A liquid medium vacuum leak detection method for aerospace

Abstract

The present invention discloses a method for vacuum leak detection of liquid media for aerospace use, comprising a calibration system, a leak rate testing system, a standard leak hole and an auxiliary air extraction system. The calibration system and the leak rate testing system both comprise a mechanical pump, a solenoid valve, a vacuum plug valve, a vacuum gauge and a quadrupole mass spectrometer. The calibration system further comprises a pre-stage molecular pump, a main molecular pump, a pressure stabilizing chamber, an air extraction hole and a calibration chamber. The leak rate testing system further comprises a molecular pump, a vacuum container and a product to be tested. The standard leak hole comprises a hand valve, an air extraction hole, a hand valve, a vacuum gauge, a hand valve, a working medium container and a hand valve. The auxiliary air extraction system comprises a molecular pump, a solenoid valve and a mechanical pump. In the present invention, the standard leak hole is calibrated by the testing system, and then the leak rate test of the product to be tested is carried out by comparison, so as to quickly and effectively detect the leak of a product whose storage medium is liquid at normal temperature and pressure and has no leak detection port or air filling port, and provide an effective and reliable leak rate.

Description

Technical Field

[0001] The present invention relates to the technical field of sealing leak detection, in particular to a liquid medium vacuum leak detection method for aerospace. Background Art

[0002] With the continuous development of China's aerospace industry, aerospace products now store liquid working fluids at room temperature and pressure, in addition to gaseous media. Furthermore, these aerospace products lack leak detection and inflation ports, making it impossible to perform leak rate testing using conventional helium mass spectrometry vacuum leak detection methods used for aerospace products.

[0003] Since the normal temperature gas phase pressures of different liquid working fluids are different and all below one atmosphere, the air in the working fluid storage tank needs to be completely evacuated during the preparation of the standard leak to prevent the working fluid inside the tank from being vaporized into a gaseous state. The measured working fluid's normal temperature gas phase pressure is relatively low. For the same standard leak aperture size, different working fluid gases move differently through the standard leak, which is not applicable to the ideal gas equation. At the same time, if the aperture is too small, the working fluid will easily clog the leak, or the calibration system and test system will not be able to detect the standard leak value; if the aperture is too large, the vacuum system will easily extract the working fluid from the working fluid storage tank during the test, resulting in large errors in the test results. Therefore, it is necessary to make a series of standard leak apertures, estimate the leak rate of the standard leak, and calibrate the standard leak using the corresponding calibration method on the calibration system.

[0004] The present invention proposes a leak detection method for aerospace products whose storage media is liquid at room temperature and pressure and lacks leak detection ports and inflation ports. This method first requires the preparation and calibration of a standard leak for the stored liquid working fluid. Then, in combination with the national standard for quadrupole mass spectrometry leak detection, a leak detection system is constructed. A mechanical pump, solenoid valve, molecular pump, vacuum gauge, quadrupole mass spectrometer, vacuum container, and the prepared standard leak are connected. The standard leak is calibrated using the test system, and then the leak rate of the product under test is tested through a comparison method. This method can solve the problem of leak rate detection for aerospace products that store liquid working fluids and lack leak detection ports. This method can quickly and effectively detect leaks in products whose storage media is liquid at room temperature and pressure and lacks leak detection ports and inflation ports. Its most significant feature is that by preparing and calibrating standard leaks for different liquid working fluids, leak rate testing can be performed on products that store different liquid working fluids and lack leak detection ports and inflation ports. Summary of the Invention

[0005] The purpose of the present invention is to solve the above problems and to propose a vacuum leak detection method for liquid medium for aerospace use.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for vacuum leak detection of liquid media for aerospace use, comprising a calibration system, a leak rate testing system, a standard leak hole, and an auxiliary air extraction system, wherein the calibration system and the leak rate testing system both comprise a mechanical pump, a solenoid valve, a vacuum plug valve, a vacuum gauge, and a quadrupole mass spectrometer;

[0008] The calibration system also includes a front molecular pump, a main molecular pump, a pressure stabilizing chamber, an air pumping hole 1 and a calibration chamber;

[0009] The leak rate test system also includes a molecular pump, a vacuum container and a product to be tested;

[0010] The standard leak holes include hand valve 1, air extraction hole 2, hand valve 2, vacuum gauge 2, hand valve 3, working fluid container and hand valve 4;

[0011] The auxiliary pumping system includes a second molecular pump, a second solenoid valve and a second mechanical pump.

