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Compressed Air System
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Compressed air systems consist of a supply side, which includes compressors and air treatment, and a demand side, which includes distribution and storage systems and end-use equipment. A properly managed supply side will result in clean, dry, stable air being delivered at the appropriate pressure in a dependable, cost-effective manner. Below figure shows you one typical compressed air system.
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Compressor Types
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There are many different types of compressors on the market, each using different technology to produce air. A description of compressors commonly used in industry follows.
1) Reciprocating compressors
Reciprocating compressors work through the action of a piston in a cylinder. Pressure can be developed on one or both sides of the piston. For large volumes of compressed air, they are usually the most expensive to buy and install, and require greater maintenance, however, they may be lower cost at small capacities. Due to their size and the vibrations caused they require large foundations and may not be suitable where noise emissions are an issue. Nevertheless, they are the most energy efficient, both at full and part loads.
2) Screw (or rotary) compressors
Screw (or rotary) compressors use two meshing helical screws, rotating in opposite directions to compress air. These compressors are usually the lowest cost to install, for large volumes of compressed air. To ensure maximum efficiency of screw compressors, it is important to correctly size the compressor and apply internal and external control systems for part load conditions. Variable output and variable speed drives are usually available from most suppliers. Below picture shows you the structure of screw compressor.
3) Screw Compressors (oil free)
Carry the same benefits as oil injected screw compressors but compress in two stages and have no lubricant in contact with the air during its passage through the compressor. Water injected screw compressors are also available where oil free air is required.
4) Centrifugal compressors
Centrifugal compressors use high speed rotating impellors to accelerate air. To reach operating pressures, several impellor stages are required. They have low installation costs, but are expensive to buy because they are precision machines. They are fairly efficient down to about 60% of their design output.
5) Scroll Compressors
These compressors are suitable for oil free air compression at smaller air capacities.