1. PUMPS

2. Types of pumps 1.Roto-dynamic pumps i.Centrifugal pump ii.Axial flow pump 2.Displacement pumps i.Reciprocating pump ii.Rotary pumps 3.Other types i.Air lift pumps ii.Jet pumps iii.Hydraulic rams

3. ROTO DYNAMIC PUMPS Consists of a wheel type rotating element – Impeller. The shape of impeller may be such as – To force water outward in a direction at right angles to its axis – RADIAL FLOW. – To give water, an axial as well as a radial velocity – MIXED FLOW. – To force water in the axial direction alone – AXIAL FLOW.

4. Radial and mixed flow machines – CENTRIFUGAL PUMPS – commonly used. Axial flow machines – AXIAL FLOW PUMPS. RADIAL FLOW MIXED FLOW AXIAL FLOW

5. Centrifugal pumps Radial or mixed flow Impeller may be open or closed. Open impeller consists of a hub to which vanes are attached. – Efficiency is much less than that of closed impeller due to clogging of debris. Closed impeller is having plates on each sides of the vanes. Casing of radial flow type centrifugal pump may be of – Volute type – Turbine type

6. Volute type centrifugal pump Impeller discharges into a gradually expanding spiral casing. It produces an equal velocity around the circumference and to reduce the velocity of water as it enters discharge pipe. Thus creating required pressure head.

7. Turbine type or diffuser type centrifugal pump Impeller is surrounded by stationary guide vanes which reduces the velocity of water before water enters the casing. The casing is generally circular and concentric with impeller. Velocity of water is more completely converted into pressure head High efficiency

9. Advantages of centrifugal pumps 1.Initial and maintenance cost are comparatively low 2.Their size is compact and can be installed in limited space 3.Their mechanism is simple. Less skilled labour is required for its operation and repairs. 4.Can be operated with high speed electric motors, or gas engines and steam turbines 5.Discharge is steady and non pulsating 6.Can be used for pumping water containing silt, sand etc., 7.Durable and safe against pressure.

10. Disadvantages of centrifugal pumps Requires priming For higher head, efficiency is low The discharge pipe has to be provided with check valve, to avoid the backflow when the pump suddenly stops due to power failure,etc., with the discharge valve open. Discharge varies with the head of water. When uniform discharge is required at varying heads, the pumps has to be rotated at variable speeds which is neither, practical nor economical. Their ordinary suction lift is limited(about 6m or so).

11. Displacement pumps – Reciprocating pumps Simplest form of reciprocating pump – Hand operated well pump(commonly called hand pump). Can be used in any depth. For wells, where water table is within 6m or so. Requires foot valve at the end of the suction pipe to avoid priming. Single acting pumps – discharge occurs at alternative piston strokes. Double acting pumps – Delivers water at each stoke – more uniform flow

13. COMPONENTS CYLINDER - It is made of cast iron or steel alloy. PISTON - The piston reciprocates inside the cylinder. CONNECTING ROD - It connects piston and rotating crank. SUCTION PIPE- It connects the source of water and cylinder. DELIVERY PIPE - Water sucked by pump is discharged through the delivery pipe. SUCTION VALVE - It adjusts the flow from the suction pipe into delivery pipe. DELIVERY VALVE - It admits the flow from the cylinder into the delivery pipe.

14. ADVANTAGES High efficiency No priming needed Can deliver water at high pressure Can work in wide pressure range Continuous rate of discharge if provided with two pistons or more. DISADVANTAGES More parts mean high initial cost High maintenance cost Occupies more space. Needs skilled supervision during operations Low discharging capacity Pulsating flow High wear in parts

15. Displacement pumps – Rotary pumps

16. ADVANTAGES Self-priming. Flow is free from pulsations. Simple to construct and easy to repair when compared to reciprocating pumps. Often used for fire protection system for buildings and for small domestic water systems. Efficiency is high at low to moderate heads and for smaller discharges. DISADVANTAGES Initial cost is high. Not durable, they require frequent replacement of their cams or gears. Water containing sediments are very injurious to such pumps, as the wear and abrasion will destroy the seal between the cams and the casing.

17. Submersible pump Driving motor is placed below the pump bowls within the well water level. The driving shaft is completely eliminated. Thus reducing the bearing friction. The water rises to the surface through a riser pipe on which the assemble is suspended. The electrical parts or the motor bearing are enclosed by a oil filled case with mercury seal.

18. Air lift pumps Used for pumping water from deep wells for lift of about 60 – 80m. Can be used for high lifts about 150 metres but their efficiency is generally low.

19. Advantages and disadvantages of air lift pumps. ADVANTAGES: Inspite of low efficiency, an air lift pump can deliver large amounts of water from small dia wells. Not harmed by sedimented water. Cheaper, reliable and simple in operation No moving parts which may be in contact with water– used for highly acidic or alkaline water. Yield of a well, using such pump, can be increased by using more amount of compressed air.

20. DISADVANTAGES Not adopted for raising water much above the ground level, and if this is necessary, a second pump has to be installed. Efficiency is low Flow obtained is not continuous but is intermittent. Less flexible in fulfilling variable demands. In order to obtain sufficient value of submergence, the depth of submergence has to be increased and thus the well has to be made deeper than required. This increases the cost.

21. Jet pumps Used for pumping water from small wells. Used for constructional works for dewatering trenches. Efficiency is low Compact and light in weight Can also handle sedimented waters without much trouble.

22. Hydraulic ram A kind of pumping arrangement which does not utilise any outside power and uses the principle of water hammer pressures developed when a moving mass of water is suddenly stopped. A large amount of water must be available at moderate head, so as to lift small amount of water to higher head. Can be used for lifts of order of 30m or so.

23. Advantages and disadvantages of hydraulic ram ADVANTAGES: Its working is simple and when once it starts functioning, practically no attention is required. The Ram is durable. It is cheap as it does not require any fuel. DISADVANTAGES: Considerable amount of water is wasted through a waste valve, and cannot be used at places where water is scarce. It produces considerable noise while working.