JP2008296945A - Double-hull tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely perform detection of leakage of a double-hull tank laid under the ground. <P>SOLUTION: The double-hull tank 10 has a double structure having an inner hull 80 consisting of a steel tank and an outer hull 90 consisting of a resin tank made of an FRP formed so as to cover the outer periphery of the inner hull 80. A sensor 154 of a liquid level detecting sensor 150 is an electrostatic capacity type sensor for detecting electrostatic capacity in accordance with change in the liquid level, and is inserted into a liquid poured into a leakage detecting cylinder 60. When the liquid level in the leakage detecting cylinder 60 is elevated or lowered by using the height of the liquid level set when the double-hull tank 10 is constructed as a reference value, the liquid level sensor 150 outputs an electrostatic capacity value corresponding to the amount of displacement as a detected signal from an outputting part 156. When an elevation of the liquid level in the leakage detecting cylinder 60 is detected, it becomes possible to judge that a fuel leaks from the inner hull 80, and when a lowering of the liquid level in the leakage detecting cylinder 60 is detected, it becomes possible to judge that the liquid 160 flows out into the underground. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a double-shell tank, and more particularly to a double-shell tank that is buried in the basement and is provided at the top of a double-shell tank that stores fuel such as oil.

  For example, in a refueling facility such as a gas station, an underground tank is buried in the site, and the oil liquid delivered by a tank truck is stored in the underground tank.

In recent years, in underground tanks, pinholes due to corrosion have occurred when buried underground, causing fuel stored in the tank to leak into the ground or underground water to flow into the tank. It has become. Double shell tanks have been developed to prevent such underground leakage.
As seen in Patent Document 1, the double shell tank is a double shell in which an FRP resin tank (outer shell) is provided on the outer periphery of a steel tank (inner shell) formed by joining cylindrical steel plates by welding. It has a structure that is strong enough to withstand earth pressure from the surroundings and that can withstand corrosion caused by groundwater.

Furthermore, in the underground tank, a detection space for leakage detection is provided between the outer periphery of the steel tank and the resin tank, and a detection cylinder communicating with this detection space is passed through from the tank top to the tank bottom, and the liquid level at the tank bottom. A detection sensor is provided. The liquid level detection sensor outputs a detection signal when a pinhole is generated in the resin tank and groundwater enters the detection space, or when oil liquid leaking from the steel tank enters the detection space.
Utility Model Registration No. 2577578

  However, in the above liquid level detection method, depending on the underground tank burial location, there may be no groundwater, and in that case, even if a pinhole occurs in the resin tank, groundwater does not enter the detection space, There was a problem that it could not be detected.

  In addition, when rainwater enters the detection space from the top of the tank, the liquid level detection sensor outputs a detection signal, which causes a problem of reducing reliability due to malfunction.

  Therefore, in view of the above circumstances, an object of the present invention is to provide a double shell tank that solves the above problems.

  In order to solve the above problems, the present invention has the following means.

The present invention comprises a steel inner shell for storing liquid;
A resin outer shell provided outside the inner shell, a leak detection space provided between the outer periphery of the inner shell and the outer shell except for the top of the inner shell, and a lower end at the bottom of the inner shell A detection tube that penetrates through the detection space and communicates with the detection space, and has an upper end protruding outside from the top of the inner shell, a leakage detection liquid injected into the detection tube and the leakage detection space, and the detection tube And a leak detection sensor for detecting a liquid level position of the leak detection liquid.
The present invention provides a communication path forming member that forms a communication path that communicates with the leakage detection space between the outer periphery of the top portion of the inner shell and a communication path that is communicated with the communication path and protrudes upward from the top portion of the inner shell. The present invention solves the problem by providing a discharge port for discharging the air in the leak detection space when the leak detection liquid is injected.
In the present invention, when the liquid level position of the leakage detection liquid rises, the leakage detection sensor detects that groundwater has flowed into the leakage detection space from the outside, and the liquid level position of the leakage detection liquid is The problem is solved by being provided so that it can be detected that the leakage detection liquid has flowed to the outside when it is lowered.
The present invention solves the problem by having a corrosion-resistant layer whose inner surface is coated with a material insoluble in the liquid at least up to the position of the maximum allowable liquid level of the inner shell.

