JP4498187B2 - Foam leak test liquid and leak test method - Google Patents

Description

  The present invention relates to a foam leakage inspection liquid used when detecting leakage points of various containers and pipes and penetration defects of welded structures by a foaming phenomenon, and a leakage test method using this inspection liquid.

  Conventionally, various methods are used to detect penetration defects that cause leakage in containers and piping. For example, there are a helium leak test method, a halogen leak test method, an ammonia leak test method, a foam leak test method, and the like as methods for detecting a gas leak by applying pressure. Is more widely used than other methods because the test method is simple and no special equipment or equipment is required.

  The foam leakage test method is a method in which a test solution is applied to the outer surface of a test body whose inside is pressurized, and a penetration defect is detected by bubbles generated by the leaked gas. As the test solution used at that time, an aqueous solution containing a water-soluble surfactant having good foamability is generally used (for example, see Patent Documents 1 to 3). Are, for example, soaps, anionic surfactants such as sodium alkylbenzenesulfonate, and HLB (Hydrophilic-Hydrogen- Lipophilic-Balance) is a nonionic surfactant having a strong hydrophilicity of 10 or more. In addition, a rust inhibitor, an antiseptic, an antifreezing agent, a viscosity modifier, and the like are added to the conventional foam leakage inspection liquid depending on the application.

  For example, Patent Document 1 contains 0.5 to 10% by mass of polyoxyethylene noniphenyl ether as a nonionic foaming agent (nonionic surfactant) and N, N as a nonionic foam stabilizer. -0.5 to 10% by mass of dihydroxyethyl laurylamide, 0.35 to 7% by mass of a carboxyanionic surfactant as an anionic rust inhibitor, and 0 of benzotriazole as a cationic rust inhibitor A composition for gas leakage detection comprising 0.08 to 1.7% by mass and further comprising an aqueous solution to which benzoic acid is added as an antiseptic and rust inhibitor is disclosed.

  Further, in Patent Document 2, a foam leak test liquid comprising an aqueous solution containing 0.01 to 10% by mass of a surfactant and 0.0001 to 0.01% by mass of a fluorescent dye, and this foam leak test liquid are tested. A leak test method is disclosed in which foam formation is detected while being applied to a body and irradiated with ultraviolet rays in a dark place. When the leak test method described in Patent Document 2 is used, a penetration defect can be easily detected even when the test specimen is white or transparent.

Further, Patent Document 3 discloses a water-soluble organic solvent having two or more hydroxyl groups and having a boiling point of 150 ° C. or higher, for example, ethylene, so that it can be used even when the temperature of the specimen is as high as 80 to 250 ° C. Water-soluble nonionic surfactants containing 90 to 99.9% by weight of glycol and glycerin and the like and having two or more CH ₂ CH ₂ OH groups or CH ₂ CH ₂ O groups, such as polyoxyethylene alkyl ethers and A foam leak test liquid containing 0.1 to 10% by mass of fatty acid diethanolamide or the like has been proposed.

JP 58-48050 A JP-A-10-26572 JP-A-10-281917

  However, the conventional techniques described above have the following problems. The conventional foam leakage inspection liquids described in Patent Documents 1 to 3 have no problem in the sensitivity of detecting gas leakage from penetration defects or the like, but since the surfactant remains on the surface of the test specimen after inspection, If left for a long period of time, there is a problem that rust is generated at the inspection site and corrosion is likely to occur. In addition, for steel products and cast steel products, paint may be applied for the purpose of rust prevention after inspection, but if the coating of the test solution remains on the surface, paint repelling, peeling of the paint film, etc. Is likely to occur, and has the problem of adversely affecting the coating after inspection.

  Furthermore, if a penetration defect or pinhole is detected as a result of foam leakage inspection, the part may be repaired by filling it with organic putty or resin, but in this case also the inspection liquid remains in the defect. If so, there is a problem that the adhesiveness of the filler is lowered and the repair strength is significantly lowered. In order to prevent these problems, it is necessary to remove the test solution from the surface of the specimen by washing or wiping after the test is completed, but it takes time and effort to completely remove the test solution. There is a problem that time increases.

