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A Strategy For Optimal Replacement Of Water Pipes Integrating Structural And Hydraulic Indicators Based On A Statistical Water Pipe Break Model

Leïla Dridi, Alain Mailhot, Marc Parizeau and Jean-Pierre Villeneuve

Abstract - The ageing of water networks results in an increase in water pipe breaks in addition to a decrease in hydraulic capacity. Considering the complexity of these processes combined with the huge investments municipalities will have to make to maintain an adequate service level, it is imperative to develop tools that will assist water supply utilities managers in selecting, among the available options, those that will minimize the total costs on the long term. This article presents a new strategy for the optimal replacement of water pipes. It integrates the two key elements involved in the deterioration of water supply services, namely the structural integrity and the hydraulic capacity. The objective function used to define optimal solutions comprises two terms: one related to repair costs and another to replacement costs. The optimal solution must minimize this function under the constraints that all node demands and pressure are satisfied. The model used to estimate the probability of pipe break occurrences considers time intervals between successive pipe breaks as a random variable described by probability density functions. A Bayesian approach is used to estimate the model parameters values. Network hydraulics are modeled using Epanet2.0, and a genetic algorithm (GA) is used to seek the optimal solution. The validation and the performance evaluation of the proposed strategy have been realized by generating stochastic pipe breaks on a water pipe network. The network “lifetime” has been subdivided into five-year time intervals. The planning schedule for the next five years is defined at the beginning of these time intervals (i.e. which pipes are replaced, and when they are replaced according to the optimization results). At the beginning of each of these periods, parameters values of the pipe break model are re-evaluated according to break records available at that time. Once the water pipe network is upgraded, pipe break records are extended to the next five years. This process of identifying water pipes to be replaced for the next five years is repeated until the end of the network “lifetime”. Results are reported for two hypothetical water networks of 100 and 250 pipes, respectively.

Bibtex:

@inproceedings{Mailhot608,
author    = { Leïla Dridi and Alain Mailhot and Marc Parizeau and Jean-Pierre Villeneuve },
title     = { A Strategy For Optimal Replacement Of Water Pipes Integrating Structural And Hydraulic Indicators Based On A Statistical Water Pipe Break Model },
booktitle = { 8th International conference on Computing and Control for the Water Industry },
volume    = { 1 },
pages     = { 65--70 },
address   = { University of Exeter, Angleterre },
year      = { 2005 },
month     = { 5-7 September }
}

Last modification: 2006/01/24 by parizeau

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