JP2020060474A - Alkali leak detection tape and alkaline fluid leak detection method - Google Patents

Abstract

To provide an alkali leakage detection tape capable of reducing labor and costs required for replacement, without deteriorating over a long period of time, even when used in piping or the like installed outside, and to provide an alkali fluid leakage detection method using the tape.SOLUTION: Provided is an alkali leakage detection tape obtained by adhering a copper compound being a pH indicating agent, on a nonwoven fabric being a substrate. The alkali leakage detection tape is configured to change colors when contacting an alkali fluid or gas. Leakage of an alkali fluid or gas can be detected by attaching this tape at a place where an alkali fluid or gas may leak. In the alkali leakage detection tape, the pH indicating agent hardly modifies due to UV light or the like, even when the tape is used outside, since the copper compound being an inorganic compound is used as the pH indicating agent. Accordingly, the tape does not have to be frequently replaced, thereby reducing labor and costs required for replacement.SELECTED DRAWING: None

Description

  The present invention relates to an alkali leak detection tape capable of detecting a leak of an alkaline (basic) liquid or gas by changing its color when touched, and an alkaline liquid or gas using the tape. And a method for detecting leakage of an alkaline fluid, which detects leakage of water.

  It is not preferable to release a strongly alkaline (alkaline having a pH above 11; the same applies below) liquid or gas to the environment because it causes chemical burns when touching a finger or the like and is biotoxic. For this reason, in a plant that handles such a strong alkaline fluid, it is important to prevent the strong alkaline fluid from leaking from the joints of the pipes, etc. is there. This is because the strong alkaline fluid often has corrosive properties, and if the initial leakage is overlooked, the corrosion may spread around the leakage location, leading to a larger-scale leakage.

  Conventionally, as a method for detecting the leak from the joint of the pipe, [1] an electrode is arranged at the joint, and the leaked liquid is leaked due to a change in conductivity caused by contact with the electrode. By the method of detecting (hereinafter sometimes referred to as "electromagnetic sensor method") or by applying a pH indicator to the [2] seam portion in advance and the leaked strong alkaline fluid comes into contact with the coating film. A method of visualizing the leakage by the discoloration of the pH indicator that occurs (hereinafter sometimes referred to as the "paint method"), or [3] a tape on which the pH indicator is fixed is wound around the seam in advance and the leakage strength is increased. A method of visualizing leakage by the discoloration of the pH indicator caused by the contact of the alkaline fluid with the tape (hereinafter, sometimes referred to as “tape method”) and the like have been proposed. Among them, the electromagnetic sensor method has a problem that it cannot be used for gas leak detection and that it requires a large cost because it is necessary to install electrodes at all joints. Further, if rain or the like is applied to the electrodes, it will be detected as leakage, and thus there is a problem that it cannot be used outdoors. On the other hand, in the paint method, it is very time-consuming to apply paint to all joints, and when applying paint to pipes installed outdoors, it is necessary to avoid rain when working. However, there is also a problem that it is difficult to set up a work schedule.

  In this respect, the tape method is excellent in that it can also be used for gas leak detection, is low in cost, and can be easily attached to piping installed outdoors. An example of the tape used in such a tape method is the detection tape described in Patent Document 1. As shown in FIG. 2 and the like of the same document, the detection tape 6 has a base material 9 coated with an adhesive 8. The base material 9 is made of a transparent plastic sheet such as soft polyvinyl chloride. Although the adhesive 8 is also transparent, the adhesive 8 is mixed and kneaded with a pH indicator, such as thymol blue or phenol red, which changes color when it comes into contact with a strongly alkaline fluid. As shown in FIG. 1 of the same document, if the detection tape 6 is attached to the side surface of the flange 2 in the pipe connecting portion (joint) of the pipe 1 (piping) with the adhesive 8 side facing inward. When the internal fluid 5 flowing in the pipe 1 leaks from the pipe connecting portion, the pH indicator in the portion in contact with the internal fluid 5 is discolored, and the discolored portion is visible from the outside through the transparent base material 9. It becomes a state. As a result, it is said that the leaked spot can be easily found by visual inspection.

