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Collection and Conveyance of Water


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Collection and Conveyance of Water

BTCI05006/ MBCI05006

Published in: Education
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Collection and Conveyance of Water

  1. 1. Collection & Conveyance of Water Unit-II BTCI05006/ MBCI05006
  2. 2. Collection & Conveyance of Water Unit-II
  3. 3. Syllabus • Collection and conveyance of water: Types of intake structure, design of intake structure, estimation of fluid flows, engineering requirements of conduits with respect to their performance, types of conveyance system, hydraulic design of conveyance conduits, various materials of pipes, appurtenances, and issues associated with conveyance of water. • Pumps for lifting of water: Types of pumps, selection of pumps, design of pumping main for conveyance of water, economical diameter of pumping main, pumping station
  4. 4. Intake Structures
  5. 5. Introduction • In any water supply project the first step is to select the source of water from which water is drawn. The device Installed for the purpose of drawing water from the source of water are called Intakes
  6. 6. Intake Structures
  7. 7. Intake Structure • The basic function of intake structure is to help in safely withdrawing water from the source and then to discharge this water in to the withdrawal conduit, through which it reaches the water treatment plant. • It is constructed at the entrance of the withdrawal conduit and thereby protecting it from being damaged/clogged by ice,debris. • Some times from reservoirs where gravity flow is possible, water is directly transmitted to the treatment through intake structure. • If gravity flow is not possible, water entering intake structure is lifted by pumps and taken to the treatment plant.
  8. 8. Intake Structure
  9. 9. Intake Structure
  10. 10. Selecting Location Of Intake Structure • Site should be near the treatment plant to reduce conveyance cost. • Intake must be located in the purer zone of the source so that best quality water is withdrawn from source to reduce the load on the treatment plant. • Intake must never be located in the vicinity of waste water disposal point. • Intake must never be located near the navigation channels so as to reduce chances of pollution due to waste discharge from ships. • The site should be such as to permit greater withdrawal of water, if required in future.
  11. 11. Selecting Location Of Intake Structure
  12. 12. Selecting Location Of Intake Structure • Intake must be located at a place from where it can draw water even during the driest period of the year. • The intake site should remain easily accessible during floods and should not get flooded. • In meandering rivers, the intakes should not be located on curves or atleast on sharp curves.
  13. 13. Selecting Location Of Intake Structure
  14. 14. Intakes for Collecting Surface Water Types of Intakes According to type of source • River Intake • Canal Intake • Reservoir Intake • Lake Intake According to position of Intake • Submerged Intake • Exposed Intake According to presence of water in the tower • Wet Intake • Dry Intake
  15. 15. Intakes for Collecting Surface Water According to position of Intake • (a) Submerged Intake • (b) Exposed Intake • The submerged Intake structures are those which are constructed entirely under water. They are less expensive to construct but are difficult to maintain. Such intakes are commonly used to obtain water from lakes • The Exposed intakes is in the form of well or tower constructed near the bank of river or in some cases even away from the bank of river. They are more common due to ease in operation and maintenance
  16. 16. Intakes for Collecting Surface Water According to presence of Water in the tower Wet Intake Dry Intake A Wet intake is that type of the Intake tower in which the water level is practically the same as the water level of the source of supply. Such Intakes are also called as JackWell and is most commonly Used In Dry Intake There is no water in the intake tower. Water enters through entry port directly in to conveyance pipes. The dry Intake tower is simply used for the operation of valves.
  17. 17. Simple Lake Submerged Intakes • It consists of a simple concrete block or a rock filled timber crib supporting the starting end of the withdrawal pipe. • The intake opening is generally covered by screen so as to prevent the entry of debris, ice etc.. in to the withdrawal conduit. • In lakes, where silt tends to settle down , the intake opening is generally kept at about 2 to 2.5m above the lake bed level to avoid entry of silt. • They are cheap & do not obstruct navigation • They are widely used for small water supply projects drawing water from streams or lakes having a little change in water level through out year. • Limitation is that they are not easily accessible for cleaning & repairing.
  18. 18. Simple Submerged Intakes
  19. 19. Rock Filled Timber Crib -Submerged Intake
  20. 20. Intakes for Collecting Surface Water River Intake A River Intake is located on the upstream side of the city to get comparatively better quality of water. They are either located sufficiently inside the river so that necessary demand of water can be met in all the seasons of the year. The intake tower permits the entry of water through several entry ports located at various levels to cope with fluctuations in the water levels during different seasons. This are also called as penstocks. The penstocks are covered with suitable design screens to prevent entry of floating impurities.
  21. 21. Intake Towers • They are widely used on large water supply projects drawing water from rivers or reservoirs having large change in water level. • Gate controlled openings called Ports are provided at various levels in these concrete towers to regulate the flow. • If the entry ports are submerged at all levels, there is no problem of any clogging or damage by ice or debris etc.. • There are two major types of intake towers: (a)Wet intake towers (b) Dry intake towers
  22. 22. Wet Intake Towers • It consist of a concrete circular shell filled with water up to the reservoir level and has a vertical inside shaft which is connected to the withdrawal pipe. • The withdrawal pipe may lie over the bed of the rivers or may be in the form of tunnels below the river bed. • Openings are made in to the outer concrete shell as well as, in to the inside shaft. • Gates are usually placed on the shaft, so as to control the flow of water in to the shaft and the withdrawal conduit. • The water coming out of the withdrawal pipe may be taken to pump house for lift (if treatment plant is at high elevation) or may be directly taken to treatment plant (at lower elevation).
  23. 23. Wet Intake Towers
  24. 24. Dry Intake Towers • The water is directly drawn in to the withdrawal conduit through the gated entry ports. • It has no water inside the tower if its gates are closed. • When the entry ports are closed, a dry intake tower will be subjected to additional buoyant forces. • Hence it must be of heavier construction than wet intake tower. • They are useful since water can be withdrawn from any selected level of the reservoir by opening the port at that level.
  25. 25. Dry Intake Towers
  26. 26. Intake
  27. 27. Intake • There are two types of intakes as under • (i) Dry Intake Tower • In dry intake tower the entry ports are directly connected with the withdrawal conduit and water inside the tower when gates are in a closed position. Dry Intake tower has a merit that the intake tower being dry is made accessible for inspection and operation besides that the water can be withdrawn from any level by opening the port at that level. • However, dry intake tower is massive in structure, than wet intake to withstand additional buoyant forces to which it is subjected when the port gates are closed.
