Potable (drinking) water is transferred from Tilal Pumping Station to a Break Pressure Tank via a single dedicated GRP pipeline which varies in diameter along the route. The pipeline is fed from a number of high head pumps in Tilal PS.
A simulator of the system was built and a detailed steady flow analysis was undertaken for a wide range of potential operating conditions to ensure the selected pumps were capable of meeting their duty requirements. Once the model had been calibrated, various transient pump shutdown events were modelled. Particular focus was given to ensuring the pressures in the pipeline remain above atmospheric during transient conditions to minimise the risk of contamination entering the pipeline. In order to prevent contamination of the water supply, surge vessels were recommended and calibrated at the pumping station, including the installation of a backflow restrictor on the surge vessel connecting pipework to reduce the severity of the maximum surge pressures in the pipeline.
A detailed formal report was written and particular focus was given to the pump non-return valve selection as the study had identified that non-return valve slam could be an issue. The closure requirements of the pump check valves were determined in the study and suitable valve types were proposed, together with recommendations on the valve spring torque settings.