Compressed Air Basics Part 1: The Fourth Utility

This will be the beginning of a series on the basics of compressed air.  We will begin on why compressed air use is so common and its benefits.

Compressed Air is often called "The Fourth Utility" because it an essential element to millions of businesses around the world.  However, unlike your electricity, water and gas utilities, your compressed air system is something you have complete control of.

Compressed air is the energy of choice to power a great variety of applications. Sanders, grinders and paint guns in automotive service shops, presses and accessory equipment in dry cleaning stores and commercial laundries all depend on a reliable supply of compressed air. Theme parks depend on compressed air to run roller coasters, fountains, and animated characters. Construction and road crews use compressed air to power jackhammers and repair our roads.  Manufacturers use air compressors to run their equipment.  Every hospital has an air compressor for medical air and sometimes for climate control.  Power companies use them for engine starting.  Universities use compressors for lab air.  Bottling companies use compressed air to make the plastic bottles that you drink out of.  Compressed air in the tires of your car.

Compressed air is everywhere.

The reasons why compressed is so widely used include:

• Compressed air can be easily stored for its intended purpose, using storage tanks located in places where no other power is available or practical.
• Compressed air can be used where other energy sources cannot be used due to explosion hazard or fire risk.
• Equipment operated by compressed air can function at extreme temperature.
• Compressed air can have a high degree of cleanliness, where quality, hygiene and safety are essential.
• Compressed air can be stored in bottles and used where no pipe system exists.
• As a power source, compressed air does not interfere with electrical monitoring equipment.
• Air tools are often much lighter than the equivalent electrical models, making them easier for an operator to handle.
• Air tools are ideal for challenging applications such as in steel mills and foundries where the conditions are almost destructible; however, with periodic maintenance the tools can continue to run at their peak efficiency.

Compressed air has been used by man since at least the 3rd Century BC.  The Greek inventor Ctesibius used compressed air in an alarm clock and in a cannon that shot arrows.  His protege, Hero, used it to open the gates at the Temple of Alexandria.

So what is compressed air?

Compressed air is simply atmospheric air under pressure.  That pressure is energy stored in the air, and now that energy is available to do work.

There is a relationship between volume, pressure and temperature:

You can see that as volume decreases, both pressure and temperature increase.  So what air compressor does is take in ambient air and decrease its volume, which creates a rise in pressure and a rise in temperature.

This pressure is either used immediately to do work or stored in tanks for future work. There are many different types of compressors that use various methods to compress the air.  We'll go over the different types next week.