Optimal Design and Structural Analysis of Internally Pressurized Thin-Walled Shells

Abstract

The objective of this study is to utilize nonlinear constrained optimization to optimally design and analyze the features of an internally pressurized thin-walled shell for mini liquefied petroleum gas storage and transportation. Computer aided tools was utilised to minimize the materials selection information overload and then finite element analysis of the pressure vessels was undertaken for different shell profile. From the results maximum von-misses stresses of 1.7017E9 Pa was recorded for horizontal oval vessel made with low alloy steel and this is above the yield strength of low alloy steel, however, the lowest von Mises stress of 2.2749E8Pa was recorded for cylindrical vessel. Minimization of cost showed that the shell manufacturing cost for low alloy steel is reduced from NGN 311186.5 to NGN 232848.9 because of the smaller volume using optimal dimensions of D = 2.5m and L = 5.09294m.. Distortion Energy Theory (DET) gave the smallest shell thickness of 3.678mm for low alloy steel. Various parameters of pressure vessel were designed and checked according to the principles specified in American Society of Mechanical Engineers (A.S.M.E) Section VIII Division 1. The use of low alloy steel is therefore recommended for cylindrical vessels of Liquefied Petroleum Gas Storage tanks.

Keywords: FEM, Shell, Pressure Vessel, Crack Size, Fracture Toughness, Vessel Thickness