American Journal of Engineering Research (AJER)2015 American Journal of Engineering Research (AJER) e-ISSN: 2320-0847p-ISSN : 2320-0936 Volume-4, Issue-8, pp-64-74 www.ajer.org Research PaperOpen Access w w w . a j e r . o r g Page 64 Computer Aided Design (CAD) for Failure Analysis in a Crude Oil and Gas Carbon Flow line ALAO Kehinde T. 1, OLALERE Olusegun A.2,ADEYI Oladayo3, OLADAPO Micheal A.4 1, 4 (Department of Mechanical Engineering, Ladoke Akintola University of Technology, Ogbomoso, Nigeria.) 2(Department of Industrial & Production Engineering, University of Ibadan, Oyo State, Nigeria) 3 (Department of Chemical Engineering. Landmark University Omu-Aran, Kwara State, Nigeria) ABSTRACT: The failure analysis in flow lines comes to relevance in order to prevent the menace attached to failures; financial losses, dangers to workers, and production breakdowns. Hence the materials used must be of good mechanical properties, low cost and of wider availability. Thepressuredistribution and stress analysis wereestimated by varying the diameter and pressuredrop in the pipe. These were subsequently obtained from a set of mathematical models computed and displayed through the use of a simulated computer aided design auto inventor-based software.TheresultsobtainedfromtheComputeraideddesignshowedthestressinducedinpipeduringfailure.By varying pressure the maximum operating pressures increases at constant diameter of pipe, with a corresponding increaseinpipestress.Italsoshowstherateatwhichliquidflowthroughthepipeatvaryingmaximum operating pressures and diameter together. From result obtained also, the wall thickness of the pipe should not be less than 0.25 inch (6.35mm) This study helps to analyze oil pipeline failures in Nigeria with the aim to undertake a desk study to evaluate the procedures for maintenance and contingency plans for addressing oil pipeline failures in Nigeria. Keywords:Crude oil, computer-aided-design (CAD), failure analysis, pipeline (flow line), pressure drop I.INTRODUCTION The failure of components and materials of most machines and machineries is one of the most dreaded situationsinanyproducingestablishmentduetothebuoyantnatureofthestudy.Hencethereisaneedfora propermonitoringwithutmostscrutinyinthedesignandproductionofpipes/flowlinesusedinoilandgas industryinordertopreventdistortioninoilandgasproduction.Distortioninproductionasregardspipingis generallyinducedbythefailureofthesepipesmeetingupwithproperdesigncodesandcriteria.Theyare thereforesaidtobefailingortohavefailed,dependingontheseverityordiscrepancyfromdesigncriteria beforetheultimatemodeoffailure-rupture.Pipelinesarecommonlymadeofcarbonsteelsduetheirgood mechanical properties, low cost and wider availability. However, in spite of good properties exhibited by carbon pipes, their resistance to corrosion is relatively low. Normally, as an oil well ages, the production of oil starts to declinewhereas water and gas flow rates tend to increase. The presence of high corrosive agents such as CO2, H2Sandchlorinecompoundsdissolvedinthefluidscanthereforeacceleratecorrosionprocessinsidethe pipeline.Hence,theimpactofchangesinfluidcompositiononapipelineshouldbeanticipatedduring maintenanceprogram.Oilleakshavebeenrecentlyreportedtooccuratahorizontalcrudeoilsubseapipeline after 27 years in service. During operation, crude oil was pumped from subsea wells into the horizontal pipeline and crude oil was then flowed out from the pipeline directly into a long radius elbow section which turned the crude oil flow vertically allowing the flow to pass through a riser for further processing in the platform [1].Hence,failureanalysis comes to relevance in order to prevent themenaceattached to these fractures, financial losses, dangers toworkers and personnel, production breakdowns and also thelikelihood to spark up anepidemic.Failureanalysisanddesignhelpstomaintainandgivethepipingsystemsdrawingapredictive forecast and thus apreventivemaintenance strategy against possible causes offailuressuch as corrosion, sand American J ournal of Engineering Research (AJ ER)2015 w w w . a j e r . o r g Page 65 