Multi-channel time division multiplexing sampling system and method for tracer gas leakage detection

Abstract

The invention belongs to the technical field of tracer gas leakage detection, and relates to a multichannel time division multiplexing sampling system and method for tracer gas leakage detection. The system comprises a sampling circulation loop, an external sampling cavity and a sampling self-cleaning device, the sampling circulation loop comprises a gas return branch and a plurality of sampling points, and each sampling point is correspondingly connected with one gas inlet electromagnetic valve to form multi-channel sampling; a first air return electromagnetic valve is arranged on the air return branch; a self-sealing sampling opening is formed in the external sampling cavity, and a sampling pump and an air pressure sensor are arranged in the external sampling cavity; the sampling pump is communicated with the air inlet electromagnetic valve; the sampling self-purification device comprises an air extracting pump, an air extracting electromagnetic valve, an air exhausting electromagnetic valve and a second air returning electromagnetic valve; one end of the first air return electromagnetic valve is connected with the air return port, and the other end of the first air return electromagnetic valve is communicated with the external sampling cavity; one end of the second air return electromagnetic valve is connected with the sucking pump, and the other end is connected with the air return port. The problem that an existing leak detection method has safety risks or is low in accuracy is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of tracer gas leak detection, and particularly relates to a multi-channel time-division multiplexing sampling system and method for tracer gas leak detection. Background Art

[0002] Gas-insulated switchgear relies on gases such as SF6 as insulation and arc-extinguishing media, and good sealing performance is the key to ensuring the normal operation of the equipment. In a high-temperature environment, the materials of the equipment may expand, and the sealing components may deform, resulting in a decline in sealing performance; while in a low-temperature environment, the materials may contract, and the same may cause gaps or leaks at the seals. By conducting sealing tests under high and low temperature conditions, it is possible to test whether the sealing structure and sealing materials of the equipment can still maintain good sealing performance under extreme temperatures, prevent gas leakage, and ensure the stability of the gas pressure and insulation performance inside the equipment.

[0003] Currently, the sealing test mainly follows the provisions of the GB / T 11023-2018 standard. The test piece is placed in a closed plastic or metal cover using the cover method. After a certain period of time, a calibrated gas leak detector is used to measure the concentration of the tracer gas inside the cover, and the quantitative leak detection method for determining the relative leakage rate is calculated.

[0004] There are currently two leak detection methods as follows: 1. Currently, for the sealing test, a handheld gas leak detector is generally used to detect the gas concentration. To ensure the accuracy of the detection results, during the high and low temperature tests, the test personnel need to carry the gas leak detector into the environmental test chamber for leak detection. The extreme temperature in the test area (especially in a low-temperature environment) poses great safety risks to the personnel and equipment placed therein.

[0005] 2. Another method is to connect the test piece cover with a conduit. During the high and low temperature tests, the test personnel use a gas leak detector outside the environmental test chamber to detect leaks through the conduit opening. When using the method of connecting the test piece cover with a conduit for leak detection, the detection results are greatly affected by various factors such as the length of the conduit, the inner diameter of the conduit, the material of the conduit, the suction of the leak detector, temperature, and air pressure. After verification, the accuracy of the detection results will be greatly reduced.

[0006] In summary, the existing leak detection methods have technical drawbacks such as safety risks or low accuracy. Summary of the Invention

[0007] The purpose of the present invention is to provide a multi-channel time-division multiplexing sampling system and method for tracer gas leak detection, which solves the problems of technical drawbacks such as safety risks or low accuracy existing in the existing leak detection methods.

