Device and method for recovering inert protective gas during welding of outer conductor of radio frequency coaxial cable

Abstract

The invention relates to a device and a method for recovering inert protective gas during welding of an outer conductor of a radio-frequency coaxial cable. The welding device comprises at least one welding area used for welding the outer conductor of the radio frequency coaxial cable; the air inlet is formed in the welding area; a first connecting pipe is connected between the pumping and draining system and each welding area, and an activated carbon screen layer is arranged in each first connecting pipe; the membrane separation area is arranged at the downstream of the pumping and draining system and comprises a polyimide separation membrane unit and a mixed matrix membrane unit which are connected in series; the gravity separation tank is arranged at the downstream of the membrane separation area, a second connecting pipe is connected between the gravity separation tank and the membrane separation area, and a top outlet and a bottom outlet are formed in the top and the bottom of the gravity separation tank respectively. According to the invention, active collection of the protective gas can be carried out, and helium with relatively high concentration is finally obtained for subsequent secondary treatment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radio frequency coaxial cable manufacturing, in particular to an inert protective gas recycling device and method for radio frequency coaxial cable outer conductor welding. BACKGROUND

[0002] As a core component in modern communication systems, radar systems and high-frequency electronic devices, the welding quality of the outer conductor of the radio frequency coaxial cable directly determines the stability and reliability of signal transmission. In the welding process of the outer conductor of the radio frequency coaxial cable, inert gas is generally used for protection to prevent the outer conductor copper strip from being welded due to the local temperature being too high at the weld or being combined with oxygen and nitrogen in the air.

[0003] During the welding process of the outer conductor, helium is used, the arc is wider and the energy density is high, the heat is larger and more concentrated. When welding aluminum and other high-thermal-conductivity materials, the heat is easily lost from the welding area, the input heat of argon is insufficient, and defects such as incomplete penetration, insufficient penetration, and poor weld formation are easily produced, which requires multiple welding or a large current output. This method is low in efficiency, high in risk of deformation, and may still not guarantee root penetration. The use of helium can significantly increase heat input and penetration, and the higher voltage and energy density of the helium arc can effectively inject more heat into the workpiece, improve weld formation and reduce porosity, and increase the welding speed by more than 40%, greatly improving production efficiency. At present, argon is still widely used in the processing of the outer conductor of the radio frequency coaxial cable, but in the high-demand outer conductor welding scene, it is necessary to use helium protection.

[0004] However, helium is a non-renewable resource and is very expensive, and the price of high-purity helium is more than 10 times that of argon. In order to save resources, save costs and improve the collection efficiency of helium, helium needs to be recycled and then purified for secondary treatment by relevant manufacturers. Therefore, it is necessary to provide an inert protective gas recycling device and method for radio frequency coaxial cable outer conductor welding to recycle high-purity helium while using pure helium to weld the outer conductor of the radio frequency coaxial cable. SUMMARY

[0005] Therefore, the present application provides an inert protective gas recycling device and method for radio frequency coaxial cable outer conductor welding, which concentrates the outer conductor welding equipment of the radio frequency coaxial cable in the same workshop, actively collects the protective gas when the welding protective gas starts to release, and finally obtains high-concentration helium for subsequent secondary treatment, thereby saving costs.

[0006] To solve the above technical problems, the present application provides an inert protective gas recycling device and method for radio frequency coaxial cable outer conductor welding, comprising: at least one welding area for welding operation of the outer conductor of the radio frequency coaxial cable; An air inlet is arranged on the welding area to introduce helium and generate a first tail gas containing helium, air mixture gas and solid impurities during welding; A pumping system is connected with each welding area through a first connecting pipe, and an activated carbon sieve layer is arranged in the first connecting pipe. The pumping system is used to pump the first tail gas, and the first tail gas is dehydrated and removed of solid impurities through the activated carbon sieve layer to obtain a second tail gas. The pumping system can pressurize the second tail gas; A membrane separation zone is arranged downstream of the pumping system and includes a polyimide separation membrane unit and a mixed matrix membrane unit connected in series. The polyimide separation membrane unit is used to separate the second tail gas to separate the helium and the larger molecular gas containing nitrogen and oxygen in the air in the second tail gas to obtain a first crude helium stream. The mixed matrix membrane unit is used to separate the first crude helium stream to absorb the smaller molecular gas in the first crude helium stream to obtain a second crude helium stream containing helium and impurity gas, and the impurity gas includes argon and air mixture gas. A gravity separation tank is arranged downstream of the membrane separation zone and connected with the membrane separation zone through a second connecting pipe. The gravity separation tank is provided with a top outlet and a bottom outlet at the top and the bottom, respectively. The gravity separation tank is used to introduce the second crude helium stream and separate the helium and the impurity gas based on the density difference of the gas. The helium-rich stream is collected through the top outlet, and the impurity gas is discharged through the bottom outlet.

