JP4540431B2 - Leak detection device in double shell tank - Google Patents

Description

  The present invention relates to a leak detection device in a double shell tank used for storing a combustible material (hereinafter referred to as a low boiling combustible material) having a boiling point of room temperature (approximately 20 ° C.) or less, such as liquefied natural gas (LPG). More particularly, the present invention relates to a leak detection device in a double-shell tank in which a reinforced plastic layer is formed on the surface of a steel tank, which is used underground to store low-boiling combustibles. .

  Dangerous goods with reinforced plastic-lined double-shell tanks that have been revised and enforced under the Law that revises part of the regulations on the regulation of dangerous goods and the part of regulations that regulate the regulation of dangerous goods. Can be stored.

  For example, as shown in FIGS. 14 and 15, the reinforced plastic-lined double-shell tank has a portion (liquid phase portion L) other than the upper portion and the flange portion (gas phase portion G) outside the steel tank a. In FIG. 2, a reinforced plastic layer c is provided while forming a minute gap b to form a tank body d, and a detection tube e communicating with the minute gap 2 is inserted from the top to the bottom of the tank body 4 and is not shown. However, a sensor capable of detecting both a dangerous substance leaking from the tank a and a groundwater flowing from the reinforced plastic layer c is disposed at the bottom of the detection pipe e, and an output from the sensor is further provided at an appropriate location. Is provided with a detection device for processing.

  Such a double-shell tank is currently installed in a gas station or the like, and is currently used as a storage tank for storing dangerous substances (type 4) that are flammable liquids at room temperature, such as gasoline.

  As a double-shell tank for storing dangerous substances that are flammable liquids at room temperature such as gasoline, in addition to the type of tank configured as shown in FIGS. There are products on the market that have pipes that contain sensors and those that contain a vapor sensor in a minute gap.

  On the other hand, when the above double shell tank is used as a tank for storing low boiling point combustible materials, it is confirmed that the results of the water pressure test etc. meet the standard by conducting a prescribed water pressure test etc. However, if the above double shell tank is used for a long period of time, the inner steel tank will corrode etc., and since it is a low boiling point combustible material, high pressure is applied to the steel tank from the inside. Therefore, there is a risk of leakage of low boiling point combustibles. Therefore, it is necessary to prepare a configuration that can detect a low boiling point combustible material quickly and accurately when a leak occurs.

  However, even if a double shell tank having a water level sensor disposed at the bottom of the detection tube as shown in FIGS. 14 and 15 is used as a tank for storing low boiling point combustible materials as it is, the above water level sensor is used. The boundary of whether or not it is possible is a liquid having a vapor pressure of 100 kpa or more at room temperature, and low boiling point combustibles having a boiling point of LPG (both butane and propane) or the like cannot be detected. And in the conventional system as shown in FIG. 15, when the leakage of a low boiling point combustible material generate | occur | produces, this cannot be detected.

 In order to detect leakage of low boiling point combustibles in the above double shell tank, it may be possible to enclose a vapor sensor inside the minute gap of the tank at the time of manufacturing the tank. If the vapor sensor fails, there is a problem that the tank itself cannot be used.

  Furthermore, in the case of low boiling point combustibles, unlike gasoline, the internal pressure of the tank is high, so when the tank is used, not only the diameter of the tank body increases, but also the expansion and contraction are repeated depending on the temperature. A problem that internal stress is generated at the joint between the tube e and the tank, or even if a slight amount of stress is applied intermittently, there is a risk of leakage of low boiling point combustibles due to cracks, cracks, etc. There is also.

  The present invention has been made to solve the above-described problems of the prior art, and the object of the present invention is to store a low-boiling combustible in a double-shell tank, and to lower the low-boiling combustible from the double-shell tank. Low-boiling combustible storage that can detect leaks quickly and accurately, and does not cause internal stress due to expansion of the tank body due to tank internal pressure. An object of the present invention is to provide a leak detection device for a double shell tank.

In order to solve the above-mentioned problem, the invention described in claim 1 is a reinforced plastic in which a reinforced plastic layer is formed on a surface of a steel tank through a micro gap so as to store a combustible material having a boiling point of room temperature or lower. A leak detection device for a lining double shell tank,
A detection tube communicating with the minute gap is erected in the steel tank, and a check valve that is opened by a predetermined pressure from the minute gap side is interposed in the middle of the detection tube outside the steel tank. In the double shell tank, wherein the tip of is opened in a detection box disposed at the top of the steel tank, and a sensor for detecting the combustible material is disposed in the detection box. This is a leak detection device.

