Fisher 657 and 667 Diaphragm Actuators

The Fisher 657 and 667 Diaphragm Actuators are rugged, high-performance pneumatic actuators engineered to provide precise control and reliable operation for a wide range of control valves in industrial applications. Designed and manufactured by Emerson, these actuators deliver exceptional stability, repeatability, and durability under demanding process conditions. The Fisher 657 series is a spring-opposed, direct-acting diaphragm actuator, typically used for throttling or on/off control of sliding-stem valves. It utilizes air pressure on the diaphragm to move the actuator stem downward, with an opposing spring providing the return force. The Fisher 667 series, on the other hand, is a reverse-acting diaphragm actuator, where air pressure lifts the actuator stem upward against the spring force—ideal for applications requiring opposite action or fail-safe positioning. Constructed from high-quality, corrosion-resistant materials, both series are designed to withstand harsh industrial environments, including those in the oil and gas, petrochemical, power generation, and process control industries. They feature integral travel stops, high-thrust output capability, and low hysteresis, ensuring smooth and accurate valve operation with minimal maintenance over their service life. Both the 657 and 667 actuators can be fitted with a variety of valve positioners, manual handwheels, and accessory devices for enhanced control, positioning accuracy, and fail-safe response. Their simple, field-proven design ensures easy installation, calibration, and maintenance, making them a trusted choice for critical process applications worldwide.

Technical Specification of Fisher 657 and 667 Diaphragm Actuators

Actuation

Spring-return, Linear

Certifications

SIL capable, ATEX, CUTR, PED

Control Type

On/Off, Throttling

Operating Temperature

Cryogenic, Low Temperature, Standard Temperature, High Temperature

Power Source

Pneumatic, Manual

Valve Type

Angle Valve, Globe Valve

Other Configurations

Contact your local Emerson business partner or sales office to learn about additional specifications or options for this product.

Feature of Fisher 657 and 667 Diaphragm Actuators

• The integral mounting pad eliminates the traditional mounting bracket and reduces the number of parts required to mount.
• Incorporates an integral air passage that eliminates the need for external tubing and fittings when paired with a Fisher FIELDVUE™ instrument.
• Both 657 and 667 actuators are compatible with instruments that utilize traditional bracket-based mounting kits. The 667 can be externally tubed for instruments or accessories when required.
• Spring rates, travel stops, and manual operators are available for nearly any control valve application.
• A molded diaphragm travels in a deep diaphragm casing, minimizing area change throughout the travel.
• A shallow casing on the pressure side means reduced volume on that side, thereby minimizing response time.
• The molded diaphragm allows maximum thrust for given diaphragm size.
• Rugged thick-walled cast iron and steel construction provides increased stability and corrosion protection.