'First Estimate' Solutions for the Plastic Collapse Pressure of Pressure Vessels Subjected to Extensive Corrosion Wall Thinning

摘要

Pressure vessels are commonly used in the operation of plant in many industries including the nuclear and their integrity is often paramount to the safe running of the operations. In many cases these vessels can contain highly corrosive liquids, which, over time can lead to a degree of thinning in the vessel walls. Since failure of these vessels could lead to the escape of highly corrosive material the assessment and maintenance of them is of high importance. Current Fitness for Service Codes and Standards provide guidance on the assessment of cylinders and pipes with localized wall thinning and general corrosion. This guidance, however, is not currently applicable to components with geometric discontinuities (a pressure vessel base-wall junction). This paper presents a "First Estimate" Solution for the collapse of flat bottomed vessels subjected to extensive corrosion wall thinning in the lower regionsof such components, and provides guidance on the conservatism of the solution, suggesting improvements where possible. The solutions have been derived from a series of axi-symmetric finite element analyses. Collapse results are presented in graphical form to enable a quick first estimate of the effect of wall thinning on the collapse pressure to be carried out. Results from this study can be used to enable the development of the solution to include more complex tori-spherical geometries.