JP3837523B2 - Pipe inner surface treatment monitoring method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a process for forming an oxide film on an inner wall surface of a high-purity gas pipe or the like used in semiconductor element manufacturing, and relates to an oxide film forming process measurement of a pipe and an oxide film forming process method using the same. .
[0002]
[Prior art]
In semiconductor processes, the use of high-purity gas is indispensable with high integration. Therefore, semiconductor gas piping used for transporting high-purity gas is also required to have low degassing, particle reduction, high corrosion resistance, and the like. Therefore, stainless steel pipes frequently used in these semiconductor gas pipes are also subjected to inner wall polishing by electrolytic polishing and passivation treatment (CRP) with chromium oxide. In the treatment using the characteristics of ozone that is more active than oxygen and can greatly reduce the treatment temperature, the following has been proposed.
[0003]
A high-temperature and low-concentration ozone treatment method in which treatment is performed at a temperature of 200 ° C. in an ozone-oxygen mixed gas containing 5 to 10% ozone (see Patent Document 1 below)
[0004]
A low-temperature, high-concentration ozone sealing treatment method in which an ozone-oxygen mixed gas containing 50% or more of ozone is sealed in a pipe and processed at a temperature of 60 ° C. or lower (see Patent Document 2 below)
[0005]
An ozone flow-down treatment method in which an ozone-oxygen mixed gas containing 12% ozone flows down into a pipe and is treated until the difference in concentration between the outlet and the inlet of the pipe is 0.01% or less (see Patent Document 3 below)
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 5-287396 [Patent Document 2]
JP-A-9-195031 [Patent Document 3]
JP 2001-279423 A
[Problems to be solved by the invention]
Conventionally, there are only a few examples that provide judgment criteria for the completion of treatment in the treatment of forming chromium oxide on the inner wall surface of a stainless steel tube using ozone, and the difference between the ozone concentration at the pipe outlet and the ozone concentration flowing down is 0.01% or less. (Patent Document 3 above) and the increase in pressure in the piping filled with ozone stopped because the ozonolysis stopped due to the completion of passivation.
[0008]
However, there was a problem with this method. That is, when there is an insufficiently processed part in the pipe, it is impossible to identify which part of the pipe.
[0009]
When constructing long pipes in production lines such as factories, various pipes are welded and joined, and piping parts such as valves and fittings (in this specification, these pipes, valves and fittings are referred to as “processed parts”. Is metal sealed. In the piping, there are various surface states and material compositions such as differences in materials constituting the tubes and piping parts and welds where the chromium oxide film is lost. Since the ozone treatment is an oxidation treatment for passivating these surfaces, the time required for passivation varies greatly depending on the material and surface condition. Therefore, the time required for ozone treatment of the piping is not uniform at each location in the piping. In some cases, the passivating process is mostly completed, but a part of it is incomplete.
[0010]
In the conventional measurement method, the average decomposition rate of ozone over the entire pipe is measured. For example, measurement of the ratio of ozone concentration at which ozone concentration flows down at the pipe outlet (Patent Document 3 above), measurement of pressure increase due to ozone decomposition of the pressure of the pipe filled with ozone (Patent Document 2), and the like.
[0011]
In these methods, there is a problem that it is impossible to identify the location even if there is an untreated location that partially decomposes ozone in the piping.
[0012]
If it is possible to identify the location in the pipe where a difficult-to-passivate part can be identified, it can be replaced with a part that has been passivated, thereby shortening the time required for passivating the pipe. be able to.
[0013]
In particular, when transporting high-concentration ozone gas, safety is also involved. If there is a small amount of untreated parts in the piping for high-concentration ozone gas, even if other pipe parts are completely passivated, ozone decomposes and heats up in the untreated parts, and the heat decomposes ozone. Ozone self-decomposition that is induced is repeated. Therefore, it may be a problem that high-concentration ozone cannot be transported or, in some cases, an explosion factor. Therefore, identification of the unprocessed part is indispensable for improving safety.
[0014]
The present invention pays attention to the above points, and provides a method for identifying an incomplete part of processing in order to perform complete processing on the entire inner surface even after piping construction, and provides a judgment criterion for processing completion. An object is to provide a method for improving the safety of piping.
[0015]
[Means for Solving the Problems]
In the passivating process of the inner wall of the pipe, in order to identify the insufficient passivated part in the pipe, first ozone is sealed in the pipe for a certain period of time, then the ozone in the pipe is purged and the ozone flowing out from the outlet Concentration is measured in time series. In the part where the passivation is insufficient in the pipe, the decomposition of ozone is progressing, so the ozone concentration is less in the measured time-series concentration distribution than the part where the passivation is sufficient. Sites of insufficient passivation can be identified.
[0016]
Further, based on the analysis result, when the degree of decomposition of the enclosed ozone gas is equal to or less than the determination standard over the entire piping area, it can be determined that the passivation treatment process over the entire piping area has been completed.
