Groundwater & pumps


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This document explains about various types of pumps used and about groundwater

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Groundwater & pumps

  1. 1. Energy & Environment
  2. 2. Distribution of the World’s Water How much of the World’s water is fresh & available? Our main source of water is groundwater
  3. 3. Hydro Cycle Revision Water in the world is reused Rain Lakes and StreamsGroundwater As well as being the largest % of fresh water, what else is good about groundwater
  4. 4. Revision of Permeability Clay Sand Clay is Sand is Impermeable Permeable
  5. 5. Permeability of RockRock Cracks in rock Water travels through cracks in rocks If no cracks then water cannot move
  6. 6. Advantages of ground water Sand is PermeableWater is filtered through sand and gravel More chance of water availability in summerReduced risk of contamination Stays at a stable temperature
  7. 7. Ground Water Storage: AquifersMovement ofwater throughthe ground/rocks Storage of groundwater Saturated Zone
  8. 8. Unconfined Aquifer A pump is required to overcome this headThis difference inheight is called thehead required. Water TableUnconfined Aquifer Non permeable rock/clay No cracks for water to move
  9. 9. Confined / Artesian Aquifer If head required> pressure in aquifer then pump is requiredNo pump required ifhead required <pressure in aquifer Water in aquifer is trapped so pressure builds upArtesian/ConfinedAquifer Non permeable rock/clay No cracks for water to move
  10. 10. Head Where you want to collectThis difference in water fromheight is called thehead required. A pump is required to overcome this head Where water is (water table)
  11. 11. Where would you build your well? Shortest well, so smallest head B required & also A close to house CD Non permeable rock/clay
  12. 12. Where would you build your well? C A BWastage of water?Storage Needed? What are the issues with your choice?
  13. 13. Effect of well on Water table What do you think will happen when we build a well? Original Water Table
  14. 14. Effect on other wells Drawdown Original Water Table
  15. 15. Summary Drawing Explain this drawing
  16. 16. What type of Well? Bored or Drilled Well Deep narrow well Protected from pollutants Can safely abstract waterHand dug-normally quiteshallowOpen to pollutionEven the bucket and rope cancontaminate the water supply
  17. 17. Digging Wells Hand drilled Cant get that deepNot advised to drillamount of water Limited into hard rock-not easy to Use an augerfind connecting cracks Jetting wells After drilling, borehole Machine drilled Use of water to will need casing or well boreholes loosen soil and will need bricks to Drilling rig & crew carry it to surface support it Time and money Sand/gravel/clay –not rock Percussion drilling Rotary drilling
  18. 18. Machine Drilled Boreholes: CablePercussion Drilling TripodNot good for rock Falls by gravity Drilling shallow boreholes Low cost & minimum disruption
  19. 19. Machine Drilled Boreholes: Rotary Drilling Exerts downward pressure and drills rotationally all the way downSharp,rotational drillbit rotatesround
  20. 20. Well YieldImportant to know the yield of the well so we know what pump to usePrevent drawing down the well too much or effecting other wellsThe Yield of an aquifer depends on the1. Amount of water available2. Rate at which it can be extracted Depends on soil type or amount of cracks in the rockA pumping test is done to estimate the yield of the borewell
  21. 21. Pumping Test Pump well for 8 to 48 hours. Rate of water pumped Distance to new water =volume/time level/time Tests the balance between the max volume of water pumped out and rechargeNormally carried out by Drawdown Rechargespecialist contractors Balance achieved when water level stops Recharge dropping. This is the yield
  22. 22. Calculating Head Required: If Pump Below Water Total head to overcome=Static + Friction-Suction headHeight differencebetween twowater bodies Head needed to get to pump Bend in pipes etc
  23. 23. Calculating Head Required: If Water Below Pump Total head to overcome=Static + Friction + Suction headHeight differencebetween twowater bodies Head needed to get to pump Bend in pipes etc