[0008] The present invention is realized through the following technical solutions: The present invention discloses a multi-channel time-division multiplexing sampling system for tracer gas leak detection, which includes a sampling circulation loop, an external sampling cavity, and a sampling self-purification device; During detection, the test piece is placed in a sealing cover, and the sealing cover is placed in a test chamber; The sampling circulation loop includes a gas return branch and multiple sampling points. Each sampling point is correspondingly connected to an intake solenoid valve to form multi-channel sampling; the sampling points are set at corresponding positions near the test piece; a first gas return solenoid valve is provided on the gas return branch; The external sampling cavity is provided with a self-sealing sampling port, and a sampling pump and a pressure sensor are arranged inside. The sampling pump is connected with a nozzle; the sampling pump is communicated with the intake solenoid valve; The sampling self-purification device includes an air extraction pump, an air extraction solenoid valve, an exhaust solenoid valve, and a second gas return solenoid valve; the intake end of the air extraction pump is communicated with the external sampling cavity through the air extraction solenoid valve, and the outlet end of the air extraction pump is connected with the exhaust solenoid valve; The sealing cover is provided with a gas return port. One end of the first gas return solenoid valve is connected to the gas return port, and the other end is communicated with the external sampling cavity; One end of the second gas return solenoid valve is connected to the air extraction pump, and the other end is connected to the gas return port.

[0009] Furthermore, the external sampling cavity is provided with an intake port, an outlet port, and an air extraction port. The sampling pump is connected with the intake solenoid valve through the intake port; The outlet port is connected with the first gas return solenoid valve; The air extraction port is connected with the air extraction solenoid valve.

[0010] Furthermore, the air extraction port is connected with the air extraction solenoid valve through a pipeline, and the outlet port is connected with the first gas return solenoid valve through a pipeline.

[0011] Furthermore, a magnetic attraction switch is also provided at the self-sealing sampling port. When the external sampling cavity is in a negative pressure state, the magnetic attraction switch is in a closed state to tightly close the self-sealing sampling port.

[0012] Furthermore, a pressure sensor is arranged inside the external sampling cavity, and the pressure sensor is linked with the air extraction pump, the air extraction solenoid valve, the exhaust solenoid valve, the first gas return solenoid valve, and the second gas return solenoid valve.

[0013] Furthermore, the number of branches for multi-channel sampling is set according to the size of the test piece.

[0014] Furthermore, the sampling points are connected with the intake solenoid valves through sampling gas pipes.

[0015] Furthermore, the intake solenoid valves are connected with the intake ports in the external sampling cavity through a collecting pipe.

[0016] Furthermore, the first gas return solenoid valve and the second gas return solenoid valve are respectively connected with the gas return port through sampling gas pipes.

[0017] Furthermore, an exhaust solenoid valve is connected to a gas collection tank through a pipeline.

[0018] The present invention also discloses a detection method based on the multi-channel time-division multiplexing sampling system for tracer gas leak detection, including a pre-purification process, a detection process at the first sampling point, and detection processes at subsequent sampling points; The pre-purification process specifically includes the following processes: Before sampling and analysis, open the air extraction solenoid valve and the exhaust solenoid valve, start the air extraction pump, and discharge the initial gas in the external sampling cavity to the outside of the test chamber and the sealing cover; Detect the pressure in the external sampling cavity. When the pressure in the external sampling cavity reaches the preset vacuum degree, close the air extraction solenoid valve and the exhaust solenoid valve, and stop the air extraction pump; The detection process at the first sampling point is specifically as follows: Open the intake solenoid valve corresponding to the first sampling point, start the sampling pump, and circulate the gas at the first sampling point to the external sampling cavity through the nozzle; When the pressure in the detection cavity reaches atmospheric pressure, open the first return air solenoid valve to return the gas in the cavity to the sealing cover and establish a gas circulation, and complete the leak detection of the tracer gas through the self-sealing sampling port. After the detection is completed, close the intake solenoid valve and the first return air solenoid valve, and stop the sampling pump; The detection processes at subsequent sampling points are specifically as follows: For gas sampling at the next sampling point corresponding to the test piece in the sealing cover, first open the air extraction solenoid valve and the second return air solenoid valve, start the air extraction pump, and circulate the residual gas in the external sampling cavity to the sealing cover; Detect the pressure in the external sampling cavity. When it is detected that the pressure in the external sampling cavity reaches the preset vacuum degree, close the air extraction solenoid valve and the second return air solenoid valve, and stop the air extraction pump; Open the intake solenoid valve corresponding to this sampling point, start the sampling pump, and circulate the gas at this sampling point to the external sampling cavity through the nozzle. When the pressure in the detection cavity reaches atmospheric pressure, open the first return air solenoid valve to return the gas in the external sampling cavity to the sealing cover and establish a gas circulation, and complete the leak detection of the tracer gas through the self-sealing sampling port. After the detection is completed, close the intake solenoid valve and the first return air solenoid valve, and stop the sampling pump; Same as the detection processes at subsequent sampling points, respectively operate to complete the gas sampling of the remaining sampling points.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention discloses a multi-channel time-division multiplexing sampling system and method for tracer gas leak detection, which extends the gas sampling in the sealed cover to an external external sampling cavity, and adopts multi-channel time-division multiplexing sampling technology, enabling continuous detection of multiple sampling points; the sampling circulation loop adopts a modular design, with each branch using an independently controlled intake solenoid valve, and the loop can be expanded according to the actual sampling location; before each use of the system, a vacuum self-purification pretreatment mechanism is used to discharge the initial gas in the external sampling cavity to the outside of the test chamber and the sealed cover, avoiding affecting the sampling detection results; when continuously sampling multiple sampling points, to avoid the previous sampling affecting the results of the subsequent detection, the residual gas in the external sampling cavity needs to be circulated back into the sealed cover; the action sequence of the intake solenoid valve, the return solenoid valve, the exhaust solenoid valve, and the vent solenoid valve is controlled by real-time detection of the pressure value in the sampling cavity, thereby achieving closed-loop feedback control.

