Method for improving sensitivity of pressure vacuum method helium mass spectrum leak detection system

Abstract

The invention relates to a method for improving sensitivity of a pressure vacuum method helium mass spectrum leak detection system, and belongs to the technical field of nondestructive testing. Establishing a vacuum leak detection system; the vacuum chamber is connected with the calibration leak hole through a pipeline; putting the detected piece into the vacuum chamber, and closing a gate of the vacuum chamber; opening a mechanical pump valve and a molecular pump valve; vacuumizing the vacuum chamber through a mechanical pump and a molecular pump until the vacuum degree of the vacuum chamber is stable; starting the leak detector to enter a leak detection state; opening the leak detection valve to enable the leak detector to be communicated with the vacuum chamber; gas is input through the micro-flow device; after the number measured by the leak detector is stable, reading a background value I0 and a noise value In of the vacuum leak detection system; opening a calibration leak hole; after the number measured by the leak detector is stable, the reaction value I of the calibration leak hole is measured; calculating the effective minimum leak detection rate Qemin of the vacuum leak detection system, and completing the measurement of the sensitivity of the system; the pre-stage vacuum degree of the leak detection system is adjusted, so that the background and noise of the leak detection system are reduced, and the detection sensitivity of the system is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of nondestructive testing and relates to a method for improving the sensitivity of a pressure vacuum method helium mass spectrometer leak detection system. Background Art

[0002] With the high frequency of spacecraft launches, leakage incidents have occurred repeatedly. Through systematic investigation, it was found that leakage of pressure-bearing products occurred in the assembly test and pre-launch test, causing great losses. In order to strictly control the sealing quality of pressure-bearing products, designers have put forward higher and higher requirements for the sealing performance of pressure-bearing products. Generally, the total leakage rate index is required to be 10 -8 ~10 -5 Pa·m 3 / s.

[0003] The pressure vacuum helium mass spectrometry leak detection technology has the advantages of high system sensitivity, easy implementation and high detection efficiency, and is widely used in the total leakage rate detection of pressure-bearing products. Since the pressure-bearing product leak detection has the characteristics of high detection pressure, large number of products, and easy leakage of tooling, the leaked helium will remain in the system during large-scale continuous detection, causing helium pollution, which can easily lead to an increase in background and a decrease in sensitivity. Sometimes it can't even meet the requirements of pressure-bearing product leak detection, which seriously affects the detection efficiency and reliability. Therefore, it is necessary to study and solve methods to improve the detection sensitivity of the system. Summary of the invention

[0004] The technical problem solved by the present invention is: to overcome the deficiencies of the prior art, to propose a method for improving the sensitivity of a pressure vacuum method helium mass spectrometer leak detection system, to achieve the adjustment of the vacuum degree of the forestage of the leak detection system, thereby reducing the background and noise of the leak detection system and improving the detection sensitivity of the system.

[0005] The solution of the present invention is:

[0006] A method for improving the sensitivity of a pressure vacuum method helium mass spectrometer leak detection system, comprising:

[0007] Establish a vacuum leak detection system; including a vacuum chamber, a molecular pump, a molecular pump valve, a leak detector, a leak detection valve, a mechanical pump, a mechanical pump valve and a micro-flow device; the vacuum chamber is connected to the calibrated leak hole through a pipeline;

[0008] Place the test piece into the vacuum chamber and close the door of the vacuum chamber;

[0009] Open the mechanical pump valve and the molecular pump valve; evacuate the vacuum chamber by using the mechanical pump and the molecular pump until the vacuum degree of the vacuum chamber is stable;

[0010] Start the leak detector and enter the leak detection state; open the leak detection valve to connect the leak detector with the vacuum chamber;

[0011] Gas is introduced through a micro-flow device;

[0012] After the leak detector measurement is stable, read the background value I0 and noise value I of the vacuum leak detection system. n ;

[0013] Open the calibrated leak; after the leak detector readings stabilize, measure the response value I of the calibrated leak;

[0014] Calculate the effective minimum leak detection rate Q of the vacuum leak detection system emin , complete the measurement of system sensitivity.

