Air Compressor

Having wide application in majorly all industry and factories, air compressors provide compressed air by converting electrical energy or power to potential energy. In simpler terms, it is a machine that extracts air from the atmosphere and compresses it into a holding chamber. The energy contained in the compressed air can be used for a variety of applications. Pressure gauge, safety valve is used for monitoring & assuring the safe operation.

Components of Air Compressor: The basic components of an air compressor are

1. Cylinder Head: The cylinder head consists of pockets for holding the intake/suction and delivery valves. They also have air cooling fins or water jacket for cooling water passage. There are usually network of pipes for cooling water and compressed air delivery to the next successive stage.
2. Piston and Cylinder wall: The piston moves inside the cylinder wall or the liner, reciprocating up and down. The liner supports and guides the piston, forming a main part of the air compression chamber.
3. Intercooler and After cooler: The intercoolers and the after coolers are usually mounted on the body of the compressor allowing the hot compressed air to exchange its heat with the forced circulation water. Some air compressors are cooled by forced circulation of ambient air itself.
4. Suction Filter: Filter is usually mounted onto the cylinder head allowing filtered air to enter compressor unit.
5. Engine: air is compressed by pulling in atmospheric air, reducing its volume and increasing its pressure.
6. Storage Tank: Storage tank is used to hold the pressurized air & it releases the air as per requirement.
7. Inlet and Outlet Valve: Inlet valve allows air into the machine to be compressed as the piston pushes upward and keeps the inlet valve shut, which in turn opens the discharge valve which allows the air taken in through the inlet to be compressed.

Working of Air Compressor:

1. Valve head helps in sucking the air in from atmosphere due to the movement of piston in cylinder in downward direction
2. While piston moving up, the air get pressurized and air is compressed.
3. This increase in pressure forces the discharge valve to open leading to its movement into the storage tank.
4. Continuous movement of piston in upward and downward direction leads to increased pressure in the tank.
5. Motor shuts down once the pressure reaches the higher limit and starts working when the pressure reaches lower limit, making the cycle continuous.

Types and Method of Air Compressor:

Method of air compression for air compressors are dynamic displacement and positive displacement.

1. Positive-displacement compressors: Forces air in a chamber and volume of chamber is decreased to compress the air. Once the maximum pressure is reached, outlet valve opens and air is discharged into the outlet system from the compression chamber. Example of such air compressors are reciprocating and rotary type.
2. Reciprocating type-uses pistons driven by a crankshaft to deliver gases at high pressure. It is of two type

• Single Stage/Single Acting– Air is drawn in and compressed on one side of the piston. In this case, the downward stroke of the piston draws in the air, and the upward stroke compresses it.
• Multi Stage/Double Acting-It has compression chambers on both sides of the piston. On the down stroke, air is drawn in on the top of the piston while air is compressed on the bottom side. On the upstroke, air is drawn into the bottom side while air is compressed on the top side.

1. Rotary air compressors: Pump works in cycles. Over each cycle a volume is created in contact with the chamber where pressure is to be lowered. By motion, molecules from the vacuum chamber pass into the volume created by the pump.

• Root blower compressor: This is a positive displacement lobe pump which pumps fluid with a pair of meshing lobes. It consists of two rotors with lobes rotating in air tight casing. The casing has inlet and outlet parts on opposite sides.
• Screw Compressor: It is a type of gas compressor using rotary-type positive-displacement mechanism. There are two meshing helical screws, known as rotors, to compress the gas. The meshing rotors force the gas through the compressor, and the gas exits at the end of the screws.

2. Dynamic displacement: Centrifugal compressorsand axial compressors are employed in such compressors. A rotating part imparts its kinetic energy to the air which is eventually converted into pressure energy.
3. Axial air compressor: To produce large air flow, they have set of fan blade. The axial compressors are largely used for ventilation and as part of air processing.
4. Radial air compressor: They draw in air to the center of an impeller, and then accelerate it outward toward its perimeter. There it impinges upon a diffuser plate and outlet scroll, where velocity decreases and pressure increases.

Good suppliers of Air Compressors include Atlas Copco, Kaeser, Ingersoll Rand, Elgi, etc.