汽機培訓教材9(汽封系統(tǒng))

GLANDSEALSYSTEM在汽輪機轉(zhuǎn)子穿過外缸的部位，必需采取措施用以防止外部空氣漏入汽缸，從而影響排汽缸的真空，同時也必需防止汽缸內(nèi)蒸汽漏出汽缸，漏入前軸承箱容易呵斥油中帶水，漏至汽機房破壞汽機房環(huán)境。汽輪機的汽封系統(tǒng)就是為了完成這一功能而設(shè)置的。Measuresmustbetakenattheportionswheretheturbinerotorpassesthroughtheoutercasingtopreventtheairleakagefromoutsideintothecasingandaffectthevacuityoftheexhausthood.Inthemeantime,thesteaminsidethecasingmustalsobepreventedfromitsleakagetotheoutside,especially,tothefrontbearingboxtoleadtoamixingofthelubricationoilwithwaterandtotheturbinehousetodeteriorateitsenvironmentalconditions.Theglandsealsystemofasteamturbineisfurnishedjustforsuchapurpose.輔助蒸汽母管SteamsealcoolerSteamsealcoolerSteamsealcooler汽封系統(tǒng)圖本系統(tǒng)是高低壓分開供汽的汽封系統(tǒng).ThepresentsystemisaglandsealsystemcapableofsupplyingsteamtoHPandLPcylinderseparatelydeveloped.系統(tǒng)中主要設(shè)備有：高壓軸封供汽調(diào)理站、低壓軸封供汽調(diào)理站、高壓噴水減溫調(diào)理站、低壓噴水減溫調(diào)理站、各種截止閥、疏水閥等，連同汽封冷卻器、疏水擴容器等設(shè)備，共同構(gòu)成了該機組汽封系統(tǒng)。該系統(tǒng)可以維持汽封供汽母管的壓力在0.107～0.11MPa(A)之間，供汽溫度在121～150℃之間，控制部分可根據(jù)實踐情況接入控制室，經(jīng)過DCS系統(tǒng)調(diào)理各執(zhí)行機構(gòu)動作。Thesystemmainlyincludesthefollowingmainequipmentitems:HPglandsealsteamsupplyregulatingstation,LPglandsealsteamsupplyregulatingstation,HPwaterspraydesuperheatingregulatingstation,LPwaterspraydesuperheatingregulatingstation,variouscut-offvalvesanddrainvalves,glandsealcoolersanddrainflasktanksetc.Itcanexerciseafunctionofmaintainingthesteampressureinsidetheglandsealsteamsupplymainlinebetween0.107Mpaand0.11Mpa,thesteamtemperaturebetween121℃and150℃.ThecontrolsignalscanbesenttothecontrolroomaccordingtothespecificcasesandthencontroltheactionofvariousactuatorsthroughtheDCSsystem.轉(zhuǎn)子汽封GlandSealofRotor在汽缸兩端裝有汽封體和汽封圈，汽封圈上汽封齒環(huán)繞轉(zhuǎn)子，外表僅留有為防止在運轉(zhuǎn)過程中發(fā)生接觸的間隙。Glandcasingsandsealingringsareequippedatbothendsofthecylinderandtheteethonthesealringssurroundtherotorwithaclearancebeingkepttopreventanycontactbetweenthesaidteethandtherotorsurfaceduringtheturbineinoperation.在汽輪機啟動時，凝汽器抽真空，汽缸內(nèi)的壓力低于大氣壓力，供至“A〞腔室的汽封蒸汽在一側(cè)經(jīng)過汽封漏入汽輪機汽缸內(nèi)，在另一側(cè)漏入“B〞腔室，汽封抽汽器正常運轉(zhuǎn)，使“B〞腔室維持壓力稍低于大氣壓力，因此空氣經(jīng)過端汽封漏入“B〞腔室，構(gòu)成汽氣混合物，經(jīng)過一個與汽封抽汽器相連的接口，從“B〞腔室被抽出。(見圖1)Duringstartupofthesteamturbine,thecondenserisevacuatedandthepressureinthecylindersislowerthantheatmosphericpressure.Thesteamsuppliedtothe“A〞chamberoftheglandsealisleakedtothecylinderoftheturbineatonesideandto“B〞chamberatanotherside.Iftheairejectorfortheglandsealsisinnormaloperationtomaintainthepressurein“B〞chamberslightlylowerthantheatmosphericpressure,theairisleakedintothe“B〞chamberthroughtheglandsealattheend,formingasteamandairmixture.Thenthemixtureisevacuatedfrom“B〞chamberviaaportconnectedwiththeairejectorfortheglandseals(seeFig.1).