FISHER™ 657 and 667 Diaphragm Actuators

Fisher 657 and 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. The 657 actuator is direct-acting; the 667 is reverse-acting. These actuators are designed to provide dependable on-off or throttling operation of automatic control valves.

Main Features

Application Versatility

Five actuator types in eleven sizes are available for an extensive variety of
applications. Spring rates, travel stops, and manual operators are available for nearly any control valve application.

Excellent Linearity Between Loading Pressure and Trave

A molded diaphragm travels in a deep diaphragm casing, minimizing area change throughout the travel.

High Degree of Dynamic Stability and Frequency Response

A shallow casing on the pressure side means reduced volume on that side, thereby
minimizing response time.

High Thrust Capability

The molded diaphragm allows maximum thrust for given diaphragm size.

Long Service Life

Rugged thick-walled cast iron and steel construction provides increased stability, corrosion protection, and protection from deformation should over-pressurization occur.

Cold Service Applications

Enhanced product specifications for all sizes of 657 and 667 diaphragm actuators allow performance to -50℃ (-58℉). Use of a positioner is recommended to ensure responsiveness in applications operating below -40℃ (-40℉).

Positive Connections

A split block stem connection provides a solid transfer of motion while allowing
easy mounting. The absence of linkages helps to avoid lost motion and inaccurate valve positioning.

Specifications

Size:SIZE 30-87
Operating Temperature Range

Standard Construction (Nitrile Elastomers): -40 to 82℃ (-40 to 180℉)
Optional Construction (Silicone Diaphragm): -40 to 149℃ (-40 to 300℉)
Maximum Valve Packing Box Temperature: 427℃(800℉) with cast iron yoke

Other configurations: Consult your Emerson sales office or Local Business Partner

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