What Does A Compressor Do And Its Types?

  What is a compressor?

In order to understand "what does a compressor do?". At first, we need to understand what a compressor is? Well the answer to this question is not possible in a few words because it offers a wide range of applications.

The compressor is a a device that supplies air at high speed. To have an idea for "what does a compressor do?" remember a machine that you might have seen at homes for cleaning the floor or at garages for carrying out a tire inflation jobs

Yes, these machines are compressors. The high air pressure created by compressors makes its use in a wide variety of applications. The compressor offers a vast use that ranges from homes to industries. There are many different types of compressors with different applications and sizes (20 gallon, 30 gallon, 60 gallon). 

A compressor typically consists of an engine, the inlet and outlet valve, crankshaft, pistons or impellers, and, tank for storing compressed air.

  How do air compressors work?

The working principle of a compressor is very simple. The mechanical energy generated by the motors or impellers to compress the air.

That energy is imparted to fluid and the fluid gains high pressure and velocity.

It takes the atmospheric air through the inlet valve and gets inside by passing through a filter to remove dust and dirt. The air is then compressed through either helical rotors or piston or impellers.

The compressed air is then discharged through an outlet and stored in a tank.

  Types of compressors:

Based on air displacement, there are two types of compressors.

  1. The Positive displacement compressors
  2. The Dynamic displacement compressors

1). Positive Displacement compressors

Positive displacement pumps use mechanical energy to transfer fluid. These pumps are capable of delivering very high pressures. These pressure can exceed the required pressure limit.

Therefore, the relief valves are used to control the pressure. The positive displacement compressors are further categorized into two types.

  • The Reciprocating compressors
  • The Rotary compressors.

i). The Reciprocating compressors:

The compressors that use pistons as the compressing elements are called the reciprocating compressors. It consists of a housing and an internal piston connected to a crankshaft. The piston moves up and down with the help of crankshaft.

The downward stroke of the compressor is called the suction stroke and the upward stroke is called the compression stroke. On suction stroke, the volume increases within the cylinder and pressure become lower pressure inside than the inlet pressure.

The higher pressure forces the inlet to open and draw more air into the cylinder. With the upward stroke the volume of the cylinder decreases, the air is compressed and the inside pressure is increased. The increased pressure forces the outlet valve to open and discharge the compressed air

The reciprocating compressors may be single staged or two staged compressor.

  • Single Stage Compressor

The single stage compressors have only one piston and cylinder and they compress the air in only one stage. They have output pressure from 50 to 75 PSI.

During compression the air becomes too hot that reduces the compressor efficiency and there is a chance of explosion as well therefore the manufacturer have introduced a two stage compressor to overcome this problem.

  • Two-Stage Compressor

To overcome the problem of overheating and still generate high pressure, the manufacturers make compressors with multiple stages.

The first stage is used to compress the air then the air is cooled as it travels trough a tube exposed to flywheel fan. The cooled air then enters the second stage where it is further compressed. They can operate up to 175 PSI.

ii). Rotary compressors:

The compressors that use impellers or veins are called a rotary compressor. They consist of a cylindrical housing with adjustable rotary veins, an inlet, and an outlet. The veins are on an off center drive shaft. These veins form compartments of different sizes.

The air gets inside through the inlet. As the veins move the size of compartment reduces and the air is compressed with the reduction in compartment size. The compartment size becomes sufficiently reduced when it reaches the outlet and air is in a highly compressed state.

2). Dynamic displacement compressors

The dynamic displacement compressors use the mechanical energy driven by the motor and impeller and this energy is consumed in increasing the pressure and kinetic energy of the fluid and they create pressure at the outlet.

Centrifugal pumps:

Centrifugal pumps are the most preferred pumping devices in the hydraulic world. The heart of centrifugal pump is an impeller that has got a series of curved valves . When the impeller is made to rotate the fluid surrounding it also rotates.

This imparts a centrifugal force to fluid particles and they move radially outward. Since rotational mechanical energy is transferred to the fluid at the discharge side both the pressure and kinetic energy will rise. The fluid moves in the same direction of rotation as the impeller to the discharge port.

  Applications of Compressors:

i). At home:

The compressors are vastly used for household needs and they may be used for maintenance tasks. Further, you can use it to clean your home. With the fast blow off the air it is easy to clean dust and you can use it as a floor dryer as well after washing the floor. 

It can also be used to inflate the kid's toys at home and other inflatables like swimming accessories or sports balls. Further, if you need to paint your home, you can use your air compressor for this purpose. Usually, the compressors used at home are low power reciprocating style compressors.

ii). In Automotive:

Air compressors are widely used in garages for cars, bikes, or heavy vehicle tires Usually, small, portable, and cordless compressors are used by car and bike owners. 

The inflators used for small or mid-size cars are low power and can't be used for heavy vehicles like truck tires. You should choose the compressor according to the loading capacity of the vehicle.

iii). In industries:

The compressors offer, a wide range of applications at the industrial level. They are used in the food and beverage industries, pharmaceutical, agricultural, and textile industries.

Let's have a look at the details of its application in these areas.

  • Agriculture Industry

The field of agriculture is also well mechanized and may need compressors to power agricultural machinery like dairy machines, spraying crops, and powering pneumatic tools used in agriculture.

  • Textile Industry:

The compressors are also well used in dry cleaning in garments and textile industries. The cleaning guns, laundry presses, and, stream cleaners are powered by air compressors.

  • Pharmaceutical Industry:

The compressors used in the pharmaceutical industry are oil-free. During the manufacturing of a drug, the pneumatic power is required at many stages. Also, the production of nitrogen is achieved with its help.


We have seen the functionality, types, and, applications of different kinds of compressors and got the answer to "what does a compressor do?" Undoubtedly, the compressor is a very useful device for everyone. It makes many of your tasks easier like inflating car tires.

It eliminates the need to visit the garage and saves money. Further, you can use it for maintenance, painting, and, cleaning. It can be used in the home, garage, and, shops.

There are two basic types of compressors based on the basis of air displacement and five different types based on differences in the compression technique and compressing elements.

The compressing element commonly used are pistons, screw, and impellers. We have to know their working and applications to become familiar with "what does a compressor do?"

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