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CENTRIFUGAL COMPRESSORSCENTRIFUGAL COMPRESSORS

N.B.HEMANT HUMARN.B.HEMANT HUMAR

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CLASSIFICATION OF COMPRESSORSCLASSIFICATION OF COMPRESSORS

A xia lly S p lit

R ad ia lly S p lit

In teg ra lly G eared

C en trifu g a l(u p to 1 5 0 0 0 0 m 3 /h r)

A xia l(flow > 1 0 0 ,0 0 0 m 3 /h r)

M ed iu m to la rg e flow sL ow to m ed iu m p res su re

D yn am ic

P is ton

L ab yrin th

D iap h rag m

R ec ip roca tin g< 2 0 0 0 m 3 /h r

S crew

L ob e

R ota ry

L ow to m ed iu m flowsP ress u re n o lim ita t ion

P os it ive D is p lacem en t

C om p res so rs

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VARIOUS TYPES OF COMPRESSORS:VARIOUS TYPES OF COMPRESSORS:

STRAIGHT THROUGHSTRAIGHT THROUGH STRAIGHT THROUGH – BACK TO BACKSTRAIGHT THROUGH – BACK TO BACK SIDE STREAM ( EXTRACTION / INJECTION )SIDE STREAM ( EXTRACTION / INJECTION ) BARREL TYPEBARREL TYPE SINGLE STAGE COMPRESSORSSINGLE STAGE COMPRESSORS HIGH SPEED INTEGRALLY GEARED COMPRESORSHIGH SPEED INTEGRALLY GEARED COMPRESORS

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Typical Construction Centrifugal Compressor (Radial Split)

A- CasingB-Diaphragm BundleC-RotorD-ImpellersE-Balance DrumI-Thrust BearingH-Journal BearingF-Thrust CollarL-LabyrinthM-Seals

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TYPICAL CENTRIFUGAL COMPRESSORTYPICAL CENTRIFUGAL COMPRESSOR

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GENERAL INFORMATION / CONSIDERATIONSGENERAL INFORMATION / CONSIDERATIONS

CAPACITY RANGE FOR CENTRIFUGAL COMPRESSORS - 1,700 CAPACITY RANGE FOR CENTRIFUGAL COMPRESSORS - 1,700 TO 170,000 mTO 170,000 m33 /hr /hr

HORIZONTALLY SPLIT COMPRESSORS:HORIZONTALLY SPLIT COMPRESSORS: WITH NOZZLES ON THE BOTTOM HALF , MAINTENANCE WITH NOZZLES ON THE BOTTOM HALF , MAINTENANCE

WITHOUT DISTRIBING THE PROCESS PIPING.WITHOUT DISTRIBING THE PROCESS PIPING. WITH PRESSURES ABOVE 500 psig THESE COMPRESSOR WITH PRESSURES ABOVE 500 psig THESE COMPRESSOR

CASINGS LOOSE THEIR SEALING CAPABILITYCASINGS LOOSE THEIR SEALING CAPABILITY VERTICALLY SPLI COMPRESSORS:VERTICALLY SPLI COMPRESSORS:

MAINTENANCE WITHOUT DISTRUBING THE PROCESS MAINTENANCE WITHOUT DISTRUBING THE PROCESS PIPINGPIPING

FOR PRESSURES ABOVE 500 PSIG THIS TYPE OF CASINGS FOR PRESSURES ABOVE 500 PSIG THIS TYPE OF CASINGS SHALL BE USED.SHALL BE USED.

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GENERAL INFORMATION / CONSIDERATIONS (Contd.)GENERAL INFORMATION / CONSIDERATIONS (Contd.)

NUMBER OF CASINGS FOR COMPRESSORS IS GENERALLY NUMBER OF CASINGS FOR COMPRESSORS IS GENERALLY LIMITED TO 3LIMITED TO 3

SINGLE STAGE COMPRESSORS:SINGLE STAGE COMPRESSORS: SIMILAR TO SINGLE STAGE, OVERHUNG C.F. PUMPS.SIMILAR TO SINGLE STAGE, OVERHUNG C.F. PUMPS. PRESSURE RATIO ~ 1.6PRESSURE RATIO ~ 1.6

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SPECIFYING FLOW TO A COMPRESSOR MANF.SPECIFYING FLOW TO A COMPRESSOR MANF.

