Method for inspecting structure

Abstract

To provide an improved method for inspecting structures.SOLUTION: A surface of a part to be inspected of a structure is covered with a manually peelable coating, and a surrounding surface of the part to be inspected and the manually peelable coating are firmly bonded to each other via a primer, i.e., the part to be inspected is covered with the manually peelable coating and firmly bonded to the surroundings, and then the manually peelable coating of the part to be inspected is cut off and peeled off to inspect the part to be inspected. One example of a method for inspecting a liquid-storage steel structure includes the steps of: peeling off the coating of the part to be inspected of a liquid-storage steel structure, the entire surface of which is coated with an anti-rust coating, by blasting to form a strip-shaped coating-peeled part; attaching masking tape to an existing coating surface on the outer periphery of the coating-peeled part; applying a primer to the existing coating on the outer periphery; applying a paint that produces a solvent-resistant and manually peelable coating; picking up the coating and the masking tape with left and right ends of the coating and the masking tape as ears; and inspecting the steel plate of the part to be inspected by using the coating and the masking tape.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a method for inspecting structures such as liquid storage tanks. [Background technology]

[0002] Tanks or equipment that store or handle hydrocarbon oils such as petroleum, or tanks or equipment that store high-pressure gas such as liquefied petroleum gas (LPG), which are steel structures, are required by the Fire Service Act and the High Pressure Gas Safety Act to be opened within a certain period of time and to undergo inspections of welds and plate thickness. Weld inspection involves magnetic particle testing to determine whether or not there are cracks, scratches, or false patterns in the welds. However, because the magnetic particle patterns cannot be seen through the anti-rust coating on the surface near the welds, the anti-rust coating on the surface near the welds must be removed before the inspection can be carried out. For this reason, anti-rust coatings are removed using a blasting method in which silica sand, grit, etc. is projected at high speed onto the coating surface to crush the coating and remove it. However, although this blasting method completely removes the coating, it causes many problems. (1) Since dust is generated, work will be carried out while wearing dust masks, but this will inevitably have an impact on the occupational hygiene environment and the surrounding environment. (2) Blasting work removes the paint film and grinds away the throat thickness of welds and the surface of the edges by several tens of microns. For this reason, when blowholes or cracks present immediately below the surface of the weld are exposed on the surface of the steel sheet, polishing is required to remove the cracks and the like from the surface of the steel sheet. As a result, the throat thickness of the weld is reduced at an accelerating rate due to the reduction in thickness caused by blasting and grinding with the grinder. If the polishing results in the plate thickness being less than the legally required minimum thickness, a welded repair will be performed, which will result in residual stress being generated around the repaired area. As a result, the inspections that were originally intended to ensure safety have turned into a vicious cycle of inspections that thin the throat thickness of the welds with each overhaul, raising concerns about leaks of stored oil due to earthquake loads. (3) Blasting causes numerous scratches on the surface of steel plates that passed the previous weld inspection, causing the magnetic powder pattern from the previous weld inspection to change. As a result, the surface of the steel plate becomes rough every time it is opened, and inspections are being repeated from scratch without being able to compare results with those of previous inspections. (4) Blasting work takes about one month for crude oil tanks. Therefore, by the time the next step, inspection work, begins, rust has already started to form in the areas where the paint has peeled off. In addition, the impact frictional heat of the blasting causes metal to fall and adhere to the steel plate surface. For this reason, pre-inspection preparation work involves using a grinder to remove rust and metal, which means non-destructive inspections cannot be carried out quickly. Blasting work is necessary to remove the paint film, but it comes at a high cost in terms of the poor occupational health and environment, the environmental pollution it causes around the factory, and the reduction in throat thickness of welds every time an overhaul inspection is conducted. Blasting has been considered unavoidable in removing paint films, but when considered at an industry-wide level, blast removal results in significant waste for the national economy, including operational losses in international competitiveness, high costs, and environmental burdens due to the disposal of industrial waste in soil. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-169307 A Summary of the Invention [Problem to be solved by the invention]

[0004] Therefore, there has been a demand for a non-destructive inspection method, particularly a magnetic particle inspection method, that can solve the above-mentioned problems of dust, reduce damage caused by blasting work on structures such as oil tanks, and enable rapid inspection. [Means for solving the problem]

[0005] Therefore, as a result of extensive research, the inventors have developed a method for inspecting structures, which not only solves many of the problems mentioned above but also significantly improves the entire process of open inspection work by using a coating film that can be peeled off manually, thereby enabling damage to structures such as oil storage tanks to be easily inspected and repaired at low cost. Therefore, as a result of extensive research, the inventors have developed a method for inspecting structures that uses a manually peelable coating, which not only solves many of the problems mentioned above, but also significantly improves the entire process of open inspection work, allowing for easy inspection and repair. That is, the present invention provides a method for inspecting a structure having the following configuration. [1] A method for inspecting a structure, comprising: covering the surface of a portion of the structure to be inspected with a manually peelable coating; and firmly adhering the surrounding surface of the portion to be inspected to the manually peelable coating via a primer; i.e., encapsulating the portion to be inspected with the manually peelable coating, and then cutting out and peeling off the manually peelable coating of the portion to be inspected. [2] A method for inspecting a structure, comprising: covering the surface of a part of the structure to be inspected with a transparent, manually peelable coating; and firmly adhering the surrounding surface of the part to be inspected to the transparent, manually peelable coating via a primer; i.e., encapsulating the part to be inspected with a transparent, manually peelable coating that is firmly adhered to the surrounding area; and then visually inspecting the part to be inspected by looking through the transparent, manually peelable coating.

[0006] [3] A method for inspecting a structure, comprising: encapsulating the surface of a portion of the structure to be inspected with a transparent, manually peelable coating; and firmly adhering the surrounding surface of the portion to be inspected to the transparent, manually peelable coating via a primer; i.e., encapsulating the portion to be inspected with the transparent, manually peelable coating that is firmly adhered to the surrounding surface; and then cutting out and peeling off the manually peelable coating of the portion to be inspected. [4] 1. A first step of peeling off the coating film of the inspection-required portion (2') of a liquid storage steel structure (1) having an anti-rust coating film (2) applied to the entire surface thereof by blasting to form a strip-shaped coating-peeled portion (3); 2. A second step of attaching a masking tape (4) to the surface of the existing coating film (2) on the outer periphery of the strip-shaped coating film peeled portion (3) formed in the first step; 3. A third step of applying a primer (5) to the existing coating film (2) on the outer periphery of the masking tape (4) in order to firmly adhere a solvent-resistant and manually peelable coating film (6); 4. A fourth step of applying a paint that forms a solvent-resistant, manually peelable coating film (6) to the entire surface of the coating film peeling portion (3), the masking tape (4), and the primer (5) on the outer periphery of the masking tape; 5. A fifth step of making an incision with a utility knife (7) in the solvent-resistant, manually peelable coating film (6) located at the boundary between the masking tape (4) and the primer (5), picking up the left and right ends of the coating film (6) and the masking tape (4) with the fingers, lifting the coating film (6) and the masking tape (4) from the steel plate (the strip-shaped coating film peeling portion (3)) of the inspection target portion (2'), and pulling them upward to peel them off; 6. A method for inspecting a liquid storage steel structure, comprising a sixth step of inspecting the steel plate of the inspection-required portion (2') (the steel plate of the strip-shaped coating peeled portion (3)) exposed by peeling off the manually peelable coating film (6).

