as the volume decreases between the turning mated
rotors. Compression is completed as the air is passed out
of the discharge end of the twin-bore cylinder. The
process is continuous as long as the rotors turn; thus we
have an extremely smooth flow of compressed air. As
with the vane type of unit, compressor oil is injected into
the twin-bore cylinder and picked up by the mating
rotors. The oil serves to seal the rotor surfaces and to
cool the air in its compression stages. The oil that mixes
with the air during compression is passed into a receiver
separator where it is removed and returned to the oil
COMPONENTS OF COMPRESSORS
Air compressors consist of basic systems and
components such as the air filter, the air control system,
the compressing element, and the air receiver and
lubrication systems. Other components are safety
devices, cooling systems, and air/oil separators. These
systems and components allow the air compressor to
perform its design function efficiently and safely. The
following sections detail the purpose of these different
components and systems, and their relationship to
efficient air compression.
SAFETY DEVICES OF COMPRESSORS
Air compressors have automatic safety control
devices that shut the unit down in the event of a
Figure 8-9.Typical pressure release valve.
Safety devices on air compression systems
are not to be bypassed FOR ANY REASON.
Engine overspeeding, overheating, low oil pressure,
and low or high fuel pressure are all reasons for the
prime mover to be shut down. These safety devices are
placed on the power source to protect it.
On the compressor, a pressure release (safety relief)
valve (fig. 8-9) releases excess air pressure to protect
personnel, the compressor, tanks, and piping from
damage if the air pressure exceeds the design limits. The
safety valve is mounted in plain view on the air receiver
and is normally set at 125 psi (special-duty air
compressors may have different psi settings). The
Figure 8-8.Example of airflow through a screw type of air compressor.