JP2004286521A - Leakage sensor of conductive liquid substance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve durability, to prevent erroneous operation, and to secure required detection sensitivity. <P>SOLUTION: In a leakage sensor of a conductive liquid substance, a metal conductor 28 is inserted into a row of a number of electrically insulated cylindrical insulators 24 that are made of heat-resistant/corrosion-resistant substance and have a conductor insertion hole 26 at the center, and the outer periphery of the row of insulators is surrounded by a metal coil 30 to compose a sensor body 20. By detecting a change in electrical resistance between the conductor and the coil, the presence or absence of the leakage of the conductive liquid substance is detected. The shape of the insulators is optional, only the cylindrical insulators may be arranged, or two types, namely the cylindrical insulators and spherical insulators having an outer diameter being larger than the inner diameter, may be arranged alternately. A through-hole that has a size for allowing the conductive liquid substance to fully enter and reaches the inner periphery surface from the outer periphery surface is preferably formed on the side of the cylindrical insulators. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a leak sensor for detecting a liquid material having conductivity, and more specifically, to improve durability by making a metal coil surround the outer periphery of a large number of insulator rows holding a core wire. The present invention relates to a conductive liquid material leakage sensor that prevents malfunction. This technique is not particularly limited, but is useful for leak detection in, for example, a material corrosion test apparatus using a liquid metal or a molten metal compound.
[0002]
[Prior art]
In a device holding various liquids, it is often necessary to quickly and surely detect when a liquid leaks from a container or the like. If the liquid used has conductivity, a leak sensor utilizing the property can be constructed. One example of the prior art is shown in FIG. In this leak sensor, a metal core wire 12 is inserted into a row of a large number of electrically insulating insulators 10 having a core wire insertion hole at the center, and a metal braided tube 14 surrounds the row of insulators. Is composed. Here, the insulator 10 has a short cylindrical shape. The braided tube 14 is formed by knitting the whole into a tube shape using a thin metal wire. The principle of operation of the leak detection is that if a leaked substance (conductive liquid material) adheres between the core wire and the braided tube, the electrical resistance between the core wire and the braided tube (that is, ground) changes. By detecting, the presence or absence of leakage is detected.
[0003]
Such a leak sensor in the form of a coaxial cable is usually laid in a meandering shape outside the container or the like holding the conductive liquid substance so as to cover the entire bottom.
[0004]
[Problems to be solved by the invention]
However, the conventional leak sensor has a problem that a malfunction is liable to occur, depending on a use state and a use environment, such that a leak detection signal is generated even though no leak actually occurs. Braided tubes are excellent in flexibility and tensile strength, but when used at high temperatures, repeated damage due to thermal expansion and contraction due to temperature changes and deterioration due to high-temperature oxidation are severe, so the thin metal wires that make up the braided tubes are broken. And fuzzing due to surface oxides. The cause of the malfunction is that the fluffy thin metal wires come into contact with the core wire and short-circuit (see a portion surrounded by a symbol X in FIG. 7).
[0005]
Further, in the conventional leak sensor, when the leaked material has a property of rapidly solidifying, particularly when the leak amount is small, the leaked material may be blocked by the braided tube and solidified as it is. Then, since the leaked substance does not penetrate to the core wire, leak detection cannot be performed. As described above, there is also a problem that the detection cannot be performed or the detection sensitivity is lowered depending on the properties of the conductive liquid substance to be detected and the state of the leakage.
[0006]
An object of the present invention is to provide a conductive liquid substance leakage sensor which has excellent durability, can prevent malfunction, and has good detection sensitivity.
[0007]
[Means for Solving the Problems]
The present invention provides a structure in which a metal core wire is inserted into a row of a large number of electrically insulating insulators made of a heat-resistant and corrosion-resistant substance and having a core wire insertion hole at the center, and the outer periphery of the insulator row is surrounded by a metal protection member. In a sensor that has a sensor main body and detects a leak of a conductive liquid material by detecting a change in electric resistance between a core wire and a protective member, the use of a coil as a protective member surrounding the outer periphery of the insulator row is considered. It is a leakage sensor of a conductive liquid material which is a feature.