MASS FLOWMASS FLOW IT IS DIFFICULT TO APPRECIATE SIZE OF COMPRESORIT IS DIFFICULT TO APPRECIATE SIZE OF COMPRESOR CONFUSION ON ACCOUNT OF WATER VAPORCONFUSION ON ACCOUNT OF WATER VAPOR

ACTUAL FLOWACTUAL FLOW DISADVANTAGEOUS IN CASE OF SIDE LOAD COMPR.SDISADVANTAGEOUS IN CASE OF SIDE LOAD COMPR.S

STANDARD FLOW / NORMAL FLOWSTANDARD FLOW / NORMAL FLOW

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COMPRESSOR PERFORMANCE CALCULAIONCOMPRESSOR PERFORMANCE CALCULAION

WHY COMPRESSIBILITY FACTORWHY COMPRESSIBILITY FACTOR : : IDEAL GAS EQUATION : PV = RTIDEAL GAS EQUATION : PV = RT NO GAS CONFIRMS TO IDEAL GAS BEHAVIOUR. NO GAS CONFIRMS TO IDEAL GAS BEHAVIOUR. INTRODUCTION OF DEVIANCE PARAMETER TO APPLY THE INTRODUCTION OF DEVIANCE PARAMETER TO APPLY THE

IDEAL GAS EQUATION TO REAL GAS EQUATIONIDEAL GAS EQUATION TO REAL GAS EQUATION HENCE: PV = ZRTHENCE: PV = ZRT

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CALCULATION OF COMPRESSIMILITY FACTORCALCULATION OF COMPRESSIMILITY FACTOR

ASSUMPTION - LAW OF CORRESPONDING STATESASSUMPTION - LAW OF CORRESPONDING STATES CALCULATE REDUCTION PRESSURE FOR EACH COMPONENT CALCULATE REDUCTION PRESSURE FOR EACH COMPONENT

OF THE GAS COMPOSITION MULTYPLIED BY THE MOLE OF THE GAS COMPOSITION MULTYPLIED BY THE MOLE FRACTIONFRACTION

AND ADD ALL REDUCED PRESSURES TO FIND REDUCED AND ADD ALL REDUCED PRESSURES TO FIND REDUCED PRESSURE OF THE GAS MIXTUREPRESSURE OF THE GAS MIXTURE

Pr = P / Pc

Pc = Critical pressure

P = Pressure of the gas

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SIMILARLY CALCULATE REDUCED PRESSURE FOR EACH SIMILARLY CALCULATE REDUCED PRESSURE FOR EACH COMPONENT OF THE GAS COMPOSITION MULTYPLIED BY COMPONENT OF THE GAS COMPOSITION MULTYPLIED BY THE MOLE FRACTIONTHE MOLE FRACTION

AND ADD ALL REDUCED TEMPERATURES TO FIND REDUCED AND ADD ALL REDUCED TEMPERATURES TO FIND REDUCED TEMPERATURE OF THE GAS MIXTURETEMPERATURE OF THE GAS MIXTURE

OBTAIN THE COMPRESSIBILITY FACTOR FROM THE OBTAIN THE COMPRESSIBILITY FACTOR FROM THE COMPRESSIBILITY FACTOR CHARTCOMPRESSIBILITY FACTOR CHART

Tr = T / Tc

Tc = Critical Temperature

T = Temperature of the gas

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CALCULATION OF MOL. WEIGHT, Cp AND KCALCULATION OF MOL. WEIGHT, Cp AND K MOL. WEIGHT CONTRIBUTION OF EACH COMPONENT = MOL. MOL. WEIGHT CONTRIBUTION OF EACH COMPONENT = MOL.

