FRP lining application for underground fuel storage tanks, such as mixed gasoline.

Abstract

This invention relates to the construction of FRP lining for underground tanks that store fuels such as mixed gasoline, biomass fuel, and organic solvents. [Solution] A method for repairing a tank using FRP, characterized by performing an opening process to form an opening in a buried tank that stores fuels such as mixed gasoline, biomass fuel, or organic solvents; a cleaning process to enter through the opening and clean the inside of the buried tank; a repair and renovation process to repair and refurbish the inside of the buried tank after the cleaning process; and a process to attach an FRP sheet of a predetermined width to the inside of the buried tank after the repair and renovation process.

Description

Technical Field

[0005]

[0001] The present invention relates to the FRP lining construction of underground tanks for storing fuels such as mixed gasoline, biomass fuel, and organic solvents.

Background Art

[0002] Today, underground tanks for oil storage are widely used at gas stations and the like. Conventionally, such underground tanks for oil storage have stored fuels such as gasoline and light oil, but today, various fuels such as mixed gasoline, biomass fuel, organic solvents such as ethanol, methyl ester, and ketone are used, and it is necessary to store such fuels in underground storage tanks as well.

[0003] For example, mixed gasoline is a fuel used by mixing gasoline and lubricating oil at a certain ratio. Biomass fuel is a renewable fuel made from biological resources of animals and plants such as corn.

[0004] On the other hand, underground storage tanks change over time due to use and may suffer from corrosion and pitting, and problems such as soil pollution may occur if there is fuel leakage or the like. Therefore, repair of the underground storage tank becomes necessary. Patent Document 1 proposes a fuel tank repair method for preventing leakage of combustible fuel from an existing fuel tank without replacing the aged existing fuel tank with a new fuel tank.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, as mentioned above, underground tanks storing various fuels such as modern blended gasoline, biomass fuels, and organic solvents require different repair methods than conventional underground storage tanks. For example, in the case of blended gasoline, as previously stated, it is a fuel made by mixing gasoline and lubricating oil in a certain ratio, making it prone to deterioration and unsuitable for conventional repair methods. In the case of biomass fuel, waste-derived biomass fuel is often used, leading to severe corrosion of the tank's inner surface, which cannot be addressed with conventional repair methods.

[0007] Furthermore, the effectiveness of FRP (fiber-reinforced composite material) lining in buried tanks varies significantly depending on the construction method, as it is crucial to prevent corrosion and pitting. [Means for solving the problem]

[0008] The above problems can be solved by providing an FRP lining construction method for underground fuel storage tanks, according to the present invention, which involves: an opening treatment to form an opening in an underground tank for storing fuels such as mixed gasoline, biomass fuel, or organic solvents; a cleaning treatment to enter through the opening and clean the inside of the underground tank; a repair and renovation treatment to repair and refurbish the inside of the underground tank after the cleaning treatment; a first adhesion treatment to adhere a first FRP sheet of a predetermined width to the inside of the underground tank after the repair and renovation treatment; and a second adhesion treatment to adhere a second FRP sheet on the first FRP sheet.

[0009] Furthermore, the thickness of the first FRP sheet can be achieved by providing a tank repair method using FRP that is thicker than the thickness of the second FRP sheet.

[0010] Furthermore, the attachment of the first FRP sheet can be achieved by providing a tank repair method using FRP, in which the first FRP sheet is attached by overlapping it with an adjacent FRP sheet with a predetermined width, and the second FRP sheet is attached on top of the first FRP sheet such that the center of the second FRP sheet is located in the overlapping portion. [Brief explanation of the drawing]

[0011] [Figure 1] This is a cross-sectional view of the buried tank illustrating this embodiment. [Figure 2] This is a cross-sectional view of the buried tank after the tank opening has been made. [Figure 3] This diagram illustrates the FRP lining application process inside the tank. [Figure 4] This diagram illustrates the FRP lining application process inside the tank. [Figure 5] This figure illustrates another lining construction process of the present invention. [Modes for carrying out the invention]

[0012] Hereinafter, embodiments of the present invention will be described based on the drawings. Figure 1 illustrates the configuration of a buried tank to which the lining method of this embodiment is applied. In the figure, 1 is a buried tank buried underground, and the buried tank 1 can store mixed gasoline, biomass fuel, or organic solvents such as ethanol, methyl ester, or ketone. 2 is a supply pipe that supplies the mixed gasoline, etc., to the buried tank 1, and 3 is a suction pipe used when sucking out the stored mixed gasoline, etc.

