SI routinely conducts analysis of pressure vessels, piping, valves and other components with degraded wall thickness. Through evaluation of the mechanism, rate of wall thinning, and the required local wall thickness to meet Code requirements, continued operation may be justified when wall thickness degradation is observed.

SI has been a leader in developing methods for evaluating wall thinning. The evaluation methods in ASME Section XI Code Cases N-480, N-513 and N-597 stemmed from work conducted for EPRI. The approaches contained therein were based on our understanding of ASME Code criteria and intent for wall thickness and applied component loadings. As a result, local thinning well below the general minimum wall thickness required by the Code may be justified.

Where simplified analytical methods such as in the above Code Cases cannot show acceptability, finite element models are developed to determine local stress distributions in thinned components. In situations with local through-wall leakage, fracture mechanics analysis can be conducted to show that there is sufficient margin against fracture should there be a crack-like opening in the component wall. Because of our expertise in finite element analysis and fracture mechanics, these evaluations can be turned around very rapidly, allowing rapid run/repair/replace decisions to be made during plant outage conditions. Wall thinning evaluations can also be performed as part of a Life Cycle Management program.