ModelingandSimulationModelingandSimulationi l i S di l i S dTransientAnalysisCaseStudyTransientAnalysisCaseStudy

of a Liquids Gathering Systemof a Liquids Gathering SystemofaLiquidsGatheringSystemofaLiquidsGatheringSystem

Mr.AugustoGarciaMr.AugustoGarciaMr.Mr.ThomasMoore

SouthwestResearchInstituteSouthwestResearchInstitute

Description&OutlineDescription&Outline

Numerous failures of a flexible composite pipeline

Liquids gathering system

Transient hydraulic model to evaluate a 4-inch flexibleit i li d 8 i h t l i li

IntroductionIntroduction

composite pipeline and an 8-inch steel pipeline

DataCollectionDataCollection ComputationalModelingComputationalModeling ResultsResults AnalysisAnalysisyy Summary&Conclusions/QuestionsSummary&Conclusions/Questions

GatheringSystemMapGatheringSystemMap

CDP-01, -02, -03, and Stabilizer plantStabilizer plant

CDPs identical in configuration with 2 triplex pumps (PDP)

~12.5 Miles from CDP-01 to stabilizer plantp

Stabilizer plant PCV holds 500 psig back pressure

Check valve half way up hill

~500 ft from CDP-01 to top500 ft from CDP 01 to top of hill

ModelingProcessModelingProcess

Verify data is consistentVerify data is consistent Collect additional data and makeCollect additional data and make

Data Collection Collect additional data and make Collect additional data and make

corrections as neededcorrections as needed

Functional & process block diagrams

Collection

Document assumptionsDocument assumptions Verify data is consistent and appropriateVerify data is consistent and appropriateblock diagrams

Computational model d l t

Verify data is consistent and appropriate Verify data is consistent and appropriate for modeling softwarefor modeling software

Ensure predictive measures are consistent Ensure predictive measures are consistent and appropriate for intended analysisand appropriate for intended analysis

development

Computational model

Check that the units are correctCheck that the units are correct Use known operating parameters from Use known operating parameters from

data collection phase if possibledata collection phase if possiblevalidation

Obtain model results

data collection phase if possibledata collection phase if possible

Ensure results are consistent with known Ensure results are consistent with known operating conditionsoperating conditions

Analysis

DataCollection

DocumentationDocumentation

P&IDsandisometricdiagrams Datasheets Datasheets Operationalphilosophy Reportsp Anecdotaldata Failuresappearedtoincreaseaftercheckvalveinstalled

Flexible PipeFlexible PipeFlexiblePipeFlexiblePipeStructuralStructural

ComponentsComponentsComponentsComponents

FieldSurveyFieldSurvey

Verifieddocumentationandcollectedadditionalinformation

InstrumentedallthreeCDPs Did not go to stabilizer plant Didnotgotostabilizerplant

TransientHydraulicModelingTransientHydraulicModeling

UtilizedtheStonerPipelineSimulator(SPS) Slightly compressible liquids EOS SlightlycompressibleliquidsEOS

8-Inches Pipeline SystemCDP SP16-18: P-7310 47%, M15-06: P-6310 23%, M14-16: P-4310 78%

Pressure Elevation

500

600

700

7600

7700

7800

300

400

P

r

e

s

s

u

r

e

(

p

s

i

g

)

7300

7400

7500

100

200

7000

7100

7200

00 10000 20000 30000 40000 50000 60000 70000

Pipeline Distance (ft)

6900

8InchPipelineSystemPressurewithPulsation

700 35

Pressure Max. Pressure Min. Pressure Pulsation

500

600

25

30

400

500

u

r

e

(

p

s

i

g

)

20

25

i

o

n

(

p

s

i

g

)

200

300

P

r

e

s

s

u

10

15

P

u

l

s

a

t

0

100

0

5

00 10000 20000 30000 40000 50000 60000 70000

Pipeline Distance (ft)

0

SummaryResultsSummaryResults

Theresultsdidnotrevealaproblemrelatedtowaterhammer in either the pre existing or existing pipelineshammerineitherthepreexistingorexistingpipelines

Thepulsationswerealittlehighinthepreexistingpipeline but were not considered excessivepipeline,butwerenotconsideredexcessive

Transientsduringpumpstartandstopsweresignificant but were well within the limits of thesignificantbutwerewellwithinthelimitsofthepipeline

An investigation of failed composite pipeline sections Aninvestigationoffailedcompositepipelinesectionsrevealedthefailureoccurredfromtheinsideoutward

There was no creep and adjacent sections were burst Therewasnocreep,andadjacentsectionswerebursttestedtogreaterthan2timestheMAOP

WaterHammerAnalysisWaterHammerAnalysis Waterhammernotaproblem

Flowvelocitiesarelowandthereforethemomentumchangeislow

Nomechanismfoundforcausinganysignificantwaterhammer issueshammerissues

390

410

Averaged Pressure

2-Inch Pipeline Pressure

350

370

s

u

r

e

(

p

s

i

g

)