[0013] The buried tank 1 is equipped with a vent pipe 4 for venting air from inside the tank, and a metering port (not shown) for measuring mixed gasoline, etc. The buried tank 1 is buried to a predetermined depth from the ground surface, and concrete 5 is installed on top of the buried tank 1. A valve 6 is provided on the supply pipe 2, and a valve 7 is provided on the suction pipe 3, and these valves 6 and 7 are closed when repair / renovation work is carried out on the buried tank 1.

[0014] In the buried tank 1 with the above configuration, the FRP lining construction process inside the tank, including the opening treatment of the buried tank 1, will be explained. First, measure the combustible gas in the buried tank 1. This process checks the internal gas concentration and the presence or absence of fuel leakage using a measuring instrument not shown in the figure. Here, if there are abnormalities in the gas concentration or fuel leakage, etc., they should be removed immediately to make the inside of the buried tank in a safe state.

[0015] Next, when the safety inside the buried tank 1 is confirmed by the above process, perform the extraction operation of the mixed gasoline, or biomass fuel, or organic solvent inside the buried tank 1. This operation involves disconnecting the pipes such as the supply pipe 2 and the suction pipe 3, removing the fuel gauge, inserting the suction hose, and extracting the mixed gasoline, etc. inside the tank using, for example, an air-driven pump or a pressure-resistant explosion-proof pump.

[0016] Next, fill the buried tank 1 with water and spray the oil absorbent. For example, after extracting the mixed gasoline, etc. inside the tank as described above, fill the buried tank 1 with water by introducing water from the supply pipe 2. The amount of this water is about half of the tank capacity, and after filling with water, the water should reach near the middle of the buried tank 1. After the above water filling, spray the organic oil absorbent to absorb the floating oil on the organic oil absorbent. The water from which the oil has been separated is discharged into the drainage ditch through an oil-water separation tank not shown in the figure.

[0017] Next, perform a water pressure test on the buried tank 1 and each of the pipes 2 and 3. This test is carried out after the removal of the floating oil. Fill the inside of the buried tank 1 with water, for example, increase the pressure to 0.7 Kg / m of water pressure, and perform a water pressure test on the buried tank 1, the supply pipe 2, and the suction pipe 3 to check for the presence or absence of water leakage.

[0018] Next, cut off the edges of the buried tank 1 and each of the pipes 2 and 3. That is, cut off the edges of all the pipes connected to the buried tank 1.

[0019] Next, mark the position of the opening to be formed on the buried tank 1 and install a temporary enclosure. The position of the opening to be formed on the buried tank 1 is determined according to the structural diagram of the buried tank 1. Also, after marking the position of the opening, cover the surrounding area with a temporary fireproof wall.

[0020] Next, remove the concrete 5 formed on the buried tank 1 and perform excavation work. Here, the position of the concrete 5 is particularly indicated as 5' in FIG. 1. This process is to cut the concrete 5' with a concrete excavator along the lined line, and after cutting, crush the concrete 5' with a concrete breaker and dig down the earth and sand 8 until the buried tank 1 appears.

[0021] Next, remove the anticorrosion coating. That is, remove the anticorrosion coating applied to the tank according to the opening of the buried tank 1.

[0022] Next, perform the opening work of the buried tank 1. This opening is carried out with an air cutter, and after the opening work is completed, perform the removal work of the water seal bath. FIG. 2 is a diagram showing the state of the buried tank 1 and its vicinity after the above series of operations. Note that 9 shown in the figure is the opening.

[0023] When the opening work is completed as described above, perform the cleaning work of the tank. The cleaning work of the tank is to pump out the water in the buried tank 1 with an air-driven pump or a pressure-resistant explosion-proof pump and discharge it through an oil-water separation tank. Then, after draining the water, spray an organic oil absorbent on the sludge inside the buried tank 1, and further add, for example, a 6% emulsion solution to its surface to extremely suppress the generation of volatile gases, and dispose of it together with the cleaning sewage inside the buried tank 1.

