VOLIIS6FWS.docx

VOLIIS6FWS.docx

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VOLIIS6FWS

SECTION–6

FEEDWATERsystem

SECTION–6

FEEDWATERSYSTEM

TABLEOFCONTENTS

CLAUSENO.DESCRIPTIONSHEETNO.

1.0.0SCOPEOFSUPPLYANDSERVICES3

2.0.0FEEDWATERHEATERS,BOILERFEEDPUMP

ANDDEAERATOR3

3.0.0PerformanceRequirements10

4.0.0DesignandConstruction10

5.0.0INSPECTION,TESTINGANDREPORTS14

6.0.0PERFORMANCEGUARANTEETESTS15

SECTION–6

FEEDWATERSYSTEM

1.0.0SCOPEOFSUPPLYANDSERVICES

Thebiddersarerequestedtonotethatonlythemajorequipmentarementionedbelow.Anyotherequipment/systemnotspecificallymentionedbelowbutmentionedelsewhereinthespecificationsandanyotherequipment/systemessentialforsmoothandefficientfunctioningofthesystemshallbeconsideredinthescopeofthebidderatnoextracost.

1.1.0Thisspecificationcoversingeneral,theminimumrequirementandguidelinetobeaddressedbythecontractorfordesign,manufacture,testingatmanufacturer’sworks,supply,transportandsupervisionoferection,testingandcommissioningoffeedwatersystem.

1.2.0Themajorcomponentsofthefeedwatersystemforeachturbineunitshallbe:

∙VerticalLowpressure（LP）heater&Horizontaldraincooler

∙SlidingpressureDeaerator（commonfor2x25MWUnit）

∙Three（3）Nos.（3x100%）boilerfeedpump,Commonfor2x25MWunit,eachpumpshallbesuitablefor1x25MWunit.

∙VerticalHighpressure（HP）heater

∙Relatedpipingandvalves

1.3.0Thefollowingsystemshallbecommonforboththeunits

∙SlidingpressureDeaerator

∙Three（3）Nos.（3x100%）boilerfeedpump,Commonfor2x25MWunit,eachpumpshallbesuitableforof1x25MWunit.

1.4.0Noequipmentiscommoninfeedwatersystemsof2x25MWunitsunlessotherwisespecificallymentioned.

2.0.0FEEDWATERHEATERS,BOILERFEEDPUMPANDDEAERATOR

2.1.0LPFeedheatersandDRAINCoolers

LPheatershallbeverticaltype.AdequateprovisionmustbemadetoprotecttheturbineagainstthebackflowofwaterfromtheLPfeedheaters.Thedrainlinesmustbeofadequatesizeand,areequippedwithadraincontrolsystem.Ifthewaterlevelcontinuestorise,alevelmonitormustclosethemotorizedshut-offvalveinthebleedlinetoLPfeedheateratthemaximumpermissiblewaterlevelandcondensatelineacrossLPheaterbypassed.TheLPheaterdrainlevelcontrolvalvescontinuouslydumpscondensatetoexhauststeamductdrainpotviadraincooler.TheLPHeatershallhavebypassstationwhichoperatesintheeventofcondensatereachinghighhighlevelinLPheater.Themaximumwaterlevelisalsotobeappliedfortheturbinetripthroughaseparatelevelmonitor..HeightofL.PheatershallbesuchthatitshallnotprojectaboveSTGBuildingoperatingfloor.

TheLPheatersshallhaveindividualbypassstations.

Theflowresistanceonthedrainsideofthecondensatecoolersmustnotexceedforanassumedflowatbursttubesof50%ofthemaximummaincondensateflow.ThesizingofLPheatercondensatedrainpipingshallbeasperlatestHEIstandards.SteamsidesafetyvalvemustbesuitablefordischargingmaincondensateflowasperHEIstandards.

TheLPfeedheatershallbeofstandardverticaltubeplatetypewithU-tubes.

Thecondensatedraincoolersshallbeofstandardhorizontaltubeplatetype.

Thewaterboxesmustbeprovidedwithflangedcoverstoallowfullaccesstothetubeplate.

Pipeconnectionsshallbeflangedonthemaincondensateside;allotherpipeconnectionsandallconnectionsonthevacuumsideshallbewelded.

Valvesandotherfittingsexceedingnominalsizeof25mm,whicharecontinuouslyorintermittentlyundervacuum,mustbeprovidedwithsealwaterconnections.

Shellandtubebundleshallbeequippedwitheffectivebaffleplatesandprotectionatthesteamanddrainsinlet.Particularcaremustbetakenforproperairextractionsothatnoairpocketscanforminsidetheheatexchangers.

2.2.0HPFeedheaters

Duringlow-loadoperationoftheturbine,whenthepressureinHPfeedheaterisnolongersufficienttodrivethecondensateintothefeedwatertank,thedrainisledtothecondenser（viaanemergencyflashtank）viaalow-loaddraincontrolsystem.TheautomaticswitchoverofthedrainfromthefeedwatertanktothecondenserandviceversashallbedonedependentonthepressuredifferencebetweenHPheaterandfeedwatertankconsideringasuitablehysteresischaracteristic.HeightofH.PheatershallbesuchthatitshallnotprojectaboveSTGBuildingoperatingfloor.

AdequateprovisionmustbemadetoprotecttheturbineagainstthebackflowofwaterfromtheHPfeedheaters.Ifthewaterlevelrisesexcessivelythefeedwaterlinemustbeautomaticallyby-passedandsimultaneouslythemotorizedshut-offvalvesandtheemergencycheckvalvesinthebleedlinesupstreamthefeedheatersaretobeclosed.Atthemaximumpermissiblewaterlevelanothermonitormustinitiateturbinetrip.

