Portable breather valve online detection device and detection method

Abstract

The invention relates to a portable breather valve online detection device and detection method, and belongs to the technical field of valve detection. According to the structure, an air storage tank is connected with a pumping and beating dual-purpose air pump, an electromagnetic valve and a controller, and a one-way valve is arranged between the pumping and beating dual-purpose air pump and the air storage tank; a temperature sensor and a pressure sensor are arranged between the gas storage tank and the controller; according to the invention, the problems of large size, heavy weight and inaccurate detection result of detection equipment in the prior art are solved; the occupied space and the weight of the equipment are greatly reduced, so that the detection equipment is portable.

Description

Technical Field

[0001] The invention relates to a valve detection device, and in particular to a portable breathing valve online detection device and a detection method. Background Art

[0002] The breathing valve is an important oil tank accessory. Through reasonable process structure and control of valve switching, it can effectively adjust the gas pressure in the tank, reduce or inhibit oil evaporation, and reduce oil loss.

[0003] The failure of the breathing valve may lead to serious consequences. For example, on December 8, 2018, Henan Energy and Chemical Group Luoyang Yonglong Energy Chemical Co., Ltd. suffered a toxic gas leak due to the failure of the safety valve, causing a major poisoning accident, resulting in 3 deaths and 1 injury.

[0004] Therefore, it is necessary to conduct regular inspections of the breathing valve. Traditional breathing valve inspections use two independent suction pumps and inflation pumps to reversely pressurize or depressurize the breathing valve to be inspected. The equipment takes up a lot of space and is heavy. In addition, the traditional breathing valve inspection device uses long pipes to connect the fan and the large gas storage tank, and the micromanometer and the large gas storage tank. When inspecting a breathing valve with a diameter of 250mm, the diameter of the gas storage tank is generally greater than 2.5 meters, and its height is generally greater than 2 meters, resulting in a large device size.

[0005] In addition, when there is insufficient gas in the gas tank of traditional detection equipment, the inclination angle produced by the breathing valve may be mistakenly detected as the breathing valve being opened, resulting in inaccurate detection results. Summary of the invention

[0006] In view of the problems existing in the above-mentioned prior art, the present invention provides a portable online detection device for breathing valves, which solves the problems in the prior art that the detection equipment is large in size, heavy in weight and the detection results are inaccurate.

[0007] Another object of the present invention is to provide a portable breathing valve online detection method.

[0008] The technical solution of the present invention is as follows:

[0009] A portable breathing valve online detection device, wherein an air storage tank is respectively connected to a whipping dual-purpose air pump, a solenoid valve and a controller, a one-way valve is arranged between the whipping dual-purpose air pump and the air storage tank; a temperature sensor and a pressure sensor are arranged between the air storage tank and the controller.

[0010] The gas storage tank is connected to the breathing valve to be tested by a flange.

[0011] In the controller, a mathematical model is established when the breathing valve core produces an inclination angle, and the mathematical model is as follows:

[0012]

[0013] Where: x is the effective cutoff length m; b is the critical pressure ratio b = 0.2 ~ 0.5; σ is the pressure ratio; P in is the upstream pressure Pa; P out is the downstream pressure Pa;

[0014]

[0015] Where: sb is the solid-phase friction coefficient of the elbow, λ sb =2.2;ξ b is the local resistance coefficient of airflow through the elbow:

[0016]

[0017] Where: D is the pipe diameter m; R is the radius corresponding to the curved arc of the pipe centerline; θ is the central angle corresponding to the curved arc of the pipe centerline;

[0018]

[0019] Where: a is the air flow density kg / m3; P 0 is the standard atmospheric pressure pa; T is the actual temperature K

[0020]

[0021] Where: μ a is the air flow velocity in m / s.

[0022] Q max2 =CQ max (7)

[0023] Where: Q max2 is the air pump flow rate; C is the circumference of the valve disc.

[0024] In the controller, a theoretical simplified model of the breathing valve is established, and a mathematical model of the breathing valve is established through the gas state equation, motion equation, and flow equation.

