JPH11173446A - Melting plug for preventing electric corrosion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of electric corrosion between a melting plug body and a closing member in a melting plug. SOLUTION: The lower end part of a first inner cylinder engaged with a second inner cylinder is positioned at the lower end of a melting plug body 1, and a closing member 2 comprising a melting material such as a solder is brought into pressure contact with the lower part of the melting plug body 1 through an O-ring 6 by this lower end part. A this film which is formed of the same metal as metal forming the melting plug body 1 and whose thickness is formed thinner to such extent of from 10 to 20 μm is arranged as an electric corrosion preventing member 3 on the lower surface of the closing member 2, thereby the whole part of a melting plug, which is brought into contact with boiler water in a boiler 50 is covered with the same metal. As a result, electric corrosion produced between the different kinds of metal can be prevented. In the case that the closing member 2 is melted at a predetermined temperature, the electric corrosion preventing member 3 is bucked by the inner pressure of the boiler 50 at the same time when the closing member 2 is melted, and exhausted together with boiler water to the outside through an emergency exhaust pipe 56.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a melting plug, and more particularly to a melting plug configured to prevent corrosion of a metal constituting the melting plug.

[0002]

2. Description of the Related Art In a device such as a hot water boiler in which a high-temperature fluid is present, damage to the device due to a sudden rise in temperature (pressure) of the internal fluid or a catastrophic accident such as an explosion is prevented in advance. Dissolving plugs are installed to perform this.

FIG. 6 shows a state in which a melting plug is installed in a hot water boiler 50. The water filled in the heated space 52 is heated by the combustion of the fuel in the combustion chamber 51 in the can, and the hot water having a predetermined temperature is discharged out of the system through the hot water pipe 53. In such a hot water boiler, the temperature and pressure in the can are increased for some reason such as abnormal combustion of fuel, poor control of fuel supply, and the like, and the pressure reaches a preset value. Then, the pressure relief valve 54 operates to release the pressure to the outside. However, the operating factor of the pressure relief valve 54 is only pressure, and has no effect on the temperature rise in the can, so that danger due to the temperature rise cannot be prevented.

[0004] The dissolving plug is designed to cope with such a situation, and the closed portion which is normally closed with a specific material melts and breaks in response to this rapid temperature rise, and the internal fluid is discharged. By forming a passage and discharging the internal fluid to the outside in a short time, damage to the device, an explosion accident, and the like are prevented in advance. Reference numeral 55 denotes this dissolving plug. When the internal fluid reaches a preset temperature, the closed portion is opened, and the hot water in the space to be heated is discharged to the emergency discharge pipe 56.
Through a large amount in a short time.

[0005]

FIG. 7A shows an example of a conventional structure of the above-mentioned dissolving plug. First, the main body 57 of the melting plug 55 is firmly screwed and fixed to the mounting seat 50a of the boiler 50. Reference numeral 58 denotes a closing portion for keeping the main body 57 closed at all times as a plug. As the closing member, solder, which is an alloy for brazing metal, is usually used.

FIG. 7B shows another conventional configuration. In this melting stopper, the solder as a closing member constituting the closing portion is formed in advance as a plate (disk) 59 having a predetermined thickness,
A sealing material 60 is provided on the periphery of the plate material 59 and
1 is screwed into the lower end of the main body 57 to form a sealing material 6.
A plate member 59 having a zero is fixed to the main body 57. In this configuration, since the solder constituting the closing portion is a plate material whose thickness is accurately determined in advance, the uniformity of the product is higher and the precision as a melting plug is higher than in the conventional configuration shown in FIG. It is possible to hold.

The main body 57 of the melting plug is made of the same material as that of the boiler 50, for example, stainless steel (SUS304 or the like) having high corrosion resistance. On the other hand, as the material forming the closing portion 5859, a metal material different from the metal material forming the melting plug main body 57, such as solder that melts at a predetermined water temperature as described above, is used.

[0008] In such a case, corrosion due to the combination of dissimilar metals becomes a problem. That is, when different metals are in contact with each other, a local current flows through both metals due to a potential difference between the two. In this case, the boiler water acts as an electrolytic solution, and this low-potential metal is ionized and elutes into the boiler water, causing electrochemical corrosion (hereinafter referred to as "electrolytic corrosion").

