QBT 2551-2021《Cast iron dryers used in paper machinery 造纸机械用铸铁烘缸》

ICS85.100CCSY91

LightIndustryStandardofthePeople's

RepublicofChina

QB/T2551—2021ReplaceQB/T2551—2008,QB/T2556—2008

Castirondryersusedinpapermachinery造纸机械用铸铁烘缸

（EnglishTranslation）

Issuedate:2021-05-17Implementationdate:2021-10-01

IssuedbyMinistryofIndustryandInformationTechnologyofthePeople'sRepublicofChina

I

QB/T2551—2021

Foreword

SAC/TC101isinchargeofthisEnglishtranslation.IncaseofanydoubtaboutthecontentsofEnglishtranslation,theChineseoriginalshallbeconsideredauthoritative.

ThisdocumentisdraftedinaccordancewiththerulesgivenintheGB/T1.1—2020Directivesforstandardization—Part1:Rulesforthestructureanddraftingofstandardizingdocuments.

ThisdocumentreplacestheQB/T2551—2008TechnologicalconditionofcastirondryersusedinpapermachineryandtheQB/T2556—2008Designdocumentincastirondryersusedinpapermachineryinwhole.Inadditiontoanumberofstructuraladjustmentsandeditorialchanges,thefollowingtechnicaldeviationshavebeenmadewithrespecttotheQB/T2551—2008andtheQB/T2556—2008.

——Changingthenameofthedocument;

——Adjustingthedesignpressureinthe"Scope"toClause5(seeClause5,Clause1oftheQB/T2551—2008andClause1ofQB/T2556—2008);

——Changingthematerialrequirementsforcastirondryers(seeClause6,Clause3oftheQB/T2551—2008andClause4ofQB/T2556—2008);

——Addingtherelationshipbetweentheadditionalamountofdryerthicknessandtheexpectedservicelife(see7.3.5);

——Adding"insulationofendcovers"(see7.13);

——Addingtherequirementsfortheremovalofresidualstresses(see7.12and8.1);

——Changingthedefecttreatmentrequirements(see8.3and8.4,seeQB/T2551—2008,3.4);——Adding"Inspectionrules"(seeClause10).

ThisdocumentwasproposedbyChinaNationalLightIndustryCouncil.

ThisdocumentwaspreparedbySAC/TC101(nationaltechnicalcommitteeonLightIndustryMachineryofstandardizationadministrationofChina).

Thepreviouseditionsofthisdocumentareasfollows:

——ThepreviouseditionsofthereplaceddocumentQB/T2551—2008areasfollows：

.Thefirsteditionwasissuedin1988asZBY91003—1988；

.ThefirsteditionwastransformedintoQB3662—1999in1999;

II

QB/T2551—2021

.ThefirsteditionwasrevisedasQB2551—2002in2002，andthesecondrevisionwasissuedin2008.

——ThepreviouseditionsofthereplaceddocumentQB/T2556—2008areasfollows：

.Thefirsteditionwasissuedin1989asZBY91008—1989；

.ThefirsteditionwastransformedintoQB3663—1999in1999;

.ThefirsteditionwasrevisedasQB2556—2002in2002，andthesecondrevisionwasissuedin2008.

——Thisisthethirdrevisededition.TheQB/T2551—2008andQB/T2556—2008wereamalgamated.

1

QB/T2551—2021

Castirondryersusedinpapermachinery

1Scope

Thisdocumentspecifiesthetermsanddefinitions,basicrequirements,materials,design,fabrication,testmethods,inspectionrules,marking,packaging,transportationandstorageofcastirondryersusedinpapermachinery.

Thisdocumentisapplicabletodryersandblanketdryers(hereinaftercollectivelyreferredtoas"dryers")withanoutsidediameterofnotlongerthan4600mmforpapermachines,cardboardmachinesandpulpboardmachines.

2Normativereferences

Thefollowingreferencedocumentsareindispensablefortheapplicationofthisdocument.Fordatedreference,onlytheeditioncitedapplies.Forundatedreferences,thelatesteditionofthereferenceddocument(includinganyamendments)applies.