[0020] Furthermore, a self-sealing sampling port is adopted to achieve a dynamic sealing effect, and a magnetic switch is also provided at the self-sealing sampling port. The self-sealing sampling port may leak when the cavity is under negative pressure, and the magnetic switch serves as a secondary sealing measure for the self-sealing sampling port. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic structural diagram of a multi-channel time-division multiplexing sampling system for tracer gas leak detection according to the present invention.

[0022] Among them, 1, sealed cover; 2, test piece; 3, sampling circulation loop; 4, external sampling cavity; 5, sampling self-purification device; 11, return port; 31, first return solenoid valve; 41, sampling pump; 42, nozzle; 43, pressure sensor; 44, intake port; 45, outlet port; 46, self-sealing sampling port; 47, magnetic switch; 48, exhaust port; 51, exhaust pump; 52, exhaust solenoid valve; 53, vent solenoid valve; 54, second return solenoid valve; SP1-SP2 are sampling points; V1-V2 are intake solenoid valves. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments.

[0024] The components described and illustrated in the accompanying drawings and embodiments of the present invention can be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of the present invention provided in the following drawings is not intended to limit the scope of the claimed invention, but merely represents a selected embodiment of the present invention. Based on the accompanying drawings and embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts fall within the protection scope of the present invention.

[0025] It should be noted that: the term "comprising", "including" or any other variant is intended to cover non-exclusive inclusion, such that a process, element, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or elements inherent to the process, element, method, article or device.

[0026] The following are the explanations of relevant terms: 1. Leak detection Means for detecting leak points and the concentration of leaked gas.

[0027] 2. Tracer gas In gas leak detection, it is the general term for gases that can be fully mixed with the gas to be detected, have stable properties themselves, and can be detected at extremely low concentrations.

[0028] The features and performance of the present invention will be further described in detail below in conjunction with embodiments.

[0029] As above Figure 1 As shown above, the present invention discloses a multi-channel time-division multiplexing sampling system for tracer gas leak detection, which mainly consists of a sampling circulation loop 3, an external sampling cavity 4, and a sampling self-purification device 5. The three parts are modularly designed and the loop can be expanded according to the actual sampling location.

[0030] During gas concentration detection, the test piece 2 is placed in the sealing cover 1, and the sealing cover 1 is placed in the test chamber. The rectangular frame with thick black lines in the figure is the test chamber.

[0031] In the sampling circulation loop 3, taking five sampling points as an example for illustration, SP1~SP5 are gas sampling points at the test piece 2, which are respectively connected to the intake solenoid valves V1~V5 through sampling gas pipes. The sampling circulation loop 3 can be modularly expanded according to the actual number of sampling points.

