Processing laser range image for the investigation on the long-term performance of ductile iron pipe

Prediction of service life of ductile iron pipe is carried out using the information on pipe condition, backfill/soil properties, and corrosion rates, as well as historical failure records. Among the factors that affect pipe condition, external pitting corrosion is a prominent variable contributing to the disintegrity of the pipe. A pipe scanner equipped with a laser displacement sensor was used to measure pitting corrosion. The pipe scanner can generate an accurate topographic mapping of the outer surface of the pipe. In order to accelerate the scanning process, a scan with reduced resolution is preferred. An image of higher resolution can be obtained with interpolation methods afterwards. Different interpolation methods are compared in term of the accuracy. To establish the statistical model, we need to identify and characterize each corroded area from the scanned laser range images. Quantitative description of the corroded areas, such as size, percentage of material loss, and location, needs to be generated and kept in a database for modeling and prediction purpose. This paper describes the procedure to carry out the process of the laser scan of ductile iron pipe.