JP, 60-093329, A

  However, since the detection tape 6 described in Patent Document 1 uses an organic pH indicator such as thymol blue or phenol red as a pH indicator, it may be exposed to ultraviolet rays, heat or moisture after a certain amount of time has passed since it was attached to the pipe. Therefore, there is a problem that the pH indicator is denatured and the normal discoloration reaction is not exhibited. In particular, when used in a pipe installed outdoors, there is a problem that the pH indicator is denatured within a short period of time due to the influence of ultraviolet rays and the like. For this reason, it is necessary to replace the detection tape 6 with a new one at regular intervals of a short period of about several months, resulting in increased maintenance labor and cost.

  In addition, since the base material 9 and the adhesive 8 of the detection tape 6 described in Patent Document 1 are transparent, the color that appears when the pH indicator touches the alkaline internal fluid 5 and the flange 2 When the color of the side surface of the pH indicator is similar to the color of the pH indicator, there is a problem that it is difficult to visually detect it even if the pH indicator changes color due to leakage. Therefore, when the detection tape 6 of the same document is attached, as described in the upper right column, page 7, line 7 to line 10 of the same document, the portion to which the detection tape 6 should be attached (see In FIG. 2 of the document, it is described that the discoloration of the pH indicator can be promptly found by previously painting the side surface of the flange 2 in white. However, if all the parts to which the detection tape 6 is to be attached are painted in white in advance, it may take a lot of time and effort.

  The present invention has been made to solve the above problems, even when used in a pipe or the like installed outdoors, it is unlikely that the pH indicator is denatured by ultraviolet rays, heat, humidity, etc., It is an object of the present invention to provide an alkali leak detection tape which can reduce the time and cost for replacement. It is also an object of the present invention to provide an alkali leak detection tape which makes it easy to visually find the leak location of the alkaline fluid. Further, it is an object of the present invention to provide a method for detecting the leakage of an alkaline fluid, which detects the leakage of an alkaline liquid or gas using this alkaline leakage detection tape.

  The above problems can be solved by providing an alkali leak detection tape in which a copper compound is attached to a non-woven fabric.

  The alkaline leak detection tape of the present invention uses a copper compound, which is an inorganic compound, as a pH indicator. Therefore, even when this tape is used for pipes installed outdoors, the pH indicator is difficult to denature due to ultraviolet rays, heat, humidity, etc., so long as no leakage of alkaline fluid occurs There is no need to replace it. As a result, the labor and cost of exchanging the alkali leak detection tape can be reduced. The alkali leak detection tape of the present invention is not limited to the use place for piping, and can be used at any place as long as the leak of the alkaline fluid can occur.

  In addition, the alkaline leak detection tape of the present invention makes it easy to visually find the leaking location of the alkaline fluid. This is because the alkaline leak detection tape of the present invention uses a non-woven fabric as a base material, and since such a non-woven fabric is usually opaque (including translucent), it occurs on the base material. This is because it is easy to visually confirm the discoloration of the pH indicator regardless of the color of the place where the alkali leak detection tape is attached. As will be described in detail later, the alkaline leak detection tape of the present invention is normally lightly colored (before contact with an alkaline liquid or gas. The same applies hereinafter) because of the attached copper compound. ~ It has a light green color, but when it comes into contact with an alkaline liquid or gas, it changes color from bright blue to purple or dark brown to black.

  In addition, when the alkali leak detection tape of the present invention is used for leak detection of an alkaline liquid, even if the leak occurs at a place such as the back side of the pipe that is difficult for the operator to see, the leak can be easily found. You can This is because the alkaline leak detection tape of the present invention uses a non-woven fabric as a base material, and therefore, when an alkaline liquid adheres to the tape, the liquid infiltrates to a relatively wide range in the tape due to a capillary phenomenon, Discoloration is occurring even at the infiltrated destination. Thereby, for example, when the alkali leakage detection tape is wound around the pipe and installed, even if leakage of the alkaline liquid occurs on the back side of the pipe, the liquid infiltrates the inside of the tape, and This is because the portion wound on the front side also causes discoloration, which can be easily visually recognized by the operator.