  28. 28. Dry Intake Tower
  29. 29. Dry Intake Tower
  30. 30. Dry Intake Tower
  31. 31. Intake Wet Intake Tower • A wet intake tower has entry ports at various levels and the vertical shaft is filled with water up to reservoir level. It differs from the dry intake tower is that the water enters from the ports into the tower and then into the withdrawal conduict through separate gated openings. As such it consists of a circular shell made of concrete filled with water up to reservoir level, housing another inside shaft directly connected to the withdrawal conduit. It is less costly to construct and is usually not subjected to flotation and certain other stress may not be the consideration.
  32. 32. Wet Intake Tower
  33. 33. Trash Racks • Trash rack is defined as a screen or grating provided at the entrance of intake to prevent entry of debris. Trash racks usually consists of trash sections 1.5 to 2 m wide and not too long for handling, made up of mild steel flats on edge 5 to 15 cm. Coarse trash racks are provided near the ports to prevent large drift, such as cakes of ice, roots, trees and timber from being drawn into the intake.
  34. 34. Trash Racks • In some part of the intake fine trash racks are provided to protect the machine & machine parts through which water flows. In cold region, trash racks is often clogged with fragile ice. Electrical heating for small trash racks are provided to prevent ice formation on the racks. • The floating debris accumulated, as are denied entry into the intake, are removed with the help of power driven rack-rakes.
  35. 35. Trash Racks
  36. 36. River Intake Structures • They are generally constructed for withdrawing water from almost all rivers. • They can be classified in to two types (1) Twin well type of intake structure (2) Single well type of intake structure
  37. 37. Twin Well Type Intakes • They are constructed on almost all types of rivers, where the river water hugs the river bank. • A typical river intake structure consists of 3 components: (a) An inlet well (b) An inlet pipe (intake pipe) (c) A jack well • Inlet well is usually circular in c/s, made of masonry or concrete. • Inlet pipe connects inlet well with jack well. It has a min dia of 45cm, laid at slope of 1 in 200. Flow velocity through it<1.2m/s • Water entering jack well is lifted by pumps & fed into the rising main • Jack well should be founded on hard strata having B.C> 450 kN/m2.
  38. 38. Twin Well Type Intakes
  39. 39. Single Well Type Intakes • No inlet well & inlet pipe in this type of river intake. • Opening or ports fitted with bar screens are provided in the jack well itself. • The sediment entering will usually be less, since clearer water will enter the off-take channel. • The silt entering the jack well will partly settle down in the bottom silt zone of jack well or may be lifted up with the pumped water since pumps can easily lift sedimented water. • The jack well can be periodically cleaned manually, by stopping the water entry in to the well.
  40. 40. Single Well Type Intakes
  41. 41. Single Well Type Intakes
  42. 42. Canal Intakes
  43. 43. Canal Intakes • In case of a small town a nearby Irrigation Canal can be used as the source of water. The Intake Well is generally located in the bank of the Canal. Since water level is more or less constant there is no need of providing inlets at different depth. It essentially consist of concrete or masonry intake chamber or well. • Since the flow area in the canal is obstructed by the construction of Intake well, the flow velocity in the canal decreases. So the canal should be lined on the Upstream & Downstream side of the intake to prevent erosion of sides and bed of channel
  44. 44. Intakes For Sluice Ways Of Dams
  45. 45. Intakes For Sluice Ways Of Dams
  46. 46. Intakes For Sluice Ways Of Dams
  47. 47. Intakes for Reservoirs • When the flow in the river is not guaranteed throughout the year, a dam is constructed across the river to store the water in the reservoir so formed. • Reservoir Intakes essentially consists of an Intake tower constructed on the slope of Dam at such a place where Intake can draw water in sufficient quantity even in the driest period. Intake pipes are fixed at different levels, so as to draw water near the surface in all variations of water levels.
  48. 48. An intake structure constructed at the entrance of conduit and thereby helping in protecting the conduit from being damaged or clogged by ice , trash, debris, etc.., can vary from a simple Concrete block supporting the end of the conduit pipe to huge concrete towers housing intake gates, Screens, pumps, etc.. and even sometimes, living quarters and shops for operating personnel.
  49. 49. Lake Intake • Lake Intake are mostly submerged intake. These Intakes are constructed in the bed of lake below the low water level so as to draw water even in dry season. It mainly consist of a pipe laid in the bed of the lake. One end of the pipe which is in middle of the lake is fitted with bell mouth opening covered with a mesh and protected timber or concrete crib. The water enters in the pipe through the bell mouth opening and flows under gravity to the bank where it is collected in a sump well and then pumped to the treatment plant for necessary treatment.
  50. 50. Submerged Intake
  51. 51. Advantages Intakes • No Obstruction to navigation • No danger of floating bodies • No ice trouble
  52. 52. Intake
  53. 53. Intake • The general requirement of an Intake Structure are: Structural Stability • The Intake structure is stable to resist water and wave thrust besides wind pressure when reservoir is empty as also against the shock of earthquakes. Hydraulic efficiency • There is smooth entry into the water conductor system to ensure gradual transformation of static head to conduct velocity so as to involve hydraulic losses.
  54. 54. Intake
  55. 55. Intake Velocity Limitation • The velocity through trash rack gates and ports is within economic and safe limits. Operational efficiency • The intake and the equipments are such as to prevent/ minimize ice, floating trash and coarse sediment entering the water conductor system to ensure good operational efficiency.
  56. 56. Intake • The main components of an irrigation intake structure are (i) Trash rack and supporting structure (ii) Bell mouth entrance with transition and rectangular circular opening, and (iii) Gate slot closing devices with air vents.
  57. 57. Trash Rack
  58. 58. Bell Mouth Entrance
  59. 59. Gate slot closing devices with air vents.
  60. 60. Intake Function of Intakes • Intake structure serve to permit withdrawal of water in the reservoir over a predetermined range of reservoir levels to the outlet. • The other functions served by an intake are to support necessary auxiliary appurtenances such as trashrack, fish screens and bypass devices, etc.,.
  61. 61. Intake
  62. 62. Intake
  63. 63. Intakes
  64. 64. Intake
  65. 65. Intake
  66. 66. Intake
  67. 67. Intake Run-of-River Intakes • In a run-of-River plants, intake is apparent to power house and draws water from the river without any appreciable storage upstream of the diversion structure. Characteristics of river flows., the intake is designed to withstand high peaks and short duration flood flows and high sediment loads. The bell mouth entrance is essentially provided with trash racks.
  68. 68. Run-of-River type Intake
  69. 69. Intake Canal Intake • It is also a variant of the run-of-river intake, that is provided adjacent to the diversion weir/ barrages to admit water into the canal. It is designed to function under low heads and the topography and geology permits straight reach suitable for it. Sediment excluder is an essential component of the intake. The crest of the intake is generally raised to prevent entry of coarse fraction of bed load into the canal.