  The present invention has been made in view of such a problem, and even if it remains on the surface, the test specimen does not corrode, and does not adversely affect the coating and repair performed after the inspection. The purpose is to provide a test method.

The foam leak test liquid according to the first invention of the present application is an aqueous solution containing a water-soluble resin that undergoes oxidative polymerization in the foam leak test liquid applied to the surface of the test object to be inspected during the foam leak test . The total content of non-volatile components including the resin is 3.82 to 35% by mass, and the surface tension is 40 mN / m or less.

  In the present invention, instead of a water-soluble surfactant, a water-soluble resin that undergoes oxidative polymerization is added as a foaming agent, so that water as a solvent volatilizes after the test, so that the water-soluble resin is in the air. It reacts with oxygen and undergoes oxidative polymerization, and a film made of a water-soluble resin is formed on the surface of the specimen. Since this resin film can be directly coated with a paint or filled with a repairing agent such as a resin or putty, it is not necessary to remove the inspection liquid after the foam leakage test as in the prior art. Moreover, since the dry film of this water-soluble resin blocks water and oxygen, the effect of preventing the occurrence of rust and corrosion can be obtained. Furthermore, the foam leak test liquid of the present invention is optimized for the amount of non-volatile components mainly composed of water-soluble resin and the surface tension of the test liquid. It penetrates into fine penetration defects that cannot be detected or overlooked in the foam leakage inspection, and the fine penetration defects can be blocked by a resin film formed after the inspection. Thereby, the leakage from the penetration defect which could not be detected by the inspection can be prevented.

  The water-soluble resin is, for example, at least one resin selected from the group consisting of a water-soluble alkyd resin, a water-soluble modified alkyd resin, a water-soluble epoxy ester resin, a water-soluble acrylic resin, and a water-soluble melamine resin.

  Further, the foam leakage inspection liquid may further contain 0.005 to 0.5% by mass of a fluorosurfactant. Thereby, surface tension can be made low, without reducing the adhesiveness with respect to the coating material and repair agent on the surface of a test body, and the outstanding foamability is obtained. In that case, the fluorosurfactant is at least one selected from the group consisting of perfluoroalkylcarboxylates, perfluoroalkylethylene oxide adducts, perfluoroalkyltrimethylammonium salts, and perfluoroalkylaminosulfonates. Surfactants can be used.

  Furthermore, the total content of the nonvolatile components may be 15 to 25% by mass. Thereby, the outstanding foamability is obtained.

  The leak test method according to the second invention of the present application is characterized in that the above-described foam leak test solution is applied and foaming from the leak point is detected.

In the present invention, since a test solution in which a water-soluble resin that undergoes oxidative polymerization is added as a foaming agent is used, water as a solvent is volatilized to react the water-soluble resin with oxygen in the air, etc. the method, by oxidative polymerization of a water-soluble resin of the test solution after the inspection, it is possible to form the resin to be film on the surface of the specimen and through the defect. As a result, it is possible to prevent the occurrence of corrosion without removing the test solution on the surface of the test body, and it is possible to directly coat the paint on the coating, and to use other resins, etc. The defect repair can be carried out.

  According to the present invention, since a water-soluble resin that undergoes oxidative polymerization is used as a foaming agent, by oxidizing and polymerizing the water-soluble resin after completion of the inspection, the surface of the test specimen and the penetration defects are obtained. A resin film with excellent adhesion to paints and repair agents can be formed, so that coating and repair can be carried out without removing the inspection solution. Can also be prevented.

  Hereinafter, embodiments of the present invention will be specifically described. First, the foam leak test liquid according to the first embodiment of the present invention will be described. The foam leakage inspection liquid of the present embodiment (hereinafter simply referred to as inspection liquid) is an aqueous solution containing a water-soluble resin that undergoes oxidative polymerization when exposed to a gas containing oxygen such as air, and has a nonvolatile component content. In addition to 0.5 to 35% by mass, the surface tension is 40 mN / m or less. The non-volatile component in this test solution is a component that remains on the surface of the specimen after water as a solvent volatilizes, and is mainly a water-soluble resin.

