JPH10185742A - Material and method for leak inspection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a leak position surely, simply and with good accuracy by using a leak inspection material comprising a white layer which is formed on a colored layer, which becomes transparent when wetted and which becomes opaque when dried. SOLUTION: A colored layer 2 is formed on one face of an air-permeable film 1, and a white layer 3 is formed on it. As the air-permeable film 1, a film which permeates a liquid such as water, oil or the like can be used. The colored layer 2 is composed of a color pigment and of a paste agent which is discolored in a solvent. Especially a red color pigment is preferable as the color pigment, but a color pigment whose color tone is deep may be used. The white layer 3 is composed of a white inorganic fine powder and of a paste agent which is dissolved in a solvent. As the white inorganic fine powder, a white inorganic fine powder which becomes transparent when wetted and which becomes opaque when dried may be used. Thereby. a leak place is detected simply and surely without adding a special chemical to water beforehand in a filling water test or the like and without using a special machine or a special apparatus, and the leak place and a through defect can be detected easily.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leakage inspection material having a specific structure for detecting leakage of a liquid, and a leakage inspection method using the inspection material. In particular, a leak inspection material and its inspection for the complete inspection and maintenance inspection of large tanks and containers, the inspection of welded parts of pipes and pipes, and the easy detection of leaks of liquids such as water oozing from walls etc. Related to inspection method.

[0002]

2. Description of the Related Art There are known various inspection methods for detecting a penetrating defect causing a leak. As a method of detecting gas leakage under pressure, 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. However, these inspection methods usually require that the inside of the inspection container be sealed and pressurized, and therefore cannot be applied to an open tank or the like. In addition, if the test object is wet with water or the like, the reliability of detection is reduced. Therefore, it is necessary to sufficiently dry the test object before the test.
In addition, the helium leak test, halogen leak test, and ammonia leak test, which are considered to be highly sensitive, require a special gas to be charged, which requires machinery and equipment, and is laborious. A water filling test is known as a general test method for detecting leaks using a liquid. This method has been used for a long time during the manufacture of tanks and the like, in addition to the inspection of leakage and penetration defects, as well as the strength inspection. However, this method is very low in sensitivity as a method of detecting a penetration defect because the leaked portion is visually checked. In addition, as a method of increasing the sensitivity in the water leak test, a water-soluble fluorescent dye such as a surfactant or uranine, which improves permeability, diluted 1000 to 10,000 times with water is added to the water to be used, and darkness is added. Incidentally, a method of detecting a leaked portion while irradiating ultraviolet rays is also known. This method also requires that the power supply equipment and the inspection site be darkened, and that the amount of drug to be added is proportional to the capacity of the test object container. If not treated, it may cause environmental pollution and is hardly used.

[0003] In addition, various proposals have been made as to a method of detecting a leak using a liquid, but a special liquid is used, the detection sensitivity is low, and the work is difficult. Therefore, there are many problems, and no good inspection method has been established yet. As a technique for solving these problems, Japanese Patent Application Laid-Open No. Hei 7-306113 discloses a method in which a test piece is applied to a test piece using a leak test agent comprising a volatile solvent, a white inorganic powder and a water-soluble dye, and the leak of the liquid is detected by coloring.
No. 6,086,045. Although this method has the advantage of extremely high sensitivity, it has the drawback that if even a slight amount of dew forms on the surface of the test piece, it develops a color, and the use conditions are considerably limited. The spray method is generally used to apply this leak test agent to the surface of the test piece, but there are also problems such as scattering during application, contamination during post-treatment, and peeling of the coating film. Was.

[0004]

SUMMARY OF THE INVENTION It is a first object of the present invention to provide a new inspection material which can solve the above-mentioned disadvantages of the conventional leak test method and penetration defect inspection method. That is, in the present invention, a water filling test or a simple method without adding a special agent or the like to water or oil in advance to a leaking liquid such as an oil leak test method, and without using a special machine or device. Another object of the present invention is to provide a leak inspection material capable of reliably and accurately finding a leak location. A second object of the present invention is to solve the drawbacks of the method using a leakage test agent described in the above-mentioned publication, and to provide a method that enables an inspection even when dew condensation occurs on the surface of a test piece if the degree is not large. To provide. A third object of the present invention is to provide an inspection material capable of changing the color and inspecting when the colored layer and the white layer are wet, regardless of the type of the leaking liquid. A fourth object of the present invention is that since the form is a film type, handling is simple, scattering during application during use, contamination during post-processing,
This inspection method can also solve problems such as peeling of the coating film.

