12/10/2014 OnOffValveBypassIndustrialProfessionalsCheresources.comCommunity

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OnOffValveBypassStartedbyfarid.k,Jul22201407:09PM

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12/10/2014 OnOffValveBypassIndustrialProfessionalsCheresources.comCommunity

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farid.k

HyeNormallycontrolvalvethatregulateflowwillhavecommonisolationvalve,drainandbypass.IsitnecessarytoputthatitemalsoforONOFFvalvewhichistriggeredduringemergencycase?Idontthinksosinceformeitisconsideredassafetyitemthatshallbeserviceduringturnaroundonly.Havingbypassconsideredbypassthesafety.Appreciatetoadviseme.

Posted22July201407:09PM

sukanta87

Duringstartup,theshutdownvalveinclosedposition.Theupstreamofshutdownvalvewillbepressurizedathighpressure(i.e100barg)whilsttheshutdownvalvemaystillkeptat23barg.Highdifferentialpressureacrosstheshutdownwillresultshightorqueagainsttheactuator.http://webwormcpt.bl...sdvbypass.html(http://webwormcpt.blogspot.com/2007/12/commonrequirementsofsdvbypass.html)Inemergencyifshutdownvalveisactuated,highDPwillcreate(ifthereisnobypassorbypassisclosed)whichisbadfortheSDV.Moreover,inmanycasestheSDVbypassesaresmallerthantheusualbypasssize.EventheSDVbypassmayequippedwithRO(restrictionorifice),itdepends.Aftersometimesofoperation,SDVbypasscanbeclosedasyourneeds.

Posted22July201411:17PM

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fallah

farid.k,Itdependstotheon/offvalvefunction.ForanESDVconsideringbypassisn'tnormallyauthorizedduetosafetyissue,butforSDVitcouldbeconsidered...

Posted23July201412:46AM

farid.k

fallah,on23Jul201408:56AM,said:

farid.k,

Posted23July201402:20AM

12/10/2014 OnOffValveBypassIndustrialProfessionalsCheresources.comCommunity

http://www.cheresources.com/invision/topic/21249onoffvalvebypass/# 3/5

Itdependstotheon/offvalvefunction.ForanESDVconsideringbypassisn'tnormallyauthorizedduetosafetyissue,butforSDVitcouldbeconsidered.

whatisthedifferentbetweenESDVandSDV?actthenewvalveistoprotectboiler.forme,itstillconsiderasemergencyshutdownvalve.appreciatetoadvise.

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fallah

farid.k,Thereisnodifferencebetweentheminconstructionandaccessoriesstandpoints...SDVsarethevalveswillbeactuatedtobeclosedduringpartialortotalplantshutdownofsystembeingprotectedbythem.ESDVsarethevalveswillbeactuatedtobeclosedduringemergencyconditionwhentriggeredbyESDlevelsignalandarenormallylocatedatINCOMING (#)/outgoinglinesofaplantoreachfirezoneinsideaplant.AscanbeseenanESDVismoreimportantthanaSDVinsafetystandpoint....

Editedbyfallah,23July201402:42AM.

Posted23July201402:41AM

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farid.k

fallah,on23Jul201410:51AM,said:

farid.k,Thereisnodifferencebetweentheminconstructionandaccessoriesstandpoints...SDVsarethevalveswillbeactuatedtobeclosedduringpartialortotalplantshutdownofsystembeingprotectedbythem.ESDVsarethevalveswillbeactuatedtobeclosedduringemergencyconditionwhentriggeredbyESDlevelsignalandarenormally

locatedatINCOMING (#)/outgoinglinesofaplantoreachfirezoneinsideaplant.

Posted23July201403:21AM

12/10/2014 OnOffValveBypassIndustrialProfessionalsCheresources.comCommunity

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AscanbeseenanESDVismoreimportantthanaSDVinsafetystandpoint....

myconcernis,ifiputbypass,theyhavechancetobypassitandnomoreprotectiontotheboilerduringbypass.ialsonopointwhyshouldiputbypass.unlesscontrolvalvethatregulateflowthatmightneedtoservicetimetotime

fallah

farid.k,Normallybypassistobeconsideredforacontrolvalveduetooneofthefollowingthreereasons:StartupbypassMaintenancebypassControlbypassIfyouhavetouseoneoftheabovebypassandareworryaboutanysafetyissue,youcanputitinlockedclosedpositioninnormaloperationcondition...

Posted23July201403:30AM

sanchit_11

DearFarid,Ireallyappreciateyourconcernwithprovisionsofbypassacrossshutdownvalve(ON/OFF).PleasefindpointwiseANALYSIS (#)forwhereyoushouldinstalledbypassacrossshutdownvalves.

Itistobenotedthatanyshutdownvalveatwhateverlineitisinstalleddoesnothavemuchpressuredifferenceacrossitwhenitisinopenconditionbutitwillexperienceappreciablepressuredifferenceonlywhenvalvewillbeinclosedposition.Actuatoronshutdownvalvewillbesizedonbasisoftorquerequiredtoovercomethispressuredifferencetoopenthevalveagainwhenshutdownreasonistakencareof.Ifpressuredifferenceacrossshutdownvalveismorethansizeofactuatorwillbelargeandviceversa.Butsometimewithlargesizevalvewhichishavinghighpressuredifferenceacrosstheminclosedconditionactuatorsizerequiredbecomeverylarge.Thusinordertoavoidusageofverylargesizeactuatoraverysmallsizebypassnormally2"or3"isinstalledacrossvalve.Thisbypassequalizesupstreamanddownstreampressureandreducedifferentialpressureacrossvalveandhelpinreducingsizeofactuator.

So,fromabovewecanconcludethatbypassofshutdownvalveisnotrequiredunlessreductioninsizeofactuatorisrequired.SometimeInstallationoflargesizeactuatorsarenotpossibleduetospacerestrictionasatoffshoreplatformswherespaceisthemostCOSTLY (#)item.Ihopethisansweryourquery.regardsSanchit

Posted24July201412:01AM

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sukanta87

Thankssanchitfortheclearviewwithelaboration.

Posted24July201401:43AM

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