Airtight pipeline gas extraction device and gas extraction method thereof

Abstract

The application discloses a kind of closed pipeline gas taking device and its gas taking method, solve the existing closed pipeline gas sampling is loss sampling, sampling quantity is larger, can destroy the internal atmosphere of part and cause the problem of part waste.This application includes sealing structure, the sealing structure is respectively connected with sampling assembly and punch welding sealing assembly, closed pipeline is inserted into the sealing structure, the sealing structure includes seal and sealing plug, the sealing plug, seal and the tube wall of closed pipeline are collectively enclosed to form sealed cavity, the sampling assembly includes gas taking bottle and vacuum pump, the gas taking bottle and the vacuum pump are connected with the sealing plug and are communicated with the sealed cavity, the punch welding sealing assembly includes laser device, the sealing plug is provided with light transmission plate, and the laser device is punched and welded through light transmission plate.This application has the advantages of nondestructive and micro sampling, does not affect the internal gas content and atmosphere of closed pipeline and small volume.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sampling detection, in particular to a closed pipeline gas taking device and a gas taking method thereof. BACKGROUND

[0002] China has been an industrialized country for several decades. For some parts with pipeline sealed cavities that have been working for several years, the internal gas state must be detected to determine the use state of the parts.

[0003] The traditional method is to use a destructive detection method to obtain the internal gas state of the part pipeline. After destructive detection, the product cannot be used. When facing a large number of products that need to be detected, a sampling method is usually used to take out a part of the internal gas by a destructive method. After detecting the gas components, the use state of other products is determined by statistical methods. This traditional destructive detection method has the following disadvantages: first, it is a lossy detection, causing waste of parts; second, the sampling detection method is not completely accurate for judging the use state of the undetected parts; third, it stops the pipeline from working, affecting the normal progress of experimental production; fourth, for closed containers with pipelines, the traditional method takes samples destructively, and the sampling will inevitably destroy the internal atmosphere state of the container.

[0004] Therefore, it is necessary to develop a sampling detection device that realizes non-destructive detection in a closed environment. SUMMARY

[0005] The technical problem to be solved by the present application is that the existing closed pipeline gas sampling detection is in a lossy form, which destroys the internal atmosphere state of the pipeline, has a large sampling amount, affects the internal gas content of the closed pipeline, and causes waste of parts and affects the normal progress of production and research and development due to lossy sampling.

[0006] The present application provides a closed pipeline gas taking device and a gas taking method thereof to solve the above problems.

[0007] The present application is achieved by the following technical solutions:

[0008] The application discloses a kind of closed pipeline gas taking device, including sealing structure, sampling assembly and punch welding assembly, the sealing structure is connected with the sampling assembly and punch welding assembly respectively, closed pipeline is inserted into the sealing structure, the sealing structure includes sealing piece and sealing plug, the sealing plug, the sealing piece and the pipe wall of the closed pipeline are collectively enclosed to form sealed cavity, the sampling assembly includes gas taking bottle and vacuum pump, the gas taking bottle and the vacuum pump are connected with the sealing plug, the gas taking bottle is communicated with the sealed cavity, the vacuum pump is communicated with the sealed cavity, for the sealed cavity is pumped, the punch welding assembly includes laser device, the sealing plug is provided with light transmission plate, the laser device is punched and welded by the light transmission plate to the closed pipeline in the sealed cavity.

[0009] The design principle of the application is that in many production or research and development environments, the closed pipeline works continuously, and problems of the closed pipeline parts are prone to occur over time, so internal gas detection is needed to reflect the working state of the closed pipeline, and the key of gas detection is how to take gas samples from the closed pipeline without affecting the normal use of the closed pipeline.The sealing plug, the sealing piece and the pipe wall of the closed pipeline are collectively enclosed to form a sealed cavity, a vacuum pump is used to pump a vacuum, a negative pressure environment is formed in the sealed cavity, and laser punching sampling is carried out in the sealed cavity.The vacuum negative pressure environment can make the gas in the closed pipeline flow out smoothly, and after sampling is completed, the pipe wall of the closed pipeline is welded by laser.Because laser can penetrate the light transmission plate to punch and weld the pipe wall of the closed pipeline, mechanical damage to the sealed environment of the sealed cavity will not occur, and the entire sealed cavity can be kept completely sealed and isolated from the atmosphere during the entire sampling and welding process, so it will not be affected by the gas in the external environment.Because the laser punching can control the size of the hole to be very small, the laser device is located outside the sealed cavity for processing, and the sealing structure connected with the closed pipeline and the sealed cavity can also be made very small, so the amount of sampling can also be very small, which can be less than 10ml, and will not affect the gas content in the closed pipeline.

