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piperack Design Philoshipy

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  • 08/05/2015 www.sefindia.org::ViewtopicPIPERACKDESIGNGUIDELINES

    http://www.sefindia.org/forum/viewtopic.php?t=8219 1/10

    www.sefindia.orgSTRUCTURALENGINEERINGFORUMOFINDIA[SEFI]

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    PIPE RACK DESIGN GUIDELINESGotopage1,2Next

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    nestlejinSEFIMember

    Joined:16Jul2010Posts:19

    Posted:TueAug31,20109:07amPostsubject:PIPERACKDESIGNGUIDELINES

    Dearall,Givenweblinkisveryusefulltounderstandpiperackdesign

    http://www.civildesignhelp.info/pr.html

    PiperackDesignPhilosophy

    InthispageIwilltalkaboutthepiperackdesignphilosophy.Piperackisthemainarteryofanyplant.Thiscarriesthepipesandcabletrays(raceways)fromoneequipmenttoanotherequipmentwithinaprocessunit(calledISBLpiperack)orcarriesthepipeandcabletraysfromoneunittoanotherunit(calledOSBLpiperack).SometimesyouwillalsofindtheAIRCOOLEDHEATEXCHANGERSonthepiperack.

    Therearedifferenttypesofpiperack:

    ContinuousPiperacks(conventionalpiperack)systemNoncontinuousPiperackssystemModularPiperack

    Conventional/ContinuousPiperack

    ContinuousPiperacks(conventionalpiperack)system:Thisisessentiallyasystemwheremultiple2dimensional(2D)frameassemblies(commonlycalledbents),comprisedoftwoormorecolumnswithtransversebeams,aretiedtogetherinthelongitudinaldirectionutilizingbeamstruts(forsupportoftransversepipeandracewayelementsandforlongitudinalstabilityofthesystem)andverticalbracingtoforma3Dspaceframearrangement.Piperackssupportingequipmentsuchasaircooledheatexchangersmustutilizethecontinuoussystemapproach.

    Step1:Datacollectionforpiperackdesign:

    Duetothefasttracknatureassociatedwithmostoftheprojects,oftenthefinalpiping,raceway,andequipmentinformationisnotavailableatinitiationofthepiperackdesign.Therefore,asaCivil/StructuralEngineer,youshouldcoordinatewiththePipinggroup,Electrical,ControlSystems,andMechanicalgroupstoobtainasmuchpreliminaryinformationaspossible.Whenreceived,alldesigninformationshouldbedocumentedforfuturereferenceandverification.Intheinitialdesign,theEngineershouldusejudgementwhenapplyingorallowingforloadsthatarenotknown,justifyingtheminthedesignbasisunder"DesignPhilosophy"(apartofyourcalculation)

    Thefollowingshouldbereviewedfordesigninformation:

    Plotplansandequipmentlocationplans3Dmodelshowingpipinglayout,cabletraylayout,Piperackbentspacingandelevationofsupportlevels

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  • 08/05/2015 www.sefindia.org::ViewtopicPIPERACKDESIGNGUIDELINES

    http://www.sefindia.org/forum/viewtopic.php?t=8219 2/10

    inthetransversedirection,Elevationoflongitudinalbeamstrutsandlocationsofverticalbracing.andlocationofpipebridge,ifany.Pipingorthographicdrawings.Vendorprintsofequipmentlocatedontherack,e.g.,aircoolersandexchangers.Thevendorprintsshouldincludetheequipmentlayout,mountinglocationsanddetails,accessandmaintenancerequirements,andthemagnitudeanddirectionofloadsbeingtransmittedtothepiperack.Electricalandcontrolsystemsdrawingsshowingtheroutingandlocationofelectricalandinstrumentationracewaysand/orsupports.Undergrounddrawingsthatshowthelocationsofburiedpipes,concretestructuresandfoundations,ductbanks,etc.intheareaofthepiperack.Piperackconstructionmaterial(Steel,Castinsituconcrete,Precastconcrete)shallbeasperprojectdesigncriteria.

