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Emitter clogging is a major problem in microirrigation systems, which may result from the isolated or combined effects of physical, chemical, and biological agents. Clogging caused by suspended solid particles is the most common plugging form of emitters. Water quality and emitter geometry are key aspects in clogging processes. Any suitable test procedure to assess the sensitivity of drippers to clogging should take into account the predominant factors that influence clogging and must reproduce the field conditions. This research set out to assess the performance and suitability of a laboratory clogging test procedure in order to validate a methodology and to provide scientific results that may support the standardization of a clogging test method. The evaluated methodology has been used by the IRSTEA laboratory since 1974 (Platform of Research and experiment on Science and Technology for Irrigation - PReSTI, formerly LERMI) and its contents are currently being discussed by the ISO TC23/SC18 committee. The aim is to define a standardized testing protocol to evaluate the sensitivity of emitters to clogging due to solid particles. Replications analyzing the clogging resistance of four models of emitting pipes were carried out in a laboratory. The clogging test procedure enabled an accurate assessment of the combinations of concentration and size of particles that caused clogging in each model of dripper. However, a significant variability in degree of clogging was identified when the results of replications for each model of dripper were compared. Several requirements, concerns, and improvements related to the clogging test protocol were discussed.

Information about local head loss caused by connections employed in micro-irrigation systems is hard to be found in literature. The objective of this research was to experimentally determine the local head losses in connections commonly used in micro-irrigation and propose mathematical models using the theorem of Buckingham. The methodology of tests was based on international standards. The tests were carried out under controlled inlet pressure, at 150 kPa, and five to ten units of each connection model were tested. The curves relating flow and head losses were drawn based on 15 flow conditions, obtained under increase and decrease of flow rate. For each condition, 30 points were collected resulting in a sample size of 900 points in each test. For each connection model evaluated, the following information was obtained: curves of local head loss as a function of flow rate and of local head loss coefficient (KL). The obtained values of KL ranged from 2.72 to 24.16, which become constant for Reynolds number higher than 10,000. The sensitivity of the coefficient related to a ratio of the internal sections in the connections was also verified. The flow exponents presented values close to the one applied by the Darcy-Weisbach equation (m = 2). The models developed for the connections presented a satisfactory performance.

PROJETO E VALIDAÇÃO DE UMA BANCADA PARA ENSAIOS DE PERDA DE CARGA LOCALIZADA  WAGNER WILSON ÁVILA BOMBARDELLI¹; ANTONIO PIRES DE CAMARGO²; ROGÉRIO LAVANHOLI³; ANA CLAUDIA SÁTIRO ARAUJO¹; MARCUS VINICIUS TALAMINI JUNIOR¹ E JOSÉ ANTÔNIO FRIZZONE4  1 Mestrando, Departamento de Engenharia de Biossistemas, Escola Superior de Agricultura “Luiz de Queiroz” - ESALQ/USP, Avenida Pádua Dias, 11, 13418-900, Piracicaba - SP. E-mail: wavila@usp.br, satiroagro@gmail.com, talamini.1988@gmail.com²Especialista em Laboratório, Departamento de Engenharia de Biossistemas - ESALQ/USP, e-mail: apc.pires@gmail.com ³ Doutorando, Departamento de Engenharia de Biossistemas – ESALQ/USP, e-mail rogeriolavanholi@usp.br4 Prof. Dr. Titular, Departamento de Engenharia de Biossistemas – ESALQ/USP, e-mail: frizzone@usp.br  1 RESUMO As perdas de carga localizadas são relevantes principalmente no dimensionamento de subunidades de sistemas de microirrigação. O uso de sistemas automatizados adequadamente projetados e validados para a execução de ensaios é conveniente, pois assegura maior estabilidade das condições de ensaio, otimização do tempo de operação, redução das falhas ou imperfeições humanas, consequentemente conduzindo a melhor qualidade dos resultados de ensaio. Deste modo, o presente trabalho propôs projetar, instalar e validar uma bancada automatizada para condução de ensaios de perda localizada de carga. Desenvolveu-se o circuito eletrônico microcontrolado que dispõe de funcionalidades para aquisição e condicionamento de sinais de sensores; controle de inversor de frequência e válvula proporcional; controle Proporcional-Integral-Derivativo (PID); e, comunicação Modbus RTU com outros dispositivos através de rede RS-485. O firmware implementado no microcontrolador foi desenvolvido na linguagem C, enquanto que a interface gráfica do usuário (GUI) foi desenvolvida em C#. A validação da bancada foi efetuada a partir de ensaios de estabilidade, que permitem afirmar o adequado funcionamento da bancada de ensaios. Palavras-chave: circuito eletrônico microcontrolado, hidráulica, microirrigação  W. W. Á. BOMBARDELLI; A. P. CAMARGO; R. LAVANHOLI; A. C. S. ARAUJO; M. V. TALAMINI JUNIOR; J. A. FRIZZONEDESIGN AND EVALUATION OF A TEST BENCH FOR DETERMINING MINOR PRESSURE LOSSES  2 ABSTRACT The minor pressure losses are fundamental in the development of subunits for micro-irrigation systems. The use of well-designed and validated automated systems in order to perform tests is convenient because it ensures a greater stability of test conditions, and also improves the use of operating time, reducing the risk of faults or human error, consequently, thus having better quality in the test results. Thereby, this paper aims to develop, install and validate an automated bench to conduct minor pressure loss tests. The previously developed micro-controlled electronic circuit has features to input and store signals from sensors; Frequency inverter controller and proportional valve; Proportional-Integral-Derivative Controller (PID); and a Modbus RTU communication protocol to interact with other devices via RS-485 network. The firmware implemented in the microcontroller was developed using the C programming language, whereas the graphical user interface (GUI) was programmed in C #. The validation of the bench was carried out using stability tests, which approved the test bench performance. Keywords: micro-controlled electronic circuit, hydraulic, micro-irrigation

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