Pressure Vessel Design by Design by Analysis Route

Abstract

Pressure vessels are conventionally designed based on the Design by Rule (DBR) approach. Standard vessel geometries are designed using simple formulae and charts, formulated as standards and codes based on the rules proposed in the ASME Boiler and Pressure Vessel Code and the European Standard prEN13445-3. The stress categorization problem faced employing DBR methodology was overcome by employing Limit Load Analysis using the DBA approach. A simple unfired vertical cylindrical pressure vessel with torispherical pressure head and Y-forged skirt support was analyzed for its structural integrity using ANSYS software. The results obtained for two different materials, high strength steel P500-QT and the conventional low strength steel P355 employing DBA approach was compared with the calculated results using the DBR approach. The maximum allowable pressure (PMAX) for P500-QT material was found to be 2.5X the maximum pressure calculated using the DBR approach as per ASME codes and 3X times as per EN13445-3 standard. For P355 material the maximum allowable pressure (PMAX) was found to be 2.32X the maximum pressure calculated using the DBR approach as per ASME codes and 2.6X times as per EN13445-3. The DBR methodology proves to be highly conservative whereas the use of DBA leads to less conservative design parameters.