Fisher™ 657 Diaphragm Actuator

The Fisher™ 657 Diaphragm Actuator is a direct-acting, spring-opposed pneumatic actuator designed for reliable operation of sliding-stem control valves. Signal pressure applied to the upper diaphragm housing drives the actuator stem downward, while the spring provides fail-safe return action when pressure is reduced. This proven design is widely used in throttling and on/off service across industries such as power, chemical, and refining.

Key Features

• Reliable Performance – Rugged cast iron or steel construction ensures durability and long service life.
• Excellent Linearity – Deep diaphragm casing design minimizes change in effective area, delivering accurate response to signal pressure.
• Fast Response – Shallow pressure casing reduces air volume for quicker control action.
• High Thrust Capability – Provides strong operating force across a wide range of valve sizes.
• Flexible Options – Available with adjustable travel stops, manual handwheels, and integral mounting pads for Fisher FIELDVUE™ digital valve controllers.
• Broad Operating Range – Supports various pressure spans (3–15 psig, 6–30 psig) and temperature conditions, including cold-service construction down to –50 °C.

Variants / Related Models

• 657 (Standard) – Direct-acting actuator available in multiple sizes (30 to 100).
• 657-4 – Extended travel version for specific control valve applications.
• 657C – Long-travel design optimized for desuperheater service.
• 657NS / 657NS2 – Special-service variants designed for enhanced performance in demanding environments.
• 657R – Reverse-acting configuration where spring action extends the stem, providing alternate fail-safe operation.
• 667 Series – Reverse-acting counterpart of the 657, providing alternate fail-safe operation.

Advantages

• High reliability and stable performance under demanding operating conditions.
• Wide selection of sizes and options to suit different valve and process requirements.
• Easy integration with digital positioners and accessories.
• Proven track record in critical control applications worldwide.

Why Choose HKXYTECH

HKXYTECH is your trusted source for Fisher™ 657 Diaphragm Actuators and related control solutions.

• Authentic Products – 100% new and original Fisher actuators.
• Competitive Pricing – Cost-effective solutions without compromising quality.
• Fast Delivery – Short lead times and dependable stock availability.
• Comprehensive Support – Technical guidance, documentation, and after-sales service.

With HKXYTECH, customers gain not only access to industry-leading Fisher technology but also a reliable partner committed to reducing downtime and ensuring long-term operational safety.