[0007] [5] 1. A first step of attaching masking tape (4) to the outer periphery of a steel plate of a steel plate of a part (2') to be inspected of a liquid storage steel structure (1) having no anti-corrosive coating on the entire surface; 2. A second step of applying a primer (5) to the steel plate around the outer periphery of the masking tape (4) for firmly adhering a solvent-resistant, manually peelable coating film (6); 3. A third step of applying a paint that produces a solvent-resistant, manually peelable coating film (6) to the entire surface of the steel plate of the inspection-required portion (2'), the masking tape (4), and the primer (5) on the steel plate around the outer periphery of the masking tape (4); 4. A fourth step of making an incision with a cutter knife (7) in the solvent-resistant and manually peelable coating film (6) located at the boundary between the masking tape (4) and the primer (5), picking up the left and right ends of the coating film (6) and the masking tape (4) with fingers, lifting the coating film (6) and the masking tape (4) from the steel plate of the inspection-required portion (2'), pulling them upward, and peeling them off; 5. A method for inspecting a liquid storage steel structure, comprising a fifth step of inspecting the steel plate of the inspection-required portion (2') from which the coating film (6) has been peeled off and exposed. [6] 1. A first step of peeling off the coating film of a part (2') to be inspected of a liquid storage steel structure (1) having an anti-rust coating film (2) applied to the entire surface thereof by blasting to form a strip-shaped coating-peeled part (3); 2. A second step of attaching a masking tape (4) to the strip-shaped coating film peeled portion (3) formed in the first step; 3. A third step of applying a primer (5) to the existing coating film (2) on the outer periphery of the strip-shaped coating film peeling portion (3) in order to firmly adhere a solvent-resistant, manually peelable coating film; 4. A fourth step of applying a paint that forms a solvent-resistant and manually peelable coating film (6) to the entire surface of the masking tape (4) on the surface of the coating film peeling portion (3) and the primer (5) on the outer periphery of the masking tape; 5. A fifth step of making an incision with a utility knife (7) in the solvent-resistant, manually peelable coating film (6) located on the left and right edges of the masking tape (4), picking up the left and right edges of the coating film (6) and the masking tape (4) with the fingers, lifting the coating film (6) and the masking tape (4) from the steel plate (1) in the area to be inspected (the strip-shaped coating peeling portion (3)), and pulling them upward to peel off the masking tape (4) from the steel plate (1); 6. A method for inspecting a liquid-storage steel structure, comprising: a sixth step of inspecting the steel plate (1) (the strip-shaped paint peeling portion (3)) of the inspection-required portion (2') exposed by peeling off the masking tape (4).

[0008] [7] 1. A first step of peeling off the rust-preventive coating film from the inspection-required portion (2') of a liquid storage steel structure (1) having an anti-rust coating film applied to the entire surface thereof by blasting to form a strip-shaped coating-removed portion (3); 2. A second step of attaching a masking tape (4) to the surface of the existing coating film (2) on the outer periphery of the strip-shaped coating film peeled portion (3) formed in the first step; 3. A third step of applying a primer (5) to the existing coating film (2) on the outer periphery of the masking tape (4) in order to firmly adhere a manually peelable coating film (6); 4. A fourth step of applying a paint to the surface of the coating film peeling portion (3), the masking tape (4) and the entire surface of the primer (5) to form a transparent coating film (6') that can be peeled off manually; 5. A method for inspecting a liquid storage steel structure, comprising: a fifth step of visually inspecting the area to be inspected through said transparent, manually peelable coating film (6'). [8] 1. A first step of attaching masking tape (4) to a steel plate of a part (2') to be inspected of a liquid storage steel structure (1) having no anti-corrosive coating on the entire surface; 2. A second step of applying a primer (5) to the outer periphery of the steel plate of the inspection-required portion (2') in order to firmly adhere a solvent-resistant, manually peelable coating film (6); 3. A third step of applying a paint that produces a solvent-resistant and manually peelable coating film (6) to the entire surface of the masking tape (4) of the steel plate of the inspection-required portion (2') and the primer (5) of the steel plate on the outer periphery of the inspection-required portion (2'); 4. A fourth step of making an incision with a cutter knife (7) in the solvent-resistant and manually peelable coating film (6) located on the left and right edges of the masking tape (4), picking up the left and right edges of the coating film (6) and the masking tape (4) with fingers, lifting the coating film (6) and the masking tape (4) off the steel plate of the inspection-required portion (2'), pulling them upward, and peeling the masking tape (4) off the steel plate of the inspection-required portion; 5. A method for inspecting a liquid storage steel structure, comprising a sixth step of inspecting the steel plate of the inspection-required portion (2') exposed by peeling off the masking tape (4).

[0009] [9] 1. A first step of peeling off the surface of a rainwater infiltration prevention measure of a liquid storage structure by blasting to form a rainwater infiltration prevention measure peeled off portion; 2. A second step of applying a primer (5) to the lower part of the side panel (10) of the liquid storage structure, the front edge of the bottom panel overhang (11), and the outer periphery of the berm (13) to firmly adhere a transparent, manually peelable coating film (6'); 3. A third step of applying a paint to the entire primer surface of the rainwater intrusion prevention measure peeling portion and the entire surface between all the primers to form a manually peelable transparent coating film (6'); 4. A method for inspecting a liquid storage structure, comprising a fourth step of visually inspecting the peeled-off portion of the rainwater intrusion prevention measure seen through a transparent coating film (6').

[0010]

[10] 1. A first step of peeling off the surface of a rainwater infiltration prevention measure of a liquid storage structure by blasting to form a rainwater infiltration prevention measure peeled off portion; 2. A second step of applying a primer (5) to the front edge of the bottom plate overhang (11) of the liquid storage structure and the outer periphery of the berm (13) for firmly adhering a transparent, manually peelable coating film (6'); 3. A third step of attaching a transparent masking tape (4') to the berm (13) of the rainwater intrusion prevention measure peeling portion formed in the first step; 4. A fourth step of applying a paint to the entire primer surface of the rainwater intrusion prevention measure peeling portion and the entire surface between all the primers to form a manually peelable transparent coating film (6'); 5. A method for inspecting a liquid storage structure, comprising a fifth step of visually inspecting the peeled-off portion of the rainwater intrusion prevention measure, which can be seen through a transparent coating film (6') and a transparent masking tape (4').

[11] 1. A first step of applying a primer (5) to the outer periphery of a substrate of a structure (1) at a visual inspection site (2') for safety reasons in order to firmly adhere a transparent, manually peelable coating film (6'); 2. A second step of applying a paint to the entire surface of the substrate and primer (5) of the required visual inspection area (2') to form a transparent, manually peelable coating film (6'); 3. A method for inspecting a structure, comprising a third step of visually inspecting the substrate of the required visual inspection area (2') seen through a transparent coating film (6').

