On-line monitoring device and method for tiny leakage of safety valve

Abstract

The invention discloses an on-line monitoring device and method for tiny leakage of a safety valve, in the on-line monitoring device, a variable reluctance type power generation device is placed in a detection pipeline, an electric control device is arranged on the detection pipeline and is connected with the variable reluctance type power generation device through a wire, and a float flowmeter is connected with the detection pipeline through a threaded hole. The float flowmeter is connected with the automatic opening and closing device; when large-flow airflow passes through the detection pipeline, the float flowmeter controls the automatic opening and closing device to be opened through upward movement of a float. After the relief of the safety valve is completed, the electric control device sends an electric signal to the second coil to control the closing of the automatic opening and closing device; at the moment, the gas flow is calculated through the induced electromotive force of the coil; when small-flow airflow passes through the detection pipeline, the gas flow is calculated through the displacement of a floater in the floater flowmeter. On the premise that normal relief of the safety valve is not affected, flow measurement of two working conditions of fault leakage and overpressure relief of the safety valve is completed, and the detection efficiency is high.

Description

Technical Field

[0001] The present invention relates to the technical field of safety valve leakage monitoring, and in particular to an online monitoring device and method for slight leakage of a safety valve. Background Art

[0002] Hydrogen energy has attracted wide attention due to its advantages such as high energy efficiency, wide sources and no pollution. However, while hydrogen energy has advantages such as easy availability and zero carbon emissions, it also has many major disadvantages that are not conducive to storage and transportation, such as wide flammable range, low ignition energy, and difficulty in liquefaction. With the gradual maturity of high-pressure hydrogen storage technology, high-pressure gaseous hydrogen storage is currently the most widely used hydrogen energy storage method due to its high technical maturity and fast charging and discharging speed. The large-scale use of hydrogen energy meets my country's requirements for diversified reform of the energy supply side and the goal of building a clean, low-carbon, safe and efficient energy system. Hydrogen has the characteristics of wide combustion range and low ignition energy, and is prone to fire or explosion accidents, especially in the storage and transportation stage of high-pressure hydrogen, and its more uncertain factors make it very easy to cause serious accidents. As an overpressure protection device for equipment or pipelines, safety valves are widely used in hydrogen energy storage and transportation systems, playing an important role in protecting personnel safety and normal production operation. During the operation of the hydrogen storage system, the safety valve can reliably open and release pressure when the internal pressure exceeds the set pressure, and automatically close when the internal pressure is lower than the set pressure. The sealing performance of a valve refers to the ability of each sealing part in the valve to prevent the leakage of the medium, and is one of the most important technical performance indicators of the valve. However, in actual industrial equipment applications, nearly 20% of valves have leakage problems, which can be roughly divided into the following two types of leakage: (1) When the internal pressure of the equipment is close to the set pressure, the force on the sealing surface of the safety valve decreases, resulting in gas leakage; (2) The sealing surface is worn and damaged by foreign objects during use, resulting in failure and leakage of the sealing surface. According to statistics, in the petrochemical industry, nearly 40% of explosion accidents are caused by valve leakage; and in the medium transmission equipment in the petrochemical industry, the uncontrolled release of volatile organic compounds caused by valve leakage reaches 60%.

[0003] At present, the valve leakage detection methods include: negative pressure wave detection method, bubble method, ultrasonic leak detection method, infrared temperature measurement method, and acoustic emission detection. Negative pressure wave detection has weak anti-interference ability and is easily affected by pressure fluctuations. It has insufficient detection ability when the leakage rate is small. The bubble method uses the human eye as an observation tool to record the number of leaking bubbles, which is time-consuming and labor-intensive, and is prone to introduce errors. In addition, for weak leaks, the use of the bubble method is more time-consuming. Ultrasonic detection technology is applicable to the situation where gas flows through the leak hole to form a turbulent field, and as an active detection method, it is not suitable for real-time detection. Acoustic emission leak detection is a dynamic non-destructive test that is currently used more frequently. It can monitor the entire object being tested online, but due to the high noise in the working environment, the results of acoustic emission leak detection technology are greatly affected by noise. At present, most detection technologies require the support of professionals and professional equipment, and the detection range is small, the time required is long, the detection accuracy is relatively low, and some will cause damage to the valve, so they cannot meet the needs of on-site detection of small valve leaks. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide an online monitoring device and method for minor leakage of a safety valve, which can realize flow measurement of two working conditions, namely, safety valve fault leakage and overpressure discharge, without affecting the normal discharge of the safety valve, automatically change the detection method, and improve the detection accuracy of minor leakage.