[0025] According to Newton's second law, the motion equation of the breathing valve is established;

[0026]

[0027] Where: P(t) is the change of the pressure in the tank with time pa / s, A is the area of ​​the valve core affected by the pressure in the tank m2, k is the spring coefficient N / m, x(t) is the change of the breathing valve opening with time m, M is the mass of the valve core kg, F is f Resistance N caused by valve stem rust, μ viscous resistance coefficient;

[0028] As the gas is an ideal gas and satisfies the ideal gas state equation, the state equation of the gas in the tank is:

[0029] PV=mRT(9)

[0030] Based on the fact that the volume of the gas tank does not change, the internal air mass changes with the internal pressure, and the gas temperature does not change when the gas is discharged. At this time, the pressure and gas mass change with time. The derivative of equation (9) is:

[0031] P(t)V=m(t)RT(10)

[0032] The mass of the gas in the tank can be calculated by subtracting the mass discharged when the breathing valve is working from the initial mass of the gas in the tank:

[0033]

[0034] Where: V is the volume of the gas storage tank m3, m(t) is the amount of change of the gas mass in the tank over time kg / s, R is the gas constant J / (mol·k), T is the temperature in the tank k, m 0 is the initial mass of the gas in the tank kg, ρ is the gas density at normal temperature and pressure kg / m3, Q(t) is the change of flow rate over time m3 / t2;

[0035] The flow equation is,

[0036]

[0037] Where: C is the outer circumference of the valve disc m, b is the critical pressure ratio b = 0.2 ~ 0.5, σ is the pressure ratio, P in is the upstream pressure Pa, P out is the downstream pressure Pa;

[0038] Leakage detection formula

[0039]

[0040] That is, the leakage per unit time ΔV is as shown in formula (9):

[0041]

[0042] Where: V is the volume of the gas tank, n is 1 The amount of gas in the gas tank at state 1, n 2 The amount of gas in the gas tank at state 2, R is the molar gas constant, T is the temperature of the gas tank, p 1 The pressure in the gas tank at state 1, p 2 The pressure in the gas tank in state 2.

[0043] A portable breathing valve online detection method, including breathing valve pressure monitoring, valve stem displacement detection and breathing valve leakage detection;

[0044] The breathing valve pressure detection comprises the following specific steps:

[0045] A1 Preparation before testing:

[0046] Input the parameters of the breathing valve to be tested into the controller, calculate the air pump flow required for this test through the controller, and adjust the air pump flow to the required range after obtaining the data;

[0047] a2 turns on pressure detection:

[0048] Connect the breathing valve to be tested to the gas tank, open the one-way valve to allow the whipping dual-purpose air pump to communicate with the gas tank, turn on the whipping dual-purpose air pump, and the temperature sensor and pressure sensor begin to record the corresponding data in the gas tank and transmit them to the PLC connected to it; when the breathing valve to be tested is opened for a period of time due to the change of gas pressure in the small gas tank until the pressure in the tank is stable, the PLC controls the whipping dual-purpose air pump 1 to restore the pressure of the gas tank to the initial level, and then the PLC continues to control the whipping dual-purpose air pump to open the breathing valve to be tested, and repeat this process until the breathing valve to be tested is opened four times; by observing the pressure curve in the PLC, when the pressure curve after the breathing valve is opened oscillates around the normal opening pressure line periodically, it can be judged that the opening pressure of the breathing valve is normal; when the pressure curve after the breathing valve is opened oscillates around a pressure line lower than or higher than the normal opening pressure line periodically, it can be judged that the opening pressure of the breathing valve is abnormal;

[0049] a3 Post-test operation:

[0050] Turn off the whipping and beating dual-purpose air pump 1, open the solenoid valve 7, and restore the pressure to the atmospheric pressure level;

[0051] The breathing valve stem displacement detection comprises the following specific steps:

[0052] b1 Preparation before experiment:

[0053] After completing the pre-test preparation a1 of the opening pressure test, the parameters of the breathing valve to be tested are input into the controller, and the controller calculates the normal pressure curve of the breathing valve to be tested when it is normal;

[0054] b2 valve stem displacement detection:

[0055] Connect the breathing valve to be tested to the gas tank, open the one-way valve to allow the whipping dual-purpose air pump to communicate with the gas tank, turn on the whipping dual-purpose air pump, and the temperature sensor and pressure sensor begin to record the corresponding data in the gas tank and transmit them to the PLC connected thereto; when the breathing valve to be tested is opened for a period of time due to the change in the gas pressure in the gas tank, the PLC controls the whipping dual-purpose air pump to restore the pressure of the gas tank to the initial level, and then the PLC continues to control the whipping dual-purpose air pump to open the breathing valve to be tested, and repeat this process until the safety valve to be tested is opened four times; by comparing the pressure curve generated by the PLC in preparation b1 before the experiment with the pressure curve recorded by the pressure sensor in the valve stem displacement detection b2, when the amplitude of the curve in b2 is less than the amplitude in b1, it is judged that the valve stem friction of the breathing valve to be tested is too large; when the frequency of the curve in b2 is less than the frequency of the curve in b1, it is judged that the spring coefficient of the breathing valve to be tested is too small;

[0056] b3 Post-test operation:

[0057] Turn off the dual-purpose air pump and open the solenoid valve to restore the pressure to the atmospheric pressure level;

[0058] The breathing valve leakage detection comprises the following specific steps:

[0059] C1 Preparation before experiment:

[0060] Same as a1;

[0061] C2 leakage detection:

[0062] The PLC controls the dual-purpose air pump to make the pressure in the air tank 85% of the opening pressure, and then closes the ball valve and leaves it for 1 minute; the temperature sensor and the pressure sensor start to record the corresponding data in the air tank and transmit them to the PLC connected to it; the PLC calculates the leakage amount of the breathing valve to be tested through the processing of the leakage amount algorithm, and can judge whether the leakage amount of the breathing valve 6 to be tested is qualified;

[0063] c3 Post-test operation:

[0064] Open the solenoid valve to restore the pressure to atmospheric pressure level.

[0065] The advantages and effects of the present invention are as follows:

[0066] 1. The present invention adopts flange connection equipment and the breathing valve to be tested, which not only expands the detection range of the equipment to DN50-DN350, but also improves the sealing performance compared with traditional equipment.

[0067] 2. The present invention adopts a dual-purpose air pump for whipping and beating, which greatly reduces the space and weight of the equipment, making the detection equipment portable.

[0068] 3. The present invention connects the air pump and the sensor directly to a small air tank, thereby reducing the volume of the entire device. The air tank of the present invention adopts a rectangular parallelepiped structure, and its size is 600mm×200mm×350mm, which greatly reduces the space occupied by the air tank of the traditional equipment.

[0069] 4. The present invention combines fluid finite element simulation to simulate the motion state of the valve core when the breathing valve is tested. According to the simulation results, the valve core of the breathing valve will not open directly axially when being tested, but will first generate a certain amount of inclination, thereby improving the accuracy of the test results.

[0070] 5. In order to solve the problem of few detection types of traditional breathing valves, the present invention establishes a theoretical simplified model of the breathing valve, and establishes a mathematical model of the breathing valve through the gas state equation, motion equation, and flow equation, wherein the parameters include the spring elastic coefficient of the breathing valve, the friction resistance of the valve stem, the upstream pressure of the breathing valve, etc. By comparing the pressure curve generated by the mathematical model with the pressure curve collected by the equipment, the spring failure, opening pressure failure, valve stem failure due to excessive friction, and excessive leakage failure of the breathing valve can be detected. In addition, since the detection of the present invention only requires fewer components to complete the detection, it also increases the portability of the detection equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 This is a solid domain mesh model diagram of the present invention;

[0072] Figure 2 This is a fluid domain grid model diagram of the present invention;

[0073] Figure 3 This is a diagram showing the overall deformation of the valve core of the present invention;

[0074] Figure 4 This is a diagram showing the change of valve core displacement over time in the present invention;

[0075] Figure 5 This is a schematic diagram of the theoretical model of the breathing valve of the present invention;

[0076] Figure 6 It is a schematic structural diagram of the portable online detection device for breathing valve of the present invention.

[0077] Figure 6 Among them, 1- whipping dual-purpose air pump, 2- one-way valve, 3- temperature sensor, 4- pressure sensor, 5- small air storage tank, 6- safety valve to be tested, 7- solenoid valve. DETAILED DESCRIPTION

[0078] Example

[0079] like Figure 6As shown, a portable breathing valve online detection device, a small air tank is connected to a dual-purpose air pump, a solenoid valve and a controller respectively, a one-way valve is arranged between the dual-purpose air pump and the small air tank; a temperature sensor and a pressure sensor are arranged between the small air tank and the controller.