[0012] Preferably, the calibration system for the liquid working fluid standard leak includes the following steps:

[0013] S1, manual valve 1 is in the closed state, open the calibration system mechanical pump 1, the front molecular pump, the main molecular pump and the corresponding valves, wait for the calibration chamber pressure to stabilize, and record the pressure value of vacuum gauge 1 as P1;

[0014] S2, manual valve 1 and manual valve 3 are in the closed state, open other vacuum pumps and valves except the calibration system, and pump to the ultimate vacuum;

[0015] S3. Close manual valve 4, open manual valve 3, and observe that vacuum gauge 2 reaches the gas phase pressure of the working fluid at room temperature;

[0016] S4. Open manual valve 1. After the pressure in the calibration chamber stabilizes, record the pressure value of vacuum gauge 1 as P2. Observe the spectrum of the quadrupole mass spectrometer and record the mass number of the peak corresponding to the working fluid mass spectrum.

[0017] S5. Conductance formula through a circular hole

[0018]

[0019] Where, T is the gas temperature [K]

[0020] M——molar mass of the working fluid gas being measured [kg / mol]

[0021] d——diameter of the exhaust hole, known to be 18mm

[0022] It is concluded that the conductance of one of the small holes for exhaust is C1;

[0023] S6, the effective pumping speed S1 of one small pumping hole is:

[0024]

[0025] Among them, C1 is the flow conductance of one small hole for exhaust [m 3 / s]

[0026] S——effective pumping speed of main molecular pump outlet [m 3 / s],S>>C1

[0027] Therefore, S1≈C1;

[0028] S7, flow rate Q of one small suction hole:

[0029] Q=S×P (3)

[0030] Where, S is the effective pumping speed of one small pumping hole [m 3 / s]

[0031] P——Stable pressure value of calibration room [Pa];

[0032] S8. Since the system mass flow is equal, the leakage rate Q0 of the standard leak hole is obtained by the formula:

[0033] Q0=S×(P2-P1) (4)

[0034] Where, S is the effective pumping speed of one small pumping hole [m 3 / s]

[0035] P1——Stable pressure value of the calibration chamber after closing the manual valve [Pa]

[0036] P2——Stable pressure value of the calibration chamber after opening the manual valve [Pa].

[0037] Preferably, the pre-processing steps before testing the tested product include:

[0038] S1. Use high-purity nitrogen to blow off the surface of the product to be tested;

[0039] S2. Place the product to be tested in a vacuum container and evacuate it to remove any working fluid that may be adsorbed on the surface.

[0040] Preferably, the leak rate test process of the product under test includes the following steps:

[0041] S1. When the product to be tested is not placed in the container, close the door of the vacuum container and evacuate the container to the limit state;

[0042] S2, the manual valve is in the closed state, the quadrupole mass spectrometer is turned on, and the peak current value I0 of the mass spectrum of the working fluid corresponding to the quadrupole mass spectrometer is recorded;

[0043] S3, manual valve 1 and manual valve 3 are in the closed state, open other vacuum pumps and valves except the test system, and pump to the ultimate vacuum;

[0044] S4. Close manual valve 4, open manual valve 3, and observe that vacuum gauge 2 reaches the gas phase pressure of the working fluid at room temperature;

[0045] S5. Open manual valve 1, wait until the vacuum is stable, then turn on the quadrupole mass spectrometer and record the peak current value I1 of the mass spectrum of the working fluid;

[0046] S6. Place the product to be tested into a vacuum container, close the door of the vacuum container, and evacuate the vacuum container to the limit state;

[0047] S7. After the vacuum degree of the vacuum container is stable, turn on the quadrupole mass spectrometer and record the peak current value I2 of the mass spectrum of the working fluid corresponding to the quadrupole mass spectrometer;

[0048] S8. The leakage rate Q of the product under test is calculated by the formula:

[0049]

[0050] Where, I0 is the background value of the working fluid in the container [A]

[0051] I1——Standard leak response value [A]

[0052] I2——Reaction value of the tested product [A]

[0053] Q0——Standard leak rate value [Pa·m 3 / s].

