Fisher 657 and 667 Diaphragm Actuators
Fisher™ 657 and 667 actuators are designed to provide dependable on/off or throttling operation of control valves. These spring-opposed diaphragm actuators position the valve plug in the valve in response to varying controller or valve positioner pneumatic output signals. The 657 actuator is direct-acting, while the 667 is reverse-acting.