JP2003240388A - Method for judging using possibility of existing piping, and tool for checking using possibility of existing piping - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple judging method about the using possibility of an existing piping, for the purpose of re-using the existing piping in refrigerant- using equipment. <P>SOLUTION: This judging method for judging the using possibility of the existing piping is a method for judging the using possibility of the existing piping in an air-conditioner, and is provided with the first step and the second step. A residue left in an inside of the existing piping is applied onto a check sheet 30 in an installation site of the existing piping, in the first step. The using possibility of the existing piping is judged based on a color of the chuck sheet 30 applied with the residue, in the second step. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for judging the usability of an existing pipe and a tool for checking the usability of an existing pipe, and in particular, a judgment for making a judgment as to the usability of an existing pipe of a refrigerant using device. Regarding methods and check tools.

[0002]

2. Description of the Related Art In recent years, since the destruction of the ozone layer has become a problem, the reduction of HCFC used as a refrigerant has been started. In the future, stepwise reduction of HCFC refrigerants (HCFC22, etc.) will be promoted worldwide, and it is necessary to use alternative refrigerants such as HFC refrigerants instead of them.

Under such circumstances, there are an increasing number of cases where new refrigerant-using equipment (such as an air conditioner) using an alternative refrigerant is installed. By the way, in multi-type air conditioners installed in buildings such as condominiums and buildings, and in air conditioners (housing air conditioners) that perform air conditioning throughout the house in a private house, the refrigerant pipe connecting the indoor unit and the outdoor unit has a wall surface. It is buried in the building or goes through the ceiling. In such a case, in order to remove the existing air conditioner and install a new air conditioner, whether or not the existing refrigerant pipe can be reused (reused) by the new air conditioner is related to the installation cost. It will be an important factor. This is because it takes a lot of time and money to replace the existing pipe. Further, even in the case where it can be diverted, whether or not it is necessary to clean the existing refrigerant pipe is a factor for reducing the installation cost.

Generally, refrigerating machine oil containing impurities adheres to the existing pipe and remains. If this residual oil becomes extremely dirty, residual impurities may dissolve into the newly used refrigerant and the decompressor (expansion valve or capillary tube), which is the expansion mechanism, may become clogged and the refrigeration oil may deteriorate. high. In particular, the refrigerating machine oil used for the HFC refrigerant is a synthetic oil such as ether oil or ester oil, and has a property of easily dissolving the residual impurities in the existing pipe due to its high polarity. Therefore, when the HFC refrigerant is used in the new air conditioner, there is a high possibility that the decompressor of the new air conditioner may malfunction due to the residual impurities in the existing pipe.

Therefore, in the present situation, 10 to 20 years
When reusing existing pipes that have been used for a year, the inside of the pipes is cleaned using a washer.

[0006]

However, the washing machine for washing the existing pipe is very expensive, and the washing cost is not low. On the other hand, if the existing pipe is less contaminated, it is not necessary to wash it. Depending on the method of recovering the refrigerant and the oil, there are cases in which the contamination of the existing pipe is reduced and the need for cleaning is eliminated.

However, taking a sample of the residue in the existing pipe and returning it to a laboratory or the like to inspect the oil or the refrigerant in the existing pipe has conventionally been a more expensive operation than the cleaning operation. . For this reason, in most cases, the current situation is that the existing pipes are unconditionally cleaned by the cleaning machine as recommended by the manufacturer. An object of the present invention is to provide a simple method for determining the availability of an existing pipe for the purpose of reusing the existing pipe of a refrigerant using device.

[0008]

According to a first aspect of the present invention, there is provided a method for determining the availability of an existing pipe, which comprises determining the availability of an existing pipe of a refrigerant using device.
It comprises a step and a second step. In the first step, the residue remaining inside the existing pipe is attached to the check tool at the place where the existing pipe is installed. In the second step, the availability of existing piping is judged based on the color of the check tool with residue.

The present inventor collects a large amount of a sample of the residue in the existing pipe to be replaced or reused, and judges whether the existing pipe can be reused or whether cleaning is necessary. It was found that it can be judged by the color of the residue such as residual oil. Then, the present inventor uses a check tool,
By comparing the color of the residue in the existing pipe attached to this check tool with a sample, etc., we found that the usability of the existing pipe can be determined with high accuracy.

