The intakes or intake works are the devices or structure installed for the purpose of drawing water from the source.Opening,strainer or gratting through which water enters.The conduit conveying water usally by gravity to a sump.It should be located at a place safe against damage of floods.
What are types of intakes
1.River intakes: The river intake consists of circular lower 3 to 6m is diameter constructed in masonry or concrete on the bank of river at a sauitable point.The pump house is located in the top of the tower the lower chamber act as asump well.Two or more penstocks covered with coarsed screen are provided at different level to the sump well the penstocks are fitted with values to regulates the flow into the well.
The penstocks just the existing water level,is only operated at any time and the remaining are closed so as to avoid high entry velocities.If velocity is high trubulence will occur resulting the ingress of silt into the well water collected in sump is pumped to the treatment plant.
2.Canal intake: A canal intake consists of essentially a bell mouth pipe covered with fine screen,placed in a small intakes chamber constructed partly in the canal bank.The chamber is provided with a side opening fitted with coarse screen to check the entry of the floating matter a pipe i provided with value which is operated from the top regulates the flow.
The fine screen on the top of bell mouth pipe prevents the entry of slits and other small particles from entering into the pipe.The entry velocities through coarse screen and fine screen are limited to 15cm and 30cm respectively.The canal bed up stream and down stream of intakes are provided with pitching to protect against scouring.
3.Lake in take: The lake intake consists of a submerged bell mouth pipe fitted with cast iron strainer projecting into the water.The pipe is surrounded by a square or octogonal wood crib protected by rock boulder the water enters through perforation of the strainer and is conveyed through outlet pipe to the treatment plant.The intakes opening should be located sufficiently above the bottom of the lake so as to minimise the danger of pollution.
4.Reservoir intake: It consists of a circular will constructed in masonry or concrete.The intakes pipes covered with screen,are located at different level,to draw clear water devoid of floating material.Values are fitted to the intakes pipe to control the entry of water.The pipe just below the existing water level in the reservoir is opened and the other pipes are closed at any time,to avoid high entry velocities due to large heads.Water is collected in the vertical pipe connected to the intake pipes,and then conveyed by gravity.A gangway connects the top of dams and control room over the well.The values are operated from the control room.
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