How does a pneumatic diaphragm actuator work?

• A. Air moves diaphragm up or down which opens or closes the valve
• B. Electric current causes expansion of a diaphragm
• C. Hydraulic fluid inflates a cylinder to move the valve
• D. Pneumatic pressure seals the diaphragm but does not move it

Answer: (A)

A pneumatic diaphragm actuator works by using compressed air to flex a flexible diaphragm, producing linear motion that opens or closes the valve. The diaphragm sits between the air side and the valve side; when air pressure is applied to one side, the diaphragm deflects and pushes the connected valve stem to move the valve toward open or closed. Often a return spring (or reverse air pressure) provides the return or sets the direction, so releasing pressure lets the valve return to its rest position. This arrangement makes the actuator compact, quiet, and reliable for converting pneumatic energy into valve motion. In short, air pressure moves the diaphragm, and that motion actuates the valve.