Woodward 9902-365

Digital guide

Product Name: VariStroke Linear Electro-Hydraulic Valve Actuator (Integrated Double Acting Type)

Product Introduction: The 9902-365 belongs to Woodward’s VariStroke series of linear electro-hydraulic actuators. This series is designed for steam turbine and hydro turbine control valves (or valve groups), utilizing a low-pressure hydraulic oil source (typically turbine lubricating oil) to provide output shaft thrust. Its excellent precision and resolution make it highly suitable for steam valve control applications where turbine availability and runtime are critical.

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Detailed content

Technical Specifications:

Linearity: ±1.0% of full scale
Repeatability: ±0.5% of full scale
Temperature drift: 0.04%/°C
Opening response rate: 200 mm/s (8 in/s)
Closing/trip rate: Up to 254 mm/s (10 in/s)
Stroke length: 50–457 mm (2–18 inches), field-configurable
Maximum stall force: 450–18,000 kg @ 35 bar (depending on bore size and direction/model)
Bore sizes: 102/152/254/305 mm (4/6/10/12 inches)
Cylinder type: Double Acting, some models optionally single acting
Fail-safe direction: Extend or Retract, depending on model
Supply voltage: 90–150 VDC (auxiliary power)
Analog input: 1 isolated 4–20 mA (dual redundant optional)
Analog output: 1 channel 4–20 mA valve position feedback
Discrete input: 1 isolated (run/enable)
Relay outputs: 2 (alarm & trip)
Communication ports: 2 redundant CANopen + 1 RS-232 service port
Side load capacity: Sustained 10% of rated output
Operating temperature: –40 to +85 °C
Protection rating: IP66

Functional Features: Anti-contamination design with only 2 moving parts and self-cleaning servovalve ports with 50 lbf debris shearing capability; variable stroke configurable via software; 11-point linearization table to compensate for valve flow nonlinearity; soft stop function to decelerate before valve seat, extending valve and seat life; side load tolerance via high-precision bearings and triple sealing technology; redundant design with dual CANopen networks and dual redundant LVDT/MLDT position sensors; adaptive control algorithm with auto-tuning PID parameters.

Application Scenarios: Steam turbine main steam valve and control valve linear positioning; turbine bypass valve control; hydro turbine guide vane control; compressor anti-surge valve control; retrofit replacement for legacy servo systems.

Structural Characteristics: Integrated design combining double-acting hydraulic cylinder + integrated servovalve + electronic driver; output shaft with visible stroke scale; built-in fail-safe return spring (depending on model); high-precision bearing-supported output shaft; triple sealing technology to prevent oil leakage; hydraulic cushioning device to protect piston end points.

Working Principle: The control system outputs a 4–20 mA position command signal. The VariStroke internal driver receives the signal and drives the servovalve to shift, allowing hydraulic oil to enter the corresponding cylinder chamber and push the piston to move.

Installation Requirements: Install per mounting drawing with field-configured stroke length; ensure hydraulic oil supply meets 35 bar working pressure; align output shaft coupling with valve stem; connect CANopen and 4–20 mA circuits with proper shielding.

Usage Precautions: