International Journal of Engineering and Techniques - Volume 2 Issue 1, Jan - Feb 2016

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1 RESEARCH ARTICLE OPEN ACCESS A Study and Analysis of Sealing Performance of Bolted Flange Jointwith Gaskets using Finite Element Analysis Wasim B. Patel 1,Ritesh G. Deokar 2,Pundlik N. Patil 3,Raghunath Y. Patil 4, 1*(PG Scholar, Department of Mechanical Engineering, SGDCOE,North Maharashtra University, Jalgaon.) 2 (UG Scholar, Department of Mechanical Engineering, MIT, Savitribai Phule Pune University, Pune.) 3,4 (Asso. Prof. Department of Mechanical Engineering, SGDCOE, North Maharashtra University, Jalgaon) Abstract: Gaskets in joints play an important role in the sealing performance of bolted flange joints, and their behavior is complex due to nonlinear material properties combined with permanent deformation. The variation of contact stresses due to the pressure of the flange and the material properties of the gasket play important roles in achieving a leak proof joint. In this paper, a three-dimensional finite element analysis (FEA) of bolted flange joints has been carried out by taking experimentally obtained loading and unloading characteristics of the gaskets for various thicknesses and loads. Analysis shows that the distribution of contact stress has a more dominant effect on sealing performance than the limit on flange rotation specified by ASME. Keywords Bolted Flanged joints,gaskets,fea,von-misses stresses. I. INTRODUCTION Due to simple dismounting bolted flanged joints are the most popular means of connecting piping systems and pressure vessels containing fluid or gas under pressure. Although this type of connection is practical in terms of disassembly, it is a source of potential leakage failure especially when operating under high pressures and temperatures. A gasket is used to create and retain a static seal between two stationary flanges, which connect series of mechanical assemblies in an operating plant, containing a wide variety of fluids. These static seals aim to provide a complete physical barrier against the fluid contained within, and so block any potential leakage path. To achieve this, the gasket must be able to flow into (and fill) any irregularities in the mating surfaces being sealed, while at the same time be sufficiently resilient to resist extrusion and creep under operating conditions. The seal is affected by the action of force upon the gasket surface, which compresses the gasket, causing it to flow into any flange imperfections. A.The modern sealing challenge Historically, compressed asbestos fiber sheet material has been the material of choice for "soft" gasket materials. It was regarded as easy to use and very tolerant of abuse, for which it was recognized as very "forgiving". Consequently, the material was used to seal almost all common applications, and usually gave reasonable performance. A broad experience of the material was established over many years amongst manufacturers and users alike. Similarly, testing specifications for traditional soft gasket materials were intended for application to asbestos-based materials where there was a large area which indicated that such materials would perform satisfactorily in service, provided that they were manufactured under an appropriate level of quality control. some of the properties measured by such quality control tests were of direct functional importance. Rather, they provided assurance that the current batch was similar to its predecessors in composition and therefore, by implication, in performance. II. METHODOLOGY To carried out the comparative analysis of contact stresses between the joint by experimentally and by FEM,following are the steps to be followed out: Step 1. The detailed FEM model of the single bolt joint is built, completely reflecting geometry of the bolt and fragment of the flange. Contact interactions between elements are taken into ISSN: Page 46