[0005] Technical solution: An online monitoring device for small leakage of a safety valve, including a detection pipeline, a variable magnetic resistance power generation device, an electric control device, a float flowmeter, and an automatic opening and closing device;

[0006] The variable reluctance type power generation device is placed in the detection pipeline, the electric control device is arranged on the detection pipeline and connected with the variable reluctance type power generation device through a wire, the float flow meter is connected with the detection pipeline through a threaded hole, and the float flow meter is connected with the automatic opening and closing device;

[0007] When a large amount of airflow passes through the detection pipeline, the airflow drives the rotor to rotate, the variable reluctance generator works, and the float flowmeter controls the opening of the automatic opening and closing device by moving the float upward; when the safety valve is released, the electronic control device sends an electrical signal to the second coil to control the closing of the automatic opening and closing device; at this time, the induced electromotive force of the coil is obtained by the electronic control device, and the gas flow is calculated;

[0008] When a small flow of gas passes through the detection pipeline, the variable reluctance generator does not work, and the float moves upward under the action of the gas. At this time, the displacement of the float in the float flowmeter is obtained through the electronic control device, and the gas flow is calculated.

[0009] Furthermore, the detection pipeline includes a conversion joint and a detection pipeline housing, the detection device housing and the conversion joint are connected by threads, and the conversion joint can be connected to safety valves of different calibers; the detection device housing is made of magnetic conductive material and has a countersunk hole and a threaded through hole, the electronic control device is placed in the countersunk hole, and the float flowmeter is installed in the threaded through hole.

[0010] Furthermore, the variable reluctance power generation device includes a deflector, a rotor, a shaft, a bearing, a magnet, a first coil, a blade and a sleeve. The deflector is connected to the shaft through a bearing, the rotor is fixed on the shaft and positioned by a sleeve, the first coil is wound around the magnet and placed in a countersunk hole, and the deflector has blades arranged circumferentially; when the airflow passes through the deflector, it drives the rotor to rotate.

[0011] Furthermore, the electronic control device includes an electronic control device body, a first output interface, a second output interface, a first input interface and a second input interface; the first input interface is connected to the first coil, the second input interface is connected to the displacement sensor, the electronic control device body includes an electronic control processing module, an energy storage module and a display module, the electronic control processing module includes a frequency module, a rectifier module and a processing module; the first output interface is connected to the display module, the frequency module, the rectifier module and the processing module, and the second output interface is connected to the second coil.

[0012] Furthermore, the float flowmeter includes an upper end cover, a second shell, a displacement sensor, and a float, wherein a through hole is opened in the middle of the upper end cover and is arranged on the second shell, and the displacement sensor lead-out terminal is connected to the second input interface through a wire; a hole is opened on the side of the second shell, and the hole is used to install the slider guide rail in the automatic opening and closing device; the float is a cylinder with a hole in the middle and equal upper and lower surface areas, which is sleeved on the displacement sensor guide rail and can float up and down; the internal flow channel of the second shell has a certain cone angle, and the top of the cone angle is arranged at the connection end of the detection pipeline.

