JP2002002880A - Lining coated liquid storage tank, method for manufacturing the same and method for detecting flaw of lining layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid storage tank constituted so as to be capable of simply detecting the presence of the piercing flaw part of a lining layer causing the leaching or leakage of a stored liquid with respect to the liquid storage tank to which the lining layer is applied to apply the lining layer more simply at a low cost, and a method for detecting the flaw of the lining layer. SOLUTION: The electric insulating synthetic resin insulating substrate layer formed on the whole inner surface of the liquid storage tank, a conductive coating material layer containing a particulate conductive filler covering the insulating substrate layer and the embedded electrode embedded in the conductive coating material layer are provided and an electric insulating corrosion-resistant synthetic resin surface finish layer is provided on the conductive coating material layer and the lead wire of the embedded electrode is led out to the inside or outside of the tank and an electrode plate is provided to enable the detection of the piercing flaw of the surface finish layer. At the time of inspection, the tank is emptied, and the embedded electrode and an inspection electrode are connected to a resistance measuring instrument through conductors and the inspection electrode containing a conductive liquid is scanned on the surface of the finish layer left and right as well as up and down in this state to detect a position, where a resistance value is low, as the piercing flaw.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid storage tank provided with a lining layer, and more particularly, to a structure, a manufacturing method, and a defect detection method for the liquid storage tank capable of detecting penetrating defects or leakage of the lining layer. About the method.

[0002]

2. Description of the Related Art Various intermediates and wastewater by-produced in the course of various production activities such as the chemical industry, metal industry, and semiconductor manufacturing industry.
Liquid such as waste liquid is temporarily stored in a predetermined liquid storage tank during the process. This liquid storage tank is required to have effective liquid leakage blocking performance and corrosion resistance for the liquid to be stored, and therefore, a corrosion-resistant lining treatment is applied to the entire inner surface of the liquid storage tank. Many.

[0003] However, the lining layer on the inner surface of the liquid storage tank may be damaged due to imperfect construction during the lining process, deterioration of the material of the lining layer during operation of the liquid storage tank, or abrasion.
In some cases, penetrating defects such as pinholes and cracks leading to leakage of the liquid out of the tank were generated. Leakage of liquid from the reservoir will lead to contamination of the surrounding environment and must be monitored constantly, and such lining defects need to be repaired sequentially.

[0004] When the storage tank is constructed on the ground, the defect of the lining layer substantially coincides with the area where the stored liquid oozes or leaks on the outer peripheral surface of the storage tank.
The defective portion of the lining layer can be easily confirmed by directly visually observing the point, and the subsequent repair work was relatively easy.

On the other hand, in a storage tank of an underground buried type,
Defects in the lining layer lead to a direct cause of ground pollution due to leakage of stored liquids out of the tank, but the leakage site is below the ground and its existence is simple and low cost. The method of recognizing by has not been established yet.

With respect to the prior art, a method of detecting a penetrating defect generated in a lining layer applied to the inner surface of a liquid storage tank is disclosed in Japanese Utility Model Publication No. 63-39628. Leak detection systems have been proposed. In this system, an insulating synthetic resin lining is stuck on the inner surface of the tank body, and a plurality of small-area energizing clauses are spread over the entire surface of the synthetic resin lining, and are insulated from each other. Was coated with an insulating synthetic resin.

In this prior art, each energizing cloth is connected in parallel to one pole of a power source via a corresponding position display lamp, and is disposed on the inner bottom of the tank and in the peripheral wall of the tank body. The electrode plates are connected in parallel to the other pole of the power supply via corresponding indicator lights. When corrosion, cracks, etc. occur in the coating layer, lining layer, or tank body, the energizing close and the electrode plate are energized via waste liquid or other conductive storage liquid, and the position display lamp and indicator lamp are turned on. Thus, a defective portion such as a crack was recognized.