[0080] The small gas storage tank is connected to the breathing valve to be tested by a flange.

[0081] In the controller, a mathematical model is established when the breathing valve core produces an inclination angle, and the mathematical model is as follows:

[0082]

[0083]

[0084] Where: x is the effective cutoff length m; b is the critical pressure ratio b = 0.2 ~ 0.5; σ is the pressure ratio; P in is the upstream pressure Pa; P out is the downstream pressure Pa;

[0085]

[0086] Where: sb is the solid-phase friction coefficient of the elbow, λ sb =2.2;ξ b is the local resistance coefficient of airflow through the elbow:

[0087]

[0088] Where: D is the pipe diameter m; R is the radius corresponding to the curved arc of the pipe centerline; θ is the central angle of the curved arc of the pipe centerline °;

[0089]

[0090] Where: a is the air flow density kg / m3; P 0 is the standard atmospheric pressure pa; T is the actual temperature K

[0091]

[0092] Where: μ a is the air flow velocity in m / s.

[0093] Q max2 =CQ max (7)

[0094] Where: Q max2 is the air pump flow rate; C is the circumference of the valve disc.

[0095] In the controller, a theoretical simplified model of the breathing valve is established, and a mathematical model of the breathing valve is established through the gas state equation, motion equation, and flow equation.

[0096] According to Newton's second law, the motion equation of the breathing valve is established;

[0097]

[0098] Where: P(t) is the change of the pressure in the tank with time pa / s, A is the area of ​​the valve core affected by the pressure in the tank m2, k is the spring coefficient N / m, x(t) is the change of the breathing valve opening with time m, M is the mass of the valve core kg, F is f Resistance N caused by valve stem rust, μ viscous resistance coefficient;

[0099] As the gas is an ideal gas and satisfies the ideal gas state equation, the state equation of the gas in the tank is:

[0100] PV=mRT(9)

[0101] Based on the fact that the volume of the gas tank does not change, the internal air mass changes with the internal pressure, and the gas temperature does not change when the gas is discharged. At this time, the pressure and gas mass change with time. The derivative of equation (9) is:

[0102] P(t)V=m(t)RT(10)

[0103] The mass of the gas in the tank can be calculated by subtracting the mass discharged when the breathing valve is working from the initial mass of the gas in the tank:

[0104]

[0105] Where: V is the volume of the gas storage tank m3, m(t) is the amount of change of the gas mass in the tank over time kg / s, R is the gas constant J / (mol·k), T is the temperature in the tank k, m 0 is the initial mass of the gas in the tank kg, ρ is the gas density at normal temperature and pressure kg / m3, Q(t) is the change of flow rate over time m3 / t2;

[0106] The flow equation is,

[0107]

[0108] Where: C is the outer circumference of the valve disc m, b is the critical pressure ratio b = 0.2 ~ 0.5, σ is the pressure ratio, P in is the upstream pressure Pa, P out is the downstream pressure Pa;

[0109] Leakage detection formula

[0110]

[0111] That is, the leakage per unit time ΔV is as shown in formula (9):

[0112]

[0113] Where: V is the volume of the gas tank, n is 1 The amount of gas in the gas tank at state 1, n 2 The amount of gas in the gas tank at state 2, R is the molar gas constant, T is the temperature of the gas tank, p 1 The pressure in the gas tank at state 1, p 2 The pressure in the gas tank in state 2.

[0114] Combining (9)(10)(11)(12)(13), it is found that when the breathing valve spring fails, the opening pressure fails, and the valve stem friction is too large, it will affect the amplitude and frequency of the pressure curve. When the breathing valve spring coefficient decreases, the frequency of its pressure curve will decrease. When the valve stem friction is too large, the amplitude of its pressure curve will decrease.

