Determining Effective Thickness of Cylinders in Pressure Equipment With Significant Thickness Variations for Fitness for Service Assessments

In many in-service issues involving pressure equipment, it is often the case that the thickness of a cylinder reveals significant variations in thickness around its cross section. This variation could represent loss of thickness due to corrosion or erosion, or could involve additions of thickness from repair activities. A common issue deals with determining the overall affect of such variations on the integrity of the vessel. This paper describes a spreadsheet tool employing common geometric properties such that these thickness variations may be simply reduced to an effective thickness of the cylinder cross section. This effective thickness may then be used for purposes of conducting fitness for service assessments or to assist in the planning of repairs. The use of this tool is illustrated with two case studies.