of 10
Piping (Nozzle) Loads.Applying the API 610 standards
To A Centrifugal Pumpset{Pumpset = Pump + Baseplate}
Presentedby: DougIngham,SulzerPumps(US)Inc.
5.3.3a The pressure casing shall be designed to operate without leakage or internal contact between rotating and stationary components while subject simultaneously to the MAWP and the worst-case combination of twice (2x) the allowable nozzle loads of Table 4 applied through each nozzle.
NOTE: The twice-nozzle-load requirement is a pressure-casing design criterion. Other factors such as casing support or baseplate stiffness affect allowable nozzle loads.
6.3.5 The pump and its baseplate shall be constructed with sufficient structural stiffness to limit displacement of the pump shaft at the drive end to meet values per API Table 12 when subjected to (1x) API 610 Table 4 nozzle moments.
5.5.1 Three factors to consider:1. Pump casing stress. Total to be within ASME allowable. (5.3.4)2. Pump casing distortion. (5.3.3)3. Misalignment of pump and driver shafts. (6.3.5)
5.5.5 Annex F gives methods of qualifying nozzle loads in excess of those in Table 4. Annex F is used by the piping designer - not the pump designer.It also goes on to say that user must be aware that the use of Annex F methods can result in 50% greater misalignment than would occur using the loads of Table 4
API610{10thEdition}Requirements
6.3.6 If specified, the vendor shall test to demonstrate that the pump and its baseplate assembly, anchored at foundation bolt hole locations, are in compliance with 6.3.5. The pump casing shall be subjected to moments MYCand MZC applied to either nozzle, but not both, such that the corresponding shaft displacements can be measured and recorded. MYC and MZC shall not be applied simultaneously to either nozzle. The shaft displacement measurements shall be absolute (not relative to the baseplate).
API610{10thEdition}Requirements
DY
DZ0.003" max
0.007" max
NozzleLoadTestatPumpVendor'sFacilityMomentsMYC&MZCareappliedviaahydraulicallyoperatedrotaryactuator.Shaftendmovementsaremeasuredviadialindicators.AppliedmomenttosuctionnozzleforMy
MeasuredeflectioncausedbyMy
13008706Discharge
2800180010Suction
MZ(ftlb)MY(ftlb)Size(in)Nozzle
Calculated Moment Loads (ft- lbs)MYc = MY (discharge) + MY (suction) = 870 + 1800 = 2670MZc = MZ (discharge) + MZ (suction) = 1300 + 2800 = 4100
0.00050.0008Dialindicator (in)DYDZShaftdisplacement41662708Momentapplied (ftlb)MZcMYcLoading
N/ADY=0.003MZcN/ADZ=0.007MYc
UngroutedtypebaseBaseintendedforgroutMaximumallowablepumpshaftdisplacements(in)
LoadingCondition
Question:Whenapurchaserspecifiesthatthepumpallowablenozzleloadsshallbetwice(2x)Table4values Whatdoesthisactuallymean?
Purchaser'sRequirementsTo reduce the complexity / cost of the supply / return piping design layout, purchasers request that pump suppliers modify the pumpset to accommodate higher nozzle loads.
Option1):A2xmultipliermustbeappliedtoallparagraphsinAPI610thatpertaintoTable4nozzleloads:5.3.3aThepressurecasingshallbedesignedtooperatewithoutleakageorinternalcontact betweenrotatingandstationarycomponentswhilesubjectsimultaneously totheMAWP andtheworstcasecombinationoffourtimes (4x)theallowablenozzleloadsofTable4appliedthrougheachnozzle.6.3.5 Thepumpanditsbaseplateshallbeconstructedwithsufficient structuralstiffnesstolimitdisplacementofthepumpshaftatthedriveend tomeetvaluesperAPITable12whensubjectedto(2x)API610Table4nozzlemoments.F.1.2a)TheindividualcomponentforcesandmomentsactingoneachpumpnozzleflangeshallnotexceedtherangespecifiedinTable4byafactormorethan4.Option2):A2xmultiplierisonlyappliedtotheshaftdeflectioncriteria:6.3.5 Thepumpanditsbaseplateshallbeconstructedwithsufficient structuralstiffnesstolimitdisplacementofthepumpshaftatthedriveend tomeetvaluesperAPITable12whensubjectedto(2x)API610Table4nozzlemoments.
Whenpurchasersmandatetheacceptanceofnozzleloadsinexcess ofAPI610Table4thepumpvendormaybeabletomeettheserequirements,however,thisprovisionwillrequireadditionalanalysis,whichmayincludea3DcasingFiniteElementAnalysis(FEA)atadditionalcostandincreasedleadtime. Thepumppressurecasingmayneedtobemodified.ASMEflangeratingsmayneedtobeincreased.{Useclass600#on apumpwithaMAWPof740psig}.Pumppedestalandbaseplatesubframedesignwillneedtobemodified.Analyticalstudiesmayfindthatitisnotpossibletomeetacceptancecriteriaforreliableoperationunderthespecifiedhighnozzleloadconditions.
