Asset management: Quantifying economic lifetime of large‐diameter pipelines

Large‐diameter water mains have relatively low failure rates, but significant costs can result when failures do occur. Although economic analyses to schedule water main replacements are available, they rely on historical failure data. In many cases, however, large‐diameter mains do not have sufficient failure data to enable confident application of these methods. As an alternative, water authorities can inspect pipes to determine structural condition and assess the need for and timing of future inspections and replacement. Because asset failure depends on a range of factors, however, inspection data alone cannot fully support this type of decision‐making. This article describes a methodology that combines asset condition with a physical probabilistic failure model to determine the lifetime of a large‐diameter cast‐iron pipeline. Net present value calculations are used to determine the timing of future inspections and replacement of the entire pipeline. The authors also present a case study that illustrates the use of the proposed methodology.