Pneumatic control valve achieves precise adjustment of pipeline medium flow rate, pressure and other parameters through the cooperation of actuator, locator and valve body. Its working principle is as follows:

Executing Agency: Power Conversion Core

The actuator uses compressed air as a power source to convert air pressure signals into mechanical displacement. Common types include membrane type and piston type:

Thin film type: composed of a thin film, compression spring, and push rod. Air pressure acts on the thin film to deform it and push the push rod to move; The spring resets the push rod when the air pressure disappears and changes the output force by adjusting the preload force.

Piston type: composed of a cylinder, piston, and connecting rod. The piston moves in a straight line inside the cylinder and transmits displacement to the valve core through the connecting rod, which is suitable for high-pressure and large-diameter scenarios.

The actuator generates corresponding thrust based on the magnitude of the input air pressure signal, driving the valve body to move. Its mode of action is divided into positive action (push rod downward when air pressure increases) and negative action (push rod upward when air pressure increases).

Positioner: Precise Control Guarantee

The locator converts electrical signals (such as 4-20mA current) into air pressure signals through force balance or displacement balance principles, and adjusts the actuator action in real time to ensure that the valve opening is consistent with the input signal. The workflow is as follows:

Compare the input signal with the feedback signal (generated by valve stem displacement) to generate a deviation signal;

The deviation signal is amplified and output to control the air pressure, driving the actuator to act;

When the valve is activated, the feedback component continuously monitors the actual position, and the locator continuously corrects the output until the deviation is zero and the valve stabilizes at the set opening.

The locator can eliminate the instability of the actuator film and spring, improve the adjustment accuracy, and achieve functions such as fast positioning and improved flow characteristics.

Valve body: medium regulating terminal

The valve body is in direct contact with the medium, and the flow cross-sectional area is changed through the cooperation of the valve core and valve seat, achieving flow and pressure regulation. Common valve core structures include straight through, spherical, plunger shaped, etc. When the actuator pushes the valve stem, the valve core moves, changing the gap between it and the valve seat, thereby adjusting the medium resistance. For example, a pneumatic valve opens wider when the air pressure increases, while a pneumatic valve closes.