Question: Why surge tank is built (installed) with close conduit hydroelectric power plants?
Answer: Closed conduit of dam faces the irregular pressure of water under varying loads. A surge tank is installed for relieving the conduit pipes under varying loads.
In hydroelectrical power plants, water conduits connect the link to the turbine housing. During its operation water flows from the dam, passes through the conduit and runs down to the powerhouse.
During low demand conditions, the decreased water supply to the turbine causes the water surge to rush back towards the top. The surge tank stores extra water thus protecting the closed conduits from bursting.
During peak hours the water is drawn from the surge tank to fulfill the load demands. A surge tank is opened from the top level.