Chapter IX Rotating Equipment 请对应中文版.docx

Chapter IX Rotating Equipment 请对应中文版.docx

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ChapterIXRotatingEquipment请对应中文版

ChapterIXRotatingEquipment

Rotatingequipmentincludes:

pump,compressor,blower,etc.

Pump

1.Whatisthedefinitionofpump?

Whataboutitsclassification?

Apumpisafluidmachinerytomovefluidsandincreaseitspressureenergy.

Accordingtoworkingprinciple,pumpssuchascentrifugalpump,reciprocatingpump,gearpump,vortexpump,screwpump,etc.arecommonlyused.

Accordingtotheprincipleofpumping,pumpsfallintobladepumpandpositivedisplacementpump.Bladepumpmovesfluidbybladesmountedandrotatedinsideofpumpcavity.Basedonvariousbladestructures,itisdividedintocentrifugalpump,axialflowpump,vortexpump,etc.Positivedisplacementpumpcausesfluidtomovebyperiodicvariationofcavitycapacity,includingreciprocatingpumps（pistonpump,plungerpump,diaphragmpump,etc.）androtorpump（gearpump,screwpump,etc.）.

Pumpsarealsoclassifiedaccordingtotheusesofpumps,suchaswaterpump,oilpump,ammoniapump,liquidhydrocarbonpump,sludgepump,noncorrosivepump,condensatepumpandsoon.

2.Whatistheworkingprincipleofcentrifugalpump?

Figure9-1isadiagramofasingle-stagecentrifugalpump.Mainworkingpartsareimpellerswhichhaveacertainnumberofblades;impellersaremountedontheshaftanddriventorotatebytheshaft;pumphousingisastationaryspiralexpandingcavity;pumpsuctionisconnectedwithsuctionpipe;andpumpoutletisconnectedwithdischargepipe.

图9-1离心泵工作简图

Figure9-1Diagramofcentrifugalpump

1—叶轮impeller；2—叶片blade；3—泵壳pumphousing；4—泵轴pumpshaft；5—填料筒gland；6—底阀；bottomvalve

7—扩散管diffusionpipe；8—吸入管suctionpipe；9—排出管dischargepipe

Suctionpipeandpumparefulfilledwithliquidtobetransferredbeforecentrifugalrunning.Whenimpellersdrivenbymotorarerotating,liquidwillproduceenergyfromrotatingimpeller,andthrewawayfromthepump.Liquidwhichisthrownawaywillflowintodiffusionpipethroughpumphousinganddischargefromdischargepipe.Meanwhile,vacuumisproducedintheimpellers,thus,liquidisdrawnintoimpeller.Liquidisdischargedandsuctioncontinuouslyduetoimpellersrotatingcontinuouslyandevenly.

3.Whataboutmainrunningparametersofcentrifugalpump?

（1）Flowrate（Q）-Fluidflowratedischargedfrompumpperunittime.Flowratethatisshowninvolumeiscalledasvolumeflow,unitism3/horm3/s;Flowratethatisshowninweightiscalledweightflow,unitiskg/horkg/s.

（2）Head（H）-Theincrementofenergyofunitweightliquidafterflowingthroughpumpiscalledthehead,kPa,denotedwithmeterliquidcolumn.

（3）Rotatingspeed（n）-Rotationtimesperminuteofpumpshaft,unitisr/min.

（4）Shaftpower（N）-Inputpowerofpump,unitiskW.

（5）Effectivepower（Ne）-Effectiveenergyobtainedfrompumpforliquidtransferredinunittime,unitiskW.

（6）Efficiency（η）-Ratioofeffectivepowerandshaftpower,i.e.η=Ne/N.

4.Takeexamplestoexplainthedetailsofeachsymbolofpumptype?

（1）100YII-60A

Wwhereinin,100:

Nominaldiameterofpumpsuction,mm;

Y:

Single-suctioncentrifugalpump;

II:

CatalogueIImaterial,applicablefor-45～400℃;

60:

Ratedhead,m;

A:

Impellerouterdiameterfirstcutting.

