Woodward SonicFlo™ Gas Fuel Control Valve With Electric Trip

Trip Relay Valve Assembly

The SonicFlo™ valve uses a solenoid-operated trip relay circuit to operate a high capacity, three-way,

two-position, hydraulically operated valve. This trip relay circuit consists of four functional elements: the

trip relay solenoid valve, the trip relay supply orifice, the hydraulically operated trip valve, and the trip

relay volume.

In the normal run mode, the trip relay solenoid valve is closed, which prevents the trip relay volume from

bleeding to the hydraulic return. As a result, high-pressure oil is fed into the trip relay circuit through the

supply orifice, which quickly pressurizes the trip circuit to supply pressure. When the trip circuit pressure

increases above 1100 kPa (160 psig), the three-way relay valve shifts position so that the common port

connects the control port of the servo-valve to the lower piston cavity of the actuator, allowing the servo

valve to position the throttle valve.

The solenoid valve opens when it is de-energized. Opening the solenoid valve causes the trip circuit to be

connected to drain. This in turn causes the three-way relay valve to shift position so that the common port

is connected to the hydraulic drain circuit, and isolated from the hydraulic supply. As the pressure falls

within the lower piston cavity, the return spring rapidly returns the valve plug to the downward position,

closing the control valve and shutting off fuel to the engine.

Hydraulic Filter Assembly

The valve is supplied with an integrated, high-capacity filter. The broad range filter protects the internal

hydraulic control components from large oil-borne contaminants that might cause the hydraulic

components to stick or operate erratically. The filter is supplied with a visual indicator which shows when

the recommended pressure differential has been exceeded and thus replacement of the element is

necessary.

LVDT Position Feedback Sensors

The SonicFlo control valves use a dual-coil, dual-rod LVDT for position feedback. The LVDT is factory set

to give 0.7 Vrms feedback at minimum position and 3.5 Vrms feedback at maximum position, when

supplied with 7 Vrms excitation at 3000 Hz.