Abstract
South Africa is a water scarce country where a large number of people still are not provided with adequate water. This project will help to manage water resources in a sustainable manner that will benefit the country as a whole.
This study concentrated on the behaviour of pipe materials with leak openings under different pressure conditions. The stress distribution throughout a pipe is known due to the pressures within the pipe i.e. the longitudinal and circumferential stresses as well as the working pressure of the pipe, however when a leak opening such as a hole or crack appears in the pipe the stress distribution around these openings change. It is the effect of this stress distribution that this study addressed. The effect of stresses around these leak openings may provide some knowledge as to how and when the pipes will fail completely as well as help in explaining the leakage exponents within pipes.
Using the method of Finite Element Analysis (FEA) the project aimed to find the relationship between the pressure in the pipe and the behaviour of the leak openings for different leak types. The different leak openings investigated were: a circular hole, a longitudinal crack and a circumferential crack. This study used finite element analysis to understand what happens to a pipe when pressure is applied within the pipe and the pipe has a leak opening e.g. a small hole, a longitudinal crack or a circumferential crack in it. The materials studied were uPVC, steel, cast iron and fibre-cement.
The main conclusions drawn from this study were that when a pipe has a circular hole in it the leakage exponent does not differ from the theoretical value of 0.5. With the longitudinal cracks it was found that regardless of whether there are longitudinal stresses in the pipe or not the leakage exponent is the same: and these exponents vary significantly from the theoretical value of 0.5 and can be in the order of 0.87, 0.82, 0.75, 0.55 for a 60 mm long crack in an uPVC, steel, cast iron and fibre-cement pipe respectively. With the circumferential cracks however, there were significant differences in exponents due to the longitudinal and lack of longitudinal stress. For the case when the pipe has the longitudinal stresses the exponents were significantly larger than 0.5. The exponents were in the order of 1.15, 1.02, 0.95, and 0.64 for a 150 mm long crack of uPVC, steel, cast iron and fibre-cement respectively. If there is no longitudinal stress then the exponents were smaller than 0.5 and tended to close the crack along the circumference. The exponents were 0.45, 0.47, 0.46, and 0.49 for a 150 mm crack of uPVC, steel, cast iron and fibre-cement respectively.
Prof. J.E. van Zyl