JP2002156099A - Corrosion prevention structure of tank bottom board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the corrosion in a tank bottom board of an outer tank. SOLUTION: A corrosion prevention structure of the tank bottom board is provided with a tank pedestal 11 provided on an upper face of a tank foundation part 3 and capable of arranging the tank bottom board 5 on an upper face and ventilating, a covered member 15 surrounding the tank pedestal 11 along the direction of surrounding, an introduction line 20 for making an inert gas 18 to flow into the tank pedestal 11 through the covered member 15, and an exhaust line for exhausting the inert gas 18 from the tank pedestal 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tank bottom plate corrosion preventing structure for preventing tank bottom plate corrosion.

[0002]

2. Description of the Related Art As shown in FIG. 5, a low temperature tank having a double shell structure for storing a low temperature liquefied gas such as LNG is placed on a plurality of piles 2 driven into the ground 1 in a state of being separated from the ground 1 while being separated from the ground 1. A tank bottom plate 5 of an outer tank 4 is laid on the tank base 3, and an inner tank 6 is provided on the tank bottom plate 5 via a plurality of cylindrical blocks (not shown). Tank bottom plate 7 is placed.

As shown in FIG. 6, a tank bottom plate 5 of the outer tank 4 is provided on a peripheral edge 8 of the tank bottom plate 5 of the outer tank 4.
A waterproof sealing material 9 such as silicone is applied from the lower portion of the tank side plate 10 to the tank base portion 3 so as to close the gap between the tank base portion 3 and the tank base portion 3.

Accordingly, it is possible to prevent moisture such as rainwater or snowmelt from entering the space between the tank bottom plate 5 of the outer tub 4 and the tank base portion 3 and to suppress corrosion of the tank bottom plate 5 of the outer tub 4. I have.

[0005]

However, even if the waterproof sealing material 9 is applied so as to cover the edge 8 of the tank bottom plate 5, the waterproof sealing material 9 will be cracked with the passage of time. There has been a problem that moisture such as snowmelt and air intrude between the tank bottom plate 5 of the outer tank 4 and the tank base 3, resulting in corrosion of the tank bottom plate 5.

The present invention has been made in view of the above circumstances, and has as its object to prevent corrosion of a tank bottom plate of an outer tank.

[0007]

According to the present invention, there is provided a tank bottom plate corrosion prevention structure which is laid on an upper surface of a tank base and which allows the tank bottom plate to be disposed on the upper surface, and a tank pedestal extending in the circumferential direction. , A feed line for flowing an inert gas through the coating member into the tank pedestal, and a discharge line for discharging the inert gas from the tank pedestal.

Further, in the structure for preventing corrosion of a tank bottom plate of the present invention, there is a structure in which a tank base is made of either porous concrete or porous asphalt.

When the tank is constructed, an inert gas is introduced into the tank pedestal from the introduction line through the covering portion to discharge moisture and air existing between the tank base and the tank bottom plate from the discharge line. Then, an inert gas is filled between the tank base and the tank bottom plate.

As described above, since the inert gas is flowed into the tank pedestal and sealed therein, an inert gas atmosphere is provided between the tank base and the tank bottom plate, so that corrosion of the tank bottom plate can be reliably prevented. Even when moisture and air newly enter from the outside air between the tank base and the tank bottom plate filled with inert gas, the inert gas is flown again to the tank base to discharge moisture and air. By doing so, the tank bottom plate can always be maintained in a corrosion-prevented state.

When the tank pedestal is made of porous concrete or porous asphalt, the tank pedestal can sufficiently withstand the load of the tank and can appropriately flow an inert gas, so that the tank pedestal is excellent in durability and the tank bottom plate can be formed. Corrosion can be more reliably prevented.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show a first example of a structure for preventing corrosion of a tank bottom plate according to an embodiment of the present invention.
5 and 6 indicate the same parts.

Between the upper surface of the tank base 3 and the tank bottom plate 5 of the outer tank 4, a tank pedestal 11 having the same width and a predetermined thickness as the tank bottom plate 5 is laid.
It is made of a material selected from porous concrete and porous asphalt so as to withstand the load of the outer tank 4 and the inner tank 6 and to have air permeability.

The edge 8 of the tank bottom plate 5 of the outer tank 4
In the vicinity, a closed internal space is formed to form a tank bottom plate 5.
A covering member 15 composed of an upper surface portion 13 and a side surface portion 14 so as to cover the edge 8 and the side surface 12 of the tank pedestal 11 in the circumferential direction.
The upper part 13 of the covering member 15 is welded at the end to the lower part of the tank side plate 10, and the side part 14 of the covering member 15 is provided.
The lower end edge 16 is fastened to the tank base 3 via an anchor 17.

An introduction line 20 having an on-off valve 19 is provided at a predetermined position on the side surface 14 of the covering member 15 so that an inert gas 18 such as nitrogen gas or halogen gas can be introduced into the tank pedestal 11. An opening / closing valve 21 is provided on the side surface 14 of the covering member 15 located on the side opposite to the introduction line 20 so that the inert gas 18 in the tank base 11 can be discharged.
And a discharge line 23 provided with a dew point meter 22.

Here, the dew point meter 22 is for confirming whether or not the discharged inert gas 18 contains moisture. Reference numeral 24 shown in the figure denotes a safety valve.

The operation of the first embodiment of the present invention will be described below.