[12] 1. A first step of attaching a transparent masking tape (4') to a substrate of a portion (2') of a structure (1) that is to be visually inspected for safety reasons; 2. A second step of applying a primer (5) to the outer periphery of the substrate in the required visual inspection area (2') for firmly adhering a transparent, manually peelable coating film (6'); 3. A third step of applying a paint to the entire surface of the masking tape (4') and the primer (5) to form a transparent, manually peelable coating film (6'); 4. A method for inspecting a structure, comprising a third step of visually inspecting the substrate of the required visual inspection area (2') seen through a transparent coating film (6').

[0011]

[13] The method for inspecting a structure according to any one of [1] to

[12] above, characterized in that the paint producing the manually peelable coating film (6, 6') is mainly composed of a polyurea monopolymer.

[14] The method for inspecting a structure according to any one of the above [1] to

[12] , characterized in that the paint producing the manually peelable coating film (6, 6') is mainly composed of a copolymer of polyurea and polyurethane.

[15] A coating material which produces a manually peelable coating film (6) is mainly composed of a polyurea monopolymer or a copolymer of polyurea and polyurethane, The powder or flakes are selected from silica, mica, and glass having an average particle size of 10 to 500 μm. The content of the fine powder or flakes is 5 to 35% based on the solid content mass of the solvent-resistant, manually peelable coating film (6); The tensile strength (JIS A6021:2011) of the coating film (dry film thickness 700 μm) obtained by applying the paint (6) is 2.3 to 40 N / mm 2 and The elongation at break (JIS A6021:2011) of the coating film (dry film thickness 700 μm) is 11 to 500%, The adhesion strength of the coating is 10-100kg / cm 2 A method for inspecting a structure according to any one of claims [1], [4], [5], [6] or [8], characterized in that

[16] A method for inspecting a structure described in any one of [1] to

[15] , characterized in that the structure (1) is a tank for storing or handling a hydrocarbon oil such as petroleum, or a tank for storing or handling a liquefied gas such as LPG. Effect of the Invention

[0012] According to the present invention, the portion requiring inspection is normally protected by a manually peelable coating film, and at the time of inspection, the manually peelable coating film can be easily peeled off, allowing the portion requiring inspection to be inspected immediately. In addition, when a transparent, manually peelable coating is used, the parts requiring inspection are protected by the manually peelable coating at all times, while the transparent coating can be seen through to monitor and inspect the parts. If an abnormality is found in the parts requiring inspection, the transparent coating can be easily peeled off to immediately check and repair the problem. In particular, a manually peelable coating film mainly composed of a polyurea monopolymer or a copolymer of polyurea and polyurethane, which is said to have strength comparable to that of concrete and extremely excellent flexibility, is used to completely encapsulate the area to be inspected, thereby achieving the following excellent effects: (1) In the case of crude oil tanks, non-destructive testing can be performed while peeling off the manually removable coating film by hand, without having to wait for the first blasting work period, which can last up to one month. In addition, since the coating film is peeled off manually, dust caused by blasting is not generated, so coating film peeling and non-destructive testing can be carried out simultaneously. As a result, the tank open period is shortened by one month. Conventionally, the coating on the weld line had to be completely removed before moving on to the next step of non-destructive testing, but the present invention eliminates the need for heavy machinery such as power supply vehicles and compressors that are required for blasting work, which also results in cost reduction. (2) Since the coating can be peeled off in accordance with the progress of the non-destructive testing, there is no need to peel off the coating for sections that are not scheduled for testing. This makes it possible to protect the steel plate surface from moisture in the air and rainwater for several months until the safety inspection, thereby suppressing the occurrence of red rust and the progression of rust. (3) During non-destructive testing, there is no need for buffing to remove rust or chipping (removal) of deposited metal that occurs during blasting work, thereby improving inspection speed. For inspection companies, this brings about a major benefit as non-destructive testing, or 3K work, is improved, changing the image of the profession. (4) After the non-destructive testing is completed, the peeled off coating can be used to temporarily cover the peeled off areas for a certain period of time, thereby insulating the steel plate surface from moisture in the air and rainwater for several months to a year until the government inspection. As a result, for example, a second blasting operation immediately before a government inspection will no longer be necessary, and the tank open period will be shortened by a further two weeks.

[0013] (5) By using transparent or translucent solvent-resistant paint with manual peeling off for the prevention of rainwater intrusion around the exterior of tank basins and for the prevention of oil intrusion into the pontoons of floating roof tanks, it becomes possible to detect oil seepage and leakage early through daily inspections and visual inspections without having to take the trouble of peeling off the coating. (6) Because blasting creates sparks, the work to remove the rainwater intrusion prevention measures is carried out at the same time as the blasting work for the coating on the tank bottom plate. This means that the entire circumference of the bottom plate overhang is exposed to rain for the entire period the tank is open (several months to a maximum of just under a year), allowing rainwater to infiltrate the underside of the tank bottom plate. However, if manual coating removal becomes possible, the coating can be removed at the time of inspection by government agencies without having to remove it at the time the tank is opened. In addition, by touching up the peeled coating after the inspection, immediate repair and restoration can be made possible, and unnecessary exposure to rain can be avoided in advance. (7) If the coating of the rainwater infiltration prevention measures has not deteriorated, the rainwater infiltration prevention measures can be reused and used repeatedly until the next open inspection. As a result, from an environmental perspective, it is possible to reduce the amount of industrial waste discharged from the factory.

[0014] (8) By using the paint of the present invention, which has a large elongation rate and shape conformability, it becomes easy to provide weatherproofing to prevent corrosion. In particular, at the connection between the equipment and the heating pipes, which have different vibrations during operation and natural periods and thermal expansion coefficients, using the shape-conforming coating film of the present invention for rainproofing helps prevent corrosion of the outer surface of the pipes (corrosion under the insulation). (9) It helps prevent deterioration of the rainwater infiltration prevention measures installed on the tank bottom plate overhang, which expands and contracts due to fluctuations in the liquid level in the tank and the temperature gradient in the heated tank. (10) The floating roof tank roof and the pontoons of the auxiliary equipment are constantly subjected to repeated fatigue caused by waves, and fatigue cracks are inevitable due to the accumulation of residual stress. However, in the unlikely event that a crack or corrosion penetrates the steel plate, the coating will seal the opening, preventing leakage or outflow. [Brief description of the drawings]