erosion(depletingthicknessofpipesfromtheinside),excessivestressinpipes,fluctuatingpressureeffects, fatigue etc. These effects have posed perennial difficulties to the oil and gas industry, hence the untiring efforts toalwaysfindnew,workabletechniquesandmethodsintoanalyzingtheflowlinetodesigningpossible solutions.Furthermore,theenormousdividendsgeneratedfromtheoilandgasindustryhashelpedputmore concern into the close monitoring of the pipes efficiency over a good period of time andthus reducing possible hazards to a barest minimum. This research work will be encompassing; evaluation of crude oil flow parameters such as pipe thickness, working pressure, oil flow pressure, temperature, stresses in pipes etc. and their relation to each other using the carbon steel pipe alone as our case study. II LITERATURE REVIEW 2.1Preamble Majorpipelinesacrosstheworldtransportlargequantitiesofcrudeoil,naturalgas,andpetroleum products.Thesepipelinesplayacrucialroleinprovidingneededfuelsforsustainingvitalfunctionssuchas powergeneration,heatingsupply,andtransportation.However,duetothehazardouspropertiesofthese productstransmitted,arupturedpipelinepresageseriousenvironmentalproblems.Thisproblemisfurther compoundedbythefactthatmanydevelopingcountrieshavenotyetestablishedproperguidelinesand standardsforthedesign,construction,andoperationofmajoroilpipelines.Thisstudyhelpstoanalyzeoil pipeline failures in Nigeria with the aim to undertake a desk study to evaluate the procedures for its maintenance and contingency plans for addressing oil pipeline failures in Nigeria. The risk associated with pipeline in terms ofsafetyofpeople,damagetotheenvironmentandlossofincomehasbeenamajorconcerntopipeline integritymanagers.Agbaeze(2000)mentionedhisviewonhowtoimprovepipelineIntegrityManagement, opining that pipeline operators can realize many benefits by implementing a data integration approach that will enablesintegritymanagers,riskassessmentspecialistsandpiggingengineerstoviewandanalyzecombined information from disparate surveys and to increase the value of data by shaving it across the entire corporation [2]. There have been a number of studies conducted by researchers on causes of oil pipeline failures in the oilandgasindustry.IkporukpoandChris,(1998)examinedthecausesofpipelineleaksversuspipeline rupturesandtheproportionforeach.Infailuresresultinginproductloss,leaksconstituted86.8%offailures and ruptures 13.2 %. Corrosion is the predominant cause of leaks. According to his findings, third party damage is the leading cause of line ruptures. Since 1994, 191 hits were recorded, and these are not included as they did notresultineitherleaksorruptures.Thehitsequaled47%ofallrecordedthird-partyincidentsfortheyears 1994-1997,demonstratingthatapproximatelyhalfofallthirdpartyincidentsresultedinapipelinefailure. Reference showed that about 50 % of third-party incidents resulted in loss of pipeline products [3]. The number ofinternalcorrosionfailuresformultiphasepipelinesanddiscoveredthatinternalcorrosionfailuresincreased steadily while the number of external corrosion failures held steady.They stated for sour gas pipelines, internal corrosion is the major cause of failure [4]. External corrosion failures have declined in recent years, possibly as the result of improved coatings and increased inspection. Of the sour line failures, about 86 % were leaks and 14 %wereruptures.Theyusedthelatesttechnologyinthefieldsofinternalelectronicinspection,metallurgy, coatings, cathodic protection, and chemical inhibition. Nwankwoet al., (2012) and Odusola (2012) extensively studied the effects of internal corrosion failures for natural gas pipelines which have generally been increasing. Some "other" category which include high vapour pressure liquids, low vapour pressure liquids, fuel gas, and all others showed failure rates to be relatively few and the causes to be relatively random.Ilman (2014) worked on subsea crude oil steel pipeline oil leakage whose failure was caused by electrochemical corrosion combined with mechanical process known as flow induced corrosion [1]. 