    Pleasenotethat,Unlessspecificallyexplainedintheprojectdesigncriteria,noallowanceorprovisionsshouldbemadeforfutureadditionsforpipeorracewayspaceandrelatedloading.

    Step2:Designloadsconsideration:

    Followingloadsaretobeconsideredforthepiperackdesign:

    PipingGravityload(D):Intheabsenceofdefinedpipingloadsandlocations,anassumedminimumuniformpipeloadof2.0kPashouldbeusedforpreliminarydesignofpiperacks.Thiscorrespondstoanequivalentloadof6in(150mm)linesfullofwatercoveredwith2in(50mm)thickinsulation,andspacedon12in(300mm)centers.ThisassumptionshouldbeverifiedbasedoncoordinationwiththePipingGroup,andconcentratedloadsshouldalsobeappliedforanyanticipatedlargepipes.Whentheactualloadsandlocationsbecomeknown,astheprojectdevelops,thestructuraldesignshouldbecheckedagainsttheseassumedinitialloadparametersandrevisedasrequired.Aconcentratedloadshouldthenbeaddedforpipesthatare12in(300mm)andlargerindiameter.TheconcentratedloadPshouldbe:

    P=(Wsxpxd),s=Spacingofpiperackbent,p=pipeweightconsidered(kPa),d=pipediameterW=pipeconcentratedload.

    Whereconsiderationofupliftorsystemstabilityduetowindorseismicoccurrencesisrequired,use60%ofthedesigngravityloadsasan"allpipesempty"loadcondition.

    Loadingduetohydrostatictestingoflinesshouldbeconsideredinthedesignifapplicable.Coordinatethetestingplan(s)withConstruction,Startup,and/orthePipingGroupasnecessary,inordertofullyunderstandhowsuchloadswillbeappliedtothepiperackstructure.Undermostnormalconditions,multiplelineswillnotbesimultaneouslytested.Thehydrotestloadsdonotnormallyneedtobeconsideredconcurrentlywiththeothernonpermanentloads,suchasliveload,wind,earthquake,andthermal.Typicalpracticeistopermitanoverstressof15%forthehydrotestcondition.Becauseoftheseconsiderations,thehydrotestconditionwillnotnormallygovernexceptforverylargediameterpipes.ElectricalTrayandConduits(D):Electricalandcontrolsystemsdrawingsand/ortheproject3Dmodelshouldbereviewedtodeterminetheapproximateweightandlocationofelectricaltrays,conduits,andinstrumentationcommodities.Unlesstheweightoftheloadedracewayscanbedefined,anassumedminimumuniformloadof1.0kPashouldbeusedforsingletierraceways.

    SelfweightofPiperack(D):Theweightofallstructuralmembers,includingfireproofing,shouldbeconsideredinthedesignofthepiperack.

    WeightofEquipmentonpiperack(D):Equipmentweights,includingerection,empty,operating,andtest(iftheequipmentistobehydrotestedonthepiperack),shouldbeobtainedfromthevendordrawings.Theequipmentweightshouldincludethedeadweightofallassociatedplatforms,ladders,andwalkways,asapplicable.SpecialLoads:Specialconsiderationshouldbegiventounusualloads,suchaslargevalves,expansionloops,andunusualpipingorelectricalconfigurations.

    LiveLoad(L):Liveload(L)onaccessplatformsandwalkwaysandonequipmentplatformsshouldbeconsidered,asapplicable.

    SnowLoad(S):Snowloadtobeconsideredoncabletrayandonlargediapipes.Thisloadshallbecalculatedperprojectapproveddesigncodeandprojectdesigncriteria.Generally,youneedtoconsider100%snowloadontoptierand50%onothertierofpiperacks.

