COMPRESSORS: A DETAILED STUDY OF TYPES AND COMPONENTS
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The document discusses different types of compressors used to compress gases. It describes positive displacement compressors like reciprocating, screw, and rotary vane compressors which work by reducing the gas volume. Dynamic compressors like centrifugal compressors are also discussed which increase gas pressure using an impeller. Key components, working principles, advantages and disadvantages of reciprocating, screw, rotary vane and centrifugal compressors are summarized. Selection factors for compressors like required pressure, flow rates, piston speed and system layout are also highlighted.
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COMPRESSORS: A DETAILED STUDY OF TYPES AND COMPONENTS
- 2. Detailed Study of various Components: Compres sors Conden sers Evapora tors Expansion Devices 1/31/2018
- 3. Compressors are mechanical devices that compresses gases. It is widely used in industries and has various applications The machine which takes in air or any other gas at low pressure and compresses it to high pressure are called compressors. A compressor is used for increasing the pressure of air is called Air compressor. 1/31/2018
- 4. 1/31/2018
- 5. Air compressors are classified according to method of energy transfer and pressure generation i.e. positive displacement and dynamic compressors Positive displacement compressors work on the principle of increasing the pressure of air by reducing the volume of air in an enclosed chamber Dynamic compressors works on the principle of imparting the energy by rotating vanes of impeller on air flowing through casing that increases pressure in air 1/31/2018
- 6. Reciprocating Air compressors Reciprocatingaircompressorsarepositivedisplacement typeofaircompressors. Thesearepiston&diaphragmtype,vanetype,geartype, screwtypecompressors Theprincipleofoperationissamebutaccordingtostages thedeliverypressureisdifferentineachcompressor. 1/31/2018
- 7. Areciprocatingaircompressorconsistofapistonwhichis enclosedwithinacylinderandequippedwithsuctionand dischargevalve ThepistonreceivespowerfromelectricmotororICengine. Thecompressionofairisdonebyfirstdrawingavolumeof airintothecylinderthroughsuctionvalveduringsuction strokeofpistonandthencompressedanddischarged throughdeliveryvalveduringdeliverystroke 1/31/2018
- 9. Whenpistonstartsmovingdownwards,thepressureinside thecylinderfallsbelowatmosphericpressurethatopens suctionvalve. Thepressureoftheairinthecylinderrisesduring compressionandattheendofcompression,deliveryvalve opensanddischargesthecompressedairintothereceiver tank. Singlestageaircompressordeveloppressureupto7bar. Forhigherpressuresmultistagecompressorsaresuitable 1/31/2018
- 10. Double stage Reciprocating Air compressors Itconsistoftwocylinders–lowpressurecylinderandhigh pressurecylinder Piston,crankcase,pistonrod,crank,crankshaft, oil,finsetc. 1/31/2018
- 11. 1/31/2018
- 12. ThefreshairisdrawninsidetheL.P.cylinderthroughinlet suctionfilter. Thisairiscompressedbypiston Asthepistonmovestowardstheendofcylinder,theair compressiontookplace. ThefreshairisdrawninsidetheL.P.cylinderthroughinlet suctionfilter. Thisairiscompressedbypiston Asthepistonmovestowardstheendofcylinder,theair compressiontookplace. 1/31/2018
- 14. Advantages Simple in design Lower initial cost Easy to install Higher effeiciency 1/31/2018
- 15. Disadvantages Number of moving parts are more Higher maintenance cost Heavy foundation is required as it has vibration problem Cannot run at full capacity 1/31/2018
- 17. Rotary vane compressor Itispositivedisplacementtypecompressor. Itprovideshigherefficiencyandflowratesoverawide rangeofpressure Rotaryvanecompressorconsistofrotorwithanumber ofvanesinsertedintheradialslotscutinrotor. 1/31/2018
- 18. Rotary vane compressor Therotorismountedeccentricinacasing. Thevanesslidesradiallyinandoutoftherotor. Astherotorrotatesathigherspeed,centrifugalforce throwsthevanesoutwardkeepingtheendofvanein contactwiththestatorring. 1/31/2018
- 19. Rotary vane compressor Astherotorturns,compressionisachievedasthevolume goesfromamaximumatintakeporttominimumatthe exhaustport. Anoilisinjectedintotheairintakeandalongthestator wallstocooltheairandlubricatebearingandvanesand toprovideasealbetweenthevaneandstatorwallto reduceinternalleakage. 1/31/2018
- 20. Advantages: Simpledesign Compactinsize Lightinweight Easytoinstall Lowcost Lowmaintenancecost Longerlife Fewmovingparts Lowrotationalspeed Expensivefoundationnotrequired 1/31/2018
- 21. Disadvantages: Lowerefficiency Difficultywithhigherpressureabove200psi Oilinjecteddesignshaveoilcarryover 1/31/2018
- 22. Centrifugal compressor Itisdynamiccompressor. Itconsistofarotatingimpellerwhichrotatesathigher speed(upto60000rpm) Animpellerfittedinsidecasingforcetheairtotherim ofimpeller,increasingvelocityofair. 1/31/2018
- 25. Centrifugal compressor Adiffuser(divergentshapeofcasing)sectionconvertsthe velocityofair tocauseanincreaseinpressure.This process is called dynamic compression. These compressors are used for continuous, stationary services in industries like oil refineries, chemical and petrochemical plants, natural gas processing plants. 1/31/2018
- 26. Centrifugal compressor These are also used in IC engine superchargers and turbochargers. In gas turbine plants It can provide extremely high output pressures greater than 10000psi. 1/31/2018
- 27. Screw compressor It consist of two screws - one with convex and the other with concave contour mostly called male and female rotor respectively. These two screws gets rotating by means of gear trips there by sucking the air through an inlet port in chamber and then compressing the same 1/31/2018
- 30. Screw compressor Thus compression begins and air is discharged at the end of other side. There is no contact between male and female rotors and casing. Hence no lubrication require but oil may injected for the purpose of cooling. 1/31/2018
- 31. Details of Screw Compressor 1/31/2018
- 32. Twin lobe compressor It is used in applications where higher flow at comparatively low pressure is required. 1/31/2018
- 33. Twin lobe compressor Here two lobes are placed in a casing The air is transferred from suction side to the delivery side with continuous rotation of two lobes The lobes are precisely maintained and the casing also maintained to close tolerances It has limited compression ratio @ 1.7 1/31/2018
- 34. Selection of compressors Pressure : The discharge pressure from the compressor should be decided first considering the needs of the cylinder, air motor & pressure drop in the circuit. Most of pneumatic systems and tools are designed for pressure of 6 – 7 bar. A compressor used should meet the requirement. 1/31/2018
- 35. Selection of compressors Pressure : Pneumatic circuit requiring air at high pressure can be supplied with air by a separate high pressure compressor While any low pressure can be met by availing a reducing valve. For huge air flow rates at pressures below 2 bar, a turbo-blower or low pressure rotary compressor may be used. 1/31/2018
- 36. Selection of compressors Flow rates or capacity:- Volume of air required per minute is also an important factor for selection. The capacity should be adequate enough to supply air to all devices operating simultaneously. In many plants where pneumatic tools are operated intermittently, in such cases maximum instantaneous demand of the compressed air has to be find first. 1/31/2018
- 37. Selection of compressors Speed of piston:- The speed of piston inside the cylinder must also be considered. For small capacity compressor, the piston speed 300 m/min, whereas for large capacity compressor piston speed 250 m/min. The layout of pipe line, system requirement and the distance of user machine from compressor plant 1/31/2018