[0017]
Embodiment
FIG. 1 is a configuration diagram showing an inner surface treatment apparatus for piping showing an embodiment of the present invention. In the above processing apparatus, a valve (A), an ozone concentration measuring instrument (A), a flow rate controller and an ozone generator are connected in this order on the inlet side of the pipe to be processed, and the valve (B) and ozone are connected on the outlet side. Concentration meter (B) is connected. Further, a flow rate regulator (B) and a valve (C) for purging the pipe with oxygen are connected to the pipe inlet.
[0018]
The piping contains a metal whose inner wall surface forms a passive oxide film, and the passive oxide film is an oxide film of iron, titanium, alumina, nickel, chromium, or the like. The ozone generator may be a mixed gas containing ozone or ozone water containing ozone. Further, what is used for purging may be a mixed gas containing ozone, ozone water containing ozone, nitrogen, oxygen, or an argon rare gas.
[0019]
The result of measuring the ozone concentration at the inlet and outlet of the pipe is sent to the data processing device. The ozone generator supplies an ozone-oxygen mixed gas, and the ozone concentration is 27 wt%. The ozone concentration may be other values.
[0020]
In the measurement method of the present invention, purge gas is introduced from the inlet to push out ozone gas in the piping. As a result, uncertainty arises due to the mixture of purge gas and ozone gas in the piping. Therefore, the influence of uncertainty due to the mixture of ozone and oxygen was investigated.
[0021]
Figure 6 shows the effect of extruding oxygen in the pipe and examining the effect of extruding the gas in the pipe. The sample is a pipe having a length of 8 m and an outer diameter of 12.7 mm. The inner wall of the pipe is previously passivated with ozone. This pipe was filled with oxygen, and then ozone gas (concentration 700 g / m3) was flowed from the inlet at a constant flow rate, and the ozone concentration at the outlet was measured. At this time, the rising of the concentration at the outlet, that is, the time for switching from oxygen to ozone was 1.2 minutes as shown in FIG. Ideally, this rise should be zero, but there is some blurring due to mixing when pushing out the oxygen in the pipe by ozone.
[0022]
As shown in Fig. 6, it took 17 minutes for the ozone to flow from the inlet to the outlet, so the position resolution ambiguity due to gas mixing when pushing out oxygen in the pipe by ozone was 7%. It is.
This result is only an example, and the blur due to gas extrusion at the time of purging can be further improved by the purge gas flow rate according to the pipe diameter, the type of purge gas, the temperature control of the pipe, and the like.
[0023]
[Example 1]
The pipe to be treated is a SUS304 stainless steel pipe having an outer diameter of 1/2 inch and a length of 6 m. The inner surface treatment is electrolytic polishing. When the ozone-oxygen mixed gas was flowed and the total amount reached 36L, 142L, and 244L, the ozone concentration distribution in the piping was measured by the concentration measurement method described below.
[0024]
That is, after flowing a predetermined amount of ozone, the valves (A) and (B) were simultaneously closed, and the ozone was left in the pipe to be treated for 110 minutes. The piping temperature was kept at 23 ° C. Thereafter, the valves (B) and (C) were opened at the same time, and 50 cc of oxygen was allowed to flow through the flow rate controller (B) per minute to purge the ozone in the piping. (The outlet concentration at this time was measured with an ozone concentration recorder (B). The measurement results were recorded in time series with a data processor.
[0025]
From the outlet, ozone that has accumulated at each point in the pipe and decomposed according to the degree of passivation on the spot is sequentially discharged. FIG. 2 shows the time-series data of these concentrations as the distribution of the ozone decomposition rate according to the distance from the entrance of the pipe in the data processing device. Here, the ozone decomposition rate is obtained by subtracting from 1 by taking the ratio of the outlet concentration to the inlet concentration by the ozone concentration measuring device (A). That is, the ozone decomposition rate is 1 when the outlet concentration is 0%, and the ozone decomposition rate is 0 when the outlet concentration is equal to the inlet concentration.
[0026]
From FIG. 2, it can be seen that the ozone decomposition rate decreases from the entrance of the piping, the passivation proceeds from the entrance, and the ozone decomposition rate of the entire piping decreases as the ozone flow time increases.
[0027]
Completion of the processing of the pipe can be determined when the ozonolysis rate is equal to or lower than the determination reference value over the entire pipe.
The criterion value is 1% when the piping is at room temperature and the sealing time is about 2 hours or less.
However, when the piping exceeds room temperature, it is necessary to correct the influence of ozone self-decomposition and raise the judgment value. The self-decomposition of ozone has temperature dependence, and when the temperature is raised from 25 ° C. to 40 ° C., the self-decomposition rate becomes more than twice. In this case, it is necessary to double the judgment value.
Further, when the sealing time is extremely long, it is necessary to correct ozone self-decomposition even when the piping temperature is room temperature. For example, when ozone with a concentration of 50 vol% is sealed for 80 hours, the self-decomposition rate at 25 ° C. is 10%, so the determination value is 10%.
[0028]
In this embodiment, oxygen is purged with a constant flow rate, but ozone from an ozone generator can be used instead of oxygen. In short, it is a gas that can push out ozone in the piping, and other gases can be used if they do not react with the enclosed ozone gas.
In addition, when ozone water is sealed in the pipe, a liquid such as water or ozone water can be used for purging.
