Plants in safety-critical industries comprise of a number of different components, including various sizes of pressure vessels, and their integrity is often paramount to the safe running of the plant. In many cases these vessels can contain highly corrosive liquids, which, over time can lead to a degree of thinning in the vessel walls. With corrosion wall-thinning come a number of issues, including a reduced plastic collapse load of the vessel and possible fatigue initiation from corrosion pits. Since failure of these vessels could lead to catastrophic failure and the escape of highly corrosive material, the assessment and maintenance of these vessels 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, with respect to plastic collapse. This guidance, however, is not currently applicable to components with geometric discontinuities (the pressure vessel base-wall junction).
This paper follows a preceding paper presented at the ASME PVP Conference 2010 which derived “First Estimate” plastic collapse solutions for flat-based, corroded, pressure vessels. These solutions have been expanded through further finite element studies to accommodate the estimation of plastic collapse in tori-spherical headed pressure vessels subjected to extensive corrosion wall-thinning. Results from this study are presented in graphical form to enable a quick and efficient first estimate of the effect of wall thinning on the collapse pressure to be attained.