[0010] Preferably, the sealing piece includes a screw sleeve and a tapered sleeve, the screw sleeve is connected with the tapered sleeve, the closed pipeline is inserted into the tapered sleeve, the screw sleeve is detachably connected with the sealing plug, and the tapered sleeve, the sealing plug and the pipe wall of the closed pipeline collectively enclose the sealed cavity.

[0011] In the specific sealing process, the end of the closed pipeline to be detected is inserted into the taper sleeve, the screw sleeve is sleeved on the taper sleeve to form one end of the sealing element, the sliding screw sleeve and the taper sleeve can adjust the position of the sealing element on the closed pipeline, when the position to be detected is adjusted, the sealing plug is connected with the screw sleeve, and the sealing plug and the taper sleeve form the other end of the sealing element to form a sealing cavity for sealing the closed pipeline.

[0012] Preferably, the taper sleeve comprises a taper end, and the outer diameter of the taper end gradually decreases from the end connected with the screw sleeve to the end connected with the sealing plug.

[0013] Further, the inner cavity diameter of the sealing plug is greater than the closed pipeline.

[0014] In the specific sealing operation, the outer wall of the sealing plug is threadedly connected with the screw sleeve, and the inner wall of the sealing plug is gradually screwed into the taper end of the taper sleeve until the taper sleeve is completely sealed with the closed pipeline, and the gap between the sealing plug and the closed pipeline becomes a flow channel for the gas.

[0015] Preferably, the perforating and welding assembly comprises a laser and a laser processing head, the laser is connected with the laser processing head, and the laser emitted from the laser processing head can perforate and weld the position to be detected of the closed pipeline through the light-transmitting plate.

[0016] The light-transmitting plate can transmit the laser to perforate and weld the wall of the closed pipeline, and ensure the sealing of the sealing cavity during the whole process.

[0017] Preferably, the sealing plug is provided with a pressure detection table for detecting the pressure in the sealing cavity, so as to control the sampling amount.

[0018] Preferably, the gas sampling bottle is connected with the sealing plug through a gas pipe one, and the gas pipe one is provided with an electromagnetic valve one.

[0019] Preferably, the vacuum pump is connected with the sealing plug through a gas pipe two, and the gas pipe two is provided with an electromagnetic valve two.

[0020] Further, the electromagnetic valve one is an electromagnetic valve one, and the electromagnetic valve two is an electromagnetic valve two.

[0021] After the sealing operation is completed, the gas in the sealing cavity is air, which will affect the sampled gas sample and cause inaccurate detection results if not removed completely. The vacuum pump and the gas sampling bottle can be opened and closed, the electromagnetic valve one and the electromagnetic valve two are controlled in sequence, and the laser perforation and welding are used to realize sampling and repair of the closed pipeline.

[0022] Preferably, the laser is a quasi-continuous single-mode fiber laser.

[0023] A closed pipeline gas sampling method using the closed pipeline gas sampling device, comprising the following steps:

[0024] Step 1: unscrew the sealing plug from the screw sleeve until the taper sleeve can move freely between the sealing plug and the screw sleeve;

[0025] Step 2: insert the closed pipeline into the screw sleeve and the taper sleeve, select the position to be measured of the closed pipeline, fix the relative position between the closed pipeline and the screw sleeve, screw the sealing plug into the screw sleeve until the taper sleeve and the outer wall of the closed pipeline are sealed;

[0026] Step 3: open electromagnetic valve one and electromagnetic valve two, start the vacuum pump, when the pressure gauge shows zero, close electromagnetic valve one, close electromagnetic valve two, and close the vacuum pump;

[0027] Step 4: turn on the laser, adjust the beam parameters, start laser drilling, and at the same time, open electromagnetic valve one to start collecting the atmosphere inside the closed pipeline. During the sampling process, as the gas flows from the closed pipeline to the sealing plug, the pressure in the sealing cavity gradually increases until it is equal to the pressure in the sealing plug, and the sampling is completed.

