Water hammer protection and pump-valve linkage optimization for combined pump-pressurized and gravity flow water delivery systems

Combined pump-pressurized and gravity flow are increasingly relevant in large-scale water delivery methods, yet the transient control strategies for such integrated configurations remain insufficiently addressed. This paper presents an investigation into water hammer protection measures for the system and delineates the functional layout of each hydraulic section. A theoretical framework is established to analyze the pump-valve linkage. Theoretical formulas are derived to guide valve operation and to calculate replenished water volumes for the high-level surge tank and energy dissipation boxes (EDBs). The correlation between valve operation and water replenishment volume is examined. A corresponding pump-valve linkage strategy is determined for accident conditions. The effectiveness of the proposed protective measures has been demonstrated through an actual water delivery project. The derived valve closure rule and water replenishment volume formula are consistent with the numerical simulation results, providing a reliable basis for designing pump-valve linkage strategies and optimizing the hydraulic layout of water delivery systems. Analysis indicates that valve closure methods of valves exert limited influence on system pressure variations and air vessel performance. Simultaneous valve closure can effectively reduce fluctuations in the water levels of the high-level surge tank and EDBs. The research results can serve as a reference for the design, safe operation, and emergency control of water hammer protection in combined water delivery systems, while also reducing the computational workload of numerical simulations.