[0005]

SUMMARY OF THE INVENTION A first aspect of the present invention is to provide a breathable film, a dark colored layer provided on the breathable film, and a transparent layer provided on the colored layer when wetted. This is a leakage inspection material comprising a white layer that becomes opaque when dried. The second aspect of the present invention is a leakage inspection method in which the above-described leakage inspection material is applied to the surface of a test body and leaking liquid is detected by a change in color tone. That is, the leak inspection material of the present invention has a dark colored layer on a transparent air-permeable film, and further has a high light transmittance in a state of being wetted by a liquid on the layer, and is nearly transparent but in a dry state. Is a film-type leakage inspection material having a structure in which a white layer having a high light-blocking property is laminated in a dry state. When this film is affixed to the surface of the test specimen containing liquid, a white layer is visible from the outside, and when the liquid leaks from the inside of the test specimen, it passes through the dark colored layer and the liquid passes through this white layer. Will get wet. The white layer becomes transparent when wet, so the wet area can be seen through the transparent white layer and the color of the dark colored layer underneath can be seen, and the indication pattern of the dark colored layer formed on the white background As a result, a leaked portion of the liquid can be detected.

[0006] Since the leak inspection material of the present invention is in the form of a film, it is scattered during application during use, contamination during post-processing,
Problems such as peeling of the coating film can be solved, and reliable inspection can be performed by using a transparent and relatively durable breathable film on the outermost surface. In the invention of JP-A-7-306113, a dye that is soluble in water is used, so that the color develops even in a slight amount of water due to dew condensation, whereas in the present invention, the contained color pigment does not dissolve in a liquid, In order to form a coating film, it is necessary to leak a sufficient amount of liquid to make the white pigment sufficiently wet and transparent, and it also has a characteristic that it does not discolor with a little water such as ordinary dew. In addition, since the leakage inspection material of the present invention develops color when the white layer is wet, it can be used not only for water but also for liquids such as oil. In addition, the leak test material of the present invention can be reused as a test material after drying if the leaked material is a dry or volatile substance such as water or kerosene.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As shown in FIG. 1, a leakage inspection material according to the present invention has a colored film 2 provided on one surface of a breathable film 1,
It is sufficient that the white layer 3 is formed thereon.
Further, as shown in FIG. 2, the adhesive layer 4 can be provided under the gas permeable film 1 in order to stick the gas permeable film 1 to the test object. Further, on the white layer 2, an air-permeable transparent film 5 can be coated for protection of dirt. The breathable film of the present invention may be made to pass through a liquid such as water or oil, and specifically, for example, a film, a nonwoven fabric, or a filter paper having a fine hole, such as polyester, polyethylene, polystyrene, polypropylene, polyvinyl chloride, or a cellulose resin. Etc. can be used.

[0008] The colored layer in the leakage inspection material of the present invention comprises a colored pigment and a paste dissolved in a solvent. The colored pigment may be any one that has a particularly good red color but a good color tone. Red pigments such as azo pigments, copper phthalocyanine pigments, quinacridone pigments and dioxaazine pigments, and cadmium-based and iron oxide-based pigments as inorganic coloring pigments, specifically, for example, Shimla Red, Brilliant Carmine, Lake Red C There is conch. Specific examples of the sizing agent used for the colored layer include a cellulose resin, an acrylic resin, a polyester resin, a polyamide resin, an epoxy resin, and a petroleum resin. These coloring pigments are uniformly dissolved in a sizing agent previously dissolved in a solvent such as normal heptane or ethyl alcohol, and this solution is coated on a transparent air-permeable film. The amount of the color pigment to be used is usually preferably 3% by weight or more based on the color layer after evaporating the solvent. If it is less than 3% by weight, the color development of the leaked part is inferior.

The white layer in the leak inspection material of the present invention may be any layer that is white when dry and becomes highly transparent when wet with water or oil. The reason why this layer is white when dried is that the indication pattern of leakage is most visible when the background is white. The white layer of the present invention is composed of a white inorganic fine powder and a sizing agent dissolved in a solvent. The white inorganic fine powder may be any as long as it becomes transparent when wet and becomes opaque when dried. And fine powders of silicate, magnesium carbonate, calcium carbonate, magnesium hydroxide and the like. These may be used alone or as a mixture of several types. The particle size of the white inorganic fine powder is preferably 10 μm or less from the viewpoint of applicability and the like. In addition, a white inorganic fine powder which is white when dried, and a titanium oxide powder having a high hiding power without being transparent even if leaked are unsuitable. Specific examples of the sizing agent include a cellulose resin, an acrylic resin, a polyester resin, a polyamide resin, an epoxy resin, and a petroleum resin. These white inorganic fine powders are uniformly dispersed in a paste previously dissolved in a solvent such as normal heptane or ethyl alcohol. Then, this mixture is coated on the colored layer by screen printing or the like. At this time, a suitable dispersant, for example, Nonion OP-80R (manufactured by NOF Corporation) can be used. The thickness of the white layer is preferably as small as possible, as long as it has a concealing property with respect to the colored layer. However, in practice, the thickness is required to be 10 μm or more.

