A pneumatic valve flow and pressure stabilization control device

Abstract

This invention relates to a pneumatic valve flow and pressure stabilization control device. The control device includes a DCS main controller, a signal distributor, a comparison storage trigger control device, a current signal measuring point, a valve positioner, a two-position three-way electrically controlled directional valve, a pneumatic amplifier, a pneumatic valve cylinder, a plant compressed air source, and a pressure stabilization control unit. The DCS main controller outputs a control command current signal connected to the input terminal of the signal distributor. The signal distributor outputs corresponding current signals in two paths to the comparison storage trigger control device. One path is sent to its internal relay trigger circuit, and the other path is sent to its internal comparison storage trigger circuit. The output signal of the comparison storage trigger control device is directly connected to the signal receiving terminal of the valve positioner. A valve positioner control current signal measuring point is connected in series in the control cable. The comparison storage trigger circuit controls the interruption of abnormal signals and stabilizes the normal control current signal to maintain the valve position.

Description

Technical Field

[0001] This invention relates to a control device, specifically a pneumatic valve flow and pressure stabilization control device, belonging to the field of electrical instrumentation control technology. Background Technology

[0002] Currently, pneumatically controlled regulating valves or shut-off valves are widely used in continuous production processes due to their significant advantages. Pneumatic control results in fast valve response, simple control components, ease of maintenance, and convenient troubleshooting. However, in practical applications, valve control component failures have led to production accidents, severely impacting normal production. For example, at Meigang Thermal Power Plant, a fault occurred in the pneumatic anti-surge regulating valve of the No. 7 blast furnace blower, where a fault in the control command current signal and control cable caused the valve positioner to receive incorrect command signals, resulting in valve position drift. Another fault occurred where a valve positioner failure directly caused erroneous and disordered output air pressure signals to enter the valve cylinder, leading to malfunctioning valve operation. These faults have seriously affected blast furnace production. Therefore, it is essential to invent a pneumatic valve flow stabilization and pressure stabilization control device and method to address the issues of control command current signal failures and valve positioner failures causing malfunctioning valve operation. This method aims to maintain valve position stability and provide compensatory control after control command signal or positioner failures, ensuring stable production operation. Summary of the Invention

[0003] This invention addresses the problems existing in the prior art by providing a pneumatic valve flow and pressure stabilization control device. This technical solution achieves the goal of preventing large-scale drifting or accidents such as full opening or full closing of the pneumatic valve during continuous production processes by controlling the fault comparison and storage of the current signal to trigger self-cutting function and the fault air pressure compensation control function of the valve positioner. This ensures stable and smooth production to a certain extent.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows: a pneumatic valve flow and pressure stabilization control device, characterized in that the control device includes a DCS main controller, a signal distributor, a comparison storage trigger control device, a current signal measuring point, a valve positioner, a two-position three-way electrically controlled directional valve, a pneumatic amplifier, a pneumatic valve cylinder, a plant compressed air source, and a pressure stabilization control unit; the DCS main controller outputs a control command current signal connected to the input terminal of the signal distributor, and the signal distributor outputs corresponding current signals in two paths to the comparison storage trigger control device, one path of which is sent to its internal relay trigger circuit, and the other... The signal is sent to its internal comparison and storage trigger circuit. The output signal of the comparison and storage trigger control device is directly connected to the signal receiving end of the valve positioner. A valve positioner control current signal measuring point is connected in series in the control cable. The air pressure input end of the valve positioner accepts the plant's compressed air source as the working air source. The air pressure output end of the valve positioner is connected to the input end 1 of the two-position three-way solenoid valve. Its output end 2 is connected to the air circuit amplifier. The output end of the air circuit amplifier is directly connected to the pneumatic valve cylinder. The control coil S of the two-position three-way solenoid valve is connected to the circuit output of the voltage stabilizing control device through the control cable.

[0005] As an improvement of the present invention, the control device includes an external current signal generator, which is disposed between the DCS main controller and the comparison storage trigger control device. The external current signal generator and the comparison storage trigger control device are connected via a control signal cable, allowing the external current signal generator to directly control the valve positioner through switching via the internal switching circuit of the comparison storage trigger control device. The DCS main controller and the external current signal generator are connected via a power cable, requiring a continuous supply of 24VDC drive power to the external current signal generator.