[0015] [Figure 1] An explanatory diagram showing the method of claim 4 of the present invention. [Diagram 2] An explanatory diagram showing the method of claim 4 of the present invention. [Diagram 3] An explanatory diagram showing the method of claim 4 of the present invention. [Figure 4] An explanatory diagram showing the method of claim 4 of the present invention. [Diagram 5] An explanatory diagram showing the method of claim 4 of the present invention. [Figure 6] An explanatory diagram showing the method of claim 4 of the present invention. [Figure 7] An explanatory diagram showing the method of claim 6 of the present invention. [Figure 8] An explanatory diagram showing the method of claim 6 of the present invention. [Figure 9] An explanatory diagram showing the method of claim 6 of the present invention. [Figure 10] An explanatory diagram showing the method of claim 6 of the present invention. [Figure 11] An explanatory diagram showing the method of claim 6 of the present invention. [Figure 12] An explanatory diagram showing the method of claim 6 of the present invention. [Figure 13] An explanatory diagram showing the method of claim 7 of the present invention. [Figure 14] An explanatory diagram showing the method of claim 7 of the present invention. [Figure 15] An explanatory diagram showing the method of claim 7 of the present invention. [Figure 16] An explanatory diagram showing the method of claim 7 of the present invention. [Figure 17] An explanatory diagram showing the method of claim 9 of the present invention. [Figure 18] An explanatory diagram showing the method of claim 10 of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described. First, the basic technical idea of ​​the present invention is to cover the surface of a part requiring inspection of a structure such as an oil tank with a manually peelable coating, and to firmly bond the surrounding surface of the part requiring inspection to the manually peelable coating via a primer, and then to peel off the manually peelable coating of the part requiring inspection and visually inspect the part requiring inspection. That is, (1) firmly covering the part to be inspected with a manually peelable coating, and then peeling off the manually peelable coating of the part to be inspected and visually inspecting the part to be inspected; and if any damage is found in the part to be inspected, peeling off the transparent manually peelable coating of the part to be inspected and carrying out repair processing; (2) Alternatively, the surface of the part to be inspected is covered with a transparent manually peelable coating, and the surrounding surface of the part to be inspected and the transparent manually peelable coating are firmly bonded via a primer, that is, the part to be inspected is firmly covered with a transparent manually peelable coating, and then the part to be inspected is visually inspected through the transparent manually peelable coating. If any damage is found in the part to be inspected, the transparent manually peelable coating of the part to be inspected is peeled off and repaired.

[0017] Next, structures that are the subject of the present invention include oil tanks, liquefied gas tanks, bridges, tunnels, chemical plants, large buildings, ships, and the like. Examples of steel structures for storing liquids include tanks for dangerous liquids such as petroleum, high-pressure gas tanks such as LPG, piping, and pontoons for floating roof tanks. Moreover, as the rust-preventive coating film applied to the entire surface of these steel structures, high-strength resins having high rigidity, such as vinyl ester and epoxy, have been used.

[0018] In addition, the blasting process for removing the coating from the parts to be inspected is carried out by projecting an abrasive material. The abrasive material may be, for example, fine particles such as iron balls, natural silica sand, garnet, silicon carbide, or fused alumina. The abrasive particles preferably have a particle size in the range of 30 to 500 μm, and are projected onto the surface of the substrate by being carried by high-pressure air or high-pressure liquid. The spray pressure in this case is usually 2 to 6 kg / cm. 2 A range of is used. As the masking tape (tape for masking), commercially available adhesive tapes and the like can be used, but it is preferable to use a tape that leaves no residue when peeled off. In the present invention, the "inspection" in the final step is a non-destructive inspection, i.e. This is performed using visual inspection, magnetic particle inspection, radiographic inspection, ultrasonic inspection, magnetic inspection, penetrant inspection, eddy current inspection, strain measurement, leak testing, acoustic emission (AE), infrared inspection methods, etc. Here, a coating film having manual releasability (that is, the property of being able to be held between fingers and peeled off), which is a key requirement of the present invention, will be described. "Peeling" is the phenomenon in which a part or all of a material separates from its original position (in the case of a coating, from the coated surface). As a result of extensive research, the inventors have found that polyurea monopolymer or a copolymer (blend) of polyurea and polyurethane has excellent manual peelability, and that these resins are excellent high-strength resins while also having excellent elasticity, and have therefore been adopted in the present invention.

[0019] Peelability focuses on the ductility of a material, which is the property of being plastically stretched beyond its yield point. Ductility is quantitatively expressed as elongation, and the greater the elongation of a material, the more ductile the material. For example, polyurea, polyurethane urea, ionomer, etc. are high-strength materials with large tensile strength, but at the same time, they are tough and stretchable without breaking, and break when they reach their tensile strength. In other words, they have the property of continuing to stretch without breaking until they reach their tensile strength. On the other hand, hard paints do not stretch even if they have a high tensile strength, so they undergo brittle fracture when they reach their tensile strength. As a result, even if partial separation or peeling occurs due to fracture, sustained peeling does not occur. From this, we discovered that even if the coating is made of the same high-strength material, the ability to peel off is determined by the way the coating breaks, either ductile or brittle. The "stress-strain diagram," which quantitatively shows the elongation of a coating film, indicates that if the elongation when peeled off with a tensile force greater than the coating film's adhesive strength is less than the elongation at break, the coating film will peel off without breaking. When the elongation required for peeling reaches the elongation at break, the coating film will break. Elongation is one of the mechanical properties, and while tensile strength indicates the strength of a material, it is an index that indicates the ease of deformation. The elongation percentage here refers to the percentage of elongation when the coating film is subjected to force and deforms and breaks, that is, the elongation percentage at break. Quantitatively, the condition for the coating to peel off without breaking can be expressed by the inequality "elongation at the time of coating peeling" < "elongation at the time of coating breakage."

[0020] With regard to manual peelability, the tensile force required for peeling decreases as peeling progresses, so when peeling is performed with a constant tensile force, the coating film is peeled off with an accordingly large tensile force. As a result, the coating can be peeled off with a force smaller than the adhesion force of the coating. This is called manual peelability. The reason for this is that the principle of leverage works on the peeling tape. The principle of leverage is the ability to generate a large force with a small force. The formula for the principle of leverage is "distance A x weight = peeling B x force." If we consider the point where the edge of the coating film is pinched between the fingers as the point of force, and the point where the coating film is separated from the coated surface as the point of application, then the length of the coating film from the point of force to the point of application corresponds to distance B. In other words, if we consider this length of the coating film to be peeling B, the longer the distance, the greater the force acting on the point of application, and therefore less force is required to peel it off. In the peeling condition, "adhesive strength of the coating film" < "tensile force required for peeling", when peeling starts, the tensile force must be greater than or equal to the adhesive strength of the coating film in order to peel it off, but as peeling progresses, the Deco principle comes into play, and it becomes possible to peel it off with a force less than the adhesive strength of the coating film. In other words, the inequality is in the opposite direction, "tensile force required for peeling" < "adhesive strength of the coating film", which is why it is manually peelable. The acceleration of peeling is proportional to the force acting on the object, so if the force acting on the object increases in proportion to the increase in distance B, the peeling speed will increase accordingly. This is the acceleration of peeling.

[0021] The numerical basis for manual peelability is that in the case of oil tanks, crude oil is used for high-pressure cleaning to wash off the crude oil adhering to the walls of the side and bottom plates as part of the preparation work for opening the tank. When the crude oil is sprayed onto the coating at high speed, the adhesion strength of the coating is 2 to 3 N / mm 2 If this is the case, the coating will not peel off during cleaning. In comparison, the tensile strength of polyurethane is 24N / mm 2 Therefore, even if the tensile strength of the blend (polyurea-polyurethane copolymer) is reduced by half, the adhesion strength required for the coating is still 6-5N / mm 2 There is ample room for this. The molecular chains of the urea bonds in these resins, which were originally developed as explosion-resistant paints, have strong physical properties, so even if you pull them up by hand, no part of the resin will remain as residue in the grooves or depressions of the welds. In comparison, the tensile strength of polyurea is 24N / mm 2 This is because even if the tensile strength of the blend is reduced by half, it is still sufficient to provide the required adhesive strength for the coating film. Originally developed as explosion-resistant paints, the molecular chains of these polymer resins are connected by numerous intricately intertwined urea bonds, giving them strong physical properties that mean the resin will not break even if pulled up by hand, and no residue remains in the valleys between welds in steel plates. The emergence of a completely removable coating will revolutionize the world of paint. Eliminating the need for blasting work will reduce damage to welds in steel structures and will enable faster non-destructive testing, especially magnetic particle testing, which will lead to shorter open period. Not only that, it will also make it possible to reuse and repeatedly use the coating, allowing the coating to be used to its full expected service life. This will lead to a reduction in the amount of waste coating material disposed of in landfill by half to one third. When considered in terms of tank substrates across all industries, this will contribute significantly to environmental conservation in Japan.