2.2Flow of crude oil and causes of leaks and ruptures in flow lines Oil pipelines transport liquidpetroleum productsfrom onepoint to another. Therearegenerallythree types of oil pipelines: Gathering lines: travel short distances, collect unprocessed oil products from wells and deliver them to oil storage tanks. Pipes range from 4 to 12 inches in diameter Feeder lines:move product from oil storage tanks and processing plants to the transmission pipelines. They are generally bigger than gathering lines, but smaller than transmission lines.Transmission lines:can be up to 48 inches in diameter and transport oil and associated products from producing to consuming areas, including across provincial and international boundaries. The oil is piped to refineries where it is refined into petroleum products. American J ournal of Engineering Research (AJ ER)2015 w w w . a j e r . o r g Page 66 Source: Amec Paragon, (2013) Figure 1: Represent the flow line, gathering line and the transmission line Internalcorrosion,externalcorrosion,externalintervention(forexample:hitbyatruckor back-hoe), soildisplacementsuchaslandslides,materialdefects,andsystemmalfunctions(forexample:operatingover design pressure) can cause leaks and ruptures. Based on incidents reported to the National Energy Board (2010), themajorityofleaksarerelatedtopumpstationsandvalves,ratherthanthebodyofthepipeline.Ingeneral, corrosion accounts for about 20% to 30% of pipeline leaks. 2.3Failure Analysis Theflowlineitselfcanbeclassifiedtobeapressurevesselinthatitworksundercertainservice pressure requirement and hence a vessel because it is enclosed and used as a leak proof transport medium from oneendtoanother.Vesselfailurescanbegroupedintofourcategorieswhichdescribewhyavesselfailure occurs; failure can also be grouped into types of failures, which describe how the failure occurs. Each failure has awhyandhowtoitshistory.Itmayhavefailedthroughcorrosionfatigueorbecausethewrongmaterialwas selected. The different Categories of Failures were analyzed by Ilman and Kusmono (2014). Failureduetomaterial:Selectionofflowlinematerialsisimportantsoastopreventreactionofthe hydrocarbon element with the internal surface of the flow line thus, preventing corrosion and to be able towithstand other externalfactors. When selectingmaterial,considerationmust begiven tomaterials withgoodmarketavailability,documentedfabrication,serviceperformance,operatingcondition, corrosion monitoring possibilities and compatibility to other materials to be used. Failure due to design: For the design of a pipeline, the overall thickness, addition of intermediate leak proofsheath,increasingthemomentofinertiatowithstandpressureandalsoselectingcathodic protection system design to prevent corrosion etc to make the overall flowline last longer. Failureduetofabrication:Whenfabricating,favourablecombinationofweldability,strength, corrosionresistancetogetherwiththeconditionoftheenvironmentinwhichthepipelinewillbe installedmustbecarefullyconsidered.Also,whenfabricating,thematerialmustbesubjectedto pressure testing to detect failures related to welding, strength etc. Failure due to service: Regularly scheduled inspections, evaluations and testing by qualified personnel arecriticalpartofpreventingfailure.Theirpurposeistoprevent,predictandreadilydetect discharges/leakages.Soactiveandregularservicecheckmustbedoneonthisflowlinetoprevent failure. III RESERCH METHOD AND MATERIAL The research work involved a full understanding of what failure is all about. To this effect there is theneed to have an overview of the root cause of failure, the methods used in this study involves the following; 1.Libraryand online research2.Questionnaire survey3.Oral interview4.Physical observation and mathematical model 5.Computer Aided Design 3.1Field SurveyInordertoexaminetherootcauseoffailure,severalcasesoffailurethathaveoccurredwerecriticallylooked into. Selected team of field workers, inspection officers were posed with questions based on failure in flow lines. Some of the questions asked are highlighted below. American J ournal of Engineering Research (AJ ER)2015 w w w . a j e r . o r g Page 67 How long was the part in service? What was the nature of the stresses at time of failure? Was the part subjected to an