[0015] In the above-mentioned method for improving the sensitivity of a pressure vacuum method helium mass spectrometer leak detection system, the vacuum chamber is a hollow cavity structure; the vacuum chamber is connected to one end of a molecular pump valve through a pipeline; the other end of the molecular pump valve is connected to a molecular pump through a pipeline; the molecular pump is connected to one end of the leak detection valve, one end of a mechanical pump valve and a micro-flow device through a four-way valve; the other end of the leak detection valve is connected to a leak detector; and the other end of the mechanical pump valve is connected to a mechanical pump.

[0016] In the above method for improving the sensitivity of a pressure vacuum method helium mass spectrometer leak detection system, the side wall of the vacuum chamber is connected to the calibration leak hole through a pipeline; the calibration leak hole is in a closed state in an initial state.

[0017] In the above method for improving the sensitivity of the pressure vacuum method helium mass spectrometer leak detection system, the specific method of evacuating the vacuum chamber by the mechanical pump and the molecular pump is as follows:

[0018] Open the mechanical pump valve and the molecular pump valve; start the mechanical pump first, and evacuate the vacuum chamber through the mechanical pump; start the molecular pump, and the mechanical pump and the molecular pump perform vacuum processing together.

[0019] In the above method for improving the sensitivity of the pressure vacuum method helium mass spectrometer leak detection system, when the mechanical pump evacuates until the pressure at the connection between the molecular pump and the vacuum chamber is less than 50 Pa, the molecular pump is started.

[0020] In the above method for improving the sensitivity of the pressure vacuum method helium mass spectrometer leak detection system, the vacuum degree of the vacuum chamber is better than 1×10 in a stable state. -2 Pa.

[0021] In the above method for improving the sensitivity of a pressure vacuum helium mass spectrometer leak detection system, the gas is nitrogen; the input nitrogen flow rate is 10 -2 Pa·m 3 / s.

[0022] In the above method for improving the sensitivity of the pressure vacuum helium mass spectrometer leak detection system, the leak detector measures two values, one of which is a stable average value, i.e., the system background value I0; the other is a fluctuation value, i.e., the noise value In .

[0023] In the above method for improving the sensitivity of the pressure vacuum method helium mass spectrometer leak detection system, after the calibration leak hole is opened, the stable average value measured by the leak detector is the reaction value I of the calibration leak hole.

[0024] In the above method for improving the sensitivity of the pressure vacuum helium mass spectrometer leak detection system, the effective minimum leak detection rate Q of the vacuum leak detection system emin The calculation method is:

[0025]

[0026] Where Q0 is the nominal leak rate value of the calibrated leak.

[0027] The beneficial effects of the present invention compared with the prior art are:

[0028] (1) The present invention takes the pressure vacuum method leak detection system as the research object. When the leak detection system reaches dynamic equilibrium, a micro-flow of pure nitrogen is filled between the main pump and the front-stage pump to blow the vacuum system, thereby adjusting the front-stage vacuum degree of the leak detection system and changing the gas flow state in the dynamic equilibrium mode of the vacuum system to reduce the system background and noise, and finally improve the sensitivity of the detection system;

[0029] (2) The present invention establishes a rapidly increasing pressure vacuum method helium mass spectrometry leak detection system to ensure that the leak detection requirements of pressure-bearing products are met and the detection accuracy and efficiency are improved;

[0030] (3) The present invention uses a molecular pump and a mechanical pump to perform vacuuming in coordination, and sets a start-up judgment standard for the molecular pump, thereby ensuring accurate control of the stability of the vacuum degree in the vacuum chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the vacuum leak detection system of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the embodiments.

[0033] The invention provides a method for improving the sensitivity of a pressure vacuum method helium mass spectrometer leak detection system, which realizes adjusting the vacuum degree of the forestage of the leak detection system, thereby reducing the background and noise of the leak detection system and improving the detection sensitivity of the system.

[0034] The method for improving the sensitivity of a pressure vacuum helium mass spectrometer leak detection system specifically comprises the following steps:

[0035] Establish a vacuum leak detection system, such as Figure 1As shown, it specifically includes a vacuum chamber, a molecular pump, a molecular pump valve, a leak detector, a leak detection valve, a mechanical pump, a mechanical pump valve and a micro-flow device; the vacuum chamber is connected to the calibration leak through a pipeline. The vacuum chamber is a hollow cavity structure; the vacuum chamber is connected to one end of the molecular pump valve through a pipeline; the other end of the molecular pump valve is connected to the molecular pump through a pipeline; the molecular pump is connected to one end of the leak detection valve, one end of the mechanical pump valve and the micro-flow device through a four-way valve; the other end of the leak detection valve is connected to the leak detector; the other end of the mechanical pump valve is connected to the mechanical pump. The side wall of the vacuum chamber is connected to the calibration leak through a pipeline; the calibration leak is closed in the initial state.

