A compressor is a machine that is able to increase the pressure of a gas by using mechanical energy. This tool differs from the pump in that it is able to act on a fluid which is compressible. Depending on the operation, the compressors can be divided into two categories, volumetric and dynamic. The former have mechanisms that adequately compress the gas. In the volumetric compressor, on the other hand, compression occurs due to the speed that is able to impart to the body and to the energy produced by the variation of the moment of momentum. The dynamic compressors then compress the gas using the kinetic energy that is provided by particular mechanisms. Usually they are composed of a wheel equipped with blades which supplies the energy necessary to increase pressure. On the market there are many different models with characteristics that also differ according to the use that will have to be made of them.
The volumetric compressor is a device that is capable of sucking in gas independently of the conditions that can be found both on the suction and on the delivery. Therefore operation does not depend on the pressure that can be found upstream or downstream of the device. Volumetric compressors have a flow rate which is usually proportional to the rotation speed, while the compression ratio generally does not depend on it. There are different types of volumetric compressors, divided according to operation. Reciprocating compressors provide the aspirated gas with an increase in pressure by means of a piston that moves inside a cylinder in an alternating way. Reciprocating compressors are usually driven by an electric motor, much more rarely, however, by an internal combustion engine.