Pneumatic gate valve is an industrial valve that controls the vertical lifting of the gate plate through a pneumatic actuator to achieve the opening and closing of fluids.

Pneumatic control valve = Control valve body + Pneumatic actuator + Valve positioner.

1. Control signal: A 4-20mA DC current signal is sent from the controller (such as DCS, PLC).
2. Valve positioner (the core brain):
   • It receives this 4-20mA control signal.
   • At the same time, it detects the position of the actuator's valve stem (mechanical feedback).
   • The positioner compares the control signal with the valve position feedback:
   • If they are not consistent, the positioner will output a stream of compressed air (or exhaust) to the actuator.
   • Objective: Drive the valve until the valve stem position precisely corresponds to the control signal.
3. Pneumatic actuator (power muscle):
   • It receives the air source pressure from the positioner, pushing the diaphragm or piston to move, generating thrust/torque.
   • It drives the valve stem to move linearly or rotationally.
4. Control valve body (regulating organ):
   • The movement of the valve core relative to the valve seat changes the area of the flow path, thereby precisely regulating the flow of the fluid.

Simple closed-loop control process:

• Controller output signal (4-20mA) → Positioner → Actuator → Valve stem displacement → Change flow rate → Process parameter change → Sensor detection → Controller...

• Explosion-proof safety: Powered by compressed air, it is intrinsically safe and particularly suitable for flammable and explosive sites such as petroleum and chemical industries.
• High output force and smooth, reliable operation: It can withstand high pressure differences.
• Simple maintenance: The structure is relatively simple compared to electric valves, and has low technical requirements for maintenance personnel.
• Strong overload capacity: The actuator can be designed to reach the limit position without damage.
• Moderate cost: The technology is mature and has a high cost-performance ratio.

• Pneumatic control valves are almost used in all continuous process industries.
• Petrochemical industry: Feed control of distillation columns, reflux control, temperature and pressure control of reactors.
• Power industry: Boiler feed water, desuperheater and pressure reducing valve, steam temperature control.
• Metallurgical industry: Fuel and air ratio control of heating furnaces.
• Light industry and papermaking: Concentration and pulp blending adjustment.
• Water treatment: Precise control of pH value and dosing amount.

Pneumatic control valves are the "final executive" and "safety guardians" in process control. They are not simple on-off switches but rather precise, continuously adjustable terminal control devices. Their inherent safety, high output force, and mature technology have made them dominant in demanding process industries. From simple liquid level control to complex multi-variable systems, the final actions are all carried out by them. A well-designed and properly selected pneumatic control valve system is the lifeline for ensuring the stable, efficient, and safe operation of production facilities.