When the low-temperature tank is installed, the on-off valve 19 of the introduction line 20 is opened and the inert gas 1
8, an inert gas 18 flows into the tank pedestal 11 from an upstream half-circumferential position on the side surface 12 of the tank pedestal 11, and removes moisture and air existing between the tank base 3 and the tank bottom plate 5 with the inert gas. Tank pedestal 1 with 18
Discharge line 2 from the downstream half position on the side surface 12
After purging for a predetermined time, the on-off valve 21 of the discharge line 23 is closed and an inert gas is filled, so that the space between the tank base 3 and the tank bottom plate 5 is set to an inert gas atmosphere of atmospheric pressure or higher. .

After the construction of the low-temperature tank, the same operation is carried out periodically so that the space between the tank base 3 and the tank bottom plate 5 is always kept in an inert gas atmosphere at atmospheric pressure or higher. At this time, by measuring the discharged inert gas 18 with the dew point meter 22, it is possible to check how much water is contained in the inert gas 18 between the tank base 3 and the tank bottom plate 5. .

As described above, since the inert gas 18 is supplied to the tank pedestal 11 and sealed therein, the space between the tank base portion 3 and the tank bottom plate 5 becomes an inert gas atmosphere at a pressure higher than the atmospheric pressure. Corrosion of the tank bottom plate 5 can be reliably prevented by preventing entry of moisture such as water and air.
Further, even when moisture and air from the outside air newly enter between the tank base portion 3 and the tank bottom plate 5 filled with the inert gas 18, the inert gas 18 is allowed to flow through the tank pedestal 11 again. By discharging the water and air, the tank bottom plate 5 can always be maintained in a corrosion-prevented state.

When the tank pedestal 11 is made of either porous concrete or porous asphalt, the tank pedestal 11 can sufficiently withstand the load of the low-temperature tank and can appropriately flow the inert gas 18, so that it has excellent durability. In addition, corrosion of the tank bottom plate 5 can be more reliably prevented.

A second example of the tank bottom plate corrosion prevention structure according to the embodiment of the present invention will be described with reference to FIG. 3. The second example of the tank bottom plate corrosion prevention structure is the first example of the tank base 1 of the first example.
1 is changed. Note that, in the drawings, portions denoted by the same reference numerals as those in FIGS. 1 and 2 represent the same components.

The tank pedestal 25 is a structure in which a plurality of wells are combined to provide air permeability.
A large amount of inert gas 18 flows therein.

Therefore, the operation of the second embodiment of the present invention can obtain the same operation as that of the first embodiment.

A third example of the tank bottom plate corrosion prevention structure according to the embodiment of the present invention will be described with reference to FIG.
Is a modified version. Note that, in the drawings, portions denoted by the same reference numerals as those in FIGS. 1 and 2 represent the same components.

The covering member 26 is provided on the side 1 of the tank base 11.
Reference numeral 2 denotes a header pipe arranged along the circumferential direction, and an inlet 27 for the inert gas 18 is provided at a contact portion of the tank pedestal 11. Further, a sealing plate 28 is provided on the side surface 12 of the tank pedestal 11 that is not in contact with the header tube so that the inert gas 18 does not leak.

Further, an introduction line 20 and a discharge line 23 are provided at predetermined positions of the covering member 26 in the header tube, as in the first and second examples.

Therefore, the operation of the third embodiment of the present invention can also obtain the same operation as that of the first embodiment.

The structure for preventing corrosion of the tank bottom plate of the present invention is not limited to the above-described embodiment, and an inert gas may always flow through the tank pedestal.
The material of the tank pedestal may be any material as long as it can withstand a predetermined load and has air permeability, the discharge line may be directly attached to the tank pedestal, and the other points do not depart from the gist of the present invention. Of course, various changes can be made within the range.

[0031]

According to the structure for preventing corrosion of a tank bottom plate of the present invention, various excellent effects can be obtained as follows.

I) Since an inert gas is flowed and sealed in the tank base, an inert gas atmosphere is provided between the tank base and the tank bottom plate, so that corrosion of the tank bottom plate can be reliably prevented. Even when moisture and air newly enter from the outside air between the tank base and the tank bottom plate filled with inert gas, the inert gas is flown again to the tank base to discharge moisture and air. By doing so, the tank bottom plate can always be maintained in a corrosion-prevented state.

II) When the tank pedestal is made of porous concrete or porous asphalt, the tank pedestal can sufficiently withstand the load of the tank and can appropriately pass an inert gas, so that the tank pedestal has excellent durability and Corrosion of the bottom plate can be more reliably prevented.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view showing a first example of an embodiment of a tank bottom plate corrosion prevention structure of the present invention.

FIG. 2 is an overall plan view showing a first embodiment of a tank bottom plate corrosion preventing structure according to the present invention.

FIG. 3 is a longitudinal sectional side view showing a second example of the embodiment for implementing the tank bottom plate corrosion prevention structure of the present invention.

FIG. 4 is a vertical sectional side view showing a third example of the embodiment for implementing the tank bottom plate corrosion prevention structure of the present invention.

FIG. 5 is a vertical sectional side view showing the entire tank.

FIG. 6 is a longitudinal sectional side view showing a conventional structure for preventing corrosion of a tank bottom plate.

[Explanation of symbols]

 3 Tank Base 5 Tank Bottom Plate 11 Tank Base 15 Covering Member 18 Inert Gas 20 Introducing Line 23 Discharge Line 25 Tank Base 26 Covering Member

Claims (2)

[Claims] 1. An air-permeable tank pedestal laid on the upper surface of a tank base and capable of disposing a tank bottom plate on the upper surface, a covering member surrounding the tank pedestal along a circumferential direction, and the tank member passing through the covering member. And a discharge line for discharging an inert gas from the tank pedestal. 2. The structure for preventing corrosion of a tank bottom plate according to claim 1, wherein the tank pedestal is made of either porous concrete or porous asphalt.