Pumps and pipes

pumps
pipes
coupled joint
advantages
asbestos cement pipes
copper pipes
coupled joint

1. Pumps and Pipes

2. Purpose of Pumping To lift the raw water from the source – lake, reservoir, river or well To lift the treated water to overhead tanks or reservoir To deliver treated water to the consumer’s tap with pressure. To boost the line pressure To supply water under pressure to fire hydrants. For miscellaneous operations at the treatment plants, such as Backwashing of filter Pumping chemicals Dewatering the tanks, basins, sumps etc.

3. Types of Pumps Mechanical Principles of operations Types of power required

4. Selection of pumps Capacity of the pump Number of pump units required Suction conditions Lift (total head) Discharge conditions and variations in the load Floor space requirement Flexibility of operations Starting and priming characteristics Types of drive required Initial cost and running costs.

5. Components of Pumps: Casing Internal main moving apart Motor Inlet Outlet Electrical connection

6. Mechanical Principle’s of Operations: Displacement Pumps Centrifugal pumps Air lift pumps Miscellaneous pump

7. Displacement Pumps: Positive displacement pumps: Liquid sucked and then it is pushed or displaced due to the thrust exerted on it by moving member, which results in the lifting of the liquid to the desired height. Pump has one or two chambers which are alternatively filled and emptied with the liquid to be pumped.

8. Two Types Reciprocating pumps Rotary pumps

9. Reciprocating pumps: Consists of piston or a plunger which move to and fro in a close fitting cylinder which is connected to the suction and delivery pipes. Pipes are provided with non returnable or one way valves, In Single acting reciprocating Pumps, during suction stroke, piston or plunger moves outwords , a partial vacuum is created in the cylinder, which enables the atmospheric pressure acting on the liquid surface in the sump below to force the liquid in the cylinder by forcing open the suction valve.

10. During the inward motion of the plunger, the liquid in the cylinders is forced up the delivery pipe, during this operation suction valve S closes and delivery valve D opens. The action is then repeated. The piston or plunger is moved by a crank rotated at uniform speed by driving engine or motor.

11. In Double acting reciprocating pump, Liquid is in contact with both the sides of the plunger. It has two delivery and two suction pipes with valves. During such stroke, suction takes place on one side of the piston while the other side delivers the liquid. Due to this there are two suction strokes and two delivery strokes in one revolution of the crank .

12. Depending upon the number of cylinders provided, reciprocating pumps may be classified as follows Single cylinder pump Double cylinder pump Triple cylinder pump Duplex double action pump

13. Rotary Pumps In rotary pumps, two gears occam’s mesh together and rotate in opposite directions. The rotating elements fit closely in the casing, so that water is drawn up the suction pipe, trapped between the teeth or cams and the casing and forced out into the discharge pipe . In this pump no valve is required and the flow is practically continuous. The pumps which use the above principle of rotary displacement are: gear, lobe, screw, moyno and vane pumps. Not common to use in water work.

14. Centrifugal pump When a certain mass of liquid is made to rotate by an external force, it is thrown away from the central axis of rotation and a centrifugal head is impressed which enables it to rise to a higher level. The centrifugal pump employs a rotating impeller with water being drawn at the hub or eye of the pump impeller and disharged through a spiral casing by virtue of the centrifugal force developed due to the rotation of the impeller. In addition, the liquid passes through the revolving wheel, its angular momentum changes – results in the increasing pressure of the liquid.

15. Based on the casing provided, these pumps are classified into two types. Volute Pump Diffuser or turbine pump

16. Volute Pump: Impeller is surrounded by a spiral shaped casing commonly called as volute chamber. The shape of the chamber is such that the sectional areas of the periphery of the impeller increases gradually to the delivery pipe. In other design, the circular portion is called as a vortex chamber, which reduces the velocity and increases the efficiency of the pump by converting large amount of kinetic energy into pressure energy.

17. Diffuser or turbine pump: A diffuser ring remains stationary while the impeller rotates inside the ring. The liquid after leaving the impeller passes through the gradual in enlarged passages of the guide vane. Due to this , the velocity of flow gradually decreases while the pressure increases. After passing through the guide vanes, the liquid flows onto the surrounding casing which may be either circular or volute shaped. A diffuser pump is a reverse turbine, and hence it is known as a turbine pump.

18. A centrifugal pump may be further classified into a single stage and multi stage pump depending upon number of impellers mounted on the shaft. A single stage pump has only one impeller while , multistage pump has two or more impellers connected in series. The water first collected in a casing or volute and discharged into the eye of the second impeller and so on. As many as six stages are being sometimes employed and each stage increases the head from 30 to 45 metres , Mainly used in deep wells. Based on direction of flow, centrifugal pumps are classified as radial flow pump, mixed flow pump and axial flow pump. Radial flow pump, liquid flow in radial direction, axial flow type, liquid flow in axial direction. In mixed, the liquid will flow radial as well as axial direction.

