Metodología innovadora para la selección de la instrumentación de un proceso

Abstract

A methodology for selection of process instrumentation and some approaches that allow estimating the influence of the instrumentation on the stability of the processes are presented. The method, once established the pattern of the system, proceeds to simulate it with the MatLabâ, program maintaining in a transparent way the elements of the instrumentation: Transmitters and control valves. The open knot parameters of the controller adjustment are obtained using the methods of Dahlin and Ziegler-Nichols. Then, the controller type that presents better performance is closed knot proven (P, PI and PID) to obtain the best control strategy. To select the analyzers (transmitters) we proceed to determine the variation range of the measurement variables, which allows defining the calibration of the instrument. The valve type (lineal or isoporcentual) that presents the best behavior of the process in study is selected, by means of changes in the ;Set Point;. The effect of the security that should have the valve performance when energy fails is considered. An example is presented where the operability of the method is proven. In order to determine the controller robustness for changes in the dynamics of the instrumentation, some values are modified. These values are: nominal gain, time constant and time out of the control valve selected for a lineal system in which the process output is controlled. The controller response is considered robust, if fulfills its function for changes in the dynamics of the instrumentation of until a 20%.