A preliminary study on pipe wall thinning of metallic underground utilities using inpipe infrared thermography

Underground utilities are often prone to damage due to aging and external factors in which external corrosion has been reported as the main reason for pipe failure. Thus, obtaining the thickness of the pipe wall of the existing pipeline is crucial to prevent pipe failure. This study assesses the thermal signature of wall thinning in ductile iron pipes due to elevated temperature at reduced path length (or pipe wall thickness) of thermal transfer. It is a common problem that is caused by external corrosion in hostile underground environment. A new ductile iron pipe was prepared by milling several thinned regions of various sizes, shapes, and residual thicknesses onto the external wall. Wall thinning was investigated by infrared thermography using hot air as a heat source with the aid of visual images. Infrared and visual images of the inner pipe wall during a 2-minute heating phase were captured at a frequency of 9 Hz. While pipe interior surface feature could be eliminated by its sharp thermal response, thinned area generally has blurry boundary with a 0.5 ºC temperature contrast with the sounded region. Therefore, a rapid condition assessment using infrared thermography for buried metal pipelines is successfully demonstrated.