Device for testing and analyzing purity of high-purity gas

Abstract

The utility model discloses a high-purity gas purity testing and analyzing device which comprises a dry pump, a molecular pump, a cold trap, a testing cavity, a connecting pipeline and a gas sampler which are connected in sequence, and the testing cavity is connected with a residual gas analyzer and a high vacuum gauge; the gas sampler comprises a double-end self-sealing joint, the double-end self-sealing joint comprises a sealing male head and a sealing female head which are detachably fixed, and the end, away from the sealing female head, of the sealing male head is fixedly connected with a connecting pipeline. According to the gas sampler, the dry pump can assist the molecular pump to establish a high vacuum environment for the side view cavity, the two ends of the gas sampler are arranged to be of detachable self-sealing joint structures, it is guaranteed that the sampler cannot be polluted by external gas in the disassembly and assembly process, and meanwhile the gas sampler can be flexibly used to achieve sampling in different environments; through on-line sampling of the sampling end of the gas sampler, helium sampling of the helium compressor can be completed without shutdown of the GM refrigerating machine system, and the test precision is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of test analysis system, more particularly to a kind of testing device of high-purity gas purity. BACKGROUND

[0002] High-purity gas generally refers to gas with purity equal to or higher than 99.999%, and high-purity gas is widely used in the fields of semiconductor industry, vacuum technology and low-temperature superconducting, etc., and plays a crucial role.

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

[0004] The GM refrigerator system includes a helium compressor, a helium pipe and an expander. The system requires the purity of helium to be above 99.999%. When the purity does not meet the standard, it may cause abnormal friction sound of the expander, performance degradation of the cold storage material, etc., resulting in performance degradation of the GM refrigerator. The helium compressor in the refrigerator system provides high-purity high-pressure helium for the expander. The low-pressure helium is pressurized by the compressor pump to become oil-gas mixed gas, separated by the oil filter, filtered by the adsorber to form high-purity helium above 99.999%, and the adsorber is usually made of adsorbent with developed pores. However, the adsorber will reach saturation after a long time of operation, losing the filtering effect, so 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 running time of the compressor, which cannot quantitatively evaluate the purity of the outlet gas of the adsorber.

[0005] Residual gas analyzer (RGA) requires an environment with a vacuum degree below 10-4 mbar to work, so it is often used to monitor and analyze the gas composition and concentration in a high-vacuum environment. Patent No. CN109799315 A discloses a system that connects the RGA to the measured vacuum chamber through a system fine-tuning valve, expands the working pressure of the RGA from atmospheric pressure to ultra-high vacuum, provides a residual gas analysis system suitable for a wide range of gas pressures, and solves the problem that the residual gas analyzer cannot analyze the gas composition at high gas pressure.

[0006] The patent document with the patent publication number CN 116298119 A discloses a helium purity analysis device and an analysis method, which comprises a sample inlet pipe, a detection pipe, a recovery pipe, a sensor, a combustion device, a hydrogen pipe and a mixed gas pipe. Different gas sensors are arranged in the detection pipe to test the content of different gases. The content of water, oxygen, nitrogen and hydrocarbon impurities in helium can be measured at the same time to realize quantitative analysis. The sample gas, hydrogen and nitrogen-oxygen mixed gas are mixed and combusted. Then, the content of nitrogen, oxygen and water in the helium is detected by a hydrocarbon sensor, an oxygen sensor, a nitrogen sensor and a humidity sensor to realize purity evaluation of the helium.

[0007] However, the scheme can only detect the content of nitrogen, oxygen and water by combustion method, and cannot evaluate the trace elements in the helium. Therefore, it cannot be used to test the purity of high-purity helium. The GM refrigerator system requires the purity of helium to be above 99.995%, and the testing accuracy of the gas is very high. The trace elements in the helium need to be quantitatively evaluated. At the same time, the impurity gas in the helium cannot be confirmed in advance during long-term circulation of the system, and the installation of the corresponding sensor may cause the test result to be incomplete. Practical new type content

[0008] The technical problem to be solved by the present application is how to improve the testing accuracy.

[0009] The present application solves the above technical problems by the following technical means: a high-purity gas purity testing and analyzing device, comprising a dry pump, a molecular pump, a cold trap, a testing cavity, a connecting pipeline and a gas sampler connected in sequence, wherein an oven device is arranged outside the testing cavity, the connecting pipeline comprises a first connecting pipeline and a second connecting pipeline connected in parallel, an MFC flow meter is arranged on any connecting pipeline, a valve is arranged on the first connecting pipeline and the second connecting pipeline, a residual gas analyzer and a high vacuum gauge are connected to the testing cavity, and the gas sampler comprises a double-end self-sealing joint.

