Avaliação de características operacionais de conjuntos emissores de pivô central de irrigação

Abstract

The agricultural irrigation has numerous advantages, manly by enabling the increase of yield. Among the existing irrigation systems, the center pivot has reached an increasing interest of farmers, due to its differentials. This system consists, basically, of a lateral line that moves around a fixed point, and has water emitters equally spaced. Due to the circular movement of this line, the flow rates must be higher in the emitters approaching to its the end. To meet the parameters of a uniform irrigation, it is usual to equip emitter sets whit pressure regulation valves and nozzles of different diameters. The selection of the valves and the distribution of nozzles diameters are determined by the system design, therefore those characteristics must not be changed after the installation of the irrigation system. Among the motives that can prejudice the uniformity of center pivots, it can be included the malfunction and ware of these valves, due the time of usage. In this sense, the present work aimed to evaluate the functioning of valves and the conformity of nozzles of a center pivot. Valves tests were carried out following standard requirements, and the evaluation of the nozzles belonging to the same valve-emitter set, through diameter measurements and determination of flow rate as a function of pressure. Most of the valves met minimal quality criteria, according to standardization. However, half of the valves were reproved in hysteresis tests, which probably affects their operational performance in the field. In the nozzle’s tests, the relationships of flow-pressure defined by the manufacturer were observed, with an exception of one unity, due a probable manufacturing mistake. In nozzles distribution map in the center pivot, occurrences of parts installed in incorrect positions were observed, according to their diameters, being that a probable cause of a non-uniform irrigation applied by the system.