A cold outer cylinder vacuum leak detection device and detection method

Abstract

The application discloses a cold outer cylinder vacuum leak detection device and a detection method, relates to the technical field of vacuum leak detection, and provides the following scheme, which comprises a cold outer cylinder assembly, a vacuum air extraction system, a helium supply system, a detection system and a control system. The cold outer cylinder assembly comprises a cold outer cylinder body, a refrigeration unit and a temperature monitoring unit, is used for regulating the temperature in the inner cavity of the cold outer cylinder body to a preset low-temperature range and collecting the inner cavity temperature data in real time. The vacuum air extraction system comprises a mechanical forepump, a molecular pump, a low-temperature adsorption trap and a vacuum valve group which are connected in sequence and is used for extracting the inner cavity of the cold outer cylinder body and the inside of the detected part to a preset vacuum degree. The application can simulate low-temperature working conditions, accurately control the temperature and does not need refrigerant, can detect low-temperature induced micro-leakage, reflects the actual sealing performance of the detected part, the low-temperature adsorption trap and real-time calibration ensure the detection accuracy, can detect extremely tiny leakage, can flexibly adjust the air extraction rate, accurately supply helium and locate the leakage, and improves the leak detection efficiency of large equipment.

Description

Technical Field

[0001] This invention relates to the field of vacuum leak detection technology, and in particular to a cold outer cylinder vacuum leak detection device and detection method. Background Technology

[0002] Vacuum insulation equipment (such as cryogenic insulated pressure vessels and vacuum insulated tubes) is widely used in the storage and transportation of cryogenic media such as liquid oxygen, liquid nitrogen, and liquid helium. The sealing performance of its vacuum jacket directly determines the insulation effect, operational reliability, and safety of the equipment. Leakage rate, as a core technical indicator, must be strictly controlled. For example, the leakage rate of cryogenic insulated pressure vessels used for transportation is typically required to be less than 1×10⁻⁶. -9 Pa·m 3 Therefore, accurate and efficient detection of leak rates in such equipment is crucial. Among existing vacuum leak detection technologies, helium mass spectrometry leak detection is widely used due to its advantages such as high sensitivity and accurate positioning. It mainly includes splitless detection, split detection, and suction gun method. However, for vacuum equipment used in low-temperature conditions, existing technologies have the following shortcomings: First, conventional leak detection devices do not consider the impact of low-temperature environment on detection. When the equipment is in a low-temperature working state, the difference in thermal shrinkage of materials can easily lead to changes in the stress of the sealing structure, which may produce micro-leaks that are not detected at room temperature. The results of room temperature leak detection cannot truly reflect the sealing performance of the equipment under actual working conditions. Second, in a low-temperature environment, impurity gases such as water vapor and nitrogen are easy to condense on the surface of the equipment. This not only interferes with the detection signal of tracer gas (such as helium) but may also temporarily block the leak, resulting in inaccurate leak rate measurement. Third, for large-scale low-temperature insulation equipment, the existing pumping system is difficult to quickly establish a stable vacuum background, resulting in long detection response time, low efficiency, and difficulty in achieving accurate positioning and quantitative detection of leaks.

[0003] Therefore, there is an urgent need to develop a vacuum leak detection device and corresponding detection method that can simulate low-temperature working conditions, has high detection accuracy, fast response speed and simple structure, so as to solve the shortcomings of existing technologies in leak detection of vacuum equipment under low-temperature working conditions. Summary of the Invention

[0004] The present invention provides a vacuum leak detection device and method for a cold outer cylinder, which solves the above-mentioned shortcomings of the prior art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A cold outer cylinder vacuum leak detection device includes a cold outer cylinder assembly, a vacuum pumping system, a helium supply system, a detection system, and a control system. The cold outer cylinder assembly includes a cold outer cylinder body, a refrigeration unit, and a temperature monitoring unit, which are used to regulate the internal cavity temperature of the cold outer cylinder body to a preset low temperature range and to collect internal cavity temperature data in real time.

[0007] The vacuum pumping system includes a mechanical back pump, a molecular pump, a cryogenic adsorption trap and a vacuum valve group connected in sequence, which are used to pump the inner cavity of the cold outer cylinder and the inside of the test piece to a preset vacuum level.

