What is the primary purpose of a Surge Tank in a hydroelectric power plant?
- ATo increase the velocity of water entering the turbine.
- BTo act as a reservoir for periods of low rainfall.
- CTo protect the penstock from high-pressure waves caused by water hammer.Correct
- DTo aerate the water to prevent cavitation.
Solution
Concept
Surge tank function in penstock water hammer mitigation
Formula
NONE
Step-by-step solution
1. In a hydroelectric scheme, closing turbine gates rapidly causes deceleration of the large water column in the penstock. 2. This sudden deceleration produces high-pressure water hammer shock waves that can burst the pipe. 3. A surge tank provides a free water surface that absorbs the incoming surge and dissipates hydraulic pressure waves. 4. Therefore, its primary role is protecting the penstock from high-pressure waves. Answer: C
Explanation
In a hydroelectric installation, a surge tank is an open vertical tank connected to the penstock near the powerhouse. When turbine governor valves close rapidly during electrical load reduction, the surge tank accommodates the incoming water volume and absorbs extreme water hammer pressure oscillations, safeguarding the penstock against rupture.
Why the other options are wrong
A) Surge tanks do not increase water velocity entering the turbine. B) Water storage for seasonal variations is provided by the reservoir, not a surge tank. D) Aerating water is not the intended function of a surge tank.
Shortcut
Surge tank = Absorbs water hammer pressure surges to protect the penstock.
Common mistake
Viewing a surge tank as a water storage reservoir rather than a hydraulic shock absorber.
Correct answer: C) To protect the penstock from high-pressure waves caused by water hammer.