Settling Basin Design

Settling BasinDrawing water through the intake, its is not possible to extract clear water only, certain percentage of bed load as well as suspended load will also enter along with water.If the water along with sediment enter into the turbine, it will cause damage to the turbine due to abrasion.Therefore, its very necessary to supply as much clear water into the turbine.In order to exclude the sediment settling basin are provided in the water conveyance system.Settling basin is a wider section in the water conveyence system that decrease the velocity and allow the sediment to settle.Width and length of the settling basin is based on the required size of the sediment to settle.

Types of settling basinPeriodic Flushing typeContinuous Flushing TypeIntermittent Flushing Type

Periodic Flushing type

It has to be drained completely for the flushing. After draining, 10% of the design discharge is used for the flushing of the settled sediments. Effect the power plant operation

Continuous Flushing Type

Continuous Flushing TypeThe Bieri Settling basin ensures energy production even during the flushing procedure. The sediments which settle in the settling basin are flushed vertically through the opening into the flushing channel and back to the river. The flushing water volume is therefore kept to a minimum. Sensors permit fully automatic operation.

Intermittent Flushing TypeA special conduit filled with water can float and drawn and may close and open the slot of flushing channel.Modified form of continuous flushing type

Design parameters for SiltingFall VelocityConcentration of flow

Fall VelocityFall velocity is average terminal velocity of a particle falling in quiscent distilled water of infinite extent.It depends uponShape and size of the particleWeight of the particlesviscosity

Fall VelocitySettling velocity formula: = [4*g*d*/3*Cd]1/2 whereCd =Drag Coefficient = 24/Re = =d = diameter of settling particle

Concentration of flow