High-purity gas purity testing and analyzing system and testing method thereof

Abstract

The invention discloses a high-purity gas purity testing and analyzing system and a testing method thereof.The high-purity gas purity testing and analyzing system comprises a molecular pump, a cold trap, a testing cavity, connecting pipelines and a gas sampler which are sequentially connected, a baking device is arranged on the outer side of the testing cavity, and the connecting pipelines comprise the first connecting pipeline and the second connecting pipeline which are connected in parallel; any connecting pipeline is provided with an MFC flow meter, the first connecting pipeline and the second connecting pipeline are both provided with valves, and the test cavity is connected with a residual gas analyzer and a high vacuum gauge. In the invention, the components of the mixed gas can be quantitatively analyzed and monitored through the gas analyzer, and the pressure of 10 <-7 > Pa magnitude is measured through the vacuum gauge, so that the purity of the high-purity helium working medium of the GM refrigerating machine system is quantitatively analyzed, the purity of helium output by the helium compressor is monitored, and the replacement cycle of the adsorber can be confirmed.

Description

Technical Field

[0001] The present invention relates to the technical field of testing and analyzing systems, and more specifically to a testing and analyzing system for purity of high-purity gas and a testing method thereof. Background Art

[0002] High-purity gas generally refers to gas with a purity equal to or higher than 99.999%. High-purity gas has a wide range of applications and plays a vital role in the semiconductor industry, vacuum technology, and low-temperature superconductivity.

[0003] Helium is a colorless, odorless, tasteless, non-flammable, slightly soluble in water, and chemically stable inert gas. It is the most difficult gas to liquefy among all gases. Its boiling point at normal pressure is -268.9℃, close to absolute zero. After liquefaction, it has the characteristics of small surface tension, strong thermal conductivity, and low viscosity. Therefore, it is often used in low-temperature GM refrigerators as a refrigeration cycle working fluid. High-purity helium refers to helium with a purity of more than 99.999% and a total impurity gas content of ≤10ppm. The impurity gases in high-purity helium are mainly Ne, H2O, N2, O2 and other gases. The H2O content in high-purity helium is usually tested by electrolysis, dew point method and cavity ring-down spectroscopy, and the remaining impurity gases are tested by helium ionization gas chromatography.

[0004] The GM refrigerator system consists of a helium compressor, a helium tube, and an expander. The system requires that the purity of the helium working fluid reach more than 99.999%. When the purity of the system does not meet the standard, it may cause abnormal friction noise in the expander, degradation of the performance of the cold storage material, and other undesirable phenomena, resulting in the performance degradation of the GM refrigerator. In the refrigerator system, the helium compressor provides high-purity and high-pressure helium to the expander. The low-pressure helium is pressurized by the compressor pump and becomes an oil-gas mixture. The oil and gas are separated by the oil filter, and then the impurity gas such as water vapor is filtered through the adsorber to form more than 99.999% high-purity helium. The adsorber is usually made of an adsorbent material with developed pores, but the adsorber will reach saturation and lose its filtering effect after long-term operation. Therefore, the adsorber of the compressor needs to be replaced regularly to ensure the purity of the gas. In the existing technology, the replacement evaluation method of the adsorber is usually the cumulative operating time of the compressor, and it is impossible to quantitatively evaluate the outlet gas purity of the adsorber.

[0005] Residual Gas Analyzer (hereinafter referred to as RGA), RGA requires the environmental vacuum to reach below 10-4mbar to work, so it is often used to monitor and analyze the gas composition and gas concentration in a high vacuum environment. Patent document with patent publication number CN109799315 A discloses a system that is connected to the vacuum chamber to be tested through a system fine-tuning valve, and the working pressure of RGA is expanded from atmospheric pressure to ultra-high vacuum, providing a residual gas analysis system applicable to a wide pressure range, solving the problem that the residual gas analyzer cannot analyze the gas composition under high pressure.

[0006] The patent document with the patent publication number CN 116298119 A discloses a helium purity analysis device and analysis method, including a sampling tube, a detection tube, a recovery tube, a sensor, a combustion device, a hydrogen tube and a mixed gas tube. Different gas sensors are arranged in the detection tube to test the content of different gases, and the water, oxygen, nitrogen, and carbon and hydrogen impurity contents in the helium can be measured at the same time to achieve quantitative analysis. The sample gas, hydrogen and nitrogen-oxygen mixed gas are mixed and burned, and then the carbon and hydrogen sensor, oxygen sensor, nitrogen sensor and humidity sensor detect the nitrogen, oxygen and water contents in the helium to achieve the purity evaluation of the helium.

