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Woodward 9902-405

Product Name:​ VSV (Variable Stator Vane) Hydraulic Control Mechanism
Product Introduction:​ The 9902-405 is a Woodward VSV variable stator vane control mechanism for non-aviation gas turbines, described alongside 9902-332 and 9902-406 in Manual 40110. It is mechanically similar to 9902-332 but differs in rotation direction, pressure ratings, and compliance specifications.
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Detailed content

Technical Specifications:
  • Inlet pressure: 138–690 kPa (20–100 psig)
  • Outlet pressure: 3103–3448 kPa (450–500 psig)
  • Drive speed: 0–5850 rpm
  • Rotation: Counterclockwise (CCW)
  • Speed sensing range: 2200–6000 rpm
  • Hydraulic fluid: MIL-L-23699 or MIL-L-7808, filtration 10 µm
  • Normal oil temperature: 4 to 82 °C
  • Normal ambient temperature: –7 to +93 °C; extreme –29 to +121 °C (≤ 2% of service life)
  • Compliance: GEAE Spec M50TF1838
Functional Features:​ Precise compressor VSV angle control; anti-stall protection for low-condition compressor operation; integrated tachometer pump for speed feedback; variable geometry optimization for gas turbine performance.
Application Scenarios:​ GE LM series aeroderivative gas turbine VSV regulation; industrial gas turbine compressor variable geometry control; gas turbine systems requiring anti-surge optimization.
Structural Characteristics:​ Mechano-hydraulic integrated structure with tachometer pump serrated drive shaft; similar external appearance to 9902-332 but with counterclockwise rotation and distinct pressure parameters.
Working Principle:​ The electronic controller outputs a hydraulic command; the servovalve regulates hydraulic oil flow direction and volume; the actuator piston drives the VSV vanes to rotate. The tachometer pump provides real-time speed feedback, forming a closed loop.
Installation Requirements:
  • Use a lifting strap and hoist for lifting and moving the VSV control
  • Carefully install on the turbine; the serrated drive shaft of the tachometer pump must be correctly aligned for unencumbered rotation
  • Connect hydraulic lines per figure 2-1 in Manual 40110
Usage Precautions:
  • Do not interchange with 9902-332/337/406 based on appearance; must verify outlet pressure, rotation direction, and compliance standard (M50TF1838 vs M50TF1994)
  • Confirm independent overspeed protection is in place before startup
  • Maintain hydraulic oil cleanliness per MIL-L-23699 or MIL-L-7808 specification
  • Comply with ESD protection procedures
  • Compliant as “SEP” per Pressure Equipment Directive 97/23/EC; exempt from ATEX Directive 94/9/EC as non-electrical equipment

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