Figure 1-5. Pneumatic System Schematic Diagram (Model 3800219-1)
valve reseals (closes), preventing the further escape of
outlet port of the filter and separator assembly, consists
air, when the pressure drops to about 3200 psig.
basically of an aluminum alloy valve body provided with
an inlet fitting, an outlet fitting and an adjustable valve
1.5.7.2 The pressure relief valve assembly consists of a
cap. A drilled passage connecting the inlet and outlet
cylindrically shaped, aluminum valve body which
fittings contains a piston seat and a spring-loaded
contains a spring-loaded piston, a ball-type valve, a
piston. The setting of the valve cap determines the
stem and an adjusting screw. Under normal pressure
force which the spring exerts to maintain the piston
conditions, the ball is seated against a nylon washer, or
seated against the piston seat (i.e., valve closed).
seat, installed in the bore of the piston, and no air
escapes through the assembly. However, when air
1.5.8.2 The piston of the back pressure valve is held
pressure in the system increases above a
against the piston seat, preventing the flow of air from
predetermined value, the spring-loaded piston and the
the filter and separator assembly, until the pressure in
ball are displaced until the ball rests against the end of
the separator shell reaches a predetermined value.
the stem which extends into the piston bore. A further
When air pressure at the inlet of the back pressure
increase in pressure causes additional displacement of
valve is between 2450 and 2650 psig, depending on the
the piston, unseating the ball and allowing air to escape
back pressure at the outlet fitting, the piston is forced
to atmosphere through the bore of the piston and holes
away from the piston seat, compressing the spring.
drilled in the adjusting screw. When air pressure in the
Opening of the drilled passage through the piston seat
system is reduced to an appropriate level, the spring
allows high-pressure air to flow from the filter and
force moves the piston toward the ball, closing the valve
separator assembly through the back pressure valve.
passage and preventing the further escape of air.
When air pressure in the filter and separator assembly
drops to approximately 2000 psig, the spring forces the
piston back against the piston seat, effectively closing
1.5.8 BACK PRESSURE VALVE
the back pressure valve and preventing the further flow
of air.
1.5.8.1 The back pressure valve, mounted or. the
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