Compressed air is mainly used to operate machinery, processes or equipment. Compressed air is air, which has been put under greater pressure than the air in the general environment. It is one of the most expensive of all services to be provided, but in contrary is regarded as free and often ignored when it comes to conservation. Significant energy and eventually cost can be saved by efficient and sensible generation & utilization of compressed air.

The compressed air system normally consists of various subsystems and equipment such as:

• Air compressor with air filters, inter coolers, after coolers, dryers, oil and moisture separators
• Lubrication and cooling water system
• Air receivers with safety valve, pressure gauge and drain valve
• Motor and drive transmissions
• Distribution system comprising piping, valves, non-return valves, pressure regulators, lubricators, flow meters, couplings and bends
• End use equipment such as pneumatic drills & presses and spray guns.

2 Types of Compressors

Broadly air compressors are mainly classified into two types. This classification is based on their construction and operation. Types that are commonly used are described below:

Positive displacement compressors mechanically displace a fixed volume of air into a reduced volume. They will deliver a nearly constant volume, when operated at a fixed speed; while the discharge pressure is determined by the system load conditions.

Dynamic compressors mechanically impart a velocity to the air, through the use of impellers rotating at high speed, in an enclosed housing. The air is forced into a progressively reduced volume. The volumetric flow will vary inversely with the differential pressure across the compressor.