overload?Was the part properly installed? Was it subjected to service abuse?Were there any changes in the environment? Was the part properly maintained?What was the service/ normal pressure of the crude oil coming from the well and going out of the well?How and where did the failure occur? Whatistheprimarycauseofthefailure(lack):corrosion,dent,humansabotageinadequateservice demand etc? What existing failure analysis instrumentation do they have or work with? Fieldtestingpermittedtheevaluationoftheeffectsofmaterials,designandfabricationvariableson performance of theunder-controlled conditions, by combining theinformation from testswith theresults from analysis; a clear picture of the causes of failure was obtained. While studying failure, care was taken to avoid destroying important evidence. Detailed studies usually require documentationofservicehistory(time,temperatureloadingenvironmentetc)alongwithchemicalanalysis, photomicrographs and the likes. 3.2Computer Aided Design (CAD) Use of computer programme C++ and Auto Inventor was extensively used in this project work. C++ was used to analyze data gotten from industry to give a better operating pressure with a perfect diameter and to monitor the pressuredropalongthepipeline.Thesolidworkdesignshowstheeffectofstresscausedonthepipedueto variation of operating pressure and diameter of the pipe. 3.3. Mathematical model for stress analysis through computational method` Theflowlinethicknessvariesfromdifferentsectionstoanotherduetovariationinpressureandtemperature. The thickness of the flow line from the well to the flow station and finally to the refinery or terminals must not be minimum to the one needed for a specified pressure and temperature.CPy SEPDtm) ( 2(1) Where,tm= Minimum flow line wall thickness (in) allowable on inspectionP=Maximum internal service pressure gauge (1b/in2) D=Outside diameter of pipe (in)S=Maximum allowable stress in material due to internal pressure (1b/in2) ) E=Quality factorY=A coefficient, values for which is in the standard codeC=Allowance for threading mechanical strength and corrosion (in) with values listed in the standard code. 3.3.1 Stresses in Members The stresses in members are shown in equations (2) and (3) below.

=

(2)

(3) Where, American J ournal of Engineering Research (AJ ER)2015 w w w . a j e r . o r g Page 68 Km= spring constant of memberFm= tensile force in the bolt S Um= the amount by which the member is extended when it is loaded from zero to fm Sm=Stress in memberAm=Area of the member 3.3.2Pressure drop in pipelines Thepressuredropinpipe,duetofrictionisafunctionofthefluidflow-rate,fluiddensityandviscosity,pipe diameter,pipesurfaceroughnessandthelengthofthepipe.Itcanbecalculatedusingthefollowingequation below Pf = 8f (

)2(4) Pf = Pressure drop, N/m2 f = Friction factor L = Pipe length, m di = Pipe inside diameter, m = fluid density, Kg/m3 u = fluid velocity, m/s IV RESULT AND ANALYSIS 4.1Data Presentation For an effective assessment of the failure in flowline, a computer software progamme was written using C++,andvaluesweregeneratedfortheanalysis.Theseprogrammeswereusedtoimplementthesetsof equations that were supplied. Data generated were analyzed and a design simulation was shown using AutoCAD inventor.Hence,applicable/workablefailureindiceswereobtained,practicalenoughtopredictthepossible period which failure may occur, conditions under which it may occur and period of tolerance before the ultimate mode of failure rupture. 4.2Parameter values The following data were collected from various oil fields/oil companies within the country. These data are those analyzed and results presented in subsequent sections. Table 1: Data of Parameter Values from Oil Field Type of system Hazardous liquid Accident type: Pipe failure and leak Material release: Crude oil API 35.6 Value Units Maximum operating pressure (MOP)800Psi Outside diameter of pipe (D)12.750In Specified minimum yield strength (S)42,000Psi Normal wall thickness of pipe (T)0.25In Design factor (quality factor E) (F)0.72In Maximum depth of corroded area (C)0.080 Pit depth percentage (C/t)32.0% Constant for maximum allowable Pressure (G)3.003 Safe maximum (derated) pressure for corroded area (Pd)11,100Psi Fluid velocity(U)0.4m/s Friction factor (f)0.07 Year in Service period of pipe is between (1993 2001)6Years Source: ICPI, Abuja (2012) From the data provided American J ournal of Engineering Research (AJ ER)2015 w w w . a j e r . o r g Page 69 4.3Calculations and Analysis Using stress analysis through computational method Using equation 3. And analyzing the data through C++ application t m=