2 consideration in the model, the friction on the thread and the elastic-plastic model of the material included. Step 2. Parameters like loads, pressure of the equivalent bolt joint model are defined. Step 3. The global model of the flange joint is built with equivalent elements. Contact phenomena and Clamping force of the bolt joint are taken into consideration. Generalized sectional forces are assigned for individual bolts {F}, for representative sets of loads. Step 4. Generalized extreme sectional forces {F}max and{f}min are applied to the detailed model. Fields of stresses in the bolt joint are obtained from the performed calculations.tensors are determined: average stress, stress amplitude and stress range. Equivalent values: average stress,stress amplitude and stress range are calculated according to the Huber von Misses hypothesis Step 5.Final estimate of the flange joint. Fatigue analysis is carried out based on the previously determined values with numerical or classical methods or experimental method. percent of full-scale reading. If we required hydrostatic testing of carbon steel piping systems the test medium shall be potable water at ambient temperature with ph value between 6 and 7. In accordance with ASME B31.3 the minimum hydrostatic test pressure at any point in the systemshall be: a. 1.5 times the design pressure, or b. calculated in accordance with formula specified in ASME B31.3 if the design temperature is above the test temperature. IV. COMPUTATIONAL SETUP OF FINITE ELEMENT ANALYSIS III. EXPERIMENTAL SET UP Fig 2: Geometry with seal 5mm To validate the analytical model that estimates the relaxation of the bolt and the gasket, threedimensional numerical FE models were constructed on each of these assemblies in Ansys 14.0 which is a commercial structural analysis software based on the finite element technique, was used for this purpose. Because of symmetry with respect to the plane that passes through the gasket mid-thickness and evenly repeated loading in the angular direction, it is possible to model only an angular portion (Fig.) that includes half of the bolt and half of the gasket thickness. Fig 1: Experimental setup Equipment to be used during testing shall have suitable capacity for the range of test pressures required. Pressure indicators shall have a full-scale range between 110 percent and 150 percent of test pressure and an accuracy and sensitivity of 2 A. Mesh Generation The finite element meshes for flange and bolt were created with the help of Altair Hypermesh tool which is a Mechanical meshing tool. Since the geometries of theflange and bolt models are ISSN: Page 47

3 complex, an unstructured hexahedral-dominant techniquewas used to mesh. Hexahedral-dominant means that themeshing tool tries to create a mesh consisting of hexahedral elements. The single order hexahedron elements were generated with the help of Hypermesh tool with better element quality.a good quality element refers to an element that is not excessively distorted in shape. Element quality is determined by two factors: default shape checking metric; and the Jacobian ratio. The Jacobian ratio is used to map an ideal finite-element on to the real finiteelement. The Jacobian ratio is the ratio of the maximum determinant to the minimum determinant evaluated at these points and has a limit of 0.5.Both quality factors have a value of unity for an undistortedhexahedral element.to reduce distortion of the element in such instances, either the mesh can be refined, or another element shape that meets the shape checking criteria can be employed. Fig 4. Von-Misses stress contour plot Gasket 5mm Fig 5. Von-Misses stress contour plot Gasket 4mm Fig 3: Assembly Mesh V. RESULT AND DISCUSSIONS A. Stress Distribution in the gasket for three cases Fig 6. Von-Misses stress contour plot Gasket 3mm The 5 mm gasket shows maximum von-mises stress up to MPa which is under the limit of maximum allowable stress of 80 MPa. The 5 mm gasket is not yielding beyond allowable stress for ISSN: Page 48

4 applied loading scenario. The 4 mm gasket shows maximum von-mises stress upto MPa which is slightly greater than yield strength of the material. The 3 mm gasket shows maximum von-mises stress more than MPa which is more than the yield strength of the material. Therefore, the gasket is safe for first case (for 5 mm in size) in applied structural loading conditions. The stresses at flanges, bolt and nut where within limit. Therefore, 5mm thickness gasket is most suitable for the application. B. Maximum Displacement of Gasket The maximum displacement of the gasket observed due to compressive load of the flange upper and lower housing. The displacement contour plots are shown in the below figure. The gasket shows displacement up to 0.4 mm for 5 mm thickness. Fig 8: Deformation of Gasket - Thickness 5mm Fig 9: Deformation of Gasket - Thickness 4mm Fig 7. Maximum Displacement contour plot 5mm gasket Fig 10: Deformation of Gasket - Thickness 3mm C. Graphs ISSN: Page 49