GB/T35,Squareheadboltswithsmallhead

GB/T150.1,Pressurevessels—Part1:GeneralrequirementsGB/T150.2,Pressurevessels—Part2:Materials

GB/T191,Packaging—PictorialmarkingforhandlingofgoodsGB/T699,Qualitycarbonstructuresteels

GB/T1348—2019,SpheroidalgraphiteironcastingsGB/T3077,Alloystructuresteels

GB/T4272,GeneralprinciplesforthermalinsulationtechniqueofequipmentandpipesGB/T5782,Hexagonheadbolts

GB/T6170,Hexagonalnuts,style1GB/T9439—2010,GreyironcastingsGB/T13306,Plates

2

QB/T2551—2021

NB/T47013.4—2015,NondestructivetestingofpressureequipmentsPart4:Magneticparticletesting

NB/T47013.5—2015,NondestructivetestingofpressureequipmentsPart5:PenetrationtestingQB/T3917—1999,Dynamicbalancingofrollsanddryersofpapermachine

3Termsanddefinitions

Forthepurposesofthisdocument,thefollowingtermsanddefinitionsapply.

3.1

pressure

TheforceverticallyactingonthevesselperunitsurfaceareaNOTEGaugepressure,unlessotherwisedefined.

[Source:GB/T150.1—2011,3.1.1,Modified]

3.2

operatingpressure

Undernormaloperatingconditions,theachievablemaximumpressure(3.1)atthetopofthedryer[Source:GB/T150.1—2011,3.1.2,Modified]

3.3

designpressure

Themaximumpressure(3.1)setforthedryer

NOTEItisusedtogetherwiththecorrespondingdesigntemperaturetobeusedasthedesignloadingconditionsanditsvalueshallnotbelowerthantheoperatingpressure(3.2).

[Source:GB/T150.1—2011,3.1.3,Modified]

3.4

designtemperature

Whenadryerisundernormaloperatingconditions,thesetmetaltemperatureofitscomponents(theaveragetemperaturealongthemetalsectionofthecomponents)

3.5

requiredthickness

Thethicknesscalculatedaccordingtothecorrespondingformulae

NOTEWhennecessary,itshallincludethethicknessrequiredbyotherloads.[Source:GB/T150.1—2011,3.1.10]

3.6

minimumrequiredfabricationthickness

3

QB/T2551—2021

Theminimumthicknessofensuringthedesignrequirements,afterthefabricationofthepressurecomponents

NOTETheminimumthicknessofcylindershellaftermachiningandassembling.[Source:GB/T150.1—2011,3.1.14]

3.7

safetyfactor

Theminimumfactortodeterminetheallowablestressforthemetalmaterialofthedryer(cast

ironparts,studsandbolts)

4Symbols

Forthepurposesofthisdocument,thefollowingsymbolsapply.

α:Anglebetweentheconenecksectionandthecylindershell,(°).C:Additionalthicknessofthecylindershell,mm.

D:Calculatedcross-sectionaloutsidediameterofthejournal,mm.Db:Centercirclediameteroftheboltsintheendcover,mm.

Do:Outsidediameterofthecylindershell,mm.

D1:Rabbetdiameteroftheendcover,mm.d:Insidediameterofthejournal,mm.

df:Nominaldiameterofboltwhichconnectsthecylindertotheendcover,mm.di:Rootdiameterofboltwhichconnectscylindertotheendcover,mm.

δc:Calculatedthicknessofthecylindershell,mm.δd:Designthicknessofthecylindershell,mm.

δf:Flangesectionthicknessofthecylinder,mm.δf1:Flangesectionthicknessoftheendcover,mm.δm:Maximumthicknessofcastings,mm.

FA:Supportingreactionforceonthedrivingsideofthedryer,N(maximumload,includingthedeadload,thecondensateweight,thefabrictensionload,etc.).

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QB/T2551—2021

K:Stressintensificationfactor,equalto1.2(includingthetemperaturedifferenceloadofthethermalstresscausedbythetemperaturedifferencebetweeninnerandouterofthecylindershell).

K1:Empiricalconstant,equalto2.4.

L:Distancefromthebearingcenteratthedrivingsideofthedryertothecalculatedsection,mm.

l:Conenecklengthatthediscontinuityofthecylindershell,mm.

l1:Distancefromthecentercircleofthebolttotheinsidediameterofthecylindershell,mm.

n:Quantityofboltsconnectingcylindertotheendcover.p:Designpressure,MPa.