  According to the present invention, the lower end of the inner shell communicates with the detection space through the bottom of the inner shell, and the upper end of the detection tube protrudes outward from the top of the inner shell, and the leakage detection liquid injected into the leakage detection space. Since the surface change is detected by the leakage detection sensor, leakage from the inner shell and leakage from the outer shell can be accurately detected, and the reliability of leakage detection can be improved.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a perspective view showing an embodiment of a double shell tank according to the present invention. As shown in FIG. 1, the double shell tank 10 is mounted on a concrete foundation 20 provided underground, and is embedded in a state surrounded by earth and sand. Also, at the top of the double-shell tank 10, an oiling pipe 32 to which an unloading hose from a tank truck is connected, a pipe joint 34 to which an oil supply pipe 40 is connected, a leak detection part 50, and a liquid suction pipe A connecting portion 70 is provided.

  FIG. 2 is a partial cross-sectional view showing the configuration of the double shell tank 10. As shown in FIG. 2, the double shell tank 10 has an inner shell 80 made of a steel tank and an outer shell 90 made of an FRP resin tank formed so as to cover the outer periphery of the inner shell 80. It has a heavy structure.

  Further, on the inner peripheral surface of the inner shell 80, a corrosion-resistant layer 82 coated with a material that is not soluble in the oil liquid, for example, an epoxy resin, is formed at least up to the maximum allowable liquid level height position of the inner shell 80. Yes. Thereby, the inner shell 80 can prevent corrosion from the inner peripheral surface. The corrosion-resistant layer 82 is not limited to the resin material described above, and may be a structure in which a thin sheet made of stainless steel having corrosion resistance is attached to the inner shell 80 at least at the maximum allowable liquid level position with an adhesive.

  A space securing member 100 made of a thin resin sheet (for example, a vinylon cloth having a thickness of 0.5 mm) is interposed between the inner shell 80 and the outer shell 90. Since this space securing member 100 is formed of a film-like material that is thinner than the gap between the inner shell 80 and the outer shell 90, the space securing member 100 is in close contact with the outer peripheral surface of the inner shell 80, so 110 may be formed between the inner peripheral surface of the outer shell 90. In addition to the resin sheet, the space securing member 100 may be made of a thin and water-absorbing sheet such as a resin fiber layer or Japanese paper.

  A leak detection cylinder 60 is inserted into the cylindrical shape of the leak detection unit 50. The leak detection cylinder 60 is provided so as to penetrate the inner shell 80 in the vertical direction, the lower end 62 communicates with the leak detection space 110 at the bottom of the tank, and the upper end protrudes above the top of the double shell tank 10. The upper end 64 of the leak detection cylinder 60 is used as an inlet for injecting a liquid (antifreeze) into the leak detection space 110, and is used as a mounting portion for a leak detection sensor for detecting the liquid level after installation. .

  FIG. 3 is a longitudinal sectional view of the double shell tank 10 taken along the line XX in FIG. As shown in FIG. 3, the double shell tank 10 is determined such that the maximum allowable liquid level height position Hmax is 90% of the total tank capacity. Therefore, the double shell tank 10 is unloaded from the tank truck until the maximum allowable liquid level height position Hmax is reached.

The outer shell 90 is formed not to cover the entire circumference of the inner shell 80 but to cover the outer circumference excluding the top 120 above the maximum allowable liquid level height position Hmax. Accordingly, the leakage detection space 110 is also formed with the maximum allowable liquid level height position Hmax as the upper limit.
FIG. 4 is an enlarged longitudinal sectional view showing a portion A shown in FIGS. As shown in FIG. 4, the leak detection space 110 is not formed at the top 120 of the inner shell 80, and the inner shell 80 and the outer shell 90 that are below the maximum allowable liquid level height position Hmax are formed. A space securing member 100 is interposed therebetween. At the upper end of the leak detection space 110, the edge 92 of the outer shell 90 is directly fixed to the outer periphery of the inner shell 80, so that the liquid injected into the leak detection space 110 does not move further upward. ing. Furthermore, since the surface of the edge 92 of the outer shell 90 and the surface of the top 120 of the inner shell 80 are coated with a resin material 130 such as FRP, for example, rainwater or the like cannot enter the leak detection space 110. The space between the top 120 of the inner shell 80 and the edge 92 of the outer shell 90 is sealed.
FIG. 5 is an enlarged longitudinal sectional view showing a portion B shown in FIG. As shown in FIG. 5, the lower end 62 of the leak detection cylinder 60 is in contact with the porous member 140. The porous member 140 functions as a filter that prevents foreign matter in the leak detection cylinder 60 from entering the leak detection space 110, and prevents the leak detection space 110 from being clogged with foreign matter. Furthermore, the porous member 140 also functions as a spacer that sets the distance between the lower end 62 of the leak detection cylinder 60 and the inner peripheral surface of the outer shell 90.

