Air vessel–one-way surge tower hybrid protection strategy with dynamic valve control for water hammer mitigation in long-distance pumped flow systems

In long-distance pumped flow systems with multiple uphill sections, an accidental pump trip may induce severe water hammer. For a mountainous water supply project in Xinjiang, simulations show that after a pump trip, water rapidly flows back under gravity, causing the pump reverse speed to reach 1.723 times the rated speed. Pressure along almost the entire uphill section drops below vapor pressure, thus risking pump damage and pipeline collapse. Traditional protection methods often face excessive equipment size or insufficient protection due to difficulties in coordinating pressure waves. To address these challenges, three models – unprotected, single-device, and hybrid – were developed using Bentley Hammer. A two-stage fast–slow valve closure, coordinated with pump inertia, was combined with an air vessel – one-way surge tower. Results indicate two-stage valve closure effectively suppresses pump reverse rotation, reducing maximum downstream pressure by 20–30% versus linear closure. For single air vessel protection, discrete installations downstream and along the uphill section enhance resistance against negative pressure. Compared with the single air vessel strategy (peak pressure 2.136 times rated), the hybrid reduces vessel volume by 57.14%, limits peak pressure to 1.143 times rated (46.49% reduction), and lowers minimum pressure to –0.216 m. This demonstrates superior safety and economic efficiency, providing guidance for water hammer protection in similar projects.