“Thickness optimization of inclined pressure vessele

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“Thickness optimization of inclined pressure vessele

  1. 1. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME AND TECHNOLOGY (IJMET)ISSN 0976 – 6340 (Print)ISSN 0976 – 6359 (Online)Volume 3, Issue 3, September - December (2012), pp. 682-689 IJMET© IAEME: www.iaeme.com/ijmet.aspJournal Impact Factor (2012): 3.8071 (Calculated by GISI)www.jifactor.com ©IAEME “THICKNESS OPTIMIZATION OF INCLINED PRESSURE VESSELE USING NON LINEAR FINITE ELEMENT ANALYSIS USING DESIGN BY ANALYSIS APPROACH” I.M.Jamadar1, S.M.Patil2, S.S.Chavan3, G.B.Pawar4, G.N.Rakate5 1,2 Assistant Professor, Department of Automobile Engineering, Annasaheb Dange College of Engineering and Technology, Ashta-416301, Maharashtra, India. E-mail: imranjamadar2@gmail.com 3,4,5 Assistant Professor, Department of Mechanical Engineering, Annasaheb Dange College of Engineering and Technology, Ashta-416301, Maharashtra, India.ABSTRACT Nitrous oxide (N2O) has been produced and distributed by the industrial, gasindustries for many years. It is mainly used for medical purposes (anesthesia). It is also usedin the food (whipped cream) and electronic industries. Severe accidents such as violentdecomposition of N2O and rupture of N2O tanks have occurred at production, storage anddistribution facilities. A major cause of N2O accidents has been insufficient attention to thespecific properties of N2O when designing equipment and developing operating procedures.On this basis, the principles and relevant details of safe production, storage and distributionof N2O are considered. The Objective of the Inclined Pressure Vessel (IPV) is to have largescale production of Nitrous Oxide. The rate of the reaction and its temperature is controlledby the inclination of the vessel. This investigation primarily deals with the probable causes ofin-service damage of IPV with approximate estimation of stresses using Finite elementanalysis (FEA).Keywords: IPV-Inclined Pressure Vessel.FEA-Finite element analysis.I. INTRODUCTION Specifically Nitrous Oxide is obtained by “ammonium nitrate pyrolysis synthesis”. Itis exothermic reaction occurring at around 200 deg C. Ammonium nitrate is a moderatelysensitive explosive and a very powerful oxidizer. Above 240 deg C, the nitrate can evendetonate. Hence, it is imperative to maintain temp below 240 deg C .The rate of the reactionand its temperature is controlled by the inclination of the vessel .At lower inclinations (Closer 682
  2. 2. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEMEto horizontal) the reaction will progress rapidly, as the steam will spread more and expose tomore surface area of ammonium nitrate. As the inclination will increase, the steam will riserapidly and escape to top chamber, causing the rate of reaction to reduce, thus in effect theinclination will control the rate of reaction, which is an exothermic reaction. This in turn willcontrol the temperature of the reaction. Hence the temperature will be mostly maintainedaround 200oC. This reduces the cost of control, plus rate of reaction can be controlled withouthampering the process.II. CONSTRUCTION It consists of oblique elongated inclined reactor. The vessel is closed at both the endsby conventional heads. Lower end is provided with furnace to supply steam which iscirculated around the ammonium nitrate through steam pipe. Ammonium Nitrate receives theheat from steam pipe and undergoes pyrolysis, forming water vapors and nitrous oxide gaswhich are collected and separated out from upper end.III. DESIGN CHALLENGES From a design point of view, we can categorize the challenges as temperatures are tobe maintained at 200oC, can cause considerable thermal stresses and Inclined nature of vessel(ASME code enables design of Horizontal or a Vertical vessel .No provision for an inclinedvessel in it.)In Horizontal Vessels, the key challenge is the bending that will occur at thecenter. In such a case the vessel, behaves more like a beam supported at two ends with centralbending. In Vertical Vessels, the key challenges are the bending loads that will occur at basedue to wind load. In such a case the vessel will behave more like a cantilever beam supportedat the base. In inclined vessels both wind deflection and central deflection has to beconsidered, plus we need to account for the temperature based stresses. In addition theinternal weights in the system will be a function of the angle of inclination which will have tobe considered.IV. DESIGN BY ANALYSIS (DBA) Design by analysis uses stress analysis directly. The maximum allowable load for thedesign is determined by performing a detailed stress analysis and checking against specifieddesign criteria. Design by analysis can