[0008]
Here, the specific shape of the insulator is arbitrary, but is assumed to be a short tubular shape (typically a cylindrical shape), and a large number of tubular insulators having the same shape or different shapes are arranged in a line. Alternatively, a cylindrical insulator and a spherical insulator having an outer diameter larger than the inner diameter of the cylindrical insulator may be alternately arranged. In these, it is preferable to form a through hole in the side surface of the cylindrical insulator, the through hole having a size that allows the conductive liquid material to sufficiently penetrate and extending from the outer peripheral surface to the inner peripheral surface.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is an explanatory diagram showing one embodiment of a leak sensor according to the present invention. This leak sensor comprises a sensor body 20 and connecting portions 22 located at both ends thereof. This is a leak sensor for a conductive liquid material, which is particularly suitable for use in an environment having a high temperature in the atmosphere (for example, 700 to 900 ° C.). The sensor main body 20 is a part that functions as a sensor, and the connection part 22 is a part that connects the sensor main body to external wiring.
[0010]
In this embodiment, the sensor main body 20 has a large number of cylindrical insulators 24 of the same shape having electrical insulation arranged in a line, and a metal core 28 is inserted into a core insertion hole 26 formed at the center thereof. In addition, the outer periphery of the row composed of a large number of cylindrical insulators 24 is surrounded by a metal coil 30. FIG. 2 shows the detailed structure and the bending state.
[0011]
The cylindrical insulator 24 is made of a heat and corrosion resistant material such as a ceramic material (for example, alumina or steatite). It is preferable that the inner diameter of the cylindrical insulator 24 is a dimension that allows the core wire 28 to be inserted with a margin, and the outer diameter and the length dimension are also determined according to the wire diameter of the core wire used. Since the ceramic material hardly deforms, the degree of freedom of bending of the sensor main body 20 becomes poor when the dimension in the axial direction increases. Therefore, when it is necessary to bend and attach with a small curvature, a large number is arranged in a short shape so as not to be in close contact with each other but to have a slight gap. The cylindrical insulators may be arranged by combining a plurality of types having different lengths. In addition, when the sensor main body is bent, adjacent insulators rub against each other. Therefore, it is preferable to perform chamfering or rounding on peripheral portions of both end surfaces of the insulator.
[0012]
The core wire 28 may be a copper wire, but a heat-resistant metal wire (here, a nickel wire) is used in order to minimize material deterioration due to oxidation. The wire diameter is determined according to the installation conditions and strength of the leak sensor. For example, in the case of bending and setting in a narrow space with a small curvature, the smaller the wire diameter is, the easier it is to lay. However, when the diameter is extremely small, the strength and durability are poor. In such a case, a wire diameter of about 1 mm having high flexibility (flexibility) is suitable. In addition, by increasing the wire diameter, deterioration due to repeated damage and high-temperature oxidation can be suppressed, so that the wire diameter can be set to 2 to 3 mm when bending flexibility is not required. Therefore, in general, it is appropriately determined from the range of about 0.5 to 3 mm in consideration of use conditions and use environment (freedom of installation, strength, durability, and the like).
[0013]
The coil 30 is formed by spirally winding a wire made of a material having excellent heat resistance and oxidation resistance such as stainless steel and capable of securing necessary strength. It is desirable that the coil outer diameter has a space capable of protecting the inner insulator 24 and securing freedom against deformation such as bending (no friction with the insulator when bent). It is preferable to set it to about double (gap about 1 to 2 mm). The coil pitch is set so that a conductive liquid substance as a detection target can enter the inside of the coil. When the leaked material does not solidify and has high fluidity, the gap between the coils may be almost nonexistent. This is because even if the coil has no gap in a natural state, a certain gap is naturally generated by being bent at the time of laying. Therefore, the drawings are drawn in a natural state without any gaps for convenience. In general, a coil having a gap of about 0.5 to 1 mm is preferable, although it depends on the properties of the leaked substance. In FIG. 2, the coil is drawn very sparsely at the bent portion (extending the gap between the coils very wide) for the sake of simplicity.
