Woodward 9907-321

Digital guide

Product Name: LQ25 Liquid Fuel Metering Valve

Product Introduction: The 9907-321 belongs to Woodward’s LQ25 series of electric liquid fuel metering valves, designed for industrial and aero-derivative gas turbines in the 6,000 kW to 42,000 kW output range. It combines a brushless DC motor, rotary plate metering valve, and non-contact position sensor into a fully integrated all-electric package, delivering precise closed-loop metering under digital servo control with a remote driver.

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Detailed content

Technical Specifications:

Product Type: Electrically driven liquid fuel metering valve
Control Mode: Digital servo closed-loop control (with matched LQ/LO driver)
Output Form: Rotary plate angular position
Input Command Signal: 4 to 20 mA
Position Feedback Output: 4 to 20 mA
Driver Supply: 18 to 32 VDC
Operating Media: Diesel, JP series fuels, kerosene, gasoline, naphtha, gas turbine fuel oil, and other compliant distillates
Duty: Continuous modulation

Functional Features:

Fully integrated all-electric design with brushless DC motor, metering valve, and position sensor — no gear backlash and no stepper motor oscillation
Self-cleaning shear-type metering via rotary plate, strong anti-pollution capability
High flow turn-down ratio exceeding 100:1, satisfying wide-range fuel demands from ignition to full load
Flow accuracy of ±5% of nominal flow point or ±0.5% of maximum rated flow (whichever is greater)
Non-contact position sensing using a single- or three-speed resolver — no mechanical wear, long service life
Built-in differential pressure regulator: single-stage spring-loaded piston diaphragm type maintaining constant pressure differential across the metering port
Corrosion-resistant materials in all fuel-wetted parts, adapted to various liquid fuels
Remote driver placement up to 100 meters from the valve, avoiding exposure to hazardous atmospheres

Application Scenarios: Liquid fuel metering for industrial gas turbines; fuel control for aero-derivative gas turbines; fuel regulation systems for power-generation gas turbines; fuel control for mechanical-drive gas turbines; marine gas turbine liquid fuel systems; fuel metering for combined heat and power (CHP) units.

Performance Parameters:

Flow Range: 80 to 26,000 lb/h (36 to 11,794 kg/h)
Maximum Fuel Inlet Pressure: 1,200 psig (8,274 kPa)
Maximum Fuel Bypass Pressure: 100 psig (690 kPa)
Regulated Differential Pressure: 50 psid (345 kPa) nominal
Pressurizing Valve Opening Pressure: 200 psid (1,379 kPa)
Full-Stroke Slew Rate: less than 0.100 s (closed-loop position control)
Valve Shut-off Slew Rate: less than 50 ms (@ 24 VDC to driver)
Motor Speed: 35 rad/s (typ.)
Metering Leakage: less than 80 lb/h @ 600 psig P1 pressure (less than 36 kg/h @ 4,137 kPa)
Operating Temperature: -28°C to +103°C (-18°F to +217°F)
Storage Temperature: -40°C to +103°C (-40°F to +217°F)
Protection Rating: IP66 (per IEC 60529)

Material Composition:

Valve Body: High-strength aluminum alloy (standard) or stainless steel (marine environment)
Metering Plate: Corrosion-resistant hardened stainless steel, precision EDM-machined
Metering Sleeve: Integrated with motor rotor, corrosion-resistant material
Motor Housing: Aluminum alloy with cooling fins
Motor Rotor: Rare-earth permanent magnet material
Position Sensor: Single- or three-speed resolver
Differential Pressure Regulator: Spring-loaded piston diaphragm type
Seals: Fluoroelastomer (FKM)
Internal Fasteners: Stainless steel

Structural Features:

Integrated brushless DC motor co-axial with the metering valve — no gear transmission, eliminating backlash and wear
Rotary plate metering structure — metering sleeve integrated with motor rotor, single moving part for fuel metering
Hollow-shaft non-contact resolver directly detecting rotor position with no contact wear
Built-in differential pressure regulator maintaining ≈345 kPa across the metering port
Standard SAE threaded ports; for the 9907-321 installation drawing the fuel connections are: INLET straight thread 1.625-12 SAE (-20), OUTLET straight thread 1.625-12 SAE (-20), BYPASS straight thread 1.625-12 SAE (-20), OVBD straight thread 0.438-20 SAE (-04) external drain port
Overboard drain port (OVBD) between dual-redundant shaft seals for leak monitoring
Standard mounting holes on valve bottom for rigid bracket mounting

Working Principle: The control system sends a 4-20 mA position command to the matched driver; the driver converts the signal into brushless DC motor drive current. The rotor drives the metering sleeve, changing the effective flow area of the metering port. The built-in differential pressure regulator maintains a constant 345 kPa across the metering port, ensuring linearity between flow and valve position. Fuel entering the valve body is partially regulated through the metering port to the turbine combustor, with the excess returning to the tank via the bypass circuit.

Installation Requirements:

The valve must be firmly secured to a rigid surface that does not exceed the vibration limits specified in the detailed specifications
Connect the inlet, outlet, and overboard lines to the valve; the inlet port receives pressurized fuel from the pump, the outlet line is fixed to the fuel line(s) going to the turbine combustor(s), and the bypass line is connected back to the fuel tank
The external overboard drain (OVBD) is a vent between dual redundant shaft seals; it must be connected via rigid steel pipe to a fuel collection, purge, vent, or drain system such that it is not exposed to risk of blockage, physical damage, or back pressure exceeding 69 kPa (0.69 bar / 10 psig)
Power cable from driver to actuator must be rated for at least 90°C and 10°C above maximum fluid and ambient temperatures; resolver wiring is non-flammable and installed per appropriate methods for ordinary locations

Usage Notes:

Do NOT close the overboard drain — doing so can allow fuel to enter the LQ25 actuator, creating a hazard with potential for personal injury and/or actuator damage
Leakage above 20 cm³/min from the external drain line indicates a worn or damaged shaft seal in the LQ25 valve and must be investigated immediately; special tools are required to replace the shaft seal — contact Woodward for technical assistance
Fuel water content must be strictly controlled within 0.1% by volume to prevent internal corrosion
Periodically inspect the metering port area for abnormal wear
Driver parameters shall not be arbitrarily changed as this affects closed-loop stability
Replacement seals must use originally specified FKM parts