Numerical Study on the Effect of Defects on the Performance of Spray Lined Cast Iron Pipes

Abstract

Due to aging and deterioration, water pipelines, especially cast iron pipelines, are gradually approaching the end of their design life. To more effectively reline these deteriorated pipelines, water utilities have been seeking new solutions for pipe rehabilitation. Various technologies have been developed, among which, spray lining techniques have attracted the attention of water utilities. A number of water utilities in Australia already started trialling polymeric spray liners in their water pipe networks. It has been known that deterioration, in particular corrosion, induces surface defects, which may be in the form of corrosion patches, through-wall holes or cracks on the external surface of the cast iron water pipes. In the application process of spray liners, imperfections may also form, e.g., uneven liner thickness. The defects in the host pipe and the imperfections in the liner may significantly affect the performance of the lined pipes. Literature review reveals that little research was conducted to investigate the effect of these defects/imperfections on the mechanical behaviours of the lined water pipes. This paper aims to numerically investigate and quantify the effect of the holes in the cast iron host pipe and the uneven thickness in the polyurethene spray liner on the performance of the lined pipes, using three-dimensional finite element analyses. Various sizes of circular holes, different levels of uneven thickness in the liner, different values of internal pressure and friction coefficients at the interface between the cast iron pipe and liner are considered. The outcome of this study can assist in quantifying the size and geometry of an unacceptable defect for a given host pipe and liner.

Techniques