also be used for calculating the component thicknessesfor pressure vessel components [2]. In the early days of DBA, the analysis methods werefocused on linear elastic stress analysis. This is mainly so because inelastic analysis requiredconsiderable computer resources which at the time were not present. However as computersbecame more powerful inelastic analysis has become more popular. The DBA procedureswere developed with the assumption that shell discontinuity analysis would be used for thecalculations. Today the Finite Element Method (FEM) is the most popular approach for usingDBA.V. FINITE ELEMENT ANALYSIS FOR PRESSURE VESSEL DESIGN Design engineers must use their experience and the latest design tools to maintainreasonable safety levels while providing the most cost effective design. One tool being usedon an ever increasing basis is Finite Element (FE) analysis software [1]. The current 683
  3. 3. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEMEcapabilities of FE software on desktop computers provide pressure vessel design engineerswith the ability to employ FE analysis on a nearly routine basis. Pressure vessel design engineers musthave a reasonable understanding of FE fundamentals to adequately use this design tool. Theengineer must determine the most appropriate modeling approach; select the proper elementsand solution technique to assure a reasonable analysis. The engineer must also determine ifthe model is reacting correctly and presenting reasonable results.VI. STRESS ANALYSIS OF IPV In dealing with the various modes of failure, the designer must have at his disposal apicture of the state of stress in the various parts. It is against these failure modes that thedesigner must compare and interpret stress values. But setting allowable stresses is notenough! For elastic instability one must consider geometry, stiffness, and the properties of thematerial. Material selection is a major consideration when related to the type of service.Design details and fabrication methods are as important as “allowable stress” in design ofvessels for cyclic service. The designer and all those persons who ultimately affect the designmust have a clear picture of the conditions under which the vessel will operate. Thisinvestigation primarily deals with the probable causes of in-service damage of IPV withapproximate estimation of stresses [11]. The design temperature and pressure of vessel are148.880C and 1.38795Mpa, respectively. There were four numbers of openings, Viz.entryand exit of steam, Exit of Nitrous oxide and drain. The vessel thickness was around 9.6mm,length 1275mm; inner diameter304.8mm.Stress analysis was carried out by finite elementmethod using ANSYS 13.0 code. Both the ASME (2007) code and the EN13445-3 (2002)code regulate that the safety coefficient is 2.4 and thus the design stress strength is Sm=min(460/2.4, 250/1.5)=166.66MPa.Material Selection: Usually material in pressure vessel technology are ductile, the plasticflow does not necessarily restricts the usability. Limited plastic flow in testing and in normaloperating load cases is admissible, even if it may occur repeatedly; it is taken into account inconstitutive laws of material models. Because of plastic flow DBA is restricted tosufficiently ductile materials at operating temperature below creep region. Properties Density 7.85e-006 kg mm^-3 Isotropic Secant Coefficient of Thermal Expansion 1.2e-005 C^-1 Specific Heat 4.34e+005 mJ kg^-1 C^-1 Tensile Yield Strength MPa 250 Tensile Ultimate Strength MPa 460 Reference Temperature C 22 0 Design Temperature in C 148.88 Youngs Modulus MPa 2.e+005 Poissons Ratio 0.3 Bulk Modulus MPa 1.6667e+005 Design Pressure, MPa 1.37895 Allowable Stress, MPa 166.67 684
  4. 4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEMEModel Geometry: In evaluating the geometry, there are several prime considerations. Inaddition to the necessity to accurately represent the actual geometry of the vessel orcomponent of the vessel, one must consider the loading and support (boundary) conditionsand the mesh to be employed. The extent of the vessel or component modeled is also of primeconcern when the decision is made to model only part of an overall system. Modeling of thepressure vessel was done using CATIA V5R17 software. Later on to model was imported toANSYS 13 where symmetric model was prepared, and then accordingly vessel was tilted torequired inclinations. Figure.1 Full Model in CATIAV5R15 Figure.2 Mehing with higher order brick elementElement Selection and Meshing: Once the geometry of the object to be analyzed is defined,the first task is to select the type of element that is to be employed. For most pressure vesselanalyses, the element selection is made from three categories of elements: axisymmetric