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OPERATION
Operator Controls
The unloader valve for the operation of the gasoline
compressor outfit is located between the compressor
pump and gasoline engine. The air discharge valve
can be located on the end of the air tank. The safety
valve and pressure gauge are attached to the tank
below the unloader. See page 7.
Unloader Valve
Pressure loads beyond the design limits
may cause tank rupture or explosion. Do
not attempt to adjust, remove, or defeat
the unloader valve, or change and modify
any pressure control device. If replace-
ment is necessary, the same rated valve
must be used.
Figure 6. Unloader Valve
The unloader valve, Figure 6, is controlled by tank pres-
sure. Compressors with unloaders run continuously
and maintain air pressure within set limits. At maxi-
mum tank pressure the unloader valve opens and the
compressed air is exhausted to atmosphere. This
prevents the compressor from continually building more
pressure if air is not needed. When the tank pressure
drops to a predetermined minimum pressure, the
unloader valve closes and the compressor again builds
up the tank pressure. Pressure continues to build un-
til maximum tank pressure is achieved. The cycle
then repeats itself.
The unloader is used because frequent start-ups and
stops are impractical with a gasoline engine. The
unloader valve is preset at the factory. Never attempt
to make adjustments to the unloader valve.
The toggle lever on the front of the unloader valve should
be pulled out or in the horizontal position when start-
ing up the compressor. This prevents the compressor
from starting under load. Once the engine has reached
full throttle, the lever should be pushed to the side,
returning it to its original position to allow the com-
pressor pump to build pressure in the air tank.
PAGE 11
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