[0022] Thus, while the emphasis in coating films has been placed on mechanical strength, the present invention places emphasis on the ductility of the coating film, enabling detailed safety management according to the diversity of equipment damage modes. For example, if a steel plate is penetrated by a crack or corrosion, the shape-following ability of the coating film will seal the opening, making it possible to prevent leakage or outflow of stored materials. In other words, it was discovered that the above-mentioned polyurethane resin has strong adhesive properties, yet also has excellent peelability (if you make a cut in it, pinch the edge and pull it up, it will peel off cleanly) and good elasticity, and so it was applied to the present invention.

[0023] In particular, the solvent-resistant, manually peelable coating film used in the present invention is preferably one containing, as a main component, a polyurea monopolymer or a polyurethaneurea, which is a copolymer of polyurethane and polyurea. In order to impart solvent resistance, it is preferable to disperse or contain fine powder or flakes of one type selected from silica, mica, or glass. Also, increasing the amount of these fine powders or flakes added can weaken the adhesiveness which enhances manual peelability. A coating film that combines both solvent resistance and manual peelability (hereinafter referred to as a "solvent-resistant and manually peelable coating film") preferably has the following three characteristics. (1) Solvent resistance This is an oil-resistant paint suitable for use on tanks for hazardous liquid materials such as petroleum, high-pressure gas tanks such as LPG, piping, and pontoons of floating roof tanks. (2) Manual peelability In the present invention, a coating film that can be peeled off manually is used, so there is no need to use heavy machinery such as compressors as in the conventional method of peeling off existing coatings by blasting, and no dust is generated during peeling. Furthermore, there is no adhesion of metal welded to the steel plate due to blasting, the steel plate surface is not damaged, and no coating residue is left on the steel plate surface. (3) Mechanical properties A coating film that has not only physical properties such as toughness and high elasticity, but also impact resistance, shape conformability, water vapor impermeability, waterproofness, chemical stability, weather resistance, chemical resistance, etc. (4) That is, the coating material which produces the solvent-resistant and manually peelable coating film (6) of the present invention having the above characteristics (1) to (3) is mainly composed of a polyurea homopolymer or a copolymer of polyurea and polyurethane, The powder or flakes are selected from silica, mica, and glass having an average particle size of 10 to 500 μm. The content of the fine powder or flakes is 5 to 35% based on the solid content mass of the solvent-resistant, manually peelable coating film (5); The tensile strength (JIS A6021:2011) of the coating film (dry film thickness 700 μm) obtained by applying the paint (6) is 2.3 to 40 N / mm 2 and The coating film (dry film thickness 700 μm) preferably has an elongation at break (JIS A6021:2011) of 50 to 500%.

[0024] The polyurea or polyurethane urea used in the present invention for producing a manually peelable coating film is a polyurea resin mainly composed of urea bonds produced by the reaction of polyisocyanate with polyamine, or a polyurethane urea resin which is a copolymer of polyurethane and polyurea, and has strong cohesive strength of molecular chains, and has outstanding mechanical characteristics such as strong, tough and highly elastic physical properties, impact resistance, high elongation, shape conformability and water vapor impermeability. For example, Mitsubishi Gas Chemical Company's polyurea resins, "MXDA" and "1,3-BAC", and Mitsui Chemical Industrial Products' "Swaer AR-450S" (tensile strength 20N / mm 2 , elongation rate 320%) and "Swaer AJ-900 (transparent type)". However, because urea bonds have low polarity and problems with solvent resistance, the mechanical properties of these resins have not been utilized in the safety and facility management of equipment and piping that handles petroleum products such as crude oil and chemical products. To address this issue, powder or flakes made from raw materials such as silicon dioxide (silica stone, mica, glass) having silanol groups were added to or mixed with these resins, thereby solving the problem of solvent resistance. Solving this issue goes beyond simply resolving various problems in facility management in the oil and petrochemical industries. By taking advantage of the physical properties of the urea bond, it will become possible to repeatedly use and reuse the coating, which will provide a foothold in reducing industrial waste emissions and lead to the solution of environmental problems. As the primer, that is, undercoat paint, for example, an epoxy-modified urethane resin (for example, trade name: "FP-UL1" manufactured by Nippon Steel Chemical & Material Co., Ltd., trade name "Aqueous Polyol" manufactured by Dai Nippon Toryo Co., Ltd., trade name "B-550M" manufactured by Mitsui Chemical Industrial Products Co., Ltd.) is used. The thickness thereof is preferably, for example, 50 μm to 500 μm.

[0025] In the present invention, the primer treatment is very important, and the surrounding surface of the part to be inspected is firmly adhered to a manually peelable coating via the primer, so that the part to be inspected is protected at all times from the outside by rainwater, etc., and after a certain period of time has passed, the coating on the part to be inspected is manually peeled off or viewed through the inspection. Next, a method for inspecting a structure according to the present invention, specifically, a method for inspecting a liquid-storage steel structure, will be described with reference to the drawings. Broadly speaking, there are three methods: Method A, Method B, and Method C. [1] Method A; Basically, this method involves applying a solvent-resistant, manually peelable paint directly to the steel plate at the paint peeling area, and then manually peeling off the paint at the time of inspection. First, as shown in Figures 1 to 6, The first step (Fig. 2) is carried out by blasting the coating (2') of the liquid storage steel structure (1) (Fig. 1) to be inspected, the entire surface of which is coated with an anti-rust coating (2), to form a strip-shaped coating-removed area (3). Next, a second step (FIG. 3) is performed in which masking tape (4) is applied to the surface of the existing coating film (2) on the outer periphery of the strip-shaped coating film peeled portion (3) produced in the first step. Then, a third step (FIG. 4) is performed in which a primer (5) is applied to the existing coating film (2) on the outer periphery of the masking tape (4) in order to firmly adhere a solvent-resistant, manually peelable coating film; A fourth step (FIG. 5) is carried out in which a paint that produces a solvent-resistant, manually peelable coating film (6) is applied to the entire surface of the coating peeling portion (3), the masking tape (4), and the primer (5) around the outer periphery of the masking tape. Next, a cutter knife (7) is used to make an incision in the solvent-resistant, manually peelable coating film (6) located on the left and right sides of the masking tape (4), and the left and right ends of the coating film (6) and the masking tape (4) are used as tabs to pick up the coating film (6) and the masking tape (4) with the fingers, lifting them up from the steel plate (1) in the area to be inspected (the strip-shaped coating film peeling portion (3)), and pulling them upward to peel them off (FIG. 6). Finally, a sixth step is carried out in which the steel sheet (1) of the inspection-required portion (2') (the steel sheet of the strip-like coating peeled portion (3)) exposed after the coating film (6) has been peeled off is visually inspected.

