Capillary tube testing device and method for detecting capillary tube flow and air tightness

Abstract

The application relates to a capillary pipeline testing device and a method for detecting the flow and air tightness of a capillary pipeline, and relates to the technical field of cable testing. The capillary pipeline testing device comprises a box body, a gas input joint fixed on a panel of the box body, an air tightness detection assembly and a flow detection assembly connected in series. The air tightness detection assembly comprises a switch A, a pressure regulating valve, a switch B, a precision pressure gauge A, an adapter A, an adapter B and a switch C connected in series on a gas path. The adapters A and B are respectively connected with cable adapter assemblies, and a cable to be detected containing a capillary is arranged between the two cable adapter assemblies. The flow detection assembly comprises a precision pressure gauge B, a metering valve and a flow meter connected in series on the gas path behind the switch C. After the cable to be detected containing the capillary pipeline is assembled in place, the switch C is rotated to realize the conversion of the air tightness detection function and the flow test function, and the flow and air tightness defects of the capillary pipeline can be found. The capillary pipeline testing device is simple to operate and convenient to use.

Description

Technical Field

[0001] This invention relates to the field of cable testing technology, and in particular to a capillary testing device and a method for detecting capillary flow rate and air tightness. Background Technology

[0002] As is well known, capillary tubes possess advantages such as good bending performance and compact structure, making them widely used in test cables. In test cables, capillary tubes are typically wound in a spring-like shape, with the central area filled with cable to increase the cable's bending lifespan. Both ends of the capillary tube are usually welded to a dedicated socket, with adjacent mating parts (specifically, dedicated pins) and then sealed with a sealing ring, thereby improving the connection efficiency of the plug and socket. However, in actual cable welding and assembly processes, due to the influence of post-weld internal stress and molten solder, the inner diameter of the capillary tube may become smaller, and the sealing ring may not be properly assembled. This can affect the flow rate and air tightness of the pipeline. Existing flow rate and air tightness testing equipment consists of two units, requiring repeated disassembly and reassembly of the cable under test containing capillary tubes. After testing on the flow rate testing equipment, the cable is disassembled and reinstalled on the air tightness testing equipment to check its air tightness. When multiple cables under test containing capillary tubes need to be tested in the above manner, the operation is cumbersome and time-consuming. Moreover, when testing needs to be conducted at different locations, both testing equipment must be carried along, which is inconvenient. Therefore, providing a capillary tube testing device to realize capillary tube flow rate testing and air tightness testing has become a basic requirement for those skilled in the art. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a capillary circuit testing device and a method for detecting capillary flow rate and airtightness.

[0004] The technical solution adopted in this invention is:

[0005] The capillary circuit testing device includes a housing, a gas input connector fixed on the housing panel, and a series-connected airtightness detection component and flow detection component. The airtightness detection component includes a switch A, a pressure regulating valve, a switch B, a precision pressure gauge A, an adapter A, an adapter B, and a switch C connected in series in the gas path. Cable adapter assemblies are connected to adapter A and adapter B respectively, and a test cable containing a capillary tube is installed between the two cable adapter assemblies. The flow detection component includes a precision pressure gauge B, a metering valve, and a flow meter connected in series in the gas path after switch C. The flow meter is fixed to a flow meter adapter base via an AN connector, and the output end of the flow meter is connected to the atmosphere.

[0006] The capillary circuit testing device, wherein any cable adapter assembly includes an adapter plug, a circular ring, and a conversion connector. The circular ring includes a handle A, a handle B, and a fixing screw. Handles A and B are arranged in a semi-circular shape and are fixed into a circular structure by screws on their outer circular surfaces. An adapter plug is fixed at one end of the circular ring and a conversion connector is fixed at the other end. The adapter plug includes a square plate and a circular ring fixed on the outer surface of the square plate. A hollow nitrogen pin and multiple conversion connector pins are fixed inside the circular ring. The nitrogen pin is located at the center of the circular ring and communicates with the center hole of the conversion connector. The conversion connector is connected to adapter A or adapter B through a metal flexible tube. A cable under test containing a capillary tube is fixed between the adapter plugs of the two cable adapter assemblies.

[0007] The capillary circuit testing device is equipped with a filter in the air line between switch A and the pressure regulating valve.

[0008] The capillary circuit testing device is equipped with a safety valve in the gas line between the metering valve and the flow meter.