  Further, in the invention described in claim 2, the detection tube has its tip portion protruding into the detection box, and a main portion excluding the tip portion is disposed in the steel tank, and the detection tube The double-shell tank according to claim 1, wherein a rear end portion of the pipe is communicated with the minute gap from the inside of the steel tank, and the main portion of the detection pipe is a curved pipe at least partially. This is a leak detection device.

  Further, in the invention described in claim 3, the detection tube is erected on the tank so as to communicate with the minute gap via a plate-like member fixed to the steel tank. It is a leak detection apparatus in the double shell tank described in 1.

  According to a fourth aspect of the present invention, the plate-like member for erecting the detection tube on the steel tank is fixed to the steel tank via a bolt welded to the surface of the steel tank. It is the leak detection apparatus in the double shell tank of Claim 3.

  Furthermore, in the invention described in claim 5, the plate-like member for erecting the detection tube on the steel tank is fixed to the surface of the steel tank with an adhesive. This is a leak detection device in a heavy shell tank.

  The invention described in claim 6 is the invention according to any one of claims 1 to 5, wherein a branch pipe is interposed in the detection pipe at a position closer to the tank than the check valve in the detection box. It is a leak detection device in a double shell tank.

  According to the present invention, when a low boiling point combustible material such as LPG is stored in a double shell tank, and a leakage of the low boiling point combustible material occurs from the double shell tank, this can be detected quickly and accurately. In addition, it is possible to provide a leak detection device in a double-shell tank for storing low-boiling combustibles, in which internal stress due to expansion of the tank body due to the internal pressure of the tank does not occur.

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

Embodiment 1
1 and 2 are configuration diagrams showing a double shell tank to which a leak detection device in a double shell tank according to Embodiment 1 of the present invention is applied.

  1 and 2, reference numeral 1 denotes a tank body, and the tank body 1 is composed of a steel inner shell tank 1a formed in a predetermined substantially cylindrical shape. The steel inner shell tank 1a has, for example, a diameter (outer diameter) of 1220 mm and a length of 2257 mm (however, the coating layer 1d described later is not included). The tank main body 1 is not necessarily composed of the steel inner shell tank 1a itself, but on the surface of the steel inner shell tank 1a, as shown in FIG. 3, the antirust coating 1b and the film layer 1c. Of course, it may be one that has been processed before coating. Further, at both ends in the longitudinal direction of the tank body 1, as shown in FIG. 1, end plate portions 2 and 3 formed in a predetermined curved shape are provided in order to improve pressure resistance and the like.

  The tank to which the present invention is applied is installed in a state where it is buried in the ground such as a gas stand, and is used as a storage tank for storing low-boiling combustibles such as LPG. This storage tank is configured as a double-shell tank in which a coating layer 1d made of an FRP layer or the like is coated on the outside of a steel inner shell tank 1a as required, and the inner shell tank 1a and the coating layer 1d Between them, a minute gap 4 of about 0.1 mm is formed. However, in this embodiment, the minute gap 4 is not formed in the portion 1e for mounting the detection box described later.

  As the coating layer 1d, a resin layer filled with glass fiber or the like and solidified is used. As the resin, isophthalic acid unsaturated polyester resin, bisphenol unsaturated polyester resin, vinyl ester resin, epoxy resin, or the like is used. As the glass fiber, a glass chopped strand mat, glass roving, treated glass cloth, glass roving cloth, or the like is used.

  By the way, the leak detection device in the double-shell tank according to this embodiment is a reinforced plastic in which a flammable plastic having a boiling point of room temperature or lower is stored, with a reinforced plastic layer being formed on the surface of a steel tank through a minute gap. A leak detection device for a lining double-shell tank, wherein a detection pipe communicating with the fine gap is erected on the steel tank, and a predetermined pressure from the fine gap side is provided in the middle of the detection pipe outside the steel tank. An open check valve is interposed, and the tip of the detection tube is opened in a detection box disposed at the top of the steel tank so as to detect the combustible material inside the detection box. It is configured.