[0008] The helium supply system includes a helium cylinder, a pressure reducing valve, a flow controller, and a helium hood, used to precisely inject helium into the area to be tested.

[0009] The detection system includes an ammonia gas chromatography leak detector, a standard leak hole, a differential pressure sensor, and a vacuum gauge tube, used to detect the partial pressure of helium in the inner cavity of the cold outer cylinder and to calibrate the leak detector in real time.

[0010] The control system is electrically connected to the refrigeration unit, temperature monitoring unit, vacuum pumping system, helium supply system, and detection system, respectively, and is used to receive signals from each monitoring unit and control the operating parameters of each system.

[0011] Furthermore, the inner cavity of the cold outer cylinder body is used to accommodate the test piece, the refrigeration unit is fitted to the inner wall of the cold outer cylinder body, the temperature monitoring unit is embedded in the inner wall of the cold outer cylinder body, the vacuum valve group is connected to the cold outer cylinder body through a vacuum pipe, and the low-temperature adsorption trap is used to adsorb impurity gases during the pumping process to reduce the vacuum background noise.

[0012] Furthermore, the helium cylinder is connected to the helium hood in sequence via a pressure reducing valve and a flow controller. The helium hood is detachably fitted onto the outside of the area to be tested of the workpiece. The ammonia gas chromatography leak detector is connected to the cold outer cylinder body via a detection pipe. The standard leak hole is connected to the detection pipe via a calibration valve. The differential pressure sensor is used to detect the pressure difference between the inside of the workpiece and the inner cavity of the cold outer cylinder body. The vacuum gauge is used to monitor the vacuum level of the inner cavity of the cold outer cylinder body in real time.

[0013] Furthermore, the refrigeration unit adopts a closed-loop GM refrigerator with a refrigeration temperature range of 10K-100K and a temperature control accuracy of ±0.5K. It does not require the consumption of liquid helium and liquid nitrogen refrigerants, achieving stable and efficient low-temperature environment simulation. The inner wall of the outer cylinder is also provided with a heat insulation layer, which uses vacuum insulation material to reduce cold loss and improve temperature stability.

[0014] Furthermore, the vacuum valve assembly includes a main pump valve, a diverter valve, and an auxiliary pump valve. The main pump valve is located on the main pumping pipe between the molecular pump and the cold outer cylinder body. One end of the diverter valve is fixedly connected to the main pumping pipe, and the other end is connected to the auxiliary pump. The auxiliary pump valve is located between the diverter valve and the auxiliary pump. By controlling the opening degree of the diverter valve and the auxiliary pump valve, the pumping rate can be adjusted, the detection response time can be shortened, and the leak detection requirements of test pieces with different volumes can be adapted.

[0015] Furthermore, the helium hood is a flexible sealing hood with several evenly distributed helium injection holes on its inner side, and a sealing gasket is provided at the contact part between the helium hood and the workpiece under test. The flow controller is a high-precision mass flow controller with a flow adjustment range of 0-100 sccm to ensure precise control of the helium supply.

[0016] Furthermore, the detection system also includes a data acquisition module, which is connected to the ammonia gas gas spectrometer leak detector, differential pressure sensor, vacuum gauge and temperature monitoring unit respectively, for real-time storage of temperature, vacuum degree, helium partial pressure and pressure difference detection data, and transmits the data to the host computer through the communication interface.

[0017] A method for detecting leaks in a cold outer cylinder vacuum leak detection device, applicable to any of the aforementioned cold outer cylinder vacuum leak detection devices, includes the following steps:

[0018] S1. Device debugging and calibration: Turn on the control system and preheat the ammonia gas mass spectrometer leak detector; introduce helium with a known leak rate into the detection pipeline through the standard leak hole to calibrate the ammonia gas mass spectrometer leak detector, set the leak detection sensitivity threshold, and check the operating status of the vacuum pumping system, helium supply system and refrigeration unit to ensure that each component is working properly.