[0028] Step 5: after the gas collection is completed, close electromagnetic valve one, turn on the laser welding mode, and weld the hole of the closed pipeline.

[0029] Preferably, in the closed pipeline gas sampling method, the size of the hole drilled in step 4 is 0.1-0.5mm in diameter.

[0030] Preferably, in the closed pipeline gas sampling method, in step 4, when adjusting the laser beam parameters, the laser beam is set to a laser beam pulse mode, and the focal length of the lens in the laser processing head is set to 70-120mm.

[0031] Preferably, in the closed pipeline gas sampling method, in step 5, the welding mode of the laser is turned on by switching the laser beam to a continuous laser beam mode, and the laser processing head is moved away from the closed pipeline by a certain distance to achieve negative defocusing.

[0032] The application switches to a laser beam pulse mode when punching the closed pipeline, the laser beam has very high pulse energy, and the material at the punching position can be evaporated, and when welding, the laser beam is switched to a continuous laser beam mode, the material around the small hole is melted and flows to the small hole, and the welding action is completed, since the same laser beam is used for punching and welding, the laser beam does not move, and when the diameter of the hole is very small, the position of the small hole can be accurately determined for welding, the welding quality of the closed pipeline is guaranteed, and since the punching and welding are completed on the same laser, the size of the device is reduced and the cost is saved, and the sampling operation efficiency is also higher.

[0033] The application has the following advantages and beneficial effects:

[0034] 1、The application uses laser to punch from the outside of the sealed cavity, ensures the sealing of the sealed cavity during the whole sampling process, removes air in the sealed cavity by vacuumizing, so that the whole process is carried out in an environment isolated from the outside world, the gas in the product is not polluted, and after sampling is completed, laser is used for welding, the welded pipeline meets the technical use requirements, and does not affect the normal use of the closed pipeline.

[0035] 2、The application uses laser to punch from the outside, compared with the mechanical punching mode, the size of the device and the volume of the sealed cavity can be reduced, and by controlling the laser beam, the size of the hole punched is very small, specifically 0.1-0.5mm, so that the gas taken out from the closed pipeline is very small, specifically less than 10ml, which does not affect the gas content in the closed pipeline and does not affect the normal use of the closed pipeline.

[0036] 3、The laser used in the application is a quasi-continuous single-mode fiber laser, which has the characteristics of small size and high portability, and by adjusting the laser parameters, the same laser is used for laser punching and laser welding, which completes the task target while having the characteristics of low cost and small size, and since the laser beam does not move, the position of the small hole can be accurately determined for welding when the diameter of the hole is very small.

[0037] 4、The application adopts a taper sleeve locking type seal when sealing with the outer wall of the pipeline, which is simple to operate and has good sealing effect.

[0038] 5、The device has a small overall size, can be fixed for detection, can also be switched to a wheel state to move the detected parts, and the gas taking part and the laser part can be separated, which is more flexible in application in various scenes.

[0039] 6、The laser processing head is attached with a coaxial CCD, which can observe the state of the small hole and the welding condition in real time. BRIEF DESCRIPTION OF DRAWINGS

[0040] The drawings described herein are intended to provide further understanding of the embodiments of the present application, form a part of the present application, and do not constitute a limitation of the embodiments of the present application. In the drawings:

[0041] Figure 1 A schematic diagram of a perspective structure of the present application.

[0042] Figure 2 A schematic diagram of a sectional structure of the present application.

[0043] Figure 3 A schematic diagram of a perspective structure of the present application in working state.

[0044] Markings in the drawings and corresponding names of parts:

[0045] 1 - closed conduit, 2 - screw sleeve, 3 - taper sleeve, 4 - sealing plug, 5 - light transmission plate, 6 - small hole position, 7 - laser beam, 8 - electromagnetic valve 2, 9 - vacuum pump, 10 - electromagnetic valve 1, 11 - gas taking bottle, 12 - pressure detection meter, 13 - sealing cavity, 14 - mechanical platform, 15 - laser, 16 - mounting plate, 17 - product to be inspected, 18 - laser processing head, 19 - trace gas sampling device, 20 - supporting leg. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with embodiments and drawings, the illustrative embodiments of the present application and the description thereof are only used to explain the present application, and do not constitute a limitation of the present application.

