Compressor Terminology is nothing but the small words used to describe some engineering functions. Before taking up the actual study of air compressors one must know the important terms which are frequently used.
You have to know these Compressor Terms because they are the fundamentals of air compressor technology.
One who is interested in reciprocating air compressors must always remember the following Compressor Terminology.

Important Compressor Terminology
Air Compressor
This is the machine that is used to increase the pressure of air by reducing its volume.
Reciprocating Air Compressor
This is a machine that compresses air by means of a piston reciprocating inside the cylinder bore.
Single Acting Compressor
This is a machine that compresses air in only one end of the piston and cylinder.
Double Acting Compressor
This is a machine where the air is compressed at both ends of the piston and cylinder.
Single Stage Compressor
This is a machine in which air from atmospheric pressure is compressed up to desired discharge pressure in a single operation (stage).
Two-Stage Compressors
This is a machine in which air from atmospheric pressure is compressed up to the desired pressure in two stages.
In the first stage, the air is compressed to an intermediate pressure & in the second stage; it is further compressed to desired discharge pressure.
Multistage Compressors
This is a compressor in which air is compressed from atmospheric pressure to desired pressure in more than two stages.
Rotary Compressor
This is a machine in which the compression is effected by a rotating vane or impeller that imparts velocity to the flowing air to give it the desired pressure.
Inlet Pressure
This is the absolute pressure of the air at an inlet (Suction) to a compressor.
Discharge Pressure
This is the absolute pressure of the air at an outlet (delivery) of a compressor.
Compression Ratio
This is the ratio of the absolute discharge pressure to the absolute inlet pressure.
Free Air Delivery (FAD)
Free air delivery is the volume of air delivered under the conditions of temperature and pressure existing at the compressor intake.
This generally takes 1.0332 kg/cm² abs & 15-degree centigrade, if an air conditioner is not given.
Capacity of Compressor
Capacity is the volume of air delivered by the compressor. It is generally expressed in cubic feet/min. or meter cube/ min.
Theoretical Horse Power
This is the horsepower required to compress adiabatically the air delivered by a compressor through a specified pressure range, without any provision for lost energy.
Brake Horse Power
BHP is the actual horsepower input required by a compressor.
Compressor Efficiency
This is the ratio of theoretical horsepower to the brake horsepower.
Volumetric Efficiency
This is the ratio of the capacity of a compressor to the piston displacement of the compressor.
Shall I hope, the above compressor terminology helps you to understand the topic?
Besides this information, you are suggested to read something more from below engineering books
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