Description
Woodward 9905-144
Technical Specifications
- Actuation Type: Electro-hydraulic with integrated position feedback.
- Control Signal: Accepts standard 4-20 mA or 0-10V DC commands.
- Feedback Device: High-resolution LVDT for closed-loop positioning.
- Fail-Safe: Spring-return to fuel-off or safe position on power loss.
Functional Features
- Starting Envelope Control: Precisely limits fuel during cranking and acceleration to prevent black smoke or over-speed.
- High Dynamic Response: Fast actuator movement to meet strict start-up timing requirements.
- Closed-Loop Accuracy: Continuous position feedback ensures exact fuel rack alignment.
- Robust Construction: Designed to withstand high vibration and thermal cycling.
Application Scenarios
Used in large marine diesel engines, stationary power generation, and mechanical drive turbines requiring precise fuel metering during start-up.
Performance Parameters
- Positioning Accuracy: Better than ±0.5% of full stroke.
- Response Time: Millisecond-level response for optimal start-up control.
Material Composition
Precision-machined steel body with high-performance seals and a durable epoxy-encapsulated LVDT assembly.
Structural Characteristics
- Mounting: Flange-mounted for direct attachment to the fuel pump or valve body.
- Connections: Hermetically sealed electrical connector and SAE hydraulic ports.
Working Principle
During engine start, the governor sends a compensated fuel command to the actuator. The internal servo valve meters hydraulic oil to move the piston. The LVDT continuously feeds back the actual position, ensuring the fuel rack moves exactly as commanded to safely accelerate the engine.
Installation Requirements
- Ensure hydraulic oil supply is clean and meets pressure specifications.
- Mechanically link the actuator to the fuel rack with zero binding.
- Verify the fail-safe spring direction matches the engine’s safety requirements.
Usage Precautions
- Never bypass the fail-safe spring mechanism.
- Monitor hydraulic supply pressure during start-up sequences.
- Perform stroke calibration after any mechanical maintenance.
