PRESSURE REGULATOR AND RELIEF
VALVE. This valve (fig. 1-9) converts the
uncontrolled bleed air to a regulated air pressure
of approximately 18 psi and routes it to the three
distributor valves and the pressure gage.
The combination valve is basically separate
regulator and relief valves with the two valve
bodies brazed together. A sensing line allows air
downstream of the valve to be ported to the
diaphragm in the valves regulating chamber.
As pressure builds up downstream, the
diaphram raises, compresses the regulating
spring, and raises the inlet valve toward its seat.
When the predetermined outlet pressure is
reached, the inlet valve is fully seated, shutting
off the flow of bleed air through the valve. When
the downstream pressure drops below the
regulator setting, it reduces the air pressure under
the diaphragm and the regulating spring forces
the inlet valve off its seat, allowing inlet air to
restore the system operating pressure.
The relief valve section of the valve is held in
the seated position by spring pressure until the air
pressure in the outlet port exceeds a predetermined
In the event that the regulator diaphragm
ruptures or the regulating portion of the valve fails
for any reason, the relief valve can function as
a pressure regulator as well as a relief valve to
temporarily protect the downstream deice system
components from excessive pressure.
EJECTOR. The ejector unit consists of a
pressure port, a venturi, an overboard port, and
a suction port. As air pressure from the pressure
manifold enters the inlet. pressure port, it creates
Figure 1-9.Deice system pressure regulator and relief valve.