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附录1：英文原文SHEARERSINTRODUCTIONLongwallminingintheUnitedStatesisfinallybeginningtocarveoutasignificantpercentageofundergroundminingtonnage.AlthoughlongwallinstallationsarecontinuingthroughoutthecountryatlastcountinelevenstatestheconcentrationisintheEasterncoalfields,withWestVirginialeadingallstates.Asaresultofincreasedexperiencewithlongwallinstallationsunderdifferentcondition,certainimprovementsarebeingmade.Forinstance,roofsupportshieldsarebeingutilizedtoagreaterextent,andruggednessisbeingstressedinallareas.Modificationsarebeingconsideredinordertousethelongwallinothertypesofseamsandseamconditions.Evidentlylongwallusersliketheresultsthattheyhavebeengettingbecausetheyhavebeeninstallingmoresystems.Sincelongwallminingisobviouslygoingtoplayamuchlargerroleinthecoalminingindustryinthefuture,thereisagreatneedforacomprehensivebookthatpresents,systematically,everymajorsubjectinlongwallmining.MorethanadecadeofmodernlongwallminingintheUnitedStateshasdemonstratedthatitisinherentlysafeandcomplieseasilywithcurrentlaws.Itisalsohighlyproductive,provideditisproperlydesignedandoperated.However,thegrowthoflongwallmining,thoughsteady,hasbeenslow.Oneofthereasonsforthisisthelackofacomprehensivetechnicalbackgroundliteraturefortrainingpurposes.Thisbookattemptstofillsuchagap.Forthefirsttime,anyonewhowouldliketolearnmoreaboutlongwallminingcanfindallofthemajortopicsinonebook.Thus,thisbookisamilestoneinthedevelopmentoflongwallmining.SHEARERSLongwallequipmentconsistsofthreemajorcomponents:thehydraulicallypoweredroofsupport,thechainconveyor,andthecoal-cuttingmachine.Thetwodifferenttypesofcoal-cuttingequipmentusedincoalminesareshearersandplows.Plowsareusedinlowseams,42in.orless.Theunitconsistsofsteelconstructionequippedwithcarbon-tippedbits.Thispassivesteelunitisengagedtoaguidingsystemonthefaceconveyor.Anendlessroundlinkchainpoweredbysynchronizedelectricdrivesoneachendofthefaceconveyorpullstheplowbodyatspeedsbetween120and420ft/minalongtheface.Forthecuttingprocesstheplowhastobeforcedagainstthecoalface.Thisisdonebyhydrauliccylinderattachedtothegobsideofthefaceconveyorandtothebaseofthesupports,orbyaseparatehydraulicprop.Forcesofbetween1and3tonsareappliedpercylinder.Aplowdriveisattachedtoeachdriveframeofthefaceconveyor.Only30%to60%ofthedrivepowersuppliedtotheplowisusedforcuttingandloadingofcoal；theremainderislostinfriction.Thismeansthatthepowerlossisconsiderablyhigherthanthatofashearer,whichuses75%to85%ofitspowerfortheremovalofthecoal.Asaresult,ratherlargedrivesarerequiredatthefaceends.Althoughtherearemanymodels,theshearerhasseveralcommonbasiccomponents.Adouble-endedranging-drumshearer(Fig.8.1),forexample,consistsoffourmajorcomponents:electricmotors,gearheads,haulageunit(powerpack),andcuttingdrums.Theelectricmotorrangingfrom300to1000hp.(223-750kw)isthepowersourcefortheshearer.Itprovidespowertorunthehydraulicpumpsinthehaulageunitandthegearheadsforthecuttingdrum.Thelargecapacityshearersaregenerallyequippedwithtwoelectricmotors:oneofthehaulageunitandonegearheadandtheotherfortheothergearheadandotherancillaryequipment.Themotorscanberemotelycontrolled.Therearetwogearheads,oneontheleft-andtheotherontheright-handsideoftheshearer.Eachgearheadconsistsofagearheadgearboxandarangingarm.Thecuttingdrumislacedwithspiralvanesonwhichthecuttingbitsaremounted.Itsdiameterrangesfrom34to72in.