    WindLoad(W):Transversewindloadonstructuralmembers,piping,electricaltrays,equipment,platforms,andladdersshouldbedeterminedinaccordancewithprojectapproveddesigncode.Longitudinalwindshouldtypicallybeappliedtostructuralframing,cabletrayverticaldrop(ifany),largediapipesverticaldrop(ifany)andequipmentonly.Theeffectsoflongitudinalwindonpipingandtraysrunningparalleltothewinddirectionshouldbeneglected.

  • 08/05/2015 www.sefindia.org::ViewtopicPIPERACKDESIGNGUIDELINES

    http://www.sefindia.org/forum/viewtopic.php?t=8219 3/10

    EarthquakeLoads(E):Earthquakeloadsinthevertical,transverse,andlongitudinaldirectionsshouldbedeterminedinaccordancewiththeprojectdesigncriteria.Vertical,transverse,andlongitudinalseismicforcesgeneratedbythepipes,raceways,supportedequipment,andthepiperackstructureshouldbeconsideredandshouldbebasedontheiroperatingweights.Pipesmustbeevaluatedforseismicloadsunderbothfullandemptyconditionsandthencombinedwiththecorrespondinggravityloads.

    FrictionLoading(Tf):Frictionforcescausedbyhotlinesslidingacrossthepipesupportduringstartupandshutdownareassumedtobepartiallyresistedthroughfrictionbynearbycoldlines.Therefore,inordertoprovideforanominalunbalanceoffrictionforcesactingonapipesupport,aresultantlongitudinalfrictionforceequalto7.5%ofthetotalpipeweightor30%ofanyoneormorelinesknowntoactsimultaneouslyinthesamedirection,whicheverislarger,isassumedforpiperackdesign.Frictionbetweenpipingandsupportingsteelshouldnotbereliedupontoresistwindorseismicloads.

    AnchorandGuideLoads(Ta):PiperacksshouldbecheckedforanchorandguideloadsasdeterminedbythePipeStressGroup.Itmaybenecessarytousehorizontalbracingiflargeanchorforcesareencountered.Forconventionalpiperacksystems,itisnormallypreferredtoeitherhavetheanchorsstaggeredalongthepiperacksothateachsupporthasonlyoneortwoanchors,ortoanchormostpipesononebracedsupport.Forinitialdesign,whenanchorandguideloadsarenotknown,usealongitudinalanchorforceof5.0kNactingatmidspanofeachbenttransversebeam(referprojectdesigncriteria).GuideloadsareusuallysmallandmaybeignoreduntiltheyaredefinedbythePipeStressEngineer.Fornoncontinuouspiperacksystems,pipingmaybetransverselyguidedoranchoredatbothcantileverframesandanchorbays.Longitudinalanchorsmaybelocatedonlyatanchorbays.

    Pleasenotethat,allfrictionforcesandanchorforceswithlessmagnitude,(say~5.0kN),appliedtothetopflangeofthebeam,maybeconsideredasresistedbythetotalbeamsection.Whenanchorloadshavelargemagnitudeandareappliedtothetopflangeofthebeam,theeffectoftorsionmustbeaddressed.Ifthebeamsectionisinadequatetotakecareofthistorsionalforce,alternativestobeconsidered,suchasprovidehorizontalbracingsattheloadlocations.

    Step3:LoadCombinationsandallowabledeflectionofpiperack:

    Youneedtocreatetheloadcombinationsperyourprojectdesigncriteria.However,Ihavereferedheresomeloadcombinations.

    Pleasenotethefollowing:

    Earthquakeloadisafactoredload.Forloadcombinationsthatincludewindorearthquakeloads,useonlythenonfrictionportion(anchorandguideportion)ofthethermalloads,i.e.,frictionloadsarenotcombinedwithwindorseismicloads.Frictionloadsareconsideredtobeselfrelievingduringwindandearthquakeandshouldonlybecombinedwithanchorandguideloadswhenwindorearthquakeloadsa

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