[0013] Further, the automatic opening and closing device includes a slider, a slider guide, a first spring, a guide rail rear cover, a support frame, a pipe rear cover, a second spring, a connecting plate, a connecting shaft, a terminal and a second coil, wherein the slider is made of magnetic material and is arranged on the slider guide, one end of the second spring is connected to the lifting ear on the slider, and the other end is connected to the lifting ear on the pipe rear cover, the slider guide is inserted into the hole, and the second coil on the guide rail rear cover is connected to the second output interface; one end of the first spring is fixed to the guide rail rear cover, and the other end is fixed to the rear end of the slider; the slider, the slider guide and the first spring are all arranged on the support frame, the support frame is bolted to the connecting plate, and the connecting plate is fixedly connected to the detection device housing; the pipe rear cover is connected to the connecting plate through the connecting shaft, and the pipe rear cover can rotate around the connecting shaft;

[0014] When the flow rate increases slowly, the float rises and the flow rate increases to the critical discharge flow rate Q sWhen the upper surface of the float touches the hook-shaped structure at the front end of the slider, the connection between the slider and the inner surface of the second shell is disconnected, triggering the rebound mechanism. Under the action of the restoring force of the first spring, the slider moves to the right, driving the second spring to move, and the rear cover of the pipeline opens;

[0015] When the safety valve is released, the flow rate drops to the critical discharge flow rate Q s , the rear cover of the pipe needs to be closed, at this time the electronic control device sends an electrical signal to the wiring terminal, the second coil is energized, and a magnetic field is generated; the slider moves in the direction away from the rear cover of the guide rail under the action of the magnetic force, pulling the first spring and the second spring, and the rear cover of the pipe slowly closes; when the front end of the slider is reconnected with the inner surface of the second shell, it returns to the initial state.

[0016] A method for realizing any of the above-mentioned online monitoring devices, including a method for detecting a small flow rate of a safety valve leakage, a variable magnetic resistance flow rate detection and a power generation method;

[0017] When a small leak occurs, the safety valve leakage small flow detection method is used, and the float flowmeter measures the small flow generated; the implementation process is as follows:

[0018] When the gas enters the test pipe from the conversion joint, it drives the rotor to rotate at an angular velocity of ω through the flow diversion effect of the leaf. At the same time, it enters the float flowmeter through the threaded through hole on the shell of the detection device. Under the action of the gas, the float moves upward. When the flow is stable, the float hovers at a certain place. Let the displacement at this time be x; then the force on the float is as follows:

[0019] mg=Δp·A

[0020] Where m is the mass of the float, Δp is the pressure difference between the upper and lower surfaces of the float, and A is the projected area of ​​the float along the displacement direction;

[0021] From the orifice flow formula:

[0022]

[0023] A 0 =f(x)

[0024] Among them, C d is the flow coefficient, ρ is the gas density; A 0 is the flow area at the center of gravity of the float;

[0025] The gas flow rate q 1流 The formula is:

[0026]

[0027] According to the above formula, the displacement x of the float obtained by the displacement sensor is transmitted to the electronic control device to obtain the flow rate through the float flowmeter;

[0028] When the leakage flow is large, the rotor rotates, and the variable reluctance flow detection and power generation method is used to measure the generated flow; the implementation process is as follows:

[0029] When the gas drives the rotor to rotate at an angular velocity ω, the first coil generates an induced electromotive force E:

[0030] E=ψ(ω)

[0031] Therefore, the frequency of the induced electromotive force E is obtained through the frequency module of the electronic control device, and the current rotor speed ω = ψ -1 (E); rotor angular velocity ω and flow rate q 2 The relationship is as follows:

[0032]

[0033] Where r is the average radius of the rotor blade, α is the angle between the rotor blade and the axis, c is a constant, and A is the flow cross-sectional area of ​​the rotor;

[0034] Then the gas flow rate q 2流 for:

[0035]

[0036] According to the above formula, the induced electromotive force ψ(ω) generated by the first coil is transmitted to the electronic control device to obtain the flow rate through the float flowmeter.