[0032] The sampling circulation loop 3 also has a return air branch, and a first return air solenoid valve 31 is provided on the return air branch. The first return air solenoid valve 31 is connected to the air outlet 45.

[0033] The external sampling cavity 4 is provided with an air inlet 44, an air outlet 45, and an air extraction port 48, and a sampling pump 41 is provided inside. The sampling pump 41 is connected to a nozzle 42.

[0034] The sampling self-purification device 5 includes an air extraction pump 51, an air extraction solenoid valve 52, an exhaust solenoid valve 53, and a second return air solenoid valve 54. The air extraction pump 51 is connected to the air extraction port 48 through the air extraction solenoid valve 52.

[0035] The external sampling cavity 4 is connected through the air inlet 44, the air outlet 45, and the sampling circulation loop 3. The sampling pump 41 inhales the gas at the sampling point in the sampling circulation loop 3 into the external sampling cavity 4 through the nozzle 42.

[0036] The sealing cover 1 is also provided with a return air port 11, which is a common return air port 11 connecting the external sampling cavity 4 and the sampling self-purification device 5, and is respectively connected to the first return air solenoid valve 31 and the second return air solenoid valve 54 through a sampling air pipe.

[0037] The external sampling cavity 4 is also provided with a self-sealing sampling port 46. The self-sealing sampling port 46 is a one-way valve to prevent external air from diluting the sampled gas in the cavity. When the pressure in the cavity is positive pressure, the leak detector probe is inserted into the cavity for analysis, and then taken out after the measurement, so as to realize the leak detection of the tracer gas at the self-sealing sampling port 46.

[0038] More preferably, the self-sealing sampling port 46 is one-way and may leak when the negative pressure is drawn in the cavity. Therefore, a magnetic switch 47 is also provided at the self-sealing sampling port 46. When the external sampling cavity 4 is in a negative pressure state, the magnetic switch 47 is closed, and secondary sealing is carried out through the magnetic switch 47 to prevent air leakage when the cavity is in negative pressure.

[0039] More preferably, a pressure sensor 43 is also provided in the external sampling cavity 4, and the linkage control with the sampling self-purification device 5 can be realized through the pressure feedback of the pressure sensor 43.

[0040] Specifically, the sampling self-purification device 5 performs self-purification treatment on the gas in the external sampling cavity 4 in the initial state by detecting the pressure value of the pressure sensor 43 in real time and controlling the opening and closing of the air extraction solenoid valve 52, the exhaust solenoid valve 53, and the air extraction pump 51.

[0041] Specifically, the intake solenoid valves V1~V5 are connected to the air inlet 44 in the external sampling cavity 4 through a collecting pipe.

[0042] More preferably, the exhaust solenoid valve 53 is connected to a gas collection tank for collecting the gas discharged after the initial purification.

[0043] After the entire system is connected, all valves and pumps are in the closed state.

[0044] When using a multi-channel time-division multiplexing sampling system for tracer gas leak detection of the present invention, the following process is specifically included: Before the single-trace gas leak detection sampling analysis, first close the magnetic switch 47, open the air extraction solenoid valve 52 and the exhaust solenoid valve 53, and start the air extraction pump 51. To avoid affecting the sampling and detection results, the initial gas in the external sampling cavity 4 is discharged to the atmosphere through the air extraction pump 51. Of course, the exhaust gas can also be collected through a gas collection tank to avoid pollution.

[0045] Detect the pressure in the external sampling cavity 4 through the pressure sensor 43. When the pressure in the external sampling cavity 4 reaches the preset vacuum degree, the self-purification process in the initial state ends, close the air extraction solenoid valve 52 and the exhaust solenoid valve 53, and stop the air extraction pump 51. After that, gas sampling is carried out at the sampling point SP1 corresponding to the test piece 2 in the sealing cover 1. At this time, open the intake solenoid valve V1 and start the sampling pump 41, and circulate the gas at the sampling point SP1 to the external sampling cavity 4 through the nozzle 42. When the pressure sensor 43 detects that the pressure in the cavity reaches normal pressure, open the first return air solenoid valve 31 to return the gas in the cavity to the sealing cover 1 to make the gas circulate. Open the magnetic switch 47, and complete the leak detection of the tracer gas through the self-sealing sampling port 46. After the detection is completed, close the magnetic switch 47, and at the same time close the intake solenoid valve V1 and the first return air solenoid valve 31, and stop the sampling pump 41.