  That is, as apparent from FIG. 2, the detection tube 5 has its tip 5a protruding into the inside of the hollow rectangular parallelepiped detection box 6 placed at the upper center of the tank body 1 as described above, and A main portion 5b excluding the front end portion is disposed inside the tank body 1, the rear end portion 5c of the detection tube 5 is communicated with the minute gap 4 from the inside of the tank body 1, and the main portion 5b of the detection tube. However, at least part of it is a curved pipe. The rear end portion 5 c of the detection tube 5 is preferably fixed along the radial direction of the tank body 1 inside the tank body 1.

  The main portion 5b of the detection tube only needs to be a curved tube at least at a part thereof, and a part of the main portion 5b may be a straight tube. The fixing position on the inner side of the main body 1 is not limited to that shown in FIG. 2, and for example, the position shown in FIG. 5 or 6 may be used.

  On the other hand, a detection device 7 is disposed at the tip 5 a of the detection tube 5 that protrudes into the detection box 6 on the tank body 1. As shown in FIG. 4, the detection device 7 is composed of a check valve 8 interposed at the distal end portion 5 a of the detection tube 5 and a U-shaped tube 9 containing the check valve 8. The check valve 8 presses a valve body 11 formed in a spherical shape by a coil spring 10 against a valve seat 12 and normally closes the detection tube 5, and particularly outside air containing water vapor enters the minute gap 4. The rust preventive paint applied to almost the entire surface of the tank 1 body is prevented from coming into contact with oxygen, and at the same time, when the pressure in the minute gap 4 of the tank body 1 rises above a predetermined value, the valve body 11 The low boiling point combustible material that moves upward against the pressing force of the coil spring 10 and leaks into the minute gap 4 is discharged into the detection box 6. The pressure at which the check valve 8 operates is set to a value that exceeds the normal pressure by about 10 to 50 kpa, for example.

  The configuration of the detection device 7 is not limited to the above. Normally, the detection tube 5 is closed, and at the same time, a low boiling point combustible material leaked when the pressure in the minute gap 4 rises to a predetermined value or more is detected. For example, the tip 5a of the detection tube 5 is formed so as to form a part of the outer shape of the sphere, and the valve formed in the outer shape of the sphere is formed on the tip 5a. You may make it fit a body.

  The low boiling point combustible material released into the detection box 6 and leaked into the minute gap 4 is detected by a gas detection sensor GD installed in the detection box 6 for detecting the low boiling point combustible material. The fact that the low boiling point combustible material has leaked into the minute gap 4 is warned by the output of the sensor GD activating an alarm device (not shown). In addition, as this gas detection sensor GD, although a normal thing can be used, it is desirable to use a thing with high detection accuracy.

Embodiment 2
Further, in this embodiment, a branch pipe 13 and a valve 14 are interposed at a position closer to the tank body 1 than the check valve 8 in the detection box 6. Normally, the branch 15 of the branch pipe 13 is closed. The valve 14 is opened, and the tank body 1 side is opened to the check valve 8, but if the branch 15 of the branch pipe 13 is opened and the valve 14 is closed, the tank body 1 side is branched by the branch pipe 13. 15 is open to the public.

  The branch pipe 13 is used when periodically inspecting the tank body 1 for leaks and the like, and as shown in FIG. When the tank body 1 is closed, the tank body 1 side is opened to the branch 15 of the branch pipe 13, and the inspection instrument 16 connected to the branch pipe 13 is connected to the minute gap 4 of the tank via the detection pipe 5. Periodic inspection can be performed by measuring changes in the applied positive pressure or negative pressure with the inspection device 16 by applying pressure or suctioning to negative pressure (about −100 kpa).

  If a three-way cock is used, it is not necessary to use the branch pipe 13 and the valve 14 separately.

Embodiment 3
In this embodiment, the detection tube is configured to stand on the tank so as to communicate with the minute gap via a plate-like member fixed to the steel tank.