Based on this point of view, here, a check tool that can be used at the place where the existing pipe is installed is used, and the availability of the existing pipe is judged from the color of the check tool with the residue of the existing pipe. ing.
This makes it possible to determine the availability of existing pipes using a check tool on-site, and perform unnecessary cleaning work when the inside of the existing pipe is not so dirty and cleaning is not required, Even if the inside of the existing pipe is dirty to the extent that it cannot be used even after cleaning, it is possible to suppress the problem that the existing pipe is reused by performing only the cleaning work.

As the check tool, a tool that can judge the reusability by comparing the color of the residue itself with a predetermined color may be used. You can use a tool that can check and make a decision about reusability. The method of judging the availability of the existing pipe according to claim 2 is the judging method according to claim 1, wherein the check tool indicates a first means for attaching a residue and a reference color as a reference for judgment. And second means. Then, in the first step, a residue is attached to the first means. In the second step, the judgment is made by comparing the color of the first means with the reference color of the second means.

In this case, since the check tool is provided with the second means for indicating the reference color as the reference for judgment, the color of the first means of the check tool with the residue and the reference color of the second means are set. By comparing the above, the possibility of reusing the existing pipe can be judged very easily. The first means and the second means of the check tool are
They may be separate bodies, or both may be integrated.

According to a third aspect of the present invention, there is provided a method for determining the availability of an existing pipe, wherein the second means of the check tool indicates a plurality of reference colors. Here, since the second means indicates a plurality of standard colors, it is not only necessary to judge whether the existing pipe can be used or whether it is necessary to wash the pipe to use the existing pipe. It is possible to easily determine It will also allow other decisions regarding the availability of existing piping. Further, it is possible to provide a reference color for confirming that the existing pipe can be used.

According to a fourth aspect of the present invention, there is provided a method of determining the availability of an existing pipe, wherein the second means of the check tool indicates a normal color and a boundary color. The normal color is a color that does not require cleaning treatment when using the existing pipe. The border color is a color at the border that requires a cleaning process when using the existing pipe. Here, when the color of the first means with impurities is better than the boundary color, the color of the first means is further compared with the normal color, so that the existing pipe can be washed without worry. Will be available to you.

According to a fifth aspect of the present invention, there is provided a method for determining the availability of an existing pipe, wherein the second means of the check tool is a first boundary color and a second boundary color. Indicates. The first boundary color is a color that serves as a reference for determining whether or not the existing pipe needs to be cleaned. The second boundary color is a color that serves as a reference for determining whether the existing pipe can be used. Here, by comparing the color of the first means with the first boundary color of the second means, it is possible to judge whether or not the pipe cleaning work is necessary in the use of the existing pipe. Further, by comparing the color of the first means with the second boundary color of the second means, it is possible to judge whether or not the existing piping can be used.
That is, here, by comparing the color of the first means with the second boundary color of the second means, it can be determined whether or not the existing pipe needs to be discarded and replaced.

A check tool according to claim 6 is the check tool used in the method for judging the availability of an existing pipe according to any one of claims 2 to 5, wherein the first means and the second means are mutually Is located near and integrated with. In this check tool, since the first means and the second means are arranged close to each other, the color of the first means can be compared with the color of the second means to easily determine the usability of the existing pipe. .

According to a seventh aspect of the present invention, there is provided a method of determining the availability of an existing pipe according to the first aspect, wherein the check tool has a color changeable by acid or alkali.
H analysis tool. Then, in the first step, pH
Attach residue to analytical tool. In the second step, pH
Estimate the degree of deterioration of the residue from the color of the analysis tool and judge the availability of existing piping.

Here, since the check tool is a pH analysis tool, when acid or alkali is generated in the residue in the existing pipe, it is easy to judge the degree of acid or alkali from the color of the pH analysis tool. Is. Then, the degree of deterioration of the residue in the existing pipe can be estimated from the degree of acid or alkali. Based on the degree of deterioration of the residue thus estimated, it is possible to judge the availability of the existing pipe.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a refrigerant circuit diagram of an air conditioner having an outdoor unit 10 and an indoor unit 11. The discharge side and the suction side of the compressor 1 are connected to the primary port of the four-way switching valve 2. Further, the secondary port of the four-way switching valve 2 is provided with an outdoor heat exchanger 3, an expansion valve 4, and an indoor heat exchanger 5.
Are connected in sequence. Further, a liquid closing valve 6 and a gas closing valve 7 are provided in the refrigerant circuit.