2+ + C(5) Making S the subject of the formular; S = 2()2m(6) MOP P = 800 Psi D = 12.750 in tm = 0.250 in E = from the data table(F Design factor) = 0.72 Y = 0.4C = 0.080 Calculation from our C++ application shows the amount of stress exacted on the pipe during the time of failure as41222.22ib/in2 Plate 1:C++ programmed showing the calculation of stress exacted on the pipe at 800 psi American J ournal of Engineering Research (AJ ER)2015 w w w . a j e r . o r g Page 70 Theanalyzesofthestressinducedinthepipebyvaryingbothpressureanddiameterataconstantmaximum operating Pressure of 800 Psi is given in table 2 below. Table 2: Results Generated at Constant pressure and varying pressures and diameters MOPDiameter of pipe (in)Stress induced in the pipe (ib/in2) 800928967.3202 8001032235.2941 8001135503.2679 8001238771.2418 80012.7541222.2222 Table 3: Results Generated at a constant diameter of 11 inch MOPDiameter of pipe (in)Stress induced in the pipe (ib/in2) 7001131065.3594 7501133284.3137 8001135503.2679 8501137722.2222 9001139941.1764 Table 4: Results Generated at a constant diameter of 12 inch MOPDiameter of pipe (in)Stress induced in the pipe (ib/in2) 7001233924.8366 7501236348.0392 8001238771.2418 8501241194.4444 9001243617.6471 Table 5: Results Generated At a constant diameter of 12.75 inch MOPDiameter of pipe (in)Stress induced in the pipe (ib/in2) 70012.7536069.4444 75012.7538645.8333 80012.7541222.2222 85012.7543798.6111 90012.7546375.0000 American J ournal of Engineering Research (AJ ER)2015 w w w . a j e r . o r g Page 71 Figure 2:Stress induced in a pipe of diameter 12.75 inch and MOP of 700 Psi 900 Psi Figure 3:Stress induced in a pipe of diameter 11 inch and MOP of 700 Psi 900 Psi Figure 4: Stress induced at a constant diameter of 12 inch and MOP of 700 Psi 900 Psi. 700 750 800 850 90012.75 12.75 12.75 12.75 12.7536069.444438645.833341222.222243798.611146375010000200003000040000500001 2 3 4 5MOPDiameter of pipe (in)Stress induced in pipe (ib/in)700 750 800 850 90011 11 11 11 1131065.359433284.313735503.267937722.222239941.17640500010000150002000025000300003500040000450001 2 3 4 5MOPDiameter of pipe (in)Stress induced in pipe (ib/in)700 750 800 850 90012 12 12 12 1233924.836636348.039238771.241841194.444443617.6471010000200003000040000500001 2 3 4 5MOPDiameter of pipe (in)Stress induced in pipe (ib/in)American J ournal of Engineering Research (AJ ER)2015 w w w . a j e r . o r g Page 72 American J ournal of Engineering Research (AJ ER)2015 w w w . a j e r . o r g Page 73 Plate 6: Simulation of the effect of pressure at 6.2052 MPa (900 psi) on an 11 inch pipe 4.4Pressure drop calculation Using equation 3.6 and using the C++ application Pf = 8f (

)2(7) f = 0.07 s L = 1000m (1Km) di = 10.25 in = 847 for API 35.6 u = 0.4 m/s The pressure that will be drop in the pipe in a distance of 1000m/1km will be 21.11 psi, therefore at about 38 km at most, there should be a pressure booster in place to increase the pressure back to the maximum operating pressure. Plate 7 shows the pressure drop calculation from the C++ programme. Plate 7: C++ Programme showing the pressure drops in a pipeline American J ournal of Engineering Research (AJ ER)2015 w w w . a j e r . o r g Page 74 V. DISCUSSION From thecomputer aided design (CAD) of thestress induced duringfailure, resultswereobtained by varying both the pressure and diameter shows that at constantmaximum operating pressure, the diameter of the pipediameterincreasesduetothedensityoftheliquidstressinduced.Hence,atconstantdiameterof11inch (279 mm), 12 inch (305 mm), and 12.75 inch (324 mm), the higher the maximum operating pressure,the higher the stress induced in the