CFRP double shell structure of new and existing buried tank

Abstract

To provide a buried tank of a double shell structure in which CFRP is disposed on an outer shell and an inner surface of a new steel tank, or the CFRP is arranged on an inner surface of an existing buried tank.SOLUTION: A steel tank inner surface CFRP double shell structure includes: CFRP provided to cover an outer shell of a new steel tank and an inner periphery of the steel tank to prevent leakage of oil or hydrogen and synthetic fuel from the steel tank; a gap forming member disposed between the steel tank and the CFRP; a leakage detection sensor disposed between the steel tank and the CFRP to detect leakage of liquid of the steel tank; and notification means for notifying failure of the steel tank based on a detection output of the leakage detection sensor.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a buried tank with a double-shell structure in which the outer and inner shells of a newly constructed tank are made of CFRP, or the inner surface of an existing steel tank is made of CFRP. Specifically, the present invention relates to the outer and inner shells of a new tank made of carbon fiber reinforced plastic, carbon fiber reinforced plastic, or carbon fiber reinforced resin, and the inner CFRP double-shell structure of an existing buried tank. [Background technology]

[0002] Nowadays, underground steel tanks for storing oil are widely used at gas stations and the like. However, such underground tanks may deteriorate over time due to long-term use, and may develop corrosion or pitting, which may cause oil leaks. However, once a steel tank is buried, it is difficult to inspect the tank for corrosion or pitting from above ground. For this reason, for example, Patent Document 1 proposes a buried tank made of synthetic resin that does not require advanced processing technology, does not require labor to manufacture, and requires little construction labor.

[0003] Meanwhile, in recent years, there has been active development of fuel cell vehicles (FCVs (Fuel Cell Vehicles)) that do not emit harmful substances such as carbon dioxide. Fuel cell vehicles use hydrogen as fuel, which reacts with oxygen in the air to generate electricity in the on-board fuel cell, and this electricity drives an electric motor to run the vehicle. Such fuel cell vehicles use solvents such as toluene, xylene, and methyl alcohol as fuel. Therefore, such solvents need to be supplied to fuel cell vehicles, but existing buried tanks cannot accommodate this. For this reason, the inside of the buried tanks needs to be protected with CFRP. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2003-261195 A Summary of the Invention [Problem to be solved by the invention]

[0005] Once a gasoline or other oil leak occurs, it has a large impact on the environment, such as soil contamination. In particular, if the oil leak continues for a long period of time, not only will it contaminate the soil, but it can also seep into groundwater, etc., becoming a major social issue. In addition, measures to prevent oil leaks, synthetic fuel leaks, and hydrogen leaks will be necessary for newly installed tanks. Therefore, the present invention provides a tank to be buried underground with a double structure, detects corrosion and pitting in the steel tank at an early stage, and prevents soil contamination, etc., while also using CFRP on the outer and inner surfaces of new steel tanks. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the present invention provides a steel tank inner surface CFRP double shell structure comprising: a steel tank; CFRP covering the outer and inner periphery of the steel tank and preventing leakage of oil, synthetic fuel, and hydrogen from new and existing steel tanks; a gap forming member disposed between the steel tank and the CFRP; a leak detection sensor disposed between the steel tank and the CFRP and detecting leakage from corrosion or pitting of the steel tank; and an alarm means for alarming leakage from the steel tank based on the detection output of the leak detection sensor.

[0007] The leak detection sensor also detects leaks of oil, synthetic fuel, hydrogen, etc. from the CFRP and steel tanks. If cracks or holes form in the fiber-reinforced composite material due to long-term use, it can also detect liquid leakage from those locations.

[0008] In addition, a leak detection sensor is disposed in the gap formed between the steel tank and the CFRP. The leak detection sensor is disposed along the side and bottom surfaces of the steel tank and detects leaks of water, synthetic fuel, and hydrogen from corrosion holes or pitting holes in the steel tank and leads the leaks to a detector.

