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Case Study - What could go wrong During Lubrication of HT / LT Motors

In a plant, there was a HT Slip Ring Induction Motor in which there was a Motor of 2000 KW, 6.6 kV & 988 RPM. The motor was commissioned in 2011 and was running well till when we found out some issues.<br>

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Case Study - What could go wrong During Lubrication of HT / LT Motors

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  1. ISO 9001:2015 ISO 45001:2015 (OH & S) Certified Company Case Study What could go wrong During Lubrication of HT / LT Motors www.systemprotection.in +91-265-2225137

  2. HelloFriends / Sirs, Sowestartedremovingunwantedmaterial fromgreasinginletthroughfinestickand toolswhichwehad. Butafterremoving whatcouldhavebeenvisiblewestarted greasingagain, buttheproblempersists. TheTodayIamgoingtopresentaCaseof InductionMotor, whichmightberarein Industries. Hencewanttosharethe experience, sothattheproblemtheyfaced mustnotbefacedbyothersorcanbe avoided. Nowwebroughtdrillmachinetoremove theforeignparticles, whichhasbecomethe Headacheinlast12hours. Whendrillbit wentinsideandstarteddrilling, toour surprisedrillbitgotdamagedandbroken. Noweveryonewassurprised. Whatcanbe insidewhichcanbreakthedrillbit? We removedthatbrokendrillbit. Inaplant, therewasaHTSlipRing InductionMotorinwhichtherewasaMotor of2000KW, 6.6kV & 988RPM. Themotor wascommissionedin2011andwasrunning welltillwhenwefoundoutsomeissues. Afterrunningformorethan1.0year, approx. 2000hours (1.5years), itwastimetodoRe- lubricationofbearingsofbothDEandNDE Side. Technicianwentforitandstarted greasingthemotorsfromgreasinginleton BothDE & NDESide. OnNDESideit greased8pumpsofgreasegun. Butwhen hestartedgreasingonDEside, after2 pumpgreasestartedcomingbackoutof greasinginlet. Nowwestartedsofthammeringonthe outersideofEndcoverneargreasinginlet, sothattheforeignparticlesmoveoutor changeitsposition (Softhammeringto avoiddamagetoendcoverofHTMotor) aftertryingitfor4hoursnothinghappened. Oneofmyseniorwith -around17-18yrsof experiencetooktheEndcoverandhitit withgroundwithgreasinginletdown (Hit wasmorethansoftandlessthanhard). And whatcomeoutofthegreasinginlet surpriseseveryone. Sowewentandcheckedagainwhatwas happening. Wetriedittoowithforcebut thegreasewascomingbackoutofinlet. Butastheplantwasrunningwecouldn’t domore. Wealsolookforpossibility, ifthe greasinginletwasleftopenorinletcover gotmissedandsomeforeignmaterials mighthavegoneinsidetheinletasthe greasinginletwasfoundnotcoveredduring checking. “ItwasabrokenpieceofDrillBit” notthe onewhichwasbrokenbyus. Nowwecheckwhetherthegreasingholeis throughornot, andyesitwasnotthrough. Wegot / assumedwhatcouldhavehappen duringmanufacturingofEndCoverforthis HTmotor. Theworkmanmighthavebeen drillingholeforgreasingandthedrillbit mighthavebrokenduringthat. Insteadof tellinghisseniors, theykeptasitisand packedMotorwithgoodamountofgrease init, soitcanrunforcoupleofyearsfreely. Duetoproductiondemands, wecouldn’t domuchfornext4monthsdespite monitoringtheDESidebearing temperatureclosely. After4monthswegota6dayplanned shutdown Hewouldhavethoughtit, Letitgoaswho checks “GreasingInlet” during commissioningalsomotoriskeptaround6 – 8monthsatsitePackedbefore commissioningandittakearoundone monthforcommissioning. AndEngineer willdogreasinginMotorobviouslyafter 2000hourstillthattimeraround2years willbegone. Soduringthis6dayshutdownweplanned tocheckwhatistheexactissueintheDE Sidegreasinginlet. Shutdownstartedon3rddayofshutdown wegottocheckourmotorDEsideafterit wasdecoupled. Weknewgreasingisnot goingintobearingthroughgreasinginlet. Wethoughtobviouslysomeforeign materialhasenteredintoGreasinginlet, as greasinginletwasnotcovered. www.systemprotection.in +91-265-2225137

  3. Nowtheproblemwasover. Wemakethe inletgreasethrough, sothatgreasecango tobearing. Fixedthemotor, coupledit, trial takenandgreasingdone. (Sighofreliefat3 AMMidnight) We (Maintenanceteam) mostlybelievethat “WhateverOEMhasdone, mighthavedone asperdesign”, buttheabovecasewas sayingsomethingelse, mistakescan happenfromOEMtooandthat’swhy maintenanceengineeraretheretocorrect it. WeknewwhatwasMaintenanceEngineers nexttarget, tocheckifthesameproblemis thereinrestofmotorsweregreasingnipple isthere. Alsowemustmakeamaintenancepractice tocoverMotorgreaseinlettoavoid enteringofforeignmaterialsintogrease inlet. Below is the Pictorial Representation of HT Motor for Better understanding. www.systemprotection.in +91-265-2225137

  4. CONTACT INFORMATION 301/2/306, SilverlineComplex,OppositeBBC Tower,Sayajigunj,Vadodara - 390005, Gujarat, India. bdm@systemprotection.in www.systemprotection.in +91-265-2225137

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