  24. 24. Types of Pump: PositiveDisplacement e.g. HandpumpFixedvolume ofliquidpumped upeach time Due to pressureLiquid is physically change, water is Liquid is physicallydisplaced sucked up displaced
  25. 25. Hand Pump Heavy pump handle to Rod connects balance with the inside handle to of the pump to make it piston easy for user. Rising Main carries Valve the water to the outlet Valve Pump cylinder pushes water to rising mainScreenPrevents stones and Foundation preventgravel but allows contaminating supplywater through Depth= 50m or less
  26. 26. Hand Pump Check valve open from gravityCheck valve Check valveclosed closed Foot valve Foot valve Foot valve closed from open from open from weight of suction suction water Suction pulls Suction pulls Piston moves water up water up through water and displaces water
  27. 27. Hand PumpCheck valve Check valveopen from open fromgravity gravity Check valve closed Foot valve Foot valve closed from Foot valve closed from weight of closed from weight of water weight of water water Piston moves Piston reaches Piston gets pulled up andthrough water and bottom of displaces the water on top displaces water cylinder. of piston. Also sucks up more water from borehole
  28. 28. Make your own DisplacementPump
  29. 29. Make your own DisplacementPump
  30. 30. Types of Pump: RotodynamicMachine which moves quickly and passes thiskinetic energy onto a liquid.If speed of pump increases=discharge &pumping head increasese.g. centrifugal pump Water Water (little speed) (lots of speed)
  31. 31. Centrifugal Pumps Fast water small area through pushedCasing forceswater through small space Shaft turned byImpeller gives (lots of speed) water energy electric/diesel Water motor Water(little speed)
  32. 32. Centrifugal PumpsCasing forces speed of water todecrease as less area, thisincreases the pressure. Watergets lifted due to this pressure Pressure = Force AreaImpeller spins the water roundaccelerating it.Force=mass x acceleration
  33. 33. Operation of a Surface MountedCentrifugal PumpNever run pump dryIf the pump is above the waterbodythen it cannot pump only air.It needs primedPriming means the pump casinghas to be filled with water beforestarting the pump.Better to start the pump against a closed valve-this reduces thepower needed for start
  34. 34. Multistage Pump If the required head cannot be met by one centrifugal pump then a multistage pump is used Series of centrifugal pumps Pressure of liquid is increased in stagesCan block easily and become damaged –so only good for very cleanwaterUsed for boosting water pressure and in submersible borehole pumps
  35. 35. Submersible Centrifugal Pumps Waterproof pumpPush fluid to the surface Series of impellersTypically multistagecentrifugal pumps Power supplyoperating in verticalposition Water enters here Ensure pipe does not dry out
  36. 36. Make your own Rotodynamic Pump
  37. 37. Make your own Rotodynamic Pump
  38. 38. Make your own Rotodynamic Pump
  39. 39. Simple Jet Pump Suction Pipe Venturi Underwater part of a deep well jet pumpSpeeds up the Q=velocity x areawater causing Low presurea pressure Change in pressure High velocity is related todrop. Thissucks in more High pressure change in velocitywater . Pressure pipe Half of water sent back through Cone shaped nozzelVenturi throatReduce area so increasePressure
  40. 40. Simple Jet Pump Jet pumps are designed to pump large volumes of water
  41. 41. What pump to use?Pump Type Lifting from Abstract from Distribute wells or rivers & lakes through boreholes pipelineSurfacemountedcentrifugalElectricsubmersiblemulti-stagecentrifugalHand pump
  42. 42. Selecting the correct pumpBased on head to overcome and flow need to pumpHead(m) Pump Curves from suppliers m3/s
  43. 43. Vigyan Ashram Pump ExerciseCarry out a tour of Vigyan Ashram’s pumpsComplete the below table with all the information youcan find outLocation Type of Head Power How could this pump/well be pump Rating improved?
  44. 44. Vigyan Ashram Pump Exercise How could you improve these pumps? This should be your next environment project!
