Description
Woodward A8251-765
Technical Specifications
- Control Type: Mechanical-hydraulic speed droop governor.
- Speed Setting: Adjustable via mechanical speeder spring.
- Droop Characteristic: Fixed or adjustable mechanical droop for stable parallel operation.
- Hydraulic Supply: Self-contained or externally supplied pressure oil.
Functional Features
- Purely Mechanical Operation: No electrical components required for basic speed control.
- Hydraulic Amplification: Multiplies small centrifugal forces into sufficient hydraulic force to move large fuel valves.
- Inherent Fail-Safe: Loss of hydraulic pressure automatically drives the fuel valve to the shut-off position.
- Robust Construction: Designed for continuous operation in harsh industrial environments.
Application Scenarios
Used in diesel engines, gas engines, and steam turbines driving pumps, compressors, and mechanical loads where electrical power is unavailable or undesirable.
Performance Parameters
- Speed Regulation: Stable droop control with good transient response.
- Reliability: Exceptional MTBF due to simple mechanical design.
- Temperature Range: Wide operating temperature range for ambient conditions.
Material Composition
Precision-machined cast iron and steel components with hardened internal surfaces and high-performance elastomer seals.
Structural Characteristics
- Form Factor: Compact, flange-mounted assembly.
- Adjustments: External speed adjuster, droop setting, and compensation needle valve.
- Connections: Mechanical linkage output and hydraulic supply/return ports.
Working Principle
Rotating flyweights sense engine speed and move a pilot valve in response to speed changes. The pilot valve meters hydraulic oil to a power piston, which moves the fuel valve to correct the speed error. A mechanical feedback linkage stabilizes the system and provides the droop characteristic.
Installation Requirements
- Mount securely to the engine or turbine with proper alignment.
- Connect hydraulic supply and return lines with appropriate fittings.
- Link the governor output to the fuel valve with zero binding.
Usage Precautions
- Maintain clean hydraulic oil to prevent pilot valve sticking.
- Lubricate mechanical linkages according to the maintenance schedule.
- Adjust compensation needle valve to prevent hunting or sluggish response.
