Joint design efficiency, methods

The ASME design formula from UG-34 for circular flat heads subjected to internal pressure is t = d CP/SEf, where t is the minimum thickness of the head (in.), d is the internal diameter of the vessel (in.), P is the MAWP (psi), S is the allowable stress in the material listed in ASME Section II, and E is the weld joint efficiency. The value of C ranges from 0.10 to 0.75 depending on the method of attachment of the head and the shell dimensions. For preliminary designs, a value of 0.33 for C will lead to a good approximation of the required head thickness. 

Sound knowledge of the joint behavior is required for a successful design of bonded joints. To characterize the bonded joint, the loading in the joint and the mechanical properties of the substrates and of the adhesives must be properly defined. The behavior of the bonded joint is investigated by finite element (FE) analysis methods. While for the design of large structures a cost-efficient modeling method is necessary, the nonlinear finite element methods with a hyperelastic material model are required for the detailed joint analysis. Our experience of joint analysis is presented below, and compared with test results for mass transportation applications. 

The value of t, obtained from any of the methods given above is used only to determine the required area of reinforcement. The value of tr used to set the minimum required thickness of the shell or head is based on the thickness formulas that consider aU the design loadings and weld joint efficiencies. 

This book also takes into account Billet s [15] experimental data on the hydraulic behaviour of packed columns for the development of a new method for the standard presentation of the fluid dynamics of columns with any type of packing design. The basic principles of the method for determining the separation efficiencies of packed columns have already been publicised in joint presentations and individual publications by the author and Billet [16-18]. 

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