[0046] Similarly, if gas sampling is required at the sampling point SP2 corresponding to the test piece 2 in the sealing cover 1, first open the air extraction solenoid valve 52 and the second return air solenoid valve 54, and start the air extraction pump 51. To avoid the influence of the previous sampling on the subsequent detection results, circulate the residual gas in the external sampling cavity 4 to the sealing cover 1. Detect the pressure in the external sampling cavity 4 through the pressure sensor 43. When the pressure in the external sampling cavity 4 reaches the preset vacuum degree, the self-purification process in the detection state ends, automatically close the air extraction solenoid valve 52 and the second return air solenoid valve 54, and stop the air extraction pump 51. At this time, open the intake solenoid valve V2 and start the sampling pump 41, and circulate the gas at the sampling point SP2 to the external sampling cavity 4 through the nozzle 42. When the pressure sensor 43 detects that the pressure in the cavity reaches normal pressure, open the first return air solenoid valve 31 to return the gas in the external sampling cavity 4 to the sealing cover 1. Open the magnetic switch 47, and complete the leak detection of the tracer gas through the self-sealing sampling port 46. After the detection is completed, close the magnetic switch 47, and at the same time close the intake solenoid valve V2 and the first return air solenoid valve 31, and stop the sampling pump 41.

[0047] Similarly, the gas sampling of the sampling points SP3~SP5 can be completed by separate operations.

[0048] Among them, the magnetic switch 47 belongs to secondary sealing. It is in front of the self-sealing sampling port 46 and needs to be opened before using the self-sealing sampling port 46.

[0049] When gas sampling is carried out from the second sampling point and subsequent sampling points, the residual gas in the external sampling cavity 4 is circulated into the sealing cover 1 because the cumulative leakage amount is measured in the present invention.

[0050] The present invention is based on the time-division multiplexing gas sampling technology. Through the modular arrangement of the gas channels and the programmed design of the control components, a full-process operation cycle of leak detection point gas sampling - external cavity detection - detection space self-purification - sampling point switching is realized during the sealing test under extreme ambient temperatures.

[0051] The present invention increases physical isolation to reduce the safety risks of personnel and equipment; adopts external remote operation and control to break through spatial limitations and improve environmental adaptability; strengthens the detection continuity and practicability through multi-channel modular design; and fully considers the possible influencing factors during the detection process to improve the accuracy of the detection results.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications or equivalent replacements can still be made to the specific implementation manners of the present invention, and any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A multi-channel time-division multiplexing sampling system for tracer gas leak detection, characterized in that, It includes a sampling loop circuit, an external sampling cavity, and a sampling self-purification device; During detection, the test piece is placed in a sealed cover, and the sealed cover is placed in a test chamber; The sampling loop circuit includes a return air branch and multiple sampling points. Each sampling point is correspondingly connected to an intake solenoid valve to form multi-channel sampling; the sampling points are set at corresponding positions near the test piece; a first return air solenoid valve is provided on the return air branch; The external sampling cavity is provided with a self-sealing sampling port, and a sampling pump and a pressure sensor are arranged inside. The sampling pump is connected with a spray nozzle; the sampling pump is communicated with the intake solenoid valve; The sampling self-purification device includes an air extraction pump, an air extraction solenoid valve, an exhaust solenoid valve, and a second return air solenoid valve; the intake end of the air extraction pump is communicated with the external sampling cavity through the air extraction solenoid valve, and the outlet end of the air extraction pump is connected with the exhaust solenoid valve; The sealed cover is provided with a return air port. One end of the first return air solenoid valve is connected with the return air port, and the other end is communicated with the external sampling cavity; One end of the second return air solenoid valve is connected with the air extraction pump, and the other end is connected with the return air port.

2. The multi-channel time-division multiplexing sampling system for tracer gas leak detection according to claim 1, wherein The external sampling cavity is provided with an intake port, an outlet port, and an air extraction port. The sampling pump is connected with the intake solenoid valve through the intake port; The outlet port is connected with the first return air solenoid valve; The air extraction port is connected with the air extraction solenoid valve.