隨著機組負荷的不斷提高，高中壓缸兩端的壓力逐漸添加，但因“C〞腔室與2號低壓加熱器(JD2)相連，所以高中壓汽封的“A〞腔室一直堅持送汽形狀；由于低壓缸壓力仍堅持一定的真空形狀，所以低壓汽封的“A〞腔室一直堅持送汽形狀。當除氧器能供汽時，那么切到正常運轉(zhuǎn)系統(tǒng)，即由除氧器來供汽(見圖2)。Withacontinuousincreaseoftheloadofthesteamturbine,thepressuresatbothendsofHPandIPcylinderwillgraduallyincrease.Asthe“C〞chamberisconnectedtothe2#LPheater(JD2),sothe“A〞chambersinHPandIPcylinderisalwayskeptinasteam-supplyingstate.DuetotheLPcylinderbeingmaintainedatavacuumstate,the“A〞chamberofLPglandsealsisalwayskeptinasteam-supplyingstate.Whenthedeaeratorhasanabilitytosupplysteam,thenormaloperationsystemshallbeputintoservice,i.e.supplyingsteambythedeaerator(seeFig.2).蒸汽壓力溫度控制安裝SteamPressureandTempController在汽輪機啟動和低負荷運轉(zhuǎn)形狀下〔普通低于40%負荷〕，輔助汽源經(jīng)過軸封壓力調(diào)理閥減壓及噴水減溫調(diào)理閥控制的減溫器減溫后，向汽封母管供蒸汽。隨著負荷不斷提高(約40%負荷左右)，當除氧器的汽平衡室壓力建立起來時，那么切換到正常運轉(zhuǎn)系統(tǒng)，即由除氧器來供汽。供汽母管配有熱電偶及壓力變送器(設(shè)計院選配)，母管的溫度和壓力變化是經(jīng)過與其相連的熱電偶和壓力變送器傳送的，信號傳到主控制室，由主控制室DCS系統(tǒng)完成對調(diào)理閥的溫度和壓力控制。Undertheconditionofthesteamturbineoperatinginthestartupstateandatalowload(generallylowerthan40%oftheratedload),theauxiliarysteamsourceshallsupplysteamtotheglandsealsteammainlineafterthesteampressurehasbeenreducedbytheglandsealsteampressureregulatingvalveandthesteamtemperaturehasbeendesuperheatedbyanattemperatorcontrolledbythewaterspraydesuperheatingregulatingvalve.Withacontinuousincreaseoftheload(toabout40%oftheratedload),whenasteampressureisestablishedinthesteamequilibriumchamberofthedeaerator,thenormaloperationsystemshallbeputintooperation,i.e.thesteamtotheglandsealsshallbesuppliedbythedeaerator.Thesteamsupplymainlineshallbeequippedwiththermocouplesandpressuretransmitters(selectedbyanelectric-powerdesigninginstitute).ThesignalsshowingthechangeofsteamtemperatureandpressureinthemainlinearetransmittedbythethermocouplesandpressuretransmitterstothemaincontrolroomandthentheDCScontrolsystemshallexerciseacontroloverthesteamtemperatureandpressurebyuseoftheregulatingvalvebasedonthesignals.汽封壓力調(diào)理閥能在一切運轉(zhuǎn)條件下以其DCS系統(tǒng)的給定壓力向各汽封供汽。軸封送汽調(diào)理閥壓力給定值為0.107～0.11MPa〔A〕?！惨蚰腹軌簱p未知可按實踐情況調(diào)整〕TheglandsealsteampressureregulatingvalveshallsupplysteamtovariousglandsealsatapressuresetbytheDCScontrolsystematalltheoperatingconditions.Theglandsealsteampressuresetpointbytheregulatingvalverangesfrom0.107～0.11MPa〔A〕(duetothepressurelossinthemainlinebeingunknown,onecanmakeanadjustmentaccordingtothespecificcase).