Optimal characterisation of weld lines and valve locations in a thin-walled cylindrical pressure vessel using finite element analysis

This paper addresses the critical problem of optimizing weld geometry and valve location in pressure vessel to minimize stress concentration and enhance structural integrity. The study focuses on a thin-walled pressure vessel with a cylindrical body and a spherical head, analysing how different weld and valve configurations impact the stress distribution. The design adheres to the ASME Boiler and Pressure Vessel Code IX, with steel as the base material and EX80XX for the welds. The objectives are to identify the safest weld arrangement and the optimal valve location to reduce structural risks. A combination of theoretical stress analysis and Finite Element Analysis (FEA) was used to evaluate the pressure vessel under a uniform internal pressure of 2 MPa. The study investigated seven valve positions and four weld lines arrangement. Results show that placing the valve at the centre of the spherical head minimizes the stress concentration, while the safest weld configuration is a single weld line at the interface between the cylindrical and the spherical sections. The study further explores the combined effects of multiple valves and weld lines, concluding that placing valves and welds in the cylindrical section increases structural risk compared to the spherical section. This research offers novel insights into the design of pressure vessel, offering optimal weld and valve configurations to enhance safety and performance. Keywords: pressure vessel; optimal design; weld lines; valve location; finite element analysis