  Furthermore, when the alkaline leak detection tape of the present invention is used to detect the leak of an alkaline liquid, it is possible to make a person or the environment less dangerous even when the alkaline liquid leaks. This is because the nonwoven fabric used as the base material can absorb the leaked liquid to some extent, so it is possible to prevent the leaked alkaline liquid from dripping for a while from the start of the leak until the discovery. Because.

In the alkali leak detection tape of the present invention, the specific structure of the nonwoven fabric used as the base material is not particularly limited. However, the alkaline leak detection tape of the present invention is a non-woven fabric to which a copper compound that is a pH indicator is attached. If the specific surface area of the non-woven fabric is too small, a sufficient amount of the copper compound is attached to the non-woven fabric. May not be possible. Therefore, it is preferable that the nonwoven fabric has an average fiber diameter D _{f of the} fibers constituting the nonwoven fabric of 30 μm or less. This makes it possible to increase the specific surface area of the non-woven fabric and make it easier for the copper compound to adhere to the non-woven fabric.

  In the alkaline leak detection tape of the present invention, the amount of the copper compound attached to the nonwoven fabric that is the base material is not particularly limited, but if the amount of the copper compound is too small, the alkaline leak detection tape will be formed even when the alkaline fluid comes into contact. There is a risk that the color does not change sufficiently and the leakage of the alkaline fluid cannot be effectively visualized. Therefore, it is preferable that 30 mg or more of the copper compound is attached to 1 g of the nonwoven fabric.

  In the alkaline leak detection tape of the present invention, the copper compound attached to the non-woven fabric is not particularly limited in its specific composition as long as it is discolored when brought into contact with an alkaline fluid. Examples of such a copper compound include those containing basic copper carbonate, basic copper sulfate or copper hydroxide. The copper compound may be one kind of compound or a mixture of plural kinds of compounds.

  As described above, according to the present invention, even when used in a pipe or the like installed outdoors, the pH indicator is unlikely to be denatured by ultraviolet rays, heat, humidity, etc., and the labor and cost of replacement can be reduced. It is possible to provide an alkali leak detection tape capable of performing the above. Further, it becomes possible to provide an alkali leak detection tape which makes it easy to visually find the leak location of the alkaline fluid. Furthermore, it becomes possible to provide a leak detection method for an alkaline fluid, which detects a leak of an alkaline liquid or gas using this alkali leak detection tape.

  A preferred embodiment of the present invention will be described more specifically. The alkaline leak detection tape of the present invention is a non-woven fabric as a base material to which a copper compound as a pH indicator is attached. As will be described in detail later, this copper compound changes its color to a bluish or brownish color when exposed to an alkaline fluid. For this reason, if this alkaline leak detection tape is attached to the part where the alkaline fluid may leak (hereinafter sometimes referred to as the "detected part"), the alkaline fluid leaks from the detected part. At this time, the tape that has come into contact with the leaked liquid is discolored, and the leak can be easily detected.

  There is no particular limitation on how to attach the alkali leakage detection tape to the detected portion. For example, an adhesive portion having adhesiveness may be provided on one surface of the alkali leak detection tape, and the adhesive portion may be attached to the detected portion or its periphery. In this case, there is an advantage in that the shape of the detected portion does not matter (the alkali leak detection tape can be attached even to a wall surface or the like where there is no clue to wind or bind the tape). However, if you try to attach the alkali leak detection tape to the detected part with the adhesive part and the liquid, rust, sand dust, etc. adheres to the detected part, wipe the liquid etc. in advance and then detect the alkali leak. Since it is necessary to attach the tape, it may take time to attach the alkali leak detection tape. In addition, the adhesive part is usually formed by applying an adhesive to an alkali leak detection tape, etc., and such an adhesive is often an organic substance, so when the alkali leak detection tape is used outdoors. In some cases, the adhesive may be modified by ultraviolet rays or the like. In addition, when the alkaline fluid comes into contact with the adhesive due to leakage, the adhesive may be denatured. If the adhesive is denatured and its adhesiveness is reduced, the alkali leak detection tape may be peeled off from the detected portion, and leak may not be properly detected.