19. Based on the number or entrance to the impeller, a centrifugal pump may be classified as single suction pump or double suction pump. In double suction pump , liquid enters from both the sides of impeller. Due to which the thrust neutralized. Pumps are also known as horizontal or vertical when their shaft are horizontal and vertical The impellers of the centrifugal pump may be of two types: open or closed. Open impeller are suitable for use with liquids containing solids, such as sewage etc where as closed one is efficient for water supply

20. Air lift pumps In these pumps, compressor is used to force air into a small diameter pipe called the air pipe. The air pipe is placed in a bigger diameter discharge pipe, sometimes known as education pipe. When air is forced into water, air water mixture is formed whose specific gravity is lower than that of water, Due to this air rises in education pipe and is discharged out.

21. Miscellaneous pump Booster Pump: Domestic pump used to boost pressure in water line. Submersible pump: centrifugal type motor also submerged in water - suitable where lowest point of pumping of water is far. Type of power Steam engine pumps Diesel engine pumps Electrically driven pumps

22. Taps and Cocks Bib Cock: These are the water taps which are attached at the end of water pipes and from which the consumers obtained water Fixed on water line at vertical surface or walls, used as bathroom taps, ablution taps etc. It is operated from a handle, the water comes out from the opening. The bib cocks may also be of push type and they operate automatic.

23. Pillar Cock: Fixed on horizontal surface in wash basin are relatively easy to repair

24. Stop Cock: use to control the flow of water entering the tap fixed before the taps of wash basin, sink, flushing cisterns.

25. Ferrule It is gunmetal or bronze screwed into the hole drilled in mains. The pressure in the house connection are effected by adjusting the ferrule opening. Normally the ferrule opening is equal in area to the area of flow in outlet pipe.

26. Water Meter Water metering is common for residential and commercial drinking water supply. Benefits: Water is conserved It helps to detect water leakage in the distribution system. Problems: Problems associated with metering arise in the case of intermittent supply Sudden changes in pressure can damage meters any types of meters also register air flows, which can lead to overregistration of consumption

27. Faucets A fixture for drawing or regulating the flow of liquid especially from a pipe

28. Pipe Pipe is a circular closed conduit through which the water may flow either under gravity or under pressure. water supply pipes mostly run under pressure. Sewer lines pipes do not run full - under gravity

29. Pipe Fittings In addition to the pipes, valves, tapes, various types of pipe fittings such as unions, caps, plugs, flanges, nipples, crosses, tees, elbows, bends etc are used during laying of distribution pipes The common pipe fittings are shown in figure below.

30. Materials for Pipes Pipes generally made up of the following materials: Cast Iron. Wrought iron Steel Galvanized iron Cement concrete Asbestos cement Plastic Lead Copper Wood.

31. Cast Iron Pipes: Used in great majority of water distribution mains . Resistant to corrosion. Long life over 100 years Manufactured by two methods: Ordinary sand molding process Centrifugal process Cast iron pipes are generally cast in lengths of 3 to 6 meters.

32. Joints in cast iron pipe Spigot & socket joint : The enlarged end of the pipe is known as the socket or bell. The socket accommodates the normal or the spigot end.

33. The hemp or sterilized yarn is used to maintain the alignment and molten lead heated to 400 c is then poured and caulked up using a series of chisels. The quantity of lead varies from about 5kg for 15cm dia. pipe to about 55kg for a 120cm dia. pipe. These joints are also known as run-lead joint.

34. Flanged Joint : Joint with flanges. The pipes are carefully aligned before bolts are inserted and the flanges are pulled together. A rubber ring of diameter lesser than the bolt circle diameter is inserted between the flanges. The contact should be between clean dry rubber and clean dry metal flanges and no oil or grease etc should be inserted.

35. Coupled Joint : Two types of coupling joints are used Viking Johnson coupling and Victaulic coupling. In both of these the pipes do not have sockets or spigots. Such joints are highly flexible.

36. Expansion Joints : Expansion joints allow the pipe expand or contract freely under the changing temperature conditions. The space between the socket and spigot is filled with an elastic gasket.

37. Advantages & Disadvantages: of CI pipes Advantages: C. I. pipes are of moderate cost. Their jointing is easier They are resistant to corrosion. They have long life Service connections can be easily made in them

38. Disadvantages: They are subject to tuberculation in certain waters, due to which their carrying capacity is reduced to as much as 70% They are heavier, and hence uneconomical when their diameter is more than 120cm They can not be used for pressures greater than 7kg/cm 2 They are fragile.