[0036] Place the test piece into the vacuum chamber and close the door of the vacuum chamber.

[0037] Open the mechanical pump valve and the molecular pump valve; evacuate the vacuum chamber by the mechanical pump and the molecular pump until the vacuum degree of the vacuum chamber is stable.

[0038] The specific method of using mechanical pumps and molecular pumps to evacuate the vacuum chamber is as follows:

[0039] Open the mechanical pump valve and the molecular pump valve; start the mechanical pump first, and evacuate the vacuum chamber through the mechanical pump; start the molecular pump, and the mechanical pump and the molecular pump perform vacuum processing together.

[0040] The judgment condition for starting the molecular pump is that when the mechanical pump evacuates until the pressure at the connection between the molecular pump and the vacuum chamber is less than 50Pa, the molecular pump starts.

[0041] Under stable conditions, the vacuum degree of the vacuum chamber is better than 1 x 10 -2 Pa.

[0042] Start the leak detector; open the leak detection valve; connect the leak detector to the vacuum chamber.

[0043] The gas is nitrogen; the input nitrogen flow rate is 10 -2 Pa·m 3 / s.

[0044] After the leak detector measurement is stable, read the background value I0 and noise value I of the vacuum leak detection system. n .

[0045] The leak detector measures two values, one of which is a stable average value, which is the system background value I0; the other is a fluctuation value, which is the noise value I n .

[0046] Open the calibrated leak; after the leak detector's readings stabilize, measure the reaction value I of the calibrated leak; after opening the calibrated leak, the stable average value measured by the leak detector is the reaction value I of the calibrated leak.

[0047] Calculate the effective minimum leak detection rate Q of the vacuum leak detection system emin , complete the measurement of system sensitivity.

[0048] The effective minimum leak detection rate Q of the vacuum leak detection system emin The calculation method is:

[0049]

[0050] Where Q0 is the nominal leak rate value of the calibrated leak.

[0051] Example

[0052] The following is a description of the process of improving the sensitivity of the pressure vacuum helium mass spectrometer leak detection system by micro-flow gas injection. The minimum detectable leak rate of the leak detection system after helium contamination is 1.32×10 -7 Pa·m 3 / s.

[0053] Connect a standard leak rate (nominal leak rate is 2.00×10 -2 Pa·m 3 / s). First, use the vacuum pump to evacuate the vacuum chamber until the vacuum degree of the vacuum chamber is 1×10 -3 Pa, then open the leak detection valve to connect the leak detector to the vacuum system. After the reading of the leak detector is basically stable, use the standard leak hole to fill the vacuum system with a stable flow of pure nitrogen to blow the vacuum system. After the vacuum state is stable, the inlet pressure of the leak detector is 7.28Pa, and the leak detector is still in the precision inspection mode.

[0054] Observe the leak detector reading and record the system background I0 as 1.06×10 -7 Pa·m 3 / s and noise I n 6.00×10 - 9 Pa·m 3 / s, open the calibrated leak (nominal leak rate Q0 is 1.10×10 -6 Pa·m 3 / s), and then read the leak response value I as 1.10×10 -6 Pa·m 3 / s.

[0055] Finally, using the formula To calculate the effective minimum detectable leak rate (i.e., system sensitivity) of the leak detection system, the result is 6.60×10 -9 Pa·m 3 / s. Compared with the previous system’s minimum detectable leak rate of 1.32×10 -7 Pa·m3 / s, after the injection, the system sensitivity is increased by several orders of magnitude. In summary, the method of the present invention is an effective method for rapidly improving the sensitivity of the pressure vacuum leak detection system.

[0056] The invention establishes a helium mass spectrometer leak detection system with a rapid pressure increase vacuum method to ensure that the leak detection requirements of pressure-bearing products are met and the detection accuracy and efficiency are improved.

[0057] The present invention performs vacuuming processing by cooperating with a molecular pump and a mechanical pump, and sets a start-up judgment standard of the molecular pump, thereby ensuring accurate control of the stability of the vacuum degree in the vacuum chamber.

