New wire rope designs for multi layer drums

Newwireropedesignsformultilayerdrums1NewwireropedesignsformultilayerdrumsbyDipl.-Ing.RolandVerreetThebendingfatiguemechanismBendingcyclesoversheavesBendingcyclesoversinglelayer,grooveddrumsBendingcyclesovermultilayerdrumsBendingfatiguedamagedistributioninreevingsystemswithasinglelayerdrumBendingfatiguedamagedistributioninreevingsystemswithamultilayerdrumMultilayerspoolingonhelicaldrumsMultilayerspoolingonLebusdrumsTheinfluenceoftheD/dratioTheinfluenceofropepretensionTheinfluenceoftheropediametertoleranceRemedy1:ShiftingthecrossoverzonesRemedy2:SpoolingaidsRopesolutionsRopesolution1:LangslayropesRopesolution2:RopeswithbiggerouterwiresRopesolution3:RopeswithcompactedouterstrandsRopesolution4:HammeredropesFillfactors,spinningfactors,weightfactors,discardnumbersRopedataCasarStarfitRopedataCasarUltrafitRopedataCasarParafitAdditionalCasarLiterature23346789101214151717171717172122242628Theauthor:RolandVerreet•WireRopeTechnologyAachenGrünenthalerStr.40a•D-52072AachenTel.+49241173147•Fax[phone]•e-mail:[e-mail]©3/2003.CartoonsbyRolfBunse,PRGmbH.TheauthorwouldliketothankDr.IsabelRidge,UniversityofReading,forproofreadingthetextandmakingusefullsuggestions.AlexanderFrings,thanksforthehelpduringthetypesetting.Reproduction,inwholeorinpart,onlywiththewrittenpermissionoftheauthor.NewwireropedesignsformultilayerdrumsbyDipl.-Ing.RolandVerreetThesteelwireropeofaproperlydesignedandmaintainedcraneshouldhaveareasonablylongservicelifeandonedaybediscardedbecauseoffatigue,thewireropeequivalentofoldage.Butoftenwireropesdon´tgetveryold:theymightdieprematurelybecauseofexces-siveabrasionorcorrosion(thewireropeequivalentsofskincancer).Here,properwireroperelubricationmightbetheanswer.Wireropesmightalsodieprematurelybecauseofmechanicalorstructuraldamages(thewireropeequivalentsofbeingrunoverbyabus).Improvedcranedesignandproperwireropeandcraneusagewillhelptoavoidtheseproblems.Butwhataboutdrumcrushing?Ifawireropediesbecauseofdamagesreceivedwhenspoolingonandoffadrum,isthatpartofnormalropelife?Manycranedesignersandusersthinkso.Buttheyarewrong:Whendrumcrushingoccurs,thewireropedamagesitself.Drumcrushingisthewireropeequivalentofsuicide.Thispaperexplainsthemechanismsandshowshowdrumcrushingcanbeavoided.ThebendingfatiguemechanismIfawireropeissubjectedtorepetitivebending,smallcrackswillforminthesurfaceofindividualropewires,especiallyatthepointsofcontactwithotherwiresorwiththegrooveofasheaveordrum.Withincreasingnumberofbendingcycles,thecrackwillgrow,reducingtheloadbrearingwirecrosssection.Oncetheremainingwirecrosssectionisnolongerabletocarryitsshareoftheload,thewirewillfail.Atypicalfatiguebreakischaracterizedbyabreaksectionperpendiculartothewireaxis.Figure1showsaropewithfatiguebreaks.Figure2showsthecrosssectionofaropewirebrokenduetofatigue.Fig.1:Steelwireropeswithfatiguebreaks2BendingcyclesoversheavesOnebendingcycleforagivenropesectionisdefinedasachangefromastraighttoabentandbacktoastraightcondition(Fig.3a)orfromabenttoastraightandbacktoabentcondition(Fig.3b).Everytimetheropesectiontravelsoverasheave,itissubjectedtoonebendingcycle.Ofcourse,duringatypicallift,noteveryropesectionwilltraveloverthesamenumberofsheavesandontothedrum.Therefore,alongtheropelength,thewireropewillfatiguethemostinthosesectionswhichtraveloverthegreatestnumberofsheaves,i.e.whereitissubjectedtothegreatestnumberofbendingcycles.Fig.2:BreaksectionofaropewirebrokenduetobendingfatigueBendingcyclesoversinglelayer,grooveddrumsIfaropesectiontravelsonandoffagroovedsinglelayerdrum,itwillalsoundergoachangefromastraighttoabentandbacktoastraightcondition,i.e.accordingtothedefinition,itwillalsoundergoonebendingcycle.Butisabendingcycleonadrumcomparabletoabendingcycleonasheave?Foragroovedsinglelayerdrum,theanswerisYes.TestsandpracticalexperiencehaveshownthatabendingcycleonagroovedsinglelayerdrumwillcausethesameamountabFig.3:Definitionofonebendingcycle3ofropefatigueasabendingcycleonasheave,providedthelinepullsanddiametersarethesame.Inbothcases,theropewillbebentaroundsmooth,curvedsurfacesofthesamegeometry.Wecouldsaythattherope„doesnotknow“ifitisbentaroundasheaveoradrum.BendingcyclesovermultilayerdrumsIfaropesectiontravelsonandoffagroovedmultilayerdrum,itwillalsoundergoachangefromastraighttoabentandbacktoastraightcondition,i.e.accordingtothedefinition,itwillalsoundergoabendingcycle.Buthere,theconditionsaredifferent(Fig.4):Ropesectionsspoolinginthefirstlayerwillalsobebentaroundasmoothdrumsurface,butwhenthesecondlayercomesintheywillbespooledover,compressedanddamagedontheuppersidebythesecondropelayer.Ropesectionsspoolinginthesecondandhigherlayerswillbedamagedonallsides:firsttheywillbedamagedinZoneAduringthecontactwiththeneighbouringwrapwhenenteringthedrum(Fig.5).Thentheywillbebentaroundaveryroughsurfacecreatedbythepreviousropelayer,leadingtowiredamageinZonesB1andB2(Fig.6).Thenthenextwrapwillcomein,damagingtheropesectioninZoneC,anddisplacingtheropesection,leadingtoadditionalda-mageinZonesB1andB2(Fig.7).FinallythenextlayerwilldamagetheropesectioninZonesD1andD2attheside,or,ifwearelookingata