[0026] [2] Method B; That is, this method involves applying a solvent-resistant manually peelable paint to masking tape attached to the steel plate in the coating peeling area, and then manually peeling off the coating during inspection. As shown in Fig. 7 and Fig. 8, a first step is to peel off the coating film (2') of the liquid storage steel structure (1) to be inspected from the entire surface of the structure by blasting to produce a strip-like coating film peeled portion (3); A second step (FIG. 9) of attaching a masking tape (4) to the strip-shaped coating film peeled portion (3) formed in the first step; A third step (FIG. 10) of applying a primer (5) to the existing coating film (2) on the outer periphery of the strip-shaped coating film peeling portion (3) in order to firmly bond a solvent-resistant, manually peelable coating film; A fourth step (FIG. 11) of applying a paint that forms a solvent-resistant, manually peelable coating film (6) to the entire surface of the masking tape (4) on the surface of the coating film peeling portion (3) and the primer (5) on the outer periphery of the masking tape; A fifth step (FIG. 12) is to make an incision with a cutter knife (7) in the solvent-resistant, manually peelable coating film (6) located on the left and right sides of the masking tape (4), pick up the left and right ends of the coating film (6) and the masking tape (4) with the fingers, lift the coating film (6) and the masking tape (4) from the steel plate (1) (the strip-shaped coating film peeling portion (3)) in the inspection area, and pull them upward to peel off the coating film (6) and the masking tape (4) from the steel plate (1). and a sixth step of inspecting the steel plate (1) (the strip-like paint peeled portion (3)) of the inspection-required portion (2') that is exposed after the masking tape (4) has been peeled off.

[0027] [3] Method C; In other words, this is a method of visual inspection and daily inspection using a transparent type of manually peelable paint to detect leaks and spills early. The first step (Fig. 13) is to remove the coating (2') from the part of the liquid storage steel structure (1) to be inspected, which has an anti-rust coating (2) applied to the entire surface, by blasting to produce a strip-like coating-removed part (3); A second step (FIG. 14) of attaching a masking tape (4) to the existing coating film (2) surface on the outer periphery of the strip-shaped coating film peeled portion (3) generated in the first step; A third step (FIG. 15) is to apply a primer (5) for firmly adhering a solvent-resistant and manually peelable coating film to the existing coating film (2) on the outer periphery of the masking tape (4); A fourth step (FIG. 16) of applying a paint that forms a transparent, solvent-resistant, manually peelable coating film (6') to the entire surface of the coating film peeling portion (3), the masking tape (4), and the primer (5) on the outer periphery of the masking tape; and a sixth step of inspecting the steel sheet (1) of the inspection-required portion (2') (the steel sheet of the strip-like coating peeled portion (3)) seen through the transparent coating film (6').

[0028] Next, a brief explanation of an example of adopting the technology of the present invention for rainwater infiltration prevention measures for liquid (petroleum) structures will be given based on cross-sectional schematic diagrams: Figure 17 (X-type rainwater infiltration prevention measure) and Figure 18 (Y-type rainwater infiltration prevention measure). Regarding measures to prevent rainwater infiltration into Type X, [Application of primer] As shown in Figure 17, a primer (undercoat paint) (5) is applied to the lower part of the tank side plate (10), the front edge of the tank bottom plate protrusion (11), and the outer periphery of the berm (13) to firmly adhere the manually peelable paint (6'). Next, a paint (polyurea paint) that produces a transparent, solvent-resistant, manually peelable coating film (6') is applied over the entire surface from the underside 10 of the tank side plate to the front edge of the tank bottom plate overhang (11) and the curb (13). As a result, a transparent polyurea coating film (6') is produced, making it possible to deal with the occurrence of cracks due to rainwater infiltration from the outside, vibration, etc. In the unlikely event that rainwater gets inside the polyurethane coating, it can be seen from the outside, so the coating in that area can be cut with a cutter and peeled off with your fingers, etc., and then repaired by blasting and applying polyurethane paint.

[0029] Regarding measures to prevent rainwater infiltration into Type Y, [Application of primer] As shown in FIG. 18, first, a primer (undercoat paint) (5) for firmly adhering the manually peelable paint is applied to the front edge of the tank bottom plate projection (11) and the outer periphery of the berm (13). [Applying masking tape] Next, a transparent masking tape (4') is applied to the tank berm (13). [Forms a transparent, solvent-resistant coating that can be peeled off manually] Thereafter, a paint (polyurea paint) that produces a transparent, solvent-resistant, manually peelable coating film (6') is applied over the entire surface of the tank bottom plate, including the front edge of the protruding portion (11) and the berm (13). As a result, a transparent polyurea coating film (6') is produced, which makes it possible to deal with the occurrence of cracks due to rainwater infiltration from the outside, vibration, etc. In the unlikely event that rainwater gets into the berm 13 inside the polyurethane coating, it can be seen through and confirmed from the outside, so the coating in that area can be cut with a cutter, peeled off with fingers, etc., and then repaired by blasting and applying polyurethane coating.

[0030] In the past, paint manufacturers and users had the common sense that paint films should not peel off. However, in this invention, the necessary parts (parts that need to be inspected) are usually covered to protect the inner surface, and inspection can be easily performed at the time of inspection. Thus, the appearance of the high-strength, flexible, manually peelable coating film of the present invention will revolutionize the world of paints. The advent of manually peelable coatings not only eliminates the need for blasting, but also shortens the number of days that equipment is down; it makes non-destructive testing, especially magnetic particle testing, more efficient; and it enables the coatings to be reused and used repeatedly, extending the useful life of the coatings. This in turn reduces the amount of waste coatings that is disposed of in soil by half to one-third, contributing to environmental conservation on a global scale. [Industrial Applicability]

[0031] The present invention can be used for inspecting oil tanks, liquefied gas tanks, bridges, tunnels, chemical plants, large structures, ships, and the like. According to the present invention, not only can the part requiring inspection be easily inspected, but the part requiring inspection can also be protected until the inspection is required. Furthermore, even if a small crack occurs in the area to be inspected, the coating film of the present invention can be manually peeled off, i.e., it has high strength and flexibility and will not break, so that the inner surface can be protected.