[0006] As an improvement of the present invention, the pressure stabilizing control unit includes a compensating pressure measuring point, a pressure regulating valve, and a pressure stabilizing control device. The second output of the plant compressed air is connected to the working air source interface of the pressure stabilizing control device via a pipeline. The DCS main control output power supply is connected to the working power supply interface of the pressure stabilizing control device via a cable. The valve positioner control current signal measuring point A and the valve positioner output air pressure measuring point P are respectively connected to the signal input terminal of the pressure stabilizing control device via cables. The first circuit output terminal of the pressure stabilizing control device is connected to the control coil S of the two-position three-way electrically controlled directional valve via a control cable. The air path output terminal of the pressure stabilizing control device is connected to the bypass interface 3 of the two-position three-way pneumatic control valve via a pipeline. A pressure regulating valve and a post-valve compensating pressure measuring point are installed in the connecting pipeline. The second circuit output of the pressure stabilizing control device is connected to the control terminal of the pressure regulating valve via a control cable. The post-valve compensating pressure measuring point is sent to the pressure stabilizing control device as a feedback signal via a cable.

[0007] As an improvement of the present invention, a pressure measuring point is added to the air pressure output pipeline of the valve positioner.

[0008] As an improvement of this invention, a comparison-store trigger control device is used to achieve the function of self-switching and position-holding manual control in the field after a fault in the pneumatic valve control command current signal. Specifically, the DCS control command current signal is input to the signal distributor through a control cable. The signal distributor outputs the command signal in two paths without disturbance to the comparison-store trigger control device. One path goes to its internal relay trigger circuit, and the other path goes to its internal comparison-store trigger circuit. When the pneumatic valve is under normal control, the DCS control command current signal is output through one path of the signal distributor to the normally closed contact in the relay trigger circuit of the comparison-store trigger control device, and then directly output to the signal receiving end of the valve positioner through the cable to realize normal current command control of the valve. When a fault occurs in the DCS control command or cable, resulting in an abnormal signal, the comparison-store trigger circuit inside the device immediately determines that the main control signal is abnormal by comparing it with the real-time DCS current signal. Fault conditions include open circuit, short circuit, and current signal abnormality in the control cable. If a fault occurs within 5% of the DCS set step value, meaning a command fault occurs when the DCS main control is not operating, the comparison-store trigger control device will store the second-channel control command signal in real time. If the command current signal changes abruptly or significantly, it will immediately start working. First, through relay switching, the fault control command is cut off, and the stored signal before the fault is sent to the valve positioner in real time. At this time, the normally closed contact in the relay trigger circuit becomes normally open, cutting off the fault signal; the normally open contact becomes normally closed, connecting the stored signal, achieving a smooth switching. This stabilizes the valve positioner's control command current signal at the output value before the fault, maintaining the valve position at the position before the control signal fault. Simultaneously, through the switching circuit of the comparison-store trigger control device, the output cable connector of the external current signal generator is automatically switched to the relay circuit. The normally closed contact of the relay circuit directly controls the valve positioner to receive the manually adjusted current signal output from the external current signal generator on-site. Ultimately, this achieves the goal of manually controlling the valve action directly on-site using the external current signal generator. Simultaneously, by comparing and storing the switching circuit within the control device, the external current signal generator allows for manual control of the valve operation on-site, ensuring continuous and uninterrupted production.

[0009] As an improvement of the present invention, the control process of the pressure stabilizing control unit is as follows: The pressure stabilizing control device receives power from the DCS main control unit, receives compressed air from the plant as its working air source, and simultaneously receives the input current signal and the output air pressure signal of the valve positioner as comparison trigger signal sources. A pressure regulating valve is installed on the air output pipeline of the pressure stabilizing control device. The pressure measurement point signal after the pressure regulating valve is used as a feedback signal to enter the pressure stabilizing control device. Its air pressure pipeline output is finally connected to the bypass port 3 of the two-position three-way electrically controlled directional valve. Its first circuit control output cable is connected to the coil of the two-position three-way electrically controlled directional valve, and its second circuit control output cable is directly connected to the pressure regulating valve control component. During normal operation of the pneumatic control valve, the valve positioner receives the main control command signal and, through the electro-pneumatic conversion function, outputs a certain air pressure through the input port 1 and output port 2 of the two-position three-way electrically controlled directional valve into the air amplifier for pressure amplification. Then, the valve cylinder drives the valve to operate normally. When the control command current signal remains unchanged and the positioner output air pressure is abnormal (i.e., the output air pressure signal deviates from the corresponding value of the control current by 5%), the valve positioner is judged to be faulty. The pressure stabilizing control device receives the valve positioner control current signal measurement point A and the valve positioning output air pressure measurement point P as input comparison signals. When A remains unchanged and P deviates from the normal corresponding value by 5%, the valve positioner is judged to be faulty. The pressure stabilizing control device immediately drives the control coil S of the two-position three-way solenoid valve to be energized. At this time, the pneumatic valve input port 1 and output port 2 are not connected, and the output port 2 and bypass port 3 are connected. At the same time, the compensation air pressure output regulation circuit works. Through the closed-loop control of the pressure regulating valve and the downstream pressure, the control output compensation air pressure is sent to the bypass port 3 of the two-position three-way solenoid valve at the corresponding air pressure value ΔP before the fault. The entry of compensation air pressure ΔP is used to maintain the normal opening control of the valve before the fault.