[0037] Compared with the prior art, the present invention has the following significant effects:

[0038] 1. The online monitoring device of the present invention is designed with an airflow discharge channel for normal discharge of the safety valve and a monitoring channel for small leakage when the safety valve is closed, which realizes the flow measurement of two working conditions of safety valve failure leakage and overpressure discharge without affecting the normal discharge of the safety valve, and has high detection efficiency;

[0039] 2. The online monitoring device of the present invention is designed with a discharge channel opening and closing mechanism based on spring energy storage and electromagnetic actuation, which realizes automatic opening of the discharge channel when the valve is discharged and active closing of the discharge channel when the valve is closed;

[0040] 3. The online monitoring device of the present invention is designed with a variable reluctance power generation mechanism to realize power generation and storage when the gas is normally discharged, so that the device can be separated from the external power supply and realize self-sufficiency in electricity. It does not require an external power supply and is suitable for safety valve maintenance scenarios in harsh field environments. It can improve maintenance efficiency, improve the stability of the hydrogen storage system, and expand its applicable scenarios;

[0041] 4. The online monitoring method of the present invention has a good gathering effect on the leaked gas through the small leakage monitoring channel. Under the premise of no human intervention and no influence on the normal operation of the safety valve, the detection method is automatically changed, thereby improving the detection accuracy of small leaks. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 (a) is a partial cross-sectional schematic diagram of the main structure of the present invention;

[0043] (b) is a schematic diagram of the present invention.

[0044] Figure 2 It is a schematic diagram of the detection pipeline structure of the present invention;

[0045] Figure 3 (a) is a cross-sectional view of the variable reluctance power generation device of the present invention;

[0046] (b) is a schematic diagram of the overall structure of the variable reluctance power generation device of the present invention;

[0047] (c) is a schematic diagram of the magnet and coil in the variable reluctance generator;

[0048] Figure 4 It is a schematic diagram of the structure of the electric control device of the present invention;

[0049] Figure 5 It is a schematic diagram of the structure of the float flowmeter of the present invention;

[0050] Figure 6 (a) is a schematic diagram of the overall structure of the automatic opening and closing device of the present invention;

[0051] (b) Figure 6 The front view of (a);

[0052] Figure 7 This is a control principle diagram of the electronic control device of the present invention;

[0053] Figure 8 (a) is a schematic diagram of the closed state of the automatic opening and closing device of the present invention;

[0054] (b) is a schematic diagram of the automatic opening and closing device of the present invention in the open state;

[0055] Fig. 9 It is a detection flow chart of the present invention. DETAILED DESCRIPTION

[0056] The present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0057] like Figure 1As shown in (a) and (b) of the figure, an online monitoring device for small leakage of a safety valve includes a mechanical structure part. The mechanical structure part includes: a detection pipeline 1, a variable reluctance type power generation device 2, an electric control device 3, a float flowmeter 4, and an automatic opening and closing device 5.

[0058] like Figure 2 As shown, the detection pipeline 1 includes: a conversion joint 11 and a detection pipeline housing 12. The conversion joint 11 is used to connect safety valves of different calibers to the detection pipeline 1, and the detection device housing 12 is made of magnetic conductive material to provide a detection flow channel; the detection device housing 12 is connected to the conversion joint 11 by threads, and the detection device housing 12 is provided with a countersunk hole 13 and a threaded through hole 14, wherein the countersunk hole 13 is used to place a magnet 25 and an electric control device body 31, and the threaded through hole 14 is connected to the float flowmeter 4.

[0059] like Figure 3 As shown in (a), (b) and (c) in the figure, the variable reluctance type power generation device 2 includes: a deflector 21, a rotor 22, a shaft 23, a bearing 24, a magnet 25, a first coil 26, a leaf 27 and a sleeve 28. The rotor 22 and the deflector 21 are connected to the shaft 23 through the bearing 24, and the sleeve 28 plays a positioning role. When the airflow passes through the deflector 21, it drives the rotor 22 to rotate around the shaft 23, and the first coil 26 is wound around the magnet 25 and placed in the counterbore 13 of the detection pipeline 1. The deflector 21 is provided with a leaf 27 along the circumferential direction; the rotor 22 is made of a magnetic conductive material.

[0060] like Figure 4 As shown, the electric control device 3 includes an electric control device body 31, a first output interface 32, a second output interface 33, a first input interface 34, and a second input interface 35. The electric control device body 31 includes an electric control processing module, an energy storage module, and a display module. The first input interface 34 is connected to the first coil 26, and the electric signal generated by the first coil 26 is input into the electric control device body 31. The second input interface 35 is connected to the displacement sensor 43, and the displacement of the float 44 is input into the electric control device body 31. The first output interface 32 is connected to other electrical components of the device to provide energy, and the second output interface 33 is connected to the second coil 511 to provide an electric signal.

