Fatigue Analysis and Optimization of an Agitator Vessel with Ellipsoidal Head

Abstract

The design of pressure vessel is usually made with external attachments and requires openings. The most commonly used external attachment are the nozzles with their junctions. Under different loading conditions the stress concentration will occur at the junction area. In addition, due to discontinuity of the geometry and difficulties during welding and defect detected there, the junction region will become the weakest point and the failure source of the whole structure. Apart from that when external parts like agitator is connected to the vessel it is prone to fatigue failure as well. So, the design of vessel based on ASME pressure vessel design code is very necessary. This dissertation illustrates the Design of Ellipsoidal head of pressure vessel with agitator nozzle attached to it for certain loading condition. Design calculations of Nozzle made in ellipsoidal head are as per ASME pressure vessel design code SEC VIII DIV I in PVElite software and WRC (Welding research Council) calculations are also carried out for the loading conditions. Three-dimensional model of the vessel nozzle junction is created using ANSYS Workbench. Structural analysis is carried out for nozzle with agitator on 2:1 Ellipsoidal head with 883.9 mm inside diameter subjected to internal pressure loading as well as external loads and fatigue life is calculated for the same. The result illustrates that the design passes under given loading condition and further improvement is possible. Hence, Optimization of the design for 1011 life cycles is carried out through analysis. It is suggested to approve the final design for further consideration by the organization.