Air Compressor
A machine that compresses air. There are several types of air compressor each of which uses
in a different method to compress the air.
Reciprocating / Piston - These are positive displacement machine. A piston in a cylinder increases
the pressure of the air by reducing its volume. By repeating this with successive volumes of air, the
resulting air which is held in a closed space increases in pressure. They are either air or water cooled and
can be lubricated or lubrucation free.
Rotary Screw - These are positive displacement machine. Two elements within a casing rotate and
compress the air internally. There are no valves and they are generally oil cooled (with an air or water
cooled oil cooler). Oil free screw compressors are air or water cooled. Screw compressors are easy to maintain
and operate and quieter than reciprocating compressors.
Centrifugal / Vane - These are dynamic displacement machine which relies on the transfer of energy from
rotating vanes to the air. They produce high pressure discharge by converting angular momentum imparted by the
rotating vane. To do the efficiently the vanes must rotate at high speeds. They are oil free compressors although
the running gear is oil lubricated.
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