Compressed air explained

Why Do We Need It?

Compressed air is often described as the fourth utility, although not as ubiquitous as electricity, petroleum products and gas, it plays a fundamental part in the modern world. The main difference is that users generate their own air and so have a choice in the way that air is generated.

The importance of compressed air is often over looked, but it plays a vital part in most modern manufacturing processes and modern civilization. Although we may not realize it most products we use today could simply not be made without compressed air. Compressed air accounts for about 10% of the global energy currently used in industry.

With so many applications in different environments being dependant on pneumatic air, compressors must compress the air to a specific pressure, at a certain flow, and deliver air of the right quality. To most people, a compressor is all that is required to compress air, but to obtain the right quality of the compressed air, more equipment is often needed. Filters and dryers are required to remove oil and water before it reaches the application. Some compressor manufacturers have a range of completely oil-less compressors, in which the air itself contacts the application and so the quality is critical. For example, where a compressor is used in a food packaging role.

What happens when we compress air?

Compressed air is clean, safe, simple and efficient. There are no dangerous exhaust fumes or other harmful by-products when compressed air is used as a utility. It is a non-combustible, non-polluting utility.

When air at atmospheric pressure is mechanically compressed by a compressor, the transformation of air at one bar (atmospheric pressure) into air at higher pressure (up to 414 bar) is determined by the laws of thermodynamics. They state that an increase in pressure equals a rise in heat and compressing air creates a proportional increase in heat. Boyle’s law explains that if a volume of a gas (air) halves during compression, then the pressure is doubled. Charles’ law states that the volume of a gas changes in direct proportion to the temperature. These laws explain that pressure, volume and temperature are proportional, change one variable and one or two of the others will also change, according to this equation:

Pressure Lawpressure-law

When applying this to a compressor, air volume (or flow) and air pressure can be controlled and increased to a level that suits the way it is being used. Compressed air is normally used in pressure ranges from one to 414 bar (14 to 6004 PSI) at various flow rates from as little as 0.1m3 (3.5 CFM – cubic feet per minute) and up.

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