Vacuum Sealing Technology

1LeaderinVacuumValvesVacuumSealingTechnologyKurtSondereggerProductGroupManagerAllMetallValveGroupCERNAcceleratorSchool,PlatjaD’Aro,SpainMay16–24,20062Directory
Sealingtechniquesinvacuumsystems
Differencestaticanddynamic
Staticanddynamicsealingconfiguration
Typicaldetachablesealingconfigurations
Staticsealing
Dynamicsealing
Situationonadetachablesealingjoint
outgassing/outgassingrate
Desorption,Leak(vacuum)
Permeation
Vacuumlevels
Sealingdetails–elastomerseals
Sealingsurface
VentingofO-ringgrooves
O-ringgrooveshape
Vulcanizedseals
StressplotofO-rings
Stiffnessimpactofgrooveshape
Stressplotofvulcanizedseal3Directory
CompressionofO-rings
O-ringtolerances
Effectoftolerances
StretchingandcompressingofO-rings
O-ringquality
Stiffnessofoverallsystem
ElastomerBasics
Relaxation/Temperature
Compressionset
Sealfailures–vacuumseals
Radiationresistance
Sealingdetails-metalseals
Whyallmetalseals?
Whattypeofseals?
Isthereanystandard?
“Softonhard”sealing
“Hardonhard”sealing
Advantagesof“hardonhard”against“softonhard”sealing
Keyforareliablemealseal
Comments4Sealingtechniquesinvacuumsystems
Nondetachableconnections:
Welding
Brazing
GlassandCeramicfeedthrough
Gluing–epoxyresin(pressure10-7mbar)
Detachableconnections:
Flangetoflangeconnectionswithsealingmaterial
Gatetoflangeconnectionswithsealingmaterial
Feedthrough(elastomersealed)
Feedthrough(magnetic)
Nondetachableconnection:
Feedthrough(bellowslinearorrotarymotion)STATICDYNAMIC5-Leaktight-Lowoutgassing-Lowpermeation-Bakeable-Reliable-MayberadiationresistantDifferencestaticanddynamicDynamicsealingconfigurationStaticsealingconfiguration-Repeatedreliablesealingor-TransferofmovementfromatmospheretovacuumRequirements:6
AlltypesofsealingconfigurationcanbefoundonavalvestaticdynamicStaticanddynamicsealingconfigurationdynamic7Typicaldetachablesealingconfigurations-X-timesusable-chemicallyresistant-rarelyused-Outgassingapprox.…1x10-8-Needstobe“trapped”-X-timesusable-Veryexpensive-Onlyforspecialpurposes(UHV,chemical)-Outgassingapprox.…1x10-9(stronglydependingontreatment)-Usegroovecut-inmeasurelist-X-timesusable-Expensive-Fordemandingpurposes(UHV)-Outgassingapprox.…1x10-8(stronglydependingontreatment)-Usegroovecut-inmeasurelist-X-timesusable-Mostusedsealinfineandhighvacuumtechnology-Relativelowpriced-Outgassingapprox.…1x10-6(stronglydependingontreatment)-Usegroovecut-inmeasurelistRemarksProfile260°C200-250°C150°C90°CMax.workingtemperaturePolytetrafluoroethylenePTFE(TEFLON®)FluoroelastomerFKM(VITON®)PerfluoroelastomerFFKM(KALREZ®CHEMRAZ®)SyntheticrubberNBRCR(NEOPREN)MaterialStaticsealingconfigurationsintheVacuumTechnology8-Onetimeusage-Usablewithstainlessstealsmallflanges(specialtensionrings)-LimitedUHVsuitable-Multipleusage-Suitableforsmallflange–system(ordinarytensionrings)-Minimallyoutgassing-Onetimeusage-Soft-Rarelyused-Smalloutgassing-Onetimeusage-SealingsurfaceRa0,4-Casingalsoinothermaterials-ApplicationUHVRemarksProfile260°C60°C100°C300°CMax.workingtemperatureALUMINIUMINDIUM(orpuretin)STAINLESSSTEELINDIUMALUMINIUMCoveringHélicoflex(Delta)MaterialStaticsealingconfigurationsintheVacuumTechnologyTypicaldetachablesealingconfigurations9-Multipleusage-SSweldfittingsoreventhetubeitself,planesurface-ApplicationUHV-100°C+500°CSS–SSRHP–FlatsealFlowmeca™-Multipleusage-SS-flanges,flatsurfaceN4(Ra=0.2μm)-ApplicationUHV-Onetimeusage-SS-flanges,flatsurfaceN4(Ra=0.2μm)-ApplicationUHV-Uptoapprox.4timesusable(annealeachtime)-InsteadofCFatlargerØ-Highsealingforce-Corrosionresistant-Littleoutgassing-ApplicationUHV-Onetimeusage-CF-Flange-System-Easytoassemble-Verylittleoutgassing-ApplicationUHVRemarksProfile450°C300°C450°C400°CMax.workingtemperatureSS–silverplatededgesealGOLDCOPPERsilverplatedVATVATSEALCOPPER(onlyusableinOFHC)MaterialStaticsealingconfigurationsintheVacuumTechnologyTypicaldetachablesealingconfigurations10ForVacuumapplication90°CSyntheticrubberNBRCR(NEOPREN)ForHighVacuumandUltraHighVacuumapplication150°CFluoroelastomerFKM(VITON®)ForHighVacuumandUltraHighVacuumapplication200-250°CPerfluoroelastomerFFKM(KALREZ®,CHEMRAZ®)ForXUHVapplication450°CwithspecialprecautionsSS–CUForXUHVapplication350°CSS–SSsilverplatedVATRINGRemarksProfileMax.workingtemperatureMaterialDynamicsealingconfigurationsintheVacuumTechnologyTypicaldetachablesealingconfigurations11Situationonadetachablesealingjoint12Outgassing/Outgassingrate
Outgassing/OutgassingrateTheoutgassingrate(mbarls-1)isthesumofallgasloadscausedby:-Desorption-Diffusion-Permeation-Outgassingofvoidsandcrevices-DisintegrationofsurfacelayersAsmalloutgassingrateisessentialforefficientpumpdownandlowbasepressureandisachievedby:-Useofmaterialswithassmalldesorption,diffusionandpermeationratesaspossible-Preventingcrevicesandunventedvoids-VacuumcompatiblecleaningTheoutgassingrateofverywelldegassedsurfaces(baked)atroomtemperature:-Stainlesssteel2x10-13mbarls-1cm-2-VITON®(withoutpermeation)2x10-11mbarls-1cm-213Desorption,Leak(vacuum)
Desorption
Leak(vacuum)Thedesorptionofphysicallyorchemicallyboundgassesfromtheinteriorsurfacesofavacuumcontaineristhelaststepoft