[0009] In addition, the gap forming member can be composed of 3D glass cloth, mesh-like wire mesh members, etc., and the above-mentioned leak detection sensor is configured to be able to detect synthetic fuel and hydrogen leaks, oil leaks, etc. from any direction. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing an example of an underground tank employing a double shell structure according to an embodiment. [Diagram 2] FIG. 2 is a diagram showing the cross-sectional configuration of an underground tank. [Diagram 3] FIG. 2 is a diagram illustrating the detailed cross-sectional structure of an underground tank. [Figure 4] FIG. 2 is a diagram showing the configuration of a detector. [Diagram 5] FIG. 13 is a diagram showing a construction example of attaching a honeycomb board to a steel tank. [Figure 6] A diagram showing the structure near the inspection hatch of an underground tank. [Figure 7] FIG. 4 is a diagram illustrating an example of a detection circuit. [Figure 8] A cross-sectional view showing an example of an underground tank according to a modified example of this embodiment. [Figure 9] FIG. 13 is a diagram showing a modified example of the detection circuit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an example of an underground tank having a double shell structure in which CFRP is used as the steel tank according to this embodiment. The fuel tank 1 is provided with an oil filling pipe 2 for filling, for example, synthetic fuel, hydrogen or oil, a fuel supply pipe 3 for drawing fuel from the fuel tank 1, a vent pipe 4 for ventilating the fuel tank 1, and a level gauge 5 for measuring the liquid level of the fuel stored in the fuel tank 1. The fuel tank 1 is buried at a predetermined depth below the ground surface, and concrete is laid on top of the fuel tank 1.

[0012] An oil filling port 7 is provided on the surface of the fuel filling pipe 2, and fuel is poured in through the oil filling port 7. In addition, equipment 8 such as a measuring device and a pump is provided on the surface of the fuel supply pipe 3, which draws fuel from the fuel tank 1 and measures the amount of fuel to be drawn. In addition, a valve 9 is provided on the oil filling pipe 2, and a valve 10 is provided on the fuel supply pipe 3, and when repairing / refurbishing the fuel tank 1, both valves 9, 10 are closed. In addition, a vent 12 is provided on the vent pipe 4, and gas generated inside the fuel tank 1 is discharged. A signal line 25 is connected to the monitor 18 installed in the office 20, and when a corrosion hole or pitting occurs in the steel tank, this signal line 25 notifies the monitor 18 of this information.

[0013] Fig. 2 is a diagram showing a cross-sectional configuration of the fuel tank 1, and is a DD' cross-sectional view of the fuel tank 1 shown in Fig. 1. As shown in the figure, the fuel tank 1 is made of a steel plate 13, and CFRP 14 is installed on the inside of this steel plate 13. Furthermore, the fuel tank 1 stores oil, synthetic fuel, or hydrogen.

[0014] CFRP14 is formed by applying a novolac vinyl ester resin or the like to a hollow glass fiber reinforcing agent, and forming the resin into a predetermined thickness using a coating roll or the like. Carbon fiber is used as the reinforcing agent, and the reinforcing agent can be in the form of not only a mat but also cloth or nonwoven fabric. In addition to the hand lay-up lamination method described above, a spray-up lamination method in which resin is applied to the reinforcing agent by spraying can also be used as a lamination method for CFRP14.

[0015] FIG. 3 is a diagram showing a more detailed cross-sectional configuration of the fuel tank 1. As shown in the figure, a 3D glass cloth 16 is disposed in the gap between the steel plate 13 and the CFRP 14. The 3D glass cloth 16 is available in various materials such as paper, resin, and metal, but from the viewpoint of strength and liquid leakage detection described later, a resin or metal 3D glass cloth 16 is used. For example, this example is a structure using the 3D glass cloth 16. Moreover, the 3D glass cloth used in this example is arranged to avoid wiring of a leakage detection sensor described later.

[0016] That is, the structure of the fuel tank 1 in this example is a steel tank 13 with 3D glass cloth 16 interposed therebetween and then CFRP 14 attached thereto, and the interposition of the 3D glass cloth 16 forms a predetermined gap between the steel tank 13 and the CFRP 14.

[0017] Meanwhile, a leak detection sensor 17 is disposed at the bottom of the fuel tank 1. This leak detection sensor 17 is disposed over the entire longitudinal length of the fuel tank 1. Fig. 3 also shows an enlarged view of the bottom (part A) of the fuel tank 1. As shown in the figure, the leak detection sensor 17 is disposed in the gap between the steel tank 13 and the CFRP 14, and guides the oil, synthetic fuel, and hydrogen that have accumulated at the bottom of the steel tank 1 to the leak detection sensor, which will be described later. Here, the organic solution is a liquid that is formed when corrosion or pitting occurs in the steel tank 1 due to long-term use, for example, and that is a mixture of underground moisture and organic components such as plants and bacteria contained in the soil leak out through the corrosion or pitting holes.

