How does a pneumatic valve work?
Pneumatic valves are one of the most common actuators. They are typically comprised of an adjusting screw, breather plug, spring, diaphragm assembly, bonnet, and stem.
Their work starts with the adjusting screw putting pre-load on the spring to launch the valve in its fail position. The diaphragm, a key component, moves with the spring and holds air pressure, and without a pneumatic alert on it, the valve will remain in its fail position. Next, the breather plug lets the non-energized side of the diaphragm move freely without getting air locked. Then, the diaphragm pressurizes when the actuator receives a signal from a pressure pilot.
Once the pilot senses upstream pressure, it sends an output signal through tubing into the valve’s actuator. As a result, the actuator actuates, driving the valve open or closed, depending on its configuration.