JP2001201280A - Method for repairing plate hole of plate-type heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method, by which the plate hole of a plate-type heat exchanger can be repaired durably and highly reliably, without causing defects where an airtight mechanism becomes unmaintainable due to thermal strain, by reducing the quantity of heat as small as possible at repairing of the hole and other defects, such as a volume loss, etc., which occur when a repairing material is stripped off or made thicker in thickness. SOLUTION: In the method, a hole formed in the plate of the plate type heat exchanger by corrosion is repaired by closing the hole through silver- soldering. The hole is closed in such a way that a precooled heat absorbing jig having the bottom face matching the shape of the plate, and a working hole for sliver soldering is placed on the plate by aligning the working hole with the hole of the plate and the bottom face with the shape of the plate and the hole is closed up with silver solder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for repairing a plate hole of a novel plate heat exchanger. Particularly, in a water treatment process in a semiconductor factory or the like, a temperature of 75
It is useful for a plate hole repairing method of a plate heat exchanger used for concentrating semiconductor washing water containing -100 ° C, 60% salt, and other chemicals.

[0002]

2. Description of the Related Art At present, in a water treatment process in a semiconductor factory or the like, a plate-type heat exchanger is used to concentrate semiconductor cleaning water containing, for example, a temperature of 75 to 100 ° C., a salt content of 60%, and other chemicals. ing.

When this heat exchanger is used for a long period of time, dirt adheres to the surface of the plate, and the performance of the heat exchanger is reduced to hinder operation.

For this reason, the plates of the heat exchanger must be replaced with new or remanufactured ones as appropriate. However, it is strongly desired to refresh and reuse the dirty and defective plates in terms of cost.

[0005] For this reason, dirt attached to the plate has been removed by thermal expansion and contraction due to thermal shrinkage using dry ice or the like. However, since the dirt is hard and strong, it is very difficult to remove it. However, there is a drawback that it is difficult, uniform and incomplete. Therefore, at present, a plate-type heat exchanger in which 200 to 300 plates are assembled is disassembled to make a dirty plate (stainless steel (SUS304, SUS316) made of 0.9 × 2. The surface (both front and back surfaces) of about 2 m and the mass is about 16 kg is mechanically (physically) rubbed with a wire brush (electric tool), and the dirt component (hardness component, silica) , Scales, etc.). However, it is very hard work to braze both sides of a plate that is about the size of a tatami mat and weighs 16 kg, and it is a limit of about three per day per person. Scale (especially in the process of water treatment in semiconductor factories, the temperature is 75-100 ° C, dissolved minerals (calcium salts, magnesium salts, etc.) as the semiconductor washing water containing salts and other chemicals and the steam for heating are concentrated.
Are deposited and adhere to the water side of the heat transfer surface. Such scales significantly impede heat transfer and result in overheating of the heat transfer surface. ) And the like, most of which were difficult to drop, and it was necessary to replace the wire brush two or three times per sheet. For this reason, there is a problem in that it is difficult to machine and automate, so that labor is required and work costs are increased. Further, a dirt component (including a plate component whose surface has been shaved off) such as a hardened component, silica, scale, or the like that has been shaved off may become powdery and may not be completely collected. Especially in water containing salt and other chemicals in the water treatment process in semiconductor factories, toxic substances, for example,
It contains arsenic and the like, and such a substance may be precipitated as dirt. If uncollected dirt components are left as they are, there is a risk that the health of workers and the surrounding environment may be polluted. In addition, there were problems such as not only not being able to remove cleanly due to scratches caused by the brush, but also corrosion progressing from such scratched scratches and shortening the product life of the plate by scraping the plate itself and thinning. .

Accordingly, the present inventor has already disclosed in Japanese Patent Application No.
No. 76900, a new cleaning method was found. According to this method, as a plate cleaning method for a plate heat exchanger, a plate of a plate heat exchanger that is contaminated by use is washed using a dissolving chemical solution containing hydrofluoric acid. It is. Further, preferably, the plate is further washed with an acid after washing with the chemical solution for dissolution.
More specifically, (a) a washing step of putting the plate of the plate heat exchanger soiled by use in a dissolving chemical solution containing hydrofluoric acid to wash the stain components, and (b) the washing step (C) placing the plate, which has been subjected to the acid treatment, in a weak alkaline aqueous solution, wherein the plate having been subjected to the acid treatment is subjected to acid washing. A neutralization treatment step of neutralizing a chemical solution, and (d) the plate that has been subjected to the neutralization treatment step,
And a washing step of washing with water. And especially, the plate of the plate-type heat exchanger is made of stainless steel, and the plate-type heat exchanger is used in a water treatment process in a factory to wash water containing impurities used in a washing process. In the case of a plate heat exchanger used for concentrating, especially in a water treatment process in a semiconductor factory, a plate heat exchanger used for concentrating semiconductor cleaning water containing salt and other many chemical components, etc. It is useful for cleaning plates that have become defective due to solid dirt components consisting of complex components derived from semiconductor cleaning water, such as salts and many other chemical components, being solidified on the surface of the plate by use. Is found.

Next, in order to maintain and reuse the plate of the plate type heat exchanger that has been operated for a long period of time, a defect, that is, a hole caused by corrosion formed in the plate due to use is repaired after the above-mentioned cleaning. I have.

[0008] One method of closing a defect hole formed in a plate is a repairing method by welding. Specifically, a repair method using inert gas arc welding such as TIG welding performed by wrapping the arc with an inert gas (argon, helium, or a mixture thereof) and shutting off the air is employed. A welding method that generates such an arc and uses the high temperature that occurs can weld conventionally difficult materials such as heat-resistant and corrosion-resistant steel such as stainless steel and light alloys, and prevents oxidation of metals at high temperatures. And automatic or semi-automatic welding can be performed.

Therefore, a method of closing a hole by welding is as follows.
The durability and reliability are good and there are no drawbacks such as peeling when filling with resin and loss of volume due to increasing the thickness, so the repair result seems to be the best, but the effect of heat from the welding process at high temperatures Is a problem.

[0010] In general metal welding, a sudden change in temperature causes a change in the shape of the material, a change in the material, or the like, which may make it impossible to satisfy the purpose of use.

[0011] From the above, the same applies to the plate of the plate heat exchanger. If welding is performed at the time of repairing a defective hole and the resulting distortion is generated, a confidential structure as the plate heat exchanger can be obtained. It cannot be maintained and cannot be used.

Accordingly, in the welding operation, the amount of heat must be reduced as much as possible, and the occurrence of distortion must be suppressed by performing the welding process.

