Structural evaluation of localized pipe thinning caused by erosion/corrosion

The recent pipe ruptures in high-energy lines due to erosion/corrosion (E/C) of pipe walls have accelerated the industry effort to understand the mechanism of E/C, identify potential locations of E/C, carry out inspections of piping components, perform evaluations of piping components, and repair/replace piping components as required. The mechanism of corrosion combined with erosion is complex. The potential location for E/C inspection should take into consideration water chemistry, operating temperature, flow velocity, moisture content, piping material composition, and piping geometry. Once the inspection locations have been identified and the extent of wall thinning determined, the next step is to evaluate the effect of the wall thinning on the structural integrity of the piping system. Simple analytical expressions are derived and results presented in tabular form, which can be directly utilized for evaluating longitudinal stresses in pipes with localized thinning. A simple multiplying factor can be directly utilized in an equation for design by rule. Results of the analysis clearly indicate the degree of localized thinning of pipe, which should not be of significant concern as far as longitudinal stresses are concerned.