  70. 70. Canal Intake
  71. 71. Intake Reservoir Type Intakes • Intake tower classified as Submerged, dry and wet intakes fall in this category. (i) Submerged Intake • An Intake Structure which remains entirely under water during its operation is termed as submerged intake. It is provided where the structure serves only as an entrance to the outlet conduct and where ordinarily cleaning of the trash is not required. The conduct intake may be inclined, vertical or horizontal in accordingly with the intake requirements. . An Inclined Intake may be provided with gates and operated on the upstream slopes of a low dam.
  72. 72. Submerged Intakes
  73. 73. Submerged Intake
  74. 74. Intake Intake tower • An Intake tower is used to draw water from the reservoir in which there are huge fluctuations in water level or quality water is to be drawn at the desirable depth or both. It Consist of an elaborate exposed or tower like structure rising above maximum reservoir level and closely located to the dam body or the bank of the stream so as to be approached by a connecting bridge of minimum span.
  75. 75. Intake
  76. 76. Intake • The Intake tower consist of circular concrete structure provided with openings or ports for water entry fitted with trash racks to prevent the entry of debris and ice large enough to injure the equipment and gates that control the flow through intakes into the feeding conduct outlet. • It has a merit that best quality of water available at different depths at different seasons of the year can be drawn through port openings at different elevations.
  77. 77. Design of Intake • An Intake should be designed and constructed on the basis of following points • Sufficient factor of safety should be taken so that intake work can resist external forces caused by heavy waves and currents, Impact of floating and submerged bodies, ice pressure etc.. • Intake should have sufficient self weight, so that it may not float by the up trust of water and washed away by the current • If Intake work is constructed in navigation channels, it should be protected against the impact of the moving ships by cluster of pile around • The foundation of Intake should be taken sufficient deep so that they may not be undermined and current may not overturn the structure.
  78. 78. Design of Intake • To avoid the entrance of large and medium objects and fishes screens should be provided on the Inlet, sides • The Inlet should be of sufficient size and should allow required quantity of water. • The positions of Inlet should be such that they can admit water in all seasons near the surface where quality of water is good. • Number of Inlets should be more so that if any one is blocked, the water can be drawn from others. The inlets should be completely submerged so that air may not enter the suction pipe.
  79. 79. Canal Intake
  80. 80. Design procedure for Intakes Canal Intake • If Population is given and rate of water Supply is given the discharge required by the city/town can be found • Q= Population x Rate of Supply Design of Coarse Screen • Generally the coarse screens are made of vertical bars of 15 to 20 mm dia and are spaced at 20 to 50 mm Centre to Centre • Velocity through the screens is assumed to bearound 0.15 m/sec
  81. 81. Canal Intake
  82. 82. Design procedure for Intakes • Area of Screens= Discharge Velocity through screens Q= A x V Height of the screen is found assuming that the bottom of the screen is kept 0.15 m above canal bed and also considering the minimum water level in the canal. After finding height, length of the screen opening can be found out. Length of screen = Area Height
  83. 83. Canal Intake
  84. 84. Design procedure for Intakes • Number of bars required can be found after assuming the diameter and spacing of the bars. • Total length of screen will be length of opening + length occupied by bars . Design of bell mouth entry • To find the area of bell mouth entry first assume thevelocity through bell mouth generally around 0.3 to 0.35 m/sec . After getting the area find the dia of bell mouth
  85. 85. Canal Intake
  86. 86. Design Procedure for Intakes Design of Intake Conduit • Assume the velocity of flow through conduit, generally 1.0 to 1.5 m/sec • Find , A= Q V Then Using Hazen William formula, find the head loss and the slope required, Charts can be used.
  87. 87. River Intake • First Design the Intake Well. Dia is generally between 4 to 7.5 m. Using discharge find the area and the diameter. • If rectangular find length and width after finding the length and width of the screen required. • Design procedure for coarse screen and outlet conduct is almost same as canal Intake.
  88. 88. Example • Design a bell mouth canal intake for a city of 70,000 persons drawing water from a canal which runs only for 10 hrs. a day with a depth of 1.6 m. Also calculate the head loss in the intake conduit if the treatment plant is 0.5 km away. Assume average consumption per person= 160 l/d. Assume the velocity through the screens and bell mouth to be 0.15 m/s and 0.3 m/s respectively.
  89. 89. Example • Discharge required by the city = 70000 x 160 (Population x rate of supply) = 11,200,000 11.2 MLD (Million litre per day) Since the canal only runs for 10 hrs. a day, this whole daily flow is required to be drain in 10 hrs.
  90. 90. Example Therefore the Intake load= 11.2 = 1.12 ML/Hour 10 = 1.12 x 10 6 m3 / hr.... 10 3 1.12 x 10 3 m3 /sec 60 x 60 = 0.311 m3 /sec
  91. 91. Example Design of Coarse Screen • Area of Coarse Screen = Discharge Velocity through the screen Velocity through the screen = 0.15 m /sec Area of the coarse screen = 0.311 = 2.075 m 2 0.15 Assume the minimum water level is 0.3 m below the normal water level. The bottom of the screen is kept at 0.15 m above the bed level. The top of screen is kept at minimum level Therefore available height= 1.6 – 0.3- 0.15 = 1.15 m Minimum length of the screen= 2.075 = 1.80 m 1.15
  92. 92. Canal Intake
  93. 93. Example Assume the clear opening between vertical bars to be 30 mm each we have • Number of opening = 1.8 = 60 0.03 Therefore no of bars= 59 Assume the dia of bar as 20 mm Length occupied by the bar of 20 mm = 59 x 0.02 = 1.18 m Therefore length of screen= 1.8 + 1.18 = 2.98 Say 3 m Hence provide coarse screen of length 3.0 m and height 1.15 in rectangular intake well
  94. 94. Canal Intake
  95. 95. Example Design of Bell Mouth Entry • Area of Bell mouth entry = Discharge Velocity through the bell mouth = 0.311 0.3 = 1.037 m 2 Diameter d of the bell mouth entry as = Π d 2 = 1.037 4
  96. 96. Example • D={ 4 x 1.037} 1/2 Π = 1.15 m If the dia of small holes in the screen is assumed to be 15 mm (10 to 20mm). Then area of each hole= Π x (0.015) 2 4 = 1.767 x 10 -4 Therefore number of holes on the bell mouth = Area of bell mouth Area of one hole = 1.037 1.767 x 10 -4 = 5868.2 Say 5869
  97. 97. Canal Intake
  98. 98. Example Design of Intake Conduit • Assume Velocity of flow in the conduit as 1.5 m/sec • Area of conduit required = Discharge Velocity = 0.311 = 0.2073 m 2 1.5 Dia of pipe D will be Π D2 = 0.2073 4= 0.514 Say 0.55 m
  99. 99. Canal Intake
