Product Critical Technical Advantages
-
Integral Mounting Pad: The 657-4 features a cast-in mounting pad that simplifies the attachment of positioners and accessories. By eliminating traditional bolt-on brackets, the actuator maintains better alignment with the valve stem and reduces the mechanical vibration that can affect control accuracy.
-
Tubing-Free Instrument Integration: When paired with a FIELDVUE digital valve controller, the actuator utilizes an internal air passage. This design choice eliminates the need for external copper or stainless steel tubing between the positioner and the diaphragm casing, removing common leak points and reducing maintenance complexity.
-
High-Speed Response Casing: The pressure side of the diaphragm casing is designed with a shallow profile to minimize internal volume. This allows the actuator to respond almost instantaneously to pneumatic signal changes, ensuring tight control in high-speed process loops.
-
Molded Diaphragm for Maximum Thrust: The 657-4 uses a molded diaphragm that provides a large effective surface area relative to its outer diameter. The deep casing allows the diaphragm to travel throughout its stroke with minimal changes to that effective area, ensuring consistent force delivery from start to finish.
-
Rugged Industrial Build: The casing and yoke are constructed from heavy-walled cast iron or steel. This provides the necessary weight and stability to handle high-pressure process fluids and protects the internal spring and stem from corrosive atmospheric conditions.
Key Specifications
| Feature | Technical Specification |
| Actuator Type | Direct-Acting (Air-to-Push Down) |
| Casing Material | Cast Iron or Steel |
| Diaphragm Material | Nitrile on Nylon (Standard); Silicone available |
| Typical Travel | 19 mm to 51 mm (0.75 to 2 inches) |
| Operating Pressure | Up to 2.8 bar (40 psig) for standard units |
| Mounting | Integral Pad or Traditional Yoke |
Field of Application
-
Refinery Control Loops: Ideal for managing hydrocarbon flow where “fail-open” safety logic is required.
-
Chemical Plant Automation: Used in reactors and heat exchangers where precise throttling is necessary to maintain chemical reactions.
-
Steam Distribution: Reliable operation in high-temperature environments when equipped with heat-resistant diaphragm materials.
-
Water Treatment: Automated control of filtration and dosing lines where rugged, low-maintenance hardware is essential.
