Fisher® 657 and 6670 pages

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657 and 667 Actuators

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D100087X012

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Product Bulletin

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61.1:657

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May 2012

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Fisher® 657 and 667 Diaphragm Actuators

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Fisher 657 and 667 spring-opposed diaphragm

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actuators position the valve plug in the valve in

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response to varying controller or valve positioner

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pneumatic output signals applied to the actuator

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diaphragm. Zero setting of the actuator is determined

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by the compression of the actuator spring. Span is set

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by both the actuator spring rate and the number of

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springs available. The 657 actuator is direct-acting; the

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667 is reverse-acting. These actuators are designed to

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provide dependable on-off or throttling operation of

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automatic control valves.

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Features

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Application Versatility—Five actuator types in eleven

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sizes are available for an extensive variety of

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applications. Spring rates, travel stops, and manual

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operators are available for nearly any control valve

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application.

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Excellent Linearity Between Loading Pressure and

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Travel—A molded diaphragm travels in a deep

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diaphragm casing, minimizing area change

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throughout the travel.

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High Degree of Dynamic Stability and Frequency

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Response—A shallow casing on the pressure side

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means reduced volume on that side, thereby

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minimizing response time.

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High Thrust Capability—The molded diaphragm

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allows maximum thrust for given diaphragm size.

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Long Service Life—Rugged thick-walled cast iron and

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steel construction provides increased stability,

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corrosion protection, and protection from

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deformation should over-pressurization occur.

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657 ACTUATOR

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667 ACTUATOR

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Fisher 657 and 667 Actuators Mounted on

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easy-e™ Valves

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Cold Service Applications—Enhanced product

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specifications for all sizes of 657 and 667 diaphragm

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actuators allow performance to -50°C (-58° F). Use

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of a positioner is recommended to ensure

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responsiveness in applications operating below

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-40°C(-40°F).

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Positive Connections—A split block stem connection

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provides a solid transfer of motion while allowing

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easy mounting. The absence of linkages helps to

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avoid lost motion and inaccurate valve positioning.

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FISHER

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www.Fisher.com

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EMERSON

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Process Management

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