[0054] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0055] 1. This application prepares and calibrates a standard leak for the stored liquid working fluid, and then combines it with the national standard for quadrupole mass spectrometry leak detection to build a leak detection system. The mechanical pump, solenoid valve, molecular pump, vacuum gauge, quadrupole mass spectrometer, vacuum container, and the prepared standard leak are connected. The standard leak is calibrated through the test system, and then the leak rate of the tested product is tested by comparison. This can solve the problem of leak rate detection of aerospace products that store liquid working fluids and have no leak detection ports. This method can quickly and effectively detect leaks in products whose storage media is liquid at room temperature and pressure and have no leak detection ports or inflation ports. By preparing and calibrating standard leaks for different liquid working fluids, leak rate testing can be achieved for products that store different liquid working fluids and have no leak detection ports or inflation ports. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 A schematic diagram of a standard leak calibration principle of a liquid medium in aerospace vacuum leak detection method according to an embodiment of the present invention is shown;

[0057] Figure 2 A schematic diagram of a leak rate test principle for a product under test according to an embodiment of the present invention is shown.

[0058] Legend:

[0059] 1. Mechanical pump 1; 2. Solenoid valve 1; 3. Fore-stage molecular pump; 4. Main molecular pump; 5. Vacuum plug valve; 6. Vacuum gauge 1; 7. Quadrupole mass spectrometer; 8. Pressure stabilization chamber; 9. Pumping hole 1; 10. Calibration chamber; 11. Molecular pump 1; 12. Vacuum container; 13. Measured product; 14. Manual valve 1; 15. Pumping hole 2; 16. Manual valve 2; 17. Vacuum gauge 2; 18. Manual valve 3; 19. Working fluid container; 20. Manual valve 4; 21. Molecular pump 2; 22. Solenoid valve 2; 23. Mechanical pump 2. DETAILED DESCRIPTION

[0060] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only 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 making any creative efforts shall fall within the scope of protection of the present invention.

[0061] See also Figure 1-2 , the present invention provides a technical solution:

[0062] A method for vacuum leak detection of liquid media for aerospace use, comprising a calibration system, a leak rate testing system, a standard leak hole, and an auxiliary air extraction system, wherein the calibration system and the leak rate testing system both comprise a mechanical pump 1, a solenoid valve 2, a vacuum plug valve 5, a vacuum gauge 6, and a quadrupole mass spectrometer 7;

[0063] The calibration system also includes a front molecular pump 3, a main molecular pump 4, a pressure stabilizing chamber 8, an air pumping hole 9 and a calibration chamber 10;

[0064] The leak rate test system also includes a molecular pump 11, a vacuum container 12 and a product to be tested 13;

[0065] The standard leak holes include manual valve 1 14, air extraction hole 2 15, manual valve 2 16, vacuum gauge 2 17, manual valve 3 18, working fluid container 19 and manual valve 4 20;

[0066] The auxiliary pumping system includes a molecular pump 21 , a solenoid valve 22 and a mechanical pump 23 .

[0067] Specifically, such as Figure 1 As shown in the figure, due to the special nature of the working fluid (low pressure of the liquid and gas phases), it is impossible to make a calibration standard leak in the conventional way. The standard leak used is a special working condition leak and needs to be calibrated separately. The calibration system for the liquid working fluid standard leak includes the following steps:

[0068] S1, manual valve 14 is in the closed state, open the calibration system mechanical pump 1, the front molecular pump 3, the main molecular pump 4 and the corresponding valves, wait for the pressure in the calibration chamber 10 to stabilize, and record the pressure value of the vacuum gauge 6 as P1;

[0069] S2, manual valve 14 and manual valve 3 18 are in the closed state, and other vacuum pumps and valves except the calibration system are turned on to pump to the ultimate vacuum;

[0070] S3. Close the manual valve 4 20, open the manual valve 3 18, and observe that the vacuum gauge 2 17 reaches the gas phase pressure of the working fluid at room temperature;

[0071] S4. Open manual valve 14. After the pressure in calibration chamber 10 stabilizes, record the pressure value of vacuum gauge 6 as P2. Observe the spectrum of quadrupole mass spectrometer 7 and record the mass number of the peak corresponding to the working fluid mass spectrum.