  Here, the leakage detection unit 50 will be described with reference to FIG. As shown in FIG. 6, a liquid level detection sensor 150 that detects a change in the liquid injected into the leak detection cylinder 60 is attached to the upper end 64 of the leak detection cylinder 60 inserted into the leak detection unit 50. Yes. The liquid level detection sensor 150 outputs a lid 152 that closes the upper end 64 of the leak detection cylinder 60, a sensor unit 154 that is held on the lower surface of the lid 152 and formed in a bar shape, and a detection signal that is detected by the sensor unit 154. Output unit 156.

  The sensor unit 154 is, for example, a capacitance type sensor that detects a capacitance according to a change in the liquid level, and is inserted into the liquid injected into the leak detection cylinder 60. Further, the liquid level of the liquid 160 injected into the leak detection cylinder 60 is set to be positioned above the maximum allowable liquid level height position Hmax. As a result, when a leak occurs in the inner shell 80 when the liquid level in the tank reaches the maximum allowable liquid level height position Hmax, the liquid level of the liquid 160 is lowered and the leak detection in the inner shell 80 is possible. To.

  The liquid level detection sensor 150 is composed of a capacitance type liquid level gauge, in which an inner cylinder having an inner cylindrical electrode and an outer cylinder having an outer cylindrical electrode are concentrically arranged. The electrostatic capacitance according to the height of the liquid which flowed into the cylindrical space formed between the two is detected. Therefore, when the liquid level in the leak detection cylinder 60 rises or falls with the liquid level height set at the time of construction of the double-shell tank 10 as a reference value, the liquid level detection sensor 150 is static according to the amount of displacement. The capacitance value is output from the output unit 156 as a detection signal.

  Therefore, when an increase in the liquid level in the leak detection cylinder 60 is detected by the liquid level detection sensor 150, it can be determined that fuel is leaking from the inner shell 80, and the liquid level in the leak detection cylinder 60 can be determined. When the descent is detected by the liquid level detection sensor 150, it can be determined that a pinhole is generated in the outer shell 90 and the liquid 160 has flowed out into the ground.

  Further, in the case where groundwater is accumulated around the double shell tank 10, if a pinhole is generated in the outer shell 90, the groundwater flows into the leak detection space 110. The rise in the liquid level is detected. Further, when the amount of stored oil in the inner shell 80 is reduced, if a pinhole is generated in the inner shell 80, the liquid 160 flows out to the inner shell 80. A liquid level drop in 60 is detected.

  As described above, the liquid level detection sensor 150 does not detect the liquid flowing into the leak detection space 110 as in the prior art, but detects the liquid level change in the leak detection cylinder 60 to detect the liquid level in the double shell tank 10. Since leakage detection is performed, it is possible to accurately detect leakage. Therefore, the liquid level detection sensor 150 that detects the liquid level in the leak detection cylinder 60 can accurately detect the leak from the inner shell 80 and the leak from the outer shell 90, thereby improving the reliability of leak detection. It becomes possible.

In the present embodiment, the configuration using a capacitive liquid level gauge as the liquid level detection sensor 150 has been described as an example, but other liquid level gauges (for example, the liquid level is irradiated with ultrasonic waves). Of course, an ultrasonic liquid level gauge or the like that detects the liquid level from the time until the reflection is received may be used.
Here, the configuration of the connection unit 70 will be described. FIG. 7 is an enlarged vertical sectional view showing the connecting portion 70. As shown in FIG. 7, the connecting portion 70 is formed between the communication path forming member 180 formed so as to cover the top 170 of the inner shell 80, and between the top 170 of the inner shell 80 and the communication path forming member 180. Air discharge space 190, discharge pipe 200 whose lower end communicates with air discharge space 190, and closure plug 210 that closes the upper end of discharge pipe 200.
The air discharge space 190 is an arc-shaped space formed so as to cover the top portion 170 of the outer shell 90, and both ends thereof communicate with the leak detection space 110 below the communication path forming member 180. The air discharge space 190 constitutes a discharge passage for discharging the air remaining in the leak detection space 110 to the outside when the liquid 160 is injected into the leak detection space 110.

  Furthermore, the surface of the communication path forming member 180 is coated with a resin material 220 such as FRP, and the resin material 220 is also formed at the boundary between the peripheral edge of the communication path forming member 180 and the outer shell 90 with the discharge pipe 200. It is coated. Thereby, the peripheral part of the communicating path formation member 180 and the outer periphery of the discharge pipe 200 are hermetically sealed.

