In the layout of a power house, the Surge Tank is provided in the penstock line primarily to
- AIncrease the velocity of water striking the turbine.
- BFilter out silt and debris before the water enters the turbine.
- CStore water for use during the dry season.
- DProtect the penstock from water hammer pressures during sudden load changes.Correct
Solution
Concept
Surge Tank and Water Hammer Protection
Formula
Joukowsky Equation: ΔP = ρ · a · Δv
Step-by-step solution
1. Review the question regarding the primary purpose of providing a Surge Tank in a hydro-power house penstock line. 2. Recall that sudden valve closures cause water hammer pressure (ΔP = ρ · a · Δv), which can burst the penstock if not absorbed by a surge tank. 3. Compare the functions with the options provided and select Option (d) as the correct choice.
Explanation
A surge tank is a small storage reservoir or water tank connected to the penstock pipe. When the load on the turbine decreases suddenly, the water valve closes, causing a high-pressure wave (water hammer) in the pipe. The surge tank absorbs this excess water and pressure, preventing the penstock pipe from bursting.
Shortcut
To remember the primary purpose of a Surge Tank, use the rule "Surge = Shock Absorber": - Surge/Hammer Guard: It absorbs sudden pressure rises (water hammer) caused by rapid valve closure. - Penstock Protection: It acts as an open shock absorber to keep the penstock pipe from bursting.
Common mistake
A common mistake is selecting Option C by confusing a surge tank with a primary storage reservoir or seasonal storage basin. While a surge tank holds water temporarily to absorb or supply pressure surges, its main function is not long-term seasonal storage. Another frequent mistake is selecting Option A, confusing the surge tank's function with that of a nozzle or penstock taper designed to increase flow velocity.
Correct answer: D) Protect the penstock from water hammer pressures during sudden load changes.