JP7390850B2 - Double shell tank and construction method for double shell tank - Google Patents

Description

One aspect of the present invention relates to a double-shell tank and a method for constructing a double-shell tank, and for example, relates to a double-shell petroleum fuel tank buried underground and a method for constructing the same.

Refueling stations, such as gas stations, have underground tanks. Fuel oil such as gasoline, diesel oil, kerosene, etc. is unloaded (injected) from tanker trucks and stored in underground tanks. The fuel oil in the underground tank is refueled (poured) into the vehicle via a measuring machine connected to the underground tank.

Large underground tanks are required by the Fire Service Act to have a double shell structure. The double shell tank of the present invention has a structure in which two tanks, an outer shell and an inner shell, are in close contact with each other in the upper part to form a contact area (adherence layer), and in the lower part, a sensing layer with a gap is formed. refers to something that has Examples of the double-shell tank include an SF double-shell tank in which the outer shell is made of resin and the inner shell is made of steel. However, in an SF double-shelled tank, if the outer shell made of resin is damaged due to deterioration over time or poor construction, groundwater or the like may infiltrate the inner shell. In this way, when the resin outer shell of an SF double-shell tank is damaged and groundwater, etc. can infiltrate into the inner shell, the SF double-shell tank has the double structure required by the Fire Service Act. This means that the requirements are not met. As a result, the SF2 heavy-shell tank in such a state requires measures such as replacement. Replacing a double-shell tank buried underground would require a huge amount of cost and labor, so even if the outer shell of an existing double-shell tank is damaged, it will not comply with the standards of the Fire Service Act. There is a need for countermeasures that meet the requirements and allow continued use. In addition, this problem is not limited to existing underground tanks, but similar problems may occur in the future with newly buried underground tanks, so similar countermeasures are required.

In addition, for underground tanks other than large ones, steel single-shell tanks may be used. In a steel single-shell tank, cracks may occur due to corrosion caused by underground water, and internal oil may leak into the ground, and/or groundwater may infiltrate into the tank. Therefore, in existing single-shell tanks, a lining layer of fiber reinforced plastic (FRP) is formed on the entire inside of the steel tank. However, in case of damage to the steel shell, it is difficult to ensure sufficient safety with the inner lining layer alone. Therefore, from the viewpoint of ensuring sufficient safety, it is desirable to take measures to ensure that such a single-shell tank has a safe structure even if the steel shell is damaged.

For example, Patent Document 1 discloses that an FRP layer, which is a deterioration prevention treatment layer, is formed in close contact with the entire inner wall surface of an existing steel tank A, and a water-permeable layer is provided on the entire inside of the deterioration prevention treatment layer. , a technique of arranging an airtight layer supported by a curved body has been disclosed. Although such an underground tank is not structurally equivalent to the double-shell tank of the present invention, it is said that it can facilitate the discovery of leaks.

Patent No. 3699466

Accordingly, one aspect of the present invention provides a double shell tank that can continue to function as a double shell regardless of the presence or absence of damage to the steel shell in the underground tank. Alternatively, to provide a method for constructing a double shell tank that can continue to function as a double shell irrespective of the presence or absence of damage to the steel shell of an existing underground tank that has already been buried.

A double shell tank according to one aspect of the present invention is
A double shell tank for storing oil liquid buried underground,
a first shell made of steel;
A lining layer made of FRP (Fiber-Reinforced Plastics) that is placed in close contact with the inner surface of the first shell;
A second shell made of FRP is arranged inside the lining layer so that the upper part is in close contact with the lining layer and the lower part is formed with a gap layer between the lining layer and the lining layer;
Equipped with
In the upper part, the first shell made of steel, the lining layer made of FRP, and the second shell made of FRP are in close contact with each other .

Further, a sensor for detecting at least one of oil leakage and groundwater infiltration is arranged in a gap layer formed at the bottom between the FRP lining layer and the FRP second shell. It is preferable to further include the following.

Further, it is preferable that the lining layer is disposed in close contact with the entire inner surface of the first shell.

