1. PUMPS & PUMPING STATIONS

2. Pumps
Types of Pumps
Roto-dynamic pumps: Centrifugal pump & Axial-flow pump
 Has wheel or a rotating element which rotates the water in casing, imparting energy to the water
Displacement pumps: reciprocating pump & rotary type pump
 works on the principle of mechanically inducing vacuum in a chamber, thereby drawing in a volume of water which is then mechanically displaced & forced out of the chamber
Other types: air lift pumps, jet pumps, hydraulic rams etc.

3. Types of pumps Rotodynamic pumps
It has a wheel (impeller) which rotates the water in a casing, thus imparting energy to water.
Shape of impeller such as to force water outward in a direction at right angle to its axis (radial flow), or to give water ,an axis as well as a radial velocity(mixed flow),or the force the water in axial direction (axial flow)

4. Displacement pumps
It works on the principle of mechanically inducing vacuum in a chamber, there by drawing in a volume of water which is mechanically displaced and forced out of chamber.

5. Pumps Roto-dynamic pumps:
 have a wheel type rotating element called impeller
 shape of the impeller may be such, as to force the water outward in a direction at right angles to its axis, or to give water, an axial as well as a radial velocity, or to force the water in the axial direction alone
 radial flow & mixed flow machines are commonly called centrifugal pumps whereas the axial flow machines are called axial flow pumps.

6. Types of centrifugal pumps
Radial/Mixed flow(Open or closed): open impeller consists of a hub to which the vanes are attached, while closed impeller is having plates on each side of the vanes
 open impeller is adopted for pumping raw waters or sewage containing solids & other impurities as it is less likely to be clogged by debris.
Volute type : Impeller discharges into a gradually expanding spiral casing, designed to produce an equal velocity of flow around the circumference of impeller and reduce the velocity of water as it enters the discharge pipe, thus creating the required pressure head.
Turbine type (Single stage or Multistage pump):
 Impeller is surrounded by stationary guide vanes which reduce the velocity of water before it enters the casing, thus converting velocity head into pressure head in the casing itself. The casing is circular and concentric with the impeller which leads to more complete conversion of velocity head into pressure head, resulting in higher efficiency.
One impeller is used- Single stage
2 or more impellers- Multistage-discharge from one impeller enters the eye of the next impeller

7. Deep well turbine pump:
Several impellers are installed on a vertical shaft, which is suspended and rotated from the prime mover motor placed at ground surface. The pump bowls are thus kept below the water level of well.
This type of pump is installed in a well casing of limited size, and the entire assembly has to be of small diameter.
(e) Submersible pump: Difference from the deep well pump is that the driving motor here is placed below the pump bowels within the well water level. Thus, the driving shaft is completely eliminated and the water rises to surface through a riser pipe on which the assembly is suspended. This elimination reduces bearing friction, provides an unobstructed pipe for delivery of water to the surface.

8. centrifugal pumps

9. Priming & operation of centrifugal pumps
 priming consists in filling the pump casing with water, so that the air trapped in the pump does not hinder its operation to reduce its efficiency
 fill the pump with water from an outside source & permit the displaced air to escape through an exhaust valve
 certain pumps are provided with vacuum pumps to remove the air from the casing
 diameter of the pump casing at the inlet & discharge end are often kept smaller than that of the pipe to which pump is connected
 a foot valve should also be fitted at the end of suction pipe
 delivery pipe is often installed with a check valve & a gate valve
 gate valve is opened slowly only after the pump has picked up its full speed & discharge pipe is filled water & full back pressure exists on the pump
 a strainer or a screen is usually provided at the entrance of the suction pipe while pumping raw water

10. Pumps Characteristics of centrifugal pumps
 operating characteristics which depend on its design & speed of operation
 curves are obtained by plotting at constant speed, the variations of head, efficiency, and brake horse power, against the corresponding rate of discharge

11. Pumps Advantages of centrifugal pumps
Initial cost & maintenance cost are comparatively low
Compact size, can be installed in limited space
Simple mechanism, less skilled labour is required for operation & repair
Can be operated with high speed electric motors
Steady discharge
Can be used for pumping water containing silt, sand etc.
Quite durable & safe against high pressures

12. Pumps Limitations of centrifugal pumps Priming is required
Neither be started with discharge valve open nor should the discharge valve be kept closed for longer time after starting the pump
Discharge pipe to be provided with check valve
Discharge varies with the head of water
Efficiency is low at high speeds/high heads
Suction lift is limited