[0029]
When ozone is used as the purge gas, the oxygen purge line (flow rate regulator B and valve C) is not required.
[0030]
When the ozone gas is a purge gas, the determination of passivation by the present method can be made as appropriate during the ozone treatment by simply opening and closing the valve, so that the apparatus can have a simple structure.
[0031]
Further, it is not necessary to flow purge gas at a constant flow rate in purging, and it may be variable depending on circumstances. For example, in a long pipe, control is performed to measure the concentration distribution in detail by increasing the purge gas flow rate and reducing the flow rate at the required location so that ozone gas in the piping portion that does not need to be specifically examined for passivation is quickly discharged. It is also possible to do. Such control is possible by performing time control of the flow controller and time-series recording of the outlet ozone concentration in synchronization with the data processing device.
[0032]
In this embodiment, the confinement time is 110 minutes, but can be changed according to the structure of the pipe and the degree of passivation. Longer times may be used to investigate precisely.
[0033]
The measurement time by purging needs to be sufficiently shorter than the ozone sealing time in the piping. The recommended ratio is 10 or more when the measurement time is 1. Moreover, the measurement time by purging needs to be made small to the extent that the ozone purged in the piping during the measurement does not decompose so much and does not affect the measurement. It is necessary to reduce the ozone sealing time in the pipe to such an extent that the influence of the mutual diffusion of ozone and oxygen in the pipe becomes large and the identification of the ozone decomposition position is not hindered.
[0034]
[Example 2]
FIG. 3 shows a case where the pipe to be treated is a Ti pipe having an outer diameter of 12.7 mm and a length of 4 m. The confinement time is 110 minutes. As with SUS304, passivation proceeds from the entrance, so the ozone decomposition rate falls from the entrance.
[0035]
[Example 3]
FIG. 4 shows a case where an A5052 aluminum alloy pipe having an outer diameter of 12 mm and a length of 3 m is used as the pipe to be treated. The surface treatment is a precision cleaning after wet chemical polishing. In this case as well, passivation proceeds from the entrance.
[0036]
[Example 4]
The main part of the pipe to be treated was a titanium pipe (outer diameter 1/2 inch, length 6 m), and one stainless steel part was provided in the middle. Stainless steel pipes were connected to both ends of the titanium pipe, and valves were connected.
[0037]
For the passivation treatment measurement, the ozone concentration enclosed in the pipe is 690 g / m 3, the sealing time is 2 hours, and the purge gas after the sealing is ozone. FIG. 5 shows the result of measuring the ozone concentration that exits from the outlet during purging.
[0038]
In FIG. 5, the portion where the ozone concentration is reduced corresponds to the position where the ozone is in contact with the stainless steel part during encapsulation. Since the portion where the ozone concentration is decreased is not sufficiently passivated, it can be seen that the inner wall treatment of the stainless steel part connected in the middle of the titanium tube is incomplete.
[0039]
【The invention's effect】
According to the present invention, since the incomplete part of the passivation process on the inner surface of the pipe can be identified, the degree of completion of the pipe process can be evaluated. Moreover, it can be used after the piping construction in the factory, and the inner surface treatment of the piping can be performed while grasping the degree of completion of the processing.
[Brief description of the drawings]
1 is a schematic diagram of a measuring apparatus and a processing apparatus in the present invention. FIG. 2 is a progress diagram of passivation associated with ozone treatment in a SUS304 pipe. 4) Passivation progress diagram with ozone treatment in A5052 aluminum alloy tube [Fig. 5] Passivation progress diagram with ozone treatment in piping made of Ti and stainless steel [Fig. 6] Mixing of purge gas and ozone gas in piping Survey chart of

Claims (6)

In a passivation monitoring method in the step of applying a passivation treatment with ozone to the inner surface of a part to be processed consisting of a pipe , a valve or a joint, ozone is sealed in the part for a certain period of time, and then the ozone in the part is purged. A passivating monitoring method characterized by monitoring the progress of the passivating process by measuring the concentration of ozone flowing out from the outlet of the component in time series.   The passivation monitoring method according to claim 1, wherein in the part, an insufficiently passivated portion is identified by monitoring the ozone concentration. The passivation monitoring method according to claim 1, wherein the passivation in the component is completed by detecting that the decomposition rate of the encapsulated ozone is below a criterion in every part of the component. Passivation monitoring method characterized by confirming. In a passivation monitoring device in a step of applying a passivation treatment with ozone to the inner surface of a component to be processed consisting of a pipe , a valve or a joint, a device for sealing ozone in the component for a certain period of time, and purging the ozone in the component A passivation monitoring apparatus characterized by monitoring the progress of the passivation process by providing the apparatus and a device for measuring the concentration of ozone flowing out from the outlet of the component in time series. 5. The passivation monitoring device according to claim 4 , wherein a part where the passivation is insufficient is identified in the component by monitoring the ozone concentration. 5. The passivation monitoring device according to claim 4 , wherein the passivating in the component is completed by detecting that the decomposition rate of the enclosed ozone is below the determination standard throughout the component. Passivation monitoring device characterized by checking.

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