[0008]

This conventional detection method is excellent in that it attempts to accurately locate the penetrating defect itself in the lining layer in the tank, but from the viewpoint of the construction method. In particular, it is necessary to lay down a large number of electrical closes one by one while individually insulating small-sized current-carrying cloths one by one, and the electric wiring has an extremely complicated electric wiring circuit. The amount of work was large, and the work content was more complicated. Furthermore, if the tank size is large, the number of laid small area closes and the number of electrical wires will increase drastically, and the completion of the liquid storage tank involves practical disadvantages such as the number of processes, the construction period, and economic efficiency. .

In view of the problems in the prior art, the present invention can easily detect the presence of a penetrating defect in a lining layer that leads to seepage or leakage of stored liquids, and can make the lining layer simpler and more convenient. An object of the present invention is to provide a liquid storage tank which can be constructed at low cost, a method for manufacturing the same, and a method for detecting a lining layer defect of such a liquid storage tank.

[0010]

In the liquid storage tank of the present invention, the lining layer has an insulating resin base layer on the entire inner surface of the liquid storage tank main body and a conductive layer as a conductive layer applied on the entire base layer. It is composed of a coating material layer and a surface finishing layer applied on the upper surface of the conductive coating material layer, and the conductive coating material layer is used as an electrode for detecting a defect of the surface finishing layer.

In the present invention, the surface finishing layer is designed and constructed as a surface of the lining layer so as to be able to withstand direct contact with the drainage of the liquid storage tank and the like. Substantially the entire backside of the layer is provided with conductivity, and the conductive coating layer is further connected to a lead wire and taken out of the lining layer.

Defect detection of the surface finishing layer is measured with the storage tank empty, and a resistance measuring device is connected between the lead wire of the conductive coating material layer and a separate detection electrode. The surface of the surface finishing layer of the lining layer of the storage tank is partially wetted with a conductive liquid, and the surface of the separate electrode is scanned while being in contact therewith. This detection method uses a conductive coating material at the defect position if there is a penetrating defect such as a pinhole, a blowhole, a gap, a crack, or a crack penetrating the surface finish layer wetted with a liquid from front to back. The conductive liquid flows between the layer and the test electrode, and the resistance measuring device detects a relatively low resistance, so that a pinhole that is penetrating, a crack,
Recognize defects such as peeling and incision.

[0013] Such a lining structure is formed as follows. That is, a synthetic resin-based insulating base layer having electrical insulation performance is applied to the entire inner surface of the liquid storage tank main body, and a conductive filler is compounded in the insulating base layer forming region. This is achieved by applying a coating material layer and, in the next finishing step, applying a synthetic resin-based surface finishing layer having both corrosion resistance and electric insulation performance. Lead wires are appropriately connected to the conductive coating material, and are drawn in or out of the tank, particularly, to the upper part of the tank.

Further, it is preferable that a buried electrode is buried in the conductive coating material layer in advance, so that the lead wire can be reliably conducted to the conductive coating material layer via the buried electrode. it can. In this case, the required number of small planar electrodes to which the lead wires are connected is arranged at an arbitrary position on the formed insulating base layer and attached, and thereafter, the entire surface on the insulating base layer is formed. As described above, it is preferable to form a conductive coating material layer. By using a suitable small planar electrode as a buried electrode,
By using the electrode closest to the test position of the finished surface layer,
Penetration defects can be detected with high sensitivity.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The liquid storage tank of the present invention is used for a stationary tank on the ground, an underground type or a semi-underground type, and
In addition, the tank body includes concrete and steel. The following embodiment will be described with reference to FIG. 1 and FIG. 2 as an example of a liquid storage tank in which a concrete main body is fixed in a semi-underground type, but can also be applied to a floor-standing type.