  The water-soluble resin in the test liquid of the present embodiment may be foamable and can be oxidized and polymerized by air or the like, for example, water-soluble alkyd resin, water-soluble modified alkyd resin, water-soluble epoxy ester resin, water-soluble At least one resin selected from the group consisting of acrylic resins and water-soluble melamine resins can be used. This allows the water-soluble resin remaining on the surface of the test specimen to be polymerized and cured at room temperature after the inspection is completed, so that a paint can be applied directly thereon to form a coating film, or an organic putty or It can be repaired by filling a resin or the like. In addition, two or more types of water-soluble resins may be added to the test solution of this embodiment.

  In addition, the foaming property of the test liquid according to the present embodiment is the foaming specified in JIS standard Z-2329 using a water-soluble resin aqueous solution prepared by dissolving a water-soluble resin in water so as to have a concentration of 15% by mass. When applied to one side of a foam test piece (a stainless steel plate having a thickness of 0.1 mm formed with a hole having a diameter of 30 μm) in the leak test method and the air on the opposite side is pressurized, 0.004 to 0 It is desirable that foaming can be confirmed with a minimum foaming pressure of about 0.005 MPa. In addition, when foaming is not performed at the above-mentioned minimum foaming pressure, a foaming property may be enhanced by adding a fluorosurfactant.

  Hereinafter, the reason for limiting the numerical value of the test liquid of this embodiment will be described.

Nonvolatile component: 3.82 to 35% by mass
When the non-volatile component is less than 3.82 % by mass, the water-soluble resin content is reduced, a uniform film cannot be obtained, and the generated bubbles are immediately broken, so that it is difficult to confirm the leaked portion. Become. On the other hand, if the non-volatile content exceeds 35% by mass, the content of the water-soluble resin is increased and the viscosity of the test solution is increased. Therefore, the content of the nonvolatile component is set to 3.82 to 35% by mass. The content of the nonvolatile component is preferably 15 to 25% by mass. Thereby, the viscosity of the test solution is less than 500 mPa · S, and good foamability and a uniform film can be obtained.

Surface tension: 40 mN / m or less When the surface tension of the test liquid exceeds 40 mN / m, foamability and wettability with respect to the test specimen are lowered, and the test liquid is difficult to enter into fine defects. Therefore, the surface tension of the test solution is set to 40 mN / m or less. Further, the lower the surface tension, the better the foamability and wettability, and further the permeability to fine defects. Therefore, the surface tension is preferably lower.

  Moreover, in the test solution of this embodiment, an additive may be added in order to reduce the surface tension. In that case, it is desirable to use a fluorosurfactant that can reduce the surface tension with a small amount of addition and does not adversely affect the specimen, the coating film formed after the inspection, and the repair agent. Examples of the fluorine-based surfactant added to the test solution of the present embodiment include perfluoroalkyl carboxylate, perfluoroalkyl ethylene oxide adduct, perfluoroalkyltrimethylammonium salt, perfluoroalkylaminosulfonate, and the like. Can be mentioned. Moreover, when adding a fluorine-type surfactant, it is desirable that the addition amount shall be 0.005 to 0.5 mass%. When the addition amount of the fluorosurfactant is less than 0.005% by mass, the effect of lowering the surface tension cannot be obtained, and when the addition amount of the fluorosurfactant exceeds 0.5% by mass, the surface tension is increased. Does not decrease any more, and the effect commensurate with the amount added cannot be obtained.

  Furthermore, in the test solution of this embodiment, a water-soluble rust preventive such as an organic acid amine salt type, an organic acid salt type, a fatty acid amine salt type and a surfactant amine salt type should be added as necessary. Can do. Thereby, the rust prevention effect with respect to the test body surface can be improved.

  The test liquid of this embodiment can detect the penetration defect of a test body with high sensitivity similarly to the conventional test liquid. In addition, since the test liquid of this embodiment uses a water-soluble resin instead of a conventionally used water-soluble surfactant as a foaming agent, it has good adhesion after drying and is a uniform resin. A strong resin film having a rust prevention property can be formed by forming a film and further oxidatively polymerizing the resin component. Thereby, even if it leaves for a long period of time without removing a test | inspection liquid, generation | occurrence | production of rust and corrosion can be prevented with this resin film. Furthermore, the resin film can be overcoated with a coating material or filled with a repair agent. As a result, it is not necessary to remove the inspection liquid after the inspection, so that the workability in the foam leakage inspection can be improved and the working time can be shortened.