[0007] In an embodiment of the present application, the pumping system includes a vacuum pump and a compressor connected in series.

[0008] In an embodiment of the present application, the material of the first connecting pipe and / or the second connecting pipe is polytetrafluoroethylene.

[0009] In an embodiment of the present application, the diameter of the first connecting pipe and / or the second connecting pipe is 1m±0.1m.

[0010] In an embodiment of the present application, the height of the gravity separation tank is not less than 5m, and the radial dimension is within 4m.

[0011] In an embodiment of the present application, the material of the gravity separation tank is stainless steel.

[0012] In an embodiment of the present application, the gravity separation tank is provided with a top helium concentration detection sensor, a middle helium concentration detection sensor and a bottom helium concentration detection sensor arranged correspondingly near the top, the middle and the bottom of the gravity separation tank.

[0013] In one embodiment of the present invention, a top valve and a bottom valve are respectively provided at the top outlet and the bottom outlet.

[0014] In one embodiment of the present invention, the top valve and the bottom valve are respectively connected to a top air pump and a bottom air pump.

[0015] This invention also provides a method for recovering inert protective gas during welding of the outer conductor of a radio frequency coaxial cable. Based on the aforementioned inert protective gas recovery device for welding the outer conductor of a radio frequency coaxial cable, the recovery method includes: S1. Welding operation is performed in at least one welding area using helium as a shielding gas, while helium is introduced through an inlet, and a first tail gas containing helium, air mixture and solid impurities is generated during the welding process. S2. The extraction system uses a vacuum pump to extract the first tail gas. The first tail gas passes through an activated carbon sieve layer set in the first connecting pipe to remove moisture and solid impurities, resulting in the second tail gas. The second tail gas is then pressurized by the compressor of the extraction system. S3. The second tail gas is introduced into the membrane separation zone and sequentially passes through a polyimide separation membrane and a mixed matrix membrane for multi-stage separation. The polyimide separation membrane unit separates the larger molecular gases containing nitrogen and oxygen in the second tail gas to obtain a first crude helium stream. The mixed matrix membrane unit further separates the smaller molecular gases in the first crude helium stream to obtain a second crude helium stream containing helium and impurity gases. S4. The second coarse helium stream is introduced into the gravity separation tank through the second connecting pipe. The top valve and the bottom valve are controlled to be closed. Under static conditions, the density difference between helium and impurity gas is used to achieve stratification, so that the helium in the second coarse helium stream floats and gathers at the top of the gravity separation tank, and the impurity gas sinks to the bottom of the gravity separation tank. Meanwhile, the top helium concentration detection sensor, the middle helium concentration detection sensor, and the bottom helium concentration detection sensor monitor the helium concentration in real time; S5. In response to the helium concentration values ​​detected by the top helium concentration sensor and the middle helium concentration sensor reaching 80% or more and the value fluctuation within ±5%, and the helium concentration value detected by the bottom helium concentration sensor being less than the preset first helium concentration threshold; control the opening of the bottom valve and use the bottom air pump to extract the impurity gas that has settled to the bottom of the gravity separator at a flow rate of 1.6±0.1L / min. S6. When the helium concentration detected by the bottom helium concentration sensor is higher than the preset second helium concentration threshold, the bottom valve is closed and the top valve is opened at the same time. S7, collecting the helium-rich stream from the top outlet by the top air extraction pump, when the helium concentration detected by the top helium concentration detection sensor drops to below 70%, controlling the top air extraction pump to stop extraction, and collecting the helium-rich stream for subsequent purification.

[0016] The above technical solutions of the present application have the following advantages compared with the prior art: The inert gas recovery device and method for welding the outer conductor of the radio frequency coaxial cable can effectively remove the water and solid impurities in the first tail gas generated during the welding process by arranging the gas inlet in the welding area and cooperating with the activated carbon sieve layer in the first connecting pipe and the exhaust system, so that the gas composition for subsequent separation treatment is more pure, thereby improving the helium recovery efficiency and ensuring the improvement of the helium concentration.