Here, the boiler itself is often made of stainless steel as described above in order to enhance the corrosion resistance. Therefore, in order to prevent electrolytic corrosion, it is desirable that the various members attached to the stainless steel boiler are also made of stainless steel or a material having properties equivalent thereto. However, in the melting plug 55, although the melting plug main body 57 can be made of the same stainless steel as the boiler, the melting material forming the closing portion 58 and the closing plate 59 is a low-potential metal such as solder. Therefore, a material having properties equivalent to those of stainless steel cannot be used. Therefore, FIG.
(A) and (B), a closed circuit is formed at the portion indicated by the symbol S, and the molten material having a low potential causes electrolytic corrosion. As a result, there is a danger that the boiler water leaks from the melting plug 55, and in some cases, the boiler water is discharged from the melting plug 55 during normal operation of the boiler.

[0010]

DISCLOSURE OF THE INVENTION The present invention relates to a melting plug configured in view of the above-mentioned problems, and relates to a melting plug configured to prevent electrolytic corrosion of a closed portion, such as a closing plate made of a melting material. is there. A first configuration for achieving this object is that, of the contact portion between the portion made of a melting material such as a closing plate and the melting plug main body, at least a portion that comes into contact with a liquid such as boiler water or the like. A metal thin film made of the same constituent material as the constituent material is interposed and arranged, and the melting material is covered from this thin film,
The surfaces in contact with the liquid are all dissolution plugs made of the same metal.

As a second configuration, there is provided a dissolving plug for preventing electric corrosion between different kinds of metals by forming the thin film from a non-conductive material of a non-metallic material.

As a third configuration, the melting plug main body is formed of a non-metallic material such as ceramics or heat-resistant plastic, so that the contact between the melting plug main body and the melting material is not the contact of a dissimilar metal. Therefore, even when the dissolving material is in direct contact with the boiler water, the dissolving plug is characterized in that electric corrosion is unlikely to occur.

Further, as a fourth configuration, the shape of the closing member is formed in advance by a metal thin film or a non-conductive thin film which is the same as the metal forming the melting plug main body. This is a melting plug having a closing member having a structure in which a closing member and a thin film are previously formed integrally by a method such as injecting and solidifying a metal.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A melting plug body is made of the same material as a metal to which the melting plug is attached, such as a boiler, so that electrolytic corrosion does not occur between the boiler and the melting plug body. . A closing member made of a melting material made of a metal material different from the melting plug main body such as solder is disposed on the melting plug main body. In this case, at the liquid contact surface of the closing member and at the contact portion between the closing member and the dissolving plug main body, a metal thin film having the same effect as the metal forming the dissolving plug main body, or a non-conductive non-metallic material (hereinafter referred to as the non-conductive The non-metallic material is simply referred to as “non-metallic material”).

In the case where the electrolytic corrosion preventing material is a metal thin film, the thickness of the material is extremely thin, about ten or several μm or several tens of μm. Is transmitted to Therefore, when the temperature of the boiler water rises above the specified value, the closing member is dissolved. Because the metal thin film has extremely small physical strength due to its thickness,
When the closing member melts, it is instantaneously buckled and deformed by the boiler water flowing out due to the boiler internal pressure, and is discharged to the outside together with the boiler water. Similarly, in the case of a non-metallic material, for example, the metal thin film and the process thickness are formed.

Further, as a method of forming the closing member, the metal thin film is formed in advance in the same shape as the shape of the closing member by bending.
Alternatively, a method is used in which a non-metallic material is molded, a molten material is injected into the molded metal thin film or the non-metallic thin film and solidified, and a closing member to which an anti-corrosion preventing material is attached in advance is adopted. It is also possible.

