The performance of a pressure regulator valve, manufactured by Fabrimar (Model Exact-20-Ref. RP-3-20-3/4"FF), for central pivot applications, was evaluated in the laboratory following the ISO 1993 norms. The tests were conducted in the Laboratory of Irrigation of the Department of Rural Engineering, ESALQ/USP. The performance curves of the new valves satisfied the conditions established by the norm, characterizing the regulator as type A, for reference velocity of 0.5 m s-1 (flow of 0.57 m³ h-1) up to 4.0 m s-1 (flow of 4.50 m³ h-1) and several inlet pressures. A model for the outlet pressure of the new regulator, as a function of flow and inlet pressure, was also developed. Pressure regulators of a given model were collected from several central pivot systems and from different spans in the system, such that an array of pressure regulators with 2000, 2500, 6000, 8500, 9000 and 10000 h of operation at several water qualities were obtained. These pressure regulator were evaluated according to ISO 1993 as well. In spite of the effect of water sediments on the pressure regulator and observed leaks, the hydraulic performance of the valves with 6000 h did not differ in comparison to the new ones, for inlet pressures of 826.3 kPa and reference velocities up to 2.5 m s-1. The performance of the pressure regulators with 8500 h or more of operation did not perform as well as the new ones, especially for upper inlet pressures over 481,7 kPa.
pressure regulators; performance; center pivot