[0017] The present application sets a membrane separation zone downstream of the exhaust system, and uses polyimide separation membrane units and mixed matrix membrane units connected in series to realize multi-stage separation of larger molecular gases and smaller molecular gases in the second tail gas. This structure can gradually enrich helium, significantly reduce the proportion of nitrogen, oxygen and argon impurities, and ensure the purity of helium, providing a high-quality gas source for subsequent gravity separation.

[0018] The present application sets a gravity separation tank downstream of the membrane separation zone, and separates based on the density difference of the gas, which can realize efficient layering of helium and impurity gas without additional energy consumption. The helium-rich stream is collected through the top outlet, and the impurity gas is discharged through the bottom outlet, thereby realizing low-cost recovery of helium under the premise of simple structure.

[0019] The present application sets helium concentration detection sensors at the top, middle and bottom of the gravity separation tank, and cooperates with the top valve, bottom valve and connected air extraction pump to realize real-time monitoring and dynamic control of the helium concentration. This design ensures the stability and reliability of helium collection, avoids premature extraction or helium loss, and improves the helium recovery rate.

[0020] The present application uses polytetrafluoroethylene material for the first connecting pipe and the second connecting pipe, which has excellent corrosion resistance and air tightness, avoiding leakage of helium during the recovery process; at the same time, the gravity separation tank is made of stainless steel, and the height size is not less than 5m, which ensures the gas layering effect and the structural stability of the equipment, prolonging the service life.

[0021] Through the synergistic effect of the above technical features, the helium gas escaping in the outer conductor welding process of the radio frequency coaxial cable can be efficiently recovered, a helium gas enrichment flow with high concentration is obtained, and the recovery rate can reach more than 80%. Compared with the existing direct discharge or low-efficiency recovery mode, the helium gas use cost is significantly reduced, the pressure caused by the shortage of helium resources is relieved, the device structure is reasonable, the energy consumption is low, the operation is stable, and a feasible solution is provided for the recycling of rare gases in industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to make the content of the present application more easily understood, the present application will be further described in detail below according to specific embodiments of the present application and in conjunction with the drawings.

[0023] Figure 1 is a structural schematic diagram of the inert gas recovery device during the outer conductor welding of the radio frequency coaxial cable.

[0024] Figure 2 is a top view structural schematic diagram of the inert gas recovery device during the outer conductor welding of the radio frequency coaxial cable arranged in a factory building.

[0025] DESCRIPTION OF DRAWINGS 1, welding area; 2, gas inlet; 3, first connecting pipe; 4, activated carbon sieve layer; 5, exhaust system; 51, pipeline; 6, polyimide separation membrane unit; 70, membrane separation zone; 7, mixed matrix membrane unit; 8, second connecting pipe; 9, gravity separation tank; 10, top outlet; 11, bottom outlet; 12, top helium concentration detection sensor; 13, middle helium concentration detection sensor; 14, bottom helium concentration detection sensor. DETAILED DESCRIPTION

[0026] The present application will be further described below in conjunction with the drawings and specific embodiments, so that those skilled in the art can better understand the present application and implement it, but the embodiments are not as a limitation on the present application.

[0027] In the present application, if the direction (up, down, left, right, front and back) is described, it is only for the convenience of describing the technical scheme of the present application, and is not indicative or suggestive of the technical features indicated must have a specific orientation, be constructed and operated in a specific orientation, therefore, cannot be understood as a limitation on the present application.

[0028] In the present application, the meaning of "several" is one or more, the meaning of "multiple" is two or more, and "greater than", "less than", "more than" and the like are not included in the number; "and above", "and below", "and within" and the like are included in the number. In the description of the present application, if "first", "second" are described, they are only used to distinguish technical features for the purpose, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or implicitly indicating the sequence of indicated technical features.

[0029] In the present application, unless otherwise explicitly limited, the words "set", "install", "connect" and the like should be broadly understood, for example, can be directly connected, can be indirectly connected through an intermediate medium; can be fixedly connected, can be detachably connected, can be integrally formed; can be mechanically connected, can be electrically connected or can communicate with each other; can be the communication or interaction relationship between two elements. The skilled in the art can reasonably determine the specific meaning of the above words in the present application in combination with the specific content of the technical solution.

