This dual pressure valve regulates the bleed air pressure
at 44 ƒ 5 psig when operating the engine above 400 shaft
horse power (shp) or at a maximum of 16 ƒ3 psig when
operating the engine below 400 shp.
Power is removed for
this valve 10 seconds after startup.
To open the prioritization regulating valve, the air goes
through the self cleaning filter, the high reference
regulator, and then the energized high differential
solenoid.
The air pressure then passes through the de-
energized shut-off solenoid to chamber A.
This valve
requires a pressure of 44 ƒ5 psig to move the valve toward
the closed position.
When the engine drops to 400 shp or below, the high
pressure solenoid de-energizes and the air pressure must
then pass through the low reference regulator.
The low
reference regulator reduces the reference pressure, thereby
reducing the pressure required in chamber B to move the
valve toward the closed position, and regulates the
pressure downstream at 16 ƒ3 psig.
If the cutoff solenoid fails to energize,
the valve opens when applying air pressure. With the dual
pressure valve, if the high differential solenoid fails to
energize, the valve regulates pressure at 16 ƒ3 psig only.
Figure 1-5.
Prioritization Regulating Valve Schematic.
9
OD1705
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