A method for constructing a double shell tank according to one embodiment of the present invention is as follows:
A step of forming a lining layer made of FRP (Fiber-Reinforced Plastics) in close contact with the entire inner surface of a steel shell of an existing underground tank for storing oil liquid buried underground;
forming an FRP shell inside the lining layer so that the upper part is in close contact with the lining layer and a gap layer is formed at the lower part;
Equipped with
In the upper part, the existing underground tank made of steel, the lining layer made of FRP, and the shell made of FRP are in close contact with each other .

Moreover, the existing underground tank is preferably a double-shell tank in which an outer shell made of FRP is placed on the outside of a steel shell.

According to one aspect of the present invention, an FF double shell structure can be formed inside a steel shell, with the lining layer serving as the outer shell and the FRP shell serving as the inner shell. At this time, even if a portion of the steel shell is damaged, as long as it has a certain degree of strength, the lining layer will be protected.
This allows the double shell to continue functioning regardless of whether or not there is damage to the steel shell in the underground tank. In addition, not only when installing a new underground tank, but also for existing underground tanks that are already buried, the double-shell function continues regardless of whether or not there is damage to the steel shell of the underground tank. can.

1 is an example of a cross-sectional configuration diagram showing the configuration of a gas station in Embodiment 1. FIG. 1 is a sectional view showing an example of the configuration of an underground tank in Embodiment 1. FIG. FIG. 3 is a sectional view showing another example of the configuration of the underground tank in Embodiment 1. FIG. 1 is an example of a flowchart diagram showing main steps of a method for constructing a double shell tank for an existing underground tank in Embodiment 1. FIG. FIG. 6 is a diagram for explaining the strength against a leakage test by pressurizing the sensing layer in a comparative example of the first embodiment. FIG. 3 is a diagram for explaining the strength against a leakage test by pressurizing the sensing layer in the first embodiment. FIG. 6 is a diagram for explaining strength against internal tank load in a comparative example of the first embodiment. FIG. 3 is a diagram for explaining strength against internal tank load in Embodiment 1. FIG.

Embodiment 1.
FIG. 1 is an example of a cross-sectional configuration diagram showing the configuration of a gas station in Embodiment 1. In FIG. 1, at a gas station typified by a gas station, an underground tank 102 (double shell tank) for storing oil such as gasoline is buried underground. On the other hand, a weighing machine (refueling machine) 104 is arranged on the ground. Further, a piping inlet 116 for receiving fuel oil from the tank truck 106 is arranged on the ground. A pipe 111 extending upward from the underground tank 102 is connected to a pipe 112 extending to, for example, a weighing machine 104 by a pipe joint in a box pit 100 (an upper box of an underground tank) buried underground. Further, a pipe 113 extending upward from the underground tank 102 is similarly connected to a pipe 114 extending to, for example, a pipe inlet 116 by a pipe joint within the box pit 100. Further, when the pressure inside the underground tank 102 exceeds a predetermined value, the gas vaporized for pressure adjustment is released into the atmosphere from the release valve 130 via the pipe 114, for example. These pipes 111, 112, 113, and 114 are buried underground. Further, as will be described later, a sensor (not shown) that detects leakage of oil and/or infiltration of underground water due to damage to the underground tank 102 is disposed at the bottom of the underground tank 102 through the sensor pipe 115.

In addition to gas stations (GS) (or SS: service stations) that sell fuel oil (oil liquid) such as gasoline, diesel oil, and kerosene to general vehicles, gas stations include gas stations (GS) (or SS: service stations) that sell fuel oil (oil liquid) such as gasoline, diesel oil, and kerosene to general vehicles. It also includes refueling locations that supply fuel oil to vehicles (taxi, buses, trucks, etc.) used for this purpose. The fuel oil referred to herein may also include liquefied natural gas, liquefied hydrogen, and the like.

When the tanker truck 106 arrives at the refueling station, the piping of the tanker truck 106 is connected to the piping inlet 116 . Thereafter, the fuel oil carried by the tank truck 106 flows through the pipes 114 and 113 and is injected into the underground tank 102.

A weighing machine 104 placed on the ground pours (refuels) fuel oil 101 stored in an underground tank 102 into a vehicle 300 via pipes 111 and 112. For example, the fuel oil 101 stored in the underground tank 102 is transferred by a pump (not shown) disposed in the measuring machine 104.

