ACTUATORS

A Pneumatic Actuator mainly consists of a piston, a cylinder, and valves or ports. The piston is covered by a diaphragm (seal), which keeps compressed air in the upper portion of the cylinder. The air pressure forces the diaphragm downward, moving the piston, which in turn moves the valve stem connected to the internal components of the actuator.

Pneumatic actuators may have a single signal input at either the top or bottom, depending on the required operating action. They require relatively low operating pressure and are capable of producing two to three times the applied input force.

Key Features

• Higher output force with low air pressure.
• Larger piston size provides greater output pressure.
• Suitable for high-pressure and high-flow pipeline applications.
• Provides accurate and reliable valve movement.
• Widely used for process automation and industrial flow control.

Working Principle

The input pressure acts as the control signal, typically ranging from 20–100 kPa. This signal is received from measuring devices such as pressure transmitters and is used to control the movement of the valve.

For example, when the pressure inside a vessel increases, the pressure transmitter sends a higher control signal to the actuator. The actuator moves the valve towards the closed position, reducing the incoming flow and allowing excess pressure to escape through the outlet. As the vessel pressure decreases, the actuator adjusts the valve position accordingly. This operating method is known as a Direct Acting Process.