Further, as another means for preventing electrolytic corrosion, the constituent material of the melting plug main body is made of a non-metallic material such as ceramics or heat-resistant plastic from metal. Even if the closing member is attached to the melting plug main body formed of such a non-metallic material, no electrolytic corrosion occurs in this case.
Therefore, in this case, the electrolytic corrosion preventing material is unnecessary regardless of whether the material is metallic or non-metallic. However, since the expansion coefficient of the closing member, which is a metal material, and the melting plug body formed of a nonmetal material are often different, an intervening member made of a flexible material is provided between the melting plug body and the closing member. It is arranged and absorbs the difference in the expansion coefficient, and is used as a waterproof seal.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings. 1 and 2 show a first embodiment. In the figure, reference numeral 1 denotes a melting stopper main body, and the melting stopper main body 1 is made of a material [hereinafter, stainless steel (SUS30)
4) as an example]. The melting plug main body 1 is attached to the boiler 50 by appropriate means such as screwing, caulking, fixing with fastening parts, and an opening 1a for boiler water inflow is formed at the bottom of the melting plug main body located in the boiler. I have.

Reference numeral 2 denotes a closing member which is formed of a melting material such as solder which melts at a predetermined temperature. Reference numeral 3 denotes an anti-corrosion member disposed on the inside of the boiler, that is, on the side in contact with the boiler water, with respect to the closing member 2. In the configuration shown in the drawing, the anti-corrosion member 3 rises from the bottom surface of the closing member 2, It is formed so as to cover a part of the side circumference of the closing member 2 (see FIG. 2). The first configuration of the anti-corrosion material 3 is formed to be very thin, for example, 10 to 20 μm.
Due to this thinness, a metal thin film having extremely small physical strength, for example, having a feeling close to that of paraffin paper is obtained. Further, as the second configuration, the anti-corrosion material 3 can be made of a non-metallic material such as a heat-resistant plastic instead of the metal thin film. Also in this case, the thickness of the anti-corrosion material is determined so that the physical strength and the thermal conductivity described later are substantially the same as those of the metal thin film. Unless otherwise specified, an electrolytic corrosion preventive made of a metal thin film will be described below as an example.

On the other hand, reference numeral 4 denotes a first inner cylinder arranged in the melting plug main body 1 so as to share an axis with the melting plug main body. This first
The inner cylinder is screwed into a second inner cylinder 5 fixed to the melting plug main body 1 at the upper stage inside the melting plug main body 1. That is, a male screw portion 4 a is formed on the outer peripheral portion of the first inner cylinder 4, and the male screw portion 4 a is screwed with the female screw portion 5 a of the second inner cylinder 5. The first inner cylinder 4 has a function as a pressing member for fixing the closing member 2 in addition to a function as a boiler water passage at the time of emergency discharge. That is, an O-ring 6 is disposed as a sealing material at the periphery of the opening 1a at the lower end of the melting plug main body,
By appropriately rotating the inner cylinder 4, the closing member 2 and the O-ring 6 are pressed against each other with an appropriate pressure, so that water leakage does not occur.

In the above configuration, the melting plug is normally in a completely closed state, and the boiler 50 is normally operated. In this case, the boiler water is in direct contact with the anti-corrosion member 3, and the temperature of the boiler water is almost directly reduced with almost no temperature gradient via the anti-corrosion member 3, which is a thin metal film. 2 is transmitted. When the electrolytic corrosion preventing material 3 is a metal thin film, electrolytic corrosion hardly occurs because all parts constituting the dissolution plug are made of the same metal. When the corrosion preventing material 3 is formed of a non-metallic material, no electrolytic corrosion occurs because the non-metallic material is non-conductive.

Next, for some reason, the temperature inside the boiler rises, and when the temperature exceeds a specified value, the closing member 2 melts. Electrolytic corrosion preventing member 3 having lost physical strength as a result of this dissolution
Easily buckles (mainly in the case of a metal thin film) or breaks (mainly in the case of a non-metal thin film) due to the internal pressure of the boiler, and is flushed by the boiler water simultaneously with the dissolution of the closing member 2,
The boiler water is discharged to the outside via the emergency discharge pipe 56.

FIG. 3 shows a second embodiment. This embodiment is different from the first embodiment in the mounting structure of the closing member. That is, an attaching member 10A for attaching the closing member 2 is provided at a lower portion of the melting plug main body (indicated by reference numeral 10).
Is screwed. The anti-corrosion member 3 is disposed on the closing member 2 so as to cover the liquid contact surface and the side edge of the closing member 2, and the mounting member 10 </ b> A is screwed into the melting plug main body 10 to close this state. The member 2 is the melting plug body 1
0 and each step 10a and 10Aa of the mounting member 10A
To fix. Also in the case of this configuration, by arranging the anti-corrosion member 3, the portion of the dissolution plug that comes into contact with the boiler water is prevented from being electro-eroded. Although not shown in the illustrated configuration, it is naturally possible to dispose a sealing material at a contact portion between the closing member and the dissolution plug side. In addition to using the attachment member 10A, the closure member can be attached by other methods such as caulking the peripheral portion of the closure member 2.