[0009] The capillary circuit testing device described herein has gas input connectors, adapter A, adapter B, and cable adapter assembly all of the same specification.

[0010] The capillary circuit testing device described herein uses a three-way switch B, which enables input conduction, closure, and pressure relief functions.

[0011] The method for detecting capillary flow rate using a capillary testing device includes the following steps:

[0012] a. Select a flow meter with a matching range based on the inner diameter and flow rate of the cable to be tested containing a capillary tube;

[0013] b. Install the two ends of a test cable containing a capillary tube at adapter A and adapter B respectively through the cable adapter assembly, ensuring a sealed connection; turn on switches A, B, and C, switch B to the input conduction state, the gas source is high-pressure nitrogen with a purity ≥99.9% and a rated pressure ≥20Mpa, and introduce it into the gas circuit through the gas pipe on the gas input connector. After the gas is filtered by the filter, it enters the pressure regulating valve;

[0014] c. Adjust the air pressure through the pressure regulating valve to stabilize the pressure value P1 displayed by the precision pressure gauge A at 3-7 MPa. Rotate the handle of the metering valve to adjust the gap between the valve needle and the mating surface so that the reading P2 of the precision pressure gauge B = P1-1 MPa, ensuring that the pressure drop difference is 1 MPa. After the air pressure stabilizes, read the reading through the flow meter as the flow detection data of the cable 21 containing the capillary tube and compare it with the flow requirement of the cable specification. If the flow rate is higher than the flow requirement of the cable specification, it is a qualified cable; otherwise, it is an unqualified cable.

[0015] d. Replace with another test cable of the same specification containing a capillary tube, and repeat steps b and c above. After introducing high-pressure nitrogen into the gas circuit, the pressure value displayed by precision pressure gauge A is P1′= P1, and the reading of precision pressure gauge B is P2′= P2. If the flow rate of the capillary tube of this test cable 21 containing a capillary tube is reduced due to welding or sealing ring assembly, and the reading of the flow meter is less than the flow rate requirement of this specification of cable, then it does not meet the requirements.

[0016] The method for testing the airtightness of a capillary circuit using a capillary circuit testing device includes the following specific steps:

[0017] S1. Install both ends of the cable to be tested containing the capillary tube at adapter A and adapter B respectively through the cable adapter assembly to ensure a sealed connection;

[0018] S2. Close switch C and open switch A. The gas source is high-pressure nitrogen with a purity ≥99.9% and a rated pressure ≥20Mpa. Adjust switch B from the closed state to the input state. The gas source is introduced into the gas circuit through the gas pipe on the gas input connector. After the gas is filtered, it enters the pressure regulating valve. Rotate the pressure regulating valve to adjust the pipeline pressure. The pipeline pressure is displayed in real time by the precision pressure gauge A. After the pressure value P0 reaches the required pressure for detection, maintain the pressure for 2-3 minutes.

[0019] S3. Following the previous step, two methods are used for testing during the pressure holding period:

[0020] (1) Apply leak detection liquid: Apply leak detection liquid evenly to the capillary welding part and the sealing area of ​​the sealing ring and observe whether bubbles are generated. If bubbles are generated, it is determined that there is a leak.

[0021] (2) Pressure value observation: After the reading of the precision pressure gauge A reaches the required pressure for testing, switch B8 is adjusted from the input state to the closed state to maintain the pressure for 2-3 minutes. Read the reading of the precision pressure gauge A Pt and see if it decreases compared to P0. If the decrease is greater than 0.1 MPa, it indicates that there is air leakage in the test cable 21 containing the capillary tube.

[0022] (3) Pressure relief and replacement: After the test is completed, switch switch B to the pressure relief state to release the gas in the gas path and replace the next test cable containing the capillary tube.

[0023] Due to the adoption of the technical solution described above, the present invention has the following advantages:

[0024] The capillary circuit testing device and method for detecting capillary flow rate and airtightness described in this invention control the pressure at the input end of the cable under test containing the capillary circuit through a pressure regulating valve and the pressure at the output end of the cable under test containing the capillary circuit through a metering valve, realizing flow rate testing under different pressures and pressure drop differences. During flow rate testing, different ranges can be measured by changing flow meters with different ranges, providing comprehensive flow rate testing. The combination of pressure regulating valve, metering valve, and flow meters of different specifications makes the flow rate testing highly applicable, with functions for testing large and small flow rates, while ensuring testing accuracy. After the cable under test containing the capillary circuit is assembled in one go, turning switch C can switch between airtightness detection and flow rate testing functions, enabling airtightness testing of the capillary circuit under rated pressure, and detecting flow rate and airtightness defects in the capillary circuit. The capillary circuit testing device is simple to operate and convenient to use. Attached Figure Description

[0025] Figure 1 This is an overall schematic diagram of the capillary circuit testing device of the present invention.