[0115] By comparing the normal pressure curve simulated by the mathematical model and the amplitude and frequency of the pressure curve collected by the pressure sensor, different failure modes of the breathing valve can be judged. When the amplitude of the pressure curve collected by the pressure sensor is lower than the amplitude of the pressure curve in the mathematical model, it can be judged that the valve stem friction of the breathing valve to be tested is too large; when the frequency of the pressure curve collected by the pressure sensor is lower than the frequency of the pressure curve in the mathematical model, it can be judged that the spring of the breathing valve to be tested has failed.

[0116] A portable breathing valve online detection method, including breathing valve pressure monitoring, valve stem displacement detection and breathing valve leakage detection;

[0117] The breathing valve pressure detection comprises the following specific steps:

[0118] A1 Preparation before testing:

[0119] Input the parameters of the breathing valve to be tested into the controller, calculate the air pump flow required for this test through the controller, and adjust the air pump flow to the required range after obtaining the data;

[0120] a2 turns on pressure detection:

[0121] The breathing valve 6 to be tested is connected to the small gas tank 5, the one-way valve 2 is opened to allow the whipping dual-purpose air pump 1 to communicate with the small gas tank 5, the whipping dual-purpose air pump 1 is turned on, and the temperature sensor 3 and the pressure sensor 4 begin to record the corresponding data in the gas tank 5 and transmit them to the PLC connected thereto; when the breathing valve to be tested is opened for a period of time due to the change of the gas pressure in the small gas tank 5 until the pressure in the tank is stable, the PLC controls the whipping dual-purpose air pump 1 to restore the pressure of the gas tank 5 to the initial level, and then the PLC continues to control the whipping dual-purpose air pump 1 to open the breathing valve 6 to be tested, and this is repeated until the breathing valve 6 to be tested is opened four times; by observing the pressure curve in the PLC, when the pressure curve after the breathing valve is opened oscillates around the normal opening pressure line periodically, it can be judged that the opening pressure of the breathing valve is normal; when the pressure curve after the breathing valve is opened oscillates around a pressure line lower than or higher than the normal opening pressure line periodically, it can be judged that the opening pressure of the breathing valve is abnormal;

[0122] a3 Post-test operation:

[0123] Turn off the whipping and beating dual-purpose air pump 1, open the solenoid valve 7, and restore the pressure to the atmospheric pressure level;

[0124] The breathing valve stem displacement detection comprises the following specific steps:

[0125] b1 Preparation before experiment:

[0126] After completing the pre-test preparation a1 of the opening pressure test, the parameters of the breathing valve 6 to be tested are input into the controller, and the controller calculates the normal pressure curve of the breathing valve to be tested when it is normal;

[0127] b2 valve stem displacement detection:

[0128] The breathing valve 6 to be tested is connected to the small gas tank 5, the one-way valve 2 is opened to make the whipping dual-purpose air pump 1 communicate with the small gas tank 5, the whipping dual-purpose air pump 1 is turned on, and the temperature sensor 3 and the pressure sensor 4 begin to record the corresponding data in the gas tank 5 and transmit them to the PLC connected thereto; when the breathing valve to be tested is opened for a period of time due to the change of the gas pressure in the small gas tank 5, the PLC controls the whipping dual-purpose air pump 1 to restore the pressure of the gas tank 5 to the initial level, and then the PLC continues to control the whipping dual-purpose air pump 1 to open the breathing valve 6 to be tested, and this is repeated until the safety valve 6 to be tested is opened four times; by comparing the pressure curve generated by the PLC in the preparation b1 before the experiment with the pressure curve recorded by the pressure sensor 4 in the valve stem displacement detection b2, when the amplitude of the curve in b2 is less than the amplitude in b1, it is judged that the valve stem friction of the breathing valve 6 to be tested is too large; when the frequency of the curve in b2 is less than the frequency of the curve in b1, it is judged that the spring coefficient of the breathing valve 6 to be tested is too small;

[0129] b3 Post-test operation:

[0130] Turn off the whipping and beating dual-purpose air pump 1, open the solenoid valve 7, and restore the pressure to the atmospheric pressure level;

[0131] The breathing valve leakage detection comprises the following specific steps:

[0132] C1 Preparation before experiment:

[0133] Same as a1;

[0134] C2 leakage detection:

[0135] The PLC controls the dual-purpose air pump 1 to make the pressure in the small air tank 5 85% of the opening pressure, and then closes the ball valve 2 and leaves it to stand for 1 minute; the temperature sensor 3 and the pressure sensor 4 start to record the corresponding data in the small air tank 5 and transmit it to the PLC connected thereto; the PLC can calculate the leakage amount of the breathing valve 6 to be tested by processing the leakage amount algorithm, and can judge whether the leakage amount of the breathing valve 6 to be tested is qualified;

[0136] c3 Post-test operation:

[0137] Open the solenoid valve 7 to restore the pressure to the atmospheric pressure level.