FIG. 4 shows a third embodiment. In this embodiment, the material constituting the melting plug is changed from the above-mentioned metal material such as stainless steel to a non-metallic material. However, in this embodiment, the mounting structure of the closing member 2 itself is basically the same as that of the second embodiment.

In the present embodiment, both the melting plug main body 20 and the attachment member 20A screwed to the melting plug main body 20 are formed of a non-metallic material (hereinafter, ceramics will be described as an example). The closing member 2 is not provided with the electrolytic corrosion preventing member 3 used in each of the first and second embodiments. The closing member 2 is clamped and fixed between the melting plug main body 20 and the steps 20a and 20Aa of the mounting member 20A by screwing the mounting member 20A to the melting plug main body 20, as in the above-described embodiment. Reference numeral 21 denotes a displacement absorbing member disposed between the step portions 20a, 20Aa and the closing member 2, and is formed of a heat-resistant flexible material such as heat-resistant rubber. Since the ceramic constituting the melting plug main body 20 (attachment member 20A) and the solder, which is a metal material constituting the closing member 2, have different coefficients of thermal expansion, the relative displacement of the two caused by thermal expansion is reduced. Absorption by the displacement absorption member 21 prevents damage to the melting plug. The displacement absorbing member 21 also has a function as a sealing material for preventing water leakage. In this embodiment, since the dissolution plug main body is formed of a nonmetallic material, no electrolytic corrosion occurs.

As the non-metallic material, a specific heat-resistant plastic or the like can be used in addition to the above ceramics. In this case, plastics have much higher formability than ceramics unless problems such as deterioration or deformation due to heat occur.Therefore, these non-metallic materials should be used according to the type of boiler to be used, etc. It is advisable to form the dissolution plug body by appropriately selecting it.

FIG. 5 shows an example of a method for forming the closing member. In each of the first and second embodiments, the closing member 2 made of a melting material such as solder is formed in a predetermined shape in advance, and the anti-corrosion material 3 is arranged on the closing member 2. I have.

In the configuration shown in FIG. 5, the anti-corrosion member 3 is previously formed in a disk shape having the same shape as the final shape of the closing member 2, and the anti-corrosion member 3 formed as a disk-shaped container is provided. The molten material M that has been melted is injected. When the melting material M is solidified, the closing member 2 integrated with the electrolytic corrosion preventing material 3
Is formed. According to this method, when the melting plug is formed, there is no need to dispose the anti-corrosion member 3 with respect to the closing member 2, and there is a problem that the position of the anti-corrosion member 3 is shifted when the melting plug is assembled. As a result, the workability of assembling the melting plug can be improved.

[0029]

According to the present invention, an anti-corrosion material, which is a metal thin film made of a material having the same effect as the metal material forming the melting plug, is disposed at a contact portion between the closing member made of the melting material and the melting plug body,
Since all the parts of the melting plug that come into contact with the liquid are made of the same metal material, it is possible to prevent galvanic corrosion between different metals, prolong the life of the melting plug and prevent water leaks and melting. Malfunction of the stopper can be prevented.

Further, by forming the electrolytic corrosion preventive material from a non-metallic material, it is possible to form the dissolution plug in exactly the same configuration as in the case where the electrolytic corrosion preventive material is formed of the metal thin film. Accordingly, either a metal or a nonmetal can be appropriately selected as a material for forming the electrolytic corrosion preventing material.

Further, in another configuration of the present invention, by forming the dissolution plug main body from a non-metallic material, it becomes possible to prevent electrolytic corrosion without using an electrolytic corrosion preventing material.

Further, by injecting the dissolving material into the electrolytic corrosion preventive material, it is possible to obtain a closing member integrated with the electrolytic corrosion preventive material, assembling the dissolving plug, and resetting the dissolving plug after the emergency release. Can be easily performed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a dissolution plug showing a first embodiment of the present invention.

