Using the digitized images to estimate thickness and corrosion of pipes

Piping is the most important means of transporting liquid and gaseous substances in many industries. They are subjects to deterioration caused by corrosion. To monitor the corrosion, pitting and deposit of insulated pipes, the radiographic technique has the advantages over other NDT techniques in term not removing the insulated material. In this report, two specific radiographic techniques - Tangential Radiographic Technique (TRT) and Density Measurement Technique (DMT) were investigated to estimate the capabilities and accuracy of measurements due to small change to thickness and deterioration of the pipe samples with outside diameter 1 - 4 inch. The results shown that those specific techniques can be used to detect internal and external pits and to measure their depths and to measure the remaining pipe thickness without removing its insulation material in practical with a reasonable degree of accuracy less than 1 mm, specially can be better than 0.5 mm in some case. The outlines of two specific radiographic techniques and the use of film image digital processing to improve their performance and provide accurate interpretation also are described. (author)