On the other hand, as a method of minimizing the amount of heat at the time of repair, a method of closing a hole using FRP resin or the like has been studied. Loss. That is, the flow path formed when these plates are assembled is narrowed, and there is a problem that the function as a plate heat exchanger is hindered. Since the FRP resin is not fused to the plate,
If the internal pressure becomes negative during use as a plate heat exchanger, there is also a problem that peeling is likely to occur and reliability is lacking. Furthermore, the point that the followability due to thermal expansion and contraction differs between the plate and the resin also leads to the ease of peeling. In the plate heat exchanger, many chemicals are used, and corrosive chemicals are also used. Therefore, FRP resin or the like may not be able to secure sufficient chemical resistance. Because of these problems, it is advantageous that the amount of heat during repair can be minimized, but since there are more problems,
At present, no repair method using resin has been adopted.

Further, a brazing repair method using solder, which is a brazing filler metal having a low melting point of less than 450 ° C., has also been studied. However, as in the case of TIG welding, the amount of heat at the time of repair is still large, causing distortion. The chemical solution used during heat exchange (various corrosive chemical solutions are used depending on the application) and the chemical solution (acids such as nitric acid) used at the time of cleaning by the above-described cleaning method discovered by the present inventors are used. Even after repairing, at the time of heat exchange or at the time of cleaning according to the invention of the present application, all parts that have already been repaired are completely dissolved, so that the recycling period is shortened, and there is a problem that these need to be repaired for each recycling.

[0015]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to eliminate the drawback that the amount of heat during repair can be reduced as much as possible and the security mechanism cannot be maintained due to the distortion due to heat. It is an object of the present invention to provide a plate hole repairing method for a plate type heat exchanger which is excellent in durability and reliability without a drawback such as a loss of volume due to a large amount.

Another object of the present invention is to provide a method for repairing a plate hole of a plate type heat exchanger, wherein the repair material has excellent chemical resistance to chemicals used during cleaning or heat exchange. Things.

From such a viewpoint, a method of silver brazing and heat absorption has been found as a method of repairing a defective hole formed in a plate of a plate heat exchanger.

[0018]

Means for Solving the Problems In order to achieve the above object, the present inventors have made intensive studies on a method for repairing a plate hole of a plate heat exchanger, and as a result, have completed the present invention. is there.

That is, the object of the present invention is as follows:
This is achieved by (5).

(1) A method for repairing a plate of a plate type heat exchanger by closing a hole caused by corrosion formed in a plate by silver brazing, which has a precooled bottom surface conforming to the shape of the plate and a silver brazing. Using a jig with a work hole for attaching,
The work hole of the jig is aligned with the hole of the plate, the jig is placed on the plate with the bottom surface of the jig adjusted to the shape of the plate, and the hole of the plate is closed with silver brazing. A plate hole repair method for a plate-type heat exchanger, characterized in that:

(2) The jig flows a molten metal material onto the plate (a) to produce a metal plate having a predetermined thickness whose bottom surface matches the shape of the plate. A metal plate is cut to a predetermined size to form a metal block, and (c) a metal plate or a metal block is formed by forming a working hole for brazing work of a predetermined size. The plate hole repair method for a plate heat exchanger according to the above (1).

(3) The plate is characterized in that the surface of the plate contaminated by use is cleaned by using a dissolving chemical solution containing hydrofluoric acid, and a hole due to corrosion is found by a subsequent inspection. The plate hole repair method for a plate heat exchanger according to the above (1) or (2).

(4) The method for repairing a plate hole of a plate heat exchanger according to any one of the above (1) to (3), wherein the plate is a corrugated plate made of stainless steel.

(5) The method of (1) to (1), wherein the method of pre-cooling the jig is by dry ice.
(4) The method for repairing a plate hole of a plate heat exchanger according to any one of (4).

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION In the plate hole repairing method for a plate type heat exchanger according to the present invention, holes formed by corrosion (hereinafter, simply referred to as defective holes) formed in the plate of the plate type heat exchanger are closed with silver brazing. Using a pre-cooled heat absorbing jig having a bottom surface conforming to the shape of the plate and having a working hole for silver brazing, wherein the working hole of the jig is replaced with a defective hole in the plate. And mounting the jig on the plate with the bottom surface of the jig conforming to the shape of the plate, and closing the defective hole of the plate with silver brazing.

According to the plate hole repairing method of the plate type heat exchanger of the present invention, the amount of heat used for repairing is higher in silver brazing than in soldering, but is significantly smaller than that in TIG welding, and the distortion of the plate is reduced. It is advantageous for. Furthermore, by using a metal material having a large contact area with the plate and a high thermal conductivity as the heat absorbing jig, the heat during the hole repair can be effectively absorbed, and the distortion of the plate can be suppressed extremely effectively. . In addition, silver brazing does not melt a part of the plate as in TIG welding, has extremely excellent surface smoothness, can maintain the flow characteristics in the heat exchanger extremely well, and can prevent contamination of scale and the like. Is difficult to adhere, and T
Compared with IG welding etc., it requires less work and requires less repair area, and requires less time to repair.In addition, chemicals such as acids used in the above-mentioned cleaning method found by the present inventors and chemicals used during heat exchange Because of its excellent chemical resistance, the parts repaired once, such as solder, can be made extremely durable and reliable without the risk of melting during subsequent heat exchange or cleaning. Having.

Hereinafter, a preferred embodiment of the present invention will be described.
A description will be given in accordance with the manufacturing process.

A) Preparation Step (i) Production of Heat Absorbing Jig First, a metal heat absorbing jig shown in FIG. 2 is formed according to the shape of a plate such as a corrugated plate as shown in FIG. Is prepared. More specifically, (a) flowing a molten metal material onto a plate to produce a metal plate having a predetermined thickness whose bottom surface matches the wavefront of the plate. Specifically, a plate is placed substantially horizontally, and a molten metal material is flown over the plate to produce a metal plate having a predetermined thickness whose bottom surface matches the wavefront of the plate.

(B) Next, if necessary, the metal plate is cut into a predetermined size to produce a metal block. Specifically, when the molten metal material solidifies (when it solidifies), it is removed from the plate and cut into predetermined dimensions to produce a metal block. However, if the metal plate is made in a size that can be used as a jig as it is, the step can be omitted. The cutting in this step may be performed simultaneously with the drilling in the next step (c), or may be performed after the drilling in the next step (c).

