Air Compressors. Air compressors, shown in
figure 9-14, are portable sources of compressed air.
They are self-contained and mounted on a two or four
wheel trailer frame.
Purpose. An air compressor is designed
to continuously deliver a rated volume of air at a rated
pressure. Depending upon the flow (rated in cubic feet
per minute or cfm) and the pressure (rated in pounds
per square inch or psi), an air compressor provides air
for the following uses:
· Operation of pneumatic tools, greasing
equipment, paint spray guns, and for tire
· Supply air to charge aircraft pneumatic systems,
hydraulic accumulators, oleo struts, and tires,
and for servicing the trailers that will be used for
Types. Air compressors are typed by the
maximum flow and pressure they can produce.
Generally, the low pressure compressors provide up to
175 psi and are used for pneumatic tools, spray guns,
greasing equipment, and so forth. The high pressure
compressors produce pressures of 3,000 to 3,500 psi.
accumulators, struts, and pneumatic systems on aircraft.
The external appearance of types may vary by model
number or manufacturer. The air compressors shown in
figure 9-14 are typical of those found in maintenance
Principles of operation. Air compressors
have a gasoline engine which drives the compressor,
either by a belt or through a clutch. The compressor has
low and high pressure cylinders. Air is drawn into the
low pressure cylinder through the air filter and delivered
to the high pressure cylinder through the intercooler
coils. The compressed air then goes through a check
valve to the receiver tank. The check valve prevents
Safety practices and procedures. The
following special precautions should be observed when
using air compressors:
· Do not use low pressure hoses (300 psi) on a
high pressure compressor (3500 psi).
· Do not use the air compressor in an enclosed
· Do not try to override or defeat the pressure
· Do not refuel the compressor when the engine is
· Leave all safety devices (e.g. belt guard)
Operating procedures. Consult the
applicable maintenance manual for the type and model
air compressor being used for specific instructions. The
following general procedures pertain to the operation of
the air compressor:
Locate the compressor near the
Set the brake.
Open the siphon valve on the
receiver and close the shutoff valve on the control
Start the engine.
operating pressure, open the shutoff valve.
Adjust the pressure as required and
use the compressor.
For shutdown, close the shutoff
valve and position the ignition switch to off.
When the engine stops, open the
siphon valve and drain the water accumulation.
operator inspections apply to air compressors. Detailed
inspection requirements are found in the applicable
Liquid levels. Check the engine and
compressor oil levels, gas tank fuel level, and battery
electrolyte level. Service as needed.
Hand or parking brake. Check for
Hoses. Look for wear or loose