P0:Internalaxialforceloadontheendcover,N.R:Outsideradiusofthecylindershell,mm.

Rm:Tensilestrengthofthecastiron,MPa.R1,R2,R3:Arcradiusoftheendcover,mm.

r:Arcradiusatthegeometricdiscontinuityofthecylindershell,mm.σ:Calculatedstressvalue,MPa.

[σ]:Allowabletensilestrengthofcastironmaterial,MPa.[σ1]:Allowablestressofconnectionbolts,MPa.

t1:Heatingorcoolingrateperunittime,℃/h.t2:Coolingrateperunittime,℃/h.

V1:Constant,equalto6250mm·℃/h.V2:Constant,equalto1250mm·℃/h.SomesymbolsseeFigure1.

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QB/T2551—2021

Figure1—Castirondryer

5General

5.1Thedryershallbemanufacturedaccordingtothedesigndrawingsandtechnicaldocuments

approvedbytheprescribedprocedures.

5.2Thedesignpressureofthegreycastirondryershallnotbegreaterthan0.8MPa,thescopeofthedesigntemperatureisbetween10℃to200℃.

5.3Thedesignpressureofthespheroidalgraphitecastirondryershallnotbegreaterthan

1.1MPa,thescopeofthedesigntemperatureisbetween0℃to250℃.

5.4Thecastironmaterialgradesandapplicabledesignpressureusedforthedryershallmeet

thoseasspecifiedinTable1.

Table1—Applicabledesignpressuresformaterialgrades

Inmegapascal

Materialgrades

Designpressure

HT200

0to0.3

HT250

0to0.5

HT300

0to0.8

HT350

0to0.8

QT350-22R

0to0.8

QT350-22L

0to0.8

QT400-18R

0to1.1

QT400-18L

0to1.1

5.5Forthecastirondryerswithoneofthefollowingconditions,thefiniteelementanalysisdesignshallbecarriedout:

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QB/T2551—2021

a)Theoutsidediametergreaterthan3800mm;

b)Thedesignpressuregreaterthan0.8MPa;

c)Theoutsidediameternotlessthan2000mmanddesignpressuregreaterthan0.5MPa.

5.6Whenthecastirondryer'soutsidediameterisgreaterthan3800mmorthedesignpressure

greaterthan0.8MPa,thestresstestandthesafetyevaluationshallbecarriedoutalongwiththehydrostatictest.

6Materials

6.1Thesafetyfactorofthegreycastironmaterialusedforthepressurecomponentsofthe

dryeris10.Thesafetyfactorofthespheroidalgraphitecastironmaterialis8.Thesafetyfactorofthematerialusedforthestuds(includingbolts)shallmeetthoseasspecifiedin

GB/T150.1.

6.2ThegreycastironmaterialusedforthedryershallmeetthoseasspecifiedinGB/T9439

—2010andthespheroidalgraphitecastironmaterialshallmeetthoseasspecifiedinGB/T1348—2019.

6.3Themechanicalpropertiesofthemanholecovermaterialshallnotbelowerthanthe

mechanicalpropertiesoftheendcovermaterial,andthemechanicalpropertiesoftheendcovermaterialshallnotbelowerthanthemechanicalpropertiesofthecylindermaterial.ThematerialofthesteelmanholecovershallmeetthoseasspecifiedinGB/T150.2.

6.4Ifthereisanyspecialrequirementforanymaterialforthedryer,itcanbeagreedbetween

manufacturerandpurchaser,andshallnotbelowerthanthegradeandthecorrespondingmechanicalpropertyindexasspecifiedinthisdocument.

6.5Theallowabletensilestressofthegreycastironmaterialusedforthecylinderandthe

endcovershallmeetthoseasspecifiedinTable2.TheallowabletensilestressofthespheroidalgraphitecastironmaterialshallmeetthoseasspecifiedinTable3.

Table2—Allowabletensilestressesofgreycastironparts

Inmegapascal

Material

Rm（min）

Allowabletensilestress[σ]

HT200

200

20

HT250

250

25

HT300

300

30

HT350

350

35

NOTERm(min)istheminimumtensilestrengthRm(mandatoryvalue)valueforasinglecasttestbartensile

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QB/T2551—2021

testintheGB/T9439—2010.