(C) A desired jig is manufactured by making a working hole for brazing work of a predetermined size in the metal plate or the metal block. As described in (b) above, after a plurality of working holes are formed in the metal plate, the metal plate may be cut to a predetermined size if necessary.

The plate used here may be the one that is actually provided for repair (in this case, it is preferable that the plate after cleaning is used, and it is necessary to use a portion without holes). A plate having the same shape as the plate to be repaired and having no corroded holes (a new plate or a cleaned product for regeneration) may be used.

The plate is preferably installed horizontally, but may be installed almost horizontally. In other words, even if the metal plate is inclined to some extent, the bottom surface of the formed metal plate has a predetermined corrugated shape, and only a difference in plate thickness occurs. This is because the use of the material does not particularly affect the heat absorption characteristics at the time of repair.

As a metal material that can be used for the heat absorbing jig, a metal material having a lower melting point and a higher thermal conductivity than a plate material is preferable. For example, lead, copper, aluminum, tin, zinc and the like are preferable. Melting at low temperature,
Lead, which is easy to cut, has high thermal conductivity and is inexpensive, is more preferable.

Before flowing molten metal such as lead on the plate, an appropriate dam (weir) is formed around the relevant portion, and an appropriate release agent is applied to the relevant portion. Is also good.

The dimensions (length and width) of the metal plate are not particularly limited, and may be determined depending on how many target jigs are cut out. However, when using a plate to be actually repaired, it is desirable to avoid the occurrence of distortion appropriately, for example, by pouring a molten metal material into the plate so that a certain amount of the material is poured so that no distortion occurs. .

The thickness of the metal plate is usually 1
The range is 0 to 60 mm, preferably 15 to 50 mm, and more preferably 20 to 30 mm. Here, the thickness of the metal plate (= the thickness of the jig) refers to the height from the peak of the bottom surface of the wavefront shape to the upper surface, as shown in FIG. It is preferable that the thickness of the metal plate is larger because the heat absorption capacity at the time of repair increases, but when the thickness of the metal plate exceeds 60 mm, if the thickness is excessively large, the mass when processed into a jig increases. It is not preferable because handling work becomes difficult and working holes are difficult to work. On the other hand, when the thickness of the metal plate is less than 10 mm, one hole is repaired at the time of repair, depending on the dimensions (length, width) of the jig and the depth from the crest to the valley of the bottom of the jig. In some cases, the jig loses its heat absorbing ability during the process, and it is necessary to replace the jig with another jig.

It is sufficient that the bottom surface of the jig coincides with the wavefront of the plate almost completely. This is because each plate may have a very small distortion within its allowable range, so that the plate used for manufacturing the jig and the plate currently used for repair have their own unique This is because the distortion may cause the bottom surface of the jig and the wavefront of the plate not to completely match.

The method for cutting the metal plate is not particularly limited, and a conventionally known method can be applied. Preferably, cutting is performed while preventing generation of distortion so that distortion of the wavefront shape of the bottom surface due to heat at the time of cutting is not generated. For example, the cutting may be performed while spraying a coolant (for example, a coolant or a cutting oil), the cutting may be performed by a jet stream, or the working hole described later may be simultaneously formed by punching. In addition, depending on the metal material, a hole may be formed by laser machining or electric discharge machining using a wire or a rod.

As the dimensions of the metal block, the size of the pitch of the peaks or valleys of the corrugated shape of the target plate (see dimension B in FIG. 1), the thickness of the plate, and the repair work of one hole The amount of heat generated at the time of repair is calculated from the time required for the repair, and the thickness is appropriately determined, including the above-mentioned thickness, based on these. Usually, one side (or diameter) is 80 to 300 mm, preferably 100 to 300 mm. 250
mm, more preferably in the range of 120 to 200 mm, such as a square, a rectangle, a rhombus, and a circle. When the length of the one side is less than 80 mm, the heat absorption amount is small depending on the plate thickness, and the heat absorbing ability of the jig may be lost while repairing one hole at the time of repair. Since it is necessary to replace the jig with another one, it is not preferable that the work efficiency is reduced. On the other hand, when it exceeds 300 mm, the mass of the jig becomes large and the handleability decreases, and it becomes difficult to repair the jig without touching the jig, so that the workability may decrease. Not preferred.

The method for drilling working holes in the metal block is not particularly limited, and a conventionally known method can be applied. Preferably, drilling is performed while preventing distortion from occurring, so that distortion of the wavefront shape of the bottom surface due to heat during drilling does not occur. For example, when drilling a small hole with a drill, drilling a working hole of a desired size with an end mill, or drilling a working hole with a milling cutter of a desired size, spraying a coolant (for example, coolant or cutting oil). Drilling may be performed while drilling, drilling may be performed by a jet stream, or punching may be performed simultaneously with the block cutting. In addition, depending on the metal material, a hole may be formed by laser machining or electric discharge machining using a wire or a rod. Further, the working hole may be provided with a taper so that the diameter increases from the bottom surface of the wavefront shape toward the top surface.

The optimum size of the working hole (minimum diameter) depends on the size of the pitch of the peaks or valleys of the corrugated shape of the target plate (see the size B in FIG. 1). In general, from the viewpoint of the workability of brazing a hole in a plate, the larger the better, the smaller the better for quick heat absorption.
It is 5 to 50 mm, preferably 30 to 45 mm, more preferably 35 to 40 mm. Dimension of the working hole (minimum diameter)
However, if it is less than 25 mm, the workability of brazing the hole of the plate is difficult, and it takes a long time for the brazing operation, which is not preferable. This is not preferable because rapid heat absorption is not possible and distortion is likely to occur. In addition,
One or two or more working holes may be provided for one jig, but preferably one working hole is provided for one jig in the center of the jig. It can be said that it is preferable from the viewpoint of heat absorption efficiency.

(Ii) Pre-Cooling of Heat Absorbing Jig Next, as a preparatory step, the metal heat absorbing jig is cooled in advance.

Here, the method of cooling the metal heat absorbing jig is not particularly limited, and a conventionally known cooling method can be appropriately used, and an appropriate refrigeration or freezer is prepared. Then, a method in which a jig is placed therein, a method in which cooling is performed by using an appropriate refrigerant (such as cold water, dry ice, or liquid nitrogen), and the like are included. Above all,
As a preferable cooling method, dry ice is spread on an ice box, and a lead heat absorbing jig is stored on the ice box for cooling. In this case, it is simple such that it can be easily carried to the work place, and since the used jig can be stored again in the ice box, it can be reused in a relatively short time. Can be continuously and efficiently repaired.