[0010] Compared with the prior art, the present invention has the following advantages: 1) The technical solution designs a comparison storage trigger control device, which triggers the relay circuit to operate after comparing the signal deviation, and simultaneously stores the normal control signal in real time, realizing the seamless switching of the fault control signal, so that the normal control signal continuously enters the valve positioner through the relay circuit to control the valve operation; 2) The solution adds an external current signal generator. After the main control signal fails, when production needs to continue controlling the valve opening, the external control signal can be switched in through the switching circuit to continue controlling the valve operation and maintain production. It can realize on-site manual intervention to maintain stable production by controlling the valve normally; 3) The solution designs a pressure stabilizing control device. When the valve positioner fails and the output air pressure is disordered, it can immediately determine and trigger the cut-off of the faulty air pressure output air path, and at the same time open the technically compensated normal air pressure output to the valve cylinder to maintain the normal operation of the valve; through pressure stabilizing compensation output control, the normal valve position holding function after the valve positioner fails can be realized, which can further maintain the stable control of the valve; 4) The abnormal signal is interrupted by the comparison storage trigger circuit, and the normal control current signal is stabilized to keep the valve position unchanged. Attached Figure Description

[0011] Figure 1 A schematic diagram of the on-site layout of a pneumatic valve pressure and flow stabilization control device;

[0012] Figure 2 This is a schematic diagram of a comparison storage trigger control device.

[0013] In the diagram: 1. DCS main controller, 2. Signal distributor, 3. Comparison, storage, trigger control device, 4. Current signal measuring point, 5. External current signal generator, 6. Valve positioner, 7. Air pressure measuring point, 8. Two-position three-way electrically controlled directional valve, 9. Air circuit amplifier, 10. Pneumatic valve cylinder, 11. Compensating pressure measuring point, 12. Pressure regulating valve, 13. Pressure stabilizing control device, 14. Plant compressed air source. Detailed implementation method:

[0014] To enhance understanding of the present invention, the embodiments will be described in detail below with reference to the accompanying drawings.