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

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

[0012] Preferably, the first connecting pipeline comprises a bellows, the bellows is communicated with the self-sealing joint through the first joint of the four-way valve, and a hand valve is arranged on the bellows.

[0013] Preferably, the second connecting pipeline is provided with an MFC flowmeter and a control valve, and the second connecting pipeline is communicated with the self-sealing joint through the second joint of the four-way valve.

[0014] Preferably, a pressure relief valve is connected to the third joint of the four-way valve.

[0015] Preferably, control valves are arranged upstream and downstream of the MFC flowmeter.

[0016] Preferably, the baking device is arranged outside the test cavity.

[0017] The utility model discloses beneficial effect lies in:

[0018] (1) in the utility model, through dry pump can assist molecular pump for side -view cavity establishes high vacuum environment, through the both ends of gas sampler are all set up as detachable self -sealing joint structure, guaranteeing that sampler will not be contaminated by outside gas in the process of dismounting, can be used flexibly to realize sampling of different environment simultaneously, through the on -line sampling of gas sampler sampling end, guarantee GM refrigerating machine system to complete helium compressor helium sampling without stopping, improves the test accuracy.

[0019] (2) in the utility model, through the cold trap reduces H2O partial pressure in test cavity to be -10Torr level, through the baking device further reduces H2O partial pressure in test cavity, reduces H2 partial pressure in test cavity to be -10Torr level simultaneously, makes and tests the residual gas partial pressure in cavity to control in -10Torr level, uses small -flow MFC to realize the gas partial pressure of being passed in 10 -4 Torr level simultaneously, thereby reaches the requirement of helium 99.999% purity test, through the gas analyzer can be to the component quantitative analysis monitoring of mixed gas, through the vacuum gauge measurement 10 -7 Pa level pressure, through the use small -flow mass flowmeter MFC, the gas partial pressure of being measured maintains -4Torr level, forms and the significant order difference of background gas partial pressure, improves the high -purity gas test accuracy, and simultaneously the required gas sample amount of being measured is little, and the test time is long.

[0020] (3) in the utility model, use small -flow mass flowmeter MFC, the gas partial pressure of being measured maintains -4Torr level, forms and the significant order difference of background gas partial pressure, obtains high -purity gas test accuracy requirement, realizes constant -flow long -time stable injection gas of being measured simultaneously, guarantees the accuracy of test data. Attached Figure Description

[0021] Figure 1 A schematic diagram of the overall structure provided for an embodiment of this utility model;

[0022] Reference numerals in the attached diagram: 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 Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below in conjunction with the embodiments of this utility model. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0024] See Figure 1 A high-purity gas purity testing and analysis device includes a dry pump 1, a molecular pump 2, a cold trap 13, a test chamber 3, connecting pipelines, and a gas sampler 12 connected in series. A residual gas analyzer 4 and a high-vacuum gauge 5 are connected to the test chamber 3. The residual gas analyzer 4 is used to quantitatively test the partial pressure of the residual gas at 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 at a pressure reaching 10... -7 The ultra-high vacuum gauge of Pa is equipped with a baking device 14 on the test chamber 3. The baking device 14 is wrapped around the outside of the test chamber 3. The test chamber 3 is baked 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.

[0025] Dry pump 1 is the backing pump for molecular pump 2, used to assist molecular pump 2 in establishing a high vacuum environment in the test system. Molecular pump 2 is the main vacuum pump of the test system, used to achieve the ultra-high vacuum background environment of the system. Test chamber 3 is a stainless steel vacuum chamber. Cold trap 13 is used to assist molecular pump 2 in removing water vapor from the test chamber 3, reducing the water content and background vacuum of the system. The connecting pipelines include a first connecting pipeline and a second connecting pipeline connected in parallel.

[0026] The first connecting pipeline is in communication with the test cavity 3 at one end and in communication with the gas sampler 12 at the other end. The first connecting pipeline comprises a bellows 7 for connecting the gas sampler 12 and the test cavity 3 in the test system to realize evacuation of the gas sampler 12. The bellows 7 is further provided with a hand valve 6 for controlling the opening and closing of the pipeline. The bellows 7 is connected with a self-sealing joint 11 through a four-way valve 9. The self-sealing joint 11 is detachably fixed with the gas sampler 12. The four-way valve 9 is a commercially available KF25 four-way valve which is circumferentially provided with four joints in cross shape and in communication, namely a first joint, a second joint, a third joint and a fourth joint. The first joint of the four-way valve 9 is fixedly connected with the bellows 7, and the fourth joint is fixedly connected with the self-sealing joint 11. The gas sampler 12 is a commercially available double-end self-sealing joint which comprises 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 form of all the devices to be sampled, so that the whole test system is not polluted when the sampler is disassembled and assembled;

