Ultrasonic technique for measuring the thickness of scale on the inner surfaces of pipes

At the present time, there are no known commercialized nondestructive techniques for measuring or detecting the scale on the inner surfaces of pipes in situ. The present study aims to develop an ultrasonic technique for measuring the thickness of scale on the inner surfaces of pipes in situ. All experiments were carried out under laboratory conditions by using three pipe samples with scale (HNO3). The pipe samples were made of polypropylene (PP), polyvinyl chloride (PVC), and steel, respectively. The ultrasonic technique developed in the present study was successfully applied to determine the scale thicknesses of the PP and the PVC pipes whereas it was not applicable to the steel pipe. It is expected that a predetermined graph for a particular type of scale, relating the scale thickness to the time of flight of a pulse within the scale, can be used in further testing, thereby eliminating the need for future destructive inspections.