Next, a method for injecting the liquid 160 from the leak detection cylinder 60 into the leak detection space 110 will be described with reference to FIG. As shown in FIG. 8, in the double-shell tank 10 buried underground, the upper end of the leak detection cylinder 60 is inserted into the manhole 240 and the connection portion 70 is inserted into the manhole 250.
First, the stopper plug 210 is removed from the discharge pipe 200 of the connection portion 70 via the manhole 250, and instead, the suction pipe 310 of the negative pressure generator 300 is connected to the upper end of the discharge pipe 200.

  Subsequently, the liquid level detection sensor 150 is removed from the upper end of the leak detection cylinder 60 via the manhole 240. Then, the liquid 160 is injected into the upper end opening of the leak detection cylinder 60. At the same time, the negative pressure generator 300 is operated to discharge the air in the air discharge space 190 connected to the discharge pipe 200 to the outside. As a result, the air in the leak detection space 110 communicated with the air discharge space 190 is also sucked and discharged to the outside, so that a negative pressure is generated in the leak detection space 110 and the liquid 160 injected into the leak detection cylinder 60 leaks. It is possible to inject to the end of the detection space 110.

  When the liquid 160 reaches the connecting portion 70, the suction pipe 310 of the negative pressure generator 300 is removed from the discharge pipe 200, and the closing plug 210 is attached to the upper end of the discharge pipe 200 and closed. Thereby, the outflow of the liquid 160 from the connection part 70 and the inflow of air are prevented.

  Thereafter, the liquid level in the leak detection cylinder 60 is set to be positioned above the maximum allowable liquid level height position Hmax as shown in FIG. Then, the liquid level detection sensor 150 is inserted into the upper end opening of the leak detection cylinder 60 and fixed. As a result, the liquid 160 is entirely injected into the air discharge space 190 formed between the inner shell 80 and the outer shell 90, and leakage from the inner shell 80 or the outer shell 90 can be detected. Become.

  In the above embodiment, the underground tank installed at the gas station has been described. However, the present invention is not limited to this, and other fuels (for example, gas such as CNG and hydrogen supplied to the fuel cell vehicle) are stored. Of course, it can also be applied to heavy shell tanks.

It is a perspective view which shows one Example of the double shell tank by this invention. 2 is a partial cross-sectional view showing a configuration of a double shell tank 10. FIG. It is a longitudinal cross-sectional view of the double shell tank 10 along the XX line in FIG. It is a longitudinal cross-sectional view which expands and shows the A section shown in FIG.2 and FIG.3. It is a longitudinal cross-sectional view which expands and shows the B section shown in FIG. 4 is a longitudinal sectional view showing a configuration of a leakage detection unit 50. FIG. It is a longitudinal cross-sectional view which expands and shows the connection part. FIG. 6 is a side view for explaining a method for injecting liquid 160 from leak detection cylinder 60 into leak detection space 110.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Double shell tank 50 Leak detection part 60 Leak detection cylinder 70 Connection part 80 Inner shell 82 Corrosion-resistant layer 90 Outer shell 100 Space securing member 110 Leak detection space 120,170 Top part 140 Porous member 150 Liquid level detection sensor 154 Sensor part 156 Output unit 160 Liquid 180 Communication path forming member 190 Air discharge space 200 Discharge pipe 210 Closure plug 300 Negative pressure generator 310 Suction pipe

Claims (4)

A steel inner shell for storing liquid,
A resin outer shell provided outside the inner shell;
A leakage detection space provided between the outer periphery of the inner shell and the outer shell except for the top of the inner shell,
A detection cylinder in which a lower end penetrates the bottom of the inner shell and communicates with the detection space, and an upper end protrudes to the outside from the top of the inner shell;
A leakage detection liquid injected into the detection cylinder and the leakage detection space;
A leakage detection sensor provided in the detection cylinder for detecting a liquid surface position of the leakage detection liquid;
A double-shell tank characterized by comprising A communication path forming member that forms a communication path communicating with the leakage detection space between the outer periphery of the top of the inner shell, and
Communicating with the communication path, protruding upward from the top of the inner shell, and discharging the air in the leakage detection space when the leakage detection liquid is injected;
The double-shell tank according to claim 1, comprising:   The leak detection sensor detects that groundwater has flowed into the leak detection space from the outside when the liquid level position of the leak detection liquid rises, and when the liquid level position of the leak detection liquid drops The double-shell tank according to claim 1 or 2, wherein the leakage detection liquid is provided so as to be able to detect that the liquid has leaked to the outside.   The inner shell has a corrosion-resistant layer whose inner surface is coated with a material insoluble in the liquid at least up to the maximum allowable liquid level of the inner shell. Double shell tank as described in.

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