（2）250YSIII~150×2

Wwhereinin,250:

Nominaldiameterofpumpsuction,mm;

YS:

Double-suctioncentrifugalpump;

III:

CatalogueIIImaterial,applicablefor-45～400℃,anti-corrosionofsulfuricacid;

150:

Ratedsinglehead,m;

2:

Secondarystageofimpeller.

（3）Oldtypecentrifugalpump

5FDR-5×4

Wherein,F:

Multi-stagecentrifugalpump;

D:

Single-suction（S:

Double-suctioncentrifugalpump）;

R:

Hotoilpump（J:

Cooloilpump）;

5:

Integervalueofspecificspeeddividedby10;

4:

Impellerstages.

（4）Steamreciprocatingpumptype

Wherein,1QY-2.8/64:

2QYR40-56/25

1,2:

pumpcylinderquantity;

Q:

Steamdriven;

Y:

Pumpedmediumisoil;

R40:

Hotoilpump（ifnotR,mediumtemperature≯200℃）,mediumtemperatureis400℃;

2.8,56:

designflow,unitism3/h;

64,25:

designpressure,unitiskgf/cm2（gauge）.

（5）Gearpumptype

CH——-4.5

WhereinCH:

Gearpump;

4.5:

flowratebelow100r/min,unitisL/min.

2CY-1.1/14.5-1

Wherein2:

numberofgears;

C:

Externalgearpump;

Y:

transferredoil;

1.1Flowrate,m3/h;

14.5:

Dischargehead（gauge）,kgf/cm2.

（6）Vortexpumptype

32W—30；65WX—140

Wherein32,65:

diameterofsuction,mm;

W:

Vortexpump;

WX:

Centrifugalvortexpump;

30,140:

Headatdesignpoint,m.

5.Whatarethemainpartsofcentrifugalpump?

Centrifugalpumpiscomposedofthefollowingparts:

Pumpshell（outlet,inlet,cover,support）;impeller（frontandrearwheeldisc,blade）;shaft（dowel,backcap,coupling）;sealingdevice（sealring,rotatingsealring;stationarysealring）;balancedevice（balancehole,balancetube,balancedisc,etc.）;shaftbracket（oil,watertankbearing,waterretainerring,andoilretainerring）;auxiliaryequipment（pumpseat,coolingwaterpipe,oilcup,etc.）.

6.Whatisthepowerandefficiencyofpump?

Howtocalculate?

Thepowerobtainedafterliquidflowingthroughpumpinunittimeiscalledeffectivepower,dominatedwithNe,unitisW.

Ne=HQρg

intheformula,H-headofpump,mliquidcolumn;

Q-flowrateofpumpunderdeliverytemperature,m3/s;

ρ-densityofliquidunderdeliverytemperature,kg/m3;

g-gravitationalacceleration,m2/s.

Actualpowerofpumpfrommotoriscalledshaftpower,effectivepowerislowerthanshaftpower,ratiois

whichiscalledastotalefficiencyofpump.

7.Whatisrelationshipbetweenheadandflowrateofelectricreciprocatingpump,centrifugalpump?

（1）ElectricreciprocatingpumpflowrateQisconcernedwiththeproductofsectionalareaFandstrokeSofpiston,calculationformulais:

Q=60F·Snη

intheformula:

Q-volumeflowrate,m3/h;

F-pistonarea,m2;

S-pistonstroke,m;

n-reciprocatingfrequencyperminute,times/min;

ηv–volumetricefficiency,generally0.8~0.98.

dischargeheadorheadofelectricreciprocatingpumpisonlydependentonpumpstrength,sealingperformanceandelectricmotorpower.