[0058] The present invention takes the pressure vacuum method leak detection system as the research object. When the leak detection system reaches dynamic balance, a micro-flow of pure nitrogen is filled between the main pump and the front-stage pump to blow the vacuum system, thereby adjusting the front-stage vacuum degree of the leak detection system and changing the gas flow state in the dynamic balance mode of the vacuum system, so as to reduce the system background and noise, and finally improve the sensitivity of the detection system.

[0059] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for improving the sensitivity of a pressure vacuum helium mass spectrometer leak detection system, characterized in that: include: Establish a vacuum leak detection system; including a vacuum chamber, a molecular pump, a molecular pump valve, a leak detector, a leak detection valve, a mechanical pump, a mechanical pump valve and a micro-flow device; The vacuum chamber is connected to the calibrated leak through a pipeline; Place the test piece into the vacuum chamber and close the door of the vacuum chamber; Open the mechanical pump valve and the molecular pump valve; evacuate the vacuum chamber by using the mechanical pump and the molecular pump until the vacuum degree of the vacuum chamber is stable; Start the leak detector to enter the leak detection state; open the leak detection valve; connect the leak detector with the vacuum chamber; Gas is introduced through a micro-flow device; After the leak detector measurement is stable, read the background value I0 and noise value I of the vacuum leak detection system. n ; Open the calibrated leak; after the leak detector readings stabilize, measure the response value I of the calibrated leak; Calculate the effective minimum leak detection rate Q of the vacuum leak detection system emin , complete the measurement of system sensitivity.

2. The method for improving the sensitivity of a pressure vacuum helium mass spectrometer leak detection system according to claim 1, characterized in that: The vacuum chamber is a hollow cavity structure; the vacuum chamber is connected to one end of the molecular pump valve through a pipeline; the other end of the molecular pump valve is connected to the molecular pump through a pipeline; the molecular pump is connected to one end of the leak detection valve, one end of the mechanical pump valve and the micro-flow device through a four-way valve; the other end of the leak detection valve is connected to the leak detector; the other end of the mechanical pump valve is connected to the mechanical pump.

3. The method for improving the sensitivity of a pressure vacuum helium mass spectrometer leak detection system according to claim 2, characterized in that: The side wall of the vacuum chamber is connected to the calibrated leak hole through a pipeline; the calibrated leak hole is in a closed state in an initial state.

4. The method for improving the sensitivity of a pressure vacuum helium mass spectrometer leak detection system according to claim 3, characterized in that: The specific method of using mechanical pumps and molecular pumps to evacuate the vacuum chamber is as follows: Open the mechanical pump valve and the molecular pump valve; start the mechanical pump first, and evacuate the vacuum chamber through the mechanical pump; start the molecular pump, and the mechanical pump and the molecular pump perform vacuum processing together.

5. The method for improving the sensitivity of a pressure vacuum helium mass spectrometer leak detection system according to claim 4, characterized in that: When the mechanical pump evacuates until the pressure at the connection between the molecular pump and the vacuum chamber is less than 50Pa, the molecular pump starts.

6. The method for improving the sensitivity of a pressure vacuum helium mass spectrometer leak detection system according to claim 4, characterized in that: Under stable conditions, the vacuum degree of the vacuum chamber is better than 1×10 -2 Pa.

7. The method for improving the sensitivity of a pressure vacuum helium mass spectrometer leak detection system according to claim 4, characterized in that: The gas is nitrogen; the input nitrogen flow rate is 10 -2 Pa·m 3 / s level.

8. The method for improving the sensitivity of a pressure vacuum helium mass spectrometer leak detection system according to claim 4, characterized in that: The leak detector measures two values, one of which is a stable average value, which is the system background value I0; the other is a fluctuation value, which is the noise value I n .

9. The method for improving the sensitivity of a pressure vacuum helium mass spectrometer leak detection system according to claim 4, characterized in that: After opening the calibrated leak, the stable average value measured by the leak detector is the reaction value I of the calibrated leak.

10. The method for improving the sensitivity of a pressure vacuum helium mass spectrometer leak detection system according to claim 4, characterized in that: The effective minimum leak detection rate Q of the vacuum leak detection system emin The calculation method is: Where Q0 is the nominal leak rate value of the calibrated leak.

Images