Design of Obround Flange for Pressure Vessel Application by Analytical Method and FEA to Comply with ASME code

Mechanical Engineering

Flanged joints are essential components in nearly all pressurized systems and piping; however they constitute one of the most complex parts of design. A wrong design can lead to major leakage, affect the system performance and can be hazardous for operators. Various factors influence the successful design and operation of a flange joint in service. The bolted flange joint involves interaction between bolting, flange, and gasket. For various industrial applications such as vapour absorption chillers, unfired pressure vessels having flange size more than 600 mm; there is a need of non-circular flanges having reduced heights than traditional flanges. The shape considered for flange (Slip-on type without hub) is obround shape; whose investigation involves finding an appropriate analytical method to be used for design of this obround flange and which can also comply with ASME code. This obround flange subjected to internal pressure is designed using equivalent circular flange method. The finite element analysis (FEA) is used to predict levels of stress and deformation of a particular flange and stresses are linearized for stress categorization. These FEA results are compared with ASME allowable limit and are on safe side. The analytical design method is approximate method and results on positive error side. For selected application; there is 22% reduction in height observed with the use of obround flange.

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