  45. 45. To select the correct centrifugalpump1. Calculate the flow rate. This will depend on the water use.2. Calculate the static head.3. Calculate the friction head This will include the friction over the length of pipe and the friction from local bends etc4. Calculate the total head (static + friction)5. Use Pump curves from suppliers to find the correct pump
  46. 46. Pump Head ExampleCalculate the head a submersible pump down this borehole would requireYou need to fill a 900 liter tank Assume you are using a 15mmDue to cost of running a pump internal diameter PE pipeand unreliability of electricity,you aim to fill this tank in 30mins. 5m 10m 1.What is the flow 8m needed from the pump? So Flow required = 900 liters = 30 liters = 0.5 liters 30 mins 1 min second
  47. 47. Pump Head Example2.What is the static head?Hstatic=8 +5= 13m 5m 5m 10m 8m 8m
  48. 48. Pump Head Example3.What are the friction head losses?Remember these are due to: A. Losses due to the length of the pipe (affected by the type of material) B. Local losses due to bends in the pipe and entry and exit 5m 10m 8m
  49. 49. Pump Head Example3.What are the friction head losses? First Hf = 10.9L x Q 1.85lets look at losses due to the length of the C 1.85 x D 4.87pipe. Use the Hazen Williams formula to calculate the 5m friction losses due to length 10m of pipe 8m
  50. 50. Pump Head Example: HazenWilliams Formula Length of pipe (m) Flow (m3/s) Hf = 10.9L x Q 1.85 C 1.85 x D 4.87 Frictional head loss (m) Internal diameter of pipe Coefficient
  51. 51. Pump Head Example Hf = 10.9L x Q 1.85 L= 8m + 10m +5m=23m of pipe C 1.85 x D 4.87 Q= 0.5l/s =0.0005m3/s C= 150 for PE & PVC Pipe Hf = 10.9 x 23 x 0.0005 1.85 150 1.85 x 0.015 4.87 D= 15mm= 0.015m Hf=15m 5m 10m Friction losses from the length of the pipe is Hf=15m 8m
  52. 52. Pump Head Example3.What are the friction head losses? Firstlets look at losses due to the length of thepipe. 5m 10m 8m You can also use tables Hf = 23m x 0.9 from suppliers to =20.7m calculate the head loss due to length of pipe
  53. 53. Pump Head Example Coefficient of bend/entry/exit Velocity hL= kL v23.Now lets look at local losses due to 2gbends in the pipe and entry and exit Exit Loss gravity kL values 90°bends =1 5m Plain suction entrance=0.9 10mEntry Loss Sharp exit=1 8m h = (3 x k 90°bends + k entrance + k exit) x v2 L L L L 2g hL= (3 x 1+ 0.9+ 1) x v2 2g Need to find the velocity of the water. V=Q/A
  54. 54. Pump Head ExampleCross sectional area of pipeA=Πxd2 4 0.015mA=3.14 x 0.0152 4A=0.000177Q= 0.5l/s =0.0005m3/sV= Q = 0.0005 =2.83m/s A 0.000177hL= (3 x 1+ 0.9+ 1) x v2 hL= (3 x 1+ 0.9+ 1) x 2.832 2g 2 x 9.81 =2m So local friction losses account for 2m of head
  55. 55. Pump Head Example3. S0 the friction losses are: hk= 15mA. Losses due to the length of the pipeB. Local losses due to bends in the pipe and entry and exit hL= 2m 5m 10m 8m
  56. 56. Pump Head ExampleCalculate the total head requiredTotal head = hstatic= 23m + Hk )= 15m + hL= 2m = = 40m (due to length of (due to local pipe) losses) 5m 10m The more head we have to overcome the more energy we need to use. 8m Can you think of any ways to reduce this head? Reduce number of bends Chose a bigger diameter pipe Chose a smoother material Have bell shaped entry
  57. 57. Pump Head ExampleSo to find a suitablepump. You need to lookat pump curves. Head (m) 40m 0.0005m3/s Suitable pump m3/s