ChallengesForPumpVendor
Non-Standard Pump Nozzle Loads = Not a simple task:
Pump Support [Baseplate] Stiffness Evaluation Thepumpisconsideredstifffortheanalysis.
Unitloadsareindividuallyappliedtothe"stiffnesscenter"of thepump Thestiffnesscenteriswherethenozzlesmeetthepumpcasing;thenozzlescanbeconsideredtooriginatefromthispoint
andconnecttothepipingforthepipinganalysis. Locationofnozzlesfromthestiffnesscenter(APIcoordinatesystemwasused). Thebaseplatewasanalyzedwithandwithoutgrout.
Withgrout,thebaseplatewasheldattheanchorboltlocationsandattheundersideofthebaseplatesimulatingbondedepoxygrout
Withoutgrout,thebaseplatewasheldattheanchorboltsonly.
FEAmodelofbaseplate&pumpwithAPIcoordinatesystem
Load,Displacement,andStiffnessvaluesforBaseplate&Pump
PumpSupport[Baseplate]StiffnessEvaluationResults
Providecustomer/pipingdesignerwiththeinformationbelowandrequestrecalculationofappliednozzleloads,consideringthenonrigidpumpsupportstiffness:
3-Dimensional FEA of Pump Case - Example Whenconsideringacceptabilityofnozzleloadsinexcessof2xAPI610
values,theaforementionedeffectsneedtobeinvestigated. Afiniteelementmodelofa20x24x32HSBcasingwasusedto
investigatetheeffectofhighnozzleloadsontocasingstresses anddeflections.
3-Dimensional FEA of Pump Case - Example
Thefiniteelementmodelwassubjectedto2,4,6and8timesAPI610Table4nozzleloads. Foreachloadingconditionthemodelwascheckedfor:
Casingstresses(absoluteandchange) Casedeformationaroundrotorseals. Casetightness/potentialforleakage Pumpholddownboltstresses
3-Dimensional FEA of Pump Case - Example
Severalareasofconcernwerechosenforobservationateachnozzleloadingcondition.Theselocationstypicallyexhibitedhigherconcentrationofstressthanitssurroundingareas.Linearizedstresspathswereinsertedattheselocations.
Stressdistributionovertheentirebodywasobservedforabrupt changesbetweennozzleloadings.
3-Dimensional FEA of Pump Case - Stress Results
36,000Yield70,000TensileA216Gr.WCBProperties(psi)CaseMaterial
Conclusion:Nozzleloadingsdonotsignificantlyinfluencestressesinthelowercasehalf.
3-Dimensional FEA of Pump Case - Stress Results
Upper Case #1
Upper Case #2
NOZZLE LOADINGS Zero Loading 2X API 4X API 6X API 8X API
Internal Pressure psi % change psi % change psi % change psi % changeOnly (1480 psi)
UPPER CASE HALFSTRESSES
[Membrane + Bending]
Pump Foot 32,421 32,883 1.43 32,762 1.05 31,794 -1.93 32,523 0.31LowerCase#1 19,190 18,575 -3.20 19,115 -0.39 19,087 -0.54 18,723 -2.43UpperCase#2UpperCase#1
Conclusion:Nozzleloadingsdonotsignificantlyinfluencestressesintheuppercasehalf.
36,000Yield70,000TensileA216Gr.WCBProperties(psi)CaseMaterial
3-Dimensional FEA of Pump Case - Deformation Evaluation
3-Dimensional FEA of Pump Case - Deformation Evaluation
Conclusion:Stationarywearringdoesnotcomeintocontactwith impellereyeringunderanytestedloadingcondition.
3-Dimensional FEA of Pump Case - Gasket Tightness Evaluation
Gasketcontactpressuremustbemaintainedwhenthecaseissubjecteddistortionduetointernalpressureandnozzleloads.
Pumpvendorshavespecificcriteriathatneedstobechecked.
3-Dimensional FEA of Pump Case - Gasket Tightness Evaluation
Conclusion:1.)Gasketpressuresaroundthepartingflangeboltholesandmechanicalsealboreare>=2xmaximum
internalpressure.(Internalpressureis1480psi).2.)Noleakageisexpectedfor2x,4x,6xand8xAPI610nozzleloads.Relativechangebetweenload
casesisinsignificant.
3-Dimensional FEA of Pump Case - Hold-Down Bolt Evaluation
58,000Yield90,000TensileSAEGr.5Properties(psi)
BoltMaterial
Conclusion:Holddownboltsdonotexperienceanysignificantchangeinstress.