[0072] S5. Conductance formula through a circular hole

[0073]

[0074] Where, T is the gas temperature [K]

[0075] M——molar mass of the working fluid gas being measured [kg / mol]

[0076] d——diameter of the air extraction hole, 18mm is known

[0077] It is concluded that the conductance at the 9th extraction hole is C1;

[0078] S6, the effective pumping speed S1 at the 9th pumping hole is:

[0079]

[0080] Among them, C1——the flow conductance of the 9 air extraction holes [m 3 / s]

[0081] S——effective pumping speed of main molecular pump 4 pump port [m 3 / s],S>>C1

[0082] Therefore, S1≈C1;

[0083] S7, air extraction hole 9 flow rate Q:

[0084] Q=S×P (3)

[0085] Where, S is the effective pumping speed at the air pumping hole [m 3 / s]

[0086] P——stable pressure value of calibration room 10 [Pa];

[0087] S8. Since the system mass flow is equal, the leakage rate Q0 of the standard leak hole is obtained by formula 4:

[0088] Q0=S×(P2-P1) (4)

[0089] Where, S is the effective pumping speed at the air pumping hole [m 3 / s]

[0090] P1——Close the manual valve 14 and calibrate the stable pressure value of chamber 10 [Pa]

[0091] P2——Stable pressure value of calibration chamber 10 after opening manual valve 14 [Pa].

[0092] Specifically, such as Figure 2 As shown, the pre-processing steps before testing the tested product 13 include:

[0093] S1. Use high-purity nitrogen to blow off the surface of the product 13 under test;

[0094] S2. Place the product 13 to be tested in the vacuum container 12, evacuate the container, and remove the working medium that may be adsorbed on the surface.

[0095] The leak rate test process of the product under test includes the following steps:

[0096] S1. When no product 13 to be tested is placed in the container, the door of the vacuum container 12 is closed and the vacuum container 12 is evacuated to the limit state;

[0097] S2, the manual valve 14 is in the closed state, the quadrupole mass spectrometer 7 is turned on, and the peak current value I0 of the mass spectrum of the working medium corresponding to the quadrupole mass spectrometer 7 is recorded;

[0098] S3, manual valve 1 9 and manual valve 3 18 are in the closed state, open other vacuum pumps and valves except the test system, and pump to the ultimate vacuum;

[0099] S4. Close the fourth manual valve 20, open the third manual valve 18, and observe that the vacuum gauge 2 17 reaches the gas phase pressure of the working fluid at room temperature;

[0100] S5, open the manual valve 14, wait for the vacuum degree to stabilize, turn on the quadrupole mass spectrometer 7, and record the peak current value I1 of the mass spectrum of the working medium corresponding to the quadrupole mass spectrometer 7;

[0101] S6. Place the product 13 to be tested in the vacuum container 12, close the door of the vacuum container 12, and evacuate the vacuum container 12 to the limit state;

[0102] S7, after the vacuum degree of the vacuum container 12 is stabilized, the quadrupole mass spectrometer 7 is turned on, and the peak current value I2 of the mass spectrum of the working medium corresponding to the quadrupole mass spectrometer 7 is recorded;

[0103] S8, the leakage rate Q of the tested product 13 is calculated by formula 5:

[0104]

[0105] Where, I0 is the background value of the working fluid in the container [A]

[0106] I1——Standard leak response value [A]

[0107] I2——Reaction value of the tested product [A]

[0108] Q0——Standard leak rate value [Pa·m 3 / s].

[0109] This application calibrates the standard leak hole through the test system, and then implements the leakage rate test of the tested product 13 through the comparison method, so as to quickly and effectively detect the leak of the product whose storage medium is liquid at normal temperature and pressure and has no leak detection port and inflation port, and provide an effective and reliable leak rate.

