Failure of corrosion affected buried cast iron pipes subject to water hammer

Abstract

Water hammers can be generated when the steady state conditions change at a given point of pipeline due to some instantaneous events such as fast closure of valves or pump shout down. The magnitude of water hammer pressure in water pipes can well exceed the strength of the pipes, in particular, when they have been deteriorated due to, e.g., corrosion. This paper intends to present a time-dependent reliability method for the prediction of the risk of pipe failures under the adverse combination of the excessive water hammer pressure and corrosion induced reduction of pipe strength. Stochastic models are proposed for both pitting corrosion and water hammer pressure. It is found in the paper that the risk of pipe failures increases with the increase of mean occurrence rate of water hammer and that the sudden closure of pipe valves can have devastating effect on the safety of pipeline networks. The paper concludes that the time dependent reliability method can predict the risk of pipe failure more accurately under the combined stochastic effects of the water hammer pressure and corrosion induced deterioration of the pipe. Accurate prediction of pipe failures can ensure the safe and reliable operation of pipelines, which has the potential to prolong their service life.