The cooling temperature of the metal heat absorbing jig varies depending on the various cooling means as described above, but is usually 0 ° C. or lower, preferably −80 to 0 ° C., more preferably −80 to −20. It is in the range of ° C. When the cooling temperature exceeds 0 ° C., the heat absorption is greatly affected by the temperature at the time of cooling. Therefore, it is preferable to use a method as low as possible. Before being put on the brazing work, it is cooled down to a very low temperature near the hole of the repaired part, so it becomes difficult for silver brazing to adapt, so dry ice is used as a cryogen that can obtain a low temperature of about -80 ° C (A solid carbon dioxide powder formed and processed; the sublimation temperature under atmospheric pressure is -78.5 ° C.). In particular, since dry ice does not liquefy but sublimates directly into a gas, it has an advantage that it is easy to maintain a constant temperature and the like.

(B) Repairing process In the repairing process, the hole made by the corrosion of the plate of the plate type heat exchanger is closed by silver brazing using the previously cooled jig and repaired. More specifically, (i) the plate is placed substantially horizontally, and (ii) a pre-cooled work hole having a bottom surface conforming to the corrugated shape of the plate, and a central work hole for brazing work. Using a jig having the above, the hole of the plate is placed substantially at the center of the working hole of the jig, and the jig is placed on the plate with the bottom surface of the jig adjusted to the corrugated shape of the plate. iii) Next, the hole of the plate of the target portion is closed with silver brazing.

Here, the plate to be repaired is not particularly limited, and, for example, in a water treatment process in a semiconductor factory or the like, for example, the temperature is set to 75.
A plate of a plate-type heat exchanger used for concentrating semiconductor washing water containing -100 ° C., a salt content of 60%, and other chemicals can be exemplified, but not limited thereto. Therefore, since the material of such a plate also differs depending on the intended use, stainless steel, titanium alloy,
Conventionally known various materials such as iron can be applied. The same applies to the size and thickness of the plate, for example, a corrugated sheet having a size of 0.9 × 2.2 m and a cross section shown in FIG. Dimension A = 0.7m
m, B = 13.3 mm, C = 4.0 mm, and FIG.
As shown in (C), the wave pattern is not uniform over the entire plate, but is symmetrical with respect to the central axis of the plate.
° One with an inclined wave pattern can be exemplified,
The present invention is not limited to these, and conventionally known plates of various sizes can be applied. Further, the shape of the plate is not particularly limited, such as a corrugated plate as shown in FIG. Shape can be applied. Moreover, even if one corrugated sheet is taken, as shown in FIG.
Various shapes have been developed to achieve optimal heat exchange efficiency depending on the intended use, such as non-uniformity in a single plate, but the present invention can be applied to all of these shapes. It can be said that it is made to order.

The plate to be repaired may be one obtained by removing the stain on the plate by an appropriate stain removal method. Preferably, the plate is provided by Japanese Patent Application No. 11-276900, which has already been proposed by the present inventors. It is preferable that the stain on the plate is removed by the novel washing method described in (1). In such a cleaning method, dirt is removed by dissolution using a chemical solution, and the surface is finished by washing with water, so that the plate surface is not scratched or shaved to be thin, and the dissolving chemical solution, and further, an acid solution for acid treatment. By adjusting the components and concentrations of the above, it is possible to finish the plate as new without corrosion of the plate.
Therefore, the familiarity between the plate and the silver solder is good, and the smoothness and flatness of the surface can be extremely excellent.
Further, in the conventional method for removing dirt, if dirt (hardness component, silica, scale, etc.) remains in the vicinity of the defect hole to be repaired, if silver brazing is performed through the scale, Because the location may cause peeling, it is necessary to remove some dirt in the vicinity of the defective hole by intending to scrape off a part of the plate, but since the surface of such a cut portion has reduced smoothness, during heat exchange There is a problem that dirt is easily attached, and it takes time to finish-polish such a cut portion to make it even more smooth. However, the cleaning method found by the present inventor is extremely useful without such a problem. It is. The details of the cleaning method described in Japanese Patent Application No. 11-276900 will be described later.

The plate to be repaired should be cleaned after removing the stain on the plate by means of removing the stain, preferably after removing the stain on the plate by the novel cleaning method described in Japanese Patent Application No. 11-276900. Plates with holes found by appropriate inspection are of interest. In addition, it is good to mark the hole discovered by the inspection so that it can be easily recognized.

Next, the plate to be repaired is preferably set horizontally on a suitable work table, but may be set substantially horizontally. In other words, the jig can be stably placed on the plate even if it is tilted to some extent, and the silver braze is repaired as long as the silver braze does not flow down along the slope and hinder the hole during the brazing operation. This is because the workability at the time is not particularly affected.

It is preferable that the work table is such that the plate is not distorted by the weight of the plate and the jig during the work, and from the viewpoint of promoting heat radiation, the contact area between the plate and the work table can be increased. It is preferable to have a flat surface large enough to stably support the whole,
The whole plate may be supported by a suitable frame material (vertical, horizontal, diagonal, etc.). In addition, although expensive, the surface of the workbench is processed so that it almost conforms to the wavefront shape of the plate, and the worktable itself needs necessary parts in some way, such as passing an appropriate refrigerant inside. Needless to say, it may be one that can be cooled in a timely manner according to the conditions.

Next, using the jig (= pre-cooling jig) cooled in advance in the above (A) preparation step, the holes of the jig are aligned with the holes of the plate. That is, one of the holes of the target plate (= the hole of the plate of the target portion) is located substantially at the center of the work hole of the jig so that the hole of the plate can be brazed through the work hole of the jig. It is desirable to adjust to. If the surfaces to be joined are flat surfaces, the plate can be easily adjusted so that the hole of the target plate is located at the center of the work hole. However, since the plate and the jig both have a corrugated shape, they are matched. Since it is necessary to move the plate along the shape, the adjustment may be made so that the hole of the plate of the target portion is approximately at the center of the work hole.

Further, the jig is placed on the plate with the bottom surface of the jig adjusted to the corrugated shape of the plate (see FIG. 2). Thus, the heat applied to the plate by brazing is transmitted and absorbed toward the jig.

The hole of the plate of the target portion is closed with silver brazing. At this time, there is no problem if the brazing operation is performed immediately after the jig is placed on the plate. In silver brazing, an appropriate flux may be used, and in this case, it is necessary to sufficiently remove the residual flux after the brazing operation. The above repairing steps (i) to (iii) may be repeatedly performed until all the holes in the plate are repaired.

For this reason, after the hole is filled, the mounted jig can be reused any number of times by removing it from the plate and cooling it.