The outdoor unit 10 and the indoor unit 11 are connected by a refrigerant communication pipe 9. This piping 9 is used in condominiums, buildings, houses with air conditioning systems throughout the building,
It is buried behind the walls and ceiling. At present, most of the air conditioners installed in such buildings and the like use HCFC22 as a refrigerant. When this is replaced with an air conditioner that uses an HFC-based refrigerant, use of the determination method according to an embodiment of the present invention described below will prevent unnecessary cleaning work, leading to cost reduction. be able to.

<Determination Method of Necessity of Cleaning Work in Reusing Existing Pipe> When removing the existing air conditioner, first, the liquid refrigerant is collected and collected in the outdoor heat exchanger 3 by pump down operation or the like. To do. As a result, the refrigerant and the refrigerating machine oil in the existing pipe 9 are removed, but the residual oil containing at least some contaminants remains on the inner surface of the pipe 9.

By simply checking the degree of contamination of the residual oil with the check sheet 30 shown in FIG. 2, it is possible to judge whether or not the cleaning work is required when the existing pipe 9 is reused. The check sheet 30 is a small business card-sized tool, and can be used at the place where the existing pipe 9 is installed. This check sheet 30
Is a first part 31 showing a cleaning necessity reference color, a second part 32 showing a normal oil color, and a sampling part 33 for attaching residual oil.
And an explanation part 34 for explaining the use are a sheet that is integrated. The cleaning necessity reference color of the first part 31 is a reference color for determining whether or not the cleaning processing of the pipe 9 is necessary when the pipe 9 is reused, and the residual oil color is darker than this. It is a standard color that allows you to judge that cleaning is necessary and thin cleaning is unnecessary. The normal oil color of the second part 32 represents the color of the residual oil that allows the pipe 9 to be reused without cleaning treatment. Therefore, if the residual oil color is closer to the normal oil color of the second portion 32 than the cleaning necessity reference color of the first portion 31, the pipe 9 can be reused without cleaning the pipe. The first portion 31 and the second portion 32 are arranged adjacent to each other and the sampling portion 33, respectively.

The sampling portion 33 of the check sheet 30 is made of absorbent cotton or cloth. For example, when the user wipes the inner surface of the pipe 9 with the check sheet 30, residual oil in the pipe 9 is attached. By comparing the color of the residual oil adhering to the collection part 33 with the cleaning necessity reference color of the first part 31, it is possible to judge whether or not cleaning is required when the pipe 9 is reused.

The outdoor unit 10 and the indoor unit 1 of the existing air conditioner
If the check sheet 30 is brought to the site when 1 is removed, it is possible to easily determine whether or not to reuse (reuse) the existing refrigerant communication pipe 9. The user first attaches the residual oil in the pipe 9 to the sampling part 33 by pressing the sampling part 33 of the check sheet 30 against the inner surface of the pipe 9, and then the color of the residual oil attached to the sampling part 33 is checked first. The comparison is made with the cleaning necessity reference color of the first part 31 and the normal oil color of the second part 32. Then, if the color of the residual oil of the collecting part 33 is closer to the normal oil color of the second part 32 than the cleaning necessity reference color of the first part 31, it can be determined that the pipe 9 need not be cleaned when reused. If the color of the residual oil of the collection unit 33 is darker than the cleaning necessity reference color of the first unit 31, it can be determined that the pipe 9 needs to be cleaned when it is reused.

The reference color of the necessity of cleaning of the first part 31 of the check sheet 30 and the normal oil color of the second part 32 are determined from the accumulated data of the residual oil in the existing pipe. is there. If this check sheet 30 is used, it is possible to accurately judge with high accuracy whether or not the pipe cleaning is necessary for diversion of the existing pipe. <Advantages of using the cleaning work necessity determination method of the present embodiment> (1) Conventionally, it takes time and a large cost to check the degree of dirt on an existing pipe. The method is to unconditionally clean and reuse the existing pipes without carrying out.

