Surge Tank Function and Explanation:

A surge tank is an essential component in hydraulic systems, particularly in hydropower plants or water distribution systems. Its main function is to relieve water hammer pressures in the penstock pipe. Water hammer is a phenomenon that occurs when the flow of water in a pipe is suddenly stopped or changed direction, resulting in a rapid increase in pressure. This pressure surge can cause damage to the pipe and other system components if not properly controlled.

Explanation:

1. Definition of Water Hammer:
Water hammer is a pressure surge that occurs when there is a sudden change in fluid flow, such as rapid valve closure or pump shutdown. This change in flow causes the kinetic energy of the fluid to be converted into pressure energy, resulting in a pressure wave propagating through the pipe.

2. Consequences of Water Hammer:
Water hammer can have several detrimental effects on a hydraulic system, including:

- Increased stress on pipes and fittings, leading to potential failure.
- Damage to valves, pumps, and other system components.
- Noise and vibration, which can be disruptive and potentially harmful.
- Loss of efficiency and increased energy consumption.

3. Surge Tank Function:
A surge tank is designed to mitigate the effects of water hammer by providing a cushioning effect. It acts as a temporary reservoir or storage volume that absorbs excess pressure surges and prevents them from propagating throughout the system.

- When a sudden change in flow occurs, the surge tank allows the fluid to expand and compress within its volume, reducing the pressure rise.
- This expansion and compression of the fluid help to dissipate the excess energy and minimize the impact of water hammer on the system.
- The surge tank acts as a shock absorber, absorbing the pressure waves and preventing them from damaging the pipes, valves, and other components.

4. Surge Tank Design:
The design of a surge tank is based on the specific requirements of the hydraulic system. Some key considerations include:

- Size: The surge tank volume should be sufficient to accommodate the expected pressure surges without reaching dangerous levels.
- Location: The surge tank is typically placed near the point of water hammer generation, such as close to the pump or valve.
- Inlet and Outlet: The surge tank should have separate inlet and outlet connections to allow the flow of fluid in and out.
- Air Vent: An air vent is often included to release trapped air and prevent the formation of air pockets that can affect the surge tank's performance.

Conclusion:

In conclusion, the function of a surge tank is to relieve water hammer pressures in the penstock pipe. It acts as a shock absorber, absorbing the pressure surges and preventing damage to the hydraulic system. By providing a cushioning effect, the surge tank helps maintain the stability and integrity of the system.