What Is a Pneumatic Control Valve?

Pneumatic control valve is one of industrial process control instruments widely used in petroleum, chemical, electric power, metallurgy and other industrial enterprises. Usually a combination instrument formed by connecting, installing and debugging a pneumatic actuator and a regulating valve. Pneumatic control valve is characterized by simple control, fast response, and intrinsically safe. Compared with the explosion proof valve actuator, the pneumatic control valve does not require additional explosion-proof measures.

 

The common forms of pneumatic actuators mainly include single acting pneumatic actuator and double acting pneumatic actuator. According to the valve action mode, the pneumatic control valve can be basically divided into two modes: linear stroke and angular stroke.

 

Uses and Characteristics

 

Pneumatic control valve is a right-angle rotation structure. It can be used with valve positioner to realize proportional adjustment. V-shaped spool is most suitable for various adjustment occasions. It has the characteristics of large rated flow coefficient, large adjustable ratio, good sealing effect, sensitive adjustment performance, small volume, and vertical installation. Pneumatic control valve is suitable for controlling gas, steam, liquid and other media.

 

Its characteristic is that it is a right-angle rotation structure composed of a V-shaped valve body, air powered actuator, positioner and other accessories. There is an inherent flow characteristic of approximately equal percentage. It adopts double-bearing structure, low starting torque, good sensitivity and induction speed, and super shearing ability.

 

Pneumatic piston actuator uses compressed air as the power source, and drives the crank arm to rotate 90 degrees through the movement of the piston, so as to automatically open and close the valve. Its components are adjusting bolt, actuator box, crank arm, cylinder block, cylinder shaft, piston, connecting rod, cardan shaft.

 

The working principle of the pneumatic control valve: the pneumatic control valve is composed of an actuator and an adjustment mechanism. The actuator is the thrust component of the regulating valve, which generates the corresponding thrust according to the pressure of the control signal to push the regulating mechanism to move. The valve body is the regulating component of the pneumatic regulating valve, which directly contacts the regulating medium to regulate the flow of the fluid. Common valves mainly include pneumatic ball valve, pneumatic butterfly valve and bibcock ball valve.

 

The positioner can be said to be the core part of the pneumatic control valve. It has a 4-20mA input signal and output signal. The input signal is necessary for a positioner to give instructions to this valve. The output signal is what we commonly call the feedback signal, which can send a 4-20mA feedback signal to the central control room.

 

The installation position of the air actuated control valve requires a certain height from the ground. There must be a certain space above and below the valve for valve disassembly and repair. For regulating valves equipped with pneumatic valve positioners and handwheels, it is necessary to ensure convenient operation, observation and adjustment.

 

The regulating valve should be installed on a horizontal pipeline and vertical to the pipeline up and down. Generally, it should be supported under the valve to ensure stability and reliability. For special occasions, when the regulating valve needs to be installed horizontally on a vertical pipeline, the regulating valve should also be supported (except for small-diameter regulating valves). Avoid adding additional stress to the regulating valve during installation.