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.