Table3—Allowabletensilestressesofspheroidalgraphitecastironparts

Inmegapascal

Material

Rm（min）

Allowabletensilestress[σ]

QT350-22R

350

43.75

QT350-22L

350

43.75

QT400-18R

400

50

QT400-18L

400

50

NOTERm(min)istheminimumtensilestrengthRm(mandatoryvalue)valueforasinglecastsampletensiletestintheGB/T1348—2019.

6.6ThehexagonheadboltsusedforthedryershallmeetthoseasspecifiedinGB/T5782.The

squareheadboltswithasmallheadshallmeetthoseasspecifiedinGB/T35.TheperformancegradeoftheboltsshallmeetthoseasspecifiedinTable4.

Table4—Performanceclassesofbolts

Outsidediameterofdryer

D0

mm

Designpressureofthe

dryerp

MPa

Nominaldiameterof

boltdf

mm

Performanceclass

800～1500

0.3～0.5

M20～M27

≥5.6

>1500～4600

>0.3～0.5

M24～M42

≥8.8

>1500～4600

>0.5～0.8

M24～M56

≥8.8

>1500～4600

>0.8～1.1

M24～M56

≥10.9

6.7Forthedryerwithacentershaftstructure,whentheconnectionofthecentershaftis

studs(includingbolts),theconnectorsshallmeetthoseasspecifiedinTable4,Table5andTable6.

6.8Thestandardsandallowablestressforstudsmaterial(includingbolts)aspressure

componentsshallmeetthoseasspecifiedinTable5.

Table5—Standardsandallowablestressforboltsmaterial

Grade

Steelrodstandard

Usagestatus

Boltsize

Operatingtemperature/℃

100

150

200

250

Allowablestress/MPa

20

GB/T699

Normalized

≤M22

81

78

73

—

M24～M27

84

80

74

—

35

GB/T699

Normalized

≤M22

105

98

91

82

M24～M27

106

100

92

84

8

QB/T2551—2021

40Cr

GB/T3077

Quenchedandtempered

≤M22

176

171

165

162

M24～M42

189

183

180

176

35CrMoA

≤M22

190

185

179

176

M24～M48

206

199

196

193

M52～M56

229

221

218

214

6.9Thenutsmatchedwiththestuds(includingbolts)asspecifiedin6.8shallmeetthose

asspecifiedinGB/T6170,andtheirperformanceclassshallmeetthoseasspecifiedinTable6.

Table6—Matchingtableforcarbonsteelandlowalloysteelnutswithbolts

Boltsgrade

Nutsmaterial

Steelgrade

Standards

Nominal

diameterofnuts

Usagestatus

Performanceclass

20

10、15

GB/T699

M20～M27

Normalized

≥5

35

20、25

GB/T699

M20～M27

Normalized

≥5

40Cr

40Mn、45

GB/T699

M20～M42

Normalized

≥8

35CrMoA

30CrMoA

GB/T3077

M20～M56

Quenched-tempered

≥8

7Design

7.1Load

Internalpressureshallbetakenintoconsiderationduringdesigning.

Thefollowingloadalsoshallbeconsideredwhennecessary:

a)Theself-weightofthedryer(includingtheinternalcomponents),aswellasthegravityloadoffilledwaterundernormaloperationorthehydrostatictest.

b)Externalloadonthedryerfromthedryerfeltandthetouchrollorthepressingroll;

c)Forcesfromrotaryjointsandothertransmissioncomponents;

d)Forcescausedbythedifferencesoftemperaturegradientorthermalexpansion;

e)Impactloadscausedbyrapidfluctuationsofpressure;

f)Centrifugalloads;

g)Impactreactionforce,reactionforcecausedbyfluidimpact,etc.;

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QB/T2551—2021

h)Forceswhentransportedorhoisted.

7.2Designprovisionsforthepressuretest

7.2.1Thepressuretestofthedryershouldbecarriedoutbythemethodofthehydrostatictest.

7.2.2Thehydrostatictestpressureshalldoublethedesignpressure.

7.3Calculationsforthecylinderdesign

7.3.1Outsidediameterseriesofthecylindershell

Thecylinderoutsidediametershouldbeselectedbyseries,seeAnnexA.

7.3.2Requiredthicknessofthecylindershell

TherequiredthicknessofthecylindershelliscalculatedaccordingtoFormula(1).