[0061] The electronic control processing module includes a frequency module, a rectifier module and a processing module. The frequency module is used to obtain the frequency of the induced electromotive force output by the first coil 26 and transmit the frequency to the processing module; the rectifier module is used to convert the unstable induced electromotive force output by the first coil 26 into a voltage signal with stable frequency and amplitude, and output the stable voltage signal to the energy storage module. The energy storage module can store the electric energy generated during discharge to maintain the operation of the entire device, and the display module can display the flow measured by the device at any time.

[0062] like Figure 5As shown, the float flowmeter 4 includes: an upper end cover 41, a second housing 42, a displacement sensor 43, and a float 44. Among them, the upper end cover 41 has a through hole and is arranged on the housing 42, and the displacement sensor 43 leads to the wiring terminal and is connected to the second input interface 35 through a wire; the second housing 42 has a hole 45, which is used to connect the slider guide 52 and connect to the atmosphere, and serves as a gas discharge port when the safety valve leaks a small flow; the float 44 is a cylinder with a hole in the middle and equal upper and lower surface areas, which is sleeved on the displacement sensor guide and can float up and down; the internal flow channel of the second housing 42 has a certain cone angle, and the top of the cone angle is arranged at the connection end of the detection pipeline 1. When the leakage of the safety valve is small, the leaked gas is discharged through the hole 45, and the automatic opening and closing device 5 remains in a closed state.

[0063] like Figure 6 As shown in (a) and (b), the automatic opening and closing device 5 includes: a slider 51, a slider guide 52, a first spring 53, a guide rail back cover 54, a support frame 55, a pipe back cover 56, a second spring 57, a connecting plate 58, a connecting shaft 59, a terminal 510, and a second coil 511. Among them, the slider 51 is made of magnetic material and is arranged on the slider guide rail 52. The ears on both sides of the slider 51 are connected to the ears on both sides of the pipe back cover 56 through the second spring 57. One end of the first spring 53 is fixed on the guide rail back cover 54, and the other end is fixed to the rear end of the slider 51. The slider guide rail 52 is inserted into the hole 45 of the second shell 42 of the float flowmeter. The second coil 511 on the guide rail back cover 54 is wound with a wire and connected to the second output interface 33. The slider 51, the slider guide rail 52 and the first spring 53 are arranged on the support frame 55. The support frame 55 is bolted to the connecting plate 58. The connecting plate 58 is welded to the detection device housing 12. The pipe back cover 56 is connected to the connecting plate 58 through the connecting shaft 59. The pipe back cover 56 can rotate around the connecting shaft 59 to realize the opening and closing of the detection device.

[0064] An online monitoring method for a safety valve minor leakage includes a safety valve minor leakage flow detection method, a variable magnetic resistance flow detection and power generation method, and a rear cover automatic opening and closing method. The control principle diagram of the electronic control device is as follows: Figure 7 shown.

[0065] The principle of the method for detecting the leakage of a hydrogen storage safety valve is as follows: Under normal circumstances, the rear cover 56 of the pipeline is closed. The gas enters the test pipeline from the conversion joint 11, and drives the rotor 22 to rotate at an angular velocity ω through the flow guide of the leaf 27. At the same time, it enters the float flowmeter 4 through the threaded through hole 14 on the detection device housing 12. Under the action of the gas, the float 44 moves upward. When the flow is stable, the float 44 hovers at a certain place. Assume that the displacement at this time is x. The force on the float 44 is as follows:

[0066] mg=Δp·A

[0067] Wherein, m is the mass of the float 44, Δp is the pressure difference between the upper and lower surfaces of the float 44, and A is the projected area of ​​the float 44 along the displacement direction;

[0068] From the orifice flow formula:

[0069]

[0070] Among them, C d is the flow coefficient, ρ is the gas density;

[0071] A 0 A is the gas flow area 0 =f(x) is a function of displacement x. Since the float flowmeter 4 measures a small flow rate, the float 44 is small in size, and A 0 Take the flow area at the center of gravity of the float 44;

[0072] The gas flow rate q 1流 The formula is:

[0073]

[0074] The displacement x of the float is obtained by the displacement sensor 43 and transmitted to the electronic control device 3, so that the flow rate passing through the float flowmeter can be obtained.

