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Compressors. Standard Air. Standard air has the following characteristics 14.7 psia (101 kPa abs) Density 0.0725 lb/ft 3 (11.8 N/m 3 ) Temperature 68 F (20 C) Relative humidity 38% Pressure lower than 14.7 psi (101 kPa) absolute creates a vacuum pressure. Rating Compressors.
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Standard Air • Standard air has the following characteristics • 14.7 psia (101 kPa abs) • Density 0.0725 lb/ft3 (11.8 N/m3) • Temperature 68 F (20 C) • Relative humidity 38% • Pressure lower than 14.7 psi (101 kPa) absolute creates a vacuum pressure
Rating Compressors • Compressors are rated in terms of cfm or scfm when the inlet is drawing from atmospheric conditions • (101 KPa, 20oC) • (14.7 psia and 68°F )
Compressors • While air enters at ambient conditions it must be converted to operate at pressures of 6 to 12 bars, and temperatures of 20-100 C • When conversion takes place it produces variation in the pressure, temperature, and volume (typically it is reduced)
Compressor Categories • Positive displacement • Piston, Screw, and Vane • Compressors having more than one cylinder are called multi-stage; the pressure increases are done through the use of multiple cylinders to achieve desired pressure
Power requirements • How much horsepower do we need to run the system? Q(sm3/min) P(kPa Abs)
Multi-staging • Up to 4 bar single stage • Up to 15 bar double stage • Over 15 bar treble or multi-stage
Conditioning Air • The key components to condition compressed air are: • coolers • Moisture separators • Air dryers & receivers • Filters, regulators, lubricators • Mufflers
Conditioning components • After coolers • Used to condense moisture in air prior to operating components (80-85% effective) • Moisture separators • Used to collected and discard condensation from air • Air dryers • Secondary measure used to extract any remaining moisture from system (uses desiccants)
Conditioning components • Air receivers • Storage vessel used to equalize the pulsation of incoming air and allow for uniform flow or air • Filters, regulators, lubricators • Used to clean, regulate, and lubricate • Mufflers • Placed at exhaust to reduce noise and the possibility of airborne particles
Moisture and Dew point • Depending on atmospheric conditions air will contain varying degrees (percentages) of moisture • Saturation point (dew point) is the temperature at which moisture begins to condense of the air