…………………

7.3.3Circumferentialequivalenttensilestressofthecylindershell

ThecircumferentialequivalenttensilestressofthecylindershelliscalculatedaccordingtoFormula(2).

…………………

Thecalculatedvalueshallmeetσ≤[σ].

7.3.4Designthicknessofthecylindershell

ThedesignthicknessofthecylindershelliscalculatedaccordingtoFormula(3).

δd=δc+C…………………（3）

TherequiredthicknessandthedesignthicknessofdifferentdiametercylindershellscanbecalculatedaccordingtotheFormula(1)andFormula(3).

7.3.5Additionalthicknessofthecylindershell

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QB/T2551—2021

Thechieffactorstobeconsideredintermsoftheadditionalthicknessofthecylindershellarethecorrosionandwearallowanceofthecylindershellaswellasitsmanufacturingfactors,suchasthefillingdepthrequiredtoensuretheplugstability.Itshallnotbelessthan4mm.Ifthedryerisdesignedtohaveanexpectedservicelifeofmorethan10years,thecorrosionallowanceshallincreaseby1mmwitheachadditionalperiodof10yearsofexpectedservicelife.Thewearallowanceneededshallbedecidedbythemanufacturerandthepurchaser.

7.3.6Minimumrequiredfabricationthickness

Theminimumrequiredfabricationthicknessshallbenotlessthanthedesignthickness.Theminimumrequiredfabricationthicknessofthein-servicedryeraftergrindingshallmeetthoseasspecifiedinthedesignthicknessrequiredfortheexpectedservicelifeaccordingtoFormula(3)and7.3.5.

7.4Geometricalparametersofthediscontinuousstructureofthecylindershell

7.4.1Accordingtotheprocessrequirementsofpapermakinganddryermanufacture,three

discontinuousstructuresofthecylindershellareavailable(seeFigure2).

a)Theconenecksectioncircularstructureb)Therightanglecircularstructurec)Thecirculartangential

structure

Figure2—Shapesofvariousdiscontinuousstructures

7.4.2Therequirementsfortheconenecktransitionstructure:

a)Theangleαbetweentheconeneckandcylindershellshallbewithin8°to12°;

b)Theconenecklengthlshallnotbelessthan80mm;

c)Theconeneckshallbeblendedsmoothlywiththecylindershellandtheflange.

7.4.3Therequirementsforthearctransitionstructurearethatthearcradiusrshallnot

belessthanD0/60and30mm,andshallbeblendedsmoothlywiththecylindershellandtheflange.

7.4.4Theroughnessoftheinnersurfaceofthecylinderflangeandthesurfaceinthetransition

zoneofthecylindershallnotbelessthanRa12.5.

7.5Endcover

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QB/T2551—2021

7.5.1Theendcovermaybestructuredinaconcavestyle(seeFigure3)oraconvexstyle(see

Figure4).However,fordryerswithalongerwidth,thestructureoftheassembledendcovershouldbeadopted(seeFigure5).

Figure3—Thedryerwiththeconcaveendcoverstructure

Figure4—Thedryerwiththeconvexendcoverstructure

Figure5—Thedryerwiththeassembledendcoverstructure

7.5.2Thecastingcorneroftheendcovershallberoundedsmoothly.

7.5.3Thethicknessoftheendcoverpressuresectionshallnotbelessthanflangesection

thickness.Forcastirondryerswithanoperatingpressurenotgreaterthan0.5MPa,thethicknessoftheendcoverflangeshallnotbelessthanthevalueasspecifiedinTableB.1.Forcastirondryerswithanoperatingpressuregreaterthan0.5MPaandnotgreaterthan0.8MPa,thethicknessoftheendcoverflangeshallnotbelessthanthevalueasspecifiedinTableB.2.

7.5.4Fordryerswithanoutsidediametergreaterthan3000mmorwithanoutsidediameter

greaterthan2000mmandadesignpressuregreaterthan0.5MPa,thecentershaftandendcoverconnectionstructureshallbeused,seeFigure6.

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QB/T2551—2021

Figure6—Thecentershaftandendcoverconnectionstructureatbothends

7.6Manholeandhandhole

7.6.1Fordryers'outsidediameternotgreaterthan1250mm,oneoftheendcoversshallbe

providedwithahandhole.Fordryers'outsidediameternotlessthan1500mm,oneoftheendcoversshallbeprovidedwithamanhole.Fordryers'outsidediametergreaterthan3800mm,twoendcoversmaybeprovidedwithamanholeeachwiththecenterlinebetweenthetwomanholesatanangleof180°fromeachother.

