Digital guide
You are here:
Woodward 8915-728
Product Introduction: The 8915-728 is a high-force version of the linear electro-hydraulic servo actuator, designed for high-pressure control valves of large-power steam turbines. Compared with the standard model, its output force is increased to accommodate large-diameter control valves and withstand greater valve unbalance forces. The integrated electro-hydraulic design receives the 4–20 mA signal directly from the DCS with no external servo amplifier required. It is primarily used in new-build and retrofit projects for coal-fired and cogeneration large-power steam turbines.
Detailed content
Technical Specifications:
- Control Input Signal: 4–20 mA
- Hydraulic Medium: Turbine lubricating oil
- Supply Pressure: 0.24 – 1.1 MPa
- Rated Stroke: 38 mm
- Output Force: 15,600 N
- Power Supply: 24 Vdc
- Operating Temperature: –20 to +70 °C
- Protection Class: IP54
Functional Features:
- Enlarged cylinder structure design delivers higher output force to overcome high-pressure valve unbalance
- EM35 driver with built-in adaptive self-tuning algorithm automatically optimizes closed-loop PID parameters, reducing field commissioning workload
- LVDT displacement feedback for closed-loop position control with real-time valve position reporting
- Servo valve with self-flushing structure; oil impurities are automatically flushed away
- Built-in fault diagnostics; can output actuator fault alarm signals to the host system
Application Scenarios: Extraction/condensing steam turbine high-pressure main control valves; large-power industrial drive turbines; waste-heat recovery steam turbine speed-governing valve actuators.
Performance Parameters:
- Full-stroke time: ≤180 ms
- Positioning accuracy: ±0.25% FS
- Hysteresis: ≤0.5% FS
- Resolution: 0.1% FS
Material Composition: Cylinder barrel – high-strength cast steel; piston rod – thicker chrome-plated alloy steel; servo valve spool – wear-resistant hardened stainless steel; housing – carbon steel + cast aluminum; seals – fluorocarbon rubber + PTFE composite.
Structural Features: Integrated monoblock structure with reinforced cylinder wall thickness. Enlarged hydraulic oil-port flange to match higher flow. Electronic driver box mounted on the side of the unit. LVDT sensor coaxially arranged at the piston-rod tail. Built-in high-stiffness fault-reset spring.