  Furthermore, since the inspection liquid of this embodiment has excellent wettability, it penetrates into fine penetrating defects at a level that cannot be detected by the foam leakage inspection, and the fine penetrating defects are formed by the resin film formed after the inspection. Since it can be closed, it is possible to prevent leakage from penetration defects that could not be detected by inspection. In addition, the present inventors, in JP-A-2004-286588, proposed a leak inspection agent capable of detecting a through defect and repairing a fine through defect in the same manner as the inspection liquid of this embodiment. However, the leakage inspection agent described in Japanese Patent Application Laid-Open No. 2004-286588 differs from the inspection liquid used in the present embodiment in the inspection method used. For this reason, the leak test agent described in JP-A-2004-286588 is completely different in composition from the test solution of this embodiment.

As the overcoating paint to test liquid resin to be film formed by the present embodiment, for example, oily type, synthetic resin, phthalic acid resin, epoxy resin, chlorinated rubber-based, polyurethane-based and A vinyl resin system etc. are mentioned and the paint generally used now can be used.

Next, a leak test method according to the second embodiment of the present invention will be described. The leak test method of the present embodiment is a foam leak test method for detecting penetration defects such as containers and pipes using the inspection liquid of the first embodiment described above. In the leakage test method of the present embodiment, first, the inside of the test body such as a container and piping is pressurized with air or a gas such as nitrogen gas, and the surface of the test body is subjected to the above-mentioned by an oiler, a brush, a spray gun, or the like. The test liquid of the first embodiment, that is, an aqueous solution containing a water-soluble resin that undergoes oxidative polymerization, a non-volatile component content of 3.82 to 35% by mass, and a surface tension of 40 mN / m or less is applied. . Then, by observing the foaming phenomenon on the surface of the test body, the location where the gas leaks, that is, the location where there is a penetration defect is confirmed.

  In the leakage test method of the present embodiment, since a test solution to which a water-soluble resin that undergoes oxidative polymerization is added as a foaming agent in place of a water-soluble surfactant is used, water as a solvent is added after the test is completed. By volatilizing and reacting the water-soluble resin with oxygen in the air, the water-soluble resin undergoes oxidative polymerization, and a resin film is formed on the surface of the specimen and in the penetrating defects. This water-soluble resin is not corrosive to the specimen, and the surface of the specimen is covered with a resin film formed after polymerization. Rust and corrosion do not occur on the body surface. Furthermore, since the resin film formed from this water-soluble resin has good adhesion to the test specimen and general paints and fillers, a coating film can be applied to the surface of the test specimen without removing the test solution. It is possible to form or repair a defective part. As a result, workability in the foam leak inspection can be improved, and the work time can be shortened.

  Hereinafter, the effect of the Example of this invention is demonstrated compared with the comparative example which remove | deviates from the scope of the present invention. First, water, a water-soluble resin and a rust preventive agent are placed in a 1 liter container, and in some samples, a fluorosurfactant is added and mixed for 30 minutes with a stirrer. Test solutions of Examples 1 to 8 were prepared. Similarly, water, a water-soluble resin, and a nonionic surfactant are placed in a 1 liter container, and in some samples, a fluorosurfactant and / or a water-soluble rust inhibitor are added, and the mixture is stirred with a stirrer. The test solutions of Comparative Examples 1 to 6 having the compositions shown in Table 1 below were prepared by mixing for 30 minutes. Furthermore, as a conventional example, water, a nonionic surfactant and a water-soluble rust preventive agent are placed in a 1 liter container, mixed for 30 minutes with a stirrer, and the test solution of Comparative Example 7 having the composition shown in Table 1 below is used. Was made. Then, the surface tension and the amount of nonvolatile components of the test solutions of Examples 1 to 8 and Comparative Examples 1 to 7 produced by the above-described method were obtained. At that time, the surface tension was measured with a Dunui type surface tension meter. Moreover, the amount of non-volatile components was measured for the amount of residue after drying for 30 minutes at a temperature of 110 ° C. The above results are also shown in Table 1 below.

