Seyed Ali Sadr-Al-Sadati; Mohammadreza Jalili Ghazizadeh
Volume 16, Issue 4 , January 2019, , Pages 229-248
Leakage in water supply networks causes loss of water and energy resources (Xu et al. 2014). Leakage prediction and optimal decision making on leakage control strategies require a deep understanding of the leakage-pressure relationship. High-density polyethylene pipes (HDPE) have been ...
Leakage in water supply networks causes loss of water and energy resources (Xu et al. 2014). Leakage prediction and optimal decision making on leakage control strategies require a deep understanding of the leakage-pressure relationship. High-density polyethylene pipes (HDPE) have been used extensively in water distribution networks in recent decades (Kim and Lee, 2015), and leakage behavior in this material is still debatable. The purpose of this study is to identify the leakage behavior of the longitudinal slits for high-density polyethylene pipes and the effective parameters in elastic faze.
Materials and methods:
To achieve the objectives of this research, a semi-industrial laboratory model was developed. Based on the preliminary studies and literature review, effective parameters were extracted and then 10 samples were prepared by considering the parameters of diameter and thickness of pipes, dimensions of slits and temperature. Then, the samples were pressurized by a high-pressure pump and, by setting the pressure, the leakage discharge of the longitudinal slits and temperature was measured during the test for each pressure. Using the dimensional analysis method, the experimental results were analyzed.
Results and discussion:
In the longitudinal slit of HDPE pipes, the leakage flow is a function of changes in the area of the leak. The results of the experimental investigation showed that the change in the effective area of the leak position with the pressure in the elastic state is relatively linear (Cassa, et al, 2010). Also, the slope of the effective area change due to the pressure variation depends on the parameters such as dimensions of slits, pipe diameter and thickness, and temperature. Among these parameters, the effect of the slits length and temperature had a greater effect on the amount of leakage in longitudinal slits. Using experimental results and using dimensional analysis, a relationship has been developed to estimate the effective area change of the leak in the longitudinal slits in the HDPE pipes. Using this relationship, leakage can be calculated at different pressures. In the present study, the leakage exponent for longitudinal slits in the HDPE pipe is calculated in the range of 0.44 to 1.44 and is consistent with the proposed relationship. If any of the effective parameters such as cracking length or pressure increase, in the elastic state, the leakage power is approaching 1.5 (Van Zyl and Cassa, 2013). Given the uncertainty about the size of the slits in the water distribution networks, one cannot provide a number for leakage power, but the average leakage power in the experiments is equal to 1. In another experiment, the effect of temperature on leakage was investigated independently at a pressure of 5 bar and showed that increasing the temperature could increase leakage in HDPE pipes. Also, at 40 ° C, it exits from the elastic state, and the slope of the changes increases significantly.
Based on the results of this research, it should be noted that the leakage control and pressure management should be considered more in urban water distribution networks with HDPE pipes. In addition to conventional parameters, the temperature should be taken into account. In the tropics area, the developed relationship was suggested to estimate the leakage of HDPE pipes and to select the appropriate strategy to reduce leakage.