起重机的类型英文.docx

起重机的类型英文.docx

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起重机的类型英文

TypeofCranes

Cranescanbeclassifiedintofourkinds,namely,（a）overheadtravelingcrane;（b）jibcrane;（c）bridgeorgantrycrane;and（d）cantilevercrane.

Overheadtravelingcrane.Consistsofagirderandatrolley.Thegirderissupportedateachendontruckscapableoftravelingonelevatedfixedtracks.Thetrolleyisequippedwithhoistingandothermechanism,capableoftraversingfromendtoendofsuchgirder.Thegirderandassociatedendcarriagesareknownasthebridge.

Suchcranesvaryinliftingcapacityfromabout2tonsto400tons,andinspanfrom20ftto150ft,ormore.Dependingonthepurposeforwhichitistobeused,thecranecanbeoperatedeitherfromacabinfixedtothebridgeorthetrolley,orfromtheground.Whentwotrolleysarefurnished,thesemayrunonacommontracksarrangedside-by-sideoroneabovetheothersothateachtrolleycan traversetheentirespan.

Jibcrane

Consistsofaninclinedmember,orjib,capableofsuspendingaloadatitsouterend.Thejibissupportedbyaropeorothermemberattachedtoaverticalmastofframe.Theoutreachofthejibcanbeconstantorvariable,andthecraneasawholemaybeeitherfixedormovable.

Includedinthiskindare:

mobileandcaterpillarcranes,builderstowercranes,wharfcranes,andmovablecranesmountedonhighpedestals,gantries,pontoonsandbarges.

Liftingcapacitiesvaryfrom1/2tonto300tonsormore,andoutreachesfromafewfeetto150ft.Cranesrequiredforhandlingheavymachineryandequipmentinshipyardsandatportsarefrequentlymountedonpontoons.

Bridgeorgantrycrane

Bridgeorgantrycrane.Consistsofabridgegirder,connectedatnearbothendstouprightmembers,whichmaybefixedorarrangedtotravelonafixedtrack,andtheloadissuspendedfromatrolleyorcrane,capableortraversingfromendtoendofthebridge.

Cranesofthiskindhaveliftingcapacitiesvaryingfromendtoendofthebridge.Whenusedingeneralandbulk-storageyards,thetracksmaybeofbroadornarrowgauge.Thetippingmomentoftheloadedcraneiskeptwithinproperlimitsbyacounterweightwhichismovedalonganindependenttrackonthebridgeabovethetrolley.

Cantilevercrane.

Cantilevercrane.Consistsofhorizontalandverticalmemberstheformer,knownasthecantilever,beingfixedtoortotatinginahorizontalplaneabouttheaxisoftheverticalmember.Onthecantileverisformedatrackwhichsupportsamovabletrolleyfromwhichtheloadissuspended.

Themechanismforhoistingandtraversingisusuallymountedonarearextensionofthecantilever.Althoughsuchcranesmaybefixedormovable,thoseoflargecapacityareusuallyfixed.Liftingcapacities,heightofliftandoutreachvarybetweenwidelimits.Whenusedforthefittingoutofships,lightloadsarehandledbyanauxiliaryhoistwhichmaybemountedonajibcranearrangedtotravelontrack.Themainliftingmechanismusuallyconsistsoftwowincheswhichcanbeoperatedindependentlyorinconcert.Atypicalfitting-outcranemaybeof250tonscapacitywithatotaloutreachof180ftandaliftingheightof200ft.

WharfCranes

Awharfcraneisanycranelocatedonawharforpier,andparticularlyadaptedtothetransferofcargobetweenthewharforpierandtheholdofthevesselalongside;itisalsocalledacargocrane,althoughthelattertermismoregeneral,asitcomprisesalsopartsofthecargo-handlinggearofavessel.Owingtothevaryingspacingofvesselhatchways,thewharfcraneinmostcasesmustbecapableofmovementalongthewharf,andhenceisgenerallymountedonarunway.Otherrequirementsaresufficienthorizontalreachtocoverthehatchway,sufficientlengthofhosttoraisetheloadfromthebottomoftheholdtoapointentirelyclearofthevessel,andrapidityandeconomyonoperation.

Typesmuchusedaswharfcranesaresingleordoubleportalgantriesortravelingbridgesonthewharfshedroof,carryingrotatingbridgesoncantilevergantrieswithfoldingextensionsoverthehatchways;gantrieswithinclinedcantileverjibs;alsoofthederricktype.

Inthehandlingofgeneralcargo,ascontrastedtobulkcargo,abroaderviewinanalyzingthesituationhastobetaken.Diversityofshape,sizeandweightprecludesthepossibilityofusingelevatorsorconveyorstoany greatextent,whilethenecessityofsortingandpilinginallottedplacesonthewharfmakesthetransporter,withitsratherlimitedareaofdischarge,unsuitable.

Thetravelingportalcrane,havingaboomcapableofbeingluffedaswellswung,ismuchusedasawharfcrane.Oneofthechiefdisadvantages,however,whichtheordinaryluffingcraneworksunderisthatwhentheboomisluffed-intheloadsuspendedfromthetopoftheboomissimultaneouslyraised;conversely,astheboomislowered,theloadfallsbyacorrespondingamount.This,obviously,isalossofworkandmeansanunnecessarilylargemotortoworktheluffinggear.

