since it is constructed as a barge type and towed to the installation site for installation, it can be easily constructed even in cold regions where there is not enough construction time.

[Brief explanation of drawings]

FIG. 1: An explanatory diagram of an embodiment of a storage tank, FIG. 2: A partially sectional explanatory diagram of a storage tank, and FIGS. 3 to 5: An explanatory diagram of a method of installing a storage tank. 1: storage tank, 2: inner tank, 3: outer tank.

Claims (1)

[Claims] 1. In a dock, a steel inner tank is housed in an outer tank with a double shell structure with a gap between an inner shell and an outer shell made of concrete to form a storage tank with a triple shell structure. Once completed, the completed storage tank will be towed and transported to the planned construction site, the water area surrounding the tank introduced to the planned construction site will be closed off, this water area will be drained, the tank will be brought to the bottom, and a gap will be created inside the outer tank. A storage tank installation method that backfills the area around the tank while leaving it intact.