[0026] Figure 2 This is a schematic diagram of the cable adapter assembly of the present invention.

[0027] Figure 3 This is a schematic diagram of the structure of the conversion connector of the cable adapter assembly of the present invention.

[0028] Figure 4 This is a schematic diagram of the measurement principle of the present invention.

[0029] In the diagram: 1. Precision pressure gauge A; 2. Precision pressure gauge B; 3. Switch A; 4. Pressure regulating valve; 5. Gas input connector; 6. Adapter A; 7. Adapter B; 8. Switch B; 9. Switch C; 10. Metering valve; 11. Flow meter adapter; 12. Flow meter; 13. Nitrogen pin; 14. Adapter plug; 15. Handshake A; 16. Handshake B; 17. Adapter pin; 18. Adapter connector; 19. Gas source; 20. Filter; 21. Test cable containing capillary tube; 22. Safety valve. Detailed Implementation

[0030] The present invention will be further explained and described below with reference to the accompanying drawings and embodiments. However, this should not be construed as limiting the scope of protection of the present invention. The purpose of disclosing the present invention is to protect all technical improvements within the scope of the present invention.

[0031] Combined with appendix Figure 1-4The capillary circuit testing device includes a housing, a gas input connector 5 fixed on the housing panel, and a series-connected airtightness detection component and flow detection component. The housing is made of high-strength aluminum alloy and has dimensions of 400mm × 300mm × 200mm. The airtightness detection component includes a switch A3, a pressure regulating valve 4, a switch B8, a precision pressure gauge A1, an adapter A6, an adapter B7, and a switch C9 connected in series in the gas path. A filter 20 is installed in the gas path between switch A3 and pressure regulating valve 4. The filter 20 has a filtration accuracy of 4μm and is used to filter solids in the gas source 19. Impurities; cable adapter assemblies are connected to adapters A6 and B7 respectively, and a test cable 21 containing a capillary tube is installed between the two cable adapter assemblies; the flow detection assembly includes a precision pressure gauge B2, a metering valve 10, and a flow meter 12 connected in series in the air circuit after switch C9. A safety valve 22 is provided in the air circuit between the metering valve 10 and the flow meter 12. The flow meter 12 is fixed to the flow meter adapter 11 through the AN connector to facilitate the replacement of flow meters 12 of different specifications. After installation, the flow meter 12 is in a vertical position for easy and accurate reading. The output end of the flow meter 12 is connected to the atmosphere;

[0032] Specifically, since the output of flow meter 12 is connected to the atmosphere, the gas path between metering valve 10 and flow meter 12, i.e., the auxiliary... Figure 4 The measured pressure at point A is close to a standard atmospheric pressure. Considering that the rated pressure resistance of flowmeter 12 is generally low, less than the working pressure of the capillary tube, if there is a blockage in the air passage inside flowmeter 12, the pressure at point A will rise sharply. If the pressure exceeds the rated pressure resistance of the flowmeter, a safety accident will occur. Therefore, a safety valve 22 is added at point A. The opening pressure of safety valve 22 is set to 0.3-0.5 MPa, which is between one standard atmosphere and the rated pressure resistance of flowmeter 12. For pressures ≥0.8 MPa, the metering valve 10 is a small-orifice needle valve. By rotating the handle of the metering valve 10, the gap between the valve needle and the mating surface can be adjusted, thereby adjusting the internal flow rate of the gas path. The internal gas energy is conserved. Under the condition that the potential energy remains unchanged and is highly consistent, if the gas flow rate increases, the kinetic energy of the gas passing through the capillary tube increases, and the static pressure of the gas decreases. That is, the reading P2 of the precision pressure gauge B2 is lower than the reading P1 of the precision pressure gauge A1. Therefore, the reading P2 of the precision pressure gauge B2 can be adjusted by rotating the handle of the metering valve 10.