[0027] The second connecting pipeline is provided with an MFC flow meter 8 for quantitative injection of the gas to be tested to realize long-time constant-gas-volume testing of the gas to be tested. A 2-10sccm range MFC flow meter 8 is adopted to realize precise control of the small flow of the gas. Control valves are arranged upstream and downstream of the MFC flow meter 8. One end of the second connecting pipeline is connected with the second joint, and the other end is connected with the test cavity 3. The third joint of the four-way valve 9 is connected with a pressure relief valve 10. The pressure relief valve 10 is used to adjust the pressure of the gas to be tested to be not more than the pressure difference requirement of the MFC flow meter 8. In this embodiment, the pressure is taken as an example of about 1.5 Bar;

[0028] The test method comprises the following steps:

[0029] S1, The background vacuum in the test cavity 3 is brought to a test standard by a molecular pump 2, a cold trap 13 and a baking device 14. To test the purity of helium 99.999%, the partial pressure of all residual gases in the test cavity 3 needs to be controlled at a level of less than -10 Torr. The molecular pump 2 has low pumping speed for water and hydrogen, and cannot be used alone to control the partial pressure of all residual gases at a level of less than -10 Torr. Therefore, the cold trap 13 is used to reduce the H2O partial pressure in the test cavity 3 to a level of less than -10 Torr, and the baking device 14 is used to further reduce the H2O partial pressure in the test cavity 3 and reduce the H2 partial pressure in the test cavity 3 to a level of less than -10 Torr, so as to control the partial pressure of all residual gases at a level of less than -10 Torr.

[0030] S2, The residual gas analyzer 4 is turned on for testing. After the test system is stable, the background residual gas partial pressure of the monitoring system is monitored for a certain period of time.

[0031] S3, the system disconnects the gas sampler 12, monitors the background residual gas partial pressure for a certain time, and establishes a background residual gas partial pressure benchmark;

[0032] S4, the gas sampler 12 samples from a high-purity helium gas cylinder, a compressor or a refrigerator through a detachable sealing female head connected to the gas sampler 12 to access the entire test analysis system;

[0033] S5, the MFC flow meter 8 sets a certain flow rate to continuously introduce the gas to be tested into the test system, and continuously monitors the residual gas partial pressure of the test cavity 3 through the residual gas analyzer 4;

[0034] S6, the data of the residual gas partial pressure of the test cavity 3 and the background residual gas partial pressure benchmark are processed by using the differential method, so as to obtain the proportion of different kinds of gas, that is, the quantitative analysis of the gas is realized.

[0035] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can still be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A high-purity gas purity testing and analysis device, comprising a dry pump, a molecular pump, a cold trap, a test chamber, connecting pipes, and a gas sampler connected in sequence; the test chamber is equipped with a baking device on its outer side; the connecting pipes include a first connecting pipe and a second connecting pipe connected in parallel; an MFC flow meter is installed on either connecting pipe; valves are installed on both the first and second connecting pipes; a residual gas analyzer and a high vacuum gauge are connected to the test chamber; the gas sampler includes a double-ended self-sealing connector, the double-ended self-sealing connector including a detachably fixed sealing male and a sealing female, the end of the sealing male opposite to the sealing female being fixedly connected to the connecting pipe.

2. The apparatus for testing and analyzing the purity of high-purity gases according to claim 1, characterized in that, The MFC flow metering range is 2-10 sccm.

3. The apparatus for testing and analyzing the purity of high-purity gases according to claim 1, characterized in that, The connecting pipeline is connected to a four-way valve, and a self-sealing connector is fixedly connected to the fourth connector of the four-way valve. The gas sampler is detachably fixed through the self-sealing connector.

4. The apparatus for testing and analyzing the purity of a high-purity gas according to claim 3, characterized in that, The first connecting pipeline includes a bellows, which is connected to a self-sealing joint through the first joint of a four-way valve, and a manual valve is provided on the bellows.

5. The apparatus for testing and analyzing the purity of a high-purity gas according to claim 3, characterized in that, The second connecting pipeline is equipped with an MFC flow meter and a control valve, and the second connector of the second connecting pipeline and the four-way valve is connected to a self-sealing connector.

6. The apparatus for testing and analyzing the purity of a high-purity gas according to claim 5, characterized in that, A pressure relief valve is connected to the third connector of the four-way valve.

7. The apparatus for testing and analyzing the purity of high-purity gases according to claim 1, characterized in that, The MFC flow meter is equipped with control valves both upstream and downstream.

8. The apparatus for testing and analyzing the purity of high-purity gases according to claim 5, characterized in that, The baking device is wrapped around the outside of the test chamber.

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