The lining layer 50 of the present invention has at least three layers of an insulating underlayer 2, a conductive coating material layer 4, and a surface finishing layer 5 in order from the inside of the liquid storage tank main body 1. The conductive coating layer 4 to which the lead wire 30 is connected detects a penetrating defect in the finished layer. The insulating base layer 2 is applied to the reservoir body 1 in advance, and the base layer 2 insulates the conductive coating layer 4 from the tank body 1 and stabilizes the conductive coating layer 4 as a primer. To increase the adhesive strength of the conductive coating material layer 4. Such an insulating base layer is selected from insulating materials having a high electric resistance among conventional base materials and primer materials. For example, among resin materials, acrylic, epoxy, vinyl ester, polyurethane, etc. Is used. As a method of applying the insulating base layer 2, a conventional technique such as trowel coating, brush coating, or spray coating can be used.

The conductive coating material layer 4 contains a mixture of a resin base material and a conductive filler, and the resin base material is made of a non-solvent type thermosetting resin or a thermoplastic resin, or a solvent type resin liquid. Is done. Epoxy resin, unsaturated polyester resin, polyurethane resin and the like can be used as the thermosetting resin, and acrylic resin and the like can be used as the thermoplastic resin. Preferred examples of the resin substrate include an epoxy resin, a vinyl ester resin, a polyester resin, and a methacrylate resin.

As the conductive filler, metals, metal oxides,
Carbon is utilized and can be in the form of particles, flakes or fibers. Examples of the metal include nickel, stainless steel, and aluminum, and examples of the metal oxide include conductive oxides such as zinc oxide, tin oxide, and antimony oxide. As carbon, carbon black, graphite particles, carbon fiber, graphitized carbon fiber and the like can be used. The conductive filler also includes conductive fibers obtained by coating the surface of a tough fiber such as polyester fiber or glass fiber with a metal, for example, copper or nickel, and such a metal-coated fiber also has a conductive coating material. It is suitable for securing the conductivity of the layer and strengthening the material.

In particular, the conductive filler is a conductive coating material layer 4
From the viewpoint of ensuring the coating workability and the smoothness of the coating film, it is preferable that the shape is powdery, but in order to increase the strength and electrical conductivity, a conductive fibrous shape is convenient, for example, Carbon fibers and the above-mentioned metal-coated fibers can be used.

Preferred examples of such a conductive coating material include, for example, an epoxy urethane resin on a resin base material;
Solvent-type coating liquids in which conductive filler is combined with carbon black or conductive graphite are exemplified.

As a method of applying the conductive coating material, a very simple and rapid coating method such as trowel coating, brush hand coating, roller coating, spray coating and the like can be used. Therefore, it has very great advantages in terms of work efficiency and economy.

The finishing layer 5 used in the liquid storage tank of the present invention is a surface finishing layer 5 of a synthetic resin having chemical resistance and other corrosion resistance to liquid such as waste liquid held in the liquid storage tank. At the same time, it must be electrically insulating. Such a resin material therefore differs depending on the storage use of the liquid storage tank and the size and shape, and various resin materials are used.

In the conductive coating material tank, a lead wire connected to the conductive coating material is directly arranged, and the lead wire is raised in the lining layer 50 and preferably fixed inside or outside the tank. Connected to the terminal, the terminal is usually arranged on the bath.

In a preferred embodiment of the present invention, in particular, a desired number of small planar electrode plates are connected to the lead wires 30 as the embedded electrodes 3, and the electrode plates are embedded in the conductive coating material layer 4. The other end of the lead wire 30 is preferably fixed to the terminal 31 outside the bath. Small planar electrode plates typically include thin metal plates, metal nets, metal wool, and such electrode plates are formed, for example, from copper, aluminum, steel, and particularly stainless steel. The dimensions and thickness may be any suitable size that can be placed in the conductive coating material layer 4 and electrically contact the conductive coating material layer 4. For example, the buried electrode 3 may be a flexible electrode having a rectangular or circular plate having a side or diameter of about 10 mm to 200 mm and a thickness of 0.1 mm to 5 mm.

The buried electrode 3 is attached and temporarily attached to the insulating base layer 2 after completion of the insulating base layer 2,
A conductive coating material is applied so as to cover the electrode plate, and after curing, is integrated with the conductive coating material layer 4.