[0033] Furthermore, any cable adapter assembly includes an adapter plug 14, a circular ring, and a conversion connector 18. The circular ring includes a handle A15, a handle B16, and a fixing screw. The handles A15 and B16 are arranged in a semi-circular shape and are connected and fixed into a circular structure by the fixing screw on the outer circular surface. The adapter plug 14 is fixed to one end of the circular ring by a screw, and the conversion connector 18 is fixed to the other end by a screw. The adapter plug 14 includes a square plate and a ring fixed to the outer surface of the square plate. A hollow nitrogen pin 13 and multiple conversion connector pins 17 are fixed inside the ring. The nitrogen pin 13 is located at the center and communicates with the center hole of the conversion connector 18. The conversion connector 18 is connected to the conversion connector A6 or the conversion connector B7 through a high-voltage resistant metal flexible hose. A test cable 21 containing a capillary tube is fixed between the adapter plugs 14 of the two cable adapter assemblies. The multiple conversion connector pins 17 are used for precise positioning of the adapter plug 14 and the test cable 21 containing the capillary tube to achieve electrical connection.

[0034] Furthermore, the gas input connector 5, adapter A6, adapter B7, and cable adapter assembly are all connectors of the same specification.

[0035] Furthermore, switch B8 is a three-way switch valve, which realizes the input on, off and depressurization functions respectively. In the depressurization state, it can quickly discharge the gas in the downstream air circuit, which facilitates the replacement of the test cable 21 containing the capillary tube.

[0036] The method for detecting capillary flow rate using a capillary testing device includes the following steps:

[0037] a. Select a flow meter 12 with a matching range based on the inner diameter and flow rate of the cable 21 containing the capillary tube to be tested;

[0038] b. Install the two ends of a test cable 21 containing a capillary tube at adapter A6 and adapter B7 respectively through the cable adapter assembly, ensuring a sealed connection; turn on switch A3, switch B8 and switch C9, switch B8 to the input conduction state, the gas source 19 is high-pressure nitrogen with a purity ≥99.9% and a rated pressure ≥20Mpa, and enter the gas circuit through the gas pipe on the gas input connector 5. After the gas is filtered by filter 20, it enters the pressure regulating valve 4;

[0039] c. Adjust the air pressure through the pressure regulating valve 4 to stabilize the pressure value P1 displayed by the precision pressure gauge A1 at 3-7 MPa. Rotate the handle of the metering valve 10 to adjust the gap between the valve needle and the mating surface so that the reading P2 of the precision pressure gauge B2 = P1-1 MPa, ensuring that the pressure drop difference is 1 MPa. After the air pressure stabilizes, read the reading through the flow meter 12 as the flow detection data of the cable 21 containing the capillary tube and compare it with the flow requirement of the cable specification. If the flow rate is higher than the flow requirement of the cable specification, it is a qualified cable; otherwise, it is an unqualified cable.

[0040] d. Replace with another test cable 21 of the same specification containing a capillary tube, and repeat steps b and c above. After introducing high-pressure nitrogen into the gas circuit, the pressure value displayed by precision pressure gauge A1 is P1′= P1, and the reading of precision pressure gauge B2 is P2′= P2. If the flow rate of the capillary tube of this test cable 21 containing a capillary tube is reduced due to welding or sealing ring assembly, and the reading of flow meter 12 is less than the flow rate requirement of this specification of cable, then it does not meet the requirements.

[0041] The method for testing the airtightness of a capillary circuit using a capillary circuit testing device includes the following specific steps:

[0042] S1. Install both ends of the test cable 21 containing the capillary tube at adapter A6 and adapter B7 respectively through the cable adapter assembly to ensure a sealed connection;

[0043] S2. Close switch C9 and open switch A3. The gas source 19 is high-pressure nitrogen with a purity of ≥99.9% and a rated pressure of ≥20Mpa. Adjust switch B8 from the closed state to the input state. The gas source 19 enters the gas circuit through the gas pipe on the gas input connector 5. After the gas is filtered by filter 20, it enters the pressure regulating valve 4. Rotate the pressure regulating valve 4 to adjust the pipeline pressure. The pipeline pressure is displayed in real time by the precision pressure gauge A1. After the pressure value P0 reaches the required pressure for detection, the pressure is maintained for 2-3 minutes.