[0030] Referring to Figure 1 The inert gas recovery device for welding the outer conductor of the radio frequency coaxial cable of the embodiment shown, comprising: At least one welding area 1 for welding operation of the outer conductor of the radio frequency coaxial cable; An air inlet 2 is arranged on the welding area 1 for introducing helium and generating a first tail gas containing helium, air mixed gas and solid impurities during welding; The exhaust system 5 is connected with each of the welding areas 1 through a first connecting pipe 3, and the first connecting pipe 3 is provided with an activated carbon screen layer 4 made of industrial activated carbon; the exhaust system 5 is used for extracting the first tail gas, the activated carbon screen layer 4 removes the water and solid impurities in the first tail gas to obtain a second tail gas, and the exhaust system 5 can pressurize the second tail gas to collect helium and increase the pressure, so that the gas can pass through the membrane layer of the subsequent membrane separation zone 70; The membrane separation zone 70 is arranged downstream of the exhaust system 5 and includes a polyimide separation membrane unit 6 and a mixed matrix membrane unit 7 connected in series; the polyimide separation membrane unit 6 is used to separate the second tail gas to separate the helium and the larger molecular gas containing nitrogen and oxygen in the air in the second tail gas to obtain a first crude helium stream; the mixed matrix membrane unit 7 is used to separate the first crude helium stream to absorb the smaller molecular gas in the first crude helium stream to obtain a second crude helium stream containing helium and impurity gas, and the impurity gas includes argon and air mixed gas; that is, the polyimide separation membrane unit 6 separates the second tail gas into a permeate side stream and a retention side stream, wherein the permeate side obtains a first crude helium stream (He enrichment), and the retention side enriches N2 and O2; the mixed matrix membrane unit 7 continues to separate the first crude helium stream to obtain a second crude helium stream (He further enrichment) on the permeate side. The gravity separation tank 9 is arranged downstream of the membrane separation zone 70 and connected with the membrane separation zone 70 through the second connecting pipe 8, and the top and bottom of the gravity separation tank 9 are respectively provided with a top outlet 10 and a bottom outlet 11; the gravity separation tank 9 is used to introduce the second crude helium stream and separate the helium and the impurity gas based on the density difference of the gas, collect the helium enrichment stream through the top outlet 10, and discharge the heavier impurity gas through the bottom outlet 11. This is because the helium has a lighter density than other rare gases, and after standing in the gravity separation tank 9 for a period of time and cooling, the helium will naturally gather at the top of the gravity separation tank 9, while the heavier gas will settle at the bottom.

[0031] Through the arrangement of the membrane separation zone 70 and the gravity separation tank 9, the preliminary recovery of helium in the RF coaxial cable outer conductor welding tail gas is realized. Through the preliminary efficient enrichment of membrane separation and the low energy consumption purification of gravity separation, the preliminary effective recovery of helium in the RF coaxial cable outer conductor welding tail gas can be realized, and then returned to the factory for further purification. Not only can it significantly reduce the cost of helium consumption, but also helps to cope with the challenge of global helium resource depletion. The device provides a feasible solution for the recovery of rare gases in industrial waste gas, especially for welding processes using helium as a protective gas.

[0032] Optionally, the exhaust system 5 includes a vacuum pump (or piston pump) and a compressor connected in series.

[0033] It should be noted that during the RF coaxial cable outer conductor welding process, argon or argon-helium mixed gas is used as a protective gas to prevent the molten pool from oxidizing and improve the welding quality. The welding process of the present application only uses helium for protection, and the welding equipment is not sealed for the convenience of processing. Since pure helium has higher thermal conductivity than argon, it can improve the arc characteristics and welding performance.

[0034] Furthermore, helium gas is introduced into welding zone 1 through inlet 2. Due to the lack of strict sealing for ease of processing, air impurities are present. A suction system 5 is installed near membrane separation zone 70 to remove the gas. The exhaust gas is introduced into the suction system 5 through the first connecting pipe 3 between welding zone 1 and membrane separation zone 70, effectively capturing any escaping protective gas. An activated carbon sieve layer 4 in the center of the first connecting pipe 3 absorbs moisture and solid impurities from the intake process. Each welding zone 1 is connected to a vacuum pump and a compressor, with the vacuum pump operating at a rate of 40 L / min or higher to ensure helium capture and increase the gas pressure entering membrane separation zone 70. The captured gas then re-enters membrane separation zone 70 through the first connecting pipe 3 to homogenize the gas composition.

