Prediction of Asbestos Cement Water Pipe Aging and Pipe Prioritization Using Monte Carlo Simulation

Abstract

For buried Asbestos cement (AC) pipes in service, internal and external surface degradation occur by dissolution or leaching of cement-based components leading to loss of pipe strength. Since water quality and soil environment cannot be completely specified along a pipeline, a management methodology for AC water pipelines is required to estimate the probability of pipe failure as ageing proceeds. The paper describes the technique and its application to experimental data, which illustrates in three parts. First, the degradation rates in AC pipes are computed from 360 aggregated independent pipe segments residual strength test data taken from different pipe diameter sizes used in various water utilities locations in Thailand. Second, the predictions of service lifetime for AC pipes are estimated using Monte Carlo simulation in conjunction with the physical failure state formulations. Output from the simulation provides a number of failures recorded over time, which then allows the economic analysis for optimal pipe replacement scheduling. All is described in the third part. The end results can be used for water utilities to allocate government funds for future pipe maintenance activities.

Improving pipe failure predictions: Factors affecting pipe failure in drinking water networks

“…Two main types of concrete corrosion occur in AC pipes: 1) lime leaching and 2) sulphate attack (Hu et al, 2013). Early AC pipes were manufactured using free lime, which was susceptible to lime leaching in certain soil conditions, being particularly evident when silica was not used (Punurai and Davis, 2017). Lime leaching occurs when external pipe conditions are acidic with a low ion content mobile water source (typically a high groundwater level) (Hu et al, 2013;Silva et al, 2002).…”

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“…3 allows the Weibull scale and shape parameters to be estimated and reported together with strength loss rate values. Following the procedure outlined in [27], the scale and shape parameters for different pipe sizes were calculated and shown in Table 4. Fig.…”

CT Scans of Asbestos Cement Pipes as a Reference for Condition Assessment of Water Mains

“…In previous work, it was determined that X-ray computed tomography may indeed provide a detailed description of AC pipe degradation [15]. In that work, it was also revealed that the leaching of AC drinking water pipes occurs in a far less homogeneous way than is traditionally assumed [16][17][18].…”