[0024] When the cleaning work inside the buried tank 1 is completed as described above, inspect the inside of the buried tank 1. First, visually inspect the inside of the buried tank 1. This visual inspection is carried out over the entire inside of the buried tank 1 while performing buffing with sandblasting or a wire brush to expose the base metal of the tank body.

[0025] Next, a visual inspection is conducted throughout the entire interior of the buried tank 1 to check for corrosion, scratches, tool marks, etc., including their location and quantity. Here, puncture damage is measured to check the depth, location, and quantity of puncture damage found through visual inspection, etc. In addition, plate thickness is measured using an ultrasonic thickness gauge to measure the thickness of the entire interior, including the shell and end plates.

[0026] Penetrant testing is performed on weld lines throughout the tank interior, nozzle neck welds, and damaged areas such as cracks detected by visual inspection. Next, the tank will undergo repair and renovation work. If, as a result of the inspection and examination of the inside of the tank, any repairs are deemed necessary, a specific renovation plan will be formulated according to the situation, based on a comprehensive assessment including the selection of repair materials, renovation methods, and maintenance measures, as well as the construction period. Specifically, a renovation plan will be formulated and implemented using plate welding, build-up welding, corrosion-resistant coating, or other effective methods.

[0027] Next, the FRP lining inside the tank is applied. This lining process begins with preparing the surface by sandblasting or using a wire brush, followed by applying a primer coat. After the primer coat, a predetermined number of FRP prepreg sheets are laminated and cured by exposure to ultraviolet light.

[0028] Figures 3 and 4 are diagrams that specifically illustrate the lining construction process inside the tank, and are cross-sectional views of the buried tank 1. The buried tank 1 is made of steel plate and has undergone the prescribed repairs as described above. An FRP prepreg sheet is attached to the inside of this buried tank 1. Here, FRP (fiber-reinforced composite material) is a composite material in which high-strength fibers are reinforced with materials such as plastic, metal, or rubber, and glass fiber composite material or carbon fiber composite material can be used.

[0029] The following describes the specific method for applying the FRP. First, as described above, after applying a primer to the base, the prepreg sheet 11 is applied starting from a predetermined position on the inner surface of the buried tank 1. That is, as shown in Figure 3, starting from position 10a inside the buried tank 1, which shows the cross-sectional shape, the FRP (prepreg sheet) 11 is applied along the inside of the tank 1 in a counterclockwise direction at a 240° angle, until it reaches position 10b.

[0030] Furthermore, adhesive is pre-applied to the FRP (prepreg sheet) 11. The FRP (plastic sheet) 11 is peeled off and used, and when attaching it to the inner surface of the buried tank 1, care is taken to ensure that no gas phase is created between the inner surface of the buried tank 10 and the FRP (prepreg sheet) 11. The above-described attachment work of the FRP (prepreg sheet) 11 is carried out sequentially from one end to the other in the longitudinal direction of the buried tank 1. In this way, the FRP (prepreg sheet) 11 is attached to the middle and lower layers of the buried tank 1 over a 240° range.

[0031] In this way, once the attachment of FRP (prepreg sheet) 11 to the middle and lower layers of the buried tank 1 is complete, the attachment process for the upper layer of the buried tank 1 is then carried out. Figure 4 is a diagram illustrating the attachment process for the upper layer of the buried tank 1. As shown in the figure, the FRP (prepreg sheet) 11 has been attached to all but the area between positions 10a and 10b by the process described above. Therefore, in order to attach the FRP (prepreg sheet) 11 to this area, the starting position for attaching the FRP (prepreg sheet) 11 is set to 10b, and the FRP (prepreg sheet) 11 is attached up to the ending position 10a.

[0032] In other words, the FRP (prepreg sheet) 11 is attached in a counterclockwise direction, and the FRP (prepreg sheet) 11 is attached to a 120° range in the upper layer of the buried tank 1.

[0033] By performing the bonding process as described above, the entire inner surface of the buried tank 1 is covered with FRP (prepreg sheet) 11. Finally, the FRP (prepreg sheet) 11 is irradiated with ultraviolet light to harden it.

