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ELEVATORSAFETYGIVETHEMINERABRAKEABSTRACTOVERAFIVEYEARPERIOD,THEREWEREATLEAST18DOCUMENTEDCASESOFASCENDINGELEVATORSSTRIKINGTHEOVERHEADINSOMECASES,THEACCIDENTSRESULTEDINSERIOUSINJURIESORFATALITIESTHESEACCIDENTSOCCURREDONCOUNTERWEIGHTEDELEVATORSASARESULTOFELECTRICAL,MECHANICAL,ANDSTRUCTURALFAILURESELEVATORCARSAREFITTEDWITHSAFETIESTHATGRIPTHEGUIDERAILSANDSTOPAFALLINGCAR；HOWEVER,THESEDEVICESDONOTPROVIDEPROTECTIONINTHEUPWARDDIRECTIONRULESANDREGULATIONSAPPLYINGTOELEVATORSAFETYHAVECOMEUNDERREVIEWINRESPONSETOTHESEACCIDENTSSOMEGOVERNINGAUTHORITIESHAVEALREADYREVISEDTHEIRREGULATIONSTOREQUIREASCENDINGCAROVERSPEEDPROTECTIONTHISPAPERWILLDISCUSSBASICELEVATORDESIGN,HAZARDS,REGULATIONS,ANDEMERGENCYBRAKINGSYSTEMSDESIGNEDTOPROVIDEASCENDINGCAROVERSPEEDPROTECTIONINADDITION,ACASESTUDYREPORTONAPNEUMATICROPEBRAKESYSTEMINSTALLEDANDTESTEDONAMINEELEVATORWILLBEDISCUSSEDINTRODUCTIONELEVATORSINCORPORATESEVERALSAFETYFEATURESTOPREVENTTHECARFROMCRASHINGINTOTHEBOTTOMOFTHESHAFTSAFETIESINSTALLEDONTHECARCANPREVENTTHISTYPEOFACCIDENTFROMOCCURRINGWHENTHEMACHINEBRAKEFAILSORTHEWIREROPESSUSPENDINGTHECARBREAKHOWEVER,THEINHERENTDESIGNOFTHESAFETIESRENDERTHEMINOPERATIVEINTHEASCENDINGDIRECTIONINTHEUPWARDDIRECTION,THEMACHINEBRAKEISREQUIREDTOSTOPTHECAGEIRVHENANEMERGENCYCONDITIONOCCURSUNDERNORMALOPERATION,THEMACHINEBRAKESERVESONLYASAPARKINGBRAKEDTOHOLDTHECAGEATRESTHOWEVER,WHENANEMERGENCYCONDITIONISDETECTED,MODERNELEVATORCONTROLSYSTEMDESIGNSRELYSOLELYONTHEMACHINEBRAKETOSTOPTHECARINTHEUNITEDSTATESMININGINDUSTRY,THEACCIDENTHISTORYHASPROVENTHATTHISISNOTTHEBESTCONTROLSTRATEGY2,3THESEACCIDENTSOCCURREDWHENTHERETARDINGEFFORTOFTHEDRIVEMOTORWASDEFEATEDWHENTHEMECHANICALBRAKESWEREINOPERATIVETHISALLOWEDTHECOUNTERWEIGHTTOFALLTOTHEBOTTOMOFTHESHAFT,CAUSINGTHECARTOOVERSPEEDANDSTRIKETHEHEADFRAMETHEHIGHSPEEDELEVATORCRASHESINTOTHEOVERHEADSTRUCTURECAUSEDEXTENSIVEMECHANICALDAMAGEANDPOTENTIALLYFATALINJURIESELEVATORDESIGNABASICUNDERSTANDINGOFELEVATOROPERATIONISREQUIREDINORDERTOASSESSTHESAFETYHAZARDSPRESENTANDDETERMINETHEACCIDENTPREVENTMETHODSAVAILABLEFIGURE1SHOWSACOMPLETEVIEWOFAMINEELEVATORFIG1MICOELEVATORINATYPICALELEVATOR,THEEARISRAISEDANDLOEREDBYSIXTOEIGHTMOTOR–DRIVENWIREROPESTHATAREATTACHEDTOTHETOPOFTHECARATONEEND,TRAVELAROUNDAPAIROFSHEAVES,ANDAREAGAINATTACHEDTOACOUNTERWEIGHTATTHEOTHERENDTHECOUNTERWEIGHTADDSACCELERATINGFORCEWHENTHEELEVATORCARISASCENDINGANDPROVIDESARETARDINGEFFORTWHENTHECARISDESCENDINGSOTHATLESSMOTORHORSEPOWERISREQUIREDTHECOUNTERWEIGHTISACOLLECTIONOFMETALWEIGHTSTHATISEQUALTOTHEWEIGHTOFTHECARCONTAININGABOUT45OFITSRATEDLOADASETOFCHAINSARELOOPEDFROMTHEBOTTOMOFTHECOUNTERWEIGHTTOTHEUNDERSIDEOFTHECARTOHELPMAINTAINBALANCEBYOFFSETTINGTHEWEIGHTOFTHESUSPENSIONROPESGUIDERAILSTHATRUNTHELENGTHOFTHESHAFTKEEPTHECARANDCOUNTERWEIGHTFROMSWAYINGSUSPENSIONRICPCSORTWISTINGDURINGTHEIRTRAVELROLLERSAREATTACHEDTOTHECARANDTHECOUNTERWEIGHTTOPROVIDESMOOTHTRAVELALONGTHEGUIDERAILSTHETRACTIONTORAISEANDLOWERTHECARCOMESFROMTHEFRICTIONOFTHEWIREROPESAGAINSTTHEGROOVEDSHEAVESTHEMAINSHEAVEISDRIVENBYANELECTRICMOTORMOTORGENERATORMGSETSTYPICALLYPROVIDETODCPOWERFORTHEDRIVEMOTORNEWERSYSTEMSUSEASTATICDRIVECONTROLTHEELEVATORCONTROLSVARYTHEMOTORSSPEEDBASEDONASETOFFEEDBACKSIGNALSTHATINDICATETHECARSPOSITIONINTHESHAFTWAYASTHECARAPPROACHESITSDESTINATION,ASWITCHNEARTHELANDINGSIGNALSTHECONTROLSTOSTOPTHECARATFLOORLEVELADDITIONALSHAFTWAYLIMITSWITCHESAREINSTALLEDTOMONITOROVERTRAVELCONDITIONSTHEWORSTFEAROFLITANYPASSENGERSISTHATTHEELEVATORWILLGOOUTOFCONTROLANDFALLTHROUGHSPACEUNTILITSMASHESINTOTHEBOTTOMOFTHESHAFTTHEREARESEVERALSAFETYFEATURESINMODERNELEVATORSTOPREVENTTHISFROMOCCURRINGTHEFIRSTISTHEHIGHSTRENGTHWIREROPESTHEMSELVESEACH0625INDIAMETEREXTRAHIGHSTRENGTHWIREROPECANSUPPORT32,000LB,ORABOUTTWICETHEAVERAGEWEIGHTOFAMINEELEVATORFILLEDWITH20PASSENGERSFORSAFETYSSAKEANDTOREDUCEWEAR,EACHCARHASSIXTOEIGHTOFTHESECABLESINADDITION,ELEVATORSHAVEBUFFERSINSTALLEDATTHESHAFTBOTTOMTHATCANSTOPTHECARWITHOUTKILLINGITSPASSENGERSIFTHEYARESTRUCKATTHENORMALSPEEDOFTHEELEVATORASPREVIOUSLYDISCUSSED,MODERNELEVATORSHAVESEVERALSPEEDCONTROLFEATURESIFTHEYDONOTWORK,THECONTROLSWILLDISCONNECTTHEMOTORANDAPPLYTHEMACHINEBRAKEFINALLY,THEELEVATORITSELFISEQUIPPEDWITHSAFETIESMOUNTEDUNDERNEATHTHECARIFTHECARSURPASSESTHERATEDSPEEDBY15TO25,THEGOVERNORWILLTRIP,ANDTHESAFETIESWILLGRIPTHEGUIDERAILSANDSTOPTHECARTHISWASTHEINVENTIONTHATMADEELEVATORTRANSPORTATIONACCEPTABLEFORTHEGENERALPUBLICSAFETYHAZARDSAHISTORICALPERSPECTIVEOFELEVATORDEVELOPMENTCANACCOUNTFORTODAYSPROBLEMSWITHELEVATORSAFETYRULESANDREGULATIONS4INTHEBEGINNINGOFMODERNELEVATORHISTORY,ITWASREALIZEDTHATALTHOUGHTHEREWERESEVERALFACTORSOFSAFETYINTHESUSPENSIONROPEDESIGN,THEQUALITYOFCONSTRUCTIONANDPERIODICINSPECTIONCOULDNOTBEASSUREDTHEREFORE,THEELEVATORCARWASEQUIPPEDWITHRELIABLESTANDBYSAFETIESTHATWOULDSTOPTHECARSAFELYIFTHESUSPENSIONROPESFAILEDIN1853,ELISHAOTIS,ANEWYORKMECHANIC,DESIGNEDANDDEMONSTRATEDANINSTANTANEOUSSAFETYCAPABLEOFSAFELYSTOPPINGAFREE–FALLINGCARTHISADDRESSEDTHEHAZARDSHOWNINFIGURE2LATERON,ITWASREALIZEDTHATPASSENGERSMAYBEINJUREDWHENTHECAROVERSPEEDSINTHEDOWNDIRECTIONWITHSUSPENSIONROPESINTACT,ASSHOWNINFIGURE3TOPREVENTTHISHAZARD,ANOVERSPEEDGOVERNORWITHGRADUALLYAPPLIEDSAFETIESWASDEVELOPEDITDETECTEDTHEOVERPEELINGCONDITIONANDACTIVATEDTHESAFETIES