Here, the box pit 100 is buried underground in order to inspect the underground tank 102. A manhole cover that can be opened and closed from the ground is placed above the box pit 100. Further, an entrance (not shown) through which a worker can enter and exit the underground tank 102 through the box pit 100 is arranged at the top of the underground tank 102.

FIG. 2 is a sectional view showing an example of the configuration of the underground tank in the first embodiment. FIG. 2 shows a cross-sectional view of the underground tank 102 shown in FIG. 1 at the position of the sensor pipe 115 when viewed from the side. In the underground tank 102, a lining layer 12 made of FRP (Fiber-Reinforced Plastics) is disposed in close contact with the inner surface of a steel shell 10 (first shell). The lining layer 12 is disposed in intimate contact with the entire inner surface of the steel shell 10. The lining layer 12 is preferably formed to have a thickness of about 2 to 3 mm, for example. Further, an FRP shell 14 (second shell) made of FRP is in close contact with the lining layer 14 at the upper part of the FRP shell 14, and a sensing layer 22 is provided at the lower part of the FRP shell 14, which is a gap layer between the lining layer 12 and the FRP shell 14 (second shell). is arranged inside the lining layer 12 so that a is formed. The entire surface or a wide range of the upper part of the FRP shell 14, excluding the area where piping and the like are arranged, is in close contact with the upper inner surface of the lining layer 14 to form a close contact area 20. A gap of about 0.05 mm to 1 mm (for example, 0.1 mm) is formed in the gap that will become the sensing layer 22 by arranging a gap forming body such as a 3D sheet or a spacer net, which is composed of a plurality of pillars. be done. Further, the plurality of pillars support the FRP shell 14 from below. The FRP shell 14 is preferably formed to have a thickness of about 2 to 6 mm, for example. The underground tank 102 constitutes a double shell tank (multi-shell tank) in which the steel shell 10 is an outer shell, the lining layer 12 is an intermediate shell, and the FRP shell 14 is an inner shell. In other words, in the underground tank 102 shown in FIG. 2, a double-shell tank is formed inside the steel shell 10, with the lining layer 12 serving as an outer shell and the FRP shell 14 serving as an inner shell.

The underground tank 102 is formed, for example, in the shape of a cylindrical barrel with both ends closed by hemispherical mirror plates. Therefore, the steel shell 10, the lining layer 12, and the FRP shell 14 are similarly formed into a bale shape. In the first embodiment, if the detection layer 22 is formed at the lower part of the cylindrical portion of the underground tank 102, the FRP shell 514 and the lining layer 12 may be brought into close contact with each other in the mirror plate portions at both ends. In other words, the detection layer 22 may be formed at the lower part of the cylindrical portion of the underground tank 102 in the radial direction, and may be brought into close contact with the cylindrical portion in the direction of the center axis of the circle.

In addition, it penetrates the top of the steel shell 10, the top of the lining layer 12, and the top of the FRP shell 14 from above the underground tank 102, passes through the storage space inside the FRP shell 14, and penetrates the bottom of the FRP shell 14. , the sensor pipe 115 is arranged so as to open into the detection layer 22. As the sensor piping 115, for example, a piping having a diameter of about 100 mm is used. The sensor 16 is placed on the detection layer 22 formed at the bottom between the FRP lining layer 12 and the FRP shell 14. The sensor 16 detects at least one of oil leakage and groundwater infiltration. For example, when damage such as cracks occurs in the FRP shell 14, oil stored in the FRP shell 14 leaks from the damaged part of the FRP shell 14 to the detection layer 22 and flows toward the bottom, causing the oil liquid stored in the FRP shell 14 to leak into the detection layer 22. It collects at the bottom of the. The sensor 16 detects oil leaked at the bottom of the detection layer 22. Furthermore, even if cracks or the like occur in both the steel shell 10 and the lining layer 12 and underground groundwater or the like intrudes into the detection layer 22, the sensor 16 detects the infiltrated groundwater at the bottom of the detection layer 22. do. In the example of FIG. 1, one sensor 16 is shown, but the invention is not limited to this. It is also preferable to arrange a plurality of sensors in the same way and separate the applications into oil liquid detection and groundwater detection. For example, a float sensor is used as the sensor 16.