Toovercomethisobjectionanumberofdifferentdesignsofatypeofcraneknownasthelevel-luffingcranehavebeendeveloped,andthesecranesarenowextensivelyusedaswharfcranes.Inthistypeofcranesacompensatinggearinsomeformoranotherisprovidedwherebytheloadismadetotravelalongahorizontalpathirrespectiveoftheriseandfallofthehoistingpulleycausedbytheluffing-inoroutoftheboom.

Inselectingthemosteconomicalcraneforhandlinggeneralcargo,theaverageandmaximumweightsoftheindividualpiecesofcargomustbetakenintoconsideration.Thefrequencywithwhich60-tonliftsarelikelytobeencounteredisexceedinglylow,also20-tonliftsarequiteuncommon,sothatitwouldbeoutofreasontoinstallonanysingledockanumberofcranescapableofhandlingsuchweights.Thismostpopulargeneral-cargocranesinuseatpresentarefrom5~10tons’capacity.

MobileCranes

Thetwo-axlemobilecranesectorhasundergonearadicalre-appraisalinrecentyears.Whatstartedoffasa“minicrane”conceptinJapantocopewiththatcountry’sacutesiteandroadcongestionaboutfiveyearsagoultimatelyblossomedintoTadamoGovernmentsponsoredGrevo“conceptcraneofthefuture”-----hasnowtakenrootinEurope.

Thechiefpioneerofthetwo-axlere-thinkinEuropeiscommonlyheldtobeCompactTruckofSwitzerlandSpezialmaschinenofGermany.Althoughsinglecabtwoaxlemobilecranesarenotentirelynew-----bothColesandGottwaldmadecranesinyearsgoneby-----evenrivalmanufacturerssecretlyadmittobebeingimpressedbyCompactTruck’sCT2hydrostatic-drivemobilecrane,althoughsomequestionitseconomicviabilityinaworldoflowhire-outrates.CompactTruckisouttoprovethescepticswrong,however,andafterquietlybuildinguprentalfleetsineasternGermany,saleshavenowtakenoffthisfortheCT2abroadwitharound130unitsincurrentoperationaroundtheworld.

Unsurprisinglythen,Europe’sbigmobilemanufacturershavebeenlookingcloselyattheirownranges.ThisculminatedlastmonthwiththelaunchoMannesmannDemag’s25tAC75.LiketheCT2,theAC75hasasingleoperator/driver’scab,andhasanautomatictransmission.Thecranehasawidthof6.7m,clearanceheightof3mandispoweredbya156kWdieselengine.GVWintravelmodeis20t.Themainboom,whichfeaturesDemag’sovaloidprofiledesign,is25mlong,andtipheightwithboomextensionsis40m.

OnemajorrentalcompanytoputitsfaithintheAC75isBaldwinsoftheUK,whichhasorderedtenunitstobespreadaroundthecompany’sdepots,givingeachamachinesuitableforcranelireandmachineremovalandconstructionduties.BaldwinssaystheAC75fillsaneedforahighlyversatilemachinegivinghighutilisationinallsectorsofthemarket.

Nevertheless,noothercranemanufacturerhasyettoputtheCT2’shydrostaticdriveconceptintocommercialproduction-----afeaturemorecommonlyfoundoncrawlercranes,excavators,andfork-lifttruckswhichnormallyhaveamaximumspeedof40km/horless.CompactTrucksaystheCT2isthefirsthydrostatic-drivevehiclesuitableformotorwaydriving,withamaximumspeedof80km/h.Thecompanyclaimstohavedevelopedasystemthatpreventsthehydraulicoiloverheating.Onlyone-fifthoftheoilcapacityisusedfordrivingandanoilcoolingsystemhasbeenaddedforworkintropicalclimates,suchasThailand.

Theuseofhydrostatictechnologyallowsmuchmorefreedomofdesign,particularlywithplacementofthedieselengine-----whichissituatedattherearofthevehicle.Theengine,togetherwiththepumps,actsasacounterweightattherearoftheslewingstructure.

Thedesignalsoeliminatesboomoverhang,whichisnormalwithcraneswithconventionaldriveanddriver’scablocatedatthefront.Thevehiclehasanoveralllengthof6.49m,awidthof2.49m,andaheightof3.27mor2.7mwiththecabremoved.

Afterinitialscepticism,Europeanrentalhousesseemtobewarmingtothehydrostaticconcept,withapproximately80-90unitsinGermanhirefleets.Mostofthesaleshavebeensingleunitssoldtorentalcompanies.OtherunitsareworkinginTheNetherlands,Belgium,Finland,RussiaandSwitzerland.ThecompanyhasalsogainedafootholdintheFarEastandUSA.SyracuseEquipment,compactTruck’sUSdealer,hastakendeliveryofanumberofunitsandispromotingthemachineatanopendaythismonth.CompactTruck’sdealersinThailandandTaiwan-FLSandI-Cheong,respectively-----havealsobeenpromotingthemachine.

Thisre-appraisalofthetwo-axleproductsectorhasrecentlyseenDeutscheGrovestopproductionofthetwo-axle20tKMK2020followingitstakeoverofKruppMobilkranlastyear.TheKMK2020,launchedin1993,wasbasedintheoriginalGottwaldAMK31desig