Miscellaneous Mechanical Components
Air Compressors Summary (Cont.)
The centrifugal force utilized by the centrifugal compressors is the same
force utilized by the centrifugal pumps. The air particles enter the eye of
the impeller. As the impeller rotates, air is thrown against the casing of
the compressor. The air becomes compressed as more and more air is
thrown out to the casing by the impeller blades. The air is pushed along
the path on the inner wall of the casing. The pressure of the air is
increased as it is pushed along this path. There could be several stages to
a centrifugal air compressor just as in the centrifugal pump, resulting in
Rotary compressors are driven by a direct drive that rotates a mechanism
(impellers, vanes, or lobes) that compresses the air being pumped. The
actual compression of the air takes place due either to centrifugal forces
or a diminishing air space as the impellers rotate.
Cooling systems are required in compressed air systems to remove any
heat added by the compression. The advantages to cooling the compressed
air are that cool air takes less space and holds less moisture. This reduces
corrosion and allows more air to be compressed into a given volume.
Hazards associated with compressed air are similar to hazards of any high
pressure system. Three general hazards include the following.
Small leaks or breaks can cause minute particles to be blown at speeds
high enough to cause damage. Goggles or safety glasses should be worn
when working around compressed gas.
The compressors, especially larger ones, can be quite noisy when running.
The cycling of automatic drain valves contributes noise as well. Hearing
protection should be worn around compressors.
Pressure swings may cause system damage.
Closed valves in a
compressed air system should be slowly cracked open and the pressure
should be allowed to equalize prior to opening the valve further. Systems
should be depressurized prior to opening for maintenance. Oil should be
kept out of air systems to prevent possible explosions.