FIG. 3 is a sectional view showing another example of the configuration of the underground tank in the first embodiment. FIG. 3 shows a case where an FRP shell 11 is further disposed outside the steel shell 10 shown in FIG. 2. The entire upper part of the FRP shell 11 is in close contact with the outer surface of the steel shell 10, and the lower part is arranged with a gap that serves as a detection layer. In other words, the underground tank 102 shown in FIG. 3 has a lining layer 12 and an FRP shell 14 inside a double-shell tank (SF2 double-shell tank) whose outer shell is an FRP shell 11 and whose inner shell is a steel shell 10. The configuration is further arranged. In such a case, the underground tank 102 is a double shell tank (multiple shell tank) having the FRP shell 11 as an outer shell, the steel shell 10 as a first intermediate shell, the lining layer 12 as a second intermediate shell, and the FRP shell 14 as an inner shell. ). In other words, in the underground tank 102 shown in FIG. 3, a double-shell tank is formed inside the steel shell 10, with the lining layer 12 serving as an outer shell and the FRP shell 14 serving as an inner shell.

In the example of FIG. 2, when the steel shell 10 is damaged by corrosion caused by underground water, etc., and in the example of FIG. Even if the tank is damaged, the structure of the FRP double-shell tank (FF double-shell tank) can be maintained, with the corrosion-resistant FRP lining layer 12 serving as the outer shell and the FRP shell 14 serving as the inner shell. Therefore, the function of the double shell can be continued regardless of the presence or absence of damage to the outer shell. Furthermore, in the underground tank 102 of the first embodiment, the FRP shell 14 has its upper part tightly adhered to the inner surface of the lining layer 12. Moreover, since the lining layer 12 is arranged in close contact with the inner surface of the steel shell 10, the FRP shell 14 and the lining layer 12 will not be crushed together by the load applied to the FRP shell 14. Therefore, the structure including the steel shell 10, the lining layer 12, and the FRP shell 14 can maintain sufficient strength against the load applied to the FRP shell 14.

FIG. 4 is an example of a flowchart showing the main steps of the method for constructing a double shell tank for an existing underground tank in the first embodiment. In FIG. 4, the method for constructing a double shell tank for an existing underground tank in Embodiment 1 includes a series of lining processing steps (S102), FRP inner shell processing steps (S106), and sensor placement steps (S108). Implement the process. Here, the existing underground tank is a single-shell tank made of steel, or a double-shell tank (SF double-shell tank) in which an outer shell made of FRP is placed on the outside of an inner shell made of steel. It is preferable that the double shell tank in Embodiment 1 is constructed.

As a lining processing step (S102), a lining layer 12 made of FRP is formed in close contact with the entire inner surface of a steel shell 10 of an existing underground tank for storing oil liquid buried underground. Specifically, for example, an FRP sheet containing glass fibers of a predetermined size made by impregnating glass fibers or the like with a resin as a reinforcing material is pressed with a roller or the like to defoam the sheet. It is pasted on the inner surface of the steel shell 10 and laminated until it reaches a predetermined thickness. Alternatively, it is also preferable to spray glass fiber or the like and a resin material onto the inner surface of the steel shell 10, and then defoaming by pressing with a roller or the like. Alternatively, it is also preferable to attach an FRP sheet that has been previously formed to a predetermined thickness to the inner surface of the steel shell 10 while degassing it by pressing it with a roller tool or the like.

As the FRP inner shell processing step (S106), the FRP shell 14 made of FRP is formed inside the lining layer 12 so that the upper part is in close contact with the lining layer 12 and a gap layer is formed at the lower part. Specifically, regarding the region on the inner surface of the lining layer 12 where the sensing layer 22 is to be formed, the same process as in the lining processing step (S102) is performed with the above-mentioned gap forming body being placed in the region (lower part) where the sensing layer 22 is to be formed. Next, an FRP sheet is applied to the inner surface of the lining layer 12 while degassing by pressing with a roller tool or the like, and the sheets are laminated to a predetermined thickness. Alternatively, it is also preferable to spray glass fiber or the like and resin onto the inner surface of the steel shell 10 and defoaming by pressing with a roller or the like. Alternatively, it is also preferable to attach an FRP sheet that has been previously formed to a predetermined thickness to the inner surface of the steel shell 10 while degassing it by pressing it with a roller tool or the like. As a result, in the upper part, it is possible to form a close contact region 20 in which the lining layer 12 and the FRP shell 14 are directly in close contact with each other. Further, a sensing layer 22 can be formed in the lower part. Here, the upper part where the contact area 20 is formed corresponds to the area above the intermediate height position of the FRP shell 14 in the height direction. For example, it is preferable that the area from the top of the FRP shell 14 to about 1/5 of the height of the FRP shell 14 corresponds to the area. Conversely, the lower part where the sensing layer 22 is formed includes the part other than the upper part where the contact area 20 is formed.