  The water-soluble alkyd resin 1 shown in Table 1 above is “Watersol S-311 (trade name)” manufactured by Dainippon Ink & Chemicals, Inc., which has a non-volatile component of 50% by mass. Non-volatile component is 65% by mass in “Watersol S-322 (trade name)” manufactured by Nippon Ink Chemical Co., Ltd., and the water-soluble acrylic resin 1 is non-volatile component in “Allolon 460 (trade name)” manufactured by Nippon Shokubai Co., Ltd. The water-soluble acrylic resin 2 is “Watersol S-744 (trade name)” manufactured by Dainippon Ink and Chemicals, the nonvolatile component is 40% by mass, and the water-soluble epoxy ester resin is Dainippon. Ink Chemical Co., Ltd. “Watersol S-312 (trade name)” has a non-volatile component of 66 mass%. Fluorosurfactant A is a perfluoroalkylethylene oxide adduct (“Megafac F-1405 (trade name)” manufactured by Dainippon Ink and Chemicals), and fluorosurfactant B is a perfluoroalkyltrimethylammonium salt ( "Megafac F-150 (trade name)" manufactured by Dainippon Ink & Chemicals, Inc.) and fluorosurfactant C are perfluoroalkyl carboxylates ("Megafac F-120 (trade name) manufactured by Dainippon Ink and Chemicals, Inc." ) "). Furthermore, the nonionic surfactant is polyoxyethylene alkyl ether (manufactured by Nippon Oil & Fats Co., Ltd.), the water-soluble rust preventive agent is “Rasmin w-50 (trade name)” manufactured by Kyoeisha Chemical Co., Ltd., and the non-volatile component is 50% by mass.

  Next, for the test solutions of Examples 1 to 8 and Comparative Examples 1 to 7, the paintability, leakage detection performance, paint top coatability, cross-cut adhesion, fine penetration defect repair effect, and suitability with repair agents such as putty Sexuality was evaluated. Hereinafter, the evaluation method and evaluation criteria for each evaluation item will be described.

The wettability is whether or not the surface of the steel sheet is wet evenly when the test liquid is applied to a rolled steel sheet (JIS standard G3141) having a width of 50 mm, a length of 150 mm, and a thickness of 0.8 mm. Observed. As a result, the case where the wettability to the steel sheet surface was good was evaluated as “◯”, the case where it was slightly inferior, and the case where it was inferior, and “X”.

Leak detection performance Leak detection performance is achieved by using a foamed liquid test piece specified in JIS standard Z2329, applying a test liquid to one side of this test piece, and applying air on the other side to 0.005 MPa. When pressed, foaming due to air leakage was confirmed. As a result, the case where foaming was good and the leaked part could be clearly confirmed was marked with ◯, and the case where the leaked part could not be confirmed without foaming was marked with x.

Topcoatability of paint The topcoatability of paint was evaluated based on JIS standard K5600-3-4. Specifically, the test solution was applied to the rolled steel sheet, and after 24 hours, an acrylic paint was applied thereon to evaluate whether or not a uniform coating film free from repellence or the like was obtained. As a result, the case where there was no repelling was indicated as ◯, and the case where there was repelling was indicated as x.

Cross- cut adhesion The cross-cut adhesion is applied when the cut film is cut with a cutter in accordance with JIS standard K5600-5-6, and then the adhesive tape is applied and peeled off. The state of the film was confirmed. As a result, the coating film was not peeled off, and the coating film was peeled off.

Effect of repairing fine penetration defects First, a welding vessel having a slight leak at the welded portion was prepared, and after applying Tasetorek Check (trade name) manufactured by Taseto Co., Ltd. to this welding vessel, 0.005 MPa (0.051 kgf / cm ² ), and the location of leakage due to foaming was confirmed. Next, after thoroughly washing the place where the tasserie check (trade name) was applied with water and drying the surface, the test solution of the example or comparative example was applied to the leaked place, and the pressure was 0.005 MPa. A foam leak test was performed. And after leaving the container after a test for one week, it used the tassetry check (brand name) again, pressurized to 0.005 MPa, and performed the leak test. As a result, the case where leakage did not occur was marked with ○, and the case where leakage occurred was marked with ×.

