Why Surge Tank is required in HydroElectric Power Plant?

In HydroElectric Power Plant Water is used to generate Power by using some Hydraulic Machines.For the smooth operation of Power Plant some necessary
arrangements are required,Surge Tank is one of them.

The requirment of Surge Tank is due to some problems which occured in Water Flow.First I will cover the possible problems in Flowing Water,these are,

A)Water Hammer:-
Due to Motion,Water possess some Momentum.This Momentum is destroyed,if the Flowing water is suddenly brought to rest,by closing the Valve.

A very High Pressure is developed on Valve.This High Pressure is followed by a series of Pressure Viabrations,resulting noise in pipe.This noise is known as
"Knocking".

The sudden rise in Pressure has the effect of Hammering Action on the walls of pipe, known as Water Hammer.This Water Hammer can brust the pipe

In HydroElectric Power Plant,the requirment of Water goes on changing,that's why it is essential to increase or decrease the Discharge flowing through
the pipe line.

Whenever the requirment of Water suddenly decreased,the Valve must suddenly closed,resulting a very High Pressure developed in entire pipe line
between the Reservoir and the Turbine.This is happened due to Water Hammer.

To overcome this problem,a Storage Reservoir called as "Pen Stock" is fitted at some opening made on the pipe line in order to store Water when the Valve
is suddenly closed, or to discharge Water when increased discharged is required.Such a Storage Reservoir is known as "Surge Tank".

Functions of Surge Tank.
01)To control the Pressure Variations,due to rapid changes in the pipeline flow,thus eliminating Water Hammer possibilities.

02)To regulate the flow of Water to the Turbine by providing necessary retarding Head of Water.

The Surge Tanks are placed near to the Turbine.The Height of Surge Tank is generally kept above the maximum Water Level in the supply Level Reservoir.

Ther are three important types of Surge Tanks used in HydroElectric Power Plant.
01)Simple Surge Tank
02)Restricted Orifice type Surge Tank
03)Differential Surge Tank.

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