[0047] In the present application, the structural part of removing the laser and the vacuum pump is named as: trace gas sampling device.

[0048] Example 1

[0049] As Figure 1 and Figure 2As shown, a closed pipeline gas sampling device comprises a sealing structure, a sampling assembly and a punching and welding assembly. The sealing structure comprises a sealing member and a sealing plug 4. The sealing member comprises a screw sleeve 2 and a tapered sleeve 3. The screw sleeve 2 is connected with the tapered sleeve 3. The closed pipeline 1 penetrates into the tapered sleeve 3. The tapered sleeve 3, the sealing plug 4 and the pipe wall of the closed pipeline 1 jointly enclose the sealing cavity 13. The tapered sleeve 3 comprises a tapered end. The outer diameter of the tapered end gradually decreases from one end connected with the screw sleeve 2 to the other end connected with the sealing plug 4. The inner cavity diameter of the sealing plug 4 is greater than the closed pipeline 1. In particular, during sealing operation, the to-be-measured end of the closed pipeline 1 is inserted into the tapered sleeve 3. The screw sleeve 2 is sleeved on the tapered sleeve 3 to form one end of the sealing member. The screw sleeve 2 and the tapered sleeve 3 can adjust the position of the sealing member on the closed pipeline 1. When the to-be-measured position is adjusted, the sealing plug 4 is connected with the screw sleeve 2. The sealing plug 4, as the other end of the sealing member, together with the tapered sleeve 3, forms the sealing cavity 13 for sealing the closed pipeline 1. The outer wall of the sealing plug 4 is threadedly connected with the screw sleeve 2. The inner wall of the sealing plug 4 gradually rotates into the tapered end of the tapered sleeve 3 until the tapered sleeve 3 is completely sealed with the closed pipeline 1. The gap between the sealing plug 4 and the closed pipeline 1 becomes the flow channel of the gas.

[0050] The sampling assembly comprises a gas sampling bottle 11 and a vacuum pump 9. The gas sampling bottle 11 is connected with the sealing plug 4 through a gas pipe 1. An electromagnetic valve 1 0 is arranged on the gas pipe 1. The electromagnetic valve 1 0 controls the communication and disconnection between the gas sampling bottle 1 1 and the sealing cavity 13. The vacuum pump 9 is connected with the sealing plug 4 through a gas pipe 2. An electromagnetic valve 2 8 is arranged on the gas pipe 2. The electromagnetic valve 2 8 controls the communication and disconnection between the vacuum pump 9 and the sealing cavity 13. When the electromagnetic valve 2 8 is opened, the vacuum pump 9 can perform vacuum pumping on the sealing cavity 13 to form a negative pressure environment. The air is completely pumped away to prevent the extracted gas from being polluted and affecting the detection result.

[0051] The sealing plug 4 is provided with a light transmission plate 5. The light transmission plate 5 is a light transmission glass. The laser device punches and welds the closed pipeline 1 in the sealing cavity 13 through the light transmission plate 5.

[0052] The sealing plug 4 is provided with a pressure detection table 12 for detecting the air pressure in the sealing cavity 13. The pressure detection table 12 is used to judge whether the air is completely pumped away and whether the required negative pressure environment is formed, so as to control the sampling amount and ensure that the extracted gas is not polluted by air.

[0053] The punching and welding assembly comprises a laser 1 5 and a laser processing head 1 8. The laser 1 5 is connected with the laser processing head 1 8. The laser beam 7 emitted from the laser processing head 1 8 penetrates through the light transmission plate 5 to punch and weld the to-be-measured part of the closed pipeline 1.

[0054] The light-transmitting plate 5 allows the laser to pass through, thereby achieving the punching and welding of the pipe wall of the sealed pipe 1 and ensuring the sealing of the sealing cavity 13 during the entire process.

[0055] After the sealing operation is completed, the gas in the sealing chamber 13 is air. If it is not removed cleanly, it will affect the gas sample taken out, resulting in inaccurate detection results. The present invention realizes sampling and repair of the sealed pipeline 1 by setting a vacuum pump 9 and a gas bottle 11 that can be opened and closed, controlling the sequence of the electromagnetic valve 10 and the electromagnetic valve 2 8, and performing laser drilling and welding.