[0035] Specifically, the polyimide separation membrane unit 6 includes a polyimide separation membrane, which is a thin film made of a polymer using imide rings and fixed with an iron mesh. The mixed matrix membrane unit 7 includes a mixed matrix membrane, which is a polymer matrix composite membrane using a metal frame.

[0036] It should be noted that the exhaust gas in membrane separation zone 70 is a mixture of helium and air. The separation membrane layer used in membrane separation zone 70 is a selective permeation membrane. Based on the difference in aerodynamic diameter between helium (0.26 nm) and nitrogen (0.364 nm), this embodiment selects a polyimide separation membrane and a mixed matrix membrane, which have high permeability and selectivity for helium. Most polymer membranes have selective permeability to helium. The structure of membrane separation zone 70 is designed as a multi-stage series to separate various gases and gradually increase the helium concentration. The first-stage polyimide separation membrane mainly separates most of the helium and larger molecular gases such as nitrogen and oxygen from the air, obtaining a coarse helium stream. The second stage uses a mixed matrix membrane to absorb smaller molecular gases in the coarse helium stream.

[0037] Optionally, the first connecting pipe 3 and / or the second connecting pipe 8 are made of polytetrafluoroethylene (PTFE); PTFE has good airtightness and high corrosion resistance. The diameter of the first connecting pipe 3 and / or the second connecting pipe 8 is 1m ± 0.1m.

[0038] In one embodiment, the gravity separation tank 9 is made of stainless steel and is completely sealed; the height of the gravity separation tank 9 is not less than 5m to promote stratification; based on the plant design, the radial dimension of the gravity separation tank 9 is within 4m. Multiple gravity separation tanks 9 can be installed as needed.

[0039] Reference Figure 2 The diagram shown is a top view of the factory layout in one embodiment. Multiple welding areas 1 are provided. Each welding area 1 is connected to the extraction system 5 through a first connecting pipe 3, and is connected to a single membrane separation zone 70 through a pipe 51 of the extraction system 5. The single membrane separation zone 70 is connected to multiple gravity separation tanks 9.

[0040] Specifically, the gravity separation tank 9 is provided with a top helium concentration detection sensor 12, a middle helium concentration detection sensor 13 and a bottom helium concentration detection sensor 14 corresponding to the top, middle and bottom of the gravity separation tank 9 respectively. The helium concentration detection sensor based on MEMS is not affected by air pressure and temperature, and can accurately detect the concentration of helium in different regions of the gravity separation tank 9.

[0041] Specifically, the top outlet 10 and the bottom outlet 11 are provided with a top valve and a bottom valve respectively. The top valve and the bottom valve are respectively connected with a top air extraction pump and a bottom air extraction pump.

[0042] It should be noted that after passing through the membrane separation zone 70, the helium stream enters the gravity separation tank 9 through the second connecting pipe 8 of the membrane separation zone 70 and the gravity separation zone. The gravity separation is a method of separating by using the density difference of gas. The density of helium is about 0.1786 g / L, the density of argon is about 1.784 g / L, and the density of air is about 1.225 g / L. Helium will float upwards under static conditions.

[0043] The embodiment also provides a recovery method of inert protective gas during welding of an outer conductor of a radio frequency coaxial cable, based on the recovery device of inert protective gas during welding of the outer conductor of the radio frequency coaxial cable. The recovery method comprises the following steps: S1, using helium as protective gas for welding operation in at least one welding area 1, introducing helium through the gas inlet 2, and generating first tail gas containing helium, air mixed gas and solid impurities during the welding process; S2, the first tail gas passes through the activated carbon sieve layer 4 arranged in the first connecting pipe 3, removes the water and solid impurities in the first tail gas, obtains second tail gas, and pressurizes the second tail gas through the compressor of the exhaust system 5; S3, the second tail gas is introduced into the membrane separation zone 70, and is sequentially separated by a polyimide separation membrane and a mixed matrix membrane for multi-stage separation. The polyimide separation membrane unit 6 separates larger molecular gases containing nitrogen and oxygen in the second tail gas to obtain a first crude helium stream. The mixed matrix membrane unit 7 further separates smaller molecular gases in the first crude helium stream to obtain a second crude helium stream containing helium and impurity gas; S4, the second crude helium stream is introduced into the gravity separation tank 9 through the second connecting pipe 8, the top valve and the bottom valve are controlled to be in a closed state, and the density difference between helium and impurity gas is utilized to realize stratification under static conditions, so that the helium in the second crude helium stream floats and gathers to the top of the gravity separation tank 9, and the impurity gas settles to the bottom of the gravity separation tank 9; Meanwhile, the top helium concentration detection sensor 12, the middle helium concentration detection sensor 13 and the bottom helium concentration detection sensor 14 monitor the helium concentration in real time; S5, since the sensor readings fluctuate during the gravity settling process, the middle helium concentration detection sensor 13 monitors the position of the helium layer (the detection accuracy can be increased by setting the scale of the number of sensors). In response to the helium concentration values detected by the top helium concentration detection sensor 12 and the middle helium concentration detection sensor 13 reaching more than 80% and the value fluctuation being within ±5%, and the helium concentration value detected by the bottom helium concentration detection sensor 14 being less than the preset first helium concentration threshold value (the first helium concentration threshold value is smaller, indicating that the bottom of the gravity separation tank 9 does not contain a higher concentration of helium, which can be set according to needs, indicating that the upper layer has separated a large amount of helium and other gas impurities); control the opening of the bottom valve, and extract the impurity gas settled at the bottom of the gravity separation tank 9 by the bottom gas pump at a flow rate of 1.6±0.1L / min; S6, in response to the helium concentration value detected by the bottom helium concentration detection sensor 14 being higher than the preset second helium concentration threshold value (the second helium concentration threshold value can be set according to needs, indicating that the concentration at the bottom of the gravity separation tank 9 begins to rise significantly), control the closing of the bottom valve and the opening of the top valve; S7, collect the helium-rich stream from the top outlet 10 by the top gas pump, and in response to the helium concentration value detected by the top helium concentration detection sensor 12 decreasing to less than 70%, control the top gas pump to stop extracting, and the collected helium-rich stream is subjected to subsequent purification.

[0044] By combining membrane separation technology with gravity separation technology, the preliminary recovery of helium in the welding tail gas of the outer conductor of the radio frequency coaxial cable is realized. According to estimates, the recovery rate can reach more than 80% under the two-layer membrane separation and gravity separation steps.

[0045] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to examples, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. Apparatus for recovering inert shielding gas during welding of the outer conductor of a radio frequency coaxial cable, characterized in that, The application relates to a helium recovery device for radio frequency coaxial cable outer conductor welding. The helium recovery device comprises: at least one welding area (1) for radio frequency coaxial cable outer conductor welding operation; an air inlet (2) arranged on the welding area (1) for introducing helium and generating a first tail gas containing helium, air mixed gas and solid impurities during welding; an exhaust system (5) connected with each welding area (1) through a first connecting pipe (3), wherein an active carbon sieve layer (4) is arranged in the first connecting pipe (3), the exhaust system (5) is used for extracting the first tail gas, the first tail gas passes through the active carbon sieve layer (4) to remove water and solid impurities, thereby obtaining second tail gas, and the exhaust system (5) can pressurize the second tail gas; a membrane separation zone (70) arranged downstream of the exhaust system (5) and comprising a polyimide separation membrane unit (6) and a mixed matrix membrane unit (7) connected in series; the polyimide separation membrane unit (6) is used for separating the second tail gas to separate larger molecular gas containing nitrogen and oxygen in the second tail gas, thereby obtaining a first crude helium stream; the mixed matrix membrane unit (7) is used for separating the first crude helium stream to absorb smaller molecular gas in the first crude helium stream, thereby obtaining a second crude helium stream containing helium and impurity gas, wherein the impurity gas comprises argon and air mixed gas; 2. The radio frequency coaxial cable outer conductor welding time inert gas recovery apparatus according to claim 1, wherein, a gravity separation tank (9) arranged downstream of the membrane separation zone (70) and connected with the membrane separation zone (70) through a second connecting pipe (8), wherein a top outlet (10) and a bottom outlet (11) are arranged at the top and the bottom of the gravity separation tank (9) respectively, and the gravity separation tank (9) is used for introducing the second crude helium stream and separating helium and impurity gas based on the density difference of the gas, thereby collecting a helium rich stream through the top outlet (10) and discharging the impurity gas through the bottom outlet (11).