[0015] Example 1: See Figure 1 , Figure 2A pneumatic valve flow and pressure stabilization control device is disclosed. The control device includes a DCS main controller 1, a signal distributor 2, a comparison, storage, and trigger control device 3, a current signal measuring point 4, a valve positioner 6, a two-position three-way electrically controlled directional valve 8, a pneumatic amplifier 9, a pneumatic valve cylinder 10, a plant compressed air source 14, and a pressure stabilization control unit. The DCS main controller 1 outputs a control command current signal connected to the input terminal of the signal distributor 2. The signal distributor 2 outputs corresponding current signals in two paths to the comparison, storage, and trigger control device 3. One path is sent to its internal relay trigger circuit, and the other path is sent to its internal comparison, storage, and trigger circuit. The output signal of the comparison, storage, and trigger control device 3 is directly connected to the signal receiving terminal of the valve positioner 6. The valve positioner control current signal measuring point 4 is connected in series with the control cable. The air pressure input terminal of the valve positioner 6 receives the plant compressed air source 14 as a pressure input. The working air source connects the air pressure output terminal of the valve positioner 6 to the input terminal 1 of the two-position three-way electrically controlled directional valve 8, and its output terminal 2 is connected to the air circuit amplifier 9. The output terminal of the air circuit amplifier 9 is directly connected to the pneumatic valve cylinder 10. The control coil S of the two-position three-way electrically controlled directional valve 8 is connected to the circuit output of the voltage stabilizing control device 13 through a control cable. The control device includes an external current signal generator 5, which is located between the DCS main controller 1 and the comparison storage trigger control device 3. The external current signal generator is connected to the DCS main controller through a power cable and receives the drive power output from the DCS main controller. The comparison storage trigger control device is connected to the external current signal generator through a control signal cable. By switching the external current signal generator through a switching circuit, the control signal output by the external current signal generator can be directly input to the valve positioner, realizing manual control of the valve action on site. The pressure stabilizing control unit includes a compensating pressure measuring point 11, a pressure regulating valve 12, and a pressure stabilizing control device 13. The second output of the plant compressed air is connected to the working air source interface of the pressure stabilizing control device 13 via a pipeline. The output power of the DCS main control 1 is connected to the working power interface of the pressure stabilizing control device 13 via a cable. The control current signal measuring point A of the valve positioner 6 and the output air pressure measuring point P of the valve positioner are respectively connected to the signal input terminal of the pressure stabilizing control device 13 via cables. The first circuit output terminal of the pressure stabilizing control device 13 is connected to a two-position three-way electric controller. The control coil S of the reversing valve 8 is connected via a control cable. The pneumatic output of the pressure stabilizing control device 13 is connected to the bypass interface 3 of the two-position three-way pneumatic control valve 8 via a pipeline. A pressure regulating valve 12 and a downstream compensating pressure measuring point 11 are installed in the connecting pipeline. The second circuit output of the pressure stabilizing control device 13 is connected to the control terminal of the pressure regulating valve 12 via a control cable. The downstream compensating pressure measuring point 11 is sent to the pressure stabilizing control device 13 as a feedback signal via a cable. A pneumatic measuring point 7 is installed in the pneumatic output pipeline of the valve positioner 6.

[0016] Figure 2 To compare the schematic diagram of the storage trigger control device, such as Figure 2 As shown, the DCS control command current signal is input to the signal distributor via a control cable. The signal distributor splits the command signal into two paths and outputs them to the comparison storage trigger control device. One path goes to its internal relay trigger circuit, and the other goes to its internal comparison trigger circuit. One path of the DCS control command current signal is output from the signal distributor to the normally closed contact in the relay trigger circuit of the comparison storage trigger control device, and then directly outputs to the signal receiving end of the valve positioner via a cable, realizing normal current command control of the valve. When a fault occurs in the DCS control command or cable, causing an abnormal signal, the comparison trigger circuit inside the comparison storage trigger device immediately determines that the main control signal is abnormal by comparing it with the real-time DCS current signal. The comparison storage trigger control device stores the second input control command signal in real time. If the command current signal changes abruptly or significantly, it immediately starts working. First, the relay coil K is energized to switch and cut off the fault control command, and then the stored signal before the fault is sent to the valve positioner in real time. At this time, the normally closed contact in the relay trigger circuit becomes normally open, cutting off the fault signal; the normally open contact becomes normally closed, connecting the stored signal, achieving a smooth switching. This stabilizes the valve positioner's control command current signal at its pre-fault output value, maintaining the valve position at the level before the control signal failure. Simultaneously, a switching circuit automatically connects the output cable of the external current signal generator to the relay circuit, allowing direct control of the valve positioner via normally closed contacts. This enables manual valve control from the external current signal generator in the field, ensuring uninterrupted production.

[0017] Working principle and implementation steps of the comparison-store trigger control device: In the event of a command fault occurring when the DCS main control is not operating, the comparison-store trigger control device sends the first output command signal from the signal distributor directly to the valve positioning signal receiver via the normally closed contact in the internal relay trigger circuit for real-time valve control. Simultaneously, the second command signal from the signal distributor is connected to the internal comparison-store trigger circuit, initially used as a storage signal at the circuit input as a reference signal. When the command current signal undergoes a sudden change, a large fluctuation, short circuit, or open circuit, the comparison-store trigger control device immediately triggers and starts working by comparing it with the reference control signal: The relay trigger circuit switches, cutting off the normal control command signal line and sending the pre-fault stored signal to the valve positioner in real time. The trigger circuit output controls relay K; the normally closed contact in the relay trigger circuit becomes normally open, cutting off the faulty control line; the normally open contact becomes normally closed, connecting the normal stored control signal. This achieves a smooth switching, stabilizing the valve control command current signal at the pre-fault output value. A further advantage is that an external current signal generator is added to the comparison trigger storage circuit. If the pneumatic valve fails, the system still needs to control the valve opening in real time. In this case, the switching circuit in the comparison trigger storage circuit will start working. Through the switching switch in the signal generator, the signal cable of the signal generator can be switched with the stored signal cable after the fault switch, and the control cable of the signal generator can be switched to the control loop of the valve positioner signal receiver. The normal operation of the pneumatic valve can be controlled in real time by manually adjusting the current on site.

