JP2000171362A - Sampler for high purity gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress releasing of hydrogen from a metal surface, and to make improvable the gas analyzing accuracy by forming a cylindrical vessel main body having respectively valves on both ends out of copper. SOLUTION: A vessel main body is formed of a copper pipe body 2 having a prescribed length and diameter, domed copper end plates 3 in opening parts of both ends and a bush 4 installed in a through hole 3a of the center, and the sampler 1 is formed of this vessel man body and a valve 7 connected to the bush 4 via a short pipe 5 and a joint 6. In the pipe body 2, the end plates 3 and the bush 4, these contact gas surfaces are polished before joining, adsorption/desorption of impurity is restrained, and joining of respective members is desirably electron beam welding. Thus, hydrogen is not released into sample gas from respective metallic surfaces, so that hydrogen quantity as an impurity in high purity inert gas can be accurately analyzed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sampler for high-purity gas, and more particularly to a sampler used for gas analysis of high-purity gas such as high-purity argon or high-purity nitrogen, and more particularly to a flow-type sampler. .

[0002]

2. Description of the Related Art In order to inspect the quality of high-purity gas products such as high-purity argon and high-purity nitrogen having an impurity level of ppm to ppb, these gases are collected by a sampler at a manufacturing place or a place where these gases are used. It is carried to the place where the gas analyzer is installed.

[0003] As a sampler for collecting such a high-purity sample gas, a flow-through sampler made of stainless steel has been conventionally used, and the contact surface with the sample gas has an impurity component from the metal surface to the sample gas. Various treatments have been applied to prevent the release of methane.

For example, after cold rolling and drawing, a bright annealing heat treatment is performed by heating to about 1080 ° C. in a reducing atmosphere such as ammonia, hydrogen or a mixed gas of hydrogen and nitrogen.
(Bright Anneal) treatment, anodizing treatment in an electrolytic solution such as sulfuric acid or phosphoric acid, so as to preferentially dissolve (ionize) minute projections on the metal surface by electrochemical reaction.
To make the metal surface smooth and glossy
P (Electro-Polish) treatment, 0P treatment for forming an oxidation passivation film on a metal surface, CRP treatment for forming a chromium-rich passivation film, and the like are performed.

[0005]

By performing the various treatments described above, the adsorption of impurities on the metal surface and the release of the impurities adsorbed on the metal surface into the sample gas are almost completely prevented. However, hydrogen present in the metal on the metal surface portion may be released from the metal surface into the sample gas, which may cause a large difference in the analysis result of hydrogen.

For example, when the sample gas collected in the sampler was analyzed immediately after collection, the hydrogen component was 1 ppb or less, whereas when analyzed one week after collection, the hydrogen component was several tens to several In some cases, it increased to 100 ppb.

Accordingly, the present invention provides a high-purity gas sampler that suppresses the release of hydrogen from the metal surface during the period from sampling (sampling) to analysis of a sample gas and improves the accuracy of gas analysis. It is intended to be.

[0008]

In order to achieve the above object, a high-purity gas sampler according to the present invention is a high-purity gas sampler having valves at both ends of a cylindrical container body. The main body is formed of copper.

Further, in the sampler for high-purity gas of the present invention, the container main body includes a copper tube, a copper end plate mounted at both ends of the tube, and a through hole provided at the center of the end plate. It is characterized by being formed by welding a copper bush attached to the hole and connected to the valve. Further, the valve and the connecting auxiliary member are also formed of copper.

[0010]

1 and 2 show an embodiment of a sampler for high-purity gas according to the present invention. FIG. 1 is a sectional view of a main part, and FIG. It is a piping system diagram for demonstrating the procedure of.

