Measurement of flow rates of water in large diameter pipelines using radiotracer dilution method

The present paper describes measurement of flow rates of cooling water in two large diameter pipelines in a thermal power plant using radiotracer dilution method. The objectives of the measurements were to validate the pumping efficiencies of the Vertical Turbine (VT) pumps used for pumping sea water through the pipelines and also calibrate the installed flow meters. Iodine-131 in the form of sodium iodide dissolved in aqueous solution was employed as radiotracer for flow rate measurements. The measurements were carried out at two different pumping units (Unit-1 and Unit-2) with single as well as with simultaneous operation of the two different, but identical pumps. The measured flow rates in Unit-1 and Unit-2 were found to be 15.4 ± 0.46 m3/s and 14.1 ± 0.43 m3/s, respectively with operation of a single VT pump. Whereas the measured flow rates in Unit-1 and Unit-2 were found to be 27.5 ± 0.82 m3/s and 24.55 ± 0.78 m3/s with simultaneous operation of the two identical VT pumps. The measured pumping efficiency of each individual pump was found to be quite close to the theoretically predicted pumping efficiency, i.e. 15 m3/s. The measured flow rates were also found to be quite different from the flow rates shown by the installed flow meters.