  100. 100. Example • Flow velocity through this 0.55 m dia conduit will be = V = Q = 0.311 = 1.31 m /sec A = Π x (0.55) 2 4 assume velocity of 1.5 m /sec
  101. 101. Example • Head loss through the conduit up-to treatment plant is calculated by using Hazen William’s eq n • V= 0.85 CH R 0.23 S 0.54 • Where , • CH= Coefficient of the Pipe • = 130 for Cast Iron Pipe • R= Hydraulic mean depth • = d/4 ( for pipe running full) • = 0.55 = 0.138 m 4 V= Velocity S= Slope
  102. 102. Example • Therefore, • 1.5 = 0.85 x 130 x (0.138 ) 0.63 S 0.64 • S 0.54 = 150 0.85 x 130 x (0.138) 0.63 = 0.047 S= (0.047) 1 /0.54 = 3.51 x 10 -3 Or 1 in 284.73 S= HL = Head Loss L Length of Pipe Length of pipe is equal to the distance of Intake from treatment plants 0.5 km = 500 m HL= 3.51 x 10 -3 x 500 = 1.755 m
  103. 103. Example • Design a bell mouth canal Intake for a City of 1,00,000 persons drawing water from a canal which runs for 10 hrs.. a day with a depth of 2 m. Also calculate the head loss in the intake conduit if the treatment works are 1 km away. Draw a neat sketch of canal Intake. Assume average consumption per person= 150 l/day. Assume the velocity through the screens and bell mouth to be less than 15 cm/sec and 35 cm/sec
  104. 104. Canal Intake
  105. 105. Example Discharge through Intake Daily Discharge= 150 x 1,00,000= 15,000,000 l/day • Since the canal runs only for 10 hrs. per day. • Intake Load/hr = 15,000,000 = 15,000,00 lit/hr 10 = 15,00 m3 /hr.... Q= 1500 = 0.4166 m3 /sec 60 x 60
  106. 106. Example Area of Coarse Screen I front of Intake • Area of Screen= 0.4166= 2.777 m 2 0.15 Let the area occupied by solid bars by 30 % of the total area Therefore the actual area= 3.96 m 2 Let us assume minimum water level at 0.3 m below normal water level. Also let us keep bottom of the screen at 0.15 m above canal bed and top of screen at the minimum water level. Available height of screen= 2- 0.3-0.15 = 1.55 m Required length of screen= 3.96 = 2.55 m 1.55 Hence provide a length of 2.6 m Hence provide a screen of 1.55 x 2.6 m
  107. 107. Example Design of Bell Mouth Entry • Area of Bell mouth Ab= 0.4166 = 1.301 m 2 0.32 Dia db= { 1.301 x 4}1/2 = 1.65 m 3.14 Hence provide a bell mouth of 1.7 m dia
  108. 108. Example Design of Intake Conduit • Let us assume a velocity of 1.5 m/sec in the conduit • Dia of conduit D ={ 0.4166 x 4 } 1/2 = 0.35 m 1.5 x 3.14 However, provide 0.5 m dia, conduit, so that actual velocity of flow is V = 0.4166 x 4 = 2.12 m/sec 3.14 x (0.5) 2
  109. 109. Example For head loss through the conduit • V= 0.849 C R 0.63 S 0.54 • C= 130 • R= D/4 = 0.5 /4 = 0.125 • Hence Slope S of the energy line, • 2.12 = 0.849 (130) (0.125) 0.63 S 0.54 • S= 7.533 x 10 -3 • S= HL/L • HL= S x L= 7.53 m
  110. 110. Canal Intake
  111. 111. Conveyance of Water • Water is drawn from the sources by Intakes. After it’s drawing the next problem is to carry it to the treatment plant which is located usually within city limits. Therefore after collection, the water is conveyed to the city by mean of conduits. If the source is at higher elevation than the treatment plant, the water can flow under gravitational force. • For the conveyance of water at such places we can use open channel, aqueduct or pipe line, Mostly it has been seen that the water level in the source is at lower elevation than the treatment plant, In such case water can be conveyed by means of closed pipes under pressure
  112. 112. Conveyance of Water
  113. 113. Conveyance of Water • If the source of supply is underground water, usually there is no problem as, these sources are mostly in the underground of the city itself. The water is drawn from the underground sources by means of tube-wells and pumped to the over-head reservoirs, from where it is distributed to the town under gravitational force. Hence at such places there is no problem of conveyance of water from sources to the treatment works.
  114. 114. Conveyance of Water
  115. 115. Conveyance of Water • In case of sources of water supply is river or reservoir and the town is situated at higher level, the water will have to be pumped and conveyed through pressure pipes. If the source is available at higher level than the town, it is better to construct the treatment plant near the source and supply the water to the town under gravitational forces only,
  116. 116. Conveyance of Water
  117. 117. Conveyance of Water Open Channels • These ae occasionally used to convey the water from the source to the treatment plant. These can be easily and cheaply constructed by cutting in high grounds and banking in low grounds. • The channels should be lined properly to prevent the seepage and contamination of water. As water flows only due to gravitational forces, a uniform longitudinal slope is given. The hydraulic gradient line in channels should not exceed the permissible limit otherwise scouring will start at the bed and water will become dirty. In channel flow there is always loss of water by seepage and evaporation,
  118. 118. Open Channels
  119. 119. Conveyance of Water Aqueducts • Aqueducts is the name given to the closed conduit constructed with masonry and used for conveying water from source to the treatment plant or point of distribution. Aqueduct may be constructed with bricks, stones or reinforced cement concrete. In olden days rectangular aqueduct were used, but now a days horse-shoe or circular section are used. These aqueduct are mostly constructed with cement concrete The average velocity should be 1 m/sec
  120. 120. Aqueducts
  121. 121. Conveyance of Water Tunnels • This is also a gravity conduit, in which water flows under gravitational forces. But sometimes water flows under pressure and in such cases these are called pressure tunnels. Grade tunnels are mostly constructed in horse-shoe cross-section, but pressure tunnel have circular cross-section. In pressure tunnels the depth of water is generally such that the weight of overlying material will be sufficient to check the bursting pressure. Tunnels should be water tight and there should be no loss of water.
  122. 122. Tunnels
  123. 123. Conveyance of Water Flumes • These are open Channels supported above the ground over trestles etc.. Flumes are usually used for conveying water across valleys and minor low lying areas or over drains and other obstruction coming in the way. Flumes may be constructed with R.C.C, wood or metal. The common section are rectangular and circular.
  124. 124. Flumes
  125. 125. Conveyance of Water Pipes • These are circular conduits, in which water flows under pressure. Now a days pressure pipes are mostly used at every places and they have eliminated the use of channels, aqueducts and tunnels to a large extent. These are made of various materials like cast Iron, wrought Iron, steel, cement Concrete, asbestos, cement, timber, etc.. In the town pips are also used for distribution system. In distribution system pipes of various diameter, having many connections and branches are used. Water pipe lines follow the profile of the ground water and the location which is most economical, causing less pressure in pipes is chosen.