3. A multi-channel time-division multiplexing sampling system for tracer gas leak detection according to claim 2, characterized in that, The air extraction port is connected with the air extraction solenoid valve through a pipeline, and the outlet port is connected with the first return air solenoid valve through a pipeline.

4. A multi-channel time-division multiplexing sampling system for tracer gas leak detection according to claim 1, characterized in that, A magnetic switch is further provided at the self-sealing sampling port. When the external sampling cavity is in a negative pressure state, the magnetic switch is in a closed state to tightly close the self-sealing sampling port.

5. A multi-channel time-division multiplexing sampling system for tracer gas leak detection according to claim 1, characterized in that, A pressure sensor is arranged inside the external sampling cavity, and the pressure sensor is linked with the air extraction pump, the air extraction solenoid valve, the exhaust solenoid valve, the first return air solenoid valve, and the second return air solenoid valve.

6. The multi-channel time-division multiplexing sampling system for tracer gas leak detection according to claim 1, wherein The number of branches of the multi-channel sampling is set according to the size of the test piece.

7. A multi-channel time-division multiplexing sampling system for tracer gas leak detection according to claim 1, characterized in that, The sampling points are connected with the intake solenoid valves through sampling air pipes.

8. A multi-channel time-division multiplexing sampling system for tracer gas leak detection according to claim 1, characterized in that, The intake solenoid valves are connected with the intake port in the external sampling cavity through a collecting pipe; The first return air solenoid valve and the second return air solenoid valve are respectively connected with the return air port through sampling air pipes.

9. A multi-channel time-division multiplexing sampling system for tracer gas leak detection according to claim 1, characterized in that, The exhaust solenoid valve is connected with a gas collection tank through a pipeline.

10. The detection method of the multi-channel time-division multiplexing sampling system for tracer gas leak detection according to any one of claims 1-9, characterized in that, It includes a pre-purification process, a detection process of the first sampling point, and a detection process of subsequent sampling points; The pre-purification process specifically includes the following processes: Before sampling and analysis, open the air extraction solenoid valve and the exhaust solenoid valve, start the air extraction pump, and discharge the initial gas in the external sampling cavity to the outside of the test chamber and the sealed cover; Detect the pressure in the external sampling cavity. When the pressure in the external sampling cavity reaches the preset vacuum degree, close the air extraction solenoid valve and the exhaust solenoid valve, and stop the air extraction pump; The detection process of the first sampling point is specifically: Open the intake solenoid valve corresponding to the first sampling point, start the sampling pump, and circulate the gas at the first sampling point to the inside of the external sampling cavity through the spray nozzle; When the pressure in the detection cavity reaches atmospheric pressure, open the first return air solenoid valve to make the gas in the cavity return to the sealed cover and establish a gas circulation, and complete the leak detection of the tracer gas through the self-sealing sampling port. After the detection is completed, close the intake solenoid valve and the first return air solenoid valve, and stop the sampling pump; The detection process of subsequent sampling points is specifically: For gas sampling at the next sampling point corresponding to the test piece in the sealed cover, first open the air extraction solenoid valve and the second return air solenoid valve, start the air extraction pump, and circulate the residual gas in the external sampling cavity to the sealed cover; Detect the pressure in the external sampling cavity. When the pressure in the external sampling cavity reaches the preset vacuum degree, close the air extraction solenoid valve and the second return air solenoid valve, and stop the air extraction pump; Open the intake solenoid valve corresponding to this sampling point, start the sampling pump, circulate the gas at this sampling point to the external sampling cavity through the nozzle. When the pressure in the detection cavity reaches atmospheric pressure, open the first return air solenoid valve to return the gas in the external sampling cavity to the sealed cover and establish a gas circulation, and complete the leak detection of the tracer gas through the self-sealing sampling port. After the detection is completed, close the intake solenoid valve and the first return air solenoid valve, and stop the sampling pump; Same as the detection process of subsequent sampling points, operate respectively to complete the gas sampling of the remaining sampling points.

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