[0018] Meanwhile, an inspection hatch, which will be described later, is provided at the top of the underground tank 1, and a detection signal detected by a leak detection sensor is sent via a signal line 25 through this inspection hatch to a monitor 18 in the office 20.

[0019] Next, the construction process of the fuel tank 1 having a double shell structure using the above-mentioned CFRP will be described below. First, the inner surface of the steel tank 13 that has been used for many years is cleaned. After this cleaning, the plate thickness and pitting corrosion of the steel tank 13 are measured.

[0020] Next, the leak detection sensor 17 is installed. The leak detection sensor 17 is installed so that any infiltration of oil, synthetic fuel, and hydrogen from corrosion holes or pitting holes that have occurred in the steel tank 13 is guided to a detector via the leak detection sensor, and is installed along the bottom of the steel tank 13. The leak detection sensor 17 is also installed in a straight line along the bottom of the steel tank 13, and is fixed at regular intervals so that it does not become loose.

[0021] Next, the leak detection sensor 22 is attached. This leak detection sensor 22 is installed, for example, in the center of the leak detection sensor 17 arranged along the bottom of the steel tank 13. Figure 4 is a diagram showing the configuration of the leak detection sensor 22. As shown in the figure, the leak detection sensor 22 is composed of fluoropolymer sensors 23a, 23b on both sides and a detection circuit 24 provided between the fluoropolymer sensors 23a, 23b, and the capacitance changes when water, oil, synthetic fuel, or hydrogen comes into contact with either sensor 23a or 23b. The detection circuit 24 detects the presence or absence of a leak and the location of the leak based on this change in capacitance.

[0022] 5 is a diagram showing the state in which the above-mentioned 3D glass cloth 16 is attached after the above-mentioned leak detection sensor 17 and leak detection sensor 22 are arranged. For the sake of explanation, only half of the inner surface of the steel tank 13 is shown. 3D glass cloth 16 of a predetermined size is attached to the inner surface of the steel tank 1 (steel plate 13) at regular intervals. As described above, the 3D glass cloth 16 is attached to the inner surface of the steel tank 1 using resin.

[0023] Next, electrical wiring work is carried out. This work involves connecting a signal line 25 to the leak detection sensor 22 previously installed, and wiring this signal line 25 in the gap between the steel tank 13 and the CFRP 14. Specifically, wiring is carried out to the inspection hatch position using the space where the 3D glass cloth 16 is not installed, and further wiring is carried out to the monitor 18 in the office 20. For example, as shown in Figure 5, wiring is carried out using the space 19 where the 3D glass cloth 16 is not installed.

[0024] Next, a leak detection sensor 17 is disposed inside the 3D glass cloth 16 disposed on the inner surface of the steel tank 13. The CFRP 14 used in this example is, for example, a sheet based on epoxy acrylate resin and reinforced with carbon fiber, and one side is covered with a transparent plastic film. Therefore, this plastic film is peeled off and the CFRP 14 is attached to the 3D glass cloth 16. The CFRP 14 is attached by overlapping the ends so that no gaps are left.

[0025] Next, an airtightness test of the gap (microspace) is performed by attaching an airtightness test tool to the leak detection sensor outlet and injecting a test gas into the gap.

[0026] Figure 6 is a diagram showing the structure near the inspection hatch of the underground tank 1. An iron lid 27 is provided on the top of the inspection hatch 26, and a space for an inspection box 28 is formed inside this lid 27. For example, a CFRP cylinder 29, an inspection hatch 30, and a lower support cylinder member 31 are disposed below the inspection box 28. A handle 32 is provided at the inspection hatch. The signal line 25 is wired to the monitor 18 in the office 20 via this inspection box 28.