供汽母管蒸汽溫度主要是由減溫器來控制的，減溫水來自于凝結(jié)水泵，減溫水量是由減溫水調(diào)理閥來控制的，溫度信號取自供汽母管的溫度，將溫度信號轉(zhuǎn)換為4～20mA電信號送到主控制室，由DCS系統(tǒng)來控制減溫水調(diào)理閥的執(zhí)行機構(gòu)，使供汽母管蒸汽溫度控制在121～150℃之間。Thesteamtemperatureinthesteamsupplymainlineismainlycontrolledbythedesuperheaterwiththedesuperheatingwatercomingfromthecondenstatewaterpumpandthedesuperheatingwaterquantitybeingcontrolledbythedesuperheatingwaterregulatingvalve.Thetemperaturesignalisobtainedfromthesteamsupplymainlineandthenconvertedintoa4～20mAelectronicsignalwhichissenttothemaincontrolroom.Basedontheelectronicsignal,theDCScontrolsystemtakescontrolovertheactuatorofthedesuperheatingwaterregulatingvalve,maintainingthesteamtemperatureinthesteamsupplymainlinebetween121℃and150℃.汽封冷卻器GlandCooler汽封冷卻器以稍低于大氣壓力即0.095MPa〔A〕的壓力接納閥桿及汽封“B〞腔室的漏汽，因此保證“B〞腔室不斷堅持負壓。Theglandsealcoolerreceivesthesteamleakagefromthestemsandtheglandseal“B〞chamberbyoperatingatapressureof0.095MPa〔A〕slightlylowerthantheatmosphericpressure,thuskeepingthe“B〞chamberbeingalwaysatanegativepressure.蒸汽過濾器SteamFilter為了防止外部物質(zhì)進入汽封和引起轉(zhuǎn)子的損壞，在每個汽封的供汽管道中運用了蒸汽過濾器，過濾器“Y〞形支管是程度安裝或置于管道的頂部，所以可以自行排空。Topreventforeignmattersfromenteringintotheglandsealsandcausingadamagetotherotor,thesteamfiltersareusedineverysteamsupplypipelinesoftheglandsealsandthe“Y〞-shapedbranchpipesshallbeinstalledhorizontallyorplacedonthetopofthepipes,thusensuringanairventbythefiltersthemselves.汽封系統(tǒng)的運轉(zhuǎn)OperationofGlandSystem冷態(tài)啟動Cold-stateStartup1.在汽輪機和進汽管道一切疏水閥翻開的情況下，投入盤車。Undertheconditionthatallthedrainwatervalvesonthesteamturbineandsteamintakingpipelinesareopened,theturninggearshallbeputintoservice.2.建立經(jīng)過凝汽器的水循環(huán)。Establishawatercirculationthroughthecondenser.3.啟動凝結(jié)水泵并建立經(jīng)過汽封抽汽器的冷卻水流。Startupthecondensatewaterpumpandestablishacoolingwaterflowratethroughtheairejectoroftheglandseals.4.開啟汽封抽汽器水室上的放氣口，直至全部殘留氣體排入大氣。Opentheairventonthewaterboxoftheairejectoroftheglandsealsuntilalltheresidualgasisdischargedtotheatmosphere.5.確認疏水擴容器殼體的疏水系統(tǒng)對凝汽器是翻開的。Makesurethatthedrainsysteminsidetheenclosureofthedrainwaterflashtankisopenedtothecondenser.6.確認汽封抽汽器水位報警器在運轉(zhuǎn)中，且儀表截止閥是翻開的。Makesurethatthewaterlevelalarmoftheairejectorfortheglandsealsisinoperationandthecut-offvalvesoftheinstrumentsareopened.7.確認每個汽封壓力、溫度調(diào)理站及旁路閥處于封鎖形狀。Makesurethateveryglandsealsteampressureandtemperatureregulatorstationsandbypassvalvesareintheclosingstate.8.確認啟動汽源溫度必需具有不小于14℃的過熱度。Makesurethatthetemperatureofthestartupsteamsourcecompulsorilyhasadegreeofsuperheatofnotlessthan14℃.9.確認調(diào)理閥入口的供汽管道中無水。