(0.861.83m)withrotationalspeedsfrom30to105rpm.Thetrendsaretowardfewerbutlargerbitsandslowerdrumspeedforbettercuttingefficiencyandlesscoaldustproduction.Thedrumsarealsoequippedwithpowercowlstoincreasethecoalloadingefficiency.Thepowercowlisusuallylocatedbehindthecuttingdrum.Forthatreason,itcanberotatedafull180.Theelectricmotor,haulageunit,andgearheadboxescombinetoformtheshearersbodywhichismountedontheunderframe.Theunderframehasfourslidingshoes.Theface-sideshoesarefittedandrideontheface-sidetopguideofthefaceconveyorpan,andtheothertwogob-sideslidingshoesarefittedonaguidetubetopreventderailment.Thereamingspeedoftheshearerrangesfrom19to46ft/min(5.8-14.0m/min).Inaddition,theshearerisequippedwithauxiliaryhydraulicpumpsandcontrolvalvesforoperatingtherangingarmsandpowercowls,watersprayingdevices,cable,chainanchorageandtensioners,andsoon.TYPESOFMODERNSHEARERSSinceitsfirstappearancein1954,theshearerhasundergonecontinuouschangesbothincapabilityandstructure.Itisnowthemajorcuttingmachineinlongwallcoalfaces.Therearetwotypesofshearers,single-anddouble-drum.Intheearliermodels,thedruminthesingle-drumshearerismountedontheshearersbodyandcannotbeadjustedforheight.Thereforeitisnotsuitableforareaswherethereareconstantchangesinseamthicknessandfloorundulation.Thus,thesingle-endedfixed-drumshearerisusedmostlyforthinseams.Inordertoaccommodatethechangingofseamthicknessandfloorundulationthesingle-drumshearerswitharangingarmareused.Therangingarmcanberaisedupanddownbyhydrauliccontroldevices.Butwhentheseamexceedsacertainthickness,theshearercannotcuttheentireseamheightinonecutandareturncuttingtripisnecessarytocompleteafullwebcut.Furthermore,sincethedrumislocatedontheheadentryside,itgenerallyrequiresanicheinthetailentryside.Anicheisprecutfaceend,onewebdeepandashearerslengthlong.Withanicheatthefaceendtheshearercanturnaround.Nowadays,thedoubleranging-drumshearersareusedpredominantly.Theshearercutsthewholeseamheightinonetrip.Thetwodrumscanbepositionedtoanyrequiredheight(withinthedesignedrange)duringcuttingandloweredwellbelowthefloorlevel.Thearrangementofthedrumsenablesthewholeseamtobecutineitherdirectionoftravel,therebyensuringrapidfaceadvanceandshorteningroofexposuretime.Therearevarioustypesofdoubleranging-drumshearers.Basedonthelocationofthedrums,therearetwotypes:onewithonedrummountedoneachsideoftheshearersbodyandtheotherwithbothdrumsmountedononesideofthemachine.Theformertypeisthemostwidelyused.Itsadvantageisthatwithonedrumoneachsideoftheshearer,itcansumpineitherdirection.Duringthecuttingtrip,theleadingdrumcutstheupper70%oftheseamheightwhilethereardrumcutsthelower30%andcleansupthebrokencoalonthefloor.Thetwodrumsareapproximately23-33ft.(7-10m)apart.Whenthesheareristravelingintheoppositedirectiontothatofthefaceconveyor,thecoalcutbytheleadingdrumhastopassundertheshearersbody,whichincreasesthemovingresistanceoftheshearerandthefaceconveyorandcouldcausea“crowding”condition.Ifthebrokencoalistoolarge,itmayblocktheshearerandstoptheoperation.Ingeneral,whentheshearerandfaceconveyoraretravelingintheoppositedirections,approximately70%ofthecoaltakenbytheleadingdrumwillpassundertheshearer.Butwhentheyaretravelinginthesamedirection,thecoaltakendownbythereardrumtogetherwiththefloatcoalfromthefloorconstitutetheapproximately30%ofthecoalthathastopassundertheshearer.Theformercaseconsumes25%morepowerthanthelatter.Ascomparedtothesingle-endedshearer,theunderframeofthedouble-endedshearerishigher,therebyensuringasufficientcrosssectionforcoalpassage.Basedonthemethodofadjustingtheheightofthecuttingdrum,therearealsotwotypesofshearers:ranging-armshearerandgearheadshearer.Theformeroneiscommonlyused,whereasthelatteroneisarecentdevelopment.Theadvantageofthegearheadshearer(Fig.8.2)isthatthehaulage