Strain Distribution Measurement for Wall Thinning Defect in Pipe Bends by ESPI

The strain distribution measurement for wall thinned pipe bends by ESPI is presented. Defect types observed in the steel piping in the Nuclear Power Plants (NPP) are the crack at the weld part and the wall thinning defect in the pipe bends. Especially, the wall thinning defects in the pipe bends due to the Flow-Accelerated Corrosion (FAC) is a main type of defects observed in the carbon steel piping system. ESPI is one of the optical non-destructive testing methods and can measure the stress and the strain distribution of the object subjected by the tensile loading or the internal pressure. In this paper, the strain distribution of the wall thinned pipe bends due to the internal pressure will be measured by ESPI technique and the results are discussed. From the results, the size of the wall thinning defect can also be measured approximately