[0075] The principle of the variable reluctance flow detection and power generation method is as follows: the gas drives the rotor 22 to rotate at an angular velocity ω, and the first coil 26 is wound around the magnet 25. The rotation of the rotor 22 changes the air gap of the magnetic circuit, causing the magnetic resistance in the magnetic circuit to change, while the magnetic potential of the entire magnetic field is constant, changing the magnetic flux in the magnetic circuit, so that the coil generates an induced electromotive force E=ψ(ω). Therefore, by obtaining the frequency of the induced electromotive force E through the frequency module 34 of the electronic control device 3, the current rotor 22 speed ω=ψ -1 (E).

[0076] Rotor angular velocity ω and flow rate q 2 There are the following relationships:

[0077]

[0078] Among them, r is the average radius of the blades of the rotor 22, α is the angle between the blades of the rotor 22 and the axis, c is a constant, and A is the flow cross-sectional area of ​​the rotor 22.

[0079] Then the gas flow rate q 2流 for:

[0080]

[0081] However, it should be noted that due to the uneven rotor speed, the frequency and size of the induced electromotive force are unstable. Therefore, a rectifier module 35 is added to the electronic control device 3 to convert this uneven and weak induced electromotive force E into a stable voltage signal, which is stored in the energy storage module 38 to provide electrical energy for the entire detection device. This flow measurement method is suitable for larger flow rates, because the flow rate is small when leaking and the rotor 22 does not rotate. When there is a small leak, the small flow rate generated is measured by the float flowmeter 4; through the above method, classification detection of different flow sizes is achieved.

[0082] The principle of the automatic opening and closing method of the rear cover is as follows: Under normal circumstances, the pipeline rear cover 56 is closed, the slider 51 is located in the hole 45 of the second housing 42 of the float flowmeter, and the front end of the slider 51 is connected to the inner surface of the float flowmeter housing 42 through a hook structure. One end of the first spring 53 is fixed to the guide rail rear cover 54, and the other end is fixed to the rear end of the slider 51. At this time, the first spring 53 is in a stretched state, one end of the second spring 57 is connected to the ear on the slider 51, and the other end is connected to the ear on the pipeline rear cover 56. The pipeline rear cover 54 is subjected to the tension of the second spring 57 and fits tightly to the detection device housing 12 to play a sealing role. Figure 8 As shown in (a) in Fig. 9 As shown in the figure, when the flow rate increases slowly, the float rises and the flow rate increases to the critical discharge flow rate Q s When the float 44 is in contact with the hook-shaped structure at the front end of the slider 51, the connection between the slider 51 and the inner surface of the second housing 42 is disconnected, triggering the rebound mechanism. Under the action of the restoring force of the first spring 53, the slider 51 moves to the right, driving the second spring 57 to move, and the pipeline rear cover 56 opens. Figure 8 As shown in (b) in the figure. When the safety valve is released, the flow rate drops to the critical release flow rate Q s , the pipe rear cover 56 needs to be closed, at this time the electric control device 3 sends an electrical signal to the terminal 510 on the guide rail rear cover 54, the second coil 511 is energized, and a magnetic field is generated; the slider 51 moves away from the guide rail rear cover 56 under the action of the magnetic force, pulling the first spring 53 and the second spring 57, and the pipe rear cover 56 slowly closes; when the front end of the slider 51 is reconnected with the inner surface of the second housing 42, it returns to the initial state. The whole process does not require human intervention, and the corresponding action is generated by the device itself, realizing automatic detection of flow size.

[0083] In this way, the classification and automatic detection of the flow rates of the hydrogen storage safety valve in two states, leakage and discharge, can be achieved, and power generation and storage of electrical energy can be achieved during operation.

