Woodward 8904-625

Digital guide

Product Overview

The Woodward 8904-625 is an actuator-and-valve combination unit that integrates the TM-55I integral electrohydraulic actuator with the 3103 series stainless steel gas valve. The part corresponds to a specific configuration of the HLR-750-10000 series linear position sensor. Designed for industrial gas turbine fuel control applications, the TM-55I actuator receives command signals from the electronic controller and uses an electrohydraulic servo drive system to precisely control the opening of the 3103 gas valve’s rotary metering sleeve, achieving high-precision metering and regulation of gas flow. The combination unit is functionally matched and calibrated at the factory and can be directly installed in turbine fuel systems.

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Technical Specifications

Part number: 8904-625
Manufacturer: Woodward
Equipment type: Actuator and valve combination unit
Actuator type: TM-55I integral electrohydraulic actuator
Valve type: 3103 series stainless steel gas valve
Drive method: Electrohydraulic servo drive
Position feedback: Built-in electrical position sensor
Companion sensor: Corresponding to HLR-750-10000 series linear position sensor

Performance Parameters

Actuator output torque: 30 to 75 N·m (22 to 55 lb-ft)
Actuator weight: Approx. 6.6 kg (14.5 lb)
Valve flow range: 23 to 18144 kg/h (50 to 40000 lb/h)
Gas supply pressure: Up to 600 psig (4137 kPa)
Differential pressure range: 25 to 600 psi (172 to 4137 kPa)
Gas temperature range: -40 °C to +149 °C (-40 °F to +300 °F)
Hydraulic oil supply pressure: 400 to 1000 psig (2758 to 6895 kPa), with ±20% allowable fluctuation
Hydraulic oil viscosity range: 0.6 to 400 cSt
Hydraulic oil filtration accuracy: 10 micron nominal
Ambient temperature range: -40 °C to +121 °C (-40 °F to +250 °F)
Explosion-proof certification: UL Listed Class I, Division 1, Groups C & D; CSA Listed C22.2

Functional Features

Actuator and valve are pre-matched at the factory with calibration completed, reducing on-site commissioning workload
TM-55I integral actuator uses a torque motor servovalve drive, offering rapid response and high control precision
The 3103 gas valve adopts a rotary sleeve and shoe-type throttling structure, providing excellent contamination resistance
The valve design includes an inlet guide tube that directs gas impurities toward the metering port, reducing impurity accumulation within the valve body
The metering sleeve support bearing is completely sealed from the gas, protecting internal mechanisms
The actuator automatically biases toward the minimum fuel direction upon power loss, providing fail-safe protection
Internal components are made of fully hardened stainless steel, offering both corrosion and wear resistance

Application Scenarios

Fuel control for industrial gas turbine generator sets
Fuel management for gas compressor drive units
Gas supply regulation in combined heat and power (CHP) systems
Gas flow control in distributed energy stations
Marine and offshore platform gas power units

Material Composition

Actuator housing: High-strength aluminum alloy
Actuator internal parts: Fully hardened stainless steel
Valve body: Precision-cast stainless steel
Metering sleeve and shoe: Fully hardened stainless steel, precision-ground
Seals: Fluoroelastomer (FKM) or other gas-resistant elastomers
Hydraulic seals: Preformed packing rings to prevent magnetic contaminant accumulation

Structural Characteristics

Direct connection between actuator and valve via adapter with no intermediate transmission links
Rotary sleeve and shoe metering structure with excellent flow resistance characteristics
Double-acting servo piston provides powerful driving force
40-micron filtration mesh built into the hydraulic inlet fitting for additional contamination protection
Electrical position feedback sensor built into the actuator for closed-loop control
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.

Installation Requirements

Handle with care during component handling and installation to avoid damaging seals, mounting surfaces, and factory adjustment settings
Hydraulic and gas connection ports must be protected with plastic caps or covers when not connected to formal piping
The actuator is calibrated and drained of calibration fluid at the factory; no additional cleaning or calibration is required before installation
Confirm that the hydraulic oil supply pressure meets the specified range before installation
The hydraulic system must be purged of trapped air to prevent abnormal initial actuator operation
A filter meeting requirements must be configured at the gas inlet
Shielded cables must be used for electrical connections with proper grounding

Usage Notes

Hydraulic oil cleanliness is critical to actuator service life and the specified filtration grade must be maintained
Gas impurity content must be strictly controlled: solid particles smaller than 10 microns shall not exceed 30 ppm in concentration, and those larger than 10 microns shall not exceed 0.3 ppm
Regularly inspect hydraulic system pressure and oil condition
Avoid operation under conditions of overpressure, overtemperature, or outside the viscosity range
Regularly check the sealing integrity of electrical connectors and the stability of position feedback signals
Actuator maintenance intervals shall follow Woodward OEM recommendations; return the unit to the factory for overhaul upon expiration to restore it to a “like-new” condition