[0056] Example 2

[0057] The difference between this embodiment and embodiment 1 is that the laser 15 is a quasi-continuous single-mode fiber laser 15 , and the laser drilling and laser welding use the same laser 15 .

[0058] Example 3

[0059] like Figure 3 As shown, the difference between this embodiment and embodiment 2 is that the trace atmosphere sampling device 19 is mounted on the mounting plate 16 through the support legs 20, the laser processing head 18 is also mounted on the mounting plate 16, the laser 15 and the vacuum pump 9 are mounted in the mechanical platform 14, the mounting plate 16 is connected to the top of the mechanical platform 14, and a roller is installed at the bottom of the mechanical platform 14.

[0060] The support leg 20 is a retractable structure, and the height of the trace atmosphere sampling device 19 can be adjusted according to the height of the product to be inspected 17.

[0061] During the specific operation, the product to be inspected 17 is placed on the mounting plate 16 and fixed. The product to be inspected 17 is moved so that the sealed pipe 1 penetrates the interior of the sealing structure. Once it reaches the predetermined position, the threaded sleeve 2 and the sealing plug 4 are tightened to form the sealed chamber 13. The electromagnetic valve 10 and the electromagnetic valve 2 8 are opened, and the vacuum pump 9 is turned on. When the pressure gauge 12 reads the predetermined pressure value, the electromagnetic valve 10 and the electromagnetic valve 2 8 are closed, and the vacuum pump 9 is turned off. At this point, the sealed chamber 13 is vacuumed. The laser 15 is turned on and adjusted to the predetermined parameters. The beam parameters are adjusted and laser drilling begins, controlling the diameter of the small hole within the range of 0.1-0.5 mm. At the same time, the electromagnetic valve 10 is opened. At this time, the gas inside the sealed pipe 1 escapes from the pipe due to the internal and external pressure difference and enters the gas extraction bottle 11. After the pressure gauge 12 reading stabilizes, the atmosphere is collected, the electromagnetic valve is closed, and the laser 15 is turned on to weld and seal the gas extraction hole. The gas extraction device is then removed, and the inspection process is complete.

[0062] Example 4

[0063] A method for taking gas from a closed pipe using the closed pipe gas taking device of embodiment 2, comprising the following steps:

[0064] Step 1: unscrew the sealing plug 4 from the screw sleeve 2 until the taper sleeve 3 can move freely between the sealing plug 4 and the screw sleeve 2;

[0065] Step 2: insert the closed pipe 1 into the screw sleeve 2 and the taper sleeve 3, after selecting the position to be measured of the closed pipe 1, fix the relative position between the closed pipe 1 and the screw sleeve 2, screw the sealing plug 4 into the screw sleeve 2 until the taper sleeve 3 and the outer wall of the closed pipe 1 are sealed;

[0066] Step 3: open the electromagnetic valve 1 10 and the electromagnetic valve 2 8, start the vacuum pump 9, when the pressure gauge 12 shows zero, close the electromagnetic valve 1 10, close the electromagnetic valve 2 8, and close the vacuum pump 9;

[0067] Step 4: start the laser 15, adjust the beam parameters, set the laser beam to pulse mode, set the focal length of the lens in the laser processing head to 70-120mm, specifically 80mm, start the laser drilling, at the same time, open the electromagnetic valve 1 10, the gas in the closed pipe 1 flows to the sealing cavity 13 through the hole position 6, and the gas collection in the closed pipe 1 starts. During the sampling process, as the gas flows from the closed pipe 1 to the sealing plug 4, the pressure in the sealing cavity 13 gradually increases until it is equal to the pressure in the closed pipe 1, and the sampling is completed.

[0068] Step 5: after the gas collection is completed, close the electromagnetic valve 1 10, start the laser 15 in welding mode, switch the laser beam to continuous mode, move the laser processing head away from the closed pipe to achieve negative defocusing, switch the laser beam to continuous mode, move the laser processing head away from the closed pipe to achieve negative defocusing, and weld the hole of the closed pipe 1.

[0069] The size of the hole drilled in step 4 is 0.1-0.5mm in diameter.

[0070] In the present application, "up", "down", "top" and "bottom" are based on the orientation shown in the drawings.