  Therefore, it is preferable that the alkali leak detection tape be attached to the detected portion by a method that does not use an adhesive. As such a method, for example, a method in which an alkali leak detection tape is tied around the detected portion with something like a string, or an alkali leak detection tape is wrapped around the detected portion, and the end of the tape is wrapped with a bag stopper. A method of fixing it to the tape itself with such a thing is also conceivable. However, in these methods, it is necessary to prepare a fixture such as a string or a metal fitting in addition to the alkali leak detection tape, which may complicate the work of attaching the alkali leak detection tape. For this reason, the alkali leakage detection tape is assumed to have self-adhesiveness (they adhere themselves to each other, but do not adhere to other substances. The same applies to the following.), And the alkali leakage detection tape is wound around the detected portion. It is preferable that the end of is adhered and fixed to the alkali leak detection tape itself. This allows the alkali leak detection tape to be attached to the detected portion without using a fixture.

  The method for giving self-adhesiveness to the alkali leak detection tape is not particularly limited. The self-adhesiveness may be chemical self-adhesiveness using urethane resin, etc., but if the self-adhesiveness is mechanical self-adhesiveness due to a fine catching structure, etc., it will not be exposed to ultraviolet rays or alkaline fluid. It is preferable because even if it is touched, the self-adhesiveness is not easily lost. Examples of a method for imparting such mechanical self-adhesiveness to an alkali leak detection tape include a method in which a non-woven fabric having a crimping property is used as a base material, or a fastener such as a surface fastener on at least one surface of the non-woven fabric as a base material Examples thereof include a method of providing a hook-shaped protrusion.

In the alkaline leak detection tape of the present invention, as described above, if the specific surface area of the non-woven fabric as the base material is too small, it may not be possible to adhere a sufficient amount of the copper compound to the non-woven fabric. Therefore, the average fiber diameter D _f of the fibers forming the nonwoven fabric is preferably 30 μm or less. The average fiber diameter D _f is more preferably 25 μm or less, further preferably 20 μm or less. On the other hand, if the fibers forming the non-woven fabric are too thin, it may be difficult to attach the copper compound to the non-woven fabric. Further, a special manufacturing technique is required to make the fibers constituting the non-woven fabric extremely thin, which may increase the manufacturing cost of the non-woven fabric. Therefore, the average fiber diameter D _f is usually set to 1 micrometer or more. The average fiber diameter D _f is more preferably 5 micrometers or more, further preferably 10 micrometers or more. In this embodiment, the average fiber diameter D _{f is set} to about 13 to 15 μm.

  The thickness of the non-woven fabric as the base material of the alkali leak detection tape is not particularly limited, but if the non-woven fabric is too thin, it may not be possible to adhere a sufficient amount of the copper compound to the non-woven fabric. Moreover, since the amount of leakable liquid that can be retained in the alkali leak detection tape is small, the leaked alkaline liquid may drip immediately, which may be harmful to people and the environment. Therefore, the thickness of the nonwoven fabric is preferably 0.5 mm or more, and more preferably 0.7 mm or more. On the other hand, if the thickness of the non-woven fabric is too thick, the leaking alkaline liquid slows down the speed of infiltration in the non-woven fabric in the lateral direction (direction substantially perpendicular to the thickness direction), making it difficult to detect the leak that occurred on the back side of the piping. There is a risk. Therefore, the thickness of the nonwoven fabric is preferably 5 mm or less, more preferably 3 mm or less. In this embodiment, the thickness of the nonwoven fabric is about 1 mm.