[0034] After that, work such as installing the manhole will be carried out, and once the inspection port is installed, all openings of buried tank 1 will be sealed, followed by an airtightness test and then the restoration work will be carried out. As described above, according to this embodiment, the inside of the buried tank 1 is entered through the opening 9, and the FRP lining treatment shown in Figures 3 and 4 is performed to repair and refurbish the buried tank 1, thereby ensuring that corrosion, pitting, oil leaks, etc. of the buried tank are reliably repaired.

[0035] Furthermore, although buried tank 1 will deteriorate over time after repair and renovation according to this example, the progression of this deterioration will be slowed down by the application of FRP, making it possible to use buried tank 1 for a long period of time.

[0036] In this example, FRP11 was applied to the middle and lower layers at a 240° angle, but it is not necessarily required to apply it at a 240° angle. Furthermore, the upper layer may also be applied to the remaining area.

[0037] Furthermore, although the above description of the embodiment described the lining construction using FRP, it is also possible to form a layer of FRP inside the buried tank by applying FRP to the inner wall of the tank using a brush or the like, or by spraying FRP onto the inner wall of the tank.

[0038] Here, the process of applying FRP to the inner wall of the tank using a brush or the like is, for example, a process in which a worker uses a roll brush or a brush to apply FRP to the inner wall of the tank. Also, the process of spraying FRP onto the inner wall of the tank is, for example, a process in which a worker uses a gun spray pressurized by a compressor to spray the flowable FRP onto the inner wall of the tank.

[0039] By processing the tank in this way, a layer of FRP can be formed on the inner wall of the buried tank 1, ensuring that the buried tank can be reliably repaired and refurbished.

[0040] Next, other embodiments of the present invention will be described. Figure 5 is a diagram specifically illustrating the lining construction process of another embodiment, and is a cross-sectional view of the buried tank 20. The buried tank 20 is made of steel plate and has undergone the prescribed repairs as described above. An FRP prepreg sheet is attached to the inside of this buried tank 20.

[0041] Here, FRP (fiber-reinforced composite material) is a composite material in which high-strength fibers are reinforced with materials such as plastic, metal, or rubber, and glass fiber reinforced plastics (GFRP) and carbon fiber composite materials can be used.

[0042] The following describes the specific method for applying the FRP. First, after applying a primer coat to the base as described above, the FRP sheet 21 is applied starting from a predetermined position on the inner surface of the buried tank 20. That is, as shown in Figure 5, the FRP sheet 21 is applied along the inside of the tank 20, starting from position 30 inside the buried tank 20.

[0043] Here, the FRP sheet 21 has a predetermined length, for example, a sheet with a thickness of 1.3 mm and a width of 50 cm is used. Also, adhesive is pre-applied to the FRP sheet 11, and it is used after peeling off the protective film.

[0044] First, starting from position 30 inside the buried tank 20, for example, FRP sheet 21-1 is attached. At this time, it is attached in a way that prevents a gas phase from forming between the inner surface of the buried tank 20 and the FRP sheet 21-1. Next, starting from position 21-1'', for example 5 cm inward from the end 21-1' of FRP sheet 21-1, the next FRP sheet 21-2 is attached so that it partially overlaps FRP sheet 21-1. That is, the next FRP sheet 21-2 is attached overlapping FRP sheet 21-2 by 5 cm inward from the end 21-1' of FRP sheet 21-1.

[0045] Next, as described above, starting from a point 21-2'' 5cm inward from the edge 21-2′ of FRP sheet 21-2, FRP sheet 21-3 is applied so that it partially overlaps FRP sheet 21-2. That is, the next FRP sheet 11-3 is applied overlapping by 5cm inward from the edge 21-2′ of FRP sheet 21-2.

[0046] Similarly, 1.3 mm thick FRP sheets are sequentially attached in a counterclockwise direction until the initial position 30 is reached, at which point FRP sheets 21-1 to 21-n are attached around the inside of the buried tank 20.

[0047] Next, a second FRP sheet 22 with a thickness of 0.8 mm is attached to the above FRP sheets 21-1 to 21-n. This second FRP sheet 22 is also 50 cm wide, like the first FRP sheet 21, and has adhesive applied to it beforehand.

