عنوان مقاله [English]
One of the main reasons for sprinklers, low pressure in sprinkler irrigation systems is related to incorrect estimate of quick coupling valves, minor (local) head losses. In order to measure the quick coupling valves, minor head losses, a laboratory study was conducted in accordance with ISO 9644 and ISO 4059 international standards during year 2014. Seventy-five quick coupling valve samples were selected from fifteen manufacturers, and made of three materials of cast iron, aluminum and polymer within three sizes comprised of 1, 1.5 and 2 inch. They were tested in terms of head loss. For each sample, the minor head losses were assessed using five flow rates including the maximum, minimum as well as three intermediate flow tests. Results indicated that, there are significant differences in the minor head loss values of similar quick coupling valves due mostly to manufacturing quality. Based upon the obtained results, the average minor head losses of 1 inch quick coupling valves obtained within the maximum vs. minimum flow rates were 0.46 and 10.23 m, respectively. As for 1.5 inch they were recorded 0.60 and 4.31 m, respectively, whereas for 2 inch, the figures were 0.21 and 1.76 m. Head loss values for low level flows were close to those given in their catalogues. But as for high flows, the head loss was recorded higher than those in the catalogue values. The head loss coefficients (K) of seventy-three quick coupling valve samples were recorded in the range of 7.26 to 9.79. However, based on the standards and criteria of pressurized irrigation systems, the minor head loss coefficients of quick valves should stand in the range of 2 to 2.2. The results finally indicated that the head loss related to quick coupling valves is high and that can be an important cause of low pressure in sprinkler irrigation systems.