  The porosity of the non-woven fabric that is the base material of the alkali leak detection tape is not particularly limited, but if the porosity is too small (the non-woven fabric is too clogged), the amount of liquid leakage that can be retained in the tape will decrease, There is a possibility that the leaked liquid may easily drip immediately after the start of leakage. In addition, the leaked liquid may not easily infiltrate in the nonwoven fabric, and it may be difficult to find the leak that has occurred on the back side of the pipe. Therefore, the porosity of the nonwoven fabric is preferably 50% or more. The porosity of the nonwoven fabric is more preferably 70% or more, further preferably 90% or more. However, if the porosity of the non-woven fabric is too large (the mesh of the non-woven fabric is too coarse), it may be rather difficult to retain the liquid leakage in the tape. In addition, it may be difficult to visually recognize the discoloration of the alkali leak detection tape. Therefore, the porosity of the nonwoven fabric is preferably 97% or less. The porosity of the nonwoven fabric is more preferably 95% or less. In this embodiment, the non-woven fabric has a porosity of about 93%.

  The fibers constituting the non-woven fabric are not particularly limited in kind, and natural fibers (vegetable fibers such as cellulose fibers and animal fibers such as animal body hair) may be used, but if chemical fibers are used, It is preferable because the alkali resistance and weather resistance of the alkali leak detection tape can be improved. The chemical fibers are roughly classified into recycled fibers, semi-synthetic fibers and synthetic fibers. Among them, it is preferable to use synthetic fibers because the weather resistance of the alkali leak detection tape can be further improved. As the synthetic fiber, polyester fiber, polypropylene fiber, nylon fiber, aramid fiber, polyethylene fiber, polystyrene fiber, vinylon fiber, vinylidene fiber, polyvinyl chloride fiber, acrylic fiber, acrylic fiber, polyurethane fiber, polyclar fiber, fluorine fiber, Examples include novoloid fibers, polyetherester fibers, and polylactic acid fibers. As the synthetic fiber, a fiber obtained by spinning a mixture of plural kinds of synthetic resins may be adopted. As the fibers constituting the nonwoven fabric, only one type may be used, or a plurality of types may be used in combination. In this embodiment, a non-woven fabric made of polyester fiber is used as the base material of the alkali leak detection tape.

  The method for adhering the copper compound to the non-woven fabric as the base material is not particularly limited, and a general method used when adhering the compound or particles to the non-woven fabric can be adopted. As such a method, a copper compound formed in a microcrystalline form or a powder form (hereinafter sometimes simply referred to as “copper compound powder”) is fixed to a non-woven fabric by using a fixing agent (binder). Method, a method in which a turbid liquid containing copper compound powder is filtered with a non-woven fabric, and then the non-woven fabric is dried, or an aqueous solution containing copper ions is impregnated into the non-woven fabric, and the non-woven fabric is dried under specific atmospheric conditions. And a method in which the nonwoven fabric is immersed in an aqueous solution containing copper ions to deposit a copper compound on the surface of the nonwoven fabric, and then the nonwoven fabric is dried. When the non-woven fabric is composed of thermoplastic fibers, a method of kneading a powder of a copper compound into a raw material resin of the fiber in advance, or a copper compound with respect to a fiber surface immediately after extrusion molding the raw material resin into a fibrous shape It is also possible to employ a method of spraying the powder of No. 3, a method of heating the molded non-woven fabric to melt the resin on the fiber surface, sprinkling the powder of the copper compound on it, and then cooling.