[0014]
The structure of the connecting portions 22 located at both ends of the sensor main body 20 is as follows. The end of the core wire 28 is led to the outside via a lead wire 32 provided with an insulating coating 31 (covered with rubber or the like). The lead wire 32 is made of a metal wire having low electric resistance (such as copper or aluminum), and the lead wire 32 and the core wire 28 are connected by press-fitting a butt sleeve 34. Therefore, the butting sleeve 34 is made of copper or the like having good crimpability. The vicinity of the end of the insulator row is protected by covering with a tube 36 made of stainless steel. A stainless steel adapter 38 is placed over the outer periphery of the connection between the lead wire 32 and the core wire 28 by the butt sleeve 34, and is fixed with epoxy resin. Further, a stainless steel collar 40 is provided on the outermost periphery thereof, and the both ends thereof are joined to the adapter 38 and the coil 30 by welding or the like to protect the internal structure. The core wire 28 and the lead wire 32 are insulated by an insulator and epoxy resin so that a malfunction does not occur due to a short circuit between the adapter 38, the tube 36, and the collar 40.
[0015]
The principle of operation of this leak sensor is basically the same as in the prior art. That is, if a leaked substance adheres between the core wire 28 and the coil 30, the electric resistance between the core wire 28 and the coil 30 (that is, the ground) changes. Therefore, the presence or absence of leakage is detected by detecting the change in the electric resistance. It is to do. Therefore, the leak sensor is laid outside the container or the like holding the conductive liquid material in a meandering shape so as to cover the entire bottom. In this leak sensor, even when the sensor main body 20 is bent, the coil 30 has good followability, can be bent without plastic deformation, and deterioration of the bent portion can be suppressed. In addition, the use of the coil 30 does not cause fluffing due to deterioration unlike a conventional braided tube, so that a malfunction due to a short circuit does not occur. Further, by adjusting the coil pitch, it is possible to ensure the permeability of the leaked substance into the core wire, and the leak detection sensitivity is improved.
[0016]
FIG. 3 is an explanatory view showing another embodiment of the leak sensor according to the present invention. This leak sensor also uses a coil as a protection member on the outer periphery, and the basic configuration is the same as that in FIG. 1 described above. Therefore, corresponding members are denoted by the same reference numerals, and detailed description thereof will be omitted. . FIG. 4 shows details of the insulator portion, and FIG. 5 shows a bent state of the sensor main body portion.
[0017]
In this embodiment, two types of insulators, a cylindrical insulator 50 and a spherical insulator 52 having an outer diameter larger than the inner diameter of the cylindrical insulator 50, are used and arranged alternately. FIG. 4A shows a combined state of the cylindrical insulator 50 and the spherical insulator 52 (however, they are drawn apart for easy understanding of the drawing), and FIG. 3 shows details of the spherical insulator 52, respectively. The core wire 28 is inserted into a core wire insertion hole 54 formed in the center of the cylindrical insulator 50 and a core wire insertion hole 56 formed in the spherical insulator 52. As described above, a ceramic material is optimal as the insulator material from the viewpoints of heat resistance, corrosion resistance to leaked substances, and electrical insulation.
[0018]
However, since the ceramic-based material is hardly deformed, short cylindrical insulators are arranged on the covering of the core wire 28, but a gap is formed between the cylindrical insulators at the bent portion. If the gap is too large, the coil may contact the core wire. Therefore, in this embodiment, both end surfaces of the cylindrical insulator 50 are machined into concave surfaces 51 corresponding to the spherical shape of the spherical insulator 52. By interposing the spherical insulator 52 between such cylindrical insulators 50, as shown in FIG. 5, when the sensor main body 20 is bent, a large gap is not formed between the insulators, and the coil 30 is connected to the core wire. 28 is reliably prevented.