[0071] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application, and it should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A closed pipeline gas extraction device, characterized in that: It includes a sealing structure, a sampling component and a punching welding sealing component, wherein the sealing structure is connected to the sampling component and the punching welding sealing component respectively. The sealed pipe (1) penetrates the sealing structure, and the sealing structure includes a sealing member and a sealing plug (4). The sealing plug (4), the sealing member, and the wall of the sealed pipe (1) together enclose a sealed cavity (13). The sampling assembly comprises a gas bottle (11) and a vacuum pump (9), wherein the gas bottle (11) and the vacuum pump (9) are both connected to the sealing plug (4), the gas bottle (11) is in communication with the sealing cavity (13), and the vacuum pump (9) is in communication with the sealing cavity (13) for evacuating the sealing cavity (13). The punching and welding assembly comprises a laser device, a light-transmitting plate (5) is provided on the sealing plug (4), and the laser device punches and welds the sealed pipe (1) located in the sealing cavity (13) through the light-transmitting plate (5); a pressure detection gauge (12) is provided on the sealing plug (4) for detecting the pressure in the sealing cavity (13); The punching and welding sealing assembly comprises a laser (15) and a laser processing head (18), wherein the laser (15) and the laser processing head (18) are connected, and the laser processing head (18) punches and welds the portion to be tested of the sealed pipe (1) through the light-transmitting plate (5); The sealing member comprises a screw sleeve (2) and a cone sleeve (3), wherein the screw sleeve (2) is connected to the cone sleeve (3), the sealed pipe (1) is inserted into the cone sleeve (3), the screw sleeve (2) is detachably connected to the sealing plug (4), the cone sleeve (3), the sealing plug (4) and the pipe wall of the sealed pipe (1) together enclose the sealing cavity (13), and the cone sleeve (3) comprises a cone end, the outer diameter of which gradually decreases from an end connected to the screw sleeve (2) to an end connected to the sealing plug (4).

2. A closed pipeline gas extraction device according to claim 1, characterized in that: The gas extraction bottle (11) and the sealing plug (4) are connected via a first air pipe, on which a first electromagnetic valve (10) is provided. The vacuum pump (9) and the sealing plug (4) are connected via a second air pipe, on which a second electromagnetic valve (8) is provided.

3. A closed pipeline gas extraction method, characterized in that: The method of using the closed pipeline (1) gas extraction device as claimed in claim 1 or 2 comprises the following steps: Step 1: Unscrew the sealing plug (4) from the threaded sleeve (2) until the cone sleeve (3) can move freely between the sealing plug (4) and the threaded sleeve (2); Step 2: insert the sealed pipe (1) into the screw sleeve (2) and the cone sleeve (3), select the position of the sealed pipe (1) to be tested, fix the relative position between the sealed pipe (1) and the screw sleeve (2), and screw the sealing plug (4) into the screw sleeve (2) until the cone sleeve (3) and the outer wall of the sealed pipe (1) are sealed; Step 3: Open electromagnetic valve 1 (10) and electromagnetic valve 2 (8), start the vacuum pump (9), and when the pressure gauge shows zero, close electromagnetic valve 1 (10), close electromagnetic valve 2 (8), and turn off the vacuum pump (9); Step 4: Turn on the laser (15), adjust the laser beam parameters, start laser drilling, and simultaneously turn on the electromagnetic valve (10) to start sampling the atmosphere inside the sealed pipe (1). During the sampling process, as the gas flows from the sealed pipe (1) to the sealing plug (4), the gas pressure in the sealed cavity (13) gradually increases until the two are equal, and the sampling is completed; Step 5: After completing the gas collection, close the electromagnetic valve 1 (10), turn on the welding mode of the laser (15), and weld and seal the hole of the sealed pipe (1).

4. A closed pipeline gas extraction method according to claim 3, characterized in that: The size of the holes punched in step 4 is: 0.1-0.5 mm in diameter.

5. A closed pipeline gas extraction method according to claim 3 or 4, characterized in that: In step 4, when adjusting the laser beam parameters, the laser beam is set to a laser beam pulse mode, and the focal length of the lens in the laser processing head (18) is set to 70-120 mm.

6. A closed pipeline gas extraction method according to claim 3 or 4, characterized in that: In step 5, the specific method for starting the welding sealing mode of the laser (15) is as follows: the laser beam is switched to a continuous laser beam mode, and the laser processing head (18) is moved away from the sealed pipe (1) by a certain distance to achieve negative defocus.

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