Piston compression, also known as a reciprocating compressor, is a positive displacement compressor that employs the use of a piston, which moves inside the cylinder. It is driven by a crankshaft to deliver gases at high pressure. To prevent the gas from turning into liquid, the compressor reduces its volume while increasing its density.
Types of Piston Compressor
There are two different types of piston compressors: single acting compressor and double acting compressor.
- Single Acting Compressor – This type of reciprocating compressor has a piston that operates in only one direction. This means that the piston’s other end does not perform any work; only the upper part of the piston compresses the air.
- Double Acting Compressor – As from what its name implies, both sides of the piston are used to compress the air. The double acting compressor comes with two sets of intake and exhaust valves on both sides of the piston. The upward and downward movement of the piston helps produce compressed air.
Since compressors, like the Mac-Air piston compressor, are commonly used in chemical, petrochemical, gas, and general industry, it is highly important to familiarise its major component and its corresponding functions:
1. Cylinders – The cylinder is a pressure valve that holds the gas in the compression cycle. The materials used for the cylinder depends on its operating pressure:
- Cast Iron: for pressures up to 1000 psi
- Nodular Iron: for pressures up to 1500 psi
- Cast Steel: for pressure between 1500 psi and 2500 psi
- Forged Steel: for pressures greater than 2500 psi
2. Piston – The piston is considered to be the heart of the piston compressor. The upward and downward motion of the piston enables suction and compression of the refrigerant. It comes with a set of sliding seals called piston rings to prevent leakage of compressed gas between the cylinder and piston.
3. Crankshaft – This crankshaft of the primary shaft of the piston compressor. The crankshaft is responsible for the reciprocating motion of the piston inside the cylinder. One of its sides is directly connected to the electric motor by a coupling or belt and pulley alignment, while the other side is connected to the connecting rod.
4. Compression Valves – The compression valves consist of the intake/suction and exhaust/discharge valves. The low pressure refrigerant is admitted into the cylinder and the high pressure refrigerant is released through the discharge valve.
Applications for Piston Compressors
Here is a list of the various uses of piston compressors:
- Painting and sanding vehicles (auto shop)
- Cleaning machinery using air blowgun
- Pneumatic drills and hammers (construction sites)
- Spraying crops, conveyors to move feeds and grains to and from the silo, and glasshouse ventilation (agriculture/farming)
- Cutting and welding, operating air tools, sandblasting and finishing metals, blowing molded plastic bottles and gas tanks (manufacturing)