Compressed Air Explained
The three types of compressors
Piston Compressor
The piston compressor is one of the earliest compressor designs, but it remains the most versatile and is still a very efficient compressor. The piston compressor moves a piston forward in a cylinder via a connecting rod and crankshaft. If only one side of the piston is used for compression, it is described as single acting. If both sides of the piston, top and underside are employed, it is double acting.
The versatility of the piston compressors knows virtually no limits. It compresses both air and gases with very little alterations. The piston compressor is the only design capable of compressing air and gas to high pressures, such as breathing air applications.
The configuration of a piston compressor can be a single cylinder for low pressure/low volume to a multi-stage configuration cable of compressing to very high pressure. In these compressors, air is compressed in stages, increasing the pressure before entering into the next stage to compress the air into even higher pressure.
Compression capabilities:
CompAir's Piston range operates between 0.75 kW to 420 kW (1hp to 563hp) producing working pressure at 1.5 bar to 414 bar (21 to 6004psi).
Typical types of applications:
Gas compression (CNG, Nitrogen, Inert gas, Landfill gas), High Pressure (Breathing air for SCUBA SCBA cylinders, Seismic surveying, Air blast circuit), P.E.T bottling, Engine start, Industrial
Animation of a rotary piston compressor - Click here to view CompAir piston compressors
Rotary Screw
The screw compressor is a displacement compressor with pistons in a screw format; this is the predominant compressor type in use today. The screw compression element main parts comprise male and female rotors that move towards each other while the volume between them and the housing decreases. The pressure ratio of a screw is dependent on the length and profile of the screw and of the form of the discharge port.
The screw element is not equipped with any valves and there are no mechanical forces to create any imbalance. It can therefore work at high shaft speed and combine a large flow rate with small exterior dimensions.
Compression capabilities:
CompAir's Rotary Screw range operates between 4kw to 250 kW (5 to 535hp), producing working pressure at 5 bar to 13 bar (72 to 188psi).
Typical types of applications:
Food Beverage, Brewing, Military, Aerospace, Automotive, Industrial, Electronic, Manufacturing, Petrochemical, Medical, Hospital, Pharmaceutical, Instrument air
Animation of a rotary screw compressor - Click here to view CompAir rotary screw compressors
Rotary Vane
Based on traditional, tried and tested technology, the vane compressor is directly driven at very low speed (1450rpm), offering unrivalled reliability. The rotor, the only continually moving part, has a number of slots machined along its length into which fit sliding vanes that ride on a film of oil.
The rotor rotates within a cylindrical stator. During rotation, centrifugal force extends the vanes from their slots, forming individual compression cells. Rotation decreases the cell volume, increasing the air pressure.
The heat generated by compression is controlled by pressurised oil injection.
The high pressure air is discharged through the outlet port with the remaining traces of oil removed by the final oil separator.
Compression capabilities:
CompAir's Vane compressors operate between 1.1 kW to 75 kW (1.5 to 100hp), producing working pressures of 7 to 8 and 10 bar (101 to 145psi).
Typical applications:
OEM, Printing, Pneumatics, Laboratories, Dentistry, Instruments, Machine tools, Packaging, Robotics
Animation of a rotary vane compressor - Click here to view Hydrovane rotary vane compressors
