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COMPRESSOR

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Presentation OutlineIntroductionCompressed Air Systems

Types of CompressorsRotary Screw CompressorsARL Compressed Air Requirements

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INTRODUCTIONCompressors used to increase thepressure of a compressible fluid (air

or gas)Compresses air from 35 psi up to65000 psi

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Compressed Air Systems

Main Components of Compressed AirSystem:

Intake air filtersInter-stage coolersAfter coolers

Air dryersMoisture drain trapsReceivers

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Selection Criteria of a

CompressorEfficiency at full, partial and no loadNoise level

SizeOil carry-overVibration

MaintenanceCapacityPressure

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Types of Compressors

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Types of CompressorsPositive Displacement (PD):Operate by trapping a specific volume of

gas and forcing it into a smaller volume

2 Basic Designs for PD CompressorsRotary

Reciprocating

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Types of CompressorsDynamic:Operate by accelerating the gas and

converting the energy to pressure

2 Basic Designs for Dynamic/ContinuousFlow Compressors

CentrifugalAxial

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Rotary CompressorsRotor instead of pistons: continuousdischarge

Benefits: low cost, compact, low weight,easy to maintain4 Primary Types

Rotary Screw

Sliding VaneLobeLiquid Ring

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Rotary Screw CompressorContinuous sweeping motion causevery little pulsation or surging of flow

Operates with 2 helical rotors thatrotate toward each other, causing theteeth to meshRotation forces the gases to becometrapped in the central cavity

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Oil Free Screw CompressorCompression of air entirely throughthe action of the screws, without the

assistance of an oil sealUsed where entrained oil carry-over isnot acceptable, such as medicalresearch and semiconductormanufacturing

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Oil Flooded Screw CompressorInjection of oil into the compressioncavities to aid sealing and provide

cooling sink for the gas chargeSeparation of oil from the dischargestream, cooling, filtration andrecyclingOil captures non-polar particulatesfrom the incoming air

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Rotary Screw Compressor

Process Description

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ARL Compressed AirRequirements

Type Oil Flooded Screw compressorDriver Type Electric Motor Driven

Cooling Type Air Cooled

Sound Level 85 db (A)/meter (Max)

Applicable Standard API 619

Normal Capacity 28.3 m3/min (1000) SCFM

Normal Discharge Pressure 7.2 kg/cm2g

Maximum Discharge Pressure 7.9 kg/cm2g

Compressed Air Quality Oil free

Unloader Type AutomaticInlet Dry Bulb Temperature -2 to 50°C

Average Barometric Pressure 0.9723 kg/cm2 a

Altitude 509 meters

Normal Discharge Temperature 58°C (Air Cooler Outlet)

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ARL Compressed AirRequirements

Number of dryer vessels Two

Dew point temperaturespecification

-40°C (Class II)

Max. allowable solid particle sizein instrument air product 0.1 g/m3 for particles size above1 micron (Class II)

Normal Dryer Inlet Pressure 7.2 kg/cm2 g

Lead Compressor Unloading 7.2 kg/cm2 g

Lead Compressor Loading 6.8 kg/cm2 g

Lag Compressor Unloading 7 kg/cm2 g

Lag Compressor Loading 6.6 kg/cm2 g

Plant Air Supply Cut-Off 5.8 kg/cm2 g

Emergency Shutdown Initiation 4.8 kg/cm2 g