Compatibility with repair agent First, the mild steel plate drill 9mm thick, to prepare a test piece which hole the diameter of 1mm in diameter to form a 3mm hole, the test solution of the examples or comparative examples in this specimen Was applied. Next, after leaving for 48 hours, an epoxy resin filler was applied to the portion where the test solution was applied with a brush. And after leaving for one week, the water pressure of 2.9 MPa (30 kgf / cm < ² >) was applied to the test piece, and it was confirmed whether there was any abnormality in a repair hole. As a result, the case where there was no abnormality in the repair hole was indicated as “◯”, and the case where there was an abnormality was indicated as “X”.

  The above evaluation results are summarized in Table 2 below.

As shown in Table 2, the test liquid of Comparative Example 1 having a non-volatile component amount of less than 3.82 % by mass and a surface tension of over 40 mN / m has poor wettability and leak detection performance. In the evaluation, foaming did not occur, and the leaked portion could not be confirmed. Furthermore, there was no effect of repairing fine penetration defects. Moreover, since the fluorochemical surfactant was added to the test solutions of Comparative Examples 2 and 6, the wettability was slightly improved as compared with the test solution of Comparative Example 1, but the non-volatile component was 0.5%. Since it was less than mass% and the surface tension exceeded 40 mN / m, in the leakage detection performance evaluation, no foaming was observed because foaming did not occur, and there was no effect of repairing fine penetration defects. Furthermore, although the inspection liquids of Comparative Examples 3 and 5 having a nonvolatile component amount exceeding 35% by mass had the effect of repairing the fine penetration defect, in the leakage detection performance evaluation, it was not foamed and the leakage location could be confirmed. There wasn't. Furthermore, although the amount of non-volatile components is within the range of the present invention, the test solution of Comparative Example 4 having a surface tension exceeding 40 mN / m was not foamed in the leak detection performance evaluation, and therefore, the leak location could not be confirmed. Also, there was no effect of repairing fine penetration defects. Furthermore, the test solution of Comparative Example 7 is a conventional product, and the wettability and leakage detection performance are good, but there is a repellency of the paint in the overcoatability evaluation of the paint, and in the cross-cut adhesion evaluation, Was easy to peel off and adversely affected the painting.

  On the other hand, the test solutions of Examples 1 to 8 gave good results in any evaluation of wettability, leak detection performance, cross-cut test, and paint top coatability. In addition, regarding the repair effect of the fine penetration defect and the compatibility with the repair agent, there was no abnormality in the coating film and the repair agent, and no leakage occurred.

  INDUSTRIAL APPLICABILITY The present invention can be used for foam leakage inspection for detecting leakage points of various containers and pipes and penetration defects of welded structures, and is particularly suitable for performing painting and repair after inspection.

Claims (6)

In the foam leak test liquid applied to the surface of the specimen to be inspected during the foam leak test,
An aqueous solution containing a water-soluble resin that undergoes oxidative polymerization, wherein the total content of non-volatile components including the water-soluble resin is 3.82 to 35% by mass, and the surface tension is 40 mN / m or less. Foam leak test liquid. The water-soluble resin is at least one resin selected from the group consisting of a water-soluble alkyd resin, a water-soluble modified alkyd resin, a water-soluble epoxy ester resin, a water-soluble acrylic resin, and a water-soluble melamine resin. The foam leak test liquid according to claim 1. Furthermore, 0.005 thru | or 0.5 mass% of fluorine-type surfactant is contained, The foaming leak test | inspection liquid of Claim 1 or 2 characterized by the above-mentioned. The fluorosurfactant is at least one surfactant selected from the group consisting of perfluoroalkyl carboxylates, perfluoroalkylethylene oxide adducts, perfluoroalkyltrimethylammonium salts, and perfluoroalkylaminosulfonates. The foam leakage inspection liquid according to claim 3, wherein The foam leakage inspection liquid according to any one of claims 1 to 4, wherein a total content of the nonvolatile components is 15 to 25% by mass. A leak test method, wherein the foam leak test solution according to claim 1 is applied to detect foaming from a leak location.