Hereinafter, a cleaning method described in Japanese Patent Application No. 11-276900 will be described.

In the plate cleaning method for a plate heat exchanger described in Japanese Patent Application No. 11-276900, a plate of a plate heat exchanger contaminated by use is washed with a dissolving chemical containing hydrofluoric acid. Is performed. As a result, it is possible to selectively dissolve and wash only the dirt component from the plate that has become dirty during use, and to refresh the plate surface without any corrosion.

In a preferred embodiment of the plate washing method for the plate heat exchanger, the plate is washed with the chemical solution for dissolution, and then subjected to an acid treatment. As a more preferred embodiment, (a) a washing step of putting a plate of a plate-type heat exchanger soiled by use in a dissolving chemical solution containing hydrofluoric acid to wash the soiled components, and (b) An acid treatment step in which the plate subjected to the washing step is pickled by being put in a chemical solution containing an acid,
(C) placing the plate subjected to the acid treatment step in a weak alkaline aqueous solution to neutralize a chemical solution containing acid attached to the plate, and (d) performing the neutralization treatment step. A washing step of washing the plate with water.

In the following, based on the preferred embodiment,
This will be described sequentially according to the steps.

(A) Washing step In the washing step, the plate of the plate heat exchanger that has been soiled by use is washed using a dissolving chemical solution containing hydrofluoric acid. More specifically, The plate of the plate heat exchanger that has been soiled by use is put in a dissolving chemical solution containing hydrofluoric acid to wash the soiled components.

Here, the plate of the plate heat exchanger which is contaminated by use may be a plate of the plate heat exchanger used in every field.
Preferably, it is a plate of a plate heat exchanger used for concentrating semiconductor cleaning water containing impurities used in a semiconductor cleaning process in a water treatment process in a semiconductor factory. In the plate of such a plate heat exchanger, a passage for steam for heating and a passage for semiconductor washing water containing impurities used in the semiconductor washing step are formed, and in particular, used for the semiconductor washing step. The dirt deposited on the plate surface on the passage side of the semiconductor cleaning water containing impurities is extremely firmly consolidated. Therefore, with a conventional mechanical (physical) method such as a wire brush, dirt is effectively removed. Was not able to be dropped. Therefore, in the plate of the plate heat exchanger for such an application, the cleaning method of the present invention can provide a remarkable operational effect that can solve the technical problem in the conventional method.

The contaminant component formed by using the plate of the plate heat exchanger greatly differs depending on the use of the plate heat exchanger, and cannot be defined uniquely. In a water treatment process, for example, a plate of a plate heat exchanger used for concentrating semiconductor cleaning water containing impurities used in a semiconductor cleaning process, a plate surface on a passage side of a vapor path for heating. Is formed with scales and the like which are found in ordinary boilers and the like. On the other hand, the surface of the plate on the side of the passage of the semiconductor cleaning water containing impurities used in the semiconductor cleaning process has a hardness component (including toxic arsenic and the like in some cases) due to various chemicals and a semiconductor substrate. Are formed by solidly and strongly consolidating various components such as silica (or silicon-containing component) and scale, which are partially dissolved or shaved by etching or the like.

The material of the plate of the plate heat exchanger is not particularly limited, and can be applied to various materials used for the plate of a conventionally known plate heat exchanger. In particular, in the water treatment process in the semiconductor factory as described above, most commonly used as a plate material of a plate-type heat exchanger used for concentrating semiconductor cleaning water containing impurities used in a semiconductor cleaning process. It is preferable to use a stainless steel (SUS) material which is widely used in the present invention and to which the cleaning method of the present invention can be suitably applied.

Further, regarding the size and thickness of the plate of the plate heat exchanger, the plate heat exchanger is assembled so as to have a necessary processing capacity according to the intended use.
There is no restriction. In particular, the plate-type heat exchanger has features that the plate can be easily cleaned and assembled, and the heat transfer area can be adjusted by increasing or decreasing the number of plates. Mass) is often designed to be easy to handle, for example, used in a semiconductor factory water treatment process to concentrate semiconductor cleaning water containing impurities used in a semiconductor cleaning process. Taking the plate of the plate type heat exchanger as an example, the size is 2.2 in length.
A mx 0.9 m wide and about 1 mm thick is currently commercially available and common.

Further, it can be used in the washing step.
The concentration of hydrofluoric acid is not particularly limited
However, in terms of economy, impact on the human body and surrounding environment,
0.01-3.0% by volume, preferably 0.3-1.0
%, More preferably in the range of 0.3 to 0.5% by volume.
Good. If less than 0.01% by volume,
Soil components are not sufficiently removed in a short time (or
Unfavorable) in some cases. On the other hand, 3.0% by volume
If the amount exceeds the
Or, hydrofluoric acid is a complex species (F^-, HF_Two ^-Noho
Or H_TwoF_Three ^-, H _ThreeF_Four ^-, Etc.) exist
And is highly reactive and actively reacts with various substances
Despite having the
Components do not drop off (or dissolve)
It is not preferable because of the tendency.

[0065] In addition to the hydrofluoric acid, a chemical solution having a useful cleaning effect may be added to the dissolving chemical solution that can be used in the above-mentioned cleaning step, if necessary. It is preferable to use

The washing conditions with the above-mentioned chemical solution for dissolution include:
First, the liquid temperature is not particularly limited as long as it is not lower than the melting point and lower than the boiling point, but is usually room temperature from an economical viewpoint. In addition, since the washing time varies depending on the degree of contamination due to the use of the plate of the plate heat exchanger,
Although it cannot be specified unambiguously, it is usually 24-168.
Hours, preferably 48-168 hours, more preferably 7 hours
2 to 96 hours. If the washing time is less than 24 hours, the solidified solid components may not be sufficiently removed. On the other hand, if the cleaning time exceeds 168 hours, the dirt components have already been sufficiently removed, and it is not economical because no further effect equivalent to continuing the cleaning can be expected. However, even if the cleaning is continued beyond the above cleaning time,
There is no erosion of the plate itself and no particular problem.

