Design by analysis using the elastic approach

Abstract

Pressure vessels are very important components which play a critical role in the manufacturing, processing, and servicing industry. Pressure vessels are utilised to safely store liquids and gases under pressure. Therefore, it is essential that such components can withstand the design loads and temperatures to which they are subjected. Before the recent advancements in computer power, pressure vessels were designed using Design by Rule (DBR). However, due to this advancement in computer power, it is now possible to design, model and certify pressure vessels using finite element tools. Nowadays, finite element tools are used along with codes and standards which are provided by international agencies. These codes and standards outline various limit values for various parameters such as maximum operating temperatures, pressures, and stresses. Such parameters must be carefully analysed by engineers to make sure a component is safe to be used in industry. This thesis presents the process of using Annex C- Design by Analysis - Method based on stress categories of the EN 13445-3 standard. The annex was used alongside a finite element model of a process pressure vessel which was created using ANSYS Workbench. The method based on stress categories was used with the aim to verify the validity of the design obtained from DBR results. The pressure vessel consists of various components whose thicknesses are based solely on pressure loading. Therefore, the goal was achieved by firstly, splitting the pressure vessel into separate components. Furthermore, the process of stress categorisation was performed on each component area. Stress categorisation was done to specify various stress limits for each component and component area whilst abiding by Annex C of the standard. Once the results were obtained, an analysis was performed to understand the response of the pressure vessel structure to the loading. Furthermore, the analysis was used to identify different locations along the vessel which had failed due to stresses which exceeded the limit values outlined in the standard. These failed locations were highlighted and various improvements were suggested to optimise the design of the pressure vessel. The final product is a pressure vessel design which is safer and more reliable.