[0110] The above description of the embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for vacuum leak detection of liquid medium for aerospace use, characterized in that: The leak detection device includes a calibration system, a leak rate test system, a standard leak hole and an auxiliary air extraction system. The calibration system and the leak rate test system both include a mechanical pump (1), a solenoid valve (2), a vacuum plug valve (5), a vacuum gauge (6) and a quadrupole mass spectrometer (7); The calibration system also includes a front molecular pump (3), a main molecular pump (4), a pressure stabilization chamber (8), an air pumping hole (9) and a calibration chamber (10); The leak rate test system further includes a molecular pump (11), a vacuum container (12) and a product to be tested (13); The standard leak holes include hand valve 1 (14), air extraction hole 2 (15), hand valve 2 (16), vacuum gauge 2 (17), hand valve 3 (18), working fluid container (19) and hand valve 4 (20); The auxiliary pumping system includes a molecular pump 2 (21), a solenoid valve 2 (22) and a mechanical pump 2 (23); Among them, the calibration system for the liquid working fluid standard leak includes the following steps: S1, manual valve 1 (14) are in the closed state, open the calibration system mechanical pump 1 (1), the front molecular pump (3), the main molecular pump (4) and the corresponding valves, wait for the pressure of the calibration chamber (10) to stabilize, and record the pressure value of the vacuum gauge 1 (6) as P1; S2, manual valve 1 (14) and manual valve 3 (18) are in the closed state, and other vacuum pumps and valves except the calibration system are turned on to pump to the ultimate vacuum; S3, close the manual valve 4 (20), open the manual valve 3 (18), and observe that the vacuum gauge 2 (17) reaches the gas phase pressure of the working fluid under test at room temperature; S4, open the manual valve 1 (14), wait for the pressure of the calibration chamber (10) to stabilize, record the pressure value of the vacuum gauge 1 (6) as P2, observe the spectrum of the quadrupole mass spectrometer (7), and record the mass number of the peak corresponding to the working fluid mass spectrum; S5. Conductance formula through a circular hole (1) in, T ——gas temperature K; M ——Molar mass of the working fluid gas being measured kg / mol; d ——The diameter of the small exhaust hole (9) is 18mm. It is found that the flow conductance at the suction hole (9) is C 1 ; S6, the effective pumping speed S1 at the air pumping hole 1 (9) is: （2） in, C 1 ——Flow conductance at one (9) exhaust hole m 3 / s; S ——Effective pumping speed m at the pump port of the main molecular pump (4) 3 / s, S >> C 1 So, S1≈ C 1 ; S7, flow rate at the first (9) air extraction hole Q : （3） in, S ——Effective pumping speed at the air pumping hole (9) m 3 / s; P——Stable pressure value Pa of calibration room (10); S8. Since the system mass flow is equal, the standard leak rate Q0 is obtained by formula (4): （4） in, S ——Effective pumping speed at the air pumping hole (9) m 3 / s; P1——Stable pressure value Pa in the calibration chamber (10) after closing the manual valve 1 (14); P2——Stable pressure value Pa in calibration chamber (10) after opening manual valve 1 (14).

2. The method for vacuum leak detection of liquid medium for aerospace use according to claim 1, characterized in that: The pre-processing steps before testing the product under test (13) include: S1. Blowing the surface of the product to be tested (13) with high-purity nitrogen; S2. Place the product to be tested (13) in a vacuum container (12), evacuate the container, and remove the working fluid that may be adsorbed on the surface.

3. The method for vacuum leak detection of liquid medium for aerospace use according to claim 2, characterized in that: The leak rate test process of the product under test (13) includes the following steps: S1. When the product to be tested (13) is not placed in the container, the door of the vacuum container (12) is closed, and the vacuum container (12) is evacuated to the limit state; S2, the manual valve 1 (14) is in the closed state, the quadrupole mass spectrometer (7) is turned on, and the peak current value I0 of the mass spectrum of the working fluid corresponding to the quadrupole mass spectrometer (7) is recorded; S3, manual valve 1 (14) and manual valve 3 (18) are in the closed state, and other vacuum pumps and valves except the test system are turned on to pump to the ultimate vacuum; S4, close the manual valve 4 (20), open the manual valve 3 (18), and observe that the vacuum gauge 2 (17) reaches the gas phase pressure of the working fluid under test at room temperature; S5, open the manual valve 1 (14), wait for the vacuum degree to stabilize, turn on the quadrupole mass spectrometer (7), and record the peak current value I1 of the mass spectrum of the working medium corresponding to the quadrupole mass spectrometer (7); S6, placing the product to be tested (13) into the vacuum container (12), closing the door of the vacuum container (12), and evacuating the vacuum container (12) to the limit state; S7, after the vacuum degree of the vacuum container (12) is stabilized, the quadrupole mass spectrometer (7) is turned on, and the peak current value I2 of the mass spectrum of the working medium corresponding to the quadrupole mass spectrometer (7) is recorded; S8, the leakage rate Q of the tested product (13) is calculated by formula (5): （5） Where, I0 is the background value A of the working fluid being measured in the container; I1——standard leak response value A; I2——Reaction value A of the product being tested; Q0——Standard leak rate value Pa•m 3 / s .

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