Condition Assessment of Cast Iron and Asbestos Cement Pipes by In-Pipe Probes and Selective Sampling for Estimation of Remaining Life

摘要

In the present climate of economic constraints and regulatory compliance water authorities require proactivernmaintenance strategies to remain competitive. Whilst trenchless rehabilitation is essential to deliver thesernoutcomes, the ability to map the condition and estimate the remaining life of pipelines is a key prerequisiternfor the decisions. This paper discusses the research and development of tools that are necessary to applyrncondition assessment to cast iron and asbestos-cement pipelines, which comprise the majority of Australianrnwater distribution networks. In many cases, these pipes are past or rapidly approaching their design life.rnCharacterisation of pipe wall properties and surrounding soil strata is the minimum requirement for pipelinerncondition assessment and estimation of remaining life. One technique currently being optimised that allowsrnassessment of some of these critical properties is a Remote Field Eddy Current (RFEC) tool, which isrnapplied for wall thickness measurements in cast iron pipe. Other methods for wall thickness assessment ofrnmetallic and cementitious pipes are based on transient electromagnetic (TEM) concepts, electron probesrnand moisture density probes. These techniques are also being developed and evaluated as to their suitabilityrnin assessing both pipe wall and embedment condition. To allow the full use of wall condition information,rnmodels are being constructed relating failure probability to residual wall thickness, operating pressure, andrnsoil loading stresses. A more direct approach being developed for obtaining data for condition assessment ofrnpipe wall and soil bedding is ‘keyhole’ sampling. This method is particularly useful for cementitious pipesrnwhere the success of electromagnetic methods is limited. In conjunction with a model based on residualrnpipe strength, keyhole sampling has allowed failure prediction of cementitious pipes under various operatingrnand installation conditions.