By burying preferably two or more buried electrodes in the conductive coating material layer 4 as described above, an electrode plate to be measured is appropriately selected and generated in the finishing layer 5 as described later. The detection sensitivity of the penetrating defect can be enhanced.
In particular, there is an advantage that the search efficiency for a minute defect such as a hair crack or a pinhole can be improved.

Regarding the method of inspecting the surface finishing layer 5 of the lining layer 50, if the surface of the surface finishing layer 5 is appropriately wetted with a conductive liquid such as conductive water or an aqueous electrolyte solution and a defect penetrating therethrough exists, The conductive liquid selectively passes through only the defective portions of the surface finishing layer 5 and reaches the lower conductive coating material layer 4 to be in an electrically conductive state. Therefore,
If the electrical resistance between the wetted surface and the conductive coating layer is measured, the resistance is lower than the other defect-free surface portions.

In the method for detecting a penetrating defect according to the present invention, the embedded electrode 3 and the separate movable inspection electrode 6 are connected to a resistance measuring instrument, and the desired coating of the surface finishing layer 5 of the lining layer 50 is performed. The test site is wetted with the conductive liquid and the test electrode 6 is brought into contact with the wetting solution of the test site. Is detected. Such an inspection electrode 6 has an advantage that a water-absorbing electrode impregnated with a conductive liquid in advance is simple and easy to use.

In this detection method, if the wetted surface of the surface finishing layer 5 does not have a defect penetrating between the front and back surfaces of the surface finishing layer 5, the resistance value remains relatively high. If there is a penetrating defect such as a crack on the wetted surface of the surface finishing layer 5, the resistance value is relatively lowered, and it is found that the defect is penetrating, and the portion needs to be repaired. You can see that.

This change in the electric resistance value is obtained by keeping the copper wire 63 from the lead wire 30 derived from the buried electrode 3, for example, a small planar electrode, and the copper wire 62 of the inspection electrode 6 connected to the resistance measuring device. When the inspection electrode 6 containing the conductive liquid is scanned right and left and up and down on the surface of the finishing layer 5, if a position having a low resistance value can be detected, a penetrating defect such as a crack 52
It turns out that there is a high possibility of the presence of the slab, and it is subject to repair.

In actual inspection, conductive liquids include:
The conductive water may be ordinary tap water, and the electrolyte aqueous solution may be simply a saline solution or the like. A simple example of a water-absorbing electrode as the test electrode 6 may be one in which the above-mentioned tap water or saline is impregnated or moistened into a water-absorbable fabric such as a suitable woven or non-woven fabric to which a lead wire is connected.

In another detection method, as the buried electrode 3 in the conductive coating material layer 4, the number of small planar electrode plates is appropriately arranged according to the shape of the liquid storage tank. From the change in the resistance value between the storage liquid W and each of the buried electrodes 3, it is predicted that a penetrating defect, for example, a crack exists in the finishing layer 5 near the buried electrode 3 having a low resistance value. You.

If the liquid storage tank has, for example, a rectangular shape, it is possible to easily and reliably determine the surface on which a defect has occurred simply by disposing it in the conductive coating material layer having only the four inner wall surfaces and the bottom surface. It can be restored by applying lining repair to this surface. Thus, the method of the present invention
This eliminates the complexity of the related art, such as complicated electric lines and various connections.

In the method using the liquid storage, it is possible to easily detect cracks in the liquid storage tank while the liquid storage is in operation. The inspection is preferably performed on the tank by scanning the inner wall surface of the inspection electrode 6 described above.

The method of the present invention can be applied to finishing inspection immediately after assembling a new storage tank and finishing the lining. Further, the storage tank is already in operation and is internally stored for the purpose of periodic inspection. Inspection can be performed arbitrarily even at a stage immediately after the liquid is discharged. In this case, since the defective portion has already been wet with the stored liquid for a long time, the work of again wetting the surface of the surface finishing layer with the conductive liquid can be omitted, which is rather convenient for detection.