[0019]
However, if the structure is such that no gap is formed between the insulators, or if the gap is made extremely small, the leaked substance will not reach the core wire and the function as a leak sensor will not be fully exhibited, It is also expected that it takes a long time to reach the core wire and the sensitivity is deteriorated. Therefore, in such a case, a through hole 58 extending from the outer peripheral side to the inner peripheral side is provided on the side surface of the cylindrical insulator 50. The number of the through holes 58 formed is arbitrary. The size of the through hole 58 may be a size that allows the leaked substance to easily enter. A through hole may be provided in the spherical insulator, but from the viewpoint of ease of manufacture, etc., it is preferable to form the through hole so as to cross between the facing outer peripheral surfaces of the cylindrical insulator. It is. By providing the through hole 58 on the side surface of the insulator, unnecessary contact between the coil 30 and the core wire 28 can be prevented, and leakage material can easily enter the core wire 28.
[0020]
FIG. 6 shows an example of a use state of such a leak sensor. A represents a longitudinal section, and B represents a plane (between Y _{1 and} Y ₂ ). This is an example of application to a material corrosion test device. This device has a double structure of a flanged inner container 62 holding a test melt and an outer container 64 surrounding the inner container 62. A lid 66 is attached to a flange portion of the outer container 64 via an O-ring 68. It is mounted and can be sealed by tightening with a plurality of bolts 70. In addition, the inner container 62 with a flange is held in a state of being placed on the convex portion 65 inside the flange portion of the outer container 64. A test melt 72 (here, a sodium compound reagent melt) is stored in the inner container 62 with a flange, and a test piece 74 is immersed in the test melt. The test piece 74 is held by a test piece holder 76, and the test piece holder 76 is suspended from the lid 66. In addition, a stirrer 78 and a thermocouple 80 are provided. An electric heater 82 is installed outside the outer container 64 from the side to the bottom.
[0021]
In such a material corrosion test apparatus, the leak sensor 84 is laid on the inner side surface, particularly the bottom surface, of the outer container 64 as widely as possible over a wide range. Specifically, as shown in FIG. 6B, a meandering meandering shape is provided on the bottom surface, symmetrically arranged, and fixed by spot welding. Of course, a spiral shape or the like may be used. The connection part of the leak sensor 84 is connected to the terminal part 86 and led to the control panel 88 by wiring. If the inner and outer container structure is doubled as described above, even if the test melt 72 leaks from the inner container 62 with the flange, it can be received by the outer container 64. The occurrence of the leak is immediately detected by the leak sensor 84. , And can be notified from the control panel 88 as a leak warning.
[0022]
The present invention relates to various liquid metals (pure metals such as Li, Na, K, Hg, Pb, Bi and alloys thereof) or compounds thereof (LiOH, NaOH, Na ₂ O, Na ₂ O ₂ , NaCl, etc.). It is suitable for detecting leakage of various ionic solutions (HNO ₃ , HCl, H ₂ SO ₄ , CH ₃ COOH, etc.).
[0023]
【Example】
A temperature cycle test was performed using the product of the present invention and the comparative product. The product of the present invention has the structure shown in FIG. 1, and the comparative product has the sensor body of the conventional structure shown in FIG. The materials and dimensions are as follows.