[0018] Working principle and specific implementation steps of the pressure stabilizing control device: The pressure stabilizing control device receives power from the DCS main control and uses compressed air from the plant as its working air source. It also receives the input current signal and output air pressure signal from the valve positioner as comparison trigger signals. A pressure regulating valve is installed on the air output pipeline of the pressure stabilizing control device, and the pressure measurement signal after the pressure regulating valve is used as a feedback signal to enter the pressure stabilizing control device. Its air pressure pipeline output is ultimately connected to the bypass port 3 of the two-position three-way electrically controlled directional valve. Its first circuit control output cable is connected to the coil of the two-position three-way electrically controlled directional valve. Its second circuit control output cable is directly connected to the pressure regulating valve control component. During normal operation of the pneumatically controlled valve, the valve positioner receives the main control command signal and, through the electro-pneumatic conversion function, outputs a certain air pressure. This pressure enters the air amplifier through the input port 1 and output port 2 of the two-position three-way electrically controlled directional valve, where it is amplified before entering the valve cylinder to drive the valve to operate normally. When a fault occurs where the control command current signal remains unchanged but the positioner output air pressure is abnormal (i.e., the output air pressure signal deviates from the corresponding value of the control current by 5%), the valve positioner is judged to be faulty. Specifically, the pressure stabilizing control device receives the valve positioner control current signal measurement point A and the valve positioning output air pressure measurement point P as input comparison signals. When A remains unchanged and P deviates from the normal corresponding value by 5%, the valve positioner is judged to be faulty. The pressure stabilizing control device immediately drives the control coil S of the two-position three-way electrically controlled directional valve to energize. At this time, the pneumatic valve input port 1 and output port 2 are disconnected, while output port 2 and bypass port 3 are connected. Simultaneously, the compensating air pressure output regulation circuit operates. Through the closed-loop control of the pressure regulating valve and the downstream pressure, the output compensating air pressure is controlled to be the corresponding air pressure value ΔP before the fault, and sent to the bypass port 3 of the two-position three-way electrically controlled directional valve. The input of the compensating air pressure ΔP maintains the normal valve opening control before the fault.

[0019] This solution, through the combined application of storage trigger control device and voltage stabilization control device, addresses the flow and pressure stabilization control method adopted after the control command signal of pneumatic control valves fails or the valve positioner fails. It fully ensures that the pneumatic valves will not drift significantly or cause accidents such as being fully open or fully closed in continuous production processes, thus guaranteeing stable and smooth production to a certain extent.

