高速带式输送机的设计外文翻译可编辑.docx

高速带式输送机的设计外文翻译可编辑.docx

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高速带式输送机的设计外文翻译可编辑

高速带式输送机的设计_外文翻译（可编辑）

附件A

esignofHighSpeedBeltConveyors

G.Lodewijks,TheNetherlands.

SUMMARY

Thispaperdiscussesaspectsofhigh-speedbeltconveyordesign.Thecapacityofabeltconveyorisdeterminedbythebeltspeedgivenabeltwidthandtroughingangle.Beltspeedselectionhoweverislimitedbypracticalconsiderations,whicharediscussedinthispaper.Thebeltspeedalsoaffectstheperformanceoftheconveyorbelt,asforexampleitsenergyconsumptionandthestabilityofit'srunningbehavior.Amethodisdiscussedtoevaluatetheenergyconsumptionofconveyorbeltsbyusingthelossfactoroftransport.Withvariationofthebeltspeedthesafetyfactorrequirementsvary,whichwillaffecttherequiredbeltstrength.Anewmethodtoaccountfortheeffectofthebeltspeedonthesafetyfactorispresented.Finally,theimpactofthebeltspeedoncomponentselectionandonthedesignoftransferstationsisdiscussed.

1INTRODUCTION

Pastresearchhasshowntheeconomicalfeasibilityofusingnarrower,fasterrunningconveyorbeltsversuswider,slowerrunningbeltsforlongoverlandbeltconveyorsystems.Seeforexample[I]-[5].Today,conveyorbeltsrunningatspeedsaround8m/sarenoexceptions.However,

velocitiesover10m/supto20m/saretechnicallydynamicallyfeasibleandmayalsobeeconomicallyfeasible.Inthispaperbeltspeedsbetweenthe10and20m/sareclassifiedashigh.Beltspeedsbelowthe10m/sareclassifiedaslow.

Usinghighbeltspeedsshouldneverbeagoalinitself.Ifusinghighbeltspeedsisnoteconomicallybeneficialorifasafeandreliableoperationisnotensuredatahighbeltspeedthenalowerbeltspeedshouldbeselected.

Selectionofthebeltspeedispartofthetotaldesignprocess.Theoptimumbeltconveyordesignisdeterminedbystaticorsteadystatedesignmethods.Inthesemethodsthebeltisassumedtobearigid,inelasticbody.Thisenablesquantificationofthesteady-stateoperationofthebeltconveyoranddeterminationofthesizeofconveyorcomponents.Thespecificationofthesteady-stateoperationincludesaquantificationofthesteady-staterunningbelttensionsandpowerconsumptionforallmaterialloadingandrelevantambientconditions.Itshouldberealizedthatfindingtheoptimumdesignisnotaone-timeeffortbutaniterativeprocess[6].

Designfine-tuning,determinationoftheoptimumstartingandstoppingprocedures,includingdeterminationoftherequiredcontrolalgorithms,anddeterminationofthesettingsandsizesofconveyorcomponentssuchasdrives,brakesandflywheels,aredeterminedbydynamic

designmethods.Inthesedesignmethods,alsoreferredtoasdynamicanalyses,thebeltisassumedtobeathree-dimensionalvisco-elasticbody.Athreedimensionalwavetheoryshouldbeusedtostudytimedependenttransmissionoflargelocalforceanddisplacementdisturbancesalongthebelt[7].Inthistheorythebeltisdividedintoaseriesoffiniteelements.Thefiniteelementsincorporatevisco-elasticspringsandmasses.Theconstitutivecharacteristicsofthefiniteelementsmustrepresenttherheologicalcharacteristicsofthebelt.Dynamicanalysisproducesthebelttensionandpowerconsumptionduringnon-stationaryoperation,likestartingandstopping,ofthebeltconveyor.

Thispaperdiscussesthedesignofhighbelt-speedconveyors,inparticulartheimpactofusinghighbeltspeedsontheperformanceoftheconveyorbeltintermsofenergyconsumptionandsafetyfactorrequirements.Usinghighbeltspeedsalsorequireshighreliabilityofconveyorcomponentssuchasidlerstoachieveanacceptablecomponentlife.Anotherimportantaspectofhigh-speedbeltconveyordesignisthedesignofefficientfeedinganddischargearrangements.Theseaspectswillbediscussedbriefly.

2BELTSPEED

2.1BELTSPEEDSELECTION

Thelowestoverallbeltconveyorcostoccurintherangeofbeltwidths

of0.6to1.0m[2].Therequiredconveyingcapacitycanbereachedbyselectionofabeltwidthinthisrangeandselectingwhateverbeltspeedisrequiredtoachievetherequiredflowrate.Figure1showsanexampleofcombinationsofbeltspeedandbeltwidthtoachieveSpecificconveyorcapacities.Inthisexampleitisassumedthatthebulkdensityis850kg/m3coalandthatthetroughangleandthesurchargeangleare35'and20'respectively.

Figure1:

Beltwidthversusbeltspeedfordifferentcapacities.