[0048] Here, the FRP sheet 22 is attached as follows: FRP sheet 22-1 is attached so as to cover from the center 21-1c of FRP sheet 21-1 to the center 21-2c of the adjacent FRP sheet 21-2. Therefore, FRP sheet 22-1 is attached so that its center is the overlapping portion of FRP sheets 21-1 and 21-2. In this case as well, the sheets are attached in such a way that no gas phase is created between FRP sheet 22-1 and FRP sheets 21-1 and 21-2.

[0049] Next, FRP sheet 22-2 is attached, covering the area from the center 21-2c of FRP sheet 21-2 to the center 21-3c of the adjacent FRP sheet 21-3. Therefore, in this case as well, FRP sheet 22-2 is attached so that its center is the overlapping portion of FRP sheets 21-2 and 21-3.

[0050] Similarly, 0.8 mm thick FRP sheets 22-3, 22-4, ... 22-n are sequentially attached to FRP sheets 21-3, 21-4, ... 21-n. When the initial position 30 is reached, FRP sheets 22-1 to 22-n are attached in a circular fashion around the inside of the buried tank 20, overlapping and being attached to FRP sheets 21-1 to 21-n.

[0051] In this way, by covering the FRP sheets 21-1 to 21-n attached to the inner surface of the buried tank 20 with FRP sheets 22-1 to 22-n in a double layer, the buried tank 20 can be reliably protected from corrosion and pitting. In particular, in this example of a tank repair method using FRP, the center of the FRP sheets 22-1 to 22-n is positioned at the overlapping portion of the FRP sheets 21-1 to 21-n, thus proposing a tank repair method using FRP that can more effectively prevent fuel leakage.

[0052] By performing the bonding process as described above, the inner surface of the buried tank 20 is completely covered with two layers of FRP sheets 21 and 22. Finally, the FRP sheets 21 and 22 are cured by irradiating them with an ultraviolet fluorescent lamp.

[0053] After that, work such as installing manholes will be carried out, and once the inspection hatches are installed, all openings of the buried tank 20 will be sealed, followed by an airtightness test, and then further restoration work will be performed.

[0054] As described above, according to this embodiment, a more reliable FRP lining can be constructed, and corrosion, pitting, fuel leakage, etc. of the buried tank 20 can be reliably prevented. In this example, the configuration is described as first attaching 1.3 mm thick FRP sheets 21-1 to 21-n, and then attaching 0.8 mm thick FRP sheets 22-1 to 22-n on top of them. However, the configuration may also be reversed, with 0.8 mm thick FRP sheets 21-1 to 21-n being attached first, and then 1.3 mm thick FRP sheets 22-1 to 22-n being attached on top of them. [Explanation of Symbols]

[0055] 1. Buried tank 2. Fuel supply pipe 3...Suction tube 4. Ventilation pipes 5, 5'... Concrete 6, 7... valves 10...Start position 11, 11-1~11-n··FRP sheet 11-1′~11-n′··End part 11-1″~11-n″·Position 11-1c~11-nc...center position 12, 12-1~12-n··FRP sheet 20. Buried tanks 21, 21-1, 21-2, ...FRP sheet 22, 22-1, 22-2, ...FRP sheet 21-1′, 21-2′...end 30...position

Claims

1. An opening treatment is performed to create an opening in an underground tank for storing fuels such as mixed gasoline, biomass fuel, and organic solvents. A cleaning process is performed by entering through the opening and cleaning the inside of the buried tank, The repair and renovation process involves repairing and refurbishing the inside of the buried tank after the cleaning process, The process involves attaching a first FRP sheet of a predetermined width to the inside of the buried tank after the repair and renovation treatment, The process involves attaching a second FRP sheet onto the first FRP sheet, A method for repairing a tank using FRP, characterized by performing the following.

2. The method for repairing a tank using FRP according to claim 1, characterized in that the thickness of the first FRP sheet is greater than the thickness of the second FRP sheet.

3. The method for repairing a tank using FRP according to claim 1 or 2, characterized in that the first FRP sheet is attached by overlapping it with an adjacent FRP sheet with a predetermined width, and the second FRP sheet is attached on top of the first FRP sheet such that the center of the second FRP sheet is located at the overlapping portion.

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