The washing method is not particularly limited, as long as it is in a state where the solution for dissolution and the plate can be brought into contact with the plate most effectively. For example, hydrofluoric acid in dissolving chemicals to be handled is a colorless, irritating liquid that emits smoke in the air, is toxic and has the property of strongly invading the skin and mucous membranes. Therefore, polyethylene or paraffin dissolving tanks (containers) or The solution for dissolution is stored in the dissolution tank (container) of lead or lead-clad iron, and the plate of the plate type heat exchanger that has been contaminated by use is completely immersed in the solution for dissolution in this dissolution tank,
In a state where the dissolving tank is sealed and the chemical solution for dissolution is washed while appropriately stirring while maintaining the solution temperature, the viewpoint of the working environment and the surrounding environment, and further, in a water treatment process in a semiconductor factory. In the case of a plate-type heat exchanger plate used for concentrating the semiconductor cleaning water containing impurities used in the semiconductor cleaning process, the passage side of the semiconductor cleaning water containing impurities used in the semiconductor cleaning process is used. All toxic substances contained in the dirt components deposited on the plate surface also precipitate in the washing tank and are condensed. However, the present invention is not limited to these, because it is easy to perform. In addition, during the operation of immersing the plate in the chemical solution for dissolution, the operation of taking out from the chemical solution for dissolution, and further performing the subsequent processing, since hydrofluoric acid is vaporized or taken out with the plate, In all of the steps of the series of cleaning methods of the present invention, a system for collecting and purifying air and waste liquid should be provided so that toxic hydrofluoric acid is not taken out of the system or touched by workers. desirable.

(B) Acid treatment step In the plate washing method of the plate heat exchanger, it is preferable that the plate is washed with the chemical solution for dissolution and then subjected to an acid treatment. More specifically, it is desirable to perform an acid treatment step in which the plate subjected to the washing step (a) is placed in a chemical solution containing an acid and pickled. This makes it possible to clean dirt remaining on the plate surface. In particular, by combining with the above washing step,
In the above-mentioned cleaning step, the dirt component which is difficult to remove by the conventional physical method is dissolved and peeled off, and then the dirt component remaining on the surface in the acid treatment step is washed, so that the dirt component is completely removed only by the above-mentioned washing step Combining these two steps, compared to dropping, is economical because the overall time required can be reduced.

The acid component that can be used in the above-mentioned acid treatment is not particularly limited, and includes nitric acid, hydrochloric acid, sulfuric acid, hydrofluoric acid, and the like. What is necessary is just to select a suitable one, and a conventionally known chemical solution for pickling can be used. Specifically, those already on the market are desirable because they are easily available and relatively procurable. For example,
When the plate is made of stainless steel, stainless steel surface treatment agents (trade name: Last Clean RS, constituent components: nitric acid, hydrogen fluoride, degreasing agent, spreading agent) and the like are included, but are not limited thereto. Not something. The acid component may be used alone or in combination of two or more.

Regarding the concentration of the acid component used,
Any acid component (one or a combination of two or more components) is not particularly limited as long as it can exert the effect of cleaning dirt remaining on the plate surface. If the concentration is too low, the washing ability is weak, it takes a long time to sufficiently wash, and the plate itself may be corroded, which is not preferable. On the other hand, if the concentration of the acid component is high, the plate itself may be corroded and stained, which is not preferable. However, it should be noted that the optimum concentration varies depending on the type of the acid component. For example, with hydrochloric acid having a concentration of 0.1% by volume, the plate itself is corroded at room temperature for 6 hours. In the case of a commercial product, since components other than the acid component are also contained, a sufficient small washing effect can be obtained by conducting a small-scale experiment in advance within the effective concentration range indicated in the instruction manual and the like. It can be said that it is desirable to confirm that For example, the stainless steel surface treatment agent (trade name; Last Clean®)
When S) is used, the concentration of the stainless steel surface treating agent (including components other than the acid component) may be a stock solution. In addition, since many of the acid components have corrosive properties to the metal, the plate itself may be corroded.Therefore, not only commercial products, but also the degree of corrosion of the plate and the degree of dirt on the plate surface depending on the concentration of the acid component used. It can be said that it is desirable to sufficiently check in advance.

The treatment time with the acid is not particularly limited as long as the function and effect of cleaning dirt remaining on the plate surface can be exhibited. Especially when the material of the plate is stainless steel,
In a short time, the method of applying an acid may not be uniform even in a short time because it is porous. On the other hand, if the treatment time with the acid is longer than necessary, no further action and effect corresponding to the continuation of the pickling can be expected, which is uneconomical. Further, depending on the type of the acid component, the plate itself may be corroded. In the case of commercial products, since components other than the acid component are also included,
It can be said that it is desirable to perform a small-scale experiment in advance and confirm that a sufficient cleaning effect can be obtained within the effective time range indicated in the instruction manual or the like. For example, the stainless steel surface treatment agent (trade name; Last Clean RS)
When using, the processing time is 12 to 36 hours, preferably 18 to 30 hours. In addition, since many of the acid components are corrosive to metals, they may corrode the plate itself. Therefore, not only commercial products, but also the degree of corrosion of the plate and the plate surface for each appropriate elapsed time of treatment with the acid component used It can be said that it is desirable to sufficiently confirm the degree of dirt removal in advance.

The temperature (liquid temperature) of the chemical solution containing an acid is not particularly limited as long as it can exert the effect of cleaning dirt remaining on the plate surface. From a practical viewpoint, room temperature may be used. In the case of a commercially available product, since components other than the acid component are also contained, it is desirable to confirm in advance that a sufficient cleaning effect can be obtained by conducting a small-scale experiment in advance in the temperature range indicated in the instruction manual or the like. I can say. For example, when using the above stainless steel surface treatment agent (trade name: Last Clean RS), the liquid temperature of the treatment agent is also preferably room temperature. In addition, since many of the acid components have metal corrosive properties, they may corrode the plate itself.Therefore, not only commercial products, but also the degree of corrosion of the plate and the surface of the plate at each temperature of the chemical solution containing the acid used. It can be said that it is desirable to sufficiently confirm the degree of dirt removal in advance.

The acid treatment (pickling) method is not particularly limited, as long as it is in a state where the chemical solution containing the acid can most effectively come into contact with the plate. For example, the plate that has been washed in the washing step with the chemical solution for dissolution is pulled up from the dissolution tank by a suitable transport device,
A chemical solution tank (container) that is moved and stores an acid-containing chemical solution
The method of performing acid washing with a chemical solution containing an acid in a state where the chemical solution containing the acid is properly stirred while maintaining the solution temperature in a state in which the chemical solution is completely immersed in the chemical solution and the chemical solution tank is sealed, and the like. Although desirable from an environmental point of view, it is not limited to these.

(C) Neutralization Treatment Step In the neutralization treatment step, the plate subjected to the acid treatment step (b) is placed in a weak alkaline aqueous solution to neutralize the acid solution attached to the plate. is there.