On the other hand, if the judgment method of the present embodiment is used, a simple check sheet 30 that can be used at the site where the existing pipe 9 is installed allows for easy and high accuracy on the spot. It is possible to judge whether or not the pipe cleaning work is required for reuse of the refrigerant communication pipe 9.
Then, by checking the existing refrigerant communication pipe 9 using the check sheet 30, when the residual oil in the existing pipe 9 is not so dirty and cleaning is not necessary, unnecessary pipe cleaning work is omitted. Then, the cost for reusing the pipe 9 can be reduced.

(2) Here, the check sheet 30 is provided with the first part 31 indicating the cleaning necessity reference color for judging the necessity of the pipe cleaning, and the second part 32 indicating the normal oil color.
Is provided on the check sheet 30. Therefore, the user of the check sheet 30 can judge that the pipe cleaning is unnecessary by visually recognizing that the color of the residual oil attached to the sampling portion 33 is lighter than the reference color of the necessity / non-cleaning of the first portion 31. Part 3
By visually recognizing that the color of the residual oil attached to No. 3 is closer to the normal oil color of the second portion 32 than the reference color of the necessity of washing of the first portion 31, it is possible to make the determination of the necessity of pipe washing more reliable. it can.

(3) In the check sheet 30, the first part 3
Since the first and second parts 32 and the sampling part 33 are arranged close to each other, it is easy to compare the cleaning necessity reference color and the normal oil color with the color of the residual oil attached to the sampling part 33. There are some differences depending on the type of refrigerating machine oil used in the existing air conditioner, but in general, the reference color of the first part 31 is a reddish orange color with a slight black tint. ,
The normal oil color of the second portion 32 is a nearly transparent yellow with a reddish color.

<When the residual oil in the existing pipe is extremely dirty> The above-mentioned check sheet 30 can be used to judge the necessity of the pipe cleaning operation based on the color of the residual oil attached to the sampling portion 33. . The user of the check sheet 30 can decide to wash and reuse the existing pipe 9 if the residual oil color is slightly darker than the reference color of the necessity of washing of the first part 31.

However, if the color of the residual oil attached to the sampling portion 33 is very dark and the deterioration of the residual oil is considered to be severe, then as shown in FIG.
The color sample table 40 shown in FIG. 4 will be used to determine whether the pipe 9 can be reused or discarded. That is, it is desirable to prepare the color sample table 40 in addition to the check sheet 30 and use both of them to make a determination regarding the reuse of the existing refrigerant communication pipe 9.

The color sample table 40 shown in FIG.
an Standard Test Method) A sheet on which color codes are printed, and color display sections 41 to 4 are provided on the color codes of "1" to "8".
8 are arranged. The color shown in the color display section 41 is pale yellow, the redness increases as the number of the color code increases, and the color shown in the color display section 44 is orange.
Further, as the number of color codes increases, black appears in addition to red. The color displayed on the color display section 48 is reddish black. The reference color of the necessity of cleaning of the first portion 31 of the check sheet 30 corresponds to the color shown in the color display portion 44 of the color sample table 40.

A person who checks the reuse of the pipe 9 can reuse the pipe 9 without cleaning the pipe when the color of the residual oil corresponds to the colors 1 to 3 of the color sample table 40. When the color of the residual oil corresponds to the color code 4 to 8, the pipe 9 can be reused after washing the pipe,
When the color of the residual oil is darker than the color of the color code 8 and has a strong blackness, it is determined that the pipe 9 cannot be reused. That is, the sampling unit 33 of the check sheet 30
When the color of the residual oil applied to the product is very dark and the deterioration of the residual oil is considered to be severe, the color of the color display portion 40 of the color sample table 40 is compared with the color of the residual oil, and the color of the residual oil is Color of color display 48 (AS
If the color is darker than the TM color code 8), it is decided to discard the existing pipe 9 and install a new refrigerant pipe. This is because when the color of the residual oil is a color deeper than the color of the color display section 48 (the color of the ASTM color code 8) and close to black, the residual oil of the compressor in an existing air conditioner, etc. Abrasion powder due to poor lubrication is the main black component of residual oil,
This is because adhering substances (foreign matter) cannot be often removed even by cleaning the compressor, the refrigerant system parts, and the refrigerant pipe.

<When the compressor of the existing air conditioner does not work> In the past, even when the compressor does not work, if it is not too old, the existing refrigerant pipe should be washed and re-installed. It is being used. However, if the temperature of the inside of the pipe rises due to the leakage of the refrigerant and the compressor motor is burned in, there is a high possibility that oxidation has progressed in the pipe, so even if you clean it Not recommended to use.

