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Woodward 8915-922
Product Name: 3103 Series Electro-Hydraulic Servo Actuator (Integrated EM35 Driver, Extraction-Valve Dedicated Version)
Product Introduction: The 8915-922 is an electro-hydraulic servo actuator dedicated to steam turbine extraction control valves. Optimized for the frequent-regulation duty of extraction valves, its fatigue resistance is improved. With the integrated EM35 driver, it receives a 4–20 mA signal and uses the turbine lubricating oil source for continuous extraction pressure regulation. It is widely used in cogeneration extraction turbine units.
Detailed content
Technical Specifications:
- Input Signal: 4–20 mA
- Medium: Turbine lubricating oil
- Supply Pressure: 0.21 – 1.03 MPa
- Rated Stroke: 38 mm
- Output Force: 11,200 N
- Power Supply: 24 Vdc
- Operating Temperature: –20 to +70 °C
- Protection Class: IP54
Functional Features:
- Optimized for frequent reciprocating regulation duty; cylinder seals are fatigue-resistant
- EM35 built-in piecewise correction, matched to the flow-stroke non-linear characteristics of extraction valves
- LVDT closed-loop position feedback with high regulation accuracy
- Self-cleaning servo valve structure, adapted to frequent action
- Spring fault reset – under fault conditions the valve safely closes
Application Scenarios: Extraction control valves of extraction steam turbines; exhaust regulation valves of back-pressure units; valve actuators for industrial turbine bypass control.
Performance Parameters:
- Full-stroke response time: ≤150 ms
- Positioning accuracy: ±0.25% FS
- Hysteresis: ≤0.5% FS
- Resolution: 0.1% FS
Material Composition: Cylinder barrel – cast steel; piston rod – chrome-plated alloy steel; seals – fatigue-resistant composite; servo valve spool – hardened stainless steel; electrical enclosure – cast aluminum.
Structural Features: Reinforced cylinder seal structure; servo valve selected for frequent-action optimization; LVDT with anti-vibration locking structure; fully integrated monoblock construction.
Working Principle: The extraction pressure controller outputs a 4–20 mA command to the EM35 driver board, driving the servo valve to distribute pressure oil and push the cylinder piston rod, which in turn drives the extraction valve stem. The LVDT acquires the actual valve position for closed-loop regulation. On loss of power or oil pressure, the spring closes the valve.
Installation Requirements: Preferred piston rod vertical downward, tilt not greater than 15°, hanging prohibited.