39. Wrought Iron & Galvanized Iron Pipe: Are manufactures by rolling flat plates of the wrought iron to the proper diameter and welding the edges. Pipes are much lighter than the C. I. pipes and can be more easily cut, threaded and worked. They look much neater, but are much costlier. They corrode quickly, and hence are used principally for installation within buildings. These pipes are usually protected by coating them with a thin film of molten zinc. Such coated pipes are known as galvanized iron (G. I.) pipes, and they are commonly jointed by screwed and socketed joints.

40. Steel Pipe: Small sizes can be made from the steel. Larger sizes are made by riveting or welding together the edge of suitably curved plates, the socketed being formed later in a press. The joints may be either transverse and longitudinal or transverse and spiral. Steel pipes cannot be easily made to resist high external pressures. Steel pipes are more useful to serve as big mains laid above ground.

41. They are suitable on bridges where strength and low weight are desired. Most steel pipes are produced plain ended and are therefore connected with Viking Johnson coupling. Life of steel pipe depend on the quality of protective coating on internal as well as external surface.

42. Cement Concrete Pipe: They may be either plain or reinforced They are either pre cast or may be casted on site. The plain cement concrete pipes are used for heads up to 7m while reinforced cement concrete pipes are normally used for heads upto 60m. For the heads higher than this , pre-stressed concrete pipes are used. RCC pipes are used for large water supply distribution mains. Water tightness in low pressure reinforced concrete pipe is obtained by providing sufficient thickness of good concrete (1:1:4mix)

43. Advantages & Disadvantages: of Cement Concrete pipes Advantages: resist the external loads and loads due to backfilling. The maintenance cost is low The inside surface of pipes can be made smooth, thus reducing the frictional losses. The Problem of corrosion is not there. Pipe can be cast at site - transportation problems are reduced. Due to their heavy weight, the problem of floatation is not there when they are empty. Expansion joints are not normally required.

44. Disadvantages: Unreinforced pipes are liable to tensile cracks, and they cannot withstand high pressure. The tendency of leakage is not ruled out as a result of its porosity and shrinkage cracks. It is very difficult to repair them. Precast pipes are very heavy, and it is difficult to transport them.

45. Asbestos Cement Pipes: Manufactured from asbestos fibre and Portland cement combined under pressure to form a dense homogeneous structure having strong bond between cement and the fiber. Completely impervious to passage of water through its walls. Finished with plain ends, the exterior of the barrel being manufactured to receive the coupling. The joints used are of simplex type, consist of sleeve which fits over the plain ends of the lengths, water – tightness being obtained by two rubber rings compressed between the sleeve and the pipe barrels. The join thus becomes flexible and water tight. The pipe can be tapped and threaded for service connections in the same manner as iron pipe.

46. Advantages and Disadvantages: Asbestos Cement Pipe Advantages: Smooth internal surface, due to which the frictional losses are reduced. Light and easily transported Easily cut, fitted or jointed Service connections can be easily taken as easily drilled and tapped Anti Corrosive No expansion joints are required.

47. Disadvantages: Asbestos Fibres will leads to lung cancer. They are soft and brittle & Weak under impact loading due to moving traffic Not durable Cannot be laid in exposed tie Costly

48. Copper pipes: Very costly so use is restricted for conveyance of hot water . These pipes do not sag or bend due to hot water. They are also resistant to corrosion by acidic or alkaline waters. Can withstand high internal pressure

49. Lead Pipes: They are very soft and can be easily bent. Extensively used in service connections and for internal plumbing Not used in water supply pipes .

50. Wood – Stave pipes: Prepared from staves or planks of wood held together by steel bands. They have been used for many years for water supply pipes. Used in industrial plants where highly corrosive liquids are to be conveyed.

51. Plastic Pipe: Recent origin Made up of synthetic resins of high molecular weight, polymerized from simple compounds by heat, pressure and catalysts. Plastic pipes and tubes are manufactured from a number of polymerization products such as polythene.

52. Advantages and Disadvantages: Plastic Pipe Advantage: Free from corrosion Free from damage due to freezing and thawing of water in close pipe. Cheaper Highly resistant to acidic water Light in weight, easy to handle & transported Smooth and possess low hydraulic resistance Good electric insulators. Jointing, bending & installation is easy.

53. Advantage: Have adequate strength and are resistant to shock Durable and are unaffected by age, sunlight or weather. Disadvantages: Low resistance to heat Coefficient of expansion is high Some plastic impart taste to water.