Against this, it is effective to check the color of the residual oil by using the color sample table 40 as described above.
When the oxidation in the pipe 9 is progressing, the color of the residual oil is AS
This is because the color should be darker than the TM color code 8. In this way, the above check sheet 30
Using the judgment method using the color sample table 40 and the compressor 1
Even if the inside of the existing pipe 9 is oxidized to such an extent that it cannot be used even if the motor is burned and the pipe is cleaned, it is possible to suppress the problem that the existing pipe 9 is reused only by the cleaning work.

<Modification> (A) Instead of the check sheet 30 and the color sample table 40,
It is also conceivable to make a judgment regarding the reuse of the existing pipe 9 by using litmus paper whose color changes due to acid or alkali. By using a pH analysis tool such as litmus paper, the value of the total acid value of the residual oil in the pipe 9 can be known, and based on this, the possibility of reuse of the pipe 9 and whether or not cleaning is necessary at the time of reuse Can make decisions. In particular, if a pH analysis tool such as litmus paper is used, it is possible to accurately and easily determine the oxidative deterioration of the pipe 9 (generation of hydrofluoric acid, formic acid, hydrochloric acid, etc.).

It is also preferable to add the judgment regarding the reuse of the pipe 9 using the pH analysis tool such as litmus paper to the judgment based on the check sheet 30 and the color sample table 40. In this case, the degree of deterioration of the residual oil is double checked, and the determination regarding the reuse of the pipe 9 becomes more accurate. (B) Check sheet 30 and color sample table 4 of the above embodiment
0 can also be used in an inspection to check whether or not the pipe 9 has been cleaned to a predetermined level after cleaning the pipe 9. After cleaning the pipe 9 that has been judged to be reusable, by using the check sheet 30 and the like to check the degree of contamination in the pipe 9, it becomes possible to use the new air conditioner with more peace of mind.

(C) In the above-mentioned check sheet 30, the first part 31 showing the reference color of necessity of cleaning and the second part showing normal oil color are provided.
Although the part 32 is provided, in addition to these, or the second
It is conceivable to provide the check sheet 30 with a third part indicating the reference color for discarding instead of the part 32. The discard necessity reference color corresponds to the color of the oil that has deteriorated compared to the cleaning necessity reference color of the first part 31, and the residual oil in the pipe 9 has deteriorated so that it cannot be used even after cleaning. It is a reference color for determining whether or not the pipe 9 can be reused by performing a cleaning process. Specifically, the reference color for discard necessity is the color of the color display portion 48 of the color sample table 40 (ASTM).
The color is close to that of the color code 8.

As described above, by using the check sheets showing the cleaning necessity reference color and the disposal necessity reference color, the color sample table 40
It becomes possible to judge whether or not the pipe 9 has to be discarded without using. That is, if the color of the residual oil in the pipe 9 attached to the sampling unit 33 is darker than the reference color for necessity of disposal, the user who uses this check sheet cannot use the pipe 9 even if it is washed. If the color of the sampling unit 33 is judged to be discarded and is darker than the cleaning necessity reference color and is lighter than the disposal necessity reference color, it is judged that the pipe 9 can be reused by cleaning. Will be done.

(D) First in the check sheet 30
Although the part 31 or the second part 32 and the sampling part 33 are integrated, it is possible to use a tool in which the first part 31, the second part 32 and the sampling part 33 are separate bodies. Alternatively, a cotton swab, a waste cloth, or the like corresponding to the sampling unit 33 may be used together with the color sample table 40 to determine the reuse of the pipe 9.

(E) The check sheet 30 and the color sample table 40 can be used to judge whether the existing air conditioner to be removed can be recycled or reused. If the residual oil in the removed air conditioner piping is severely oxidized, it is often impossible to recycle the parts of the existing air conditioner, but if the residual oil is less contaminated, except for the compressor, other This is because it can be reused in some cases.

[0041]

The invention according to claim 1 uses a check tool that can be used at the place where the existing pipe is installed, and judges the availability of the existing pipe from the color of the check tool with the residue of the existing pipe. It is carried out.
This makes it possible to determine the availability of existing pipes using a check tool on-site, and perform unnecessary cleaning work when the inside of the existing pipe is not so dirty and cleaning is not required, Even if the inside of the existing pipe is dirty to the extent that it cannot be used even after cleaning, it is possible to suppress a defect (at least one of the defects) in which the existing pipe is reused by performing only the cleaning work.