[0036]

EXAMPLES (Example 1) The liquid storage tank main body 1 was made of concrete and was a semi-underground type having an internal volume of 4.5 m ³ . A primer made of a polyurethane resin was spray-coated on the inner surface of the liquid storage tank main body 1 as an insulating base layer 2 of a synthetic resin, and after drying, a coating material made of a polyester resin was spray-coated and a glass mat was attached. .

Next, a small copper electrode plate (100.times.100) to which lead wires are connected as buried electrodes 6 at appropriate positions on the four side surfaces and the bottom surface of the liquid storage tank main body 1 on the insulating base layer 2.
(100 mm square, 0.2 mm thick). The following conductive coating material was applied by roller coating so as to completely cover the insulating base layer 2 and the buried electrode 3 with the lead wire drawn out into the inner space of the liquid storage tank main body 1.

The composition of the conductive coating material is summarized in Table 1. In this example, a solvent-based resin was used as the resin, and a carbon-based powder was compounded as a conductive filler. Specifically, as shown in Table 1, the resin component is an epoxy urethane composed of an urethane prepolymer and an epoxy polyol that also serves as a curing agent, and the conductive filler is graphite and carbon black (both powder having a size of 10 μm or less). Was used, and a phosphoric acid ester surfactant was added as a dispersant and xylene was added as a solvent to prepare a coating material.

[0039]

[Table 1]

After the conductive coating material was dried and cured, a surface finishing layer 5 was applied over the entire surface to complete a liquid storage tank. The finishing material was spray-coated with a coating liquid composed of a vinyl ester resin, and a glass mat was stuck thereon. Then, a surface layer composed of a coloring pigment and a vinyl ester resin was formed. The working area of this example was about 10 m ² , and only a small number of small planar electrodes were stuck, so it was completed in 12 hours.

A crack detection test was performed on the lining layer 50 formed on the inner wall as described above. A copper wire is connected to the separate test electrode 6 to a cloth wetted by absorbing a conductive liquid, and the terminal of the buried electrode 3 and the copper wire of the test electrode 6 are connected to a resistance measuring instrument. In a wet state, the inspection electrode 6 was moved on the wall surface while being pressed against the surface of the lining layer 50 on the inner wall, and a change in resistance was monitored. In the normal sound inner wall lining surface, the resistance value showed a high value of 10 to 20 MΩ, but in the small crack portion of the lining surface, it showed a low resistance value of 40 to 200 kΩ, and penetrated the front and back of the lining layer 50. It was determined to be cracked.

[0042]

According to the liquid storage tank of the present invention, the base layer and the surface finishing layer on the inner surface side of the liquid storage tank main body are insulated, and a conductive coating material layer containing a conductive filler is interposed between the two layers. So
By measuring the electric resistance between the conductive coating material layer and the lining surface layer, it is possible to easily and inexpensively realize a liquid storage tank capable of easily detecting penetrating defects in the surface finishing layer. Furthermore, if a small electrode is buried in the conductive coating material layer as the buried electrode and its lead wire is fixed on the tank, the connection to the conductive coating material layer can be surely made, and at the same time, the buried electrode By arranging a plurality of small electrodes, the accuracy of detecting the position of a defect in the surface finishing layer can be improved.

According to the method for manufacturing a liquid storage tank of the present invention, a synthetic conductive resin coating containing a conductive filler is applied to the entire inner surface of the liquid storage tank main body after an insulating base layer is applied and before the surface finishing layer is applied. Simply by coating with a material layer, simply measuring the electrical resistance between the conductive coating material layer and the lining surface layer, a liquid storage tank that can easily detect penetrating defects in the surface finishing layer, And it can be manufactured at low cost. Furthermore, simply by embedding the embedded electrode in the resin coating layer, the lead wire is led out of the tank or out of the tank, and the embedded electrode can be used for detection of cracking defects in the surface finish layer, and the conductivity of the lead wire If the connection to the conductive coating material layer is made surely and a plurality of small electrodes are arranged at the same time as the buried electrode, the detection accuracy of the defect position of the surface finishing layer can be improved.