  126. 126. Pipes
  127. 127. Conveyance of Water • The cost of pipe line depends on the internal pressure to bear and the length of pipe line. Therefore as far as possible the hydraulic line is kept closer to the pipe line. In the valley or low points a scour valve is provided to drain the line and removing accumulated suspended matter. Similarly at high points air relief valves are provided to remove the accumulated air. To prevent the bursting of pipes due to water hammer, surge tanks or stand pipes are provided at the end of pipes.
  128. 128. Surge Tank or Surge Chamber
  129. 129. Conveyance of Water
  130. 130. Surge Tank or Surge Chamber
  131. 131. Conveyance of Water The selection of material for the pipes is done on the following points • Carrying Capacity of the pipes • Durability and life of the pipe • Type of water to be conveyed and its corrosive effect on the pipe material. • Availability of funds • Maintenance cost, repair etc.. • The pipe material which will give the smallest annual cost or capital cost will be selected, because it will be mostly economical.
  132. 132. Conveyance of Water
  133. 133. Conveyance of Water Following types of pipes are commonly Used • Cast Iron Pipes • Wrought Iron pipes • Steel Pipes • Concrete Pipes • Cement lined Cast Iron Pipes • Plastic or PVC pipes • Asbestos cement pipes • Copper and lead pipes • Wooden pipes • Vitrified Clay pipes
  134. 134. Conveyance of Water • Out of the types mentioned, plastic or PVC and Asbestos cement pipes, wooden pipes are not generally used for conveyance of water. They are used in house drainage or water connection within individual house.
  135. 135. Cast Iron Pipes • Cast – Iron Pipes are mostly used in water supply schemes. They have higher resistant to corrosion, therefore have long life about 100 years. • Cast Iron pipes are manufactured in lengths of 2.5 m to 5.5 m. The fittings of these pipes are also manufactured in sand molds having core boxes. These fittings are also weighed, coated with coal tar and finally tested. Cast-Iron pipes are joined together by means of Bell and Spigot, Threaded or flanged Joints
  136. 136. Cast Iron Pipes
  137. 137. Conveyance of Water Advantages of CI Pipes • Ease in jointing the pipes • Can withstand high Internal pressure • Have a very long design life. (100 years) • They are less prone to corrosion.
  138. 138. Conveyance of Water Dis-advantages of CI Pipes • They are heavy and difficult to transport • Length of pipe available as less (2.5 to 5.5m) so more joints are required for laying the pipes so chances of leakage also Increases. • They are brittle so they break or crack easily.
  139. 139. Conveyance of Water Wrought Iron Pipes • Wrought Iron Pipes are manufactured by rolling the flat plates of the metal to the proper diameter and welding the edges. If compared with cast Iron, these are more lighter, can be easily cut, threaded and worked, give neat appearance if used in the interior works. But it is more costly and less durable than cast iron pipes. These pipes should be used only inside the buildings, where they can be protected from corrosion. Wrought Iron pipes are joined together by couplings or screwed and socketed joints. To Increase the life of these pipes sometimes these are galvanized with zinc.
  140. 140. Wrought Iron Pipes
  141. 141. Conveyance of Water Steel pipes • The Construction of these pipes is similar to wrought iron pipes, it is occasionally used from main lines and at such places where pressure are high and pipe dia is more. Steel pipes are more stronger, have very light weight and can withstand high pressure than cast iron pipes. They are also cheap, easy to construct and can be easily transported.
  142. 142. Steel pipes
  143. 143. Conveyance of Water • The disadvantages of these pipes is that they cannot withstand external load, if partial vacuum is created by emptying pipe rapidly, the pipe may be collapsed or distorted. These pipes are much affected by corrosion and are costly to maintain The life of these pipes is 25 to 50 years, which is much shorter as compared to cast Iron Pipes Steel pipes are not used in distribution system, owing to the difficulty in making connections. • The joints in steel pipes may be made of welding or riveting, longitudinal lap joints are made In riveted steel pipes up to 120 cm dia
  144. 144. Conveyance of Water Concrete Pipes • These pipes may be precast or Cast-in-situ plain concrete pipe may be used at such places where water does not flow under pressure, these pipes are jointed with Bel &Spigot Joints. Plain Concrete pipes are up to 60 cm dia only, above it these are reinforced.
  145. 145. Concrete Pipes
  146. 146. Conveyance of Water Advantages of R.C.C Pipes • Their life is more about 75 years • They can be easily constructed in the factories or at site • They have least coefficient of thermal expansion than other types of pipes . Hence they do not require expansion joints • Due to their heavy weight, when laid under water, they are not affected by buoyancy, even when they are empty. • They are not affected by atmospheric action or ordinary soil under normal condition.
  147. 147. Conveyance of Water Disadvantages of R.C.C Pipes • They are affected by acids, alkalis and salty waters • Their repairs are very difficult. • Due to their heavy weight, their transportation and laying cost is more. • It is difficult to make connections in them • Porosity may cause them to leak.
  148. 148. Pipe Joints • For the facilities in handling, transporting, and placing in position, pipes are manufactured in small lengths of 2 to 6 meters. These small pieces of pipes are then joined together after placing in position to make one continuous length of pipe. • The design of these joints mainly depends on the material of the pipe, internal water pressure and the condition of the support • The bell and spigot joints, using lead as filling material is mostly used for cast Iron pipes. For Steel pipes welded, riveted, flanged or screwed joints my be used.
  149. 149. Various types of Joints which are mostly used, are as follows • Spigot and Socket Joints or Bell & Spigot Joints • Expansion Joints • Flanged Joints • Mechanical Joints • Flexible Joints • Screwed Joints • Collar Joints • A.C. Pipe Joints
  150. 150. Spigot and Socket Joints • This types of joints is mostly used for cast iron pipes For the construction of this joint the spigot or normal end of one pipe is slipped in socket or bell mouth end of the other pipe until contact is made at the base of the base of the bell.
  151. 151. Spigot and Socket Joints
  152. 152. Spigot and Socket Joints • After this hemp or yarn is wrapped around the spigot end of the pipe and is tightly filled in the joint by means of yarning iron up to 5 cm depth. The hemp is tightly packed to maintain regular annular space and for preventing jointed material from falling inside the pipe. After packing of hemp & gasket or joint runner is clamped against the outer edge of the bell.