[0010]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. Example 1 A non-woven film made of polyester (PS) having a thickness of 50 μm was used as a tape and a sheet for a leak inspection material, and a superimposed colored layer was formed on the tape and the sheet. 5% by weight of Nippon Ink Chemical Industry Co., Ltd. and normal heptane 5
0% by weight, 35% by weight of ethanol and 10% by weight of ethyl cellulose (trade name: “Ethocel”: Dow Chemical Co.) were stirred at 1500 RPM for 30 minutes using a stirrer,
The mixture sufficiently mixed and dispersed was uniformly applied to the film surface by spraying. The thickness of the dried coating film of the colored layer was 13 μm. Next, in order to superimpose a white layer on the colored layer, 15% by weight of fine silica powder (particle size: 1 to 3 μm), 20% by weight of fine magnesium carbonate powder (particle size: 1 to 5 μm) and fine powder of calcium carbonate were used. Powder (particle size 0.5-1.5 μm)
10% by weight of normal heptane 44% by weight and a dispersant (trade name "NONION OP-80R", manufactured by NOF Corporation) 1
% By weight and 10% by weight of an acrylic pressure-sensitive adhesive were stirred at 1500 RPM for 30 minutes using a stirrer, and the mixture was sufficiently mixed and dispersed, and was printed on the colored layer on the film surface by screen printing. The thickness of the dried coating film of the white layer was 30 μm.
A 10 cm wide sheet and a 2 cm wide tape were made from the obtained film-like leakage inspection material and used for leakage detection inspection.

The leak inspection is performed according to the following method and the following evaluation criteria.
The overall performance was evaluated by measuring the background color tone, the color tone of the bleeding at the defective portion, and the effect of condensation on the leakage discrimination. The results are shown in Table 1. The color of the leak was clearly indicated by a clear red color against a white background, and it was clearly confirmed.

[Leak Detection Inspection] Two holes having a diameter of 10 μmφ at the leaked portion of the welded part and a size of 250 mmφ × 2
A 10-liter stainless steel container (SUS304) having a size of 50 mm × 1 mm in thickness was used as a test body, and 9 liters of water was filled in the container, and the tape and sheet for leakage inspection material obtained above were welded to the container. The tape was adhered to the entire surface and, after being left for 1 hour, the leakage spot where coloring was instructed on the coating film surface of the tape and sheet for leakage inspection material was confirmed. [Evaluation Criteria] Leakage detection performance (judgment was made visually by five panelists): All five persons could easily confirm the leak location. Δ: 1 to 4 persons could confirm the leaked part. X: All five persons could not confirm the leak location. Overall performance evaluation criteria: good △: slightly poor ×: poor The presence or absence of expansion due to bleeding was visually checked after leaving the test piece having a leak defect for 10 minutes. The leak detection performance of dew condensation is performed by using a dew condensation environment tester.
After leaving the leak detection test object filled with cold water of 1 ° C. for 1 hour, a change in the color of the background was visually confirmed. Those that turned red due to condensation were considered to be affected.

[0013]

[Table 1]

The solvents described in Table 1 for the colored layer and the white layer are used when each layer is coated and formed. After the layers are formed, they dry and evaporate. It does not constitute an inspection material.

Example 2 The test pieces used in Example 1 were the same in the material of the tape and sheet used in Example 1, the thickness of the substrate, and the composition of the colored layer and the white layer on the film surface. After filling kerosene in place of water in the container, a tape and a sheet-like leakage inspection material were stuck on the entire welded portion of the container, and the leakage location was confirmed in the same manner as in Example 1. The color of the leak was clearly indicated by a clear red color against a white background, and it was clearly confirmed.

Example 3 The composition of the white layer on the film surface was the same as in Example 1 except that the material of the tape and sheet was changed from polyester (PS) to polyethylene (PE). 8% by weight of Shimla Brilliant Carmine 6B233S (manufactured by Dainippon Ink and Chemicals, Inc.), 45% by weight of normal heptane, 37% by weight of ethanol, and 10% by weight of an acrylic pressure-sensitive adhesive at 1500 RPM using a stirrer.
The mixture was stirred for 0 minutes, thoroughly mixed and dispersed, and uniformly applied by a spray. The thickness of the dried coating film of the colored layer was 18 μm. Next, the test piece used in Example 1 was filled with water in the container, and the tape and sheet-like leakage inspection material obtained in Example 3 were attached to the entire surface of the welded portion. Was confirmed. The overall performance was evaluated by measuring the leak detection performance, bleeding enlargement, background color tone, bleeding color tone of defective spots, and the effect of condensation on leakage discrimination. The results are shown in Table 1. The color of the leak was clearly indicated by a clear red color against a white background, and it was clearly confirmed.

