Pneumatic Actuated Control Valves

What is a two-way pneumatic modulating control valve?

A modulating control valve regulates the fluid by changing the size of the flow passage in response to a signal from a controller. It makes pressure, temperature, flow and level control possible in any process that carries a fluid, and lets the cold water, hot water, steam, superheated water and gas a plant produces at the cost of energy be carried and controlled without loss.

What does modulating operation mean?

Modulating operation is a control concept in which the control signal is directly proportional to the error between the set point and the actual process value. In other words, the size and direction of the error determine the size and direction of the control signal, so the valve does not simply open or close — it settles at the opening the process needs.

The pneumatic actuator drives the valve with control air. A positioner converts the 4–20 mA controller signal into the corresponding stem travel and holds the valve at that position.