Fisher 657 and 667

Fisher 667 spring-opposed diaphragm actuators position the valve plug in the valve in response to varying controller or valve positioner pneumatic output signals applied to the actuator diaphragm. 

Zero setting of the actuator is determined by the compression of the actuator spring. Span is set by both the actuator spring rate and the number of springs available. This actuator is designed to provide dependable on-off or throttling operation of automatic control valves.


  • Application versatility
  • Excellent linearity between loading pressure and travel
  • High degree of dynamic stability and frequency response
  • High thrust capability
  • Long service life
  • Cold service applications
  • Positive connections 
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