Example 4 The test pieces used in Example 1 were the same in the material of the tape and sheet used in Example 3, the thickness of the substrate, and the composition of the white layer and the colored layer on the film surface. After filling kerosene in place of water in the container, a tape and a sheet-like leakage inspection material were stuck on the entire welded portion of the container, and the leakage location was confirmed in the same manner as in Example 1. The overall performance was evaluated by measuring the leak detection performance, bleeding enlargement, background color tone, bleeding color tone of defective spots, and the effect of condensation on leakage discrimination. The results are shown in Table 1. The color of the leak was clearly indicated by a clear red color against a white background, and it was clearly confirmed.

Example 5 The content of the coloring pigment in the coloring layer was 0.1% with respect to 13% by weight of the paste.
After leaking water into a container, which is a test body using the leak inspection material as small as 3% by weight (2.25% by weight by solvent removal) in Example 1, the leakage location was confirmed in the same manner as in Example 1. Done. The overall performance evaluation was good, but the coloring was slightly inferior.

Comparative Example 1 A test used in Example 1 using an aerosol type (trade name: "Tacetomoremil": manufactured by NOF CORPORATION) which is a commercially available water leak detecting agent containing a water-soluble dye. Water was filled in a container as a body, and a leakage test agent filled in a 450 cc aerosol can was applied over the entire welded portion at an application amount of 40 g / m ² , and after 1 hour standing, the leaked portion was confirmed. The overall performance was evaluated by measuring the leak detection performance, bleeding enlargement, background color tone, bleeding color tone of defective spots, and the effect of condensation on leakage discrimination. The results are shown in Table 1. The color of the leak was clearly indicated by a clear red color against a white background, and it was clearly confirmed. However, the influence of condensation on the leakage identification is that the background is colored by condensation, making it difficult to see the leak location.
The overall performance evaluation was also slightly inferior.

Comparative Example 2 Kerosene was used instead of water in the container used as the test sample used in Example 1 by using “Tacetomoremille” (trade name, manufactured by NOF Corporation) used in Comparative Example 1. After the tension was applied, the leakage was confirmed by the same test method as in Comparative Example 1. Leak detection performance, expansion due to bleeding, background color,
The influence of the color tone of the bleeding spots on the defect location and the effect of condensation on the leakage discrimination were measured, and the overall performance was evaluated. The results are shown in Table 1. Since the water-soluble dye did not dissolve in kerosene, the leaked portion did not show any color development instruction against a white background and could not be clearly confirmed.

Comparative Example 3 A leak test material was manufactured and inspected in the same manner as in Example 1 except that titanium oxide powder was used as the white inorganic fine powder of the white layer. Even if the white layer leaked, it did not become transparent and the detection performance was poor.

From Table 1, it can be seen that the leaked portions of all of Examples 1 to 5 of the present invention were clearly colored with a clear red color against a white background, and that the workability was good and the overall performance evaluation was good. . On the other hand, in Comparative Example 1 using a commercially available water-soluble dye, there was expansion due to bleeding in water. In addition, although the leak detection performance was good, there was an effect of leak discrimination due to dew condensation, and the overall performance evaluation was poor. Comparative Example 2
Did not develop color with respect to kerosene, could not identify the leak location, and was poor in overall performance evaluation. Comparative Example 3 used titanium oxide powder as the white inorganic fine powder of the white layer.
Even if the liquid leaked, the white layer did not become transparent and the leaked portion could not be detected.

[0023]

The present invention is a film-type leak inspection material characterized in that when it is wet with water or oil from a test body, that part develops a color and can be distinguished from other parts. Leaks and penetration defects can be easily found by simply and reliably detecting the water without adding a special agent or the like to the water and using no special machine or device. In addition, this method can sufficiently detect a leaking part even when the test piece is slightly condensed and wet. Also, if the leaking thing is a liquid,
There is an advantage that it can be used regardless of its type. Furthermore, since it is a film type, it is possible to perform a leak test simply by pasting it directly on the test object, and there is no fear of scattering of the medicine during use and contamination during post-processing.

[0024]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a leakage inspection material of the present invention.

FIG. 2 is a cross-sectional view showing another example of the leakage inspection material of the present invention.

[Explanation of symbols]

1 is a breathable film, 2 is a colored layer, 3 is a white layer, 4 is an adhesive layer, and 5 is a transparent film.

Claims (2)

[Claims] 1. A leak comprising a breathable film, a colored layer having a deep color tone provided on the breathable film, and a white layer provided on the colored layer, which becomes transparent when wet and becomes opaque when dried. Inspection material. 2. A leak inspection method, comprising applying the leak inspection material according to claim 1 to a surface of a test piece and detecting leaking liquid based on a change in color tone.