Here, the alkali component of the weak alkaline aqueous solution that can be used is not particularly limited, and conventionally known alkali components such as sodium bicarbonate and slaked lime can be used. These alkali components may be used alone or as a mixture of two or more. In addition, even in the case of a weak alkaline aqueous solution, when an alkali component having metal corrosiveness is used, sufficient care must be taken so as not to corrode the plate itself.

The concentration of the weak alkaline aqueous solution may be any as long as it can sufficiently neutralize the acid component in the acid treatment step (b). If it is extremely thin, processing time and labor are required.
On the other hand, if the concentration of the weak alkaline aqueous solution is too high, there is a problem due to a radical neutralization reaction. In addition, although it depends on the neutralization treatment method, when providing an appropriate neutralization tank and performing the neutralization treatment,
Since the alkali concentration gradually decreases with use, it is desirable to construct a concentration management system capable of constantly monitoring the concentration with an appropriate concentration (pH) sensor or the like so as to maintain the above-mentioned concentration range, and replenishing the alkali component as appropriate.

The liquid temperature of the above-mentioned weak alkaline aqueous solution may be any as long as it can sufficiently neutralize the acid component in the above-mentioned (b) acid treatment step, but is preferably room temperature from an economic viewpoint.

The treatment time with the above weak alkaline aqueous solution may be any as long as it can sufficiently neutralize the acid component in the above (b) acid treatment step, and it depends on the neutralization method. When the neutralization treatment is carried out with the addition of the above, the time may be usually within one hour. If the treatment time with the weak alkaline aqueous solution exceeds 1 hour, no further action and effect corresponding to the continuation of the neutralization treatment can be expected, which is uneconomical.

The neutralization treatment method is not particularly limited, and may be any condition in which the weak alkali aqueous solution and the plate can be most effectively brought into contact with each other. For example,
A water tank (container) storing a weakly alkaline aqueous solution by lifting the plate that has been subjected to the acid treatment in the acid treatment step using a chemical solution containing an acid from the chemical solution tank and moving the plate, and moving the plate.
And completely immersed in the aqueous solution of the above, in a state where the water tank is sealed, and neutralizing while appropriately stirring while maintaining the weak alkaline aqueous solution in the above-mentioned concentration range. It is not limited to. For example, the weak alkaline aqueous solution may be sprayed on each plate. In this case, it is desirable to use a common spraying device such as a jet washer for spraying the weak alkaline aqueous solution and water so that the washing process can be performed continuously with the next washing process. That is, by appropriately switching the supply path to the jet washing machine between a weak alkaline aqueous solution and water, both processes can be performed by one jet washing machine.

(D) Rinsing Step In the rinsing step, the plate subjected to the (c) neutralization step is washed with water. This makes it possible to completely wash away the weak alkaline aqueous solution (which may contain a dirt component) adhered to the plate in the (c) neutralization step.

The washing method is not particularly limited, and any method may be used as long as it can most effectively remove the weak alkaline aqueous solution attached to the plate. For example, the plate neutralized in the neutralization treatment step using the weak alkaline aqueous solution is lifted from the water tank by an appropriate transport device, moved, and sequentially placed in a water tank (container) storing a plurality of waters, and completely placed therein. By immersing, the concentration of the weak alkaline aqueous solution attached to the plate can be reduced, and the water in the water tank is replaced by using one water tank and always allowing the water to overflow. By doing so, the concentration of the weak alkaline aqueous solution attached to the plate can be reduced, but since a large amount of water and a large amount of water are required, the neutralization treatment is preferably performed in the neutralization treatment step using the weak alkaline aqueous solution. The lifted plate is lifted from the water tank by a suitable transport device, moved, and then sprayed with water (high-pressure water) on each plate using a spraying device such as a jet washer. Put, although a method of washing away the weak alkaline aqueous solution adhered to the plate and the like, but is not limited thereto. For example, by using a jet washing machine having a function as an air gun, water droplets adhering to the plate surface may be blown off immediately after the washing step. There is no particular problem if the alkali component can be sufficiently washed away in the water washing step, but even if a slight alkali component or other impurities remain, in the case of natural drying, etc., water droplets eventually collect at the bottom of the plate, and during drying. It is preferable that the droplets be quickly blown off by the air gun or the like, or that the plate be horizontal and quickly dried with hot air.

[0082]

The present invention will now be described more specifically with reference to examples.

Example 1 (A) Preparation Step (i) Lead Heat Absorbing Jig Manufacturing Step The same corrugated plate as that to be repaired (the size of one sheet is 0.3 mm).
SUS316 with a size of 9 × 2.2m and having the cross section shown in FIG.
1A, dimensions A = 0.6 mm, B =
13.3 mm, C = 4.0 mm, and as shown in FIG. 1 (C), the wave pattern is not uniform over the entire plate, but is inclined symmetrically with respect to the central axis of the plate by 45 °. A plate that had been cleaned and had no defects due to corrosion was used. ) Was placed horizontally on a workbench, and molten lead was allowed to flow on the plate to produce a lead plate 260 × 280 mm with a bottom surface coinciding with the wavefront of the plate and having a thickness of about 20 mm.

When the molten lead has solidified (solidified),
The lead plate was removed from the plate and cut into a size (130 mm × 280 mm) as shown in FIG. 2 using a band saw to produce a lead block.

Next, a work hole having a diameter of about 38 mm for brazing was formed in the center of each lead block at the center, and two lead heat absorbing jigs were produced.

(Ii) Pre-cooling step of lead heat absorbing jig Dry ice is spread on an ice box, and the jig obtained in the above (i) is stored thereon and cooled for 60 minutes or more (the entire jig is cooled). (It can be cooled to about -80 ° C).

(B) Repairing Step In the repairing step, as shown in FIG. 2, (i) Japanese Patent Application No. 11-27690 which has already been proposed by the present inventor as described above.
In accordance with the more preferred embodiment (a) to (d) of the novel cleaning method described in No. 0, the corrugated plate is cleaned of dirt, and the corrosion defect holes 27 found by the inspection (a total of five A corrugated plate 25 (discovered) was placed horizontally on a workbench (not shown).

(Ii) Pre-cooled corrugated plate 25
Using a lead heat absorbing jig 21 having a bottom surface that matches the wavefront shape of the, and having a working hole 23 for brazing work in the center,
Adjust so that the defect hole 27 of the plate is almost at the center of the work hole 23 of the jig 21, and the bottom surface of the jig 21 is corrugated plate
The jig 21 was placed on the corrugated plate 25 according to the wavefront shape of 25.