[0019] S2. Installation and Pre-treatment of the Test Component: Fix the test component inside the cold outer cylinder body, ensuring no contact between the test component and the cold outer cylinder body. Based on the actual operating temperature of the test component, set the target temperature of the refrigeration unit through the control system. Place the helium hood over the area to be tested on the test component, ensuring a reliable seal. Close the sealing door of the cold outer cylinder body, turn on the vacuum pumping system, and use the mechanical forepump and molecular pump in conjunction to pump air. Simultaneously, start the cryogenic adsorption trap to remove impurity gases until the vacuum degree inside the cold outer cylinder body reaches 1×10⁻⁶. -7 Below Pa, maintain a vacuum state for 30-60 minutes to complete the pretreatment;

[0020] S3. Low-temperature environment establishment: Start the refrigeration unit and adjust the refrigeration power according to the temperature data fed back in real time by the temperature monitoring unit to stabilize the temperature of the inner cavity of the outer cylinder body within the target temperature range of ±0.5K. Keep it warm for 20-40 minutes to ensure that the temperature of the tested part is consistent with the ambient temperature.

[0021] S4. Leak Detection: Keep the vacuum pumping system running continuously, turn on the helium supply system, adjust the helium pressure through the pressure reducing valve, control the helium flow rate through the flow controller, and introduce helium into the helium hood to maintain the helium pressure inside the helium hood at 0.1-0.3MPa. At the same time, turn on the ammonia gas gas spectrometer leak detector and differential pressure sensor to collect the helium partial pressure signal and the pressure difference signal inside and outside the tested part in real time, and transmit the data to the control system.

[0022] If the helium partial pressure signal detected by the ammonia gas gas spectrometer exceeds the sensitivity threshold, and the differential pressure sensor detects a continuous change in pressure difference, it is determined that there is a leak in the tested part. The leak is located by moving the helium hood to different areas of the tested part and recording the position corresponding to the peak value of the helium partial pressure. The leak rate of the tested part is calculated based on the standard leak calibration curve and the detected helium partial pressure value.

[0023] If the helium partial pressure signal does not exceed the sensitivity threshold and the pressure difference is stable within the preset detection time (30-60 min), the tested part is deemed to be sealed successfully.

[0024] S5. End of test and reset: Turn off the helium supply system, continue to run the vacuum pumping system for 20-30 minutes to remove residual helium from the inner cavity of the cold outer cylinder and the surface of the tested part, turn off the refrigeration unit, allow the inner cavity of the cold outer cylinder to naturally warm up to room temperature, turn off the vacuum pumping system, open the sealing door of the cold outer cylinder, and take out the tested part; organize the test data and generate a leak detection report.

[0025] Furthermore, in step S4, for large test pieces with a volume greater than 5m³, the auxiliary pump and auxiliary pump valve are turned on, and the opening of the diversion valve is adjusted so that the pumping rate ratio between the main pumping pipe and the diversion pipe is 3:1-5:1, thereby shortening the helium response time and improving the detection efficiency.

[0026] Furthermore, in step S4, if a leak is detected, the helium flow rate is adjusted (50-100 sccm), and the detection is repeated 2-3 times to ensure the accuracy of the leak rate measurement results. For extremely small leaks with a leak rate of less than 1×10-14 Pa·m³ / s, a cumulative leak detection mode is adopted, and the detection time is extended to 120-180 min. The helium partial pressure signal is accumulated through the data acquisition module to improve the detection rate of extremely small leaks.

[0027] Compared with existing technologies, the beneficial effects of this invention are:

[0028] 1. This invention simulates the actual low-temperature working conditions of the tested part through a cold outer cylinder assembly, and uses a closed-loop GM refrigerator to achieve precise temperature control within the range of 10K-100K without consuming refrigerant. It can not only detect low-temperature induced micro-leakage that is difficult to detect at room temperature, but also truly reflect the sealing performance of the tested part under actual working conditions, making the test results more reliable and valuable for reference.

[0029] 2. This invention incorporates a low-temperature adsorption trap in the vacuum pumping system, which effectively adsorbs impurities such as water vapor and nitrogen under low-temperature conditions, significantly reducing vacuum background noise. Simultaneously, the ammonia gas chromatography-mass spectrometry leak detector is calibrated in real-time using a standard leak hole to ensure detection accuracy, achieving a 1×10⁻⁶ ohmmeter. -16 The detection of extremely small leaks at the Pa·m³ / s level solves the problems of large interference and inaccurate measurement in low-temperature environments.