[0007] However, this solution can only detect the content of nitrogen, oxygen and water through the combustion test, and cannot evaluate the trace elements in helium. Therefore, it cannot be used to test the purity of high-purity helium. The GM refrigerator system requires the purity of helium to reach more than 99.995%, and the test accuracy of the gas is extremely high, and a quantitative evaluation of the trace elements in the helium is required. At the same time, the impurity gas in the helium of the long-term circulation operation of the system cannot be confirmed in advance, and the installation of the corresponding sensor is likely to cause incomplete test results. Summary of the invention

[0008] The technical problem to be solved by the present invention is how to achieve quantitative analysis of the purity of high-purity helium working medium in a GM refrigerator system.

[0009] The present invention solves the above technical problems through the following technical means: a high-purity gas purity testing and analysis system, including a molecular pump, a cold trap, a test chamber, a connecting pipeline, and a gas sampler connected in sequence, a baking device is provided on the outside of the test chamber, the connecting pipeline includes a first connecting pipeline and a second connecting pipeline connected in parallel, an MFC flowmeter is provided on any of the connecting pipelines, valves are provided on the first connecting pipeline and the second connecting pipeline, and a residual gas analyzer and a high vacuum gauge are connected to the test chamber.

[0010] As a preferred technical solution, the MFC flow meter range is 2-10 sccm.

[0011] As a preferred technical solution, the connecting pipeline is connected to a four-way valve, a self-sealing joint is fixedly connected to the fourth joint of the four-way valve, and is detachably fixed to the gas sampler through the self-sealing joint.

[0012] As a preferred technical solution, the first connecting pipeline includes a bellows, the bellows is connected to the self-sealing joint through the first joint of the four-way valve, and a hand valve is provided on the bellows.

[0013] As a preferred technical solution, an MFC flowmeter and a control valve are provided on the second connecting pipeline, and the second connecting pipeline is connected to the second joint and the self-sealing joint of the four-way valve.

[0014] As a preferred technical solution, a pressure relief valve is connected to the third joint of the four-way valve.

[0015] As a preferred technical solution, control valves are provided both upstream and downstream of the MFC flowmeter.

[0016] As a preferred technical solution, the baking device is wrapped around the outside of the test cavity.

[0017] A method for testing a high-purity gas purity test and analysis system comprises the following steps:

[0018] S1. Adjust the system background vacuum to -10Torr level through molecular pump, cold trap and baking device;

[0019] S2. Measure the background residual gas partial pressure through the residual gas analyzer and maintain it for a set time;

[0020] S3, disconnect the gas sampler, monitor the background residual gas partial pressure of the test chamber and establish a background residual gas partial pressure benchmark;

[0021] S4, sampling from a high-purity helium cylinder, a compressor or a refrigerator through the sampling end of the gas sampler and connecting it to the fixed end of the gas sampler;

[0022] S5. Inject the gas to be tested at a set flow rate into the test system through the MFC flowmeter, and monitor the residual gas partial pressure in the test chamber through the residual gas analyzer;

[0023] S6. The residual gas partial pressure of the test chamber and the background residual gas partial pressure benchmark data are processed by using a differential method to obtain the proportion of different types of gases.

[0024] As a preferred technical solution, in S1, the H2O partial pressure in the test chamber is reduced to the level of <-10Torr by a cold trap, and the H2O partial pressure in the test chamber is further reduced by a baking device, while the H2 partial pressure in the test chamber is reduced to the level of <-10Torr.

[0025] The beneficial effects of the present invention are:

[0026] (1) In the present invention, the H2O partial pressure in the test chamber is reduced to the level of <-10 Torr by a cold trap, and the H2O partial pressure in the test chamber is further reduced by a baking device, and the H2 partial pressure in the test chamber is reduced to the level of <-10 Torr at the same time, so that the residual gas partial pressure in the test chamber is controlled at the level of <-10 Torr, and a small flow MFC is used to achieve the gas partial pressure of 10- 4 Torr level, thus achieving the requirement of 99.999% purity test of helium. The gas analyzer can quantitatively analyze and monitor the components of the mixed gas, and the vacuum gauge can measure 10 -7 The pressure of Pa level can realize the quantitative analysis of the purity of high-purity helium working fluid in GM refrigerator system, monitor the purity of helium output by helium compressor, and then confirm the replacement cycle of adsorber.

[0027] (2) In the present invention, both ends of the gas sampler are provided with a detachable self-sealing joint structure to ensure that the sampler will not be contaminated by external gas during the disassembly and assembly process, and can be flexibly used to achieve sampling in different environments; through online sampling at the sampling end of the gas sampler, the GM refrigerator system can complete the helium sampling of the helium compressor without stopping, which is suitable for harsh environments that require long-term non-stop operation and maintenance.