[0138] The flow process of the gas in the tank when the breathing valve is working is complicated. To facilitate the establishment of the model, the following assumptions are made:

[0139] 1. The gas is an ideal gas and satisfies the ideal gas state equation.

[0140] 2. The volume of the gas tank does not change, the internal air quality changes with the internal pressure, and the gas temperature does not change when the gas is discharged.

[0141] 3. Gas temperature and density are evenly distributed everywhere.

[0142] The small gas storage tank described in the present application adopts a rectangular parallelepiped structure, and its size is 600mm×200mm×350mm.

[0143] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A portable breathing valve online detection device, characterized in that: The gas storage tank is respectively connected to the whipping dual-purpose air pump, the electromagnetic valve and the controller, a one-way valve is arranged between the whipping dual-purpose air pump and the gas storage tank; a temperature sensor and a pressure sensor are arranged between the gas storage tank and the controller.

2. A portable breathing valve online detection device according to claim 1, characterized in that: The gas storage tank is connected to the breathing valve to be tested by a flange.

3. A portable breathing valve online detection device according to claim 1, characterized in that: The gas storage tank adopts a rectangular parallelepiped structure, and its size is 600mm×200mm×350mm.

4. A portable breathing valve online detection device according to claim 1, characterized in that: In the controller, a mathematical model is established when the breathing valve core produces an inclination angle, and the mathematical model is as follows: Where: x is the effective cutoff length m; b is the critical pressure ratio b = 0.2 ~ 0.5; σ is the pressure ratio; P in is the upstream pressure Pa; P out is the downstream pressure Pa; Where: sb is the solid-phase friction coefficient of the elbow, λ sb =2.2;ξ b is the local resistance coefficient of airflow through the elbow: Where: D is the pipe diameter m; R is the radius corresponding to the curved arc of the pipe centerline; θ is the central angle corresponding to the curved arc of the pipe centerline; Where: a is the air flow density kg / m3; P0 is the standard atmospheric pressure pa; T is the actual temperature K Where: μ a is the air flow velocity m / s; Q max2 =CQ max (7) Where: Q max2 is the air pump flow rate; C is the circumference of the valve disc.

5. A portable breathing valve online detection device according to claim 4, characterized in that: In the controller, a theoretical simplified model of the breathing valve is established, and a mathematical model of the breathing valve is established through the gas state equation, motion equation, and flow equation. According to Newton's second law, the motion equation of the breathing valve is established; Where: P(t) is the change of the pressure in the tank with time pa / s, A is the area of ​​the valve core affected by the pressure in the tank m2, k is the spring coefficient N / m, x(t) is the change of the breathing valve opening with time m, M is the mass of the valve core kg, F is f Resistance N caused by valve stem rust, μ viscous resistance coefficient; As the gas is an ideal gas and satisfies the ideal gas state equation, the state equation of the gas in the tank is: PV=mRT (9) Based on the fact that the volume of the gas tank does not change, the internal air mass changes with the internal pressure, and the gas temperature does not change when the gas is discharged. At this time, the pressure and gas mass change with time. The derivative of equation (9) is: P(t)V=m(t)RT (10) The mass of the gas in the tank can be obtained by subtracting the mass of the gas discharged when the breathing valve works from the initial mass of the gas in the tank: Where: V is the volume of the gas storage tank m3, m(t) is the amount of change of the gas mass in the tank with time kg / s, R is the gas constant J / (mol·k), T is the temperature in the tank k, m0 is the initial mass of the gas in the tank kg, ρ is the gas density at normal temperature and pressure kg / m3, Q(t) is the change of the flow rate with time m3 / t2; The flow equation is, Where: C is the outer circumference of the valve disc m, b is the critical pressure ratio b = 0.2 ~ 0.5, σ is the pressure ratio, P in is the upstream pressure Pa, P out is the downstream pressure Pa; Leakage detection formula That is, the leakage per unit time ΔV is as shown in formula (9): In the formula: V is the gas storage volume, n1 is the amount of gas substance in the pressure tank at state 1, n2 is the amount of gas substance in the gas tank at state 2, R is the molar gas constant, T is the temperature of the gas tank, p1 is the pressure in the gas tank at state 1, and p2 is the pressure in the gas tank at state 2.

