Pump failure water hammer protection of pumping station pressurization and gravity combined water supply project

Aiming at the long-distance and high-drop water conveyance project with the combination of pressurization and gravity flow in a head pumping station, the mathematical model of the whole system hydraulic transition process was established based on the characteristic line method commonly used in transient flow calculation, and the whole process of pump failure water hammer was simulated. In order to solve the problem of negative pressure in the pipeline after power failure of water pump unit, the protection scheme of using air tank behind the pump was put forward, the parameters of air tank were optimized, and the better shape of air tank was determined. A high-level water tank was set at the highest point of the pipeline, and the gravity flow section behind the water tank adopted the mode of series connection of pressure reducing valve and regulating tank for energy dissipation. Under the condition of pump shutdown, in order to avoid empty leakage of the high-level water tank, it was necessary to close all pressure reducing valves. In order to prevent the booster water hammer generated by valve closing from exceeding the pipeline pressure bearing standard, resulting in pipe explosion accident, and considering the influence of water level fluctuation of each regulating tank, different valve closing schemes were selected for comparison. The calculation results show that the preferred volume of the air tank of the project is 15 m~3, and the pressure reducing valve is closed in a straight line in 120 s after the pump is stopped. Since the regulating tank is set behind the pressure reducing valve, closing the valve successively and closing the valve at the same time has little impact on the results. The research conclusion provides a reference for the design and safe operation of similar water supply projects.