7.6.2Themanholeoftheendcovershallbeelliptical,withtheminoraxisintheradial

directionoftheendcover.Themanholeshallbelocatedasfarawayaspossiblefromtherabbetoftheendcoverflange.

7.6.3Theopeningoftheendcovershallbeintegrallyreinforcedbyaflange.Themassofthereinforcementshallnotbelessthanthemassoftheweakening.

7.7Cylinderflange

7.7.1ThethicknessofthecylinderflangeischeckedaccordingtoFormula(4).

…………………

7.7.2Inthedesignofthethicknessofthecylinderflange,thedimensionsoftheconnection

betweenthecylinderflangeandtheboltsshallalsobetakenconsideration.

7.8Checkingofendcoverbolts

ThematerialsandallowablestressvaluesoftheboltsusedforthedryerseeTable3.ThetensilestressofeachboltiscalculatedaccordingtoFormula(5).

……………

Thecalculatedvalueshallmeetσ≤[σ1].

13

QB/T2551—2021Thediameter,materialsandnumbersoftheconnectionboltsontheendcoverseeAnnexC.

7.9Checkingofdryerjournals

ThebendingstressofeachsectionofthejournalischeckedaccordingtoFormula(6).

σ=…………………（6）

Thecalculatedvalueshallmeetσ≤1.5[σ].

7.10Finiteelementanalysis

7.10.1Whenthepressurecomponentscannotbecalculatedregularly,thefiniteelementanalysis

ortypetestsisallowedforcalculationandverification.Theanalyticalvalueoftheprimarymembranestressthusobtainedbythefiniteelementanalysisshallnotbegreaterthantheallowablestressofthematerials.

7.10.2Measuresshallbetakenatthestructuraldiscontinuityofthedryertoreducethepeaklocalstress,whichshallnotbegreaterthan3timesoftheallowabletensilestress.Ifthelocalstressexceeds2timesoftheallowablestress,anoutwardextensionofwithin30mmisrequired.Thesurfacenon-destructiveinspectionshallbecarriedoutaccordingtotheNB/T47013.4—2015ortheNB/T47013.5—2015beforethehydrostatictestandClassIisthequalifiedlevel,whichshallbeindicatedonthedesigndrawings.

7.11Dryersurfacehardness

7.11.1Thedryersurfacehardnessshallbeindicatedonthedrawings.

7.11.2Aftermachining,iftheoutsidediameterofthecylindershellisnotgreaterthan2000

mm,thecylindersurfacehardnessshallbeHB170～HB220.Iftheoutsidediameterofthecylindershellisgreaterthan2000mm,thedryersurfacehardnessshallnotbelessthanHB190,andnotgreaterthanHB240.Forthematerialswithspecialrequirements(suchasaddingalloycomponents)ofthecastirondryer,thedryersurfacehardnessshallnotbegreaterthanHB260.ThehardnessdifferencebetweenthetwoendsofthecylindersurfaceshallnotbegreaterthanHB24.

7.12Residualstressrelieftreatment

Thecylinderandtheendcovershallbeprovidedwithtreatmenttoeliminatethecastingresidualstress.Thetreatmentrequirementsshallbeindicatedonthedrawings.

7.13Endcoverthermalinsulation

ThethermalinsulationoftheendcovershallmeetthoseasspecifiedinGB/T4272.

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QB/T2551—2021

8Fabrication

8.1Residualstressrelieftreatmentforgreycastironparts

8.1.1Duringheattreatmenttoeliminateresidualstress,thewholecastingshallbeheated

to565℃to650℃(theinitialtemperatureofthefurnaceshallnotexceed200℃)andbekeptduringthisrangeforatleast2h.Asthethicknessofthecastingincreasesbyevery25mm,theholdingtimeshallaccordinglyincreaseby1handshallnotexceed12haltogether,however.Afterwards,thecastingiscooleddownto200℃.TheheatingorcoolingrateperunittimeshallnotexceedthecalculationresultofFormula(7).

