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Woodward 8915-747
Product Name: 3103 Series Electro-Hydraulic Servo Actuator (Integrated EM35 Driver, Short-Stroke Version)
Product Introduction: The 8915-747 is a short-stroke dedicated electro-hydraulic servo actuator for steam turbine control valves and extraction control valves where travel requirements are smaller. The overall footprint is compact, with the EM35 electronic driver integrated. It uses the turbine lubricating oil as the power medium and is suitable for steam turbine retrofit projects with limited installation space, delivering precise closed-loop valve position control.
Detailed content
Technical Specifications:
- Input Control Signal: 4–20 mA
- Hydraulic Medium: Turbine oil
- Supply Pressure: 0.21 – 1.03 MPa
- Rated Stroke: 25.4 mm
- Output Force: 11,200 N
- Power Supply: 24 Vdc
- Operating Temperature: –20 to +70 °C
- Protection Class: IP54
Functional Features:
- Shortened cylinder stroke with smaller overall dimensions to fit confined installation spaces
- EM35 driver with built-in piecewise correction, matched to short-stroke valve flow characteristics
- LVDT coaxial position feedback for closed-loop positioning control
- Anti-contamination servo valve, strongly adaptable to field oil conditions
- Spring fault reset – on loss of power or oil, the actuator returns to the safe closed position
Application Scenarios: Steam turbine extraction control valves; main control valves of small-power back-pressure steam turbines; anti-surge control valve actuators for compressor turbines.
Performance Parameters:
- Full-stroke response time: ≤120 ms
- Positioning accuracy: ±0.25% FS
- Hysteresis: ≤0.5% FS
- Resolution: 0.1% FS
Material Composition: Cylinder – cast steel; piston rod – chrome-plated alloy steel; servo valve spool – hardened stainless steel; seals – fluorocarbon rubber; electrical enclosure – cast aluminum.
Structural Features: Axial length of the cylinder is shortened for a compact overall structure. Servo valve mounted laterally. LVDT built into the cylinder tail. Standard oil-port flange. Internal reset spring adapted to short-stroke duty.
Working Principle: The electronic command signal enters the EM35 driver board, which converts it to current to drive the servo valve, distributing pressure oil to push the cylinder piston rod to output displacement. The LVDT acquires the position in real time to form closed-loop control. Under fault conditions, the internal spring pushes the piston rod to the valve closed position.
Installation Requirements: Preferred vertical downward installation, maximum tilt 15°, hanging (piston rod upward) is prohibited. Hydraulic piping must be flush-cleaned and equipped with a 3 μm filter.