6. The detection method of a portable breathing valve online detection device according to claim 1 is characterized in that: Including breathing valve pressure monitoring, valve stem displacement detection and breathing valve leakage detection; The breathing valve pressure detection comprises the following specific steps: A1 Preparation before testing: Input the parameters of the breathing valve to be tested into the controller, calculate the air pump flow required for this test through the controller, and adjust the air pump flow to the required range after obtaining the data; a2 turns on pressure detection: Connect the breathing valve to be tested to the gas tank, open the one-way valve to allow the whipping dual-purpose air pump to communicate with the gas tank, turn on the whipping dual-purpose air pump, and the temperature sensor and pressure sensor begin to record the corresponding data in the gas tank and transmit them to the PLC connected to it; when the breathing valve to be tested is opened for a period of time due to the change of gas pressure in the gas tank until the pressure in the tank is stable, the PLC controls the whipping dual-purpose air pump to restore the pressure of the gas tank to the initial level, and then the PLC continues to control the whipping dual-purpose air pump to open the breathing valve to be tested, and repeat this process until the breathing valve to be tested is opened four times; by observing the pressure curve in the PLC, when the pressure curve after the breathing valve is opened oscillates around the normal opening pressure line periodically, it can be judged that the opening pressure of the breathing valve is normal; when the pressure curve after the breathing valve is opened oscillates around a pressure line lower than or higher than the normal opening pressure line periodically, it can be judged that the opening pressure of the breathing valve is abnormal; a3 Post-test operation: Turn off the dual-purpose air pump and open the solenoid valve to restore the pressure to the atmospheric pressure level; The breathing valve stem displacement detection comprises the following specific steps: b1 Preparation before experiment: After completing the pre-test preparation a1 of the opening pressure test, the parameters of the breathing valve to be tested are input into the controller, and the controller calculates the normal pressure curve of the breathing valve to be tested when it is normal; b2 valve stem displacement detection: Connect the breathing valve to be tested to the gas tank, open the one-way valve to allow the whipping dual-purpose air pump to communicate with the gas tank, turn on the whipping dual-purpose air pump, and the temperature sensor and pressure sensor begin to record the corresponding data in the gas tank and transmit them to the PLC connected thereto; when the breathing valve to be tested is opened for a period of time due to the change in the gas pressure in the gas tank, the PLC controls the whipping dual-purpose air pump to restore the pressure of the gas tank to the initial level, and then the PLC continues to control the whipping dual-purpose air pump to open the breathing valve to be tested, and repeat this process until the safety valve to be tested is opened four times; by comparing the pressure curve generated by the PLC in preparation b1 before the experiment with the pressure curve recorded by the pressure sensor in the valve stem displacement detection b2, when the amplitude of the curve in b2 is less than the amplitude in b1, it is judged that the valve stem friction of the breathing valve to be tested is too large; when the frequency of the curve in b2 is less than the frequency of the curve in b1, it is judged that the spring coefficient of the breathing valve to be tested is too small; b3 Post-test operation: Turn off the dual-purpose air pump and open the solenoid valve to restore the pressure to the atmospheric pressure level; The breathing valve leakage detection comprises the following specific steps: C1 Preparation before experiment: Same as a1; C2 leakage detection: The PLC controls the dual-purpose air pump to make the pressure in the air tank 85% of the opening pressure, and then closes the ball valve and leaves it alone for 1 minute; the temperature sensor and pressure sensor start recording the corresponding data in the air tank and transmit it to the PLC connected to it; the PLC calculates the leakage amount of the breathing valve to be tested through the leakage amount algorithm, and can judge whether the leakage amount of the breathing valve to be tested is qualified; c3 Post-test operation: Open the solenoid valve to restore the pressure to atmospheric pressure level.

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