Welded Joint Analyses for Pressure Vessels with Medium and Large Diameters

Welded seal joints are recommended for applications where leak proof conditions are necessary and also when the disassembly of the closure parts is not required. Normally, for pressure vessels of medium and large diameters, the relative movements between parts of the joint is considerable due to the different movements of the individual parts or different thermal expansion coefficients. The use of weld ring gaskets with hollow lips, recommended for these type of vessels offers improved stress conditions in the seal weld. However, the construction of these joints using standard gaskets is complicated because the diameters and the configurations of hollow lips are limited. Special fabrication by the suppliers is often very expensive. In this paper, the author proposes the fabrication of hollow lips welded ring joints with a simple method by machining, allowing the designer to select the most appropriate configuration of the joint. The design of the welded ring shall be sufficient to resist the internal pressure and the deflection due to the movements of the flanges. The ANSYS program is used to obtain the optimum parameters of the seal ring. Through several iterations with ANSYS, the author can select the correct diameter and thickness of the seal ring in order to keep the resulting stresses under the specified limits. An example of welded joint ring will be analysed in this paper by the finite element method using the ANSYS program and nonlinear elements.

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