[0027] Furthermore, the signal line 25 is protected by a signal cable 33 and is wired to the monitor 18. The monitor 18 is equipped with an LED display unit, a speaker, etc., and when the leak detection sensor 22 detects water, oil, synthetic fuel, or hydrogen, for example, the LED lights up and a pre-recorded warning sound is generated from the speaker. As shown in FIG. 6, in addition to the signal line 25, the signal cable 33 also contains a signal line 11 for transmitting liquid level data detected by the aforementioned liquid level gauge 5, and the liquid level data of the gasoline in the underground tank 1, etc. are also notified to the monitor 18.

[0028] In the underground tank 1 having the above-mentioned configuration, the detection operation for detecting the occurrence of corrosion holes or pitting holes due to corrosion or pitting of the steel tank 13 will be described below. When the steel tank 13 deteriorates after many years of use, corrosion holes and pitting holes appear in the steel plate 13', and oil, synthetic fuel, and hydrogen can penetrate through these holes. However, with the double shell structure of this example, the inner circumferential surface of the steel tank 13 is covered with CFRP 14, so that oil, synthetic fuel, and hydrogen cannot penetrate into the underground tank 1. In addition, the oil, synthetic fuel, and hydrogen in the fuel tank 1 do not leak out to the outside. Therefore, soil contamination due to oil leakage, synthetic fuel, and hydrogen leakage can be prevented.

[0029] On the other hand, oil, synthetic fuel, and hydrogen that have entered through corrosion holes or pitting holes in the steel tank 14 pass through gaps formed between the steel tank 13 and the CFRP 14 and accumulate on the bottom surface of the steel tank 13 .

[0030] Furthermore, oil, synthetic fuel and hydrogen that have accumulated on the bottom surface of the steel tank 13 are guided to the leak detection sensor 22 by the above-mentioned leak detection sensor 17. For example, water or an organic solution that has entered through a hole that has appeared on the left side of the steel tank 13 reaches the left side bottom of the steel tank 13, passes through the leak detection sensor 17 (17a) and reaches the fluoropolymer sensor 23a. The fluoropolymer sensor 23a emits light when it detects oil, synthetic fuel or hydrogen, and the detection circuit 24 detects this light and converts it into a voltage change, thereby detecting a defect in the steel tank 13.

[0031] 7 shows an example of the detection circuit 24, which is composed of transistors Tr1 and Tr2, resistors R1 and R2, and a power supply E. The transistor Tr1 detects the light emitted from the fluoropolymer sensor 23a and outputs a detection signal (output 1) to the signal line 25. This signal is output to the monitor mentioned above, lights up the LED, and also generates a pre-recorded warning sound from the speaker.

[0032] Meanwhile, oil, synthetic fuel, and hydrogen that have entered through the hole that has appeared on the right side of the steel tank 14 reach the bottom right side of the steel tank 13, pass through the leak detection sensor 17 (17b), and reach the fluoropolymer sensor 23b. When the fluoropolymer sensor 23b detects oil, synthetic fuel, or hydrogen, it emits light in the same manner as described above, and the detection circuit 24 detects this light and converts it into a voltage change, thereby detecting liquid leakage from the steel tank 13. In this case, transistor Tr2 detects the light emitted from the fluoropolymer sensor 23b and outputs a detection signal (output 2) to signal line 25. This signal is output to the monitor 18 mentioned above, causing the LED to light up and a pre-recorded warning sound to be emitted from the speaker.

[0033] Therefore, according to this example, the leak detection sensor 22 can detect corrosion holes and pitting holes in the steel tank 13, and can also detect whether a hole that has occurred in the steel tank 13 is on the right or left side of the steel tank 13.

[0034] In the above embodiment, the 3D glass cloth 16 is interposed between the steel tank 13 and the CFRP 14, but as shown in Fig. 8, the CFRP 14 may be attached to the steel tank 13, and a wire mesh member having a mesh structure may be interposed between the CFRP 14 and the CFRP 14. That is, unlike the above-mentioned configuration, the CFRP 14 is first attached to the steel tank 13, and then a wire mesh member 38 is interposed instead of the 3D glass cloth 16, and the CFRP 14 is disposed covering the wire mesh member 38. In this case, since it is difficult to join the wire mesh member 38 to the CFRP 14, for example, a part of the 3D glass cloth 16 is left, and the CFRP 14 is attached to the remaining 3D glass cloth 16.