The method for detecting penetrable defects in a liquid storage tank according to the present invention comprises the steps of: connecting a lead wire connected to a conductive coating material layer or a buried electrode of the liquid storage tank to a separate movable inspection electrode; By connecting to the surface of the lining layer, the desired inspection site on the surface of the lining layer is wetted with the conductive liquid and the inspection electrode is scanned, so that penetrating defects such as cracks in the surface finishing layer can be easily and reliably detected. Moreover, there is an advantage that there is no need to apply a special device or a complicated electric circuit.

[Brief description of the drawings]

FIG. 1 shows a longitudinal section of a liquid storage tank according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional perspective view of the inside of the liquid storage tank for describing the implementation of the method for detecting a defect in the liquid storage tank of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tank main body 2 Insulating base layer 3 Buried electrode 30 Lead wire 31 Terminal 4 Conductive coating material layer 5 Surface finishing layer 50 Lining layer 52 Defect of surface finishing layer 6 Inspection electrode 60 Resistance meter

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Mitsuo Sueoka, Inventor, Chugai Shoko Co., Ltd., 1-5-14, Utsuhoncho, Nishi-ku, Osaka-shi, Osaka, Japan 6 Kyocera Corporation Shiga Plant Yokaichi block F term (reference) 2G067 AA02 AA09 BB13 CC01 DD23 EE08 3E070 AA02 AB08 BA01 CA16 CB20 DA01 DA02 MA02

Claims (8)

[Claims] An insulating base layer including a synthetic resin formed on the entire inner surface of the liquid storage tank main body; a conductive coating material layer formed of a conductive filler and a synthetic resin covering the insulating base layer; A lead wire connected to the coating material layer and led out into or out of the tank, and a surface finishing layer containing an electrically insulating synthetic resin covering the conductive coating material layer, wherein the conductive coating material A lining-coated storage tank characterized in that the layer is used as an electrode for detecting penetrating defects in the surface finishing layer. 2. The liquid storage tank according to claim 1, wherein the conductive filler contains one or more selected from a metal, a conductive metal oxide, and carbon. 3. A buried electrode is buried in an arbitrary position in the conductive coating material layer, one end of the lead wire is connected to the buried electrode, and the other end is arranged outside the liquid storage tank. The liquid storage tank according to claim 1, wherein: 4. An insulating base layer containing a synthetic resin is coated on the entire inner surface of the liquid storage tank main body, and the insulating base layer is coated with a conductive coating material layer made of a conductive filler and a synthetic resin. Next, a surface finishing layer containing an electrically insulating synthetic resin is coated on the conductive coating material layer to form a lining layer, and the lead wire connected to the conductive coating material layer is placed in the tank. Alternatively, a method for manufacturing a lining-coated liquid storage tank, wherein the liquid storage tank is led out of the tank and the conductive coating material layer can be used as an electrode for detecting a penetrating defect of the surface finishing layer. 5. The method according to claim 4, wherein the conductive filler contains one or more selected from metals, conductive metal oxides and carbon. 6. After covering the insulating base layer, a conductive buried electrode to which the lead wire is connected is arranged and attached to an arbitrary position on the insulating base layer, The method according to claim 4, wherein the conductive coating material layer is coated. 7. The liquid storage tank according to claim 1, wherein the lead wire and a separate movable inspection electrode are connected to a resistance measuring instrument, and the surface of the surface finishing layer is connected to a resistance measuring instrument. A desired inspection site is wetted with a conductive liquid and the inspection electrode is brought into contact with the wetting solution of the inspection site, and a resistance measuring device detects a penetrating defect of the surface finish layer due to a change in resistance between the inspection electrode and the buried electrode. Defect detection method of the storage tank to be detected. 8. The detection method according to claim 7, wherein the test electrode is a water-absorbing electrode impregnated with a conductive liquid in advance.