  That is, in this embodiment, as shown in FIGS. 8 and 9, a metal (for example, a steel pipe) having an outer diameter of about 11 mm is detected at the center of the upper portion of the tank body 1 similar to that in the first embodiment. A pipe 17 is erected. A plate 18 for attaching the detection tube as shown in FIGS. 10 and 11 is fixed to the lower end portion of the detection tube 17 by welding or the like, and the inside of the detection tube 17 is as shown in FIG. The detection tube mounting plate 18 is configured to communicate with the back surface side of the detection tube mounting plate 18 through a communication hole 19 formed in the detection tube mounting plate 18. As the detection tube mounting plate 18, an iron plate having a thickness of about 0.6 to 2.0 mm, for example, 1.6 mm is used.

  Further, as shown in FIGS. 11B and 11C, the detection tube mounting plate 18 has substantially the same radius of curvature as the outer peripheral surface of the inner shell tank 1a, and is long on one side of the inner shell tank 1a. Or a long curved shape on both sides of the inner shell tank 1a, and by means of a round flat seat 21 and a nut 22 via a bolt 20 erected at a predetermined position above the inner shell tank 1a by welding or the like. It is fixed to the outer peripheral surface of the inner shell tank 1a. The tip of the bolt 19 is cut off at an excessively protruding portion after the detection tube mounting plate 18 is fixed. Further, as shown in FIG. 12, the detection tube mounting plate 18 is covered with a coating layer 1 d, and the detection tube 17 is configured to communicate with the minute gap 4 of the tank body 1.

  As shown in FIG. 11A, the detection tube mounting plate 18 is provided with a long hole 23 at its lower end to absorb the change in the distance between the bolts 20 due to the expansion of the tank body 1 diameter. Can be done. Further, as shown in FIG. 12, the detection tube mounting plate 18 is firmly fixed to the tank body 1 by a covering layer 1d made of a bolt 20 and an FRP layer in this embodiment.

  Further, as shown in FIGS. 8 to 10, the micro gap 4 provided in the tank body 1 is provided in a portion excluding a region corresponding to the detection box 24 similar to that in the first embodiment, In the region corresponding to the detection box, the minute gap 4 is not provided, and has a one-layer structure. As shown in FIG. 12, a gap 25 similar to the minute gap 4 is provided at the lower portion of the detection tube mounting plate 18 to form a two-layer structure.

  The gap 25 may be secured by attaching the detection tube mounting plate 18 separately from the tank body 1 via a washer or the like, but the shape of the detection tube mounting plate 18 and the tank main body 1 is fine. It may be formed naturally due to such differences.

  On the other hand, the detection tube mounting plate 18 is not limited to the case where it is bolted to the outer periphery of the tank body 1, and as shown in FIG. 13, the detection tube mounting plate 18 is bonded to the inner shell tank 1a. In this case, the belt 26 may be temporarily attached and the belt 26 may be removed after the bonding is completed.

  In this case, the detection tube mounting plate 18 is bonded to the tank main body 1 in part, not the entire back surface thereof, to absorb the deviation from the detection tube mounting plate 18 due to the diameter expansion of the tank main body 1. Can be done. Further, as shown in FIG. 13B, the detector tube mounting plate 18 is firmly fixed to the tank body 1 by the covering layer 1d made of adhesive force, FRP layer, and the like.

  In any case, in this embodiment, the detection device 27 is attached to the tip of the detection tube 17 in the detection box 24. However, the configuration and operation are the same as those in the first embodiment. The description is omitted.

  Also in this embodiment, by adopting the configuration described in the second embodiment, it is possible to perform a periodic inspection by measuring with the inspection device 16.

  In the above configuration, the leakage detector in the double shell tank according to the present invention stores the low boiling point combustible in the double shell tank and leaks the low boiling combustible from the double shell tank as follows. When this occurs, this can be detected quickly and accurately, and the possibility of internal stress due to expansion of the tank body due to the internal pressure of the tank is eliminated.

  While the double shell tank is used for a long period of time, a fine crack or the like may occur in the inner shell tank 1a, and the stored low boiling point combustible material may leak out. The low boiling point combustible material leaking from the inner shell tank 1a flows into the detection pipes 5 and 17 communicating with the minute gap 4 or the gap 25 through the minute gap 4 of the double shell tank, and the check valve 15 And is discharged into the detection boxes 6 and 24. As a result, the gas detection sensor GD disposed inside the detection boxes 6 and 24 detects the leakage of the low boiling point combustible material.

