657 and 667 Diaphragm Actuators
657 and 667 spring-opposed diaphragmactuators position the valve plug in the valve inresponse to varying controller or valve positionerpneumatic output signals applied to the actuatordiaphragm. Zero setting of the actuator is determinedby the compression of the actuator spring. Span is setby 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.
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 Travel—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 C (-58 F). Use of a positioner is recommended to ensure responsiveness in applications operating below -40 C (-40 F).
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.
Direct Action
All 657 actuators are direct acting. Applying air pressure to the upper diaphragm casing forces the actuator stem downward. When this pressure is reduced, the opposing spring force moves the actuator stem upward. Should the loading pressure fail, the spring forces the stem to the extreme upward position. This provides fail-open action for push-down-to-close valves and fail-closed action for push-down-to-open valves.
657—A direct-acting actuator used on sliding-stem valves. Available in sizes 30 through 100. See figures 1, 2, 5, and 6.
657-4—A 657 actuator in sizes 70 and 87, designed with 102 mm (4-inch) travel.
Reverse Action
All 667 actuators are reverse acting. 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. Should the loading pressure fail, the spring forces the stem to the extreme downward position. The actuators provide fail-closed action for push-down-to-close valves and fail-open action for push-down-to-open valves.
667—A reverse-acting actuator used on sliding-stem valves. Available in sizes 30 through 100 and 76. See figures 1, 2, and 7.
667-4—A 667 actuator in sizes 70 and 87, designed with 102 mm (4-inch) travel.
Accessories
All 667 actuators are reverse acting. 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. Should the loading pressure fail, the spring forces the stem to the extreme downward position. The actuators provide fail-closed action for push-down-to-close valves and fail-open action for push-down-to-open valves.
667—A reverse-acting actuator used on sliding-stem valves. Available in sizes 30 through 100 and 76. See figures 1, 2, and 7.
667-4—A 667 actuator in sizes 70 and 87, designed with 102 mm (4-inch) travel.
Typical Actuators
Typical Top-Mounted Handwheels
646 Electro-Pneumatic Transducer on 657 Actuator
4200 Position Transmitter on 667 Actuator
3582i Valve Positioner on 657 Actuator
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