A surge tank is a small reservoir or tank in which the water level falls to reduce pressure fluctuations, so that they are not transmitted in a full-closed circuit also reduce the distance between the free water surface and turbine thus reduces the water hammer effect.
To serve as a supply tank for increased load conditions, and storage tanks in case of low load conditions.
Here we will learn about water surge tank, types of surge tank & how does a water surge tank work?
Introduction to surge tank:
A surge tank is a tank fitted on a pipeline in the upstream side of the control valve, used to control and stop the flow of water through the pipe.
It is provided on the pen stock in the hydroelectric plant, the surge tanks are placed close to the turbine.
The height of the surge tanks is usually kept above the maximum water level in the supply level reservoir.
Functions of Surge Tanks:
- This provides a free reservoir surface above the turbine intake to absorb and recompense the water hammer effect.
- It reduces the length of the high-pressure conduits that is essential to resist the water hammer effect.
- Also reduces water level fluctuations after load changes.
- It protects the drain system from excessive inside pressures.
- It should assistance the hydraulic turbine regarding its regulation characteristics.
- The pressure to store water extends strain in drop circumstances.
Type of Surge Tank:
The various types of surge tanks used in hydroelectric water convection methods are as follows:
Simple surge tank:
It has a vertical pipe that is linked between the pen stock and the turbine generator.
They are built with greater height and also provide support for holding the tank.
Whenever the speed of the water increases rapidly, the excess water is stored in the resistance tank.
The top of the surge tanks is opened to the environment, if the surge tanks are totally filled then this pressure is overtaken to take care of neutralization.
Gallery type surge tank:
Gallery type surge tanks have additional storage galleries also known as expansion rooms; so it is also called as a growth room surge tanks.
These growth rooms are often provided on the backside and prime levels.
At the bottom of the tank, level chambers are used to store excess water, when needed or run with a slight drop in pressure.
The chambers on the upper-pressure level are used to absorb the extra pressure.
Sloping surge tanks:
In this, the tank is provided with certain tilt.
The over-pressure enters the tilted tanks by providing tilted surge tanks with overflow water and the pressure is dissipated.
Restricted Orifice Surge Tank:
It has orifice between the pipeline and tank.
This drain is called throttle, so it is also called throttle surge tanks; this throttle or hole has a small diameter.
If water overflows it should enter the tank through this orifice.
Differential surge tanks:
In this tank, an internal riser is installed within the tank.
This riser has a very small diameter through which the water leaks; there are annular docks when the reduction in the riser is over.
Advantages of Surge Tank:
- It reduces detecting potential problems like vortex flow or waterfall.
- It provides proofing the safety against outflow from the aeration structure.
- Also, used in Measurement of throttle loss.
- It has low cost of computation time.
- They have verification of variants.
- The possibility of multi phase simulation.
Disadvantages of Surge Tank:
- No simulation for wind behaviour.
- No simulation for water hammer.
- Time-consuming calculation and evaluation.
- Calibration required.
Surge tank are installed in hydropower plants to reduce pressure forces during acceleration.
They reduce the distance between the free water surface and the turbine thus reducing the water hammer effect.