solidelements, shell/plate elements and 3-D brick elements. Although nearly all problems can besolved using 3-D brick elements, the other two types offer significant reductions in thesolution time and effort where they are applicable. Often, this reduction in solution effort issignificant enough to make the use of FE analysis feasible where it might not be with 3-Dbricks. The higher order hexahedron element was used for meshing. The element is definedby twenty nodes.Boundary Conditions: The whole vessel is supported on two saddle supports. One saddle isa fixed saddle while the other is a sliding type saddle. The upper saddle was fixed while tothe lower saddle cylindrical support was provided. All degrees of freedoms of are constrainedfor fixed saddle while sliding saddle provides free sliding along axis of vessel. Loadings: The vessel was analyzed for internal pressure 1.38 MPa, plus Thermal loads fromsteam at 148.880C plus Self Weight. 685
  5. 5. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEMEVII. RESULTS AND DISCUSSIONVariation of stresses with respect to angle of inclination is given below: Equivalent Von- Angle, Total Maximum Mises Stress, Nodes Elements [Degree] Deformation, [mm] [MPa]0 123.41 1.7265 371000 911034 126.12 1.7268 365123 902368 131.24 1.7238 364213 9312512 150.8 1.7465 374256 9456316 176.56 1.7524 375136 9514520 190.8 1.7892 375812 9520024 210.61 1.8093 371365 9242828 225.6 1.8564 370152 9083232 242.38 1.8916 375180 94471ANSYS Results Plot:Figure 3- Linearised Stress along Vessel Thickness Figure 4- Linearised Stress V/s vessel ThicknessFigure 5- Linearised Stress along Nozzle Thickness Figure 6 - Linearised Stress V/s Nozzle Thickness 686
  6. 6. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME Figure 7 - Equivalent Stress Along Vessel-Nozzle Intersection with reinforcement padThickness optimization resultsVariation of stresses with respect to the thickness of vessel for maximum inclination angle of320 are given below Stress at Membrane Bending Total Thickness, Membrane+Bending nozzle- Stress, Stress, Stress, [mm] Stress, [MPa] Vessel [MPa] [MPa] [MPa] Intersection 11.336 16.887 13.197 27.626 28.652 39.147 9.489 22.222 15.756 34.332 34.63 61.964 7.2875 30.759 16.856 42.41 42.061 10741 6.0275 38.001 15.648 48.049 47.743 139.4 5.4671 46.859 19.968 57.824 57.81 178.45 5.6 with 33.066 24.843 53.987 57.938 87.179 RF PadVIII. EXPERIMENTAL TESTING1) Ultrasonic testing: At Nozzle-vessel Intersection:Weld spot at nozzle vesselinteersection tested with an ultrasonic probe positioned on it and transmitting sound pulsesinto the weld metal, as well as the echo sequence generated on the screen display of theultrasonic instrument.This sound pulse is transmitted from the probe into the weld spot andpartially reflected from the interface between the probe and weld spot. This reflection appearsas interface echo at sound entry (1st indication to the farthest left) on the screen display of theultrasonic instrument. The continuous part of the pulse enters the weld spot and is onlyreflected from its rear boundary, provided there is no flaw. This reflection is displayed as 1stbackwall echo to the right of the interface echo. The sound pulse can run several times backand forth between the front and rear end of the weld spot, and delivers a part of the soundpulse to the probe every time it hits the front end. This ever decreasing part of sound pulse is 687
  7. 7. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEMEdisplayed as 2nd, 3rd, 4th backwall echo at the same intervals on the screen. In thisconnection, the interval between the individual backwall echoes corresponds to twice thematerial thickness (round trip within the material). If there is a flaw in the weld spot, e.g. inthe form of a gas pocket, a part of the sound pulse correspoding to the size of this flaw isadditionally reflected from it. As the flaw is situated between the front and rear end of theweld spot, the corresponding flaw echoes also occur between the backwall echoes. In the caseof major weld flaws, the flaw echoes are higher and possibly only recognizable.2) Hydro-testing : Vessel was also tested for hydro-test pressure of 1.5 MPa andtemperature 1500C which are slightly higher than the operating values. Also at the same timestrain gauges (LC 4CI X- HBM ) are mounted at the saddle supports and at the nozzle-vesselintersection for measuring the deformations.IX. CONCLUSIONS As seen from the table, the stresses in the vessel thickness are increasing withreduction of thickness. Here, membrane and bending stresses are within allowable limits forall cases considered. But the equivalent Von-Mises stress at nozzle-vessel intersection isincreasing abrouptly as thickness is reducing. Particularly at 5.65mm thickness the vessel willfail