3. The radio frequency coaxial cable outer conductor welding time inert gas recovery apparatus of claim 1, wherein, The exhaust system (5) comprises a vacuum pump and a compressor connected in series.

4. The radio frequency coaxial cable outer conductor welding time inert gas recovery apparatus of claim 1, wherein, The material of the first connecting pipe (3) and / or the second connecting pipe (8) is polytetrafluoroethylene.

5. The radio frequency coaxial cable outer conductor welding time inert gas recovery apparatus of claim 1, wherein, The diameter of the first connecting pipe (3) and / or the second connecting pipe (8) is 1m+ / -0.1m.

6. The radio frequency coaxial cable outer conductor welding time inert gas recovery apparatus of claim 1, wherein, The height of the gravity separation tank (9) is not less than 5m, and the radial dimension is within 4m.

7. The radio frequency coaxial cable outer conductor welding time inert gas recovery apparatus of claim 1, wherein, The material of the gravity separation tank (9) is stainless steel.

8. The radio frequency coaxial cable outer conductor welding time inert gas recovery apparatus of claim 1, wherein, The gravity separation tank (9) is provided with a top helium concentration detection sensor (12), a middle helium concentration detection sensor (13) and a bottom helium concentration detection sensor (14) arranged correspondingly near the top, the middle and the bottom of the gravity separation tank (9) respectively.

9. The radio frequency coaxial cable outer conductor welding time inert gas recovery apparatus of claim 8, wherein, A top valve and a bottom valve are arranged correspondingly at the top outlet (10) and the bottom outlet (11).

10. A method for recovering an inert protective gas during welding of an outer conductor of a radio frequency coaxial cable, characterized in that, The top valve and the bottom valve are respectively connected with a top air pump and a bottom air pump. The helium recovery device for radio frequency coaxial cable outer conductor welding according to any one of claims 1-9, and a recovery method thereof, S1, welding is performed in at least one welding area (1) using helium as a shielding gas, while helium is introduced through the gas inlet (2), and a first tail gas containing helium, air mixed gas and solid impurities is generated during the welding process; S2, the first tail gas is extracted by the vacuum pump of the exhaust system (5), and the water and solid impurities in the first tail gas are removed by passing through the activated carbon sieve layer (4) arranged in the first connecting pipe (3), to obtain a second tail gas, and the second tail gas is pressurized by the compressor of the exhaust system (5); S3, the second tail gas is introduced into the membrane separation zone (70) and subjected to multi-stage separation by passing through the polyimide separation membrane and the mixed matrix membrane in sequence, the polyimide separation membrane unit (6) separates the larger molecular gas containing nitrogen and oxygen in the second tail gas to obtain a first crude helium stream, and the mixed matrix membrane unit (7) further separates the smaller molecular gas in the first crude helium stream to obtain a second crude helium stream containing helium and impurity gas; S4, the second crude helium stream is introduced into the gravity separation tank (9) through the second connecting pipe (8), the top valve and the bottom valve are controlled to be closed, and the density difference between helium and impurity gas is utilized to realize stratification under the condition of static state, so that the helium in the second crude helium stream floats and gathers to the top of the gravity separation tank (9), and the impurity gas settles to the bottom of the gravity separation tank (9); At the same time, the top helium concentration detection sensor (12), the middle helium concentration detection sensor (13) and the bottom helium concentration detection sensor (14) monitor the helium concentration in real time; S5, in response to the fact that the helium concentration values detected by the top helium concentration detection sensor (12) and the middle helium concentration detection sensor (13) are more than 80% and the numerical fluctuation is within ±5%, and the helium concentration value detected by the bottom helium concentration detection sensor (14) is less than the preset first helium concentration threshold value; control to open the bottom valve, and extract the impurity gas settled to the bottom of the gravity separation tank (9) through the bottom air pump at a flow rate of 1.6±0.1L / min; S6, in response to the fact that the helium concentration value detected by the bottom helium concentration detection sensor (14) is higher than the preset second helium concentration threshold value, control to close the bottom valve and open the top valve; S7, collect the helium enrichment stream from the top outlet (10) through the top air pump, and in response to the fact that the helium concentration value detected by the top helium concentration detection sensor (12) decreases to less than 70%, control the top air pump to stop extraction, and collect the helium enrichment stream for subsequent purification.

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