[0032] In particular, when the coating of the polyurea monopolymer or the copolymer of polyurea and polyurethane of the present invention is used, in addition to the effects of the invention described above, there are ripple effects that bring about great merits in the safety management of facilities as described below. [a] By using a transparent type paint that is easy to deform and has good elasticity and tenacity for the weatherproofing of the connection part between the manufacturing equipment and the heat-insulating piping, 1. Early detection of external corrosion of both equipment and piping becomes possible, which helps prevent fires and explosions. 2. Gaps and cracks are less likely to occur in weatherproofing, resolving the long-standing issue of preventing external corrosion (corrosion under the insulation) of manufacturing equipment and insulated piping. During operation, manufacturing equipment and piping are constantly exposed to high-speed, high-pressure, and large volumes of hazardous liquids. The weatherproofing at the connection is constantly subjected to repeated fatigue due to vibration, which causes the deterioration of the material such as cracking and peeling to be more severe than other parts, making it easier for rainwater to penetrate. [b] By using a paint that is easily deformed, stretchy, tenacious, and transparent for the material of the rainwater intrusion prevention measures, 1. Visual inspection enables early detection of seepage, leakage, and spillage caused by corrosion on the underside of the tank bottom plate, preventing the development of a large-scale spill accident at an early stage. 2. It becomes possible to absorb deformation stress caused by repeated fatigue, and the occurrence of cracks and fractures can be suppressed. The tank bottom plate overhang is provided with rainwater intrusion prevention measures to prevent rainwater from entering through the underside of the tank bottom plate overhang. The protruding part of the bottom plate of the tank repeatedly expands and contracts in the radial direction and twists in the circumferential direction due to the loading and unloading of stored oil, and in the case of a heating tank, due to thermal expansion. As a result, the rainwater infiltration prevention measures are constantly subjected to repeated fatigue, making them prone to cracks and fractures. [c] By applying a paint that is easily deformed, stretchable, tenacious and transparent to the inside of the pontoon of the floating roof tank, 1. Early detection of stored oil leaking into the pontoon becomes possible. 2. If cracks or corrosion occur in the welds or base material of the pontoon, the coating will expand and seal the opening, preventing leakage of stored oil. These two effects of early detection of stored oil inflow and prevention of stored oil inflow make it possible to prevent floating roof subsidence and associated full-surface fires. The pontoons of floating roof tanks are constantly subjected to repeated fatigue due to the horizontal, vertical movement, and rotation of the floating roof caused by the wind above, which causes residual stress to accumulate and makes fatigue cracks at welds and stress concentration areas inevitable.

[0033] As for measures to prevent rainwater intrusion, in addition to preventing the occurrence of leaks and spills and cracks and breaks as mentioned in the previous section, early detection of these leaks and spills will also contribute to improving the inspection process. The work to remove the rainwater intrusion prevention measures is considered hot work because sparks fly when blasting, so it will be carried out in conjunction with blasting work and restoration work on the coating on the tank bottom plate. The work to remove the rainwater intrusion prevention measures is considered hot work because sparks fly when blasting, so it is carried out at the same time as the blasting work on the coating on the tank bottom plate. As a result, the entire circumference of the bottom plate overhang is exposed to rain for the entire period the tank is open (several months to a maximum of just under a year), allowing rainwater to seep in to the underside of the tank bottom plate. If manual peeling becomes possible, it will be possible to peel the paint during inspections by government agencies without having to peel it off in advance when the tank is opened. In addition, by touching up the peeled paint area after the inspection is completed, immediate repair and restoration will be possible, and unnecessary exposure to the weather will be avoided. Furthermore, if the rainwater intrusion prevention measures were transparent or semi-transparent, government inspections would require only a visual inspection, and the work of removing the rainwater intrusion prevention measures would likely become unnecessary. In terms of environmental ripple effects, if there is no deterioration in the coating of transparent or semi-transparent rainwater infiltration prevention measures, the rainwater infiltration prevention measures can be reused and used repeatedly until the next open inspection, which will reduce the amount of industrial waste discharged from the factory in proportion to the number of times the tank is opened. [Explanation of symbols]

[0034] 1: Liquid storage steel structure 2: Anti-rust coating 3: Paint peeling area 4: Masking tape 5: Primer 6: Manually peelable coating 7: Cutter knife 10: Underside of tank side panel 11: Front edge of tank bottom plate 12: Protruding part 13: Dog running club

Claims

1. A method for inspecting a structure, comprising: covering a surface of a portion of the structure to be inspected with a manually peelable coating; and firmly adhering the peripheral surface of the portion to be inspected to the manually peelable coating via a primer; i.e., encapsulating the peripheral surface of the portion to be inspected with the manually peelable coating, and then cutting out and peeling off the manually peelable coating of the portion to be inspected.

2. A method for inspecting a structure, comprising: covering the surface of a portion of the structure to be inspected with a transparent, manually peelable coating; and firmly adhering the surrounding surface of the portion to be inspected to said transparent, manually peelable coating via a primer; i.e., encapsulating the portion to be inspected with the transparent, manually peelable coating that is firmly adhered to the surrounding area; and then visually inspecting the portion to be inspected through the transparent, manually peelable coating.

3. A method for inspecting a structure, comprising: covering a surface of a portion of the structure to be inspected with a transparent, manually peelable coating; and firmly adhering the transparent, manually peelable coating to the surrounding surface of the portion to be inspected with a primer; i.e., encapsulating the portion to be inspected with the transparent, manually peelable coating that is firmly adhered to the surrounding surface; and then cutting out and peeling off the manually peelable coating of the portion to be inspected, the method comprising the steps of:

4. 1. A first step of peeling off the coating film of a part (2') to be inspected of a liquid storage steel structure (1) having an anti-rust coating film (2) applied to the entire surface thereof by blasting to form a strip-shaped coating-peeled part (3); 2. A second step of attaching a masking tape (4) to the existing coating film (2) surface on the outer periphery of the strip-shaped coating film peeled portion (3) formed in the first step; 3. A third step of applying a primer (5) to the existing coating film (2) on the outer periphery of the masking tape (4) in order to firmly adhere a solvent-resistant and manually peelable coating film (6); 4. A fourth step of applying a paint that forms a solvent-resistant and manually peelable coating film (6) to the entire surface of the coating film peeling portion (3), the masking tape (4), and the primer (5) on the outer periphery of the masking tape; 5. A fifth step of making an incision with a cutter knife (7) in the solvent-resistant and manually peelable coating film (6) located at the boundary between the masking tape (4) and the primer (5), picking up the coating film (6) and the masking tape (4) with the fingers by using the left and right ends as tabs, lifting the coating film (6) and the masking tape (4) from the steel plate (belt-shaped coating film peeling portion (3)) of the inspection target portion (2'), and pulling them upward to peel them off; 6. A method for inspecting a liquid-storage steel structure, comprising a sixth step of inspecting the steel plate of the inspection-required portion (2') (the steel plate of the strip-like coating-peeled portion (3)) exposed by peeling off the manually peelable coating film (6).

5. 1. A first step of attaching masking tape (4) to the outer periphery of a steel plate of a required inspection portion (2') of a liquid storage steel structure (1) having no anti-corrosive coating on the entire surface; 2. A second step of applying a primer (5) to the outer periphery of the masking tape (4) on the steel plate for firmly adhering a solvent-resistant and manually peelable coating film (6); 3. A third step of applying a paint that produces a solvent-resistant and manually peelable coating film (6) to the entire surface of the primer (5) on the steel plate of the inspection-required portion (2'), the masking tape (4), and the steel plate on the outer periphery of the masking tape (4); 4. A fourth step of making an incision with a cutter knife (7) in the solvent-resistant and manually peelable coating film (6) located at the boundary between the masking tape (4) and the primer (5), picking up the coating film (6) and the masking tape (4) with the fingers using the left and right ends as tabs, lifting the coating film (6) and the masking tape (4) from the steel plate of the inspection-required portion (2'), pulling them upward, and peeling them off; 5. A fifth step of inspecting the steel plate of the inspection-required portion (2') from which the coating film (6) has been peeled off and exposed.