Claims

1. An online monitoring device for minor leakage of a safety valve, characterized in that: It comprises a detection pipeline (1), a variable magnetic resistance type power generation device (2), an electric control device (3), a float flow meter (4), and an automatic opening and closing device (5); The variable reluctance type power generation device (2) is placed in the detection pipeline (1), the electric control device (3) is arranged on the detection pipeline (1) and is connected to the variable reluctance type power generation device (2) through a wire, the float flow meter (4) is connected to the detection pipeline (1) through a threaded hole; the float flow meter (4) is connected to the automatic opening and closing device (5); When a large amount of gas flows through the detection pipeline (1), the variable reluctance type power generation device (2) works, and the float flowmeter (4) controls the opening of the automatic opening and closing device (5) by moving the float (44) upward; when the safety valve is released, the electric control device (3) sends an electric signal to the second coil (511) to control the closing of the automatic opening and closing device (5); in this process, the induced electromotive force of the coil is obtained by the electric control device (3), and the gas flow is calculated; When a small flow rate of gas passes through the detection pipeline (1), the variable reluctance type power generation device (2) does not work, and the float (44) moves upward under the action of the gas; at this time, the displacement of the float in the float flowmeter (4) is obtained through the electronic control device (3), and the gas flow rate is calculated.

2. The online monitoring device for small leakage of a safety valve according to claim 1 is characterized in that: The detection pipeline (1) comprises a conversion joint (11) and a detection pipeline housing (12); the detection device housing (12) is connected to the conversion joint (11) by means of threads; the conversion joint (11) can be connected to safety valves of different calibers; the detection device housing (12) is made of magnetic conductive material and is provided with a countersunk hole (13) and a threaded through hole (14); the electric control device (3) is placed in the countersunk hole (13); and the float flowmeter (4) is installed in the threaded through hole (14).

3. The online monitoring device for minor leakage of a safety valve according to claim 2 is characterized in that: The variable reluctance power generation device (2) comprises a deflector (21), a rotor (22), a shaft (23), a bearing (24), a magnet (25), a first coil (26), a leaf stalk (27) and a shaft sleeve (28); the deflector (21) is connected to the shaft (23) via the bearing (24); the rotor (22) is fixedly arranged on the shaft (23) and positioned via the shaft sleeve (28); the first coil (26) is wound around the magnet (25) and placed in the counterbore (13); and the leaf stalk (27) is arranged along the circumferential direction of the deflector (21); when airflow passes through the deflector (21), the rotor (22) is driven to rotate.

4. The online monitoring device for minor leakage of a safety valve according to claim 3 is characterized in that: The electric control device (3) comprises an electric control device body (31), a first output interface (32), a second output interface (33), a first input interface (34) and a second input interface (35); the first input interface (34) is connected to the first coil (26), the second input interface (33) is connected to the displacement sensor (43), the electric control device body (31) comprises an electric control processing module, an energy storage module and a display module, the electric control processing module comprises a frequency module, a rectifier module and a processing module; the first output interface (32) is connected to the display module, the frequency module, the rectifier module and the processing module, and the second output interface (35) is connected to the second coil (511).

5. The online monitoring device for minor leakage of a safety valve according to claim 4 is characterized in that: The float flowmeter (4) comprises an upper end cover (41), a second housing (42), a displacement sensor (43), and a float (44), wherein the upper end cover (41) has a through hole in the middle and is arranged on the second housing (42), and the displacement sensor (43) leads out a wiring terminal and is connected to the second input interface (35) through a wire; the second housing (42) has a hole (45) in the side, and the hole (45) is used to install a slider guide rail (52) in the automatic opening and closing device (5) and is connected to the atmosphere; the float (44) is a cylinder with a hole in the middle and equal upper and lower surface areas, and is sleeved on the displacement sensor guide rail and can float up and down; the flow channel inside the second housing (42) has a certain cone angle, and the top of the cone angle is arranged at the connection end of the detection pipeline (1).

