compressors
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
Compressors
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 )
21
1221
21
1221
*
*
Tp
TpQQ
Tp
TpVV
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)
11.17
14.65
286.0
286.0
in
outin
in
outin
P
PQPkW
P
PQPHP
Compressor types
Single cylinder compressor
Multi-staging
• Up to 4 bar single stage
• Up to 15 bar double stage
• Over 15 bar treble or multi-stage
Two-stage compressor
Multi-staging with inter-coolingfor high pressures
Screw compressors
Screw compressors
Vane compressor
Receiver pressure control via motor start/stop
Compressor unloadingpressure switch
Compressor unloadingcentrifugal unloader
Pressure settings
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