Flow Control Equipment, LLC maintains all sizes of 657 and 667 pneumatic actuators in remanufactured and most sizes in new surplus with optional top or side-mounted hand wheels and travel stops.
The Fisher® 657 and 667 spring and diaphragm actuators are designed to provide dependable throttling or on-off operation of linear, sliding-stem automated control valve assemblies. The actuators position the valve plug in response to the controller or valve positioner’s pneumatic output signal sent to the actuator diaphragm casing.
The 657 are fail open, direct-acting actuators. Applying air pressure to the upper diaphragm casing forces the actuator stem downward, and when pressure is reduced the spring forces the stem upward.
The 667 are fail closed, reverse acting actuators. Applying air pressure to the lower diaphragm casing forces the actuator stem upward against the opposing spring force. When this loading pressure is reduced, the spring moves the actuator stem downward. When the loading pressure fails, the spring forces the stem in the downward position.