WEIGHT OF THE COMPONENT X MOLE FRACTIONWEIGHT OF THE COMPONENT X MOLE FRACTION ADD MOL. WT. CONTRIBUTION FOR ALL COMPONENTS TO ADD MOL. WT. CONTRIBUTION FOR ALL COMPONENTS TO

OBTAIN THE MOL.WT. OF THE GAS MIXTUREOBTAIN THE MOL.WT. OF THE GAS MIXTURE

Cp CONTRIBUTION OF EACH COMPONENT = Cp OF THE Cp CONTRIBUTION OF EACH COMPONENT = Cp OF THE COMPONENT X MOLE FRACTIONCOMPONENT X MOLE FRACTION

ADD Cp CONTRIBUTION OF ALL COMPONENTS TO OBTAIN ADD Cp CONTRIBUTION OF ALL COMPONENTS TO OBTAIN THE Cp OF THE GAS MIXTURETHE Cp OF THE GAS MIXTURE

K = Cp / ( Cp – 8.314 )K = Cp / ( Cp – 8.314 )

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TYPICAL PERFORMANCE CURVE

OF CENTRIFUGAL COMPRESSOR

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SYSTEM RESISTANCE AND PERFORMANCESYSTEM RESISTANCE AND PERFORMANCE

N1

N2N3

N4

CAPACITY

Δ PR

ESSU

RE

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PERFORMANCE VARIATIONS:PERFORMANCE VARIATIONS:

CHANGE IN INLET PRESSURECHANGE IN INLET PRESSURE POWER REQUIREMENT DIRECT PROPORTONALLY CHANGE POWER REQUIREMENT DIRECT PROPORTONALLY CHANGE INLET FLOW ILL ALSO CHAGE IN THE SAME WAYINLET FLOW ILL ALSO CHAGE IN THE SAME WAY THE PEFORMANCE CURVE FALLS LOWER TO RATEDTHE PEFORMANCE CURVE FALLS LOWER TO RATED

VARIATION IN INLET TEMPERATUREVARIATION IN INLET TEMPERATURE PR. RATIOPR. RATIO INVERSELY PROPORTIONAL TO INLET TEMP. INVERSELY PROPORTIONAL TO INLET TEMP.

HENCE FOR LOWER TEMP. THE DISCH. TEMP. INCREASESHENCE FOR LOWER TEMP. THE DISCH. TEMP. INCREASES MASS FLOW INCREASES AND SO AS THE POWERMASS FLOW INCREASES AND SO AS THE POWER THE PEFORMANCE CURVE RISES ABOVE ORIGINAL CURVETHE PEFORMANCE CURVE RISES ABOVE ORIGINAL CURVE

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PERFORMANCE VARIATIONS (Contd..):PERFORMANCE VARIATIONS (Contd..):

VARIATION IN MOLECULAR WEIGHTVARIATION IN MOLECULAR WEIGHT PRESSURE RATIO DIRECTLY PROPORTIONAL TO MWPRESSURE RATIO DIRECTLY PROPORTIONAL TO MW DISCHARGE PRESSURE INCREASESDISCHARGE PRESSURE INCREASES POWER REQUIREMENT INCREASES POWER REQUIREMENT INCREASES

VARIATION IN Z AND Cp/Cv VALUESVARIATION IN Z AND Cp/Cv VALUES FOR AIR APPLICATIONS THESE VARIATIONS ARE VERY FOR AIR APPLICATIONS THESE VARIATIONS ARE VERY

LESS. SO NEGLIGIBLELESS. SO NEGLIGIBLE FALL IN COMPRESSIBILITY RAISES THE PERF. CURVEFALL IN COMPRESSIBILITY RAISES THE PERF. CURVE FALL IN Cp/ Cv ALSO RAISES THE PERF. CURVEFALL IN Cp/ Cv ALSO RAISES THE PERF. CURVE

VARIATION IN RPM ( Hp DIR. PROP. TO NVARIATION IN RPM ( Hp DIR. PROP. TO N22 ) )

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SURGE AND STONE WALL SURGE AND STONE WALL

SURGE IS THE MINIMUM STABLE FLOW POINTSURGE IS THE MINIMUM STABLE FLOW POINT STONE WALL IS THE MAXIMUM STABLE POINTSTONE WALL IS THE MAXIMUM STABLE POINT BEYOND THE SURGE AND STONE WALL POINTS THE BEYOND THE SURGE AND STONE WALL POINTS THE

COMPRESSOR’S OPERATION IS UNPREDICTABLE.COMPRESSOR’S OPERATION IS UNPREDICTABLE. COMPRESSOR SURGE IS DAMAGING TO THE COMPRESSOR.COMPRESSOR SURGE IS DAMAGING TO THE COMPRESSOR.