[0030] 3. By setting up a diversion valve and an auxiliary pump, the present invention can flexibly adjust the pumping rate according to the volume of the tested part, shorten the detection response time, and use a flexible helium hood to achieve precise helium supply to the area to be tested. With the help of a movable helium hood, leaks can be quickly located, which greatly improves the leak detection efficiency of large-scale cryogenic insulation equipment.

[0031] 4. The device of the present invention has a simple structure and is easy to operate. The control system realizes full-process automated control and data acquisition, which reduces the intensity of manual operation. The detection method takes into account the detection needs of conventional leaks and micro leaks. It is compatible with low temperature vacuum equipment of different types and volumes, has a wide range of applications, and has good prospects for promotion and application.

[0032] In summary, this device and method can simulate low-temperature operating conditions, accurately control the temperature without the need for refrigerant, detect low-temperature induced micro-leaks, reflect the actual sealing performance of the tested parts, and ensure detection accuracy through the low-temperature adsorption trap and real-time calibration. It can detect extremely small leaks, flexibly adjust the pumping rate, accurately supply helium and locate leaks, thus improving the leak detection efficiency of large equipment. Attached Figure Description

[0033] Figure 1 This is a block diagram of the modular layout structure of the cold outer cylinder vacuum leak detection device and detection method proposed in this invention;

[0034] Figure 2 This is a flowchart of a vacuum leak detection device and method for a cold outer cylinder proposed in this invention. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0036] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0037] Example 1

[0038] Reference Figure 1A cold outer cylinder vacuum leak detection device includes a cold outer cylinder assembly, a vacuum pumping system, a helium supply system, a detection system, and a control system. The cold outer cylinder assembly includes a cold outer cylinder body, a refrigeration unit, and a temperature monitoring unit. The inner cavity of the cold outer cylinder body is used to accommodate the test piece. The refrigeration unit is fitted into the inner wall of the cold outer cylinder body to regulate the temperature of the inner cavity of the cold outer cylinder body to a preset low temperature range. The temperature monitoring unit is embedded in the inner wall of the cold outer cylinder body to collect the inner cavity temperature data in real time.

[0039] The vacuum pumping system includes a mechanical backing pump, a molecular pump, a cryogenic adsorption trap, and a vacuum valve group connected in sequence. The vacuum valve group is connected to the cold outer cylinder body through a vacuum pipe and is used to pump the inner cavity of the cold outer cylinder body and the inside of the test piece to a preset vacuum level. The cryogenic adsorption trap is used to adsorb impurity gases during the pumping process and reduce the vacuum background noise.

[0040] The helium supply system includes a helium cylinder, a pressure reducing valve, a flow controller, and a helium hood. The helium cylinder is connected to the helium hood in sequence through the pressure reducing valve and the flow controller. The helium hood is detachably fitted onto the outside of the area to be inspected on the test piece, and is used to accurately spray helium into the area to be inspected. The helium hood is a flexible sealing cover with several evenly distributed helium injection holes on its inner side, and a sealing gasket is provided at the contact point between the helium hood and the test piece. The flow controller adopts a high-precision mass flow controller with a flow adjustment range of 0-100 sccm to ensure precise control of the helium supply.

[0041] The detection system includes an ammonia gas chromatography-mass spectrometry leak detector, a standard leak hole, a differential pressure sensor, and a vacuum gauge tube. The ammonia gas chromatography-mass spectrometry leak detector is connected to the cold outer cylinder body through a detection pipe and is used to detect the partial pressure of helium in the inner cavity of the cold outer cylinder body. The standard leak hole is connected to the detection pipe through a calibration valve and is used to calibrate the leak detector in real time. The differential pressure sensor is used to detect the pressure difference between the inside of the tested part and the inner cavity of the cold outer cylinder body. The vacuum gauge tube is used to monitor the vacuum degree of the inner cavity of the cold outer cylinder body in real time. It also includes a data acquisition module, which is connected to the ammonia gas chromatography-mass spectrometry leak detector, the differential pressure sensor, the vacuum gauge tube, and the temperature monitoring unit respectively. It is used to store the temperature, vacuum degree, helium partial pressure, and pressure difference detection data in real time and transmit the data to the host computer through the communication interface.