  153. 153. Spigot and Socket Joints • Sometimes wet clay is used to make tight contact between the runner and the pipe so that hot lead may not run out of the joint spaces. The molten lead is then poured into V-shaped opening left in the top by the clamp joint runner. The space between the hemp yarn and the clamp runner is removed, the lead which shrink while cooling, is again tightened by means of chalking tool and hammer. Now a days in order to reduce the cost of lead certain patented compounds of sulphur and other materials and other materials are filled in these joints.
  154. 154. Expansion Joints • This joint is used at such places where pipes expand or contract due to change in atmospheric temperature and thus checks the setting of thermal stresses in the pipes. In this joints the socket end is flanged with cast iron follower ring, which can freely slide on the spigot end or plane end of other pipes. An elastic rubber gasket is tightly pressed between the annular spaces of socket by means of bolts. In the beginning while fixing the follower ring some space is left between the socket base and the spigot end for the free movement of the pipes under variation of temperature. In this way when the pipe expands the socket end moves forward and when the pipe contracts, it moves backward in the space provided for it. The elastic rubber gasket in every position keeps the joint water tight.
  155. 155. Expansion Joints
  156. 156. Flanged Joint • This joint is mostly used for temporary pipe lines, because the pipe line can be dismantled and again assembled at other places. • The pipe in this case has flanges on its both ends, cast, welded or screwed with the pipe. The two ends of the pipes which are to be jointed together are brought in perfect level near one another and after placing of washer or gasket of rubber, canvas, copper or lead between the two ends of flanges is very necessary for securing a perfect water-tight joints. These joint cannot be used at places where it has to bear vibration of pipes etc..
  157. 157. Flanged Joint
  158. 158. Flexible Joints • Sometimes this joint is also called Bell & Socket or Universal Joint. This joint is used at such places where settlement is likely to occur after the lying of the pipes. This joint can also be used for laying of pipes on curves, because at the joint the pipes can be laid at angle. This is a special type of joint. The socket end is cast in a spherical shape. The spigot end is plain but has a bead at the other end. For the assembling of this joints, the spigot end of one pipe is kept in the spherical end of the other pipe.
  159. 159. Flexible Joints
  160. 160. Flexible Joints
  161. 161. Flexible Joints • After this the retaining ring is slipped which is stretched over the bead. Then a rubber gasket is moved which touches the retainer high. after it split cast iron gland ring is placed, the outer surface of which has the same shape as inner surface of socket end. Over this finally cast iron follower ring is moved and is fixed to the socket end by means of bolts. It is very clear that if one pipe is given any deflection the ball shaped portion will move inside the socket, and the joint will remain waterproof in all the position.
  162. 162. Flexible Joints
  163. 163. Mechanical Joints • This type of joints are used for jointing cast Iron, Steel or wrought Iron pipes, when both the ends of the pipes are plain or spigot. There are two types of mechanical joints. • Dressers- Couplings • It essentially consists of one middle ring, two follower rings and two rubber gaskets. The two follower rings are connected to-gather by bolts and when they are tightened, they pass both the gaskets tightly below the ends of the middle ring. These joints are very strong and rigid and can withstand vibrations and shocks up to certain limit. These joints are mostly suitable for carrying water lines over bridges, where it has to bear vibrations.
  164. 164. Mechanical Joints
  165. 165. Mechanical Joints
  166. 166. Mechanical Joints Victaulic Joint • In this type of joints a gasket or leak-proof ring is slipped over both the ends of the pipes. This gasket is pressed from both the sides by mean of half iron couplings by bolts. The ends of pipes are kept sufficient apart to allow for free expansion, contraction and deflection. This joints can bear shocks, vibrations etc.. and used for cast-iron, steel or wrought iron pipe lines in exposed places.
  167. 167. Victaulic Joint
  168. 168. Victaulic Joint
  169. 169. Screwed Joints • The joint is mostly used for connecting small diameter cast iron, wrought iron and galvanized pipe. The end of the pipes have threads outside, while socket or couplings has threads on the inner side. The same socket is screwed on both the ends of the pipes to join them. For making water tight joints zinc paint or hemp yarn should be placed in the threads of the pipes, before screwing socket over it.
  170. 170. Screwed Joints
  171. 171. Collar Joint • This type of joint is mostly used for joining big diameter concrete and asbestos cement pipes. The ends of the two pipes are brought in one level before each other. Then rubber gasket between steel rings or jute rope socked in cement is kept in the grove and the collar is placed at the joint so that it should have same lap on both the pipes. Now 1:1 cement mortar is filled in the space between the pipes and the collar.
  172. 172. Collar Joint
  173. 173. Joint for A.C. Pipes • For jointing small diameter A.C. Pipes the two ends of pipes are butted against each other, then two rubber rings will be slipped over the pipes and the couplings will be pushed over the rubber rings. The rubber rings make the joint water-proof.
  174. 174. Laying of Water Supply Pipes • Pipes are generally laid below the ground level, but sometimes when they pass in open areas, they may be laid over the ground. The pipes are laid in the following way. • First of all the detailed map of all roads, streets lanes etc., is prepared. On this map the proposed pipe line with all sizes and length will be marked. The position of existing pipe line, curb lines, sewer lines etc.. will also be marked on it. In addition to this position of valves and other pipe specials, stand posts etc.. will also be marked, so that at the time of laying there should be no difficulty in this connection.
  175. 175. Laying of Water Supply Pipes • After the general planning, the center line of the pipe line will be transferred on the ground from the detail plan. The center line will be marked by means of stalkes driven at 30 m interval on straight lines. On curves the stalkes will be driven at 7 to 15 m spacing. If the road or streets have curbs, the distance of center of pipe line fro curb will be marked.
  176. 176. Laying of Water Supply Pipes • When the center line has marked on the ground the excavation for the trenches will be started. The width of the trench will be 30 cm to 45 cm more than the external diameter of the pipe. At every joint the depth of excavation will be 15 to 20 cm more for one meter length for easy joining of the pipes. The pipe lines should be laid more than 90 cm below the ground so that pipe may not break due to impact of heavy traffic moving over the ground
  177. 177. Laying of Water Supply Pipes
  178. 178. Laying of Water Supply Pipes • After the excavation of trenches the pipes are lowered in it. The pipe laying should start from lower level and proceed towards higher level with socket end towards higher side. The jointing of pipes should be done along with the laying of pipes. • After laying the pipe in position, they are tested for water leakage and pressure. • When the pipe line is tested, the back filings of the excavated material will be done. • The soil which was excavated is filled in the trenches all around the pipes and should be well rammed. All the surplus soil will be disposed off and the site should be cleaned.
