Simplification of the estimation method of wall thinning at the T tube junction in an actual plant

Abstract

Flow-Accelerated Corrosion (FAC) is a pipe wall thinning phenomenon to be monitored and managed in the power plants with high priority. Its management has been conducted with conservative evaluation of thinning rate and residual lifetime of piping based on wall thickness measurements. However, in the actual plants, noticeable case of the wall thinning occurred in branch and junction piping (T tube). There is a problem to manage the wall thickness of the part covered by reinforcing plate of the T tube, because measurement of this area is difficult to be conducted with ordinary ultrasonic testing devices due to the presence of the reinforcing plate. Our previous studies have developed methods for estimating wall thinning in areas where it is difficult to measure pipe wall thickness. The validity of this method was verified by actual plant data. However, considering its application to a new plant, this method may result in overly conservative evaluation results. Therefore, this study examines a simpler method for estimating wall thinning, including the handling of correction values for the estimated evaluation equation.