[0044] S3. Following the previous step, two methods are used for testing during the pressure holding period:

[0045] (1) Apply leak detection liquid: Apply leak detection liquid evenly to the capillary welding part and the sealing area of ​​the sealing ring and observe whether bubbles are generated. If bubbles are generated, it is determined that there is a leak.

[0046] (2) Pressure value observation: After the reading of the precision pressure gauge A1 reaches the required pressure for testing, switch B8 is adjusted from the input state to the closed state to maintain the pressure for 2-3 minutes. Read the reading of the precision pressure gauge A1 Pt and compare it with P0. If the decrease is greater than 0.1 MPa, it indicates that there is air leakage in the test cable 21 containing the capillary tube.

[0047] (3) Pressure relief and replacement: After the test is completed, switch switch B8 to the pressure relief state to release the gas in the gas path and replace the next test cable 21 containing the capillary tube.

[0048] Example 1:

[0049] Flow detection: The test cable 21 containing a capillary tube has an inner diameter of 0.7 mm and a flow rate requirement of not less than 100 L / min. Select a flow meter with a range of 0-200 L / min. Install and fix the test cable 21 containing the capillary tube through the cable adapter assembly. Turn on switch A3, switch B8 (input on), and switch C9 to introduce high-pressure nitrogen. Adjust the pressure regulating valve 4 to make P1 of precision pressure gauge A1 = 7 MPa, and rotate the metering valve 10 to make P2 of precision pressure gauge B2 = 6 MPa. After the gas pressure stabilizes, read the value of flow meter 12 as 110 L / min, which is higher than the flow rate requirement. Therefore, it is determined that the test cable 21 containing the capillary tube meets the requirements. Replace with another test cable 21 of the same specification containing a capillary tube and repeat the operation. Read the value of flow meter as 95 L / min, which is lower than the flow rate requirement. Therefore, it is determined that the flow rate of this test cable 21 containing the capillary tube does not meet the requirements.

[0050] Air tightness test: The rated working pressure of the test cable 21 containing the capillary tube is 16MPa, and the test pressure is set to 19.2MPa. The test cable 21 containing the capillary tube is installed and fixed through the cable adapter assembly. Switch C9 is closed, switch A3 is opened, and switch B8 is switched to the input state. High-pressure nitrogen is introduced and the pressure regulating valve 4 is adjusted so that the reading P0 of the precision pressure gauge A1 is 19.2MPa. The pressure is maintained in the input state for 2 minutes. During the pressure holding period, leak detection liquid is evenly applied to the capillary tube welding part and the sealing area of ​​the sealing ring to observe whether bubbles are generated. No bubbles were generated in this operation, and the air tightness of this test cable 21 containing the capillary tube is determined to be qualified. After the test is completed, switch B8 is switched to the depressurization state to release the gas in the gas circuit.

[0051] Replace the cable 21 with the same specification and the capillary tube, and repeat the test operation. During the pressure holding period, observe that the reading P0 of the precision pressure gauge A1 reaches 19.2MPa. Then, adjust the switch B8 from the input state to the closed state, hold the pressure for 2 minutes, and read the reading Pt of the precision pressure gauge A1 as 19MPa. Compared with P0, it is more than 0.1MPa lower, indicating that this cable 21 with the capillary tube has an air leakage.

[0052] The parts of this invention not described in detail are prior art.

[0053] The embodiments selected herein for the purpose of disclosing the inventive objectives are currently considered suitable; however, it should be understood that the invention is intended to include all variations and modifications of the embodiments that fall within the scope of this concept and invention.

Claims

1. A capillary circuit testing device, comprising a housing, a gas input connector fixed on the housing panel, and an airtightness detection component and a flow detection component connected in series; characterized in that: The airtightness testing assembly includes a switch A, a pressure regulating valve, a switch B, a precision pressure gauge A, an adapter A, an adapter B, and a switch C connected in series on the air path; cable adapter assemblies are connected to adapter A and adapter B respectively, and a test cable containing a capillary tube is installed between the two cable adapter assemblies; a filter is installed in the air path between switch A and the pressure regulating valve; the flow rate testing assembly includes a precision pressure gauge B, a metering valve, and a flow meter connected in series on the air path after switch C; a safety valve is installed in the air path between the metering valve and the flow meter; the flow meter is fixed to the flow meter adapter base via an AN connector, and the output end of the flow meter is connected to the atmosphere; any cable adapter assembly includes a... The system includes a connector, a ring component, and an adapter. The ring component comprises a handle A, a handle B, and a fixing screw. Handles A and B are arranged in a semi-circular shape and are fixed into a circular structure by screws on their outer surfaces. An adapter connector is fixed to one end of the ring component, and an adapter connector is fixed to the other end. The adapter connector includes a square plate and a ring component fixed to the outer surface of the square plate. A hollow nitrogen pin and multiple adapter pins are fixed inside the ring component. The nitrogen pin is located at the center of the ring component and communicates with the center hole of the adapter connector. The adapter connector is connected to adapter A or adapter B via a metal flexible tube. A cable under test containing a capillary tube is fixed between the adapter connectors of the two cable adapter assemblies.