FIG. 2 is an enlarged view of a portion A in FIG.

FIG. 3 is a partial cross-sectional view of a dissolution plug showing a second embodiment of the present invention.

FIG. 4 is a partial cross-sectional view of a dissolving plug showing a third embodiment of the present invention.

FIG. 5 is a perspective view of a closing member showing an example of a method of forming a closing member integrated with an electrolytic corrosion preventing material.

FIG. 6 is a partial cross-sectional view of the hot water boiler showing a state in which a melting plug is attached to the hot water boiler.

FIG. 7A is a cross-sectional view of a dissolving plug showing a conventional dissolving plug.
(B) is a cross-sectional view of a dissolution plug showing another conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Melting plug main body 2 Closing member 3 Electric corrosion prevention material 4 First inner cylinder 5 Second inner cylinder 10 Melting plug main body 10A Mounting member 10a Step portion 10Aa Step portion 20 Melting plug body (of non-metallic material) 20A (Non-metallic material) ) Mounting member 20a Step 20Aa Step 21 Displacement absorbing member 50 Boiler M Melting material

Claims (8)

[Claims] 1. A dissolving plug in which a closing member is formed of a metal material different from a metal material forming a dissolving plug main body, and the closing member is melted at a preset temperature to form a liquid passage. In, between the closing member and the dissolution plug main body, by interposing the electrolytic corrosion prevention material which is a thin film formed of the same or the same metal material as the metal material constituting the dissolution plug main body, , At least the surface in contact with the liquid is configured to be covered with the same or the same metal material, and when the closing member is melted, the anti-corrosion material is also configured to be discharged together with the outflow liquid. Dissolution stopper to prevent. 2. A dissolving plug in which a closing member is formed of a metal material different from a metal material forming the dissolving plug main body, and the closing member is melted at a preset temperature to form a liquid passage. In the above, between the closing member and the dissolution plug main body, an anti-corrosion material which is a thin film made of a non-conductive non-metallic material is interposed, and when the closing member is dissolved, the anti-corrosion material is also discharged together with the outflow liquid. A dissolving plug for preventing electrolytic corrosion, characterized in that the dissolving plug is configured as described above. 3. A second inner cylinder is fixedly provided in the dissolution stopper main body,
The first inner cylinder is screwed into the second inner cylinder, a closing member is disposed on the lower surface of the dissolution plug main body, and an anti-corrosion material is disposed so as to cover at least the liquid contact surface of the closing member, and The lower end of the first inner cylinder is pressed against the closing member so that the closing member is pressed and fixed to a lower portion of the melting plug main body via a sealing material such as an O-ring. Or a dissolving plug for preventing electrolytic corrosion according to 2. 4. An attachment member is screwed into the dissolution plug main body, and an anti-corrosion material is disposed on a liquid contact surface of the closing member. The dissolving plug for preventing electrolytic corrosion according to claim 1 or 2, wherein the dissolving plug is configured to be clamped and fixed by the step portion on the side. 5. The dissolution plug for preventing electrolytic corrosion according to claim 1, wherein an electric corrosion preventing material is fixed to the closing member in advance. 6. The electrolytic corrosion preventing material is formed in advance in the same shape as the outer shape of the closing member, and the molten material melted into the electrolytic corrosion preventing material is injected and solidified to form the closing member with the electrolytic corrosion preventing material. The dissolving plug for preventing electrolytic corrosion according to claim 5, wherein the dissolving plug is formed integrally. 7. A dissolving plug in which a closing member is formed of a material different from a material forming the dissolving plug main body, and wherein the closing member is melted at a preset temperature to form a liquid passage. A melting plug for preventing electrolytic corrosion, wherein a melting material constituting a closing member is made of a metal material such as solder, and a melting plug body is formed of a nonmetallic material such as ceramics and heat-resistant plastic. 8. A displacement absorbing member made of a flexible material is disposed between the melting plug main body and the closing member, and thermal expansion between the non-metal material melting plug main body and the metal closing member. 8. The dissolving plug according to claim 7, wherein a relative displacement between the two is absorbed by the displacement absorbing member.