Optimization of Elliptical Head Mass Subjected to External Pressure Using `Design by Analysis' Approach

Abstract

Pressure Vessels are the equipment which is widely used in process industries. The size of the pressure vessels depends upon its capacity and the process require- ment. The intermediate head is one of the critical components of the pressure vessel, which is widely used to combine two different vessels. The IM head is a critical com- ponent as it is exposed to two different pressure from the two sides of the pressure vessel. So it is required to analyze the design of IM head for internal pressure and the external pressure. It needs to analyze the IM head under buckling load. Usually, the design of the vessel, head and nozzles are carried out by the rules given in the ASME Section VIII Division 2 Part-4. The part-4 provides conventional methods to find out the parameters of the pressure vessel components. This leads to over design of the components considering the higher factor of safety. As per this guidelines, the thickness of the IM head is arrived at a higher value. However, this design doesn't ensure a high factor of safety in all cases. Hence an attempt is made to design the components using the "Design by Analysis" approach in accordance with part-4. Using this approach the IM head is optimized, to have weight reduction without compromising safety factor. For the IM head, linear Eigenvalue buckling analysis was carried out using FEA. It was proposed to incorporate stiffeners on the IM head. FEA was performed for various arrangements of stiffeners on the IM head. Buckling load factor was considered as a criterion for safety. With the circular stiffeners the weight of IM head is optimum (45 tonnes). The design factor is 18.9, which is higher than the minimum required buckling factor as per ASME guidelines. Keywords: Pressure vessel, IM Head, Optimization, Buckling, FEA.