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ShutdownvalveFromWikipedia,thefreeencyclopedia

Ashutdownvalve(alsoreferredtoasSDVorEmergencyshutdownvalve,ESV,ESD,orESDV)isanactuatedvalvedesignedtostoptheflowofahazardousfluidorexternalhydrocarbons(gases)uponthedetectionofadangerousevent.Thisprovidesprotectionagainstpossibleharmtopeople,equipmentortheenvironment.ShutdownvalvesformpartofaSafetyinstrumentedsystem.TheprocessofprovidingautomatedsafetyprotectionuponthedetectionofahazardouseventiscalledFunctionalSafety

Shutdownvalvesareprimarilyassociatedwiththepetroleumindustryalthoughotherindustriesmayalsorequirethistypeofprotectionsystem.ESDvalvesarerequiredbylawonanyequipmentplacedonanoffshoredrillingrigtopreventcatastrophiceventsliketheBPHorizonexplosionintheGulfofMexicoin2010.

Contents

1Typesofvalve2Typesofactuation3Measuringperformance4Seealso

Typesofvalve

Forfluids,metalseatedballvalvesareusedasshutdownvalves(SDV's).Useofmetalseatedballvalvesleadstooveralllowercostswhentakingintoaccountlostproductionandinventory,andvalverepaircostsresultingfromtheuseofsoftseatedballvalveswhichhavealowerinitialcost.

Straightthroughflowvalves,suchasrotaryshaftballvalves,aretypicallyhighrecoveryvalves.Highrecoveryvalvesarevalvesthatloselittleenergyduetolittleflowturbulence.Flowpathsarestraightthrough.Rotarycontrolvalves,butterflyvalveandballvalvesaregoodexamples.

Forairintakeshutdown,twodistincttypesarecommonlyutilized,i.e.butterflyvalvesandswinggateorguillotinevalves.Becausedieselenginesignitefuelusingcompressioninsteadofanelectronicignition,shuttingoffthefuelsourcetoadieselenginewillnotnecessarilystoptheenginefromrunning.Whenanexternalhydrocarbon,suchasmethanegas,ispresentintheatmosphere,itcanbesuckedintoadieselenginecausingoverspeedoroverrevving,potentiallyleadingtoacatastrophicfailureandexplosion.Whenactuated,ESDvalvesstoptheflowofairandpreventthesefailures.

Typesofactuation

AsshutdownvalvesformpartofaSISitisnecessarytooperatethevalvebymeansofanactuator.Theseactuatorsarenormallyfailsafefluidpowertype.Typicalexamplesoftheseare:

PneumaticcylinderHydrauliccylinder

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Pneumaticallyactuatedshutdownvalve

Electrohydraulicactuator

Inadditiontothefluidtype,actuatorsalsovaryinthemannerinwhichtheenergyisstoredtooperatethevalveondemandasfollows:

singleactingcylinderOrspringreturnwheretheenergyisstoredbymeansofacompressedspringdoubleactingcylinderEnergyisstoredusingavolumeofcompressedfluid

Thetypeofactuationrequireddependsupontheapplication,sitefacilitiesandalsothephysicalspaceavailablealthoughthemajorityofactuatorsusedforshutdownvalvesareofthespringreturntypeduetothefailsafenatureofspringreturnsystems

Measuringperformance

Forshutdownvalvesusedinsafetyinstrumentedsystemsitisessentialtoknowthatthevalveiscapableofprovidingtherequiredlevelofsafetyperformanceandthatthevalvewilloperateondemand.TherequiredlevelofperformanceisdicatedbytheSafetyIntegrityLevel(SIL).Inordertoadheretothislevelofperformanceitisnecessarytotestthevalve.Thereare2typesoftestingmethodsavailablebeing

ProoftestAmanualtestthatallowstheoperatortodeterminewhetherthevalveisinthe"asgoodasnew"conditionbytestingforallpossiblefailuremodesandrequiresaplantshutdown

DiagnosticTestAnautomatedonlinetestthatwilldetectapercentageofthepossiblefailuremodesoftheshudownvalve.Anexampleofthisforashutdownvalvewouldbeapartialstroketest.Anexampleofamechanicalpartialstroketestdevicecanbefoundhere(http://www.cam.com/Forms/Product.aspx?prodID=3da2f6d9dfad408a9863b2cdf266f49c).

Seealso

ActuatorPipelinetransportPipingUnitoperationValves

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Categories: Valves Piping Safetyengineering

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