6. 1. A first step of peeling off the coating film of a part (2') to be inspected of a liquid storage steel structure (1) having an anti-rust coating film (2) applied to the entire surface thereof by blasting to form a strip-shaped coating-peeled part (3); 2. A second step of attaching a masking tape (4) to the strip-shaped coating film peeled portion (3) formed in the first step; 3. A third step of applying a primer (5) to the existing coating film (2) on the outer periphery of the strip-shaped coating film peeling portion (3) in order to firmly adhere a solvent-resistant and manually peelable coating film; 4. A fourth step of applying a paint that forms a solvent-resistant and manually peelable coating film (6) to the entire surface of the masking tape (4) on the surface of the coating film peeling portion (3) and the primer (5) on the outer periphery of the masking tape; 5. A fifth step of making an incision with a cutter knife (7) in the solvent-resistant, manually peelable coating film (6) located on the left and right edges of the masking tape (4), picking up the left and right edges of the coating film (6) and the masking tape (4) with the fingers, lifting the coating film (6) and the masking tape (4) from the steel plate (1) (the strip-shaped coating peeling portion (3)) in the inspection area, and pulling them upward to peel off the masking tape (4) from the steel plate (1); 6. A method for inspecting a liquid storage steel structure, comprising: a sixth step of inspecting the steel plate (1) (the strip-shaped paint peeling portion (3)) of the inspection-required portion (2') exposed by peeling off the masking tape (4).

7. 1. A first step of peeling off the anti-rust coating from a portion (2') to be inspected of a liquid storage steel structure (1) having an anti-rust coating applied to the entire surface thereof by blasting to form a strip-shaped coating-peeled portion (3); 2. A second step of attaching a masking tape (4) to the existing coating film (2) surface on the outer periphery of the strip-shaped coating film peeled portion (3) formed in the first step; 3. A third step of applying a primer (5) to the existing coating film (2) on the outer periphery of the masking tape (4) in order to firmly adhere a manually peelable coating film (6); 4. A fourth step of applying a paint to the surface of the coating film peeling portion (3), the masking tape (4) and the entire surface of the primer (5) to form a transparent coating film (6') that can be peeled off manually; 5. A fifth step of visually inspecting the parts to be inspected through the transparent, manually peelable coating film (6').

8. 1. A first step of applying masking tape (4) to a steel plate of a part (2') to be inspected of a liquid storage steel structure (1) having no anti-corrosive coating on the entire surface; 2. A second step of applying a primer (5) to the outer periphery of the steel plate of the inspection-required portion (2') for firmly adhering a solvent-resistant, manually peelable coating film (6); 3. A third step of applying a paint that forms a solvent-resistant and manually peelable coating film (6) to the entire surface of the masking tape (4) of the steel plate of the inspection-required portion (2') and the primer (5) of the steel plate on the outer periphery of the inspection-required portion (2'); 4. A fourth step of making an incision with a cutter knife (7) in the solvent-resistant and manually peelable coating film (6) located on the left and right edges of the masking tape (4), picking up the left and right edges of the coating film (6) and the masking tape (4) with fingers, lifting the coating film (6) and the masking tape (4) from the steel plate of the inspection-required portion (2'), pulling them upward, and peeling the masking tape (4) from the steel plate of the inspection-required portion; 5. A method for inspecting a liquid storage steel structure, comprising a sixth step of inspecting the steel plate of the inspection-required portion (2') exposed by peeling off the masking tape (4).

9. 1. A first step of peeling off the surface of the rainwater infiltration prevention measure of the liquid storage structure by blasting to form a rainwater infiltration prevention measure peeled off portion; 2. A second step of applying a primer (5) to the lower part of the side panel (10) and the front edge of the bottom panel overhang (11) of the liquid storage structure and the outer periphery of the curb (13) for firmly adhering a transparent, manually peelable coating film (6'); 3. A third step of applying a paint to the entire primer surface of the rainwater intrusion prevention measure peeling portion and the entire surface between all the primers to form a manually peelable transparent coating film (6'); 4. A method for inspecting a liquid storage structure, comprising a fourth step of visually inspecting the peeled-off portion of the rainwater intrusion prevention measure seen through a transparent coating film (6').

10. 1. A first step of peeling off the surface of the rainwater infiltration prevention measure of the liquid storage structure by blasting to form a rainwater infiltration prevention measure peeled off portion; 2. A second step of applying a primer (5) to the front edge of the bottom plate overhang (11) of the liquid storage structure and the outer periphery of the berm (13) for firmly adhering a transparent, manually peelable coating film (6'); 3. A third step of attaching a transparent masking tape (4') to the berm (13) of the rainwater intrusion prevention measure peeling portion formed in the first step; 4. A fourth step of applying a paint to the entire primer surface of the rainwater intrusion prevention measure peeling portion and the entire surface between all the primers to form a manually peelable transparent coating film (6'); 5. A method for inspecting a liquid storage structure, comprising a fifth step of visually inspecting the peeled-off portion of the rainwater intrusion prevention measure seen through a transparent coating film (6') and a transparent masking tape (4').

11. 1. The first step is to apply a primer (5) to the outer periphery of the substrate of the structure (1) at the area (2') that is to be visually inspected for safety, for the purpose of firmly adhering a transparent, manually peelable coating film (6'); 2. A second step of applying a paint to the entire surface of the substrate and the primer (5) of the required visual inspection area (2') to form a transparent, manually peelable coating film (6'); and a third step of visually inspecting the substrate of the portion (2') to be visually inspected through a transparent coating film (6').

12. 1. A first step of attaching a transparent masking tape (4') to a substrate of a portion (2') of a structure (1) that is to be visually inspected for safety reasons; 2. A second step of applying a primer (5) to the outer periphery of the substrate in the region to be visually inspected (2') for firmly adhering a transparent, manually peelable coating film (6'); 3. A third step of applying a paint to the entire surface of the masking tape (4') and the primer (5) to form a transparent, manually peelable coating film (6'); 4. A method for inspecting a structure, comprising a third step of visually inspecting the substrate of the portion (2') to be visually inspected through a transparent coating film (6').

13. The method for inspecting a structure according to any one of claims 1 to 12, characterized in that the paint which produces the manually peelable coating film (6, 6') is mainly composed of a polyurea monopolymer.

14. The method for inspecting a structure according to any one of claims 1 to 12, characterized in that the paint that produces the manually peelable coating film (6, 6') is mainly composed of a copolymer of polyurea and polyurethane.

15. The paint which produces the manually peelable coating film (6) is mainly composed of a polyurea monopolymer or a copolymer of polyurea and polyurethane, The powder or flakes are selected from silica, mica, and glass having an average particle size of 10 to 500 μm. The content of the fine powder or flakes is 5 to 35% based on the solids mass of the solvent-resistant, manually peelable coating film (6); The tensile strength (JIS A6021:2011) of the coating film (dry film thickness 700 μm) obtained by applying the paint (6) is 2.3 to 40 N / mm ２ and The coating film (dry film thickness 700 μm) has an elongation at break (JIS A6021:2011) of 11 to 500%, The adhesion strength of the coating is 10 to 100 kg / cm ２ 9. The method for inspecting a structure according to claim 1, 4, 5, 6, or 8, wherein

16. The method for inspecting a structure according to any one of claims 1 to 15, characterized in that the structure (1) is a tank for storing or handling a hydrocarbon oil such as petroleum, or a tank for storing or handling a liquefied gas such as LPG.

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