"SO" SPRING TO OPEN
(on - off Control)

This actuator/accessory package is designed to normally position the valve open. The valve will close when compressed air is admitted into the upper actuator chamber and the actuator spring will open the valve when the air is exhausted.

"AA" AIR-AIR, DOUBLE ACTING
(on - off Control)

This actuator/accessory package is designed to open the valve when compressed air is admitted into the lower chamber and closes the valve when compressed air is admitted into the upper chamber.

"AA" AIR-AIR, DOUBLE ACTING
(automatic throttling)

This actuator/accessory package is provided with a positioner to accurately throttle the valve for pressure, liquid level, flow, temperature, and other control requirements. A transducer is generally supplied to provide valve modulation proportional to an electric signal (most often 4-20 ma).

"SC" SPRING TO CLOSE
(on - off Control)

Or Automatic Throttling (not shown) This actuator/accessory package is designed to normally position the valve closed. The valve will open when compressed air is admitted into the lower actuator chamber and the actuator spring will close the valve when the air is exhausted.