[0042] The control system is electrically connected to the refrigeration unit, temperature monitoring unit, vacuum pumping system, helium supply system, and detection system. It receives signals from each monitoring unit and controls the operating parameters of each system. The refrigeration unit uses a closed-loop GM refrigerator with a refrigeration temperature range of 10K-100K and a temperature control accuracy of ±0.5K. It does not consume liquid helium or liquid nitrogen refrigerant, achieving stable and efficient low-temperature environment simulation. The inner wall of the outer cylinder is also equipped with an insulation layer made of vacuum insulation material to reduce cold loss and improve temperature stability.

[0043] In this invention, the vacuum valve assembly includes a main pump valve, a diverter valve, and an auxiliary pump valve. The main pump valve is located on the main pumping pipe between the molecular pump and the cold outer cylinder body. One end of the diverter valve is fixedly connected to the main pumping pipe, and the other end is connected to the auxiliary pump. The auxiliary pump valve is located between the diverter valve and the auxiliary pump. By controlling the opening degree of the diverter valve and the auxiliary pump valve, the pumping rate is adjusted, the detection response time is shortened, and the leak detection requirements of test pieces with different volumes are adapted.

[0044] Example 2

[0045] Reference Figure 2 A method for detecting leaks in a cold outer cylinder vacuum leak detection device, applicable to the aforementioned cold outer cylinder vacuum leak detection device, includes the following steps:

[0046] S1. Device debugging and calibration: Turn on the control system and preheat the ammonia gas mass spectrometer leak detector; introduce helium with a known leak rate into the detection pipeline through the standard leak hole to calibrate the ammonia gas mass spectrometer leak detector, set the leak detection sensitivity threshold, and check the operating status of the vacuum pumping system, helium supply system and refrigeration unit to ensure that each component is working properly.

[0047] S2. Installation and Pre-treatment of the Test Component: Fix the test component inside the cold outer cylinder body, ensuring no contact between the test component and the cold outer cylinder body. Based on the actual operating temperature of the test component, set the target temperature of the refrigeration unit through the control system. Place the helium hood over the area to be tested on the test component, ensuring a reliable seal. Close the sealing door of the cold outer cylinder body, turn on the vacuum pumping system, and use the mechanical forepump and molecular pump in conjunction to pump air. Simultaneously, start the cryogenic adsorption trap to remove impurity gases until the vacuum degree inside the cold outer cylinder body reaches 1×10⁻⁶. -7 Below Pa, maintain a vacuum state for 30-60 minutes to complete the pretreatment;

[0048] S3. Low-temperature environment establishment: Start the refrigeration unit and adjust the refrigeration power according to the temperature data fed back in real time by the temperature monitoring unit to stabilize the temperature of the inner cavity of the outer cylinder body within the target temperature range of ±0.5K. Keep it warm for 20-40 minutes to ensure that the temperature of the tested part is consistent with the ambient temperature.

[0049] S4. Leak Detection: Keep the vacuum pumping system running continuously, turn on the helium supply system, adjust the helium pressure through the pressure reducing valve, control the helium flow rate through the flow controller, and introduce helium into the helium hood to maintain the helium pressure inside the helium hood at 0.1-0.3MPa. At the same time, turn on the ammonia gas gas spectrometer leak detector and differential pressure sensor to collect the helium partial pressure signal and the pressure difference signal inside and outside the tested part in real time, and transmit the data to the control system.

[0050] If the helium partial pressure signal detected by the ammonia gas gas spectrometer exceeds the sensitivity threshold, and the differential pressure sensor detects a continuous change in pressure difference, it is determined that there is a leak in the tested part. The leak is located by moving the helium hood to different areas of the tested part and recording the position corresponding to the peak value of the helium partial pressure. The leak rate of the tested part is calculated based on the standard leak calibration curve and the detected helium partial pressure value.

[0051] If the helium partial pressure signal does not exceed the sensitivity threshold and the pressure difference is stable within the preset detection time (30-60 min), the tested part is deemed to be sealed successfully.

[0052] S5. End of test and reset: Turn off the helium supply system, continue to run the vacuum pumping system for 20-30 minutes to remove residual helium from the inner cavity of the cold outer cylinder and the surface of the tested part, turn off the refrigeration unit, allow the inner cavity of the cold outer cylinder to naturally warm up to room temperature, turn off the vacuum pumping system, open the sealing door of the cold outer cylinder, and take out the tested part; organize the test data and generate a leak detection report.