  There is no particular limitation on how much copper compound is attached to the non-woven fabric that is the base material, but if the amount of copper compound attached is too small, the alkaline leak detection tape will not be exposed even when it comes into contact with an alkaline fluid. The color does not change sufficiently and there is a risk of overlooking the leak. Therefore, the amount of the copper compound attached to 1 g of the nonwoven fabric is preferably 30 mg or more. The amount of the copper compound attached to 1 g of the nonwoven fabric is more preferably 40 mg or more, further preferably 50 mg or more. Even if the amount of the copper compound attached is too large, there is no particular problem, but the amount of the copper compound attached to 1 g of the nonwoven fabric is usually 200 mg or less. In this embodiment, the amount of the copper compound attached to 1 g of the nonwoven fabric is about 50 to 150 mg.

  In the alkaline leak detection tape of the present invention, the copper compound attached to the nonwoven fabric as the base material is not particularly limited in its specific composition as long as it is discolored when brought into contact with an alkaline fluid. The copper compound may be one that is easily soluble in water, but in this case, when the alkali leak detection tape is used outdoors, there is a risk that the copper compound will fall off due to rain or the like. For this reason, it is preferable to employ a copper compound that is difficult to dissolve in water as the copper compound attached to the nonwoven fabric. Examples of such a copper compound include a basic copper compound, copper hydroxide, and copper oxide. Examples of the basic copper compound include basic copper carbonate, basic copper sulfate, basic copper chloride, and basic copper acetate. The copper compound may be used alone or in combination of two or more kinds. Also, so-called patina can be used as the copper compound. In this embodiment, the copper compound attached to the nonwoven fabric as the base material is a mixture of basic copper carbonate, basic copper sulfate, and copper hydroxide.

  As described above, the alkaline leak detection tape in which the mixture of the basic copper carbonate, the basic copper sulfate and the copper hydroxide is adhered to the non-woven fabric is light blue to light green in normal times. When this alkaline leak detection tape was brought into contact with various alkaline fluids, the following discoloration reaction was exhibited. That is, when the aqueous sodium hydroxide solution was brought into contact with the tape, the tape changed its color from dark blue to dark blue. It is considered that this is because copper (II) hydroxide was generated. When an excessively strong alkaline fluid was brought into contact with the tape, the tape might turn blue and then brown to black. This was because the reaction from copper (II) hydroxide to copper oxide proceeded. Is considered to be. On the other hand, when it was brought into contact with gaseous ammonia or an aqueous solution of ammonia salt, the tape changed its color from dark navy blue to ultramarine blue, and when it was contacted with ethylenediamine, the tape turned deep dark blue to purple. . It is considered that this is because amines and copper ions formed a complex. When the tape was contacted with sodium hypochlorite, the tape turned black. It is considered that this is because the copper ion was oxidized by the oxidizing power of sodium hypochlorite to generate copper oxide. These discoloration reactions hardly changed even after the alkali leak detection tape was left outdoors for one year or longer.

  The alkali leak detection tape of the present invention is not particularly limited in its use place, and can be used in any place as long as there is a possibility of leaking the alkaline fluid. Examples of such a place include a plant (factory) that handles an alkaline fluid. More specifically, in a plant that handles alkaline fluids, there are pipes for transporting alkaline fluids, tanks for storing or transporting alkaline fluids, reaction tanks and mixing vessels that use alkaline fluids therein, and the like. Can be mentioned. In particular, since the seam portion of these facilities is a place where the alkaline fluid easily leaks, it is suitable as a place to which the alkaline leak detection tape of the present invention is attached.

Claims (5)

An alkali leak detection tape with a copper compound attached to a non-woven fabric.
The alkali leak detection tape according to claim 1, wherein the fibers constituting the nonwoven fabric have an average fiber diameter D _f of 30 μm or less.
The alkali leakage detection tape according to claim 1, wherein 30 mg or more of the copper compound is attached to 1 g of the nonwoven fabric.
The alkali leak detection tape according to claim 1, wherein the copper compound contains basic copper carbonate, basic copper sulfate or copper hydroxide.
  An alkaline fluid leak detection method for detecting a leak of an alkaline liquid or gas using the alkaline leak detection tape according to claim 1.