Why Surge Tank Is Rquired in Hydro Electric Power Plant?

In Hydro Electric 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 requirement of Surge Tank is due to some problems which occurred 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 Vibrations,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 burst the pipe

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

Whenever the requirement 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.

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