[0053] In this invention, in step S4, for large test pieces with a volume greater than 5m³, the auxiliary pump and auxiliary pump valve are turned on, and the opening of the diversion valve is adjusted so that the pumping rate ratio between the main pumping pipe and the diversion pipe is 3:1-5:1, thereby shortening the helium response time and improving the detection efficiency.

[0054] In this invention, in step S4, if a leak is detected, the helium flow rate is adjusted (50-100 sccm), and the detection is repeated 2-3 times to ensure the accuracy of the leak rate measurement results. For micro-leaks with a leak rate of less than 1×10-14 Pa·m³ / s, a cumulative leak detection mode is adopted, and the detection time is extended to 120-180 min. The helium partial pressure signal is accumulated through the data acquisition module to improve the detection rate of micro-leaks.

[0055] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A cold outer cylinder vacuum leak detection device, comprising a cold outer cylinder assembly, a vacuum pumping system, a helium supply system, a detection system, and a control system, characterized in that... ； The cold outer cylinder assembly includes a cold outer cylinder body, a refrigeration unit and a temperature monitoring unit, which are used to regulate the internal cavity temperature of the cold outer cylinder body to a preset low temperature range and collect internal cavity temperature data in real time. The vacuum pumping system includes a mechanical back pump, a molecular pump, a cryogenic adsorption trap and a vacuum valve group connected in sequence, which are used to pump the inner cavity of the cold outer cylinder and the inside of the test piece to a preset vacuum level. The helium supply system includes a helium cylinder, a pressure reducing valve, a flow controller, and a helium hood, used to precisely inject helium into the area to be tested. The detection system includes an ammonia gas chromatography leak detector, a standard leak hole, a differential pressure sensor, and a vacuum gauge tube, used to detect the partial pressure of helium in the inner cavity of the cold outer cylinder and to calibrate the leak detector in real time. The control system is electrically connected to the refrigeration unit, temperature monitoring unit, vacuum pumping system, helium supply system, and detection system, respectively, and is used to receive signals from each monitoring unit and control the operating parameters of each system.

2. The vacuum leak detection device for a cold outer cylinder according to claim 1, characterized in that, The inner cavity of the cold outer cylinder body is used to accommodate the workpiece under test. The refrigeration unit is fitted to the inner wall of the cold outer cylinder body. The temperature monitoring unit is embedded in the inner wall of the cold outer cylinder body. The vacuum valve group is connected to the cold outer cylinder body through a vacuum pipe. The low-temperature adsorption trap is used to adsorb impurity gases during the pumping process and reduce the vacuum background noise.

3. The vacuum leak detection device for a cold outer cylinder according to claim 1, characterized in that, The helium cylinder is connected to the helium hood in sequence via a pressure reducing valve and a flow controller. The helium hood is fitted onto the outside of the area to be tested on the test piece. The ammonia gas chromatography leak detector is connected to the cold outer cylinder body via a detection pipe. The standard leak hole is connected to the detection pipe via a calibration valve. The differential pressure sensor is used to detect the pressure difference between the inside of the test piece and the inner cavity of the cold outer cylinder body. The vacuum gauge is used to monitor the vacuum level of the inner cavity of the cold outer cylinder body in real time.

4. The vacuum leak detection device for a cold outer cylinder according to claim 1, characterized in that, The refrigeration unit adopts a closed-loop GM refrigerator with a refrigeration temperature range of 10K-100K and a temperature control accuracy of ±0.5K. It does not require the consumption of liquid helium and liquid nitrogen refrigerants, and achieves stable and efficient low-temperature environment simulation. The inner wall of the outer cylinder is also provided with a heat insulation layer, which uses vacuum insulation material to reduce cold loss and improve temperature stability.

5. The vacuum leak detection device for a cold outer cylinder according to claim 1, characterized in that, The vacuum valve assembly includes a main pump valve, a diversion valve, and an auxiliary pump valve. The main pump valve is located on the main pumping pipe between the molecular pump and the cold outer cylinder body. One end of the diversion valve is fixedly connected to the main pumping pipe, and the other end is connected to the auxiliary pump. The auxiliary pump valve is located between the diversion valve and the auxiliary pump. By controlling the opening degree of the diversion valve and the auxiliary pump valve, the pumping rate can be adjusted, the detection response time can be shortened, and the leak detection requirements of test pieces with different volumes can be adapted.