13. Reciprocating pumps (hand pump)

14. Pumps Displacement Pumps: Reciprocating pumps & Rotary pumps
 work on principle of mechanically inducing vacuum in a chamber, sucking in a certain volume of water, which is then mechanically displaced & forced out of the chamber
Reciprocating pumps: now a days outdated except small hand pump

15. Pumps Advantages of reciprocating pumps
Discharge rate depends only on the speed with which the piston is moved & independent of head
 gives constant discharge under variable heads
 useful for very high & variable heads with low discharges
Durable & flexible
High efficiency is possible, provided the valves & the packings are in good condition

16. Pumps Disadvantages of reciprocating pumps
Initial cost of installation is high (≈ 4 * that of a centrifugal pump)
Occupy large space (6-8 times more compared to centrifugal pumps)
Needs skilled supervision during operations
Unsuitable for pumping waters containing sediments
Pulsating flow (i.e. flow with jerks)
Maintenance charges are high

17. Pumps
Rotary pumps

18. Rotary pumps Disadvantages Advantages Initial cost is high
They are not durable, as they require replacement of their gears
Water containing sediments are injurious to pumps (Abrasion will destroy seal between the gear and the casing)
Advantages
They do not require any priming.
Flow from such a pump is free from pulsations.
They don’t have valves. simple to construct and easy to repair.
Efficiency is high at low heads for smaller discharges of liters per minute.

19. Pumps Miscellaneous Types of Pumps: Air lift pumps
 compressed air is forced into the well through a small air pipe & released through a diffuser into the education pipe at the bottom of the well
 air rises in small bubbles in the education pipe forming a mixture of air & water
 resulting mixture of air & water inside the education pipe is lighter than the water outside the pipe, hence is forced upward by hydrostatic pressure
 a separator is often placed at the outlet, so as to remove air, from water
(reclaimed air is generally cooler than the atmospheric air & can be compressed more cheaply)
 can be used for high lifts upto about 150 m but efficiency is generally low
 effectiveness of an air lift pump is measured by percentage submergence
NOTE:
(a) Air lift pump will operate at best efficiency if % submergence ≈ 70%
(b) % submergence should be atleast 25% to operate the pump even at low efficiency
Where, Ds = depth of submergence
He = effective lift of pump
Ds+He  effective length of education pipe

20. Air lift pumps
Used for pumping water form deep wells for lifts about 60-80m.
These pumps can be used for high lifts upto 150mts but their efficiency is low.
Effectiveness of an air pump measured by factor called percentage of submergence.

21. Pumps Advantages of air lift pumps
Can deliver large amounts of water from small diameter wells
Not harmed by sedimented water
Cheaper, reliable & simple in operation
No moving parts of the pump is in contact with water (can be used for highly acidic or alkaline waters)
Pumping from no. of wells can be done by installing a common compressor unit
Yield of well can be increased by using more amount of compressed air

22. Pumps Disadvantages of air lift pumps
To obtain sufficient value of % submergence, depth of submergence has to be increased, thus well has sometimes to be made deeper than required. This increases the cost
Generally not adopted for raising water much above the ground level
Low efficiency
Intermittent flow
Less flexible in fulfilling variable demands

23. Miscellaneous Types of Pumps:
(ii) Jet pumps
 low efficiency
 compact & light weight, portable & easy to handle
Used for pumping water small wells
Used in dewatering trenches

24. Miscellaneous Types of Pumps:
Hydraulic ram
 does not require any outside power
 based on principle of water hammer pressures (developed when a moving mass of water is suddenly stopped)
 suitable for small water supply projects
 installed at lower levels than the source

25. Pumps Advantages of hydraulic ram
Simple working, once starts functioning, practically no attention is required
Durable
Cheap as no fuel is required
Considerable amount of water is wasted (wasted water : pumped water :: 6:1 to 2:1, depending upon the supply head, lift etc)
Produces considerable noise while working

26. Hydraulic ram Pumping arrangement which does not utilize outside power
Worked on principle of water hammer pressures

27. Factors affecting the selection of a particular type of pump
Capacity of pumps
Importance of water supply scheme
Initial cost of pumping arrangement
Maintenance cost
Space requirements for locating the pump
No. of units required
Total lift of water required
Quantity of water to be pumped
Quality of water
Reciprocating pumps are outdated now a days
Centrifugal pumps are frequently used

28. Pumps Head, Power & Efficiency of Pumps H = Hs + Hd + HL
Where, H = total head
Hs = suction lift
Hd = delivery head
HL= head lost due to friction
Work done by the pump in lifting Q cumecs of water by a head H
= γw . Q. H