  179. 179. Laying of Water Supply Pipes
  180. 180. Laying of Water Supply Pipes
  181. 181. Laying of Water Supply Pipes
  182. 182. Hydrostatic Test • After laying the new pipe line, jointing & back filling, it is subjected to the following tests: • Pressure Tests at a pressure of at least double of maximum working pressure, pipe joints shall be absolutely water tight. • Leakage Test (to be conducted after the satisfactory completion of the pressure test) at a pressure as specified by the authority for a duration of two hours. • In this way error in workman ship will be found immediately and can be rectified. Usually the length to be tested is kept up to 500 m.
  183. 183. Laying of Water Supply Pipes
  184. 184. Hydrostatic Test
  185. 185. Hydrostatic Test
  186. 186. Pumps for Lifting Water • The function of the pump is to lift the water or any fluid at higher elevation or higher pressure. In water works pumps are required under the following circumstances. • At the source of water to lift the water from rivers, streams, wells etc.. and to pump it to the treatment works. • At the treatment plant to lift the water at various units so that it may flow in them due to the gravitational force only during the treatment of the water. • For the back washing of filters and increasing their efficiency. • For pumping chemical solution at treatment plants. • For filling the elevated distribution reservoirs or overhead tanks • To increase the pressure in the pipe lines by boosting up the pressure. • For pumping the treated water directly in the water mains for its distribution.
  187. 187. Pumps for Lifting Water
  188. 188. Classification of pumps • (i) Classification based on principles of operation • Displacement pump • Centrifugal pumps • Air –lift pumps • Impulse pumps • (ii) Classification based on type of power required • Electrical driven pumps • Gasoline engine pumps • Steam engine pumps • Diesel engine pumps
  189. 189. Classification of pumps • (iii) Classification based on the type of services • Low lift pumps • High lift pumps • Deep-well pumps • Booster pumps • Standby pumps
  190. 190. The selection of a particular type of pumps depend upon the following factors • Capacity of pumps • Number of pump units required • Suction conditions • Lift (total head) • Discharge condition, and variation in the load • Floor space requirement • Flexibility of operation • Starting & priming characteristics • Initial cost and running costs
  191. 191. Displacement Pumps • In these types of pumps vacuum is created mechanically by the movable part of the pumps. In the vacuum first the water is drawn inside the pumps, which on the return of mechanical part of the pump is displaced and forced out of the chamber trough the valve and pipe. The back flow of the water is prevented by means of suitable valves.
  192. 192. Displacement Pumps • The following are the two main type of displacement pumps (i) Reciprocating Pumps (ii) Rotary Pumps
  193. 193. Displacement Pumps Reciprocating Pump • Reciprocating pumps may be of the following types • Simple hand-operated reciprocating pump • Power operated deep well reciprocating pump • Single-acting reciprocating pump • Double-acting reciprocating pump
  194. 194. Reciprocating Pump
  195. 195. Displacement Pumps Rotary Pump (a) Rotary pumps with gear (b) Rotary pumps with cams • The revolving blades fit closely in the casing and push the water by their displacement. The blades revolve in a downward direction at the Centre and the water is carried upward around the side of the casing. In this way the water is pushed through the discharge pipe and partial vacuum is created on the suction side. The intensity of vacuum mainly depends on the tightness of the parts.
  196. 196. Rotary Pump
  197. 197. Displacement Pumps Advantages of Rotary Pumps • They do not require any priming as they are self-primed. • The efficiency of these pumps is high at low to moderate heads up-to discharge of 2000 l/m • These pumps have no valves, are easy in construction and maintenance as compared with reciprocating pumps. • These pumps give steady and constant flow • These pumps are deployed for the individual building water supply and for fire protection.
  198. 198. Displacement Pumps Disadvantages of Rotary Pumps • The initial cost of these pump is high • Their maintenance cost is high due to abrasion of their cams and gears. • They cannot pump water containing suspended impurities as the wear and abrasion caused by the impurities will destroy the seal between the cans and the casing.
  199. 199. Centrifugal Pumps • These pumps work on the principle of centrifugal force, therefore, they are called centrifugal pumps. The water which enters inside the pump is revolved at high speed by means of impeller and is thrown to the periphery by the centrifugal force.
  200. 200. Centrifugal Pumps
  201. 201. Centrifugal Pumps Advantages and Disadvantages of Centrifugal Pumps • The centrifugal pumps have the following advantages • Due to compact design, they require very small space. • They can be fixed to high-speed driving mechanism • They have rotary motion due to which there is low or no noise • They are not damaged due to high pressure
  202. 202. Centrifugal Pumps Disadvantages of centrifugal pumps • They require priming • The rate of flow of water cannot be regulated. • Any air leak on the suction side will affect the efficiency of the pump. • They have high efficiency only for low head and discharge. • The pump will run back, if it is stopped with the discharge valve open.
  203. 203. Design of Pumps • Design of pumps means to find out the capacity of the pump required to deliver specific quantity of water against specific head. • So design of pumps can be divided into two parts • To find the total head against which the pump has to operate. • The total power requirement or the capacity of the pump or the size of the pump required and also deciding the number of pumps required as well as stand by.
  204. 204. Total Head Or Lift Against Which The Pump Has To Work • The total head or total lift against which the pump has to work includes suction lift (or Head), discharge or delivery lift (or Head) and total loss of head due to friction, entrance, exit, fitting etc. in suction and rising main. • If Hs= Suction lift or Head • Hd= Delivery or discharge head • Hl= Total loss of head then, • The total head against which the pump has to work is given by: • H= Hs + Hd + H l
  205. 205. Total Head Or Lift Against Which The Pump Has To Work • Suction lift : It is the difference between the lowest water and the pump • Discharge lift or delivery Head: It is the difference between the point of discharge or delivery and the pump. • Generally only the friction losses is considered for the design as minor losses are very small if the length of the pipe is greater
  206. 206. Total Head Or Lift Against Which The Pump Has To Work
  207. 207. Total Head Or Lift Against Which The Pump Has To Work • Friction loss can be found out by Darcy Weisbach equation • Darcy Weisbach Eqn = Hf= 4 f l v2 = f’ l v2 2 g d 2g d Where , l= length of pipe d= dia of pipe v= velocity of flow f= coefficient of friction f’= friction factor Value of friction factor varies between (0.02 to 0.075)
  208. 208. Power required by the pump or capacity of pump • The horse power (H.P.) of the pump can be determined by calculating the work done by the pump in raising the water up to the height H. • Let the pump raiseW kg of water to height H meter. • Then the work done by the pump= W x H ( • = ϒ Q H (m. kg/sec) • Where, ϒ = UnitWeight of water • Q= Discharge to be pumped in m3 /sec • H= Total head in meter • Water Horse Power (WHP) = ϒ Q H 75
  209. 209. Power required by the pump or capacity of pump • Brake Horse Power (B.H.P) = W.H.P Ƞ = ϒ Q H 75 Ƞ
  210. 210. Number of Pumps, size and stand by units • Pumping units at water works are generally not operated at full capacity for all times. Since the efficiency of pumping unit varies with the load, it is a usual practice to design a pumping station that some of the pump units can be operated at full capacity, at all the time. Hence two, three, or four pumps are installed. The sizes of these pumps can be fixed by considering the demand, available storage. • Thus, there will always exist some stand by capacity to take care of the repairs, breakdowns, etc. Generally 100 % stand-by by capacity to take care against average demand and 33.33 to 50 % standby capacity against the peak demand is considered sufficient and may therefore be provided at the pumping station.
