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The Woodward 8256-259 is a specific part number for a ProAct™ Actuator, which is a crucial component in Woodward’s Electrically Powered Governor (EPG) and ProAct Digital Control systems. It is not a complete governor or speed controller on its own, but rather the electromechanical device that executes the commands from an electronic controller.
WOODWARD 8256-259: ProAct™ Actuator (Often Paired with a Driver)
The Woodward 8256-259 is a ProAct™ actuator that translates electrical signals from a Woodward electronic control unit (like a ProAct Speed Control or Fuel Limiter) into precise mechanical movement. This movement then adjusts the fuel rack, throttle body, or other control linkage on a prime mover (engine or turbine).
Product Overview
- Product Type: Electro-mechanical Actuator
- Manufacturer: Woodward
- Series: ProAct™ Actuator (often referred to as a ProAct 75 Actuator in older documentation)
- Function: Converts an electrical command signal (typically from a ProAct speed control or driver) into a proportional rotary or linear mechanical output to control fuel or air to an engine.
- Key Feature: It is often listed as part of a ProAct 75 Driver + Actuator combination, with the 8256-259 being the actuator component. This indicates it typically requires a separate driver module to function correctly, which provides power and signal conditioning.
- Operation: Electrically powered, it provides precise positioning with internal return springs for fail-safe operation (returning to a predefined position, often decrease-fuel or shutdown, upon signal loss).
Detailed Description
The Woodward ProAct actuators are known for their robust design, high precision, and fast response, making them indispensable in demanding industrial applications where accurate prime mover control is essential. The 8256-259 fits into this system by providing the physical muscle for control.
Key characteristics of the 8256-259 include:
- Electromechanical Operation: It uses an internal electric motor (often a torque motor) to drive its output shaft. The position of this shaft is directly proportional to the electrical command signal it receives.
- Precise Positioning: Designed to deliver accurate and repeatable positioning, which is critical for maintaining stable engine speed, load, or air/fuel ratio.
- Fail-Safe Mechanism: Incorporated return springs ensure that the actuator moves to a safe, pre-defined position (e.g., fuel cut-off or minimum fuel) if the electrical control signal is lost or power is removed.
- Driver Dependent: For the 8256-259, its operation is tightly coupled with a specific ProAct Driver module (e.g., Woodward 8400-704 or 8400-020). The driver supplies the necessary power and often performs some signal processing for the actuator.
- Robust Construction: Housed in a rugged cast aluminum casing, it’s built to withstand the harsh conditions found in engine environments, including vibrations, wide temperature fluctuations, and electromagnetic interference.
- Wide Application Range: While precise specifications for torque and travel would be in the specific product manual, ProAct actuators are generally capable of operating various fuel control linkages with low friction and mass.
Applications
The Woodward 8256-259 (as an integral part of a ProAct system) is typically used in critical control loops for:
- Diesel Engines: Controlling fuel racks on diesel engines for speed, load, and startup fuel limiting.
- Gaseous Engines: Adjusting gas valves or mixer linkages for speed and air/fuel ratio control.
- Gasoline Engines: Managing throttle plates or fuel injection systems.
- Gas Turbines: Controlling fuel valves or inlet guide vanes.
- Power Generation: Essential for the precise speed and load control of engine-driven generator sets to ensure stable electrical frequency.
- Industrial Pumps & Compressors: Where engines drive these machines, the actuator ensures accurate speed or flow regulation.
Related Products/Series
The 8256-series typically refers to ProAct actuators, while the 8400-series covers ProAct controllers and drivers. Other related part numbers in the ProAct ecosystem include:
- 8256-238: Often listed as the older part number that the 8256-259 directly replaces for the “ProAct 75 Driver + Actuator” combination. This signifies an updated component within the same functional pairing.
- 8256-260: Another ProAct Actuator, likely a variant with slightly different specifications or an updated version.
- 8400-704: A common ProAct Driver that pairs with actuators like the 8256-259.
- 8400-020: Another ProAct Driver that might pair with this actuator.
- 9907-1290: ProAct Model II Digital Speed Control, a common electronic controller that would send its command signals to a ProAct actuator.
- 9907-1291: ProAct Plus Digital Fuel Limiter, which also sends commands to the actuator to override or limit fuel.