5 D. Result table Sr. No. 1 Gasket 5mm 2 Gasket 5mm 3 Gasket 5mm TABLE I Description FEA Results Experimental Results Deflection (mm) Von- Misses stress (MPa) Defle ction (mm) Von- Misses stress (MPa) VI. CONCLUSION A finite element analysis was performed to investigate the leakage and structural integrity of the bolted flange joint assembly for the design conditions for bolt preload and internal pressure 69 MPa. The deformation of the flange and bolt was studied when subjected to these external loads. This deformation is responsible to induce the stresses in the gasket so that it may get compressed. I t was also determined that, the difference between FEA and experimental values are less than 10%. So, it is concluded that, the 5 mm thickness of the gasket is structurally safe to use in the flange and the bolt. The experimental and FEA results are reported in the table. The other parts in the assembly like flanges, nut and bolt exerts minimum stresses that are within yield strength (350 MPa) of the material. ACKNOWLEDGMENT The compilation of this paper would not have been possible without the support and guidance of Mr. P. N. Patil with my deep sense of gratitude. My deep and most sincere feeling of gratitude to the Head of Department Mr. R. Y. Patil who very kindly allowed me to work on this interesting topic. At last I am thankful to my Father, Mother and Brother for their valuable support to me for completion of paper. REFERENCES: 1. Tengjiao Lin, Runfang Li, H. Long, H. Ou,Three-dimensional transient sealing analysis of the bolted flange connections of reactor pressure vessel, Nuclear Engineering and Design 236 (2006) G. Mathan, N. Siva Prasad, Studies on gasketed flange joints under bending with anisotropic Hill plasticity model for gasket, International Journal of Pressure Vessels and Piping, 88 (2011) Nao-Aki Nodaa,, Akifumi Inoue, Masato Nagawa, Fumitaka Shiraishi, The effect of material difference and flange nominal size on the sealingperformance of new gasketless flanges, International Journal of Pressure Vessels and Piping 79, (2002) Jacky C. Prucz, Samir N. Shoukry, Sasikumar Chandramohan, Stephen Mitchell, An analytical model for interactive design of cylindricalcomposite ducts with upright bolted flanges, Composite Structures 61 (2003) Yu Luan,Zhen-QunGuan, Geng- DongCheng,SongLiu, A simplified nonlinear dynamic model for the analysis of pipe structures with bolted flange joints, Journal of Sound and Vibration,331 (2012) M. Murali Krishna, M.S. Shunmugam, N. Siva Prasad, A Study On The Sealing Performance Of Bolted Flange Jointswith Gaskets Using Finite Element Analysis, International Journal of Pressure Vessels and Piping -84,(2007) MasoudAsgari, AidinGhaznavi, Hamid Reza Lar, Finite Element Based Fatigue Analysis of Bolted joints in multi-megawatt windturbines Main Frame, ISBN: , page Muhammad Abid, YasirMehmoodKhan,AssemblyOfGasketed ISSN: Page 50

6 Bolted Flange Joints Using Torque Control Of Preload Method: FEAApproach. 9. Janko D. Jovanovic, Finite Element Analysis Of Bolted JointWith Coarse And Fine Threads, 14th International Research/Expert Conference-Trends in the Development of Machinery and Associated Technology, September 2010, page Maël COUCHAUX, Ivor RYAN, Mohammed HJIAJ, Stress Concentration Factors For The Fatigue Design Of Tubular Flange Connections, NSCC, 2009, page MaëlCouchaux, Mohammed Hjiaj, Ivor Ryan, Static Resistance Of Bolted Circular Flange Joints Under Tensile Force, 2010,The University of Hong Kong, ISBN Page AkliNechache, Abdel-Hakim Bouzid, Creep Analysis Of Bolted Flange Joints, International Journal Of Pressure Vessels And Piping 84,(2007) Mohsen Gerami, Hamid Saberi, VahidSaberi, Amir SaediDaryan, Cyclic behavior of bolted connections with different arrangement of bolts,journal of Constructional Steel Research- 67 (2011) ISSN: Page 51