[0035] With this configuration, a gap may be formed between the CFRP 14 and the CFRP 37, and the above-mentioned leak detection sensor 17 may be disposed in this gap. In this case, the CFRP 37 directly attached to the steel tank 13 has a thickness of, for example, about 2.0 mm, and the wire mesh member 38 is disposed so that a gap of about 2.0 to 2.5 mm is formed between the CFRP 14 and 37.

[0036] In the above embodiment, a fluoropolymer sensor that detects oil, synthetic fuel, and hydrogen was used as the leak detection sensor 22, but the present invention is not limited to the fluoropolymer sensor and can be applied to any sensor that detects oil, synthetic fuel, and hydrogen. For example, terminals P1 and P2 are provided in parallel to resistor R3 of voltage dividing resistors R3 and R4 in the circuit shown in Fig. 9, and terminals P3 and P4 are provided in parallel to resistor R5 of voltage dividing resistors R5 and R6, and terminals P1 and P2 are used in place of the above-mentioned fluoropolymer sensor 23a, and terminals P3 and P4 are used in place of the above-mentioned fluoropolymer sensor 23b. The other circuits shown in Fig. 9 are the same as those in Fig. 7 and are composed of transistors Tr1, Tr2, etc.

[0037] With this configuration, for example, when water or the like penetrates between terminals P1 and P2, the base (B) potential of transistor Tr1 changes and a detection signal is output from output 1, making it possible to notify the occurrence of corrosion holes or pitting holes. Similarly, when water or the like penetrates between terminals P3 and P4, the base (B) potential of transistor Tr2 changes and a detection signal is output from output 2, making it possible to notify the occurrence of corrosion holes or pitting holes. In this case as well, it is possible to detect whether a hole that has occurred in the steel tank 14 is on the right or left side of the steel tank 14.

[0038] In addition, in the above embodiment, corrosion and pitting of the steel tank 14 was described, but for example, even if a hole develops in the CFRP arranged on the inside due to years of use, the leak detection sensor 22 can similarly detect leaks of oil, synthetic fuel, and hydrogen.

[0039] In the above embodiment, an existing fuel tank has been described, and further, CFRP is used for a newly manufactured fuel tank, and the structure in which CFRP is used for the outer shell and inner shell as described above has also been described.

[0040] 1. Underground tank 2...Lubrication pipe 3. Oil supply pipe 4. Ventilation pipe 5...Liquid level gauge 7...Oil filler port 8. Machinery storage room 9, 10 Valves 11 Signal line 12 Ventilation hole 13. Steel tank 13´·steel plate 14·CFRP 16··3D glass cloth 17, 17a, 17b Leak detection sensor 18. Monitor 19. Space 20. Office 21. Fuel supply area 22. Leak detection sensor 23a, 23b Fluoropolymer sensor 24 Detection circuit 25 Signal line 26 Inspection hatch 27...lid 28 Inspection box 29...Cylinder 30 Inspection cover 31...Lower support member 32 Handle 33 Signal cable 37··CFRP 38. Wire mesh member 39. Gap Tr1, Tr2: Transistors R1, R2...resistance R3~R6: Voltage divider resistors P1~P4 terminals E...Power supply

Claims

1. CFRP is installed around the outer and inner periphery of the new steel tank and the inner periphery of the existing steel tank to prevent leakage of oil, synthetic fuel, or hydrogen from the steel tank; A gap forming member disposed between the steel tank and the CFRP; a leak detection sensor disposed between the steel tank and the CFRP to detect corrosion or pitting of the steel tank; An alarm means for notifying a defect in the steel tank based on the detection output of the leak detection sensor; A new and existing buried tank has an inner CFRP double shell structure.

2. The CFRP double-shell inner surface structure for new and existing buried tanks as described in claim 1, characterized in that a leak detection sensor is arranged in the gap formed between the inner surface of the steel tank and the CFRP, and the leak detection sensor is arranged along the side and bottom surfaces of the steel tank to detect leaks of water, oil, synthetic fuel, and hydrogen from corrosion holes or pitting holes in the steel tank, and leaks of oil, synthetic fuel, and hydrogen from holes in the CFRP, and lead the detected leaks to a detector.

3. The inner CFRP double shell structure of new and existing buried tanks as described in claim 1 or 2, characterized in that the gap forming member is composed of 3D glass cloth or a mesh-like wire mesh member, and can detect from which direction oil, synthetic fuel, or hydrogen leaks are occurring.

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