Woodward 9908-204

Digital guide

Product Overview: This model belongs to the Woodward LQ25T series of liquid fuel metering valves, designed for industrial and aeroderivative gas turbines with output power ranging from 6,000 kW to 42,000 kW. It adopts an all-electric drive method, integrating a brushless DC motor, rotary plate metering valve, and non-contact position sensor into one unit, achieving precise closed-loop position control through a matching electronic driver. The LQ25T uses a throttling differential pressure regulator design to control the pressure differential across the metering port without bypassing fuel, making it particularly suitable for centrifugal pump or other pressure-source fuel pump systems.

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Detailed content

Technical Specifications:

Product Type: Electric liquid fuel metering valve
Control Method: Digital servo closed-loop control (with LQ driver or DVP driver)
Output Form: Rotary valve plate angular position
Input Command Signal: 4 to 20 mA
Position Feedback Output: 4 to 20 mA
Driver Power Supply: 18 to 32 VDC
Working Medium: Diesel, JP series fuel, kerosene, gasoline, naphtha, gas turbine fuel oil, and other compliant distillate fuels
Duty Cycle: Continuous regulating duty

Functional Features:

Fully electric integrated design: Brushless DC motor, metering valve, and position sensor integrated into one unit
Throttle-type differential pressure regulation: Controls the pressure differential at the metering port without bypassing fuel
Self-cleaning shear-type metering: The rotary plate valve performs a shearing metering action with self-cleaning characteristics
High flow turn-down ratio: Flow turn-down ratio exceeds 100:1
Precise flow control: Flow control accuracy is ±5% of nominal flow point or ±0.5% of maximum rated flow (whichever is greater)
Non-contact position sensing: Single-speed or three-speed resolver as feedback element
Corrosion-resistant materials: All fuel-contacting materials are corrosion-resistant
Remote driver configuration: Driver can be installed within 100 meters of the valve

Application Scenarios:

Liquid fuel precise metering for industrial gas turbines
Fuel control for aeroderivative gas turbines
Fuel regulation systems for power generation gas turbines
Fuel control for mechanically driven gas turbines
Liquid fuel systems for marine gas turbines
Fuel metering for combined heat and power (CHP) units

Performance Parameters:

Flow Range: 100 to 22,000 lb/h (45 to 9,979 kg/h)
Minimum Metering Flow: 100 lb/h (45 kg/h)
Maximum Fuel Inlet Pressure: 1,400 psig (9,653 kPa)
Regulated Differential Pressure: 50 psid (345 kPa) nominal
Metering Valve Full-Stroke Slew Rate: Less than 0.100 second
Metering Valve Shutdown Slew Rate: Less than 50 ms
Motor Speed: 35 rad/s (typical)
Flow Metering Accuracy: ±5% of nominal flow point or ±0.5% of maximum rated flow (whichever is greater)
Operating Temperature: -28°C to +103°C
Storage Temperature: -40°C to +103°C
Protection Rating: IP66
Weight: Approximately 22 kg (49 lb)

Material Composition:

Valve Body: High-strength aluminum alloy (standard) or stainless steel (marine environment type)
Metering Rotary Plate: Corrosion-resistant hardened stainless steel, precision EDM (Electrical Discharge Machining) formed
Metering Sleeve: Integrated with motor rotor, corrosion-resistant material
Motor Housing: Aluminum alloy with heat sink fins
Motor Rotor: Rare-earth permanent magnet material
Position Sensor: Single-speed or three-speed resolver
Seals: Fluoroelastomer (FKM)
Internal Fasteners: Stainless steel

Structural Features:

Integrated brushless DC motor: Motor and metering valve coaxially designed
Rotary plate metering structure: Rotary plate valve sleeve integrated with motor rotor
Non-contact resolver: Hollow shaft structure
Throttle-type differential pressure regulator: Controls pressure differential at the metering port without bypassing fuel
Standard SAE threaded ports: Complies with SAE J1926/1 and MS16142 standards
Overboard (OVBD) drain port: Provided
Standard mounting holes: On the bottom of the valve body

Working Principle: The control system outputs a 4-20 mA position command signal to the driver; the driver converts the signal into drive current for the brushless DC motor. The motor generates precisely controllable electromagnetic torque, directly driving the metering rotary plate to rotate, changing the flow area of the metering port. The built-in throttle-type differential pressure regulator maintains a constant differential pressure across the metering port, making fuel flow proportional only to the port area. The resolver detects rotor position in real time and feeds back to the driver, forming closed-loop position control.

Installation Requirements:

The valve should be installed as close as possible to the turbine
The valve body should be mounted on a rigid surface with good thermal conductivity
The inlet pipeline connects to pressurized fuel from the pump; the outlet pipeline connects to the fuel line leading to the combustion chamber
The overboard (OVBD) drain port must be connected via rigid steel pipe to a fuel collection, purge, discharge, or flare system, with back pressure not exceeding 69 kPa (10 psig)
Blocking the overboard drain port is strictly prohibited
Electrical wiring is connected via the terminal block or threaded connector on the valve body
The ambient temperature at the installation location must not exceed specified limits

Usage Precautions:

Fuel filtration accuracy must reach 20 μm or finer; water content limited to 0.1% by volume
Fuel viscosity must be within 0.5 to 12.0 cSt
Regularly inspect overboard drain line leakage
During long-term shutdowns, the valve should be exercised periodically
When replacing seals or performing repairs, specialized tools must be used
When used in hazardous locations, confirm the valve and driver have appropriate explosion-proof certification
Hearing protection must be worn when operating in turbine environments