[0020] Work process: Refer to Figure 1 — Figure 2This solution utilizes a comparison-store trigger control device to achieve self-switching and position-holding manual control of pneumatic valves in the event of a fault in the pneumatic valve control command current signal. The DCS control command current signal is input to a signal distributor via a control cable. The signal distributor outputs the command signal without disturbance to the comparison-store trigger control device via two paths: one to its internal relay trigger circuit, and the other to its internal comparison-store trigger circuit. During normal pneumatic valve control, the DCS control command current signal is output from one path of the signal distributor to the normally closed contact in the relay trigger circuit of the comparison-store trigger control device, and then directly output to the signal receiver of the valve positioner via a cable, achieving normal current command control of the valve. When a fault occurs in the DCS control command or cable, resulting in an abnormal signal, the comparison-store trigger circuit inside the device immediately determines that the main control signal is abnormal by comparing it with the real-time DCS current signal. Fault conditions include (control cable open circuit, short circuit, current signal greater than or less than 5% of the DCS set step). In the event of a command failure occurring when the DCS main control is not operating, the comparison-store trigger control device stores the second-channel control command signal in real time. If the command current signal changes abruptly or significantly, it immediately initiates operation. First, through relay switching, the fault control command is cut off, and the stored signal before the fault is sent to the valve positioner in real time. At this time, the normally closed contact in the relay trigger circuit becomes normally open, cutting off the fault signal; the normally open contact becomes normally closed, connecting the stored signal, achieving a smooth switching. This stabilizes the valve positioner's control command current signal at the output value before the fault, maintaining the valve position at the position before the control signal failure. Simultaneously, the switching circuit included within the comparison-store trigger control device allows the external current signal generator to manually control the valve action directly on-site, ensuring continuous production without interruption. This solution achieves stable valve control after a valve positioner failure through a pressure stabilization control device. The pressure stabilization control device compares the input command current signal and the output air pressure signal of the valve positioner in real time. The working principle of an electro-pneumatic valve positioner reveals that a certain input current signal (4-20mA) enters the valve positioner, controlling the magnetic coil to actuate. This, in turn, outputs a matched air pressure signal (0-100KPa) through the internal lever spring and nozzle throttling action. The input current signal and output air pressure signal of the valve positioner have a linear proportional relationship; that is, a certain current input corresponds to a certain air pressure output. When the valve positioner malfunctions, the deviation between the input current signal and the output air pressure signal exceeds the set value. In this case, the pressure stabilizing control device determines the positioner is faulty and immediately controls the two-position three-way electrically controlled directional valve via a trigger circuit to cut off the faulty air pressure output channel. Simultaneously, the calculated compensation air pressure is switched in through the bypass of the electrically controlled directional valve, seamlessly replacing the input to the normal control air circuit.

[0021] Taking a practical application as an example: If the input current of a valve positioner is 12mA, theoretically it should correspond to an output air pressure of 50Kpa. When the current is constant, if the output air pressure deviation is greater than the set value by more than 5%, the positioner is considered to have malfunctioned. The pressure stabilizing control device immediately activates, cutting off the faulty air path from the valve and immediately sending the compensated 50Kpa air pressure output through the bypass port of the two-position three-way electrically controlled directional valve to the valve control air path to maintain the normal opening of the valve.

[0022] It should be noted that the above embodiments are not intended to limit the scope of protection of the present invention. Equivalent transformations or substitutions made based on the above technical solutions all fall within the scope of protection of the claims of the present invention.

Claims

1. A pneumatic valve flow stabilizing and pressure stabilizing control device, characterized by, The control device includes a DCS main controller, a signal distributor, a comparison storage trigger control device, a current signal measuring point, a valve positioner, a two-position three-way electrically controlled directional valve, a pneumatic amplifier, a pneumatic valve cylinder, a plant compressed air source, and a pressure stabilizing control unit. The DCS main controller outputs a control command current signal connected to the input terminal of the signal distributor. The signal distributor outputs corresponding current signals in two paths to the comparison storage trigger control device. One path is sent to its internal relay trigger circuit, and the other path is sent to its internal comparison storage trigger circuit. The output signal of the comparison storage trigger control device is directly connected to the signal receiving terminal of the valve positioner. A valve positioner control current signal measuring point is connected in series with the control cable. The pneumatic input terminal of the valve positioner receives the plant compressed air source as its working air source. The pneumatic output terminal of the valve positioner is connected to the input terminal 1 of the two-position three-way electrically controlled directional valve, and its output terminal 2 is connected to the pneumatic amplifier. The output terminal of the pneumatic amplifier is directly connected to the pneumatic valve cylinder. The control coil S of the two-position three-way electrically controlled directional valve is connected to the circuit output of the pressure stabilizing control device through the control cable. The control device includes an external current signal generator, which is located between the DCS main controller and the comparison storage trigger control device. The voltage regulator control unit includes The system includes a pressure measuring point, a pressure regulating valve, and a pressure stabilizing control device. The second output of the plant's compressed air is connected to the working air source interface of the pressure stabilizing control device via a pipeline. The DCS main control output power is connected to the working power interface of the pressure stabilizing control device via a cable. The valve positioner control current signal measuring point A and the valve positioner output air pressure measuring point P are respectively connected to the signal input terminal of the pressure stabilizing control device via cables. The first circuit output terminal of the pressure stabilizing control device is connected to the control coil S of the two-position three-way electrically controlled directional valve via a control cable. The air path output terminal of the pressure stabilizing control device is connected to the bypass interface 3 of the two-position three-way pneumatic control valve via a pipeline. A pressure regulating valve and a downstream pressure measuring point are installed in the connecting pipeline. The second circuit output of the pressure stabilizing control device is connected to the control terminal of the pressure regulating valve via a control cable. The downstream pressure measuring point is sent to the pressure stabilizing control device as a feedback signal via a cable.