  211. 211. Design of Rising Main Design of Rising Main • Rising main is the pipe through which the pumped water is sent further to the next unit for treatment purpose. Water flows in this pipe under high pressure and flow is turbulent. Here the friction loss in the pipe is more due to high velocity. Pressure pipes are designed such that overall cost of the project should be lowest possible both from maintenance and constructional point of view.
  212. 212. Design of Rising Main
  213. 213. Design of Rising Main Economic diameter of rising main • For pumping a particular fixed discharge of water, there are two options • It can be pumped through bigger diameter pipe at low velocity • Through lesser diameter pipe at high velocity • If the dia of the pipe is increased, it will lead to higher cost of the pipe line on the other hand if the pipe diameter is reduced the velocity would increase which will lead to higher frictional head loss and will require more Horse Power for pumping, thereby increasing the cost of pumping, also cost of fitting will increase. • For obtaining the optimum efficiency, it is necessary to design the diameter of the pumping main which will be overall most economical in initial cost as well as maintenance cost for pumping the required quantity of water. The diameter which provide such optimum condition is known as “economic diameter” of the pipe.
  214. 214. Design of Rising Main • An empirical formula given by lee is commonly used for determining the dia of the pumping or rising main • D= 0.97 to 1.22 √Q • Where, • D= Economic dia of pipe in meters • Q= Discharge to be pumped in cumecs
  215. 215. Design of Rising Main Head loss in rising main • The loss of head in the rising main can be found by using • (i) Darcy Weisbach eq • (ii) Hazen William’s equation • Darcy Weisbach Eqn= Hf= 4 f l v2 = f’ l v2 2 g d 2g d Where , l= length of pipe d= dia of pipe v= velocity of flow f= coefficient of friction f’= friction factor Value of friction factor varies between (0.02 to 0.075)
  216. 216. Design of Rising Main Hazen Williams Equation • V= 0.85 CH R 0.63 S 0.54 • Where, • V= velocity of flow • S= Slope of H.G.L • = Hl = Head Loss L Length of Pipe R= Hydraulic mean Radius of the pipe = A P If pipe is running full then R= Π/4 d2 = d/4 Π d CH= Hazen William’s coefficient which depends on age, quality and material of pipe.
  217. 217. Examples • Find out the head loss due to friction in a rising main from the following data: • Length of the rising main= 600 m • Diameter of pipe= 0.2 m • Discharge required to be pumped = 1200 l/min • Friction factors= 0.025
  218. 218. Examples • Velocity of flow = QA Q= 1200 l/min = 1200 x 10-3 m3 /sec 60 = 0.02 m3 /sec V= 0.02 Π (0.2) 2 = 0.637 m/sec 4
  219. 219. Examples • Hf= f’ lv2 2gd = 0.025 x 600 x (0.637)2 2 x 9.81 x 0,2 = 1.551 m
  220. 220. Examples • A city with 1.5 lakh population I to be supplied water at 100 lpcd from a river 1 km away. The difference in water level of sump and reservoir is 30 m. if the demand has to be supplied in 8 hr., determine the size of the main and B.H.P of the pumps required. • Take f- 0.0075, velocity in the pipe as 2.0 m/sec and efficiency of pump as 75 %
  221. 221. Examples • Population of a city= 1,50,000 • Rate of water supply= 100 lpcd • Therefore the average demand of the town= 1,50,000 x 100 • = 15 x 10 6 l/day • Maximum daily demand= 1.5 x avg demand • = 1.5 x 15 x 10 6 • = 22.5 x 10 6 l/day • = 22.5 MLD
  222. 222. Examples • As the full demand is to be supplied through pumps in 8 hrs • Discharge required= 22.5 x 10 6 l/ hours • 8 • = 22.5 x 10 6 x 10 -3= 0.781 m3 /sec 8 x 3600
  223. 223. Examples • The maximum velocity in the pipe is given as 2.0 m/sec • Therefore Cross sectional area of the pipe required • A= Q = 0.781 = 0.39 m 2 • v • If d is the dia of the pipe then • Π d 2 = 0.39 4 D= 0.704m = 0.75 m Total lift is given as 30 m
  224. 224. Examples • Friction loss hf can be found by using Darcy Weisbash eq n • Hf= 4 f l v2 2 g d = 4 x 0.0075 x 1000x (2.0 ) 2 2 x 9.81 x 0.75 = 8.155 m
  225. 225. Examples • Thus the total lift against which the pump has to work or lift water • = 30 + 1.155 • = 38.155m • BHP of the pump= ϒ Q H 75 Ƞ = 1000 x 0.781 x 38.155 75 x 0.75 = 526.75 = 530 HP 1 hp(I) = 745.699872W = 0.745699872 kW 1 W in ... ... is equal to ... 2 3 • 1 kg·m /s
  226. 226. Example • From a clear water reservoir 3 m deep and maximum water level at RL 35 m water is to be pumped to an elevated reservoir at RL 80 m at the constant rate of 9 lakh litres per hour. The distance is 2000 m. Find the economic diameter of the rising main and the water horse power of the pump. Neglect minor losses and take f=0.01
  227. 227. Example • The Discharge Q= 9 lakh per hour • = 9,00,000 = 0.25 m3 /sec 1000x 60 x 60 Economic diameter of rising main can be found by D= 1.22 √Q = 1.22 √0.25 = 0.61 m
  228. 228. Example • Maximum Suction Head = 3 m ( depth of reservoir) • Maximum delivery head = (80- 35)= 45 m • (Difference between maximum water level and height of elevated reservoir) • Suction + Delivery= 3 + 45 = 48 m
  229. 229. Example • Friction Head loss can be found by • Hf= 4 flv 2 2 g D V= Q = 0.25 = 0.855 m/ sec A Π (0.61) 2 4 Hf= 4 x 0.01 x 2000 x (0.855) 2 2 x 9.81 x 0.61 Hf= 4.886 m The total Head = 48 + 4.886 m H= 52.886 m
  230. 230. Example • Water horse power of Pump= ϒ Q H 75 = 1000 x 0.25 x 52.866 75 = 176.22 HP
  231. 231. References Water Supply Engineering : By Prof S.K. Garg Khanna Publishers Internet Websites
  232. 232. Thanks…