Evaluation Diagnosis of Water Distribution Pipeline Utilizing Inspection Results of In-Pipe Endoscope Camera

"Maintenance of water pipelines has emerged as an important issue over the recent years. Usually, pipelines are buried in the ground, so directly observing the state of their degradation is difficult. Thus, the condition of the pipeline only becomes apparent after a water quality or leakage accident occurs. To mitigate this, an in-pipe endoscope camera system can be used; it is one of the only few nondestructive methods that can be used to directly diagnose the condition of a buried pipeline. In Japan, its use regardless of large and small water supply utilities is increasing every year. Currently, in-pipe endoscope camera inspection is mostly used as a countermeasure after accidents that affect water quality. However, the number of aged pipes and hence water quality accidents are expected to increase in the future, which may lead to residents' distrust of the water quality. In this study, we analyzed the images of the inside of the pipes taken from the endoscope camera inspections, and we assigned scores in each pipes of the five categories: “rust condition of the pipe inner face”, “condition of sticking dirt on the pipe inner face”, “corrosive condition of the pipe inner”, “condition of suspended matter”, and “condition of sediment inner the pipe”. And we surveyed the data obtained from the endoscope camera inspections conducted from 2001 to 2011 wherein the objective function are the evaluation results based on the endoscope camera inspections and the explanatory function are based on parameters related to the parts, such as coating specifications of the pipe inner face, elapsed years, and diameter. A discriminant analysis was conducted using the Hayashi's second method of quantification (discriminant analysis of categorical variables). The analysis revealed a very high rate of correct classifications (80.0%). Through these analyses, the state of the pipe inner face could be determined based on the history of the pipeline. Therefore, we consider that water endoscope camera inspection can be used as preventive maintenance measures against accidents affecting water quality."