First, the shape of the sampler 1 should be designed so that it can be formed in the same shape and the same capacity as a conventional stainless steel sampler, for example, a flow-type sampler, and have the same pressure resistance. Can be. That is, a copper pipe 2 having a predetermined diameter and length, and the pipe 2
Dome-shaped end plate 3 made of copper attached to the openings at both ends
And a container body formed by a bush 4 mounted in a through hole 3a provided at the center of the end plate 3, and connected to the bush 4 via a short pipe 5 and a joint 6, which are auxiliary connecting members. And the valve 7.

The copper forming the tube 2 may be selected from copper which can be easily processed into a tube and does not cause hydrogen embrittlement even when heated in a reducing atmosphere. For example, JIS C12
Phosphorus-deoxidized copper specified in No. 20 is preferred in terms of its performance and cost. The copper forming the head plate 3 may be selected from copper which can be easily drawn into a dome shape and does not cause the hydrogen embrittlement. For example, JIS C1020
Is preferred in terms of performance and cost. Since the bush 4 has a small gas contact surface area and is less affected by hydrogen release, an appropriate copper material can be selected. For example, the bush 4 can be made of the above-mentioned phosphorous deoxidized copper.

It is preferable that at least the gas contact surfaces of the tubular body 2, the end plate 3, and the bush 4 are polished before joining them. For example, by performing the # 400 buffing to keep the surface roughness at about 10 μm, the adsorption and desorption of impurities on the gas contact surface can be suppressed.

The members can be joined by electron beam welding, TIG welding, brazing with silver brazing, or the like.
Among them, electron beam welding is the most suitable because it can join with the joining surface as it is without performing groove processing, and high joining strength and adhesion can be obtained.

On the other hand, the short pipe 5 and the valve 7 can be made of ordinary stainless steel because they are considered to have a small gas contact area and a small amount of hydrogen release. By forming with, it is possible to further reduce the influence of hydrogen. Although the bush 4 and the valve 7 can be directly connected without passing through the short pipe 5,
In consideration of productivity and maintainability, it is preferable to provide the short pipe 5 as described above.

Such a flowable sampler 1 made of copper is:
It can be used in the same manner as a conventional stainless steel sampler. That is, as shown in FIG. 2, one of the valves 7 of the copper flow-type sampler 1 is connected to a sample gas 13 via a sampling pipe 13 composed of a small-diameter and short pipe having a discharge valve 11 and a pressure gauge 12. By connecting the flow meter 15 to the other sample valve 7 while connecting it to the sample gas extraction valve 14 of the source, the sample gas can be sampled in the same manner as in a conventional flow-type sampler.

By forming at least the tube 2, the end plate 3, the bushing 4 and the like forming the container body of the sampler 1 from pure copper-based copper, hydrogen is released from the metal surface into the sample gas. , The amount of hydrogen contained as an impurity in a high-purity inert gas used for semiconductor manufacturing, such as high-purity gas having an extremely low allowable hydrogen concentration, particularly argon or nitrogen, can be accurately analyzed. .

Even when hydrogen is not a gas to be analyzed, it is extremely effective for analyzing a sample gas containing a component which reacts with hydrogen. Further, since there is no need to perform a special inner surface treatment unlike a conventional stainless steel sampler, the manufacturing cost is low.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A cylinder diameter of 165 mm, a length of 530 mm and a capacity of 10
A liter copper sampler was made. The tube and bush are made of JIS C1220 phosphor deoxidized copper, and the end plate is made of JIS
Using oxygen-free copper of C1020, the inner surface was buffed to reduce the surface roughness to about 10 μm, and then joined by electron beam welding. The short pipe was made of stainless steel, and the valves and fittings used were commercially available high-purity gas-compatible products. As a comparative product, a conventional stainless steel sampler which had been subjected to various inner surface treatments was prepared. As the sample gas, an ultra-high-purity nitrogen gas having a hydrogen allowance of less than 1 ppb is used, and the gas analysis after sampling has a hydrogen detection limit of 1 ppb.
This was performed under the same conditions using a gas chromatograph with a photoionization detector of less than.