(1) Core wire of the product of the present invention ... Material: Nickel material, wire diameter = 1 mm
Cylindrical insulator: Material: alumina (99.7% by mass Al ₂ O ₃ ), outer diameter = 3 mm, inner diameter = 1.6 mm, length 5 mm
Coil: Material: stainless steel (SUS304), coil outer diameter = 5 mm, wire diameter = 0.3 mm, coil gap ≒ 0 mm, length = 1900 mm
(2) Comparative core wire: Material: Nickel material, wire diameter = 1 mm
Cylindrical insulator: Material: steatite (60 mass% SiO ₂ , 30 mass% MgO), outer diameter = 3.2 mm, inner diameter 1.5 mm, length 3.2 mm
Braided tube ... Material: Stainless steel (SUS304), outer diameter = 8.2mm, fine wire diameter = 0.12mm, length = 1900mm
[0024]
Such a leak sensor was incorporated in a material corrosion test apparatus shown in FIG. 6, and a temperature cycle test was performed. The temperature cycle is to raise the heater temperature to 700 to 900 ° C over 2 to 3 hours, hold at a constant temperature of 700 to 900 ° C for about 1 hour for immersion of the test piece, and then let it naturally reach room temperature over 24 hours. Cooling is a typical pattern. Three such temperature cycling tests were performed. As the reagent, a mixed reagent of sodium hydroxide and sodium peroxide (twice) and a mixed reagent of sodium hydroxide and sodium oxide (one time) were used.
[0025]
As a result of observation after the end of the test, in the product of the present invention, the coil surface was covered with the oxide film, but no damage such as breakage or deformation was found on the coil or the insulator. On the other hand, in the comparative product having the conventional structure, the braided tube was partially deformed and fuzzed by the oxide.
[0026]
When the temperature cycle test was performed 20 times, the leak alarm was activated at the 20th time for the comparative product. However, no trace of reagent leakage was observed, and it was found that the operation was malfunctioning. In contrast, no malfunction occurred in the product of the present invention. As a result of observing the malfunctioning comparative product in detail, it was found that the braided tube covering the insulator was cut and fuzzed over almost the entire length of the braided tube. In addition, cracks occurred in the insulator made of steatite due to a chemical change due to the temperature cycle and the adhesion of sodium compound vapor (such as sodium hydroxide) that had entered the outer container.
[0027]
【The invention's effect】
As described above, the leak sensor according to the present invention has a structure in which a metal coil is used as a protection member on the outer periphery of the insulator row. As described above, the thin wires are not cut or fluffed, the durability is improved, malfunctions can be prevented, and the reliability is significantly improved. Further, labor and cost required for maintenance such as replacement and inspection can be saved.
[0028]
Also, by setting the coil pitch (coil gap) appropriately, sufficient permeability of the leaked substance (conductive liquid substance) can be ensured, so that even liquids such as liquid metal which are easily solidified can be detected. There is no danger that the sensitivity will drop. Further, since the bending flexibility is good, it is not difficult to lay the meandering shape.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing one embodiment of a leak sensor according to the present invention.
FIG. 2 is an enlarged explanatory view of a bent state of the sensor main body.
FIG. 3 is an explanatory view showing another embodiment of the leak sensor according to the present invention.
FIG. 4 is an enlarged explanatory view of the insulator portion.
FIG. 5 is an enlarged explanatory view of a bent state of the sensor main body.
FIG. 6 is an explanatory view showing a state in which the leak sensor is incorporated in a material corrosion test apparatus.
FIG. 7 is an explanatory view showing an example of a sensor body of a conventional leak sensor.
[Explanation of symbols]
Reference Signs List 20 sensor body portion 22 connection portion 24 cylindrical insulator 26 core wire insertion hole 28 core wire 30 coil

Claims (3)

A sensor body with a structure in which a metal core wire is inserted into a row of a large number of electrically insulating insulators made of a heat-resistant and corrosion-resistant substance and having a core wire insertion hole at the center, and the outer periphery of the insulator row is surrounded by a metal protection member. A sensor for detecting leakage of the conductive liquid material by detecting a change in electrical resistance between the core wire and the protection member, wherein a coil is used as a protection member surrounding the outer periphery of the insulator row. Material leak sensor. 2. The leakage sensor according to claim 1, wherein the insulator comprises two types of insulators: a cylindrical insulator and a spherical insulator having an outer diameter larger than the inner diameter of the cylindrical insulator, and these are alternately arranged. . 3. The leakage sensor for a conductive liquid material according to claim 2, wherein a through hole is formed in a side surface of the cylindrical insulator so that the conductive liquid material can enter.

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