The effect of increasing operating pressure and water salinity on the performance of some common pressure compensating emitters

Document Type : Research Paper

Authors

1 Assistant professor in National Salinity Research Center

2 Department of Soil Chemistry and Plant Nutrition, National Salinity Research Center, Agricultural Research, Education and Extension Organization, Yazd, Iran

3 Department of Irrigation and Soil Physics, National Salinity Research Center, Agricultural Research, Education and Extension Organization, Yazd, Iran.

Abstract

This study has been designed and carried out due to the existence of different expert opinions about the effects of operating pressure and irrigation water salinity on the performance of common pressure compensating emitters in irrigation systems and with the aim of investigating these effects. The study evaluated three commercial brands, “Netafim”, “Eurodrip,” and “Peresi Zalvan.” These emitters were tested at flow rates of 8 and 24 liters per hour under operating pressures of 0.5, 1.5, and 2.5 bars. Additionally, two levels of water salinity (5 and 12 dS/m) were considered. The results revealed that increasing operating pressure from 0.5 to 2.5 bars and raising salinity from 5 to 12 dS/m led to either increased or unchanged coefficient of discharge variations in different emitters. Furthermore, the deviation of average flowrate from the nominal discharge did not consistently follow a decreasing or increasing pattern with changes in salinity and pressure. Comparing pre-test (new) emitters with post-test (used) ones showed variations due to various factors, including pressure changes, salinity effects, and inherent emitter characteristics. Notably, the impact of salinity not resulted in significant and noticeable differences in emitter performance under varying pressure conditions. However, for the Netafim and Eurodrip emitters (8 l/hr), averaging the results across all three operating pressures indicated that increased salinity led to reduced discharge. Specifically, the reduction was approximately 3.8% for Netafim and 2.6% for Eurodrip. According to the results and examination of the destroyed samples, it can be concluded that the application of 2.5 bar pressure led to the entry of parts and solid objects in the irrigation pipes or passed through the filtration system into the emitters, resulting in a considerable decrease in flow rate. However, this problem can be solved to a large extent by washing the pipes before starting the system. Netafim emitters (8 l/hr), despite the lack of significant entry of these objects, had a diaphragm adhesion problem, and showed the greatest decrease in flow rate due to this reason. A detailed examination of the destroyed samples showed that the reason for these differences is the different shape and structure of the water inlet. Accordingly, the smallness of the cross-sectional area of water inlet, reduces the entry of solid parts. Therefore, the applying of 2.5 bar pressure resulted in the highest rate of solid parts entry to the Peresi Zalavan with the largest cross-sectional area and the lowest rate of entry in the Netafim (8 l/hr).

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