Non-destructive Pipe Condition Assessment and Case Studies

US EPA reports that there are over 240,000 water main breaks and up to 75,000 sanitary sewer overflows per year in the United States. The number of failures has also been increasing as the systems approaching their service life. Effective management is required to extend the lives of the pipelines, and to ensure the public health and safety. An effective assets management plan, in turn, requires proper pipe condition assessment. Methods are very limited to assess the corrosion condition of metal pipelines buried underground without interrupting services or excavating. This paper presents a synergistic non-destructive method to assess the condition of underground metal pipelines following by case studies.

This non-destructive method synthesizes the environmental condition with the pipe-to-soil potential data. The environmental information includes soil condition and stray currents. Soil resistivity and soil pH are surrogate parameters for the corrosivity of the soil environment. And the presence of much stray current is an indicator of corrosion activities. The soil and stray current information supplement the pipe-to-soil potential data. Pipe-to-soil potentials are measured with two Cu-CuSO₄ half cells by following a cell-to-cell protocol. By comparing the readings of the two half cells, actively corroding areas (anodic) can be identified.

This synergistic assessment method has been shown to accurately locate corroding pipes. A case study is presented in this paper. Over the summer of 2010, 140,000 ft of sewer forced pipelines (Cast Iron, Ductile Iron) were surveyed to assess their corrosion condition. Test pits samples are scheduled to be collected by July, 2011. The results of the pipe condition assessment can then be correlated with the test pits and the pipe failure history to validate the effectiveness of this pipe condition assessment method.