6. The online monitoring device for minor leakage of a safety valve according to claim 5 is characterized in that: The automatic opening and closing device (5) comprises a slider (51), a slider guide rail (52), a first spring (53), a guide rail rear cover (54), a support frame (55), a pipe rear cover (56), a second spring (57), a connecting plate (58), a connecting shaft (59), a connecting terminal (510) and a second coil (511), wherein the slider (51) is made of magnetic material and is arranged on the slider guide rail (52); one end of the second spring (57) is connected to a lifting ear on the slider (51) and the other end is connected to a lifting ear on the pipe rear cover (56); the slider guide rail (52) is inserted into the hole (45) , the second coil (511) on the guide rail rear cover (54) is connected to the second output interface (33); one end of the first spring (53) is fixed to the guide rail rear cover (54), and the other end is fixed to the rear end of the slider (51); the slider (51), the slider guide rail (52) and the first spring (53) are all arranged on a support frame (55), the support frame (55) is bolted to a connecting plate (58), and the connecting plate (58) is fixedly connected to the detection device housing (12); the pipeline rear cover (56) is connected to the connecting plate (58) through a connecting shaft (59), and the pipeline rear cover (56) can rotate around the connecting shaft (59); When the flow rate increases slowly, the float rises and the flow rate increases to the critical discharge flow rate Q s When the upper surface of the float (44) touches the hook-shaped structure at the front end of the slider (51), the connection between the slider (51) and the inner surface of the second housing (42) is disconnected, triggering the rebound mechanism. Under the action of the restoring force of the first spring (53), the slider (51) moves to the right, driving the second spring (57) to move, and the pipeline rear cover (56) opens; When the safety valve is released, the flow rate drops to the critical discharge flow rate Q s , the pipe rear cover (56) needs to be closed, at which time the electric control device (3) sends an electrical signal to the wiring terminal (510), the second coil (511) is energized, and a magnetic field is generated; the slider (51) is moved in a direction away from the guide rail rear cover (56) by the magnetic force, pulling the first spring (53) and the second spring (57), and the pipe rear cover (56) is slowly closed; when the front end of the slider (51) is reconnected with the inner surface of the second shell (42), it returns to the initial state.

7. The method for implementing the online monitoring device according to any one of claims 1 to 6, characterized in that: Including safety valve leakage micro-flow detection method, variable magnetic resistance flow detection and power generation method; When a small leakage occurs, a safety valve leakage small flow detection method is used, and the small flow generated is measured by a float flowmeter (4); the implementation process is as follows: When the gas enters the test pipe from the conversion joint (11), it drives the rotor (22) to rotate at an angular velocity ω through the flow-guiding effect of the leaf stalk (27); at the same time, it enters the float flowmeter (4) through the threaded through hole (14) on the detection device housing (12). Under the action of the gas, the float (44) moves upward. When the flow rate is stable, the float (44) hovers at a certain position. Assume that the displacement at this time is x; then the force on the float (44) is as follows: mg=Δp·A Where m is the mass of the float, Δp is the pressure difference between the upper and lower surfaces of the float, and A is the projected area of ​​the float along the displacement direction; From the orifice flow formula: A0=f(x) Among them, C d is the flow coefficient, ρ is the gas density; A0 is the flow area at the center of gravity of the float; The gas flow rate q 1流 The formula is: According to the above formula, the displacement x of the float obtained by the displacement sensor (43) is transmitted to the electronic control device (3) to obtain the flow rate passing through the float flowmeter; When the leakage flow is large, the rotor (22) rotates, and a variable magnetic resistance flow detection and power generation method is used to measure the generated flow; the implementation process is as follows: When the gas drives the rotor (22) to rotate at an angular velocity ω, the first coil (26) generates an induced electromotive force E: E=ψ(ω) Thus, the frequency of the induced electromotive force E is obtained by the frequency module (34) of the electronic control device (3), and the current rotor (22) speed ω=ψ -1 (E); The relationship between the rotor angular velocity ω and the flow rate q2 is as follows: Where r is the average radius of the rotor blade, α is the angle between the rotor blade and the axis, c is a constant, and A is the flow cross-sectional area of ​​the rotor; Then the gas flow rate q 2流 for: According to the above formula, the induced electromotive force ψ(ω) generated by the first coil (26) is transmitted to the electronic control device (3) to obtain the flow rate passing through the float flowmeter.

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