  As described above, in the present invention, when a low boiling point combustible material is stored in the double shell tank, and the leakage of the low boiling point combustible material occurs from the double shell tank, the gas detection sensor is provided via the detection tubes 5 and 17. This can be detected quickly and accurately by GD. In addition, since there is no need to insert a large-diameter detector tube into the double shell tank or to enclose a sensor, internal stress may occur due to the tank body expanding due to the internal pressure of the tank. In the case of occurrence, the detection tube 5 which is a curved tube absorbs in the first embodiment, and in the third embodiment, the influence is minimized by devising the fixing method of the detection tube mounting plate 18. Limit.

1 is a cross-sectional view showing a main part of a reinforced plastic-lined double-shell tank to which a leak detection device in a double-shell tank according to Embodiment 1 of the present invention is applied. FIG. 2 is a cross-sectional view showing the main part of a reinforced plastic-lined double-shell tank to which the leak detection device in the double-shell tank according to Embodiment 1 of the present invention is applied. FIG. 3 is a cross-sectional view of a part of the tank body. FIG. 4 is a cross-sectional view showing the configuration of the detection device. FIG. 5 is a configuration diagram showing the attachment state of the detection tube. FIG. 6 is a configuration diagram showing the attachment state of the detection tube. FIG. 7 is a configuration diagram showing a mounting state of the inspection device. FIG. 8 is a cross-sectional view showing a main part of a reinforced plastic-lined double shell tank to which a leak detection device in a double shell tank according to Embodiment 3 of the present invention is applied. 9 is a cross-sectional view taken along line AA of FIG. 8, showing a reinforced plastic-lined double-shell tank to which a leak detection device in a double-shell tank according to Embodiment 3 of the present invention is applied. FIG. 10 is a cross-sectional view showing a main part of a reinforced plastic-lined double-shell tank to which a leak detection device in a double-shell tank according to Embodiment 3 of the present invention is applied. FIG. 11 is a block diagram showing a detector tube mounting plate in a double shell tank according to Embodiment 3 of the present invention. FIG. 12 is a configuration diagram showing an attachment state of the detection tube attachment plate. FIG. 13 is a configuration diagram showing an attachment state of the detection tube attachment plate. FIG. 14 is a sectional view showing a conventional reinforced plastic-lined double shell tank. FIG. 15 is a sectional view showing a conventional reinforced plastic-lined double shell tank.

Explanation of symbols

1: Tank body 2, 3: End plate part 4: Fine gap 5, 17: Detection pipe 6, 24: Detection box 7, 27: Detection device 8: Check valve GD: Gas detection sensor 13: Branch pipe 14: Valve 18 : Plate for detecting tube mounting 25: Gap

Claims (6)

A leak detection device in a reinforced plastic lining double shell tank in which a flammable plastic layer is coated on a surface of a steel tank through a minute gap, and a flammable material having a boiling point of room temperature or lower is stored,
A detection tube communicating with the minute gap is erected in the steel tank, and a check valve that is opened by a predetermined pressure from the minute gap side is interposed in the middle of the detection tube outside the steel tank. In the double shell tank, wherein the tip of is opened in a detection box disposed at the top of the steel tank, and a sensor for detecting the combustible material is disposed inside the detection box. Leak detection device.   The detection tube has its tip portion protruding into the inside of the detection box, the main portion excluding the tip portion is disposed inside the steel tank, and the rear end portion of the detection tube extends from the inside of the steel tank. The leak detection device for a double-shell tank according to claim 1, wherein the main portion of the detection pipe is a curved pipe at least partially in communication with the minute gap.   The leak detection device for a double shell tank according to claim 1, wherein the detection pipe is erected on the tank so as to communicate with the minute gap via a plate-like member fixed to the steel tank.   4. The double shell according to claim 3, wherein the plate-like member for standing the detection tube on the steel tank is fixed to the steel tank via a bolt welded to the surface of the steel tank. Leak detection device in the tank.   The leak detection device for a double-shell tank according to claim 3, wherein the plate-like member for erecting the detection tube on the steel tank is fixed to the surface of the steel tank with an adhesive.   The leak detection device for a double shell tank according to any one of claims 1 to 5, wherein a branch pipe is interposed in the detection pipe at a position closer to the tank than the check valve in the detection box.