2. The pneumatic valve flow and pressure stabilization control device according to claim 1, characterized in that, A pressure measuring point is installed on the pipeline at the air pressure output end of the valve positioner.

3. The pneumatic valve flow and pressure stabilization control device according to claim 2, characterized in that, The pneumatic valve control command current signal failure detection device enables automatic switching and position holding for manual on-site control. Specifically, the DCS control command current signal is input to a signal distributor via a control cable. The signal distributor outputs the command signal in two uninterrupted paths to the comparison-store trigger control device: one path goes to its internal relay trigger circuit, and the other path goes to its internal comparison-store trigger circuit. During normal pneumatic valve control, the DCS control command current signal is output through one path of the signal distributor to the normally closed contact in the relay trigger circuit of the comparison-store trigger control device, and then directly outputs to the signal receiver of the valve positioner via a cable, achieving normal current command control of the valve. When a fault occurs in the DCS control command or cable, causing signal abnormality, the comparison-store trigger circuit inside the device immediately determines the main control signal is abnormal by comparing it with the real-time DCS current signal. Fault conditions include control... When a cable is open-circuited, short-circuited, or the current signal is greater than or less than the DCS-set step value by 5% (i.e., a command fault occurs when the DCS main control is not operating), the comparison storage trigger control device will store the input second-channel control command signal in real time. If the command current signal changes abruptly or significantly, it will immediately start working. First, through relay switching, the fault control command is cut off, and the stored signal before the fault is sent to the valve positioner in real time. At this time, the normally closed contact in the relay trigger circuit becomes normally open, cutting off the fault signal; the normally open contact becomes normally closed, connecting the stored signal, achieving a disturbance-free switching. This stabilizes the valve positioner control command current signal at the output value before the fault, keeping the valve position at the position before the control signal fault. At the same time, through the switching circuit included in the comparison storage trigger control device, the external current signal generator can be manually controlled on-site to ensure continuous and uninterrupted production.

4. The pneumatic valve flow and pressure stabilization control device according to claim 3, characterized in that, The control process of the pressure stabilizing control unit is as follows: The pressure stabilizing control device receives power from the DCS main control unit and uses compressed air from the plant as its working air source. It also receives the input current signal and output air pressure signal from the valve positioner as comparison trigger signals. A pressure regulating valve is installed on the air output pipeline of the pressure stabilizing control device. The pressure measurement signal after the pressure regulating valve is used as a feedback signal to enter the pressure stabilizing control device. Its air pressure pipeline output is ultimately connected to the bypass port 3 of the two-position three-way electrically controlled directional valve. Its first circuit control output cable is connected to the coil of the two-position three-way electrically controlled directional valve, and its second circuit control output cable is directly connected to the pressure regulating valve control component. During normal operation of the pneumatically controlled valve, the valve positioner receives the main control command signal and, through the electro-pneumatic conversion function, outputs a certain air pressure. This pressure is amplified through the input port 1 and output port 2 of the two-position three-way electrically controlled directional valve and then enters the air amplifier before entering the valve. When the cylinder drives the valve to operate normally, if the control command current signal remains unchanged but the positioner output air pressure is abnormal (i.e., the output air pressure signal deviates from the corresponding value of the control current by 5%), the valve positioner is judged to be faulty. The pressure stabilizing control device receives the valve positioner control current signal measurement point A and the valve positioning output air pressure measurement point P as input comparison signals. If A remains unchanged and P deviates from the normal corresponding value by 5%, the valve positioner is judged to be faulty. The pressure stabilizing control device immediately drives the control coil S of the two-position three-way electrically controlled directional valve to be energized. At this time, the pneumatic valve input port 1 and output port 2 are disconnected, while output port 2 and bypass port 3 are connected. Simultaneously, the compensation air pressure output regulation circuit operates. Through the closed-loop control of the pressure regulating valve and the downstream pressure, the control output compensation air pressure is sent to the bypass port 3 of the two-position three-way electrically controlled directional valve, corresponding to the air pressure value ΔP before the fault. The entry of the compensation air pressure ΔP maintains the normal opening control of the valve before the fault.

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