Short Answer:

Surge tanks are vertical storage tanks connected to pipelines that carry water, usually installed near pumping stations or steep slopes. Their main purpose is to absorb sudden changes in water pressure, especially during pump start-up or shutdown, helping to prevent water hammer and protect the pipeline.

Surge tanks work by temporarily storing excess water when pressure rises and releasing it when pressure drops. They act as a shock absorber, reducing the pressure surge and maintaining a steady flow. Surge tanks are widely used in hydropower plants, water supply systems, and irrigation pipelines.

Detailed Explanation

Surge Tanks

In long or high-pressure water pipelines, sudden changes in flow can lead to dangerous pressure surges known as water hammer. These surges can damage pipes, valves, and other components in the system. To prevent this, engineers use surge tanks—a simple but highly effective solution.

A surge tank is an open or closed vertical chamber installed along a pipeline, usually just before or after a pump or at high points in the system. It provides a place for water to rise or fall freely in response to pressure changes in the pipe. By doing this, it controls the flow of water and stabilizes the pressure.

Working of Surge Tanks

1. During Normal Flow
   In regular conditions, water flows through the pipeline, and the level in the surge tank remains steady. The tank stays filled up to a certain point depending on system design.
2. Sudden Flow Increase (Pump Start-Up)
   When a pump starts suddenly, it may push water too quickly into the pipeline, increasing the pressure. The surge tank absorbs the extra water temporarily, preventing a spike in pipeline pressure.
3. Sudden Flow Decrease (Valve Closure or Pump Stop)
   If the flow is stopped suddenly, like when a valve is closed or a pump shuts off, a vacuum or negative pressure may develop. The surge tank supplies water to fill this gap, preventing pressure drop and flow reversal.
4. Water Movement in the Tank
   The water level in the surge tank rises and falls as needed to balance the pressure in the system. This movement continues until the pressure returns to normal and the flow stabilizes.
5. Restoration of Flow
   Once the system stabilizes, the water level in the tank returns to its normal position, ready for the next surge event.

Types of Surge Tanks

• Open Surge Tank: Open to the atmosphere, simple in design, easy to maintain.
• Closed Surge Tank: Sealed tanks that work under pressure, often used where space is limited.
• One-Way Surge Tank: Allows flow only in one direction, useful for specific control.
• Restricted Orifice Tank: Has an orifice that controls the rate of flow in and out, providing smoother pressure control.

Applications in Civil Engineering

• Hydropower Plants: Used between reservoirs and turbines to manage water pressure changes.
• Water Supply Pipelines: Installed near pump stations to handle startup and shutdown surges.
• Irrigation Systems: Helps in managing uneven flow conditions in long canals or pipelines.

Advantages of Surge Tanks

• Prevents water hammer and pipe damage.
• Improves safety and reliability of the system.
• Simple to operate with low maintenance.
• Reduces pressure fluctuation and flow reversal.

Limitations of Surge Tanks

• Requires space for installation.
• Initial cost can be high for large systems.
• Needs proper design to match system characteristics.

Still, surge tanks are one of the most efficient and reliable methods to manage pressure surges in civil engineering water systems.

Conclusion

Surge tanks are vertical chambers connected to pipelines that help prevent water hammer by balancing pressure changes. They absorb extra water when pressure rises and supply water when pressure drops, ensuring smooth flow and protecting the pipeline. Widely used in hydropower, water supply, and irrigation, surge tanks are a vital part of fluid system safety and efficiency.