NewWordsandExpressionsboiler['b??l?(r)]n.鍋爐furnace['f??n?s]n.爐膛（燃燒室）soot[s?t]n.煙灰saturatedsteam

飽和水蒸氣steamdrum

上汽包equivalent[??kw?v?l?nt]a.等量的，相當?shù)膒enetrate[?pen?tre?t]v.穿透，滲透hazardous[?h?z?d?s]a.危險的NewWordsandExpressionsscarcity[?ske?s?ti]n.不足blow-downvalve

排污閥scumvalve

上排污閥ventilation[vent??le??n]n.通氣chemicaldosingpump

化學加藥泵Aboilerisaclosedvesselinwhichwaterunderpressureisheatedandtransformedintosteam.Aboilerinoneformoranotherwillbefoundoneverytypeofship.Thoseonesusedonboardofshipsarecalledmarineboilers.Accordingtotheirfunctions,marineboilerscanbeclassifiedintotwotypes:mainboilersandauxiliaryboilers.

GeneralIntroduction

MainBoilersThemainboilersareusedtogeneratesuperheatedsteamathighpressuretodrivetheturbineorpropelthesteamship.Theauxiliaryboilers,whicharealsocalleddonkeyboilers,areusedtogeneratesaturatedsteamatalowpressurefortheauxiliarymachines.Nowadays,theauxiliaryboilersareusedextensivelyonmodernmerchantships.Theycanbefurtherdividedintothreetypes:oilfiredboilers,exhaustgasboilers,andcompositeboilers.

AuxiliaryBoilers

OilFiredBoilersTheoilfiredboilerstakeuseoftheenergyfromtheburningfueltoheatthefeedwater.Allofthemhaveafurnaceorcombustionchamberwherefuelisburnttoreleaseitsenergy.Airissuppliedtotheboilerfurnacetoenablecombustionofthefueltotakeplace.Alargesurfaceareabetweenthecombustionchamberandthewaterenablestheenergyofcombustion,intheformsofheat,tobetransferredtothewater(燃燒室和水之間的大表面積使燃燒能以熱的形式傳遞給水).Accordingtothefeaturesofevaporationsurface,theoilfiredboilerscanbedividedintowatertubeboilersandfiretubeboilers.

WaterTubeBoilersAsshownintheFig.12-1,inthewatertubeboilerthefeedwaterispassedthroughthetubesandthehotgasespassoverthem.Fuelisburntinsidethefurnacetocreatehotgaswhichheatswaterinthesteam-generatingtubes.Theheatedwaterthenrisesintothesteamdrum,wherethesaturatedsteamisdrawnoffthetopofthedrum.Coolwateratthebottomofthesteamdrumreturnstothefeedwaterdrumvialarge-boredowncomertubes,whereitpre-heatsthefeedwatersupply(上鍋筒底部的涼水（未汽化的水）通過大口徑降液管返回給水包，并在此預熱給水).Toincreaseeconomyoftheboiler,exhaustgasesarealsousedtopre-heattheairblownintothefurnaceandwarmthefeedwatersupply.

WaterTubeBoilersTheconstructionsofwatertubeboilers,whichusesmall-diametertubesandhaveasmallsteamdrum,enablethegenerationorproductionofsteamathightemperaturesandpressure(水管鍋爐的結(jié)構采用了小直徑管和小鍋筒，（這樣的結(jié)構）使得能夠在高溫和高壓下產(chǎn)生蒸汽).Theweightoftheboilerismuchlessthananequivalentfiretubeboilerandthesteamraisingprocessismuchquicker.Designarrangementsareflexible,efficiencyishighandthefeedwaterhasagoodnaturalcirculation.Thesearesomeofthemanyreasonswhythewatertubeboilerhasreplacedthefiretubeboilerasthemajorsteamproducer.

WaterTubeBoilers

FireTubeBoilersAsshownintheFig.12-2,inthefiretubeboilerthehotgasespassthroughthetubesandthefeedwatersurroundsthem.Theheatofthegasesistransferredthroughthewallsofthetubesbythermalconduction,andthenheatsthewatertocreatesteamultimately.Afiretubeboilerisalsocalledassmoketubeboiler.Thegeneralconstructionisasatankofwaterpenetratedbytubesthatcarrythehotfluegasesfromthefire.Thetankisusuallycylindricalforthemostpart,whichisthestrongestpracticalshapeforapressurizedcontainer.Thiscylindricaltankmaybeeitherhorizontalorvertical.

FireTubeBoilersFiretubeboiler1)Firetubeboilersareheavyincomparisontothewatertubeboilers;2)Itsefficiencyislowandcanonlygeneratelowormediumpressuresteam;3)Firetubeboilersarehavinglessefficientcombustion;4)GenerallyinFiretubeboilers,thethreatofthermal

stress

ishighbecausewatercirculationispoor;5)Itconsumesmorespaceandgenerationofsteamtakeslongertime;6)Furnaceandshellofthistypeofboilerissometimesubjectstodeformationsandthismayresultinthehazardousevent;7)Tubesofthistypeofboileraregenerallyhavingthelargerdiameterandhencetheyarejoinedwiththehelpofweldingonly;8)Waterisscarcityisnotaprobleminthistypeofboilerastubesarealwayshavingcoveringofwaterandwecanuseanytypeofwaterinordertogeneratesteam.

DifferencebetweenfireandwatertubeboilersWatertubeboiler1)Thesetypesofboilershavelightweightconstruction;2)Efficiencycomparedofthesmoketubeboilersismuchhigherandthosecanbeusedtogeneratethehighpressuresteam;3)Efficiencyofcombustioninthistypeofboilerisalwaysgood;4)Thermalstressesarelessasthewatercirculationisverygoodinside

thetubes;5)Steamgenerationtakesplaceinshortperiodoftimeandconsumeslessspace;6)Tubesarehavingsmalldiameterandinterference

methodissuedtofitthem;7)Waterlevelneedtobemaintainedinordertokeepsteamcomingup;8)Qualityofwaterthatcanbeusedinthisboilerisalwayshigherandbetterthensmoketubeboilers.

DifferencebetweenfireandwatertubeboilersTheexhaustgasboilersareinstalledonshipswhichadoptthedieselengineasthemainpropulsionplant.Theexhaustgastemperatureoflowspeedtwo-strokedieselengineisabout250-380oC,andforfour-strokemediumspeeddieselengineitisabout400oC.Thetemperatureofsaturatedsteamis165oCwhenthesteampressureis0.5MPaand194oCwhenthepressureis1.3MPa.Sincethetemperatureofexhaustgasismuchhigherthanthatofthesaturatedsteam,heatfromtheexhaustgasofmainenginecanberecoveredthroughtheexhaustgasboilertoheatthewatertogeneratesteam(由于廢氣的溫度比飽和蒸汽的溫度高得多，因此可以通過廢氣鍋爐回收來自主機廢氣的熱量，以加熱水產(chǎn)生蒸汽).

ExhaustGasBoilersAcompositeboileristhecombinationofoilfiredboilerandexhaustgasboiler.Thisarrangementpermitssteamgenerationeitherbyoilfiringwhennecessaryorbyusingtheengineexhaustgaswhentheshipisatsea.Atpresent,compositeboilersarethemostcommontypeofboilersusedonboard.Theyaregenerallybasedonfiretubeboilerdesigns.Asectionofthetubebankisseparatelyarrangedfortheengineexhaustgastopassthroughandexitviatheirownexhaustduct.

CompositeBoilers

BoilerMountingsThefollowingisabriefdescriptionofthemostimportantitemsoftheboilermountings.Thecomponentsmentionedinthissectionarereferringtothegeneralarrangementdrawingoftheboiler.Twosafetyvalvesarefittedtothepressurevesseloftheboiler.Theyareinstalledforsecurityreasons,anddesignedtopreventtheboilerpressurefromrisingabovethedesignvalue.Thesafetyvalvesmustbesuppliedwithwastesteampipesandeitherexpansiondevices,orbellows.

Safetyvalves

MainsteamvalveThemainsteamvalveisashutoff/non-returnvalve.Whenclosed,itisolatestheboilerfromthemainsteamline.Whenopen,itpreventssteamfromflowingbackwardsintotheboiler.

By-passvalveTheby-passvalveisashutoffvalve.Thepurposeofthevalveistoequalizethepressurebetweentheboilerandthesteamsystemwhenthemainsteamvalveisclosed.Pleasenotethattheby-passvalveisonlysuppliedforlargerboilers.Twogroupsoffeedwatervalvesareprovidedintheboiler.Eachgroupcomprisesashut-offvalveandanon-returnvalve.Theshut-offvalveintheordinarygroupmustbeopenwhentheboilerisinoperation,oriftheboilerisusedasasteamdrum.Theshut-offvalvesshouldbeclosedwhentheboilerisnotinuse.

Feedwatervalve

WaterlevelgaugesTwolocalwaterlevelgaugesareconnectedtothefrontoftheboiler,eachgaugebeingprovidedwithtwoshut-offvalvesandadrainvalve(兩個局部水位計連接到鍋爐的前部，每個水位計配有兩個截止閥和一個排水閥).Theshut-offvalves,fittedatthetopandbottomofthesightglass,haveaquick-closingmechanismtobeusedincaseofbrokenglass.Thepipesfromthedraincocksonthewaterlevelgaugemustleadtoanopendrain,visibleforinspection.Oneortwoblow-downvalvesaremountedatthebottomoftheboilerbody.Ifconnectedtoaseparatedrainagesystem,thevalvesareoftheballtype.Whenconnectedtoacommondrainagesystemtwovalvesareprovidedineachgroup,oneshut-offvalveandoneshut-off/non-returnvalve.Theshut-offfunctionisforsecurityandthenon-returnfunctionpreventssteam/waterfromflowingintoanemptyboilerbymistake.

Blow-downvalveScumvalveThescumvalveisacombinedshut-off/non-returnvalve.Intheeventofscumintheboiler,thisscumcanbeblownofffromthewatersurfacebyopeningthisvalve.AirvalveTheair/ventilationvalvelocatedontopoftheboilerisashut-offvalve.Itisnormallyclosedexceptwhentheboilerisbeingfilledorcompletelydrained.Theendofthedrainpipefromtheairvalvemustbevisibleinordertodeterminewhenwaterorsteamiscomingout.Asamplevalveisinstalledenablingconnectiontoasamplecoolerfortakingtestsamplestoperformboilerwateranalyses.

SamplevalveInspectionholeTwosmallinspectionholesareprovidedinthefurnacewalltoenableinspectionoftheburnerflame.Aproportionoftheairsupplyisbledofffromtheburnerfantocoolthewindowoftheinspectionhole,andpreventsootdeposits(一部分供氣從燃燒器風扇排出，以冷卻檢查孔的窗口，并防止煙灰沉積).ManholeAmanholeattheboilertopallowsinsideinspectionofthepressurevessel.Accesstothefurnaceisgainedbyswingingoutorremovingtheburnerunit.Accesstothefurnaceandsmokeoutletboxarepossiblethroughtheaccessdoorsplacedatthebottomofthefurnaceandatthesmokeoutletboxrespectively(可分別通過位于爐膛底部和排煙箱的檢修門進入爐膛和排煙箱).Bothaccessdoorsenableinspectionofthegeneratingtubebank.

AccessdoorsDrainforfurnaceThefurnacebottomisprovidedwithasocketfordrainofthewashingwater.ChemicalDosingPumpThechemicaldosingpumpisamicroprocessorcontrolledsolenoidmeteringpump.Thepumpoffershighlyaccuratereproduciblemeteringinthedosingofliquidchemic