Beltspeedselectionishoweverlimitedbypracticalconsiderations.Afirstaspectisthetroughabilityofthebelt.InFigure1thereisnorelationwiththerequiredbeltstrengthrating,whichpartlydependsontheconveyorlengthandelevation.Thecombinationofbeltwidthandstrengthmustbechosensuchthatgoodtroughabilityofthebeltisensured.Ifthetroughabilityisnotsufficientthenthebeltwillnottrackproperly.Thiswillresultinunstablerunningbehaviorofthebelt,inparticularathighbeltspeeds,whichisnotacceptable.Normally,beltmanufacturersexpectasufficientlystraightrunifapproximately40%ofthebeltwidthwhenrunningempty,makescontactwiththecarryingidlers.Approximately10%shouldmaketangentialcontactwiththecenteridlerroll.

Asecondaspectisthespeedoftheairrelativetothespeedofthebulksolidmaterialonthebeltrelativeairspeed.Iftherelative

airspeedexceedscertainlimitsthendustwilldevelop.Thisisinparticularapotentialprobleminmineshaftswhereadownwardairflowismaintainedforventilationpurposes.Thelimitinrelativeairspeeddependsonambientconditionsandbulkmaterialcharacteristics.

Athirdaspectisthenoisegeneratedbythebeltconveyorsystem.Noiselevelsgenerallyincreasewithincreasingbeltspeed.Inresidentialareasnoiselevelsarerestrictedtoforexample65dB.Althoughnoiselevelsaregreatlyaffectedbythedesignoftheconveyorsupportstructureandconveyorcovers,thismaybealimitingfactorinselectingthebeltspeed.

2.2BELTSPEEDVARIATION

Theenergyconsumptionofbeltconveyorsystemsvarieswithvariationofthebeltspeed,aswillbeshowninSection3.Thebeltvelocitycanbeadjustedwithbulkmaterialflowsuppliedattheloadingpointtosaveenergy.Ifthebeltisoperatingatfulltonnagethenitshouldrunatthehighdesignbeltspeed.Thebeltspeedcanbeadjusteddecreasedtotheactualmaterialvolumeflowsuppliedattheloadingpoint.Thiswillmaintainaconstantfillingofthebelttroughandaconstantbulkmaterialloadonthebelt.Aconstantfillingofthebelttroughyieldsanoptimumloading-ratio,andlowerenergyconsumptionperunitofconveyedmaterialmaybeexpected.Thereductioninenergyconsumptionwillbeatleast10%forsystemswherethebeltspeedisvariedcompared

tosystemswherethebeltspeediskeptconstant[8].

Varyingthebeltspeedwithsuppliedbulkmaterialflowhasthefollowingadvantages:

Lessbeltwearattheloadingareas

Lowernoiseemission

Improvedoperatingbehaviorasaresultofbetterbeltalignmentandtheavoidanceofbeltliftinginconcavecurvebyreducingbelttensions

Drawbacksinclude:

Investmentcostforcontrollabilityofthedriveandbrakesystems

Variationofdischargeparabolawithbeltspeedvariation

Controlsystemrequiredforcontrollingindividualconveyorsinaconveyorsystem

Constanthighbeltpre-tension

Constanthighbulkmaterialloadontheidlerrolls

Ananalysisshouldbemadeoftheexpectedenergysavingstodeterminewhetheritisworththeeffortofinstallingamoreexpensive,morecomplexconveyorsystem.

3ENERGYCONSUMPTION

Clientsmayrequestaspecificationoftheenergyconsumptionofaconveyorsystem,forexamplequantifiedintermsofimumkW-hr/ton/km,totransportthebulksolidmaterialatthedesignspecificationsovertheprojectedroute.Forlongoverlandsystems,theenergyconsumption

ismainlydeterminedbytheworkdonetoovercometheindentationrollingresistance[9].Thisistheresistancethatthebeltexperiencesduetothevisco-elastictimedelayedresponseoftherubberbeltcovertotheindentationoftheidlerroll.Forin-plantbeltconveyors,workdonetoovercomesideresistancesthatoccurmainlyintheloadingareaalsoaffectstheenergyconsumption.Sideresistancesincludetheresistanceduetofrictiononthesidewallsofthechuteandresistancethatoccursduetoaccelerationofthematerialattheloadingpoint.

Therequireddrivepowerofabeltconveyorisdeterminedbythesumofthetotalfrictionalresistancesandthetotalmateriallift.Thefrictionalresistancesincludehysteresislosses,whichcanbeconsideredasviscousvelocitydependentfrictioncomponents.Itdoesnotsufficetolookjustattheimumrequireddrivepowertoevaluatewhetherornottheenergyconsumptionofaconveyorsystemisreasonable.Thebestmethodtocomparetheenergyconsumptionofdifferenttransportsystemsistocomparetheirtransportefficiencies.

3.1TRANSPORTEFFICIENCY

Thereareanumberofmethodstocomparetransportefficiencies.ThefirstandmostwidelyappliedmethodistocompareequivalentfrictionfactorssuchastheDINffactor.Anadvantageofusinganequivalentfrictionfactoristhatitcanalsobedeterminedforanemptybelt.Adrawbackofusinganequivalentfrictionfactoristhatitisnota'pure'

efficiencynumber.Ittakesintoaccountthemassofthebelt,reducedmassoftherollersandthemassofthetransportedmaterial.Inapureefficiencynumber,onlythemassofthetransportedmaterialistakenintoaccount.

Thesecondmethodistocomparetransportationcost,eitherinkW-hr/ton/kmorin$/ton/km.Theadvantageofusingthetransportationcostisthatthisnumberiswidelyusedformanage