[0028] (3) In the present invention, a small-flow mass flow meter MFC is used to maintain the partial pressure of the gas to be tested at the order of -4 Torr, resulting in a significant magnitude difference from the partial pressure of the background gas, thereby achieving the high-purity gas test accuracy requirements and achieving a constant flow rate for a long time to stably inject the gas to be tested, thereby ensuring the accuracy of the test data. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of the overall structure provided by an embodiment of the present invention;

[0030] Figure numbers: 1. Dry pump; 2. Molecular pump; 3. Test chamber; 4. Residual gas analyzer; 5. High vacuum gauge; 6. Hand valve; 7. Bellows; 8. MFC flow meter; 9. Four-way valve; 10. Pressure relief valve; 11. Self-sealing joint; 12. Gas sampler; 13. Cold trap; 14. Baking device. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] See also Figure 1A high-purity gas purity test and analysis system comprises a dry pump 1, a molecular pump 2, a cold trap 13, a test chamber 3, a connecting pipeline, and a gas sampler 12 connected in series. The test chamber 3 is connected with a residual gas analyzer 4 and a high vacuum gauge 5. The residual gas analyzer 4 is used to quantitatively test the residual gas partial pressure of the background of the test chamber 3 and the partial pressure of the gas to be tested. The high vacuum gauge 5 is used to test the residual gas partial pressure of the test chamber 3 and the residual gas partial pressure of the test chamber 3. -7 The test chamber 3 is provided with a baking device 14, which is wound around the outside of the test chamber 3 and bakes the test chamber 3 by external heating to evaporate the water vapor adsorbed on the inner wall of the test chamber 3, thereby reducing the water content and background vacuum of the system.

[0033] The dry pump 1 is a pre-stage pump of the molecular pump 2, and is used to assist the test system of the molecular pump 2 to establish a high vacuum environment. The molecular pump 2 is the main vacuum pump of the test system, and is used to achieve an ultra-high vacuum background environment of the system. The test cavity 3 is a stainless steel vacuum chamber, and the cold trap 13 is used to assist the molecular pump 2 in extracting water vapor in the test cavity 3 to reduce the water content and background vacuum of the system; wherein the connecting pipeline includes a first connecting pipeline and a second connecting pipeline connected in parallel;

[0034] One end of the first connecting pipeline is connected to the test chamber 3, and the other end is connected to the gas sampler 12. The first connecting pipeline includes a bellows 7, which is used to connect the gas sampler 12 and the test chamber 3 in the test system to evacuate the gas sampler 12. The bellows 7 is also provided with a hand valve 6, which is used to control the on-off of the pipeline. The bellows 7 is connected to a self-sealing joint 11 through a four-way valve 9. The self-sealing joint 11 and the gas sampler 12 are detachably fixed. The four-way valve 9 is a commercially available KF25 four-way valve. Four cross-shaped and connected joints are arranged in the circumference thereof, namely, the first joint, the second joint, the third joint, and the fourth joint. The first joint of the four-way valve 9 is fixedly connected to the bellows 7, and the fourth joint is fixedly connected to the self-sealing joint 11. The gas sampler 12 is a commercially available double-end self-sealing joint, including a detachably connected sampling end and a fixed end. The sampling end is a sealing female head, and the fixed end is a sealing male head. The sealing female head can match the interface forms of all the devices to be sampled, so that the entire test system will not be polluted when the sampler is disassembled;

[0035] An MFC flowmeter 8 is provided on the second connecting pipeline. The MFC flowmeter 8 is used for quantitative injection of the gas to be tested to achieve long-term constant gas volume testing of the gas to be tested. The MFC flowmeter 8 with a range of 2-10sccm is used to achieve small flow rate precision control of the gas. Control valves are provided upstream and downstream of the MFC flowmeter 8. One end of the second connecting pipeline is connected to the second joint, and the other end is connected to the test chamber 3. A pressure relief valve 10 is connected to the third joint of the four-way valve 9; the pressure relief valve 10 is used to adjust the pressure of the gas to be tested so as not to exceed the pressure difference requirement of the MFC flowmeter 8. In this embodiment, about 1.5Bar is taken as an example;

[0036] The test method comprises the following steps:

[0037] S1. The background vacuum in the test chamber 3 is brought to the test standard by the molecular pump 2, the cold trap 13 and the baking device 14. To test the purity of helium at 99.999%, it is necessary to control the partial pressure of all residual gases in the test chamber 3 to the order of <-10Torr. The molecular pump 2 has a low pumping speed for water and hydrogen, and cannot be used alone to control the partial pressure of all residual gases to the order of <-10Torr. Therefore, the cold trap 13 is used to reduce the partial pressure of H2O in the test chamber 3 to the order of <-10Torr, and the baking device 14 is used to further reduce the partial pressure of H2O in the test chamber 3, and at the same time reduce the partial pressure of H2 in the test chamber 3 to the order of <-10Torr; thereby achieving the control of the partial pressure of all residual gases to the order of <-10Torr;

[0038] S2. Turn on the residual gas analyzer 4 for testing. After the test system is stable, monitor the system background residual gas partial pressure for a certain period of time;

[0039] S3, the system disconnects the gas sampler 12, monitors the system background residual gas partial pressure for a certain period of time, and establishes a background residual gas partial pressure benchmark;

[0040] S4, the gas sampler 12 takes a sample from a high-purity helium bottle, a compressor or a refrigerator through its detachable sealing female connector, and connects to the gas sampler 12 to access the entire test and analysis system;

[0041] S5, the MFC flowmeter 8 sets a certain flow rate to continuously introduce the gas to be tested into the test system, and the residual gas partial pressure in the test chamber 3 is continuously monitored by the residual gas analyzer 4;

[0042] S6. The residual gas partial pressure of the test chamber 3 and the background residual gas partial pressure reference data are processed by using a differential method, so as to obtain the proportion of different types of gases, that is, to achieve quantitative analysis of the gases.

[0043] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-purity gas purity test and analysis system, characterized in that: It includes a molecular pump, a cold trap, a test cavity, a connecting pipeline, and a gas sampler which are connected in sequence. A baking device is provided on the outside of the test cavity. The connecting pipeline includes a first connecting pipeline and a second connecting pipeline which are connected in parallel. An MFC flowmeter is provided on any of the connecting pipelines. Valves are provided on the first connecting pipeline and the second connecting pipeline. A residual gas analyzer and a high vacuum gauge are connected to the test cavity.

2. A high-purity gas purity testing and analysis system according to claim 1, characterized in that: The MFC flow meter range is 2-10 sccm.

3. A high-purity gas purity testing and analysis system according to claim 1, characterized in that: The connecting pipeline is connected to a four-way valve, a self-sealing joint is fixedly connected to the fourth joint of the four-way valve, and is detachably fixed to the gas sampler through the self-sealing joint.

4. A high-purity gas purity testing and analysis system according to claim 3, characterized in that: The first connecting pipeline comprises a bellows, the bellows is connected with the self-sealing joint through the first joint of the four-way valve, and a hand valve is arranged on the bellows.

5. A high-purity gas purity testing and analysis system according to claim 3, characterized in that: The second connecting pipeline is provided with an MFC flow meter and a control valve, and the second connecting pipeline is communicated with the second joint and the self-sealing joint of the four-way valve.

6. A high-purity gas purity testing and analysis system according to claim 5, characterized in that: The third joint of the four-way valve is connected with a pressure relief valve.

7. A high-purity gas purity testing and analysis system according to claim 1, characterized in that: Control valves are provided upstream and downstream of the MFC flowmeter.

8. A high-purity gas purity testing and analysis system according to claim 5, characterized in that: The baking device is arranged outside the test cavity.

9. A method for testing a high-purity gas purity testing and analysis system according to any one of claims 1 to 8, characterized in that: The steps include: S1. Adjust the system background vacuum to -10Torr level through molecular pump, cold trap and baking device; S2. Measure the background residual gas partial pressure through the residual gas analyzer and maintain it for a set time; S3, disconnect the gas sampler, monitor the background residual gas partial pressure of the test chamber and establish a background residual gas partial pressure benchmark; S4, sampling from a high-purity helium cylinder, a compressor or a refrigerator through the sampling end of the gas sampler and connecting it to the fixed end of the gas sampler; S5. Inject the gas to be tested at a set flow rate into the test system through the MFC flowmeter, and monitor the residual gas partial pressure in the test chamber through the residual gas analyzer; S6. The residual gas partial pressure of the test chamber and the background residual gas partial pressure benchmark data are processed by using a differential method to obtain the proportion of different types of gases.

10. A high-purity gas purity testing and analysis system according to claim 9, characterized in that: In S1, the H2O partial pressure in the test chamber is reduced to the level of <-10 Torr by a cold trap, and the H2O partial pressure in the test chamber is further reduced by a baking device, while the H2 partial pressure in the test chamber is reduced to the level of <-10 Torr.

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