（2）Centrifugalpumphead,flowratehaverelationshipwithimpellerstructureanddimension.Thebiggerdiameteris,thehigherheadbecomes,thebiggerwidthis,thequickerflowratebecomes;ithasrelationshipwithrotatingspeed,inproportiontoflowrate,headisproportionaltothesquareofrotatingspeed;inaddition,pumpheadisrelatedtostagesofimpeller.Centrifugalpumpheaddoesn’thaverelationshipwithdensity.

8.Howmanycharacteristiccurveofcentrifugalpump?

Howtoutilizethem?

Characteristiccurveofcentrifugalpumpindicatestherelationshipbetweenflowrateandhead,power,efficiencyandnecessary（NPSH）runderacertainrotatingspeed,i.e.itiscomposedoffourcurvessuchasH～Q、N轴～Q、η～Q、（NPSH）r～Q.Thequantitativerelationsoftheseparametersaremeasuredbytestsgenerally.

Characteristiccurveof2B-31typecentrifugalwaterpumpisshowninFigure9-2,whichismeasuredundertherotatingspeedof2800r/min.

Actually,whenutilizethecharacteristiccurveonpumpsample,weshoulddosomeadjustmenttomakeitsense.Becausethesecharacteristiccurvesaremeasuredby20℃waterinambienttemperatureasamedium.Inactualapplication,therewillbesomelargedifferenceinoperationcondition,itisnecessarytodosomeproperconversion.

（1）Influenceofviscosity

Whencentrifugalpumptransferstheliquidwhoseviscosityismorethanfreshwater,energylossinthepumpwillbeincreased.Themoreviscosity,thelessdischargeamountandheadatthemaximumefficiencypoint,andthemoreshaftpowerwillbe.Thus,pumpefficiencywillbedecreased,itisobviouslyforsmallpump.

Undertheoperationcondition,whenliquiddynamicviscosityislessthan10mm2/s,conversionofcharacteristiccurveofpumpisnotnecessary.Ifdynamicviscosityismorethan10mm2/s,itisnecessarytodoconversion.

图9-22B-31型离心泵工作曲线

Figure9-22B-31TypeCentrifugalPumpRunningCurve

（2）Influenceofdensity

Pumpforrefineryandchemicalindustrycouldtransferliquidwithawidescopeofdensity.Differenceofdensityhasnorelationshipwithvolumeflow,headandefficiency.However,shaftpowerofpumpwillvarywithliquiddensity,whichshouldbemodifiedbasedonformulaN轴=

（seeQuestion6）

（3）Influenceofpumprotatingspeed

Theflowrate,head,powerandefficiencywillbevariedwithcentrifugalpumprotatingspeedn,andoriginalcharacteristiccurvewillnotbeapplicable.Theoretically,relationshipofH、Q，Neandrotatingspeedncouldbecalculatedasthefollowingformula:

intheformula,n–normalratedspeed;

n′-adjustedspeed.

9.Whatissimilaritylawofpumpimpellercutting?

Therelationshipamongflowrate,head,powerandouterdiameterbeforeandafterimpellerouterdiametercuttingiscalledassimilaritylawofpumpimpellercutting.

Calculationformula:

intheformula,Q、H、N、D–pumpflowrate,head,powerandouterdiameterofimpellerwithoutcutting;

Q′、H′、N′、D′-pumpflowrate,head,powerandouterdiameterofimpelleraftercutting.

Changerotatingspeedtogetvariouspumpcharacteristiccurveunderdifferentconditions.Thismethodisunderrestraintsinpractice,becausemostofpumpisdrivenbyACmotor,whoserotatingspeedcannotchangedatrandom.Therefore,utilizeimpellerouterdiametercuttingmethodtomakecharacteristiccurvechangeinordertogetrequiredperformanceparameter.Butnotethatimpellercuttingmethodisonlyapplicableforoccasionstoreduceflowrate,headandpower.

Efficiencywillbereducedafterimpellercutting.Itisnecessarytorestrictimpellercuttingtocontrolproperefficiency.

10.Whatisspecificspeedofpump?

Specificspeedofbladepumpisacomprehensiveparameterwhichis