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Woodward 8915-916
Product Name: 3103 Series Electro-Hydraulic Servo Actuator (Integrated EM35 Driver, High-Force Long-Stroke Version)
Product Introduction: The 8915-916 is a long-stroke, high-power electro-hydraulic servo actuator for large-diameter steam turbine control valves. With longer stroke and greater output force, it integrates the EM35 electronic driver and relies on steam turbine lubricating oil as the hydraulic power source. It is matched to large turbine set control valves for speed and load closed-loop regulation, and is predominantly used in coal-fired power and large cogeneration new-build and retrofit projects.
Detailed content
Technical Specifications:
- Input Signal: 4–20 mA
- Hydraulic Medium: Turbine oil
- Supply Pressure: 0.27 – 1.1 MPa
- Rated Stroke: 50.8 mm
- Output Force: 18,000 N
- Power Supply: 24 Vdc
- Operating Temperature: –20 to +70 °C
- Protection Class: IP54
Functional Features:
- Extended cylinder stroke with high output force, matched to the huge unbalance forces of large-diameter control valves
- EM35 driver with built-in 11-point piecewise linearization, adapted to non-linear flow characteristics of large valves
- Long-stroke LVDT displacement sensor for closed-loop position feedback
- Self-flushing anti-contamination servo valve structure
- High-stiffness fault reset spring for reliable valve closing on loss of power or oil pressure
- Fault alarm signal output, integrable to the DCS system
Application Scenarios: High-pressure control valves of large turbine generator sets; main control valves of large waste-heat recovery steam turbines; actuators for large axial-flow compressor drive turbines.
Performance Parameters:
- Full-stroke response time: ≤220 ms
- Positioning accuracy: ±0.3% FS
- Hysteresis: ≤0.6% FS
- Resolution: 0.1% FS
Material Composition: Cylinder barrel – thickened cast steel; piston rod – large-diameter chrome-plated alloy steel; servo valve spool – hardened stainless steel; seals – high-temperature fluorocarbon rubber; electrical enclosure – reinforced cast aluminum.
Structural Features: Cylinder axially elongated; oil-port flange enlarged; long-stroke LVDT coaxially arranged; internal high-stiffness reset spring; servo valve laterally assembled; electrical box side-mounted.
Working Principle: The control system output 4–20 mA command enters the EM35 driver board, converting to servo valve drive current. The servo valve distributes pressure oil into the two cylinder chambers to push the piston rod to output displacement. The LVDT continuously acquires position for closed-loop correction. On loss of power or oil pressure, the spring pushes the mechanism to the valve-closed safe position.
Installation Requirements: Piston rod preferred vertical downward installation, maximum tilt 10°, hanging strictly prohibited.