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ANTI SURGE CONTROL:ANTI SURGE CONTROL:

HARDWARE REQUIRED FOR ANTI SURGE CONTROL:HARDWARE REQUIRED FOR ANTI SURGE CONTROL: RECYCLE PIPING LOOPRECYCLE PIPING LOOP ANTI SURGE VALVE WITH NECESSARY VALVE ANTI SURGE VALVE WITH NECESSARY VALVE

ACCESSORIESACCESSORIES INSTRUMENTATION FOR MEASURING THE FLOW INSTRUMENTATION FOR MEASURING THE FLOW

THROUGH THE COMPRESSORTHROUGH THE COMPRESSOR INSTRUMENTATION MEASURING INLET & OUTLET INSTRUMENTATION MEASURING INLET & OUTLET

PRESSURES & TEMPERATURESPRESSURES & TEMPERATURES

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ANTI SURGE CONTROL ANTI SURGE CONTROL

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ANTI - SURGE CONTROL:ANTI - SURGE CONTROL:

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METHOD OF CAPACITY CONTROLMETHOD OF CAPACITY CONTROL

SUCTION / DISCHARGE THROTTLINGSUCTION / DISCHARGE THROTTLING BYPASSBYPASS IGVsIGVs SPEED VARIATIONSPEED VARIATION

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CAPACITY CONTROL BY SPEED VARIATIONHe

ad

Flow

Speed

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COMPRESSOR MONITORING AND SAFETY EQPT.COMPRESSOR MONITORING AND SAFETY EQPT.

BEARING / TEMPERATURE MANITORBEARING / TEMPERATURE MANITOR MEASUREMENT OF VIBRATION MEASUREMENT OF VIBRATION SHAFT POSITIONSHAFT POSITION

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HIGH SPEED CENTRIFUGAL COMPRESSORS:HIGH SPEED CENTRIFUGAL COMPRESSORS: CAPACITIES FROM 10 ACFM TO 100000 ACFMCAPACITIES FROM 10 ACFM TO 100000 ACFM POWER RANGING FROM 15 HP – 2500 HP OR MOREPOWER RANGING FROM 15 HP – 2500 HP OR MORE SPEEDS UPTO 5800 RPM TO 50000 RPMSPEEDS UPTO 5800 RPM TO 50000 RPM DIAMETER OF THE IMPELLERS FROM 5” TO 36”DIAMETER OF THE IMPELLERS FROM 5” TO 36” USED FOR LOW CAPACITIES AND HIGH HEAD REQUIREMENTSUSED FOR LOW CAPACITIES AND HIGH HEAD REQUIREMENTS TO DECIDE APPLICEBILITY OF HIGH SPED COMPRESSORS – USE TO DECIDE APPLICEBILITY OF HIGH SPED COMPRESSORS – USE

BALJE’S CHARTBALJE’S CHART FOR PRESSURE RATIO – 1.005 TO 3.5FOR PRESSURE RATIO – 1.005 TO 3.5 TYPICAL APPLICATIONS:TYPICAL APPLICATIONS:

MOLECULAR SEIVE ABSORPTION / REGENERATIONMOLECULAR SEIVE ABSORPTION / REGENERATION VAPOR RECOVERY / BOGVAPOR RECOVERY / BOG GAS RECYCLE SYSTEMSGAS RECYCLE SYSTEMS CHLORINE, NITROGEN ETC.CHLORINE, NITROGEN ETC.

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AXIAL FLOW COMPRESSORS:AXIAL FLOW COMPRESSORS:

INCREASING TENDENCY FOR USE OF AXIAL COMPRESSORSINCREASING TENDENCY FOR USE OF AXIAL COMPRESSORS HIGHER EFFICIENCIES COMPARED TO RADIL TYPEHIGHER EFFICIENCIES COMPARED TO RADIL TYPE APPLICATIONAPPLICATION

REFINERIES – CATALYTIC CRACKINGREFINERIES – CATALYTIC CRACKING BUTADIENE -6000 TO 150000 ICFM @ 20 -30 PSIG AIRBUTADIENE -6000 TO 150000 ICFM @ 20 -30 PSIG AIR NITRIC ACID PLANTSNITRIC ACID PLANTS AIR SEPARATION PLANTSAIR SEPARATION PLANTS BLAST FURNACESBLAST FURNACES

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