Investigation of optimal thermal injection conditions and the capability of IR thermography for detecting wall-thinning defects in small-diameter piping components

In this study, optimal thermal injection conditions and the detection capability of infrared (IR) thermography were investigated to confirm the applicability of active IR thermography for detecting wall-thinning defects in small-diameter nuclear piping components. IR thermography tests were conducted on pipe specimens, including elbow specimens, with artificial wall-thinning defects. Each specimen was thermally activated using two halogen lamps, and thermal images were captured via an IR camera. The thermal injection conditions that provided the best images of defects were dependent on the pipe diameter; the smaller the pipe diameter, the shorter the optimal object distance. Under the optimal conditions, active IR thermography was able to detect all wall-thinning defects with depth d/t ≥ 0.5 in a 500 mm specimen of pipe at one time, except for the defects with very short and narrow. However, wall-thinning defects with depth d/t = 0.25 could only be detected when they had suitable lengths and circumferential angles.