pipe. Thefigure2showsthegraphicalrepresentationofthestressinducedbetweenadiametersof9inch-12inchat constant maximum operating pressure of 800 psi (5.5158 Mpa) while figure 4.3 isthe graphical representation of stress induced at a constant diameter of 12inches and a maximum operating pressure of 700 psi (4.8263 Mpa) -900psi(6.2052Mpa).However,thisvariestherateofstressdifferenceatseparatemaximumoperating pressure value with graphical authentications. The rate at which liquid flow through the pipe at varying maximum operating pressures and the representation of stress induced ata constant diameter of 12.75 inches and maximum operating pressureof 700 psi900 psi were illustrated in figure 5. The Plate 2 and 3 shows the simulation of the effect of pressure at 800 psi (5.5158 Mpa) on a 10 and 12 inch pipe. This was extracted from the auto desk inventor, showing the increment of the pressure distribution in the pipe. The design showed the pressure distribution in the 10 inch pipe and 12 inch pipe. For the 12 inch pipe, the pipe experiences much pressure at the opening and edge. And plate 4, 5, and 6 show the simulation of the effect of 700 psi, 800 psi and 900 psi on a pipe of 11inch diameter. It shows the pressure distribution in the pipe and also shows that stress is much concentrated at the edge/opening of the pipe. VI. CONCLUSION Thepressuredistributionandstressanalysiswereestimatedbyvaryingthediameterandpressuredropinthe pipe. These were subsequently obtained from a set of mathematical models computed and displayed through the use of simulated computer aided design auto inventor-based software. The computer aided design showed the effect of the data analyzed (pressure anddiameter) on the pipe and also showed the overall effect on the pipe through simulation of the parameters given. Alevelofdependencewereobtainedfromthemodelandtheresultsrevealedtheircorrespondingstress according to the given operating parameters. Furthermore, it was authentically observed that at a pressure of 800 psi (5.5158 Mpa), the 10 inch (254 mm) -11 inch (279 mm) diameter pipe will be the most suitable for use, due to the pressure distribution observed through the Auto Inventor design software.Therefore, this study can be successfully employed in the selection of pipelines as it is interchangeably used in this research work, as well as for other types of pipe specifically for crude oil, as long as the fluid properties for thetypeoffluidtobecarriedandoperatingparametersareknown.Thisstudyhelpstoanalyzeoilpipeline failuresinNigeriawiththeaimtoundertakeadeskstudytoevaluatetheproceduresforitsmaintenanceand contingency plans for addressing oil pipeline failures in Nigeria REFERENCES [1.] Ilman,M.NandKusmono;AnalysisofinternalcorrosioninsubseaoilpipelineDepartmentofMechanicalandIndustrial Engineering, Gadjah Mada University, Jl. Grafika NNo. 2, Yogyakarta 55281, Indonesia. Elsevier2014). [2.] Agbaeze, K. N ;Petroleum Pipe Leakages PPMC Report for Chief Officers Mandatory Course 026, Lagos (2000); [3.] IkporukpoChris;Environmentalimpactassessmentandhumanconcerninthepetroleumindustry:Nigeria'sexperience,9th International Conference on the Petroleum Industry and the Nigerian Environment, Abuja,766 782. [4.] Ndifon, W. O.; Health impact of a major oil spill: Case study of Mobil oil spill in Akwa Ibom State, 9th International Conference on the Petroleum Industry and the Nigerian Environment, Abuja, 1998,804 - 815. [5.] International Conference on the Petroleum Industry and the Nigerian Environment, Abuja,2012,.358-368 [6.] Nwankwo, D. I., Chukwu, L. O., and Brown, C. O.; The impact of oil pollution on the hydrochemistry andbiota of the tidal creeksandcanalsinOndoState,9thInternationalConferenceonthePetroleumIndustryandthenNigerianEnvironment, Abuja,2012,538-576. [7.] Odusola,A.F.;CommunityParticipationinEnvironmentalAssessment;InEnvironmentalPolicyPlanning,P.C.EgbonandB. Morvaridi Eds., National Centre for Economic Management and Administration (NCEMA), Ibadan,1996,152-174. [8.] Paragon.ArgonneNationalLaboratory.EnvironmentalScienceDivision(ANL/EVS/TM/08-1).U.S.DepartmentofEnergy, office of Scientific and Technical Information, U.S.A. 2010.