Reverse flow alarm activation using electrical capacitance tomometric (ECTm) correlation

In process fluid transportation, especially in inclined pipes, as often found in subsea installations, the flow of fluids, before separation, is essentially multi-phase. Experiments on lab scale facilities indicate clearly, when a multiphase flow is initiated in an inclined pipe, although the average flow is in a particular direction, very frequently, reverse flow is also observed. Reverse flow combined with slug flow can be detrimental to the hardware associated with the pipe-lines, such as actuators. By using non-intrusive and non-invasive capacitance sensor arrays placed on the periphery of the pipe using established techniques for isolation with peak, and measuring the inter-electrode capacitances on line, i.e. in real time, the distribution of the different components of the flow can be found based on their permittivities. When the time series of the measured capacitance values are correlated, with a twin plane arrangement of the electrodes, the correlated signals give the flow velocity. In such a tomometric approach, real algorithms can indicate reverse flow conditions without much delay, thus enabling the process engineer with a simple tool to alleviate problems caused by unexpected reverse flows, particularly of high velocities. By processing the raw capacitance values instead of performing image analysis, this electrical capacitance tomometric correlation can accelerate the decision process considerably.