at interection because stress is higher than allowable limits. So slight modification ismade in the original design i.e. provision of reinforcement pad at vessel-nozzle intersection.Providing the reinforcement pad has reduced stress which are below allowable limits. Theresults of the ANSYS were compared with experimental values which are in good agreement.ACKNOWLEDGEMENT We sincerely thank Mr.V.G.Patil for his continuous support in providing advances inPressure Vessel analysis technology and for guidance to prepare this paper. We also thank histeam of Vaftsy Engineering Services Ltd. Pune for providing testing facilities and inputs tocomplete the content of this research topic.X. REFERENCES [1] H. Darijani, M. H. Kargarnovin, R. Naghbadi (2009), “ Design of Spherical vessels understeady state thermal loading using Thermo elastic plastic concept”, International Journal ofVessels and Piping, Electronic Publication: Digital Object Identifiers (DOIs), Pp 619-624.[2] Donald Mackenzie, Duncan Camilleri, Robert Hamilton (2008), “Design by analysis ofductile failure and buckling in Toro spherical pressure vessel heads”. International Journal ofthick walled cylinders, Pp 963-974.[3] Thanh Ngoc Tran (2007), “Calculation of load carrying capacity of shell structures withelasto plastic material by direct approach”, International conference of material theory andnon linear dynamics, Pp 24-26.[4] Josef L. Zeman (2006), “Franz Rauscher and Sebastian Schindler,’ Pressure VesselDesign- The Direct Route”, Elsevier Publications Ltd.[5] Rolf Sandstram, Peter Langenberg, Henrik Sieurin (2005), “Analysis of the brittle fractureavoidance model for pressure vessels in European Standard”, International Journal Ofpressure Vessel and piping, Pp 872-881. 688
  8. 8. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME[6] Ho-Sung Lee, Jong-Hoon Yoon, Jae-Sung Park, Yeong-Moo Yi (2005), “A Study onFailure Characteristics of Spherical Pressure Vessel”, Journal of Materials ProcessingTechnology, Pp 882-888[7] You-Hong Liu (2004), “Limit pressure and design criterion of cylindrical pressure vesselwith nozzles”, International Journal of pressure Vessels and Piping, Pp 619-624.[8] A. Th. Diamantoudis, Th. Kermanidis. (2004), “Design By Analysis versus Design byFormula Of High Strength Steel Pressure Vessels, A Comparative Study”, InternationalJournal of Vessels and Piping, Pp 143-152.[9] Yukio Tachibana,Shigeaki Nakagawa,Tatsuo Iyoku(2004), “Reactor pressure Vesseldesign of the high temperature engineering reactor”, International journal of NuclearEngineering and design, Pp 103-112.[10] Imran M.Jamadar, Prof.R.M.Tayade, Mr.Vinay Patil (2012), “Structural Analysis ofInclined Pressure vessel Using FEM”, International Journal of Engineering Research &Technology (IJERT), ISSN: 2278-0181, Vol. 1 Issue 3, Pp. 1-5.[11] Dennis R. Moss (2004), Pressure Vessel Design Manual-Third Edition, GulfProfessional Publishing.[12] Clifford Matthews (2001), Engineers Guide to Pressure Equipment ProfessionalEngineering Publishing Limited, London and Bury St Edmunds, UK.[13] James R.Farr,Maan H. Jawad, “Guide Book For the design of ASME Section VIIIPressure Vessels” Second Edition.[14] Matin Kagadi, Prof. Girish Tembhare1, Vinaay Patil, Sujay Shelke (2012),“Optimization of Self Activating Bi-Metallic Valve using Thermo–Structural Coupled FEA”,transtech publication inc, publishers in science and engineering, Pp.147-151.[15] T.Vishnuvardhan and Dr.B.Durga Prasad, “Finite Element Analysis and Experimental Investigations on Small Size Wind Turbine Blades” International Journal of Mechanical Engineering & Technology (IJMET), Volume3, Issue3, 2012, pp. 493 - 503, Published by IAEME[16] Mane S.S and Prof. Wankhede P.A, “The Design of Vertical Pressure Vessels Subjected To Applied Forces and Vibrational Conditions” International Journal of Mechanical Engineering & Technology (IJMET), Volume3, Issue2, 2012, pp. 38 - 45, Published by IAEME[17] Manikandapirapu P.K, Srinivasa G.R, Sudhakar K.G and Madhu D., “Comparative Analysis Of Pressure Measurements In Ducted Axial Fan” International Journal of Mechanical Engineering & Technology (IJMET), Volume3, Issue2, 2012, pp. 85 - 91, Published by IAEME[18] Dr.R.Uday Kumar and Dr.P.Ravinder Reddy, “Influence of Viscosity on Fluid Pressure in Hydroforming Deep Drawing Process” International Journal of Mechanical Engineering & Technology (IJMET), Volume3, Issue2, 2012, pp. 604 - 609, Published by IAEME[19] Ayub A. Miraje and Dr. Sunil A. Patil, “Infinite Fatigue Life Of Three Layer Shrink Fitted Compound Cylinder Under Fluctuating Internal Pressure” International Journal of Mechanical Engineering & Technology (IJMET), Volume3, Issue1, 2012, pp. 288 - 299, Published by IAEME 689

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