1.5.5.3 Freezing of the condensate in the filter and
cylinder caps or otherwise disassembling the equipment.
separator assembly during cold weather operation is
1.5.4.10 The air compressor assembly is lubricated by a
prevented by wrapping a thermostatically controlled,
combination of pressure and mist principles. The complete
electric heater blanket around the shell. The application
lubrication system includes an oil reservoir attached to the
of 27-volt direct current from an external source is
bottom of the crankcase, an oil pump cylinder mounted in
controlled by a thermoswitch attached to the base of the
the bottom of the reservoir, and oil pump piston which fits
separator shell. The thermoswitch is adjusted to close
into the cylinder and is driven by the master rod. The oil
when the shell temperature reaches 45 7Fahrenheit
level in the reservoir is shown on an indicator sight glass
and to open at a temperature of 75 5Fahrenheit.
mounted on the side of the reservoir. A drain cock located
at the bottom of the reservoir enables the oil to be drained
1.5.5.4 Three additional ports are located in the top
during periodic servicing of the equipment.
surface of the tank cap. One of the ports is not used in
this application and is sealed with a pipe plug. The
1.5.4.11 During compressor operation, oil is drawn into the
other two ports mount replaceable rupture discs which
cylinder on the piston suction stroke through holes drilled in
are designed to burst and exhaust air to atmosphere if
the cylinder wall. On the piston pressure stroke, the oil
pressure in the filter and separator assembly reaches a
inlet holes are covered by the piston, preventing the
gage pressure of 4500 to 5000 pounds per square inch
escape of oil back to the reservoir. The oil trapped in the
cylinder is forced through the hollowbore of the piston,
1.5.6 PNEUMATIC DUMP VALVE
passes through a drilled hole in the master rod, and
1.5.6.1 Condensate blow down from the filter and
lubricates the wear surfaces of the master rod and shaft.
separator assembly is controlled by a pneumatic dump
The oil thrown from these rapidly moving parts separates
valve mounted in the extruded port at the base of the
into a fine mist which fills the interior of the crankcase and
separator shell The dump valve consists essentially of a
provides adequate lubrication of the bearings, connecting
hollow body which contains a spring-loaded piston. The
links, pistons and other internal parts. Oil leakage from the
spring force is directed against the piston such that,
crankcase is prevented by the use of endbell and oil
under static conditions, a drilled passage at the
reservoir gaskets and oil seals installed at each end of the
separator end of the body is open. An adapter fitting at
shaft.
the opposite end of the body serves to restrict axial
1.5.4.12 The heat which normally results from rapid
movement of the piston and also accommodates a tee
compression of a gas is dissipated before it reaches a
fitting. One run of the tee fitting is connected to the
troublesome level by the use of finned cylinders and
outlet port of the compressor first stage cylinder; the
interstage connecting tubes. In addition, the high pressure
other run is connected to the push valve mounted on the
air leaving the third stage cylinder is routed through a
instrument panel.
finned aftercooler which is attached to the underside of the
1.5.6.2 With the compressor operating and the push
fan guard. Thus, the cooling air circulated by the fan is
valve closed, static air pressure in the line from the first
drawn past the aftercooler, then blown back past the
stage cylinder is impressed on the dump valve piston.
cylinders, interstage connecting tubes and engine.
This pressure is sufficient to displace the piston against
1.5.5 FILTER AND SEPARATOR ASSEMBLY 1.5.5.1
the spring force, thus closing the valve passage and
The filter and separator assembly consists of a hollow
preventing the blow down of high-pressure air from the
aluminum shell, or tank, with a threaded, extruded port at
filter and separator assembly. When the push valve is
one end. The opposite end of the shell is closed by a
pressed (open), the static air pressure drops to zero, the
removable cap which screws into the shell and forms an air
spring force displaces the piston to open the valve
tight seal. Three tapped holes in the cap accommodate the
passage, and high-pressure air in the separator
pneumatic inlet and outlet fittings and a pressure relief
exhausts to atmosphere, carrying with it the
valve assembly. The inlet port is cross-drilled to direct air
accumulated condensate. A metered orifice in the
directly into the shell. Outlet porting is such that air leaving
pneumatic line from the first stage outlet port restricts
the filter and separator assembly must first pass through a
the flow of control air when the push valve is open, and
cup-shaped filter element attached to the inside of the cap.
no appreciable decrease in compressor output capacity
occurs during the brief blow down periods.
1.5.5.2 High-pressure air from the compressor aftercooler
is directed to the inlet port of the filter and separator
1.5.7 PRESSURE RELIEF VALVE
assembly through a short connecting tube. As the high-
1.5.7.1 Two pressure relief valves are used in the
pressure air enters the tank, the decrease in velocity and
compressor package assembly: one valve is installed in
increase in ratio of surface area to volume cause the
the cap of the filter and separator assembly; the second
moisture and oil vapor to condense and settle to the bottom
valve is installed in the high-pressure line at the inlet to
of the shell. These impurities are removed periodically by
the receiver. The pressure relief valves are safety
opening a dump valve mounted on the extruded port,
devices which open automatically and exhaust air to
allowing high pressure air to blow the accumulated
atmosphere should pressure in the system exceed a
moisture and oil condensate to atmosphere.
value of approximately 3500 psig. The relief
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