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Woodward 9902-403
Product Name: VSV / IGV Servovalve and Actuator System Component
Product Introduction: The 9902-403 is part of Woodward’s VSV (Variable Stator Vane) and IGV (Inlet Guide Vane) electro-hydraulic control product family, documented in Woodward manual 40136. As a member of the 9902 VSV/IGV product line, it operates within the dual servovalve and actuator system architecture that provides closed-loop positioning of compressor variable geometry on gas turbines.
Detailed content
Technical Specifications: Detailed specifications for the 9902-403 configuration (hydraulic flow rating, pressure class, torque motor current) are provided in Woodward manual 40136. Each actuator provides up to 3.445 inches (87.50 mm) of output stroke. Operating fluid: MIL-L-23699 or MIL-L-7808 turbine engine oil.
Functional Features:
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Dual, identical torque-motor servovalve stages — one dedicated to IGV, one to VSV
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Separate final drivers for IGV and VSV channels
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Closed-loop position control via integral LVDT feedback in each actuator
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Optional accumulator port (“ACC”) for fail-safe stroking capability
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Integrated filters and screens to prevent contamination
Application Scenarios: Gas turbine compressor variable stator vane and inlet guide vane control; anti-stall protection; part-load efficiency optimization; GE LM-series and other industrial gas turbines.
Structural Characteristics: The servovalve features an aluminum case with through-hardened stainless steel internal parts. Hydraulic ports marked “ROD” and “HEAD” are provided for both IGV and VSV actuators. Each actuator integrates an LVDT for position feedback. The servovalve is designed to be installed, with kit 8924-874, directly over the hydraulic pump, with supply and drain feeding through the base of the servo to the pump.
Working Principle: A hydraulic pump provides pressure to the dual servovalve. The electronic package sends separate command signals to the IGV and VSV torque motors. Each torque motor deflects its pilot stage, metering hydraulic flow to the respective actuator’s rod or head side. The actuator output shaft connects to the hardware on the inlet guide vanes and variable stator vanes. The LVDT in each actuator provides a position-proportional electrical signal back to the final driver, closing the position control loop.
Installation Requirements: Install the servovalve directly over the hydraulic pump using kit 8924-874 (includes O-rings, bolts, washers). Connect hydraulic ports ROD and HEAD to the correspondingly marked ports on each actuator. Connect the ACC port to an external accumulator if fail-safe stroking is required (accumulator not provided by Woodward). Ensure system filtration is in place. Follow the receiving, storage, and installation procedures in Chapter 2 of manual 40136.
Usage Notes: Read the entire manual 40136 and all related publications before installation, operation, or servicing. The turbine must have an independent overspeed shutdown device. Use proper PPE. Be prepared for emergency shutdown during start-up. Do not operate outside specified hydraulic, electrical, or mechanical limits. Observe ESD precautions for associated electronic controls.