As the sensor arrangement step (S108), the sensor is penetrated from above the underground tank 102 through the top of the steel shell 10, the top of the lining layer 12, and the top of the FRP shell 14, passing through the storage space inside the FRP shell 14, and then passing through the storage space inside the FRP shell 14. The sensor pipe 115 is arranged so as to penetrate through the bottom of the sensor pipe 14 and open to the detection layer 22 . Then, the sensor 16 is placed at the bottom of the sensing layer 22 between the lining layer 12 and the FRP shell 14 through the inside of the sensor pipe 115 .

As described above, an existing single-shell tank made of steel or an SF double-shell tank composed of an inner shell made of steel and an outer shell made of FRP is further added with a lining layer having an adhesion region 20 and a detection layer 22. It can be modified to a double shell tank by adding the structure of the FF double shell tank with 12 and FRP shell 14.

FIG. 5 is a diagram for explaining the strength against a leakage test by pressurizing the sensing layer in a comparative example of the first embodiment.
FIG. 6 is a diagram for explaining the strength against a leakage test by pressurizing the sensing layer in the first embodiment. In the example of FIG. 5(a), in the comparative example, the FRP shell 514 serving as the inner shell does not have a surface that is in close contact with the lining layer 12, and there is some The structure is such that the FRP shell 514 is supported with water-permeable supports sandwiched therebetween. In the example of FIG. 5(a), the FRP shell 514 is supported by four supports shifted by 90 degrees vertically and horizontally, but the number of supports may be larger. In this manner, in the comparative example, the FRP shell 514 serving as an airtight layer is separated from the lining layer 12. In the comparative example, the layer on which the support is disposed serves as a water-permeable layer and also serves as a detection layer. If the steel shell 10 is damaged due to corrosion or the like, the lining layer 12 needs to function as an outer shell. In such cases, the presence or absence of leakage in the detection layer is important. In the comparative example, the FRP shell 514 serving as an airtight layer is separated from the lining layer 12 around the entire circumference, so it does not have the double-shell tank structure of the present invention and receives pressure from the entire circumference including the upper part. It ends up. Therefore, as shown in FIG. 5(b), the FRP shell 514 undergoes surface buckling and becomes a structure that is easily damaged. In addition, in the comparative example shown in FIG. 5(a), if the sensing layer (water permeable layer) between the FRP shell 514 and the lining layer 12 is filled with leaked liquid and left unattended, there is a risk of damage due to the hydraulic pressure. .

On the other hand, in the first embodiment, as shown in FIG. 6(a), the upper surface of the FRP shell 14 is closely bonded to the inner surface of the lining layer 12, so no pressure is applied from above. . As a result, as shown in FIG. 6(b), the FRP shell 14 has a structure in which surface buckling is less likely to occur and damage is less likely to occur. Therefore, in the first embodiment, sufficient strength can be maintained against the load applied to the FRP shell 14 that actually stores the fuel oil 101.

Generally, an underground tank is formed in the shape of a barrel with both ends of the tank closed by hemispherical mirror plates. In addition, the roundness of underground tanks varies depending on the burial conditions, and the quality of the end plates at both ends is not uniform. Therefore, in the above-described comparative example in which the FRP shell 514 and the lining layer 12 are separated, for example, when attaching a support with water passage grooves formed to the entire inner surface of the lining layer 12, it is necessary to fit it to the tank shape. is difficult. On the other hand, in the first embodiment, if the detection layer is formed at the lower part of the cylindrical part of the tank, the FRP shell 514 and the lining layer 12 may be brought into close contact with each other in the end plate parts at both ends, and the tank shape can be made to fit.

FIG. 7 is a diagram for explaining strength against internal tank load in a comparative example of the first embodiment.
FIG. 8 is a diagram for explaining strength against internal tank load in the first embodiment. In the example of FIG. 7A, in the comparative example, as described above, the FRP shell 514 serving as the inner shell does not have a surface that is in close contact with the lining layer 12, and the FRP shell 514 and the lining layer 12 A case is shown in which, for example, four supports are used between the two. Similarly, the number of supports may be larger. In the comparative example, since the FRP shell 514 serving as an airtight layer is separated from the lining layer 12, the FRP shell 514 does not have a supporting force particularly in the upper part against the load of the fuel oil 101 stored in the FRP shell 514. Or small. Therefore, as shown in FIG. 7(b), the FRP shell 514 receives a load only by the supporting force from the lower part, resulting in a structure that is prone to surface buckling. On the other hand, in the first embodiment, as shown in FIG. 8(a), the upper surface of the FRP shell 14 is closely bonded to the inner surface of the lining layer 12, so that the supporting force at the upper part is reduced. I can make it stronger. As a result, as shown in FIG. 8(b), the FRP shell 14 can have a structure in which surface buckling is less likely to occur. In particular, since the lining layer 12 is arranged in close contact with the inner surface of the steel shell 10, the FRP shell 14 and the lining layer 12 will not collapse together due to the load applied to the FRP shell 14. Therefore, in the first embodiment, sufficient strength can be maintained against the load applied to the FRP shell 14 that actually stores the fuel oil 101.

As described above, according to the first embodiment, an FF double shell structure can be formed inside the steel shell 10, with the lining layer 12 serving as the outer shell and the FRP shell 14 serving as the inner shell. Thereby, regardless of the presence or absence of damage to the outer shell of the underground tank 102, the function of the double shell with sufficient strength can be continued. In particular, regardless of the presence or absence of damage to the steel shell 10, the double shell function can be continued with sufficient strength inside the steel shell 10. In addition, it is not only possible to install a new underground tank 102, but also to install an existing underground tank with sufficient strength, regardless of the presence or absence of damage to the steel shell of the underground tank. Heavy shell functions can be continued.

The embodiments have been described above with reference to specific examples. However, the present invention is not limited to these specific examples.

Further, although the description of parts not directly necessary for the explanation of the present invention has been omitted, the necessary device configuration can be selected and used as appropriate.

In addition, all double-shell tanks and construction methods for double-shell tanks that include the elements of the present invention and whose design can be modified as appropriate by those skilled in the art are included within the scope of the present invention.

10 Steel shell 12 Lining layer 14,514 FRP shell 16 Sensor 20 Close contact area 22 Detection layer 100 Box pit 101 Fuel oil 102 Underground tank 104 Weighing machine 106 Tank truck 111, 112, 113, 114 Piping 115 Sensor piping 116 Inlet 130 Release valve 300 vehicle

Claims (5)

A double shell tank for storing oil liquid buried underground,
a first shell made of steel;
a lining layer made of FRP (Fiber-Reinforced Plastics) disposed in close contact with the inner surface of the first shell;
a second shell made of FRP disposed inside the lining layer such that an upper part is in close contact with the lining layer and a gap layer is formed between the lining layer and the lower part;
Equipped with
A double shell tank characterized in that the first shell made of steel, the lining layer made of FRP, and the second shell made of FRP are in close contact with each other in the upper part . At least one of leakage of the oil liquid and infiltration of groundwater, which is arranged in the gap layer formed at the bottom between the lining layer made of FRP and the second shell made of FRP. The double shell tank according to claim 1, further comprising a sensor for detecting. 3. The double-shell tank according to claim 1, wherein the lining layer is disposed in close contact with the entire inner surface of the first shell. A step of forming a lining layer made of FRP (Fiber-Reinforced Plastics) in close contact with the entire inner surface of a steel shell of an existing underground tank for storing oil liquid buried underground;
forming an FRP shell inside the lining layer so that the upper part is in close contact with the lining layer and a gap layer is formed at the lower part;
Equipped with
A method for constructing a double shell tank, characterized in that the existing underground tank made of steel, the lining layer made of FRP, and the shell made of FRP are in close contact with each other in the upper part . 5. The method for constructing a double-shell tank according to claim 4, wherein the existing underground tank is a double-shell tank in which an outer shell made of FRP is placed on the outside of the steel shell.

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