6. The vacuum leak detection device for a cold outer cylinder according to claim 1, characterized in that, The helium hood is a flexible sealing hood with several evenly distributed helium injection holes on its inner side. A sealing gasket is provided at the contact point between the helium hood and the workpiece under test. The flow controller is a high-precision mass flow controller with a flow adjustment range of 0-100 sccm to ensure precise control of the helium supply.

7. The vacuum leak detection device for a cold outer cylinder according to claim 1, characterized in that, The detection system also includes a data acquisition module, which is connected to the ammonia gas gas spectrometer leak detector, differential pressure sensor, vacuum gauge and temperature monitoring unit respectively. It is used to store temperature, vacuum degree, helium partial pressure and pressure difference detection data in real time, and transmit the data to the host computer through the communication interface.

8. A method for detecting leaks in a cold outer cylinder vacuum leak detection device, applicable to the cold outer cylinder vacuum leak detection device described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Device debugging and calibration: Turn on the control system and preheat the ammonia gas mass spectrometer leak detector; introduce helium with a known leak rate into the detection pipeline through the standard leak hole to calibrate the ammonia gas mass spectrometer leak detector, set the leak detection sensitivity threshold, and check the operating status of the vacuum pumping system, helium supply system and refrigeration unit to ensure that each component is working properly. S2. Installation and Pre-treatment of the Test Component: Fix the test component inside the cold outer cylinder body, ensuring no contact between the test component and the cold outer cylinder body. Based on the actual operating temperature of the test component, set the target temperature of the refrigeration unit through the control system. Place the helium hood over the area to be tested on the test component, ensuring a reliable seal. Close the sealing door of the cold outer cylinder body, turn on the vacuum pumping system, and use the mechanical forepump and molecular pump in conjunction to pump air. Simultaneously, start the cryogenic adsorption trap to remove impurity gases until the vacuum degree inside the cold outer cylinder body reaches 1×10⁻⁶. -7 Below Pa, maintain a vacuum state for 30-60 minutes to complete the pretreatment; S3. Low-temperature environment establishment: Start the refrigeration unit and adjust the refrigeration power according to the temperature data fed back in real time by the temperature monitoring unit to stabilize the temperature of the inner cavity of the outer cylinder body within the target temperature range of ±0.5K. Keep it warm for 20-40 minutes to ensure that the temperature of the tested part is consistent with the ambient temperature. S4. Leak Detection: Keep the vacuum pumping system running continuously, turn on the helium supply system, adjust the helium pressure through the pressure reducing valve, control the helium flow rate through the flow controller, and introduce helium into the helium hood to maintain the helium pressure inside the helium hood at 0.1-0.3MPa. At the same time, turn on the ammonia gas chromatography leak detector and differential pressure sensor to collect the helium partial pressure signal and the pressure difference signal inside and outside the tested part in real time, and transmit the data to the control system. S5. End of test and reset: Turn off the helium supply system, continue to run the vacuum pumping system for 20-30 minutes to remove residual helium from the inner cavity of the cold outer cylinder and the surface of the tested part, turn off the refrigeration unit, allow the inner cavity of the cold outer cylinder to naturally warm up to room temperature, turn off the vacuum pumping system, open the sealing door of the cold outer cylinder, and take out the tested part; organize the test data and generate a leak detection report.

9. The detection method of the vacuum leak detection device for a cold outer cylinder according to claim 8, characterized in that, In step S4, for large test pieces with a volume greater than 5m³, the auxiliary pump and auxiliary pump valve are turned on, and the opening of the diversion valve is adjusted so that the pumping rate ratio between the main pumping pipe and the diversion pipe is 3:1-5:1, which shortens the helium response time and improves the detection efficiency.

10. The detection method of the vacuum leak detection device for a cold outer cylinder according to claim 8, characterized in that, In step S4, if a leak is detected, the helium flow rate is adjusted, and the detection is repeated 2-3 times to ensure the accuracy of the leak rate measurement results. For leak rates less than 1×10⁻⁶, the leak rate measurement is performed as follows: -14 For micro-leaks with a pressure of Pa·m³ / s, a cumulative leak detection mode is used to extend the detection time to 120-180 minutes. The data acquisition module accumulates the helium partial pressure signal to improve the detection rate of micro-leaks.

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