First, the sampler 1 was connected as shown in FIG. 2, and a sample gas was sampled into the sampler 1 in the following procedure. That is, the valve 7 on the outlet side of the sampler 1
The flowmeter 15 is connected to the
Is slightly opened to slightly release the sample gas, the upstream side of the sampling pipe 13 with the release valve 11 fully opened is connected, and the downstream side of the sampling pipe 13 becomes the inlet side of the sampler 1. Connected to valve 7.

To purge the sampling pipe 13 system, the valves 7, 7 on both sides of the sampler 1 are opened, the discharge valve 11 is closed, and the flow rate is adjusted by the sample gas extraction valve 14, so that the flow rate of the sample gas is reduced per minute. It carried out by setting to 10 liters and leaving it to stand for 5 minutes. In addition, the flow rate of the sample gas was confirmed by the flow meter 15.

Next, the valves 7, 7 of the sampler 1 are connected to the outlet side,
Close the inlet side in order, pressurize the inside of the pipe until the pressure becomes the same as that of the sample gas source, close the sample gas outlet valve 14, and conduct an airtightness test to check the airtightness of the connection part by the pressure gauge 12 with the presence or absence of pressure drop. went.

After the airtight test is completed, the discharge valve 11 is opened, the gas in the pipe is released, and the discharge valve 11 is immediately closed to release the gas. The sample gas extraction valve 14 is opened and the inside of the pipe is the same as the sample gas source. A purge operation of performing a pressure filling operation of filling a sample gas until a pressure is reached, that is, a so-called pressure purge, was repeated 10 times. After completion of the pressure purge, the valves 7, 7 of the sampler 1 were opened in the order of the outlet side and the inlet side, and the sample gas was allowed to flow through the sampler 1 at a rate of 20 liters per minute, thereby performing a flow purge for 20 minutes.

After the end of the flow purge, the valve 7 on the outlet side of the sampler was closed, the sample gas extraction valve 14 was fully opened, and the sample gas was filled into the sampler 1 by allowing it to stand for 5 minutes. The filling state of the sample gas was confirmed by the pressure gauge 12.

After the filling is completed, the sample gas extraction valve 14 is closed, both valves 7 and 7 of the sampler are closed, and the discharge valve 11 is opened to release the gas in the sampling pipe 13. The flow meter 15 was removed from the sampler 1, and after checking the airtightness of the valves 7, 7 on both sides of the sampler, sealing caps were attached to both ends to complete the sampling operation. The analysis of the sample gas in the sampler after sampling was performed as usual by the operation set in the analyzer.

Table 1 shows the change over time of the hydrogen gas concentration [ppb] with respect to the elapsed time after sampling.
1 "is below the detection limit).

[0027]

[Table 1]

[0028]

As described above, according to the high-purity gas sampler of the present invention, it is possible to suppress an increase in the impurity component concentration after sampling the sample gas, thereby improving the accuracy of gas analysis. In addition, gas analysis after sampling can be performed with a margin, so that the burden of gas analysis can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part showing one embodiment of a sampler for high-purity gas of the present invention.

FIG. 2 is a system diagram showing a pipe connection state when sampling a high-purity gas.

[Explanation of symbols]

1 ... sampler, 2 ... tube, 3 ... head plate, 4 ... bush,
5 Short pipe, 6 Joint, 7 Valve, 13 Sampling pipe, 14 Sample gas extraction valve

Claims (3)

[Claims] 1. A high-purity gas sampler having valves at both ends of a cylindrical container body, wherein at least the container body is formed of copper. 2. The container main body is connected to the valve by being mounted on a copper tube, a copper end plate mounted on both ends of the tube, and a through hole provided at the center of the end plate. 2. The sampler for high-purity gas according to claim 1, wherein said sampler is formed by joining a copper bush to said bush by welding. 3. The sampler according to claim 1, wherein the valve is made of copper.