ItmustbepossibletooperatethefeedwaterbypassvalvesoftheHPfeedwatersbothmanuallyandautomatically.AutomaticoperationshouldbebymeansofseparatelevelmonitorsintheHPfeedheaters.

ThesafetyvalvetobeprovidedontheshellsideoftheHPfeedheatermustbecapableofdischargingthequantityoffeedwaterwhichwouldtheoreticallybedischargedthroughtwoopen-endedtubesundertheclosedvalveheadofthefeedwaterpumps.

TheHPfeedheatersshallbeofverticaldesign.IfconstructionsotherthanthetypesthisintendedtobeprovidedfortheHPfeedheaters（e.g.tubeplatetypes）thesuppliershallsubmitareferencelisttodemonstratethatheiswellexperiencedinthatfield.TheuseoftheseconstructionsissubjecttotheapprovaloftheOwner.

Thefeedwatertubesmustbebuttweldedtothecylindricalheadersinaccordancewithrecognizedpractice.Easyaccesstotheheadersmustbeassuredforplugginganytubeswhichmaybecomedefective.Theheatersmustbeequippedwithself-sealingcoversforthispurpose.

Allconnectionmustbewelded.Thefeedheatertubesmustbemanufacturedfromhigh-strengthsteel.Adequateprovisionmustbemadeinthedesignforthepossibleexpansionofthetubesandinternalsunderthedifferenttemperatureconditions.Thecompletetubebundlemustbestress-relieved.

Effectivebaffleplatesandprotectionmustbeincorporatedintheshellandtubebundleadjacenttothesteaminlet.

2.3.0FeedwaterTankandDeaeratorforFeedwaterSystem（Commonfor2x25MWUnit）

Thedeaeratorconnectedtothefeedwatertankshouldpreferablybeofthespraycumtraytypeorstroketype.HoweverCascade-typedeaeratorsandsimilartypeswillalsobeaccepted.Inallcasesthefeedwatertanksmusthaveawarming-upsteamline.

Thesizeofthedeaeratormustbesufficientforawaterflowofatleast1.1timesthemaximumboilerfeedwaterflowplusthemaximumfeedwaterinjectionquantityforboththeboilers.

Thefeedwatertankshallbeequippedwithacondensateventsteamcondenser,ifnecessaryaspermanufacturer’sstandards.

Ifthefeedwatertankpressurefalls,asupplementarysteamsupplyistakenfromtheauxiliarymanifold.Thissupplyistakenwhentheturbineisoutofoperationorduringstart-up/shut-downandduringlowloadoperation,inordertomaintaintherequiredminimumfeedwatertemperature.ThedrainfromtheHPfeedheatersandtherecirculationandleak-off-linefromthefeedwaterpumpsarealsoreturnedtothefeedtank.

Thedeaeratorspraynozzlesandthenozzlestrainershallbeofstainlesssteel.

Sufficientdistanceshallbeprovidedbetweenthenormalregulatedwaterlevelofthefeedwatertankandthemaximumpermissiblelevel.ExtractionlineMOVfordeaeratorshallclosewhenlevelinfeedwaterstoragetankreacheshigh-highlevel.Additionallysafetyvalvesmustbeprovidedtobeabletodischargesafelythemaximumpossibleincomingcondensateflow.

Toallowforpossiblesloppingofthecontentsofthefeedtank,ahorizontalimpactforceof10%ofthemaximumverticalloadmustbeassumed.

Inordertoavoidthedangerofcorrosion,diverterplatesshouldbefittedinthedeadcornersofthefeedtanktoimprovecirculation.Thewallthicknessforthefeedtankdeaeratorshallhaveacorrosionallowanceofatleast3mm.Thetankmustbesuitablystiffenedtosafelywithstandfullvacuum.

2.3.1Allinstrumentstapoffpointswithrootvalvesandstubsforthermowells

2.3.2AllnozzlesasperP&IDasminimum.

2.3.3Safetyvalvesandventvalvesasperapplicablestandards.

2.3.4Allfixingmaterialrequiredforthefasteningofthedeaeratorwithitssupportingstructuresincludingmatchingplate,ifany.

2.3.5Cleatsrequiredforfixinginsulationtothedeaeratorandstoragetank.

2.3.6Allcommissioningsparesandspecialtools&tackles.

2.3.7MandatorysparesandO&Msparesfor2yearsoftroublefreeoperation.

2.3.8Completeinstrumentation&controltomakethesystemcomplete.

2.3.9Allelectricalmotorsandpushbuttonstations.

2.3.10SPAREPARTS

EssentialO&Msparepartsfortwoyearsoftroublefreeoperationofthesystemshallbesuppliedandquotedseparatelyalongwithlistofspares.

2.3.11SPECIALMAINTENANCETOOLS&TACKLES

Twosetsofspecialtools&tacklesrequiredforoperation,maintenanceandrepair,neatlypackedinsteelboxes,completewithoperatingdetailsshallbesupplied.Listofmaintenancetools&tacklesbeingsuppliedshallalsobefurnished.

2.3.12DESIGNANDCONSTRUCTION

2.3.12.1Thedeaeratorshallbeeitherpreferablyspraycumtraytypeorstroketype.

2.3.12.2Spraynozzlesandtheirspringsshallbeofprovendesignandmadeofstainlesssteel.Itshallbedesignedtohaveminimumpressureloss.Theinternalsofthedeaeratorshallbearrangedforeasyinspection,andremovalformai