Ball bearing lubrication in centrifugal pumps

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1、BallbearinglubricationincentrifugalpumpsThemanufacturerusingthebearinginhisequipment,nottheballbearingmanufacturer,determinestheanticipatedlifeofaballbearing.Thislife,oncedetermined,iscalledtheL10lifeofthebearinganditisbasedonthepremisethat90%ofthebearingswilllastacertainamountofrevolutio

2、nsbeforetheyexperiencemetalfatigue.Fatigueisaweakeningandeventualbreakingofmetalsduetoaprolongedstrain.Sincethemanufactureroftheequipmentthatusesthebearingistheonlyonethatknowtheoperatingconditions,hesetstheL10life.Itisusuallymeasuredinyears.ThisfatigueorL10lifeisdeterminedfrom:·Thebearin

3、gmaterial·Theloadonthebearing.(stress)·Thenumberofloadcyclesthebearingmaterialisexposedto(strain).Durironpumpcompanyliteraturestatesthattheradialbearingintheir2x3x10Marktwo,grouptwopumphasaL10lifeof300years.Inotherwords90%ofthosebearingswouldbeexpectedtorun300yearsbeforetheywouldexperienc

4、eafatiguefailure.Sincethepumpenduserisnotexperiencinganythinglikethattypeoflife,whatiscausingtheprematurefailure?Isitamanufacturing,installation,maintenanceoroperationproblem?Itturnsoutthatbearingsfailfortwomainreasons:·Contaminationofthebearingoilbywaterormoisture.·Highheatoftencausedbyt

5、oomuchlubrication.Aslittleas0.002%waterinthebearingoilwillreducebearinglife48%.Thewaterentersfrompackingleakage,washdownhosesandaspirationcausedbythetemperaturecoolingdowninthebearingcasingaftershutdown,andmoistureladenairenteringthebearingcase.A6%watercontentintheoilwillreducebearinglife

6、byasmuchas83%.Thewaterormoisturecontaminationcomesfromthreemainsources:·Packingleakage.·Waterhosesusedtowashdownthebaseplateareabecauseofpackingleakage.·Aspirationormoistureintheairenteringthebearingcaseespeciallywhenthepumpisstopped.Inpaper13-9wetalkedaboutthesealsyoucanusetokeepthismois

7、tureoutofyourbearingcase.Inthispaperwewillinvestigatethesecondreasonbearingsfail.4Excessiveheat!AcoupleofparagraphsaboveIsaidthatoverlubricationwouldcausehighheat.Whatistheproblemwithoverlubrication?Ifalittlelubricationweregood,wouldn'talotbebetter?Notreally!Thinkab