Air Compressors: Introduction

Introduction Applications
Power Types
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Air Compressor is a machine for increasing the pressure of a air by mechanically decreasing its volume (i.e. by compressing it).

This compressed and pressurized air when released in quick bursts powers whatever mechanism to which the air compressor is attached.

Air compressor thus converts power (usually from an electric or diesel or gasoline engine) into kinetic energy in order to produce a desired motion.

Air is the most frequently compressed gas, but natural gas, oxygen, nitrogen, and other industrially important gases are also frequently compressed for various applications.

Air compressors collect and store air in a pressurized tank, and use pistons and valves to achieve the appropriate pressure levels within an air storage tank that is attached to the motorized unit.

Compressors vs Pumps: Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. As gases are compressible, the compressor also reduces the volume of a gas. Liquids are relatively incompressible, while some can be compressed, the main action of a pump is to pressurize and transport liquids.


Did you know that the air you walk around in, and breathe, is already compressed? The pressure generated at sea level by the weight of the air above itself generates 14.7 PSI of pressure.

PSI stands for pounds per square inch. (1 PSI = 14.50 bar; 1 bar=1 kg /sqcm)

An air compressor takes free air (air at 14.7 PSI actual) into an intake port, and using mechanical means (pistons, screws, rotary sliding vanes) pushes that air into a smaller area. As more and more air is pushed into the smaller area (the receiver or the air tank on a compressor) the pressure continues to increase inside that tank.

There is a pressure switch which monitors the air pressure inside the tank. When the air pressure reaches the high pressure level setting, the compressor shuts off.

Compressing Air Converts Energy

Compressed air is able to do work because as you compress air you transform one form of energy into another form of energy which you then store for later use.

This energy form, compressed air, is now at imbalance, in that you have an area of high pressure in a compressor receiver surrounded by an area of lower pressure; the atmosphere.

Mother Nature doesn’t like imbalance in her systems. And that you have a container – an air tank, a receiver, an air-hog or a plant air main filled with compressed air at 120 PSI or so, bothers her.

She wants that air to be back at a nice, comfortable, 14.7 PSI – that being the pressure of the atmosphere. And she wants it right now!

That drive to achieve balance in nature – that is, to get the compressed air from an area of high pressure back to atmospheric pressure, means that when you open the valve on the tank or air line, air will move at almost the speed of sound as it rushes to try to get back to 14.7 PSI, that one atmosphere at sea level.

By controlling this flow of air, and directing it into tools that in themselves can perform work, then you can extract work from the compressed air energy as it decompresses back to atmospheric levels.

And we have. Over the years, mankind has learned how to use this high-to-low pressure flow of air to do work for us via specialty nozzles, air tools, air actuators, air motors, and so on. Compressed air really is a neat way to store and use energy.

When someone uses compressed air from the tank, the air pressure inside the tank will start to fall. When it reaches the pressure switch low pressure setting, it turns the compressor back on until the pressure inside the tank again reaches the high set point.

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We thank for permitting the use of information available therein for preparation of this article.