(Iii) Next, the corrugated plate 25 of the target portion
The hole 27 of the plate with silver brazing
All upper defect holes 27 were repaired. During this time, the pre-cooled jigs were sequentially taken out of the ice box, and the used jigs were returned to the ice box again, cooled and reused, and the repair work was performed.

Table 1 below shows the results of a comparative measurement of the distortion of the corrugated plate when repaired by the above-mentioned method using the conventional TIG welding and the above-mentioned silver brazing. In the TIG welding, the same corrugated plate 25 as used in the above-mentioned silver brazing was used, and the TIG welding was directly performed using an AES-300 welding machine manufactured by Daihen Corporation without using the lead heat absorbing jig 21. After welding, trimming was performed as much as possible to remove fluff and the like, and post-processing was performed so that the welded portion was as smooth as possible, and then measurement was performed. on the other hand,
In the case of the above-mentioned silver brazing, the silver braze fits well to the plate, and is extremely smooth and flat without any swelling of the brazed portion, so that no post-treatment is required.

[0091]

[Table 1]

As shown in FIG. 3, the measuring method is such that the corrugated plate sample 31 before and after the repair is placed on the platen 39, and the wavefront (valley side) of the corrugated plate sample 31 is evenly applied to the platen. (Not shown) was placed around the part to be measured (weight handling before and after repair was exactly the same).

The determination of the distortion is based on the wave height, that is, the height of one peak adjacent to the silver brazing (TIG welding) portion 33 (peak 35a) and the height of the other peak (peak 35a). Mountain Peak 37
= B). In the measurement, dial gauges were applied to the peaks 35 and 37 on both sides of the silver brazing (TIG welding) portion 33 to compare and measure before and after silver brazing (TIG welding), and the amount of change was obtained. In this experiment,
For both silver brazing and TIG welding, measurements were made for two silver brazing (TIG welding) portions 33, and the results are summarized in Table 1. The silver brazing (TIG welding) portion 33 shown in FIG. 3 is exaggerated for clarity.
Actually, as described above, the silver brazed portion has almost no swelling and has a smooth and flat finish. On the other hand, the TIG-welded portion melts the plate itself as shown in FIG. 3, so that the TIG-welded portion swells, and welding marks remain on the welding surface of the plate and the back surface thereof, so that smoothness and flatness are lost.

As shown in Table 1, the maximum value of the peaks 35 and 37 on both sides of the silver brazed portion 33 is +0.05 m in the silver brazing.
In m, the basic dimensions of the peaks 35 and 37 of the peak of the corrugated plate sample are those represented by the dimension C in FIG. 1A, and the maximum height (peak value) of the peak (or valley) is 4.0 mm. Therefore, the change value was 50/4000, which was an extremely small value, and was a size that could be ignored as a plate of a heat exchanger. On the other hand, in TIG welding, the maximum value is +0.50 mm.
The basic dimensions of the sample are those shown in FIG.
mm, the change was 500/4000, which was 10 times as large as that of silver brazing, and it was a dimension (distortion) in which it was difficult to maintain the airtight structure as a plate of the heat exchanger. The silver brazing in Table 1 (TIG welding)
The measurements before and after are based on the measured value of the first spot of the silver brazing as a reference (0.00), and are, so to speak, relative values indicating some of the measured values, not absolute values.

[0095]

According to the repairing method of the present invention, when repairing a defective hole due to corrosion formed in a plate of a plate type heat exchanger, the plate can be recycled so that it can be used with the same function as the initial plate when reused. In addition, when the resin is applied, there are disadvantages such as peeling and a decrease in heat exchange ability, soldering cannot withstand the chemical cleaning of the heat exchanger, and the like, and in direct welding (such as TIG welding), the plate is distorted. However, the repair method of the present invention does not cause such a problem.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a corrugated plate as one embodiment of a plate of a plate heat exchanger according to the present invention, and FIG. 1 (A) shows a direction perpendicular to a wave row of the corrugated plate. FIG. 1 (B) is a drawing showing a plate cut surface of FIG.
(A) is a perspective view including a plate cut surface of the corrugated plate,
FIG. 1C is a plan view of the entire corrugated plate.

FIG. 2 is a schematic view showing an embodiment of a lead heat absorbing jig according to the present invention, wherein FIG. 2 (A) is a plan view and FIG. 2 (B) is a side sectional view. .

FIG. 3 is a schematic diagram for clarifying a measurement site used for measuring a state of strain after repair of a plate sample of the plate heat exchanger used in the present embodiment, and is mounted on a surface plate. It is a figure showing the board cut surface of the direction perpendicular to the row of waves of the corrugated plate.

[Explanation of symbols]

A: The thickness of the corrugated plate, B: The pitch of the peak (or valley) of the corrugated plate, C: The maximum height (depth) of the peak (or valley) of the corrugated plate, 21: Heat made of lead Absorption jig, 23… Work hole, 25… Corrugated plate, 27… Defect hole, 31… Corrugated plate sample, 33… Silver brazed (TIG welding) part, 35… Silver brazed (TIG welding) part The height of one peak (= a), 37: the height of the other peak (= b) adjacent to the silver brazing (TIG welding) portion, 39: platen.

Claims (5)

[Claims] 1. A method for repairing a plate of a plate heat exchanger by closing a hole caused by corrosion formed in a plate by silver brazing, comprising a precooled bottom surface conforming to the shape of the plate and silver brazing. Using a heat absorbing jig having a working hole for the jig, the working hole of the jig is aligned with the hole of the plate, and the bottom surface of the jig is adjusted to the shape of the plate, and the jig is placed on the plate. A method for repairing a plate hole of a plate heat exchanger, comprising closing the hole of the plate with silver brazing. 2. The jig comprises: (a) flowing a molten metal material on a plate to produce a metal plate having a predetermined thickness whose bottom surface matches the shape of the plate; A metal block is prepared by cutting the plate to a predetermined size, and (c) a metal plate or a metal block is prepared by forming a working hole for brazing work of a predetermined size. The method for repairing a plate hole of the plate heat exchanger according to claim 1. 3. The plate according to claim 1, wherein the surface of the plate, which has been soiled by use, is cleaned by using a dissolving chemical solution containing hydrofluoric acid, and a hole due to corrosion is found by a subsequent inspection. 3. The method for repairing a plate hole of a plate heat exchanger according to claim 1 or 2, wherein 4. The method according to claim 1, wherein said plate is a stainless steel corrugated plate. 5. The method for repairing a plate hole of a plate heat exchanger according to claim 1, wherein the method of pre-cooling the jig is performed by dry ice.