How to Protect Against Pump Trip Water Hammer?

2024-12-24

Water Supplementation (Air Injection) for Pressure Stabilization

Water supplementation (or air injection) can prevent water column separation or excessive pressure during flow interruption, thus mitigating water hammer. This category includes bidirectional pressure regulation towers, unidirectional pressure regulation towers, and air pressure tanks.

Bidirectional Pressure Regulation Tower: Built near the pumping station or at appropriate locations along the pipeline, the water level of the regulation tower should be higher than the water level of the receiving water pool at the end of the pipeline, while considering head loss along the pipeline. The pressure regulation tower will add water to the pipeline or release excessive pressure in response to pressure changes in the pipeline, effectively avoiding or reducing water hammer pressure.

Unidirectional Pressure Regulation Tower: Built near the pumping station or at appropriate locations along the pipeline, the height of the unidirectional regulation tower is lower than the pipeline pressure at that location. When the pressure inside the pipeline is lower than the water level in the tower, the regulation tower will supplement water into the pipeline to prevent water column separation and avoid water hammer.

Air Pressure Tank: Less commonly used domestically but widely applied abroad. The air pressure tank operates according to the specific laws of gas volume and pressure. As the pressure in the pipeline changes, the air pressure tank will supplement water or absorb excessive pressure in the pipeline, similar to the function of the bidirectional pressure regulation tower.

Water Discharge and Pressure Reduction

Water discharge and pressure reduction can prevent a rapid pressure increase. This category includes pump trip water hammer eliminators, slow-closing check valves, and burst discs.

Pump Trip Water Hammer Eliminators: There are three main types: downward-opening, self-closing, and automatic reset water hammer eliminators. They operate similarly in principle, where the eliminator opens when the outlet pressure drops to a certain level during a pump trip. When the water hammer pressure wave returns to the pump, the eliminator discharges water, thus eliminating the water hammer. The length of the protected pipeline typically does not exceed 800 meters.

Slow-Closing Check Valve: A type of check valve that mitigates water hammer through slow closure. This method is simple, practical, and widely applied. There are two types of slow-closing check valves: weighted and energy-storing types. The closing time of the valve can be adjusted within a certain range as needed. Typically, 70%-80% of the valve closure occurs within 3-7 seconds after power failure, and the remaining 20%-30% of the closure time is adjusted according to the pump and pipeline conditions, generally within 10-30 seconds.

Burst Disc: Similar to a fuse in an electrical circuit, a burst disc automatically ruptures when the pressure in the pipeline exceeds a preset value due to water hammer, causing water to discharge and thereby reducing pressure to eliminate the water hammer effect.

Other Types

Increase Pipe Diameter and Wall Thickness: By increasing the diameter and wall thickness of the pipeline, and reducing the flow velocity in the water transmission line, water hammer pressure can be reduced to some extent.

Reduce Pipeline Length: Instead of using a single pumping station, two pumping stations can be used, connected by a suction well.

Use of Pumps with Larger Rotational Inertia or Installing Flywheels: Using pump units with larger rotational inertia or installing flywheels with sufficient inertia can help reduce water hammer values to some extent.

Change the Pipeline Longitudinal Profile: When laying the water transmission pipeline, efforts should be made to avoid sharp changes in slope.

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