Avaliação metrológica de hidrômetros utilizados em perímetros irrigados do Brasil e Espanha

Abstract

The installation position of multi-jet velocimetric water meters is one of the factors that can interfere with its metrological performance, with the possibility of decreasing the sensitivity of its mobile mechanisms, and thus, under-measurement and over-measurement errors can occur. Thus, the present work aimed to study and evaluate the installation positioning of the flow measurement equipment, that is, to test through bench tests in the laboratory, the functioning of the hydrometers used in different installation positions: horizontal, horizontal rotated and vertical, and observe if the positioning can generate a difference in the final flow. The tests were carried out on water meters used in irrigated perimeters in the state of Ceará in comparison with those of communities in Spain. The tests carried out for the bench tests were conducted at the Hydraulic and Irrigation Laboratory of the Polytechnic University of Valencia (UPV), located in the city of Valencia, Spain. The laboratory has adequate structure and equipment to carry out the tests. It is part of the certification and standardization committee for irrigation material and hydraulic installations and has technical approval of European Union (UNE) standards. The test consisted of testing the hydrometers in three different positions (horizontal, horizontal, rotated and vertical) and checking if their operation was within the limits of error acceptable by the technical standards established by ISO 4064. The test procedure of the hydrometers was based on the circulation of water upstream and downstream of the hydrometer, causing the water to circulate throughout the pipeline, crossing the hydrometer and recording the volume on the meter clock until it flows into the weighing tank, for the receipt of water and registration of its mass. Reaching, with that, the data necessary to calculate the measurement error. The maximum tolerance of the acceptable measurement error is the error to be within the limits of ± 5% between the minimum flow (Qmin) and the transition flow (Qt), where these limits comprise the lower measurement field and ± 2% between the transition flow (Qt) and the maximum flow (Qmax), comprising the upper measurement field (ISO 4064). The metrology of the hydrometers, knowing the quality of the equipment, the conditions of installation and operation are of fundamental importance for a decision on water management in the agriculture sector. Thus, the most suitable and recommended installation position for a better performance of multi-jet velocimetric water meters was in the horizontal installation position, that is, with the turbine axis in the vertical position. Another factor observed in the operation of this equipment was its age, where it is related to its time of use. The time of use of the hydrometer can be observed through its accumulated volume and the hydrometers that presented a greater accumulated volume also had an influence on the proper functioning of its mechanisms.