22--in pipe Rampin pipe Ramp--up up from 20%from 20%--100%100%

310

330

P

r

e

s

s

2900 2 4 6 8 10 12 14 16

Time (s)

TransientResponseAnalysisTransientResponseAnalysis

Startup&shutdowntransientsnotaproblemStartup&shutdowntransientsnotaproblem

SeveraltestcaseswererunwhichresultedinSeveraltestcaseswererunwhichresultedinsignificanttransientresponsesbutwerenotsignificanttransientresponsesbutwerenotg pg penoughtoleadtoapipelinefailureenoughtoleadtoapipelinefailure

There was no significant response related to theThere was no significant response related to theTherewasnosignificantresponserelatedtotheTherewasnosignificantresponserelatedtotheadditionofthecheckvalvehalfwayupthehilladditionofthecheckvalvehalfwayupthehill

Pulsation while small may play a significant part inPulsation while small may play a significant part in PulsationwhilesmallmayplayasignificantpartinPulsationwhilesmallmayplayasignificantpartintheflexiblecompositepipelinefailuretheflexiblecompositepipelinefailure

PulsationAnalysisPulsationAnalysis

PulsationsarestronglycorrelatedfailuresitesPulsationsarestronglycorrelatedfailuresitesPressure Max Pressure Min Pressure Failures Pulsation

25

30

600

700

Pressure Max. Pressure Min. Pressure Failures Pulsation

20

400

500

s

i

g

)

i

g

)

10

15

300

400

P

u

l

s

a

t

i

o

n

(

p

s

P

r

e

s

s

u

r

e

(

p

s

i 44--Inch Pipeline Inch Pipeline Pulsation and Pulsation and

Failure Failure C l tiC l ti

5

0

100

200 CorrelationCorrelation

000 10000 20000 30000 40000 50000 60000 70000

Pipeline Distance (ft)

FailureAnalysisFailureAnalysis AnalysisoffailedsegmentsrevealedfailurefrominsideAnalysisoffailedsegmentsrevealedfailurefrominside

outwardoutward

InnerInnerlinereruptedthroughouterlinerwithlittleevidenceoflinereruptedthroughouterlinerwithlittleevidenceofwaterbetweenlayerswaterbetweenlayers

HydroHydrotestingofadjacentsegmentsmetorexceededtestingofadjacentsegmentsmetorexceededspecificationsspecifications

Gl fib thGl fib th GlassfibersneartheGlassfibersneartheinnerlinertendedtoinnerlinertendedtohavejaggedbreakshavejaggedbreakswhereasfibersnearwhereasfibersneartheoutsidetendedtheoutsidetendedto be clean breaksto be clean breakstobecleanbreakstobecleanbreaks

FailureAssessmentFailureAssessment

Thereappearstobenoobviousfailuremechanism

Failuresoccursomewhatrandomlyandassoonasafailure is fixed another one appearsfailureisfixedanotheroneappears

However,thefailuresappeartocorrelateverywelltoth ith th hi h t l titheareaswiththehighestpulsation

Thepipevendorwarnsthatthepipeisnotdesignedforuseincyclicapplicationabove20%ofratedpressure(Cyclicisdefinedasapproximatelyonceperday)

FailureAssessment,continuedFailureAssessment,continued

Wetheorizethefollowing:Wetheorizethefollowing: Damage is incurred to the inner fibers due to the small Damageisincurredtotheinnerfibersduetothesmallpulsations,potentiallyfrombendingstressintheglass

This generates a weakness in the pipe which causes Thisgeneratesaweaknessinthepipewhichcausesincreasingstressinthatarea

Individual fibers continue to break further staining theIndividualfiberscontinuetobreakfurtherstainingtheremainingfibers

Thefailureoftheouterfibersoccursuddenlywhentheytensilestrengthofthefiberisexceededleavingacleanbreak

Astheglasslayerisweakenedtheinnerlinerbulgesoutwardbeforeeruptingthroughtheouterliner

FailureAssessment,continuedFailureAssessment,continued

FromandO&Mstandpoint,thiswouldappeartobesomewhatlikeoperatingametalpipeabovetheendurancelimitwithpulsation

Evenasmallpulsationcaneventuallyleadtopipelinefailure

Onceanfailedareaisrepairedthestressesbuildupelsewhere

Summary&ConclusionsSummary&Conclusions

Failureslikelyduetosmallcyclicstressesintheglassfibers

Lessonlearned,verifythatyourassumptionsarecorrectandreviewalldatainthefieldwhenprovidedtheopportunity

Noevidencetosupportwaterhammerasanissuef h h h h lforeitherthe4inchor8inchpipeline

Therevisedoperatingphilosophyisasubstantiali h f h i iimprovementoverthatofthepreexistingsystem

Pulsationsarenotasignificantthreattothei i f h 8 i h l i li b bintegrityofthe8inchsteelpipeline,butmaybeasignificantfactorinthefailureofthe4inchpipeline

ModelingandSimulationModelingandSimulationggTransientAnalysisCaseStudyofTransientAnalysisCaseStudyof

Li id G th i S tLi id G th i S taLiquidsGatheringSystemaLiquidsGatheringSystem