Fisher™ 644 and 645 Actuators
Fisher 644 and 645 actuators are used to automatically control steam-driven boiler feedwater pumps (reciprocating or turbine). The 644 or 645 actuator, when used in combination with one of several push-down-to-close sliding-stem valves, forms a pump governor. 644 and 645 actuators may also be combined with push-down-to-open valves to be used as relief governors.
The Fisher™ 644 and 645 Actuators, engineered by Emerson, are rugged, spring-opposed diaphragm actuators designed for use with control valves in demanding process control applications. These actuators deliver precise, reliable, and stable valve positioning under a wide range of operating pressures, making them ideal for controlling throttling or on/off valves in both industrial and oil & gas environments.
The Fisher 644 actuator is a direct-acting model, where increasing supply pressure extends the diaphragm rod, while the Fisher 645 actuator is reverse-acting, retracting the rod as supply pressure increases. Both models feature a compact, heavy-duty design that provides high thrust capability and ensures smooth, vibration-resistant operation even in harsh field conditions.
Constructed with corrosion-resistant materials, these actuators offer long service life, minimal maintenance, and easy field adjustment. When combined with Fisher control valves, the 644 and 645 actuators form a high-performance flow control solution trusted in industries such as refining, chemical processing, power generation, and natural gas transmission.
Technical Specification of Fisher™ 644 and 645 Actuators
- Actuation
- Manual
- Certifications
- CUTR
- Control Type
- On/Off
- Operating Temperature
- Standard Temperature
- Power Source
- Manual
- Valve Type
- 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™ 644 and 645 Actuators
- Steel and cast iron construction provides long service life.
- Few moving parts and easy access reduce maintenance and downtime.
- Spring adjustment is readily accessible without removing any parts.
- Direct-operated configuration provides fast speed of response.