…………………

8.1.2Whenthecastingiscooledinthemold,thecoolingrateperhourfrom565℃to250℃

shallnotexceedwhicheveristhelowervaluebetweenthecalculationresultt2ofFormula

(8)and30℃/h.

…………………

8.1.3Inadditiontothetwomeasuresmentionedabove,thecastingcouldalsobestressrelieved

throughnaturalagingwhichshalltakenotlessthan1year.

8.2Spheroidalgraphitecastironpartswithresidualstressrelieftreatment

Endcoversshallbeagingtreatedaftercasting.Forspheroidalgraphitecastironcastingendcovers,annealingtreatmentcouldbeperformedtoimprovethemechanicalproperty.

8.3Surfacedefectsandthetreatmentofthecylindershell

8.3.1Thedepthofthedefectsontheinneroroutersurfacesofthecylindershellshallnot

exceed20%ofthewallthicknessofthesectioninvolved.Incasethereexistdefectsonbothsurfacesatthesamespot,evaluationsshallbeperformedregardingthedefecttypeandtheirsafetytomakesuretheirconsequenteffectsonthestructuralbearingcapacityreducetheoverallsafetyinnoway.

8.3.2Fordefectsdetectedduringtheroughgrindingofthecylindershelloutersurface,

remediesshallbetakentoremovethoselargerthan0.8mm;forthosenotlargerthan0.8mm,remediesmaybeoptional;forthosegreaterthan8mm,evaluationstodefinethedefecttypesandtheirsafetyshallbeundertaken.Ifthedefectscanbeclearedawaycompletelyaccordingtothepluggingrequirements,thenpluggingmayapply.

15

QB/T2551—2021

8.3.3Thedefectsontheoutersurfacesofthecylindershellshallnotberepairedbywelding

andshallberepairedbypluggingwiththesamematerialandshallmeetthoseasspecifiedasfollows.

a)Thediameteroftheplugshallnotbegreaterthanthelargerof10mmor20%ofthethicknessofthesection.

b)Thecenterdistancebetweentwoadjacentrepairholesshallnotbelessthanthesumoftheirdiameters.

c)Thedepthoftheplugisnotgreaterthan20%ofthethicknessofthesection.

d)Thereshallnotbemorethan8repairholesintotalwithineachsquaremeteroftheshellsurfaceandnotmorethan8repairholeswithinanyareaof100mm×100mm.

e)Thesumtotalofthefilledholesinvolvingtheendface,shoulderareasandextendedareasofthecylindershallnotbemorethan3,seeFigure7.Theaxialsizeoftheextendedareasshallbe3timesoftheeffectivewallthicknessandnotbelessthan100mmatthesametime.

a）Theconeneckcircularstructureb)Therightanglecircularstructurec)Thecirculartangential

structure

Figure7—Thecylinderendface,cylinderfaceshoulderareasandextendedareas

8.3.4Pluggingshallnotbeappliedtotheflangetransitionconeandtheroundedareaonthe

innersurfaceofthecylindershell.Pluggingshallnotbeallowedonareaswithinadistanceof30mmfromthecenterlineofthetransitionfillet.SeeFigure8.

a)Theconeneckcircularstructureb)Therightanglecircularstructurec)Thecirculartangential

structure

Figure8—Theareaofthecylindersurfacethatshallnotbepined

8.4Surfacedefectsandthetreatmentoftheendcover

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QB/T2551—2021

8.4.1Defectsontheinnerandoutersurfaceoftheendcovershallmeetthoseasspecified

in8.3.1.

8.4.2Ontheinnerandoutersurfacesoftheendcover,nomorethan3defectsofthesize

of8mmorsmallerareallowedintheannularareas100mmtowardsand100mmawayfrom,inaradialdirection,thecirclecentersformedbytheflangebolts.Ontheremainingparts,nomorethan8defectsofsuchsizesareallowedintermsofeachsquaremeter.Incaseanydefectislargerthan8mm,evaluationsshallbecarriedoutonthedefecttypeanditssafety.

8.5Balance

8.5.1Thestaticbalanceshallbecheckedforadryerwithanoutsidediameternotlongerthan

2000mmandthemachinespeednotmorethan300m/minandforadryerwithanoutsidediameterlongerthan2000mmandtherotatespeednotmorethan100r/min,wheretheresidualimbalanceshallnotexceedthedeadwei