2. The capillary circuit testing device according to claim 1, characterized in that: The gas input connector, adapter A, adapter B and cable adapter assembly are all of the same specification.

3. The capillary circuit testing device according to claim 1, characterized in that: Switch B is a three-way switch valve, which realizes the functions of input opening, closing and pressure relief respectively.

4. A method for detecting capillary flow rate using the capillary testing device as described in any one of claims 1-3, comprising the following steps: a. Select a flow meter with a matching range based on the inner diameter and flow rate of the cable to be tested containing a capillary tube; b. Install both ends of a test cable containing a capillary tube at adapter A and adapter B respectively through a cable adapter assembly, ensuring a sealed connection; Turn on switches A, B, and C. Switch B is switched to the input conduction state. The gas source is high-pressure nitrogen with a purity of ≥99.9% and a rated pressure of ≥20Mpa. The gas is introduced into the gas circuit through the gas pipe on the gas input connector. After being filtered by the filter, the gas enters the pressure regulating valve. c. Adjust the air pressure through the pressure regulating valve to stabilize the pressure value P1 displayed by the precision pressure gauge A at 3-7 MPa. Rotate the handle of the metering valve to adjust the gap between the valve needle and the mating surface so that the reading P2 of the precision pressure gauge B = P1 - 1 MPa, ensuring that the pressure drop difference is 1 MPa. After the air pressure stabilizes, read the reading through the flow meter as the flow detection data of the cable under test and compare it with the flow requirement of the cable under test. If the flow rate is higher than the flow requirement of the cable under test, it is a qualified cable; otherwise, it is an unqualified cable. d. Replace with another cable of the same specification containing a capillary tube and repeat steps b and c above. After introducing high-pressure nitrogen into the gas circuit, the pressure value displayed by precision pressure gauge A is P1′= P1, and the reading of precision pressure gauge B is P2′= P2. If the flow rate of the capillary tube of this cable is reduced due to welding or the assembly of the sealing ring, and the reading of the flow meter is less than the flow rate requirement of this specification of cable, then it does not meet the requirements. The capillary circuit testing device described herein is used to test the airtightness of a capillary circuit. The specific steps include: S1. Install both ends of the cable to be tested containing the capillary tube at adapter A and adapter B respectively through the cable adapter assembly to ensure a sealed connection; S2. Close switch C and open switch A. The gas source is high-pressure nitrogen with a purity ≥99.9% and a rated pressure ≥20Mpa. Adjust switch B from the closed state to the input state. The gas source is introduced into the gas circuit through the gas pipe on the gas input connector. After the gas is filtered, it enters the pressure regulating valve. Rotate the pressure regulating valve to adjust the pipeline pressure. The pipeline pressure is displayed in real time by the precision pressure gauge A. After the pressure value P0 reaches the required pressure for detection, maintain the pressure for 2-3 minutes. S3. Following the previous step, two methods are used for testing during the pressure holding period: (1) Applying leak detection liquid: Apply leak detection liquid evenly to the capillary welding part and the sealing area of ​​the sealing ring and observe whether bubbles are generated. If bubbles are generated, it is determined that there is a leak; (2) Observing the pressure value: After the value of the precision pressure gauge A reaches the required pressure for testing, switch B is adjusted from the input state to the closed state and pressure is held for 2-3 minutes. Read the value Pt of the precision pressure gauge A and see if it is lower than P0. If the decrease is greater than 0.1 MPa, it indicates that there is a leak in the cable under test; (3) Depressurizing and replacing: After the test is completed, switch B to the depressurizing state, release the gas in the gas path, and replace the next cable under test containing the capillary tube.

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