Unit 1 - Intake of water, Pumping and gravity scheme.ppt
- 1. By C.Subha Assistant Professor (SG) Department of Civil Engineering, Ramco Institute of Technology, Rajapalayam INTAKE STRUCTURES
- 2. Water supply -intake structures -Functions and drawings - Pipes and conduits for water- Pipe materials -Hydraulics of flow in pipes -Transmission main design -Laying, jointing and testing of pipes -Drawings appurtenances - Types and capacity of pumps –Selection of pumps and pipe materials.
- 3. Structures used for withdrawing water from the source are called intakes. Intakes collect water from the source and convey it to the purification plants for treating water before supplying it to the consumer through distribution pipes. The structure may be stone, brick, RCC, or Concrete block masonry
- 5. 1. The location of the intake structure should be nearer to the treatment plant, in order to reduce the cost of conveyance water. 2. The location of the intake should be selected in a place, where there the fewer impurities present. 3. The intake should be selected at a place from where the water can be taken during the driest season of the year. 4. The intake location should have the possibility for future expansion and addition without much increase in cost. 5. The intake should not be located downstream of the disposal point of sewage. 6. It should be located in such a way that it should not be affected by heavy flood 7. The intake should not be located near the navigation channels such as Harbor etc. 8. It should not interfere with river traffic if any.
- 6. Simple submerged Intake Intake Tower or River Intake Structures Wet Intake Towers Dry Intake Towers Reservoir Intake Variable depth lake water intake Multi level intake Canal Intake Structures.
- 7. A submerged intake structure consists of a simple concrete block supporting the starting end of the withdrawal pipe. The withdrawal pipes are generally taken up to the sump well at the river bank from where the water is lifted by pumps. The intake opening is generally covered by a screen so as to prevent the entry of debris, ice, etc., into the withdrawal pipe. The intake opening is generally kept about 2 to 2.5 m above the bottom of the lake and thus avoids the entry of silt and sediment.
- 9. Intake towers are generally used on large projects and on rivers or reservoirs where there are large fluctuations in water level. Gate-controlled openings at various levels called ports are generally provided in these concrete towers which may help in regulating the flow through the towers and permit some selection of the quality of water to be withdrawn. Accesses to these towers are generally provided for operating the gates, etc., by means of a footbridge from the tower up to the dam or up to the river banks.
- 10. Types of Intake Towers Wet intake Towers Dry Intake Towers
- 11. The wet intake is that type of intake tower in which the water level is practically the same as the level of water in the river. It is sometimes known as JACK Well and it is most commonly used. It consists of a concrete circular shell filled with water up to the level in the source and has a vertical inside shaft that is connected to the withdrawal pipe. Gate-controlled openings at various levels called ports are generally provided in these concrete towers which may help in regulating the flow through the towers and permit some selection of the quality of water to be withdrawn. Accesses to these towers are generally provided for operating the gates, etc., by means of a footbridge from the tower up to the dam or up to the river banks.
- 13. The essential difference between a dry intake and wet intake is that in a wet intake the water enters from the entry ports in to the intake and then it enters in to the conduit pipe through separate gate controlled openings whereas in a dry intake water is directly drawn in to the withdrawal pipe through the gate entry openings. A dry intake will therefore have no water inside the intake if its gates are closed whereas the wet intake will be full of water even if its gates are closed.
- 15. When the flow in the river is not available throughout the year. a dam is constructed across it to store water in the reservoir so formed. The reservoir intakes are practically similar to the river intake except that these are located near the upstream face of the Dam where the maximum depth of water is available. The access to intake is provided through a footbridge. The water level will be the same as the reservoir level. Water available at various levels are withdrawn using withdrawal ports at various levels through gate valve control operated at the top.
- 17. In canal intake structure, the intake well is generally located in the bank of the canal and water enters the chamber through the inlet pipe. The inlet pipe is covered with a fine screen. The top of the screen is generally provided at minimum water level in the canal and bottom is about 0.15 m above the canal bed to avoid entry of bed load. The inlet end is of bell mouth shape with perforation of fine screen on its surface.
- 18. The flow velocity through the out let is generally 1.5 m/sec, and this helps in determining the area and diameter at the withdrawal pipe. The area of the coarse screen is designed by limiting the flow velocity to as low as 0.15m/sec. The flow velocity through the bell mouth is limited to about 0.3 m/sec.
- 20. Gravitational System • In this system, the water from high levelled source is distributed to the consumer at lower levels by the action of gravity without any pumping. • For proper functioning of this system the difference of head available between the source and localities must be sufficient enough as to maintain the adequate pressure level. • The gravitational system is designed so as to leave only minimum permitted available head to the consumer.
- 21. PUMPING SYSTEM • In this system the treated water is directly pumped into the distribution main without storing it anywhere. • For this reason, this system is also sometimes called pumping without storage system. • High lift pumps are required in this system which have to operate at variable speeds so as to meet variable demand of water. • If the power supply fails there will be complete stoppage of water supply and if by chance fire breaks out such a time it will bring disaster. • This method is generally not used.
- 22. COMBINED GRAVITY AND PUMPING SYSTEM • In this system the treated water is pumped at a constant rate and stored in a elevated distribution reservoir from where it distributed to the consumer by the action of gravity. • Sometimes the entire water is first of all pumped in to the distribution reservoir and many a times it is pumped into the distribution main and reservoir simultaneously. • This method thus combines the pumping and gravity flow and is sometimes called pumping with storage system.