valve opens, the compressed air escapes into the
the end of its compression stroke, the air pressure is
interstage connecting tube and is routed to the
sufficient to overcome the spring force holding the
compressor third stage where the compression cycle is
exhaust valve against the valve plate, and the
repeated and the air raised to its ultimate delivery
compressed air escapes through the outlet ports and
pressure.
flows through the interstage connecting tube to the inlet
port of the second stage cylinder.
1.5.4.8 The strainer and relief valve assembly installed
in the inlet port of the second stage cylinder normally
1.5.4.5 The intake valve mechanisms of the second
serves only to strain the interstage air.
and third compressor stages each consists of a port in
the side of the cylinder, holes drilled through the walls of
the piston, and a poppet fitted into the forward end of
NOTE: Model 3800219 has a 3rd stage strainer and
the piston. The exhaust valves are hardened steel
relief valve assembly.
discs, carefully ground and lapped to seat against a
lapped shoulder at the end of the cylinder bore.
However, should air pressure within the elbow body
Compression springs installed between the valves and
exceed a predetermined value, the spring-loaded
the cylinder normally maintain the valves seated against
poppet is forced away from its seat, and air escapes to
the shoulders.
atmosphere through the drilled hole in the spring
adjusting plug.
The poppet reseats automatically,
1.5.4.6 Compressor timing is such that the second
preventing further escape of air, when the internal
stage piston is moving toward the crankcase and
pressure drops to the normal operating level.
approaching the bottom of its stroke when compressed
air is exhausting from the first stage cylinder. This
1.5.4.9
Additional protection against inadvertent
compressed air enters the second stage cylinder through
overpressurization is provided by rupture discs installed
the strainer and relief valve assembly installed in the
in the second and third stage cylinder caps.
inlet port, flows through the holes drilled in the piston,
forces the poppet open, and fills the area of reduced
The rupture discs, mounted in ports drilled through the
pressure in the cylinder bore between the piston and the
cylinder caps, are designed to burst and exhaust air
exhaust valve. When the piston reverses direction, the
directly to atmosphere in the event of a sudden rise in
poppet valve is forced closed and the air trapped in the
pressure within the cylinders.
forward end of the cylinder is compressed by the
advancing piston.
NOTE: Model 3800219 does not use a rupture disc
in second stage cylinder cap.
1.5.4.7 As the second stage piston approaches top
dead center, the pressure of air compressed in the
The rupture discs can be replaced without removing the
cylinder becomes sufficient to override the spring force
holding the exhaust valve closed. When the exhaust
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