In the invention according to claim 2, since the check tool is provided with the second means for indicating the reference color as a reference for judgment, the color of the first means and the second means of the check tool to which a residue is attached are provided. By comparing with the reference color of the means,
It is very easy to judge the possibility of reusing existing pipes. In the invention according to claim 3, since the second means indicates a plurality of standard colors, it is judged whether the existing pipe can be used or whether the pipe cleaning is necessary to use the existing pipe. Not only that, it is possible to make both judgments easily. It is also possible to provide a reference color to confirm that the existing pipe can be used.

In the invention according to claim 4, when the color of the first means with impurities is better than the boundary color, the color of the first means is further compared with the normal color, It will be possible to use the existing pipes with more peace of mind without cleaning. In the invention according to claim 5, by comparing the color of the first means with the first boundary color of the second means, it is possible to judge whether or not the pipe cleaning work is necessary in utilizing the existing pipe. Further, by comparing the color of the first means with the second boundary color of the second means, it is possible to judge whether or not the existing piping can be used.

In the invention according to claim 6, since the first means and the second means of the check tool are arranged close to each other, the color of the first means can be easily compared with the color of the second means to easily connect the existing pipe. You can make decisions about availability. In the invention according to claim 7, since the check tool is a pH analysis tool, when acid or alkali is generated in the residue in the existing pipe, the degree of acid or alkali is judged from the color of the pH analysis tool. Is easy. Then, the degree of deterioration of the residue in the existing pipe can be estimated from the degree of acid or alkali. Based on the degree of deterioration of the residue thus estimated, it is possible to judge the availability of the existing pipe.

[Brief description of drawings]

FIG. 1 is a refrigerant circuit diagram of an air conditioner including a refrigerant communication pipe that is a determination target regarding reuse according to an embodiment of the present invention.

FIG. 2 is a plan view of a check sheet.

FIG. 3 is a plan view of a color sample table.

[Explanation of symbols]

9 Refrigerant communication pipe (existing pipe) 30 Check Sheet (Check Tool) 31 Part 1 (second means) 32 Part 2 (Second Means) 33 Collection unit (first means)

Claims (7)

[Claims] 1. A judgment method for judging the availability of an existing pipe (9) of a device using a refrigerant, which remains inside the existing pipe (9) at a place where the existing pipe (9) is installed. A first step of attaching an object to the check tool (30), and a second step of determining the availability of the existing pipe (9) based on the color of the check tool (30) with the residue. How to judge the availability of existing piping provided. 2. The check tool (30) has a first means (33) for applying the residue, and a second means (31) for indicating a reference color which is a reference for the determination. In the first step, the residue is applied to the first means (33), and in the second step, the color of the first means (33) is compared with the reference color of the second means (31, 32). The method of determining the availability of an existing pipe according to claim 1, wherein the determination is performed by making the above determination. 3. The method for judging the availability of existing piping according to claim 2, wherein the second means (31, 32) of the check tool (30) shows a plurality of reference colors. 4. The second means (31, 32) of the check tool (30) has a normal color that does not require a cleaning process when using the existing pipe (9), and when using the existing pipe (9). The method for judging the availability of an existing pipe according to claim 3, which indicates a boundary color at a boundary where a cleaning process is required. 5. The second means of the check tool is capable of using the first boundary color, which is a standard for judging whether or not the existing pipe (9) needs to be cleaned, and the existing pipe (9). The method for determining the usability of an existing pipe according to claim 3, which indicates a second boundary color that serves as a criterion for determining whether or not the existing pipe is available. 6. The check tool (30) used in the method for determining the availability of an existing pipe according to any one of claims 2 to 5, wherein the first means (33) and the second means ( (31, 32) and a check tool which are arranged in the vicinity of each other and integrated. 7. The check tool is a pH analysis tool whose color is changed by an acid or an alkali. In the first step, the residue is attached to the pH analysis tool, and in the second step, the pH analysis is performed. The method for determining the usability of an existing pipe according to claim 1, wherein the degree of deterioration of the residue is estimated from the color of the tool to make the determination.