Fisher™ 657 and 667 Diaphragm Actuators

Fisher 657 and 667 actuators are designed to ensure stable on/off or throttling operation of control valves. These spring-balanced diaphragm actuators respond to changing pneumatic output signals from a controller or valve positioner to determine the position of the valve spool. The 657 actuator is a direct-acting actuator; the 667 actuator is a reaction-acting actuator.