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Woodward 8904-787
Product Overview
The Woodward 8904-787 is an actuator-and-valve combination unit that integrates the TM-55I integral electrohydraulic actuator with the 3103 series stainless steel gas valve. The component is specifically designed for industrial gas turbine fuel control applications. The TM-55I actuator receives command signals from the electronic controller and precisely controls the opening of the 3103 gas valve’s rotary metering sleeve via an electrohydraulic servo drive system, achieving high-precision metering and regulation of gas flow. This part is documented as a used or surplus GE gas turbine part.
Detailed content
Technical Specifications
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Part number: 8904-787
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Manufacturer: Woodward
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Equipment description: 3103 Valve c/w TM55 Actuator
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Equipment type: Actuator and valve combination unit
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Actuator type: TM-55I integral electrohydraulic actuator
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Valve type: 3103 series stainless steel gas valve
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Drive method: Electrohydraulic servo drive
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Position feedback: Built-in electrical position sensor
Performance Parameters
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Actuator output torque: 30 to 75 N·m (22 to 55 lb-ft)
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Actuator weight: Approx. 6.6 kg (14.5 lb)
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Valve flow range: 23 to 18144 kg/h (50 to 40000 lb/h)
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Gas supply pressure: Up to 600 psig (4137 kPa)
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Differential pressure range: 25 to 600 psi (172 to 4137 kPa)
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Gas temperature range: -40 °C to +149 °C (-40 °F to +300 °F)
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Hydraulic oil supply pressure: 400 to 1000 psig (2758 to 6895 kPa), with ±20% allowable fluctuation
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Hydraulic oil viscosity range: 0.6 to 400 cSt
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Hydraulic oil filtration accuracy: 10 micron nominal
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Ambient temperature range: -40 °C to +121 °C (-40 °F to +250 °F)
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Explosion-proof certification: UL Listed Class I, Division 1, Groups C & D; CSA Listed C22.2
Functional Features
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Actuator and valve are pre-matched at the factory with calibration completed, reducing on-site commissioning workload
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TM-55I integral actuator uses a torque motor servovalve drive, offering rapid response and high control precision
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The 3103 gas valve adopts a rotary sleeve and shoe-type throttling structure, providing excellent contamination resistance
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The valve design includes an inlet guide tube that directs gas impurities toward the metering port, reducing impurity accumulation within the valve body
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The metering sleeve support bearing is completely sealed from the gas, protecting internal mechanisms
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The actuator automatically biases toward the minimum fuel direction upon power loss, providing fail-safe protection
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Internal components are made of fully hardened stainless steel, offering both corrosion and wear resistance
Application Scenarios
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Fuel control for industrial gas turbine generator sets
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Fuel management for gas compressor drive units
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Gas supply regulation in combined heat and power (CHP) systems
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Gas flow control in distributed energy stations
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Marine and offshore platform gas power units
Material Composition
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Actuator housing: High-strength aluminum alloy
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Actuator internal parts: Fully hardened stainless steel
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Valve body: Precision-cast stainless steel
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Metering sleeve and shoe: Fully hardened stainless steel, precision-ground
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Seals: Fluoroelastomer (FKM) or other gas-resistant elastomers
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Hydraulic seals: Preformed packing rings to prevent magnetic contaminant accumulation
Structural Characteristics
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Direct connection between actuator and valve via adapter with no intermediate transmission links
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Rotary sleeve and shoe metering structure with excellent flow resistance characteristics
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Double-acting servo piston provides powerful driving force
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40-micron filtration mesh built into the hydraulic inlet fitting for additional contamination protection
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Electrical position feedback sensor built into the actuator for closed-loop control
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Compact overall structure facilitating installation within turbine compartments
Working Principle
The electronic controller sends an electrical command signal to the torque motor servovalve within the TM-55I actuator. The servovalve generates a differential pressure that drives the second-stage spool valve, regulating the flow of hydraulic oil to both ends of the double-acting servo piston. Piston movement drives the final output shaft to rotate, which in turn drives the metering sleeve of the 3103 gas valve to change its opening. The built-in electrical position sensor continuously detects the actuator/valve position and feeds back to the controller, forming a high-precision closed-loop position control. When the control system loses power, the actuator’s spring-loaded mechanism pushes the valve to the minimum fuel position, achieving fail-safe protection.
