Performance of pressure control valves and flow meters precision in operational irrigation-water balance accuracy

In pressure irrigation-water distribution networks, pressure regulating devices for controlling the discharged flow rate by irrigation units are needed due to the variability of flow rate. In addition, applied water volume is used controlled operating the valve during a calculated time interval, and assuming constant flow rate. In general, a pressure regulating valve PRV is the commonly used pressure regulating device in a hydrant, which, also, executes the open and close function. A hydrant feeds several irrigation units, requiring a wide range in flow rate. In addition, some flow meters are also available, one as a component of the hydrant and the rest are placed downstream. Every land owner has one flow meter for each group of field plots downstream the hydrant. Its lecture could be used for refining the water balance but its accuracy must be taken into account. Ideal PRV performance would maintain a constant downstream pressure. However, the true performance depends on both upstream pressure and the discharged flow rate. The objective of this work is to asses the influence of the performance on the applied volume during the whole irrigation events in a year. The results of the study have been obtained introducing the flow rate into a PRV model. Variations on flow rate are simulated by taking into account the consequences of variations on climate conditions and also decisions in irrigation operation, such us duration and frequency application. The model comprises continuity, dynamic and energy equations of the components of the PRV.

Control estadístico de la calibración de MDP volumétricos para la transferencia de custodia de hidrocarburos líquidos

Este proyecto tiene por objeto desarrollar una sistemática de control metrológico para vigilar la exactitud de los medidores volumétricos de desplazamiento positivo que operan en las compañías logísticas de hidrocarburos para la transferencia de custodia que están en el cargadero y se ensayan in situ para obtener su meter factor. El punto de partida son las hojas primarias de las calibraciones generadas frente a sus patrones y el prover que nos facilitan las compañías. Dado el elevado número de ensayos y debido a que estos medidores no tienen gráficos de control estables, el enfoque del tratamiento ha sido un etiquetado para realizar un control de inestabilidad y calidad de los ensayos y así, determinar equipos anómalos. Para la búsqueda de equipos atípicos se ha desarrollado el filtro de Tukey para el estudio de la estadística descriptiva de los valores del meter factor. Entre los dos métodos se han obtenido una clasificación de equipos vigilables, recalibrables y sustituibles para facilitar a las compañías logísticas. ABSTRACT The aim of this project is to develop a systematic metrological control to monitor the accuracy of the positive displacement flow meters operating in oil logistics companies for custody transfer which are in the loading track facilities and it are tested in-situ to obtain the meter factor. Due to the high number of assays that meters don´t have stable graphics of control, the approach of data processing has been a labeled to perform an instability and quality control of assays for establish anomalous meters. To find outliers meters is developed the filter of Turkey to study the descriptive statistics of meter factor values. Between both analytical methods is obtained a classification of controllable, recalibrables and replaceable meters to provide to the logistic company.

Increasing the accuracy of positive displacement meters for the measurement of volume in liquid hydrocarbon logistics

Accuracy in the liquid hydrocarbons custody transfer is mandatory because it has a great economic impact. By far the most accurate meter is the positive displacement (PD) meter. Increasing such an accuracy may adversely affect the cost of the custody transfer, unless simple models are developed in order to lower the cost, which is the purpose of this work. PD meter consists of a fixed volume rotating chamber. For each turn a pulse is counted, hence, the measured volume is the number of pulses times the volume of the chamber. It does not coincide with the real volume, so corrections have to be made. All the corrections are grouped by a meter factor. Among corrections highlights the slippage flow. By solving the Navier-Stokes equations one can find an analytical expression for this flow. It is neither easy nor cheap to apply straightforward the slippage correction; therefore we have made a simple model where slippage is regarded as a single parameter with dimension of time. The model has been tested for several PD meters. In our careful experiments, the meter factor grows with temperature at a constant pace of 8?10?5?ºC?1. Be warned