Short Answer:

A surge tank is a vertical structure connected to a pipeline that helps manage sudden changes in water pressure, especially in long pipelines or hydropower systems. It acts as a safety device to absorb excess pressure during water hammer or rapid valve closures.

The main function of a surge tank is to stabilize pressure fluctuations by storing or releasing water temporarily. It protects pipelines and equipment from damage due to sudden pressure surges and helps maintain smooth and controlled flow in the system.

Detailed Explanation:

Function of surge tanks in pipelines

In hydraulic systems, especially those involving long pipelines or high-pressure flow like in hydroelectric power stations, sudden changes in flow conditions can cause dangerous pressure variations known as water hammer. A surge tank is a vertical chamber or container installed near the start or along the length of a pipeline to absorb these pressure shocks and ensure system safety and stability.

Purpose and Working of Surge Tanks

1. Pressure Control
   When valves close suddenly or turbines stop, water in motion suddenly decelerates, creating a high-pressure wave. A surge tank provides an open space where this extra pressure can escape, avoiding pipe bursts or structural damage.
2. Flow Regulation
   When demand drops quickly, excess water enters the surge tank instead of stressing the pipeline. When flow demand increases, water from the surge tank can flow back into the system, ensuring smoother operation.
3. Water Hammer Protection
   By providing an immediate outlet for sudden flow changes, the surge tank reduces the intensity of water hammer, a shock wave caused by abrupt velocity changes in pipelines.
4. Energy Balance
   In systems with turbines or pumps, surge tanks help balance hydraulic energy and minimize pressure instability. They assist in maintaining constant operating conditions even when flow changes rapidly.

Types of Surge Tanks

Though not required for this answer, common types include:

• Simple surge tanks (open to atmosphere)
• Restricted orifice tanks (with flow resistance)
• Differential surge tanks (with inner risers for controlled flow)

Each type is used based on system design, location, and risk of pressure variation.

Applications in Civil Engineering

• Hydropower Plants: To manage load variations and sudden turbine shutdowns.
• Water Supply Systems: In hilly terrains where gravity-fed pipelines face rapid changes.
• Pump Systems: Protect pumps and pipes from pressure surges caused by start-stop cycles.
• Irrigation Projects: To maintain stable flow and reduce risk of damage during switching.

Properly designed surge tanks reduce maintenance needs, increase system life, and ensure safety.

Conclusion:

The surge tank plays a vital role in protecting pipeline systems from damage caused by rapid pressure changes. Its main function is to absorb and release water as needed to stabilize flow and reduce water hammer effects. This simple yet essential structure ensures the safe and efficient functioning of complex hydraulic systems, especially in power generation and long water transport pipelines.