Makesurethatthereisnowaterinthesteamsupplypipelinetotheinletoftheregulatingvalve.10.啟每個調(diào)理閥兩側(cè)的手動截止閥。Openthemanually-operatedvalvesatbothsidesofeachregulatingvalves.11.汽封系統(tǒng)在冷態(tài)啟動形狀時，輔助汽源向各個汽缸前后汽封供汽，蒸汽經(jīng)過軸封壓力調(diào)理閥減壓，再經(jīng)過減溫器減溫到121～150℃向高低壓前后軸封供汽。假設(shè)除氧器能供汽，那么切到正常運轉(zhuǎn)系統(tǒng)。Duringacold-statestartupoftheglandsealsystem,theauxiliarysteamsourceshallprovidesteamtotheglandsealsinthefrontandattherearofvariouscylinders.Thesteampressureisreducedbytheglandsealsteampressureregulatingvalveandthesteamtemperatureisdesuperheatedto121℃and150℃byanattemperator.Then,thesteamissuppliedtotheHPandLPfrontandrearglandseals.Ifthedeaeratorhasanabilitytosupplythesteam,thenthenormaloperationsystemshallbeputintoservice.12.當汽封供汽母管壓力建立并暖管后，立刻啟動汽封抽汽器。Whenthesteampressureinthesteamsupplymainlineoftheglandsealsisestablishedandthesaidmainlineiswarmedup,oneshallimmediatelystartuptheairejectorfortheglandseals.13.確認汽缸的每個汽封腔室均有低度真空。Makesurethateachchamberoftheglandsealsforthecylindershasavacuityatalowdegree.14.確認各汽封腔室內(nèi)蒸汽沒有漏入大氣，假設(shè)發(fā)現(xiàn)漏汽，那么提高汽封抽汽器真空，或調(diào)整壓力調(diào)理閥或各送汽支路上的送汽截止閥，調(diào)理各截止閥開度，以降低汽封母管的蒸汽壓力，直至停頓向外部漏汽。Makesurethatthesteaminvariousglandsealchambersdoesnotleaktotheatmosphere.Ifanyleakageofsteamisfound,thevacuitymaintainedbyuseoftheairejectorshallbeenhancedorthepressureregulatingvalveorthecut-offvalvesonvariousbranchlinesforsteamsupplyshallbeadjustedortheopeningdegreesofvariouscut-offvalvesshallberegulatedtoreducethesteampressureintheglandsealsteammainlineuntilthesaidleakageofsteamtotheoutsideisstopped.15.檢查汽封供汽母管的溫度，檢查高壓缸內(nèi)壁溫度與汽封腔室內(nèi)蒸汽溫度之差值，確保差值小于110℃，確保后汽封送汽腔室內(nèi)蒸汽溫度在121～150℃之間，檢查汽封蒸汽管路疏水能否通暢。Inspectthetemperatureintheglandsealsteamsupplymainline,inspectthetemperaturedifferencebetweentheinnerwalltemperatureoftheHPcylinderandsteamintheglandsealchambers,ensurethesaiddifferencetobelessthan110℃andthesteamtemperatureintherearglandsealsteamsupplychambertobebetween121℃to150℃.Inspecttheglandsealsteampipelinestoseewhetherthedraininsideflowsfreely.16.封鎖凝汽器的真空破壞門，啟動抽氣設(shè)備，并在凝汽器內(nèi)建立盡能夠高的真空，在每個汽封建立起最大流量之前，所需的汽封蒸汽量隨凝汽器真空的改善而添加。Closethevacuumbreakingvalve,startuptheairejectorequipmentandestablishavacuityashighaspossibleinthecondenser.Priortoanestablishmentofamaximumflowrateineachglandseals,thesteamamountnecessaryfortheglandsealswillincreasewithanincreaseofthevacuityinthecondenser.17.當負荷逐漸添加時，來自除氧器的蒸汽可以滿足高、低汽封供汽時，那么輔助汽源供汽切換到除氧器供汽。這樣高中壓汽封系統(tǒng)與低壓汽封系統(tǒng)相互獨立，整個系統(tǒng)相對穩(wěn)定。WhentheloadgraduallyincreasesandthesteamflowratefromthedeaeratorcanmeetthesteamamountrequiredbytheHPandIPglandsealsystem,thesteamcanbeswitchedoverfromsuppliedbytheauxiliarysteamsourcetosuppliedbythedeaerator.Insuchacase,theHPandIPglandsealsystemareindependentfromtheLPglandsealsystemandthewholesystemisrelativelystable.控制降負荷ControlLoadReduction在控制降負荷時，汽封母管的蒸汽壓力高于0.107MPa(A)，那么汽封系統(tǒng)維持正常形狀，高、低壓汽封供汽由除氧器供應(yīng)；當汽封母管壓力低于0.107MPa(A)時，即除氧器的汽源不能保證母管壓力時，改由輔助汽源供汽。Whentheloadreductioniscontrolledandthesteampressureintheglandsealsteammainlineishigherthan0.107Mpa(A),theglandsealsystemiskeptinanormaloperationstateandHPandLPglandsealsteamissuppliedbythedeaerator.Whenthesteampressureintheglandsealsteammainlineislowerthan0.107Mpa(A),i.e.thesteamfromthedeaeratorcannotmaintainthepressureinthemainline,thenthesteamshallbesuppliedbyanauxiliarysteamsource.汽輪機停機TurbineShutdown只需存在著堅持汽缸內(nèi)真空的必要，就必需向汽輪機各汽封提供密封蒸汽，在凝汽器的抽氣設(shè)備停頓運轉(zhuǎn)和凝汽器的真空完全消逝以前，不得切斷汽封供汽，否那么冷空氣流入會使轉(zhuǎn)子外表金屬急劇冷卻，而且還會導(dǎo)致熱的靜止的汽封體變形。Aslongasaneedforkeepingavacuityinthecylindersexists,oneshallsupplysteamtovariousglandsealsoftheturbine.Priortothestoppageoftheairextractionequipmentofthecondenserandafulllossofvacuityinthecondenser,thesteamsuppliedtotheglandsealsshallnotbecutoff,otherwise,coldairenteringintothesteamturbinewouldcauseanabruptcoolingoftherotorsurfacemetalandalsoresultinadeformationofthehotandstillglandcasings.汽輪機停機順序ShutdownSequence1.在機組盤車和汽封供汽來自外部汽源的情況下，確認凝汽器真空已完全消逝。Undertheconditionthatthesteamformaintainingtheturbineturningandtheglandsealsisfromthesteamsourceattheoutside,oneshallmakesurethatthevacuityinthecondenserhasbeenfullylost.2.封鎖汽封冷卻器風機。Closethefanoftheglandsealcooler.3.封鎖各汽封壓力調(diào)理閥兩側(cè)的手動截止閥。Closevariousmanually-operatedcut-offvalvesatbothsidesoftheglandsealsteampressureregulatingvalve.在切斷汽封冷卻器的風機后，應(yīng)立刻封鎖上述閥門，在汽封體內(nèi)無真空的情況下，汽封供汽的投入導(dǎo)致蒸汽漏入大氣，這些蒸汽會進入光滑油中，并凝結(jié)成為污染雜質(zhì)，積存在油箱中。Afterthefanoftheglandsealcoolerhasbeenstopped,oneshallimmediatelyclosealltheabove-mentionedvalves.Undertheconditionthatthesealcasingisatzerovacuity,iftheglandsealsaresuppliedwithsteam,thelatterwillbeescapedtotheatmosphereandalsotothebearingbox,mixedwiththelubricationoilandcoagulatedtopollutantsanddepositedintheoiltank.熱態(tài)啟動Hot-stateStartup熱態(tài)啟動形狀，機組轉(zhuǎn)子溫度接近滿負荷運轉(zhuǎn)工況下的轉(zhuǎn)子溫度，此時一切閥門形狀同冷態(tài)啟動，只是添加一股熱態(tài)啟動汽源(P=1.0MPa，T=450℃)，經(jīng)過高溫電動、手動截止閥后，向圖2中的高壓前汽封的“D〞腔室送汽。其它同冷態(tài)啟動送汽，假設(shè)除氧器能供汽，那么切到正常運轉(zhuǎn)系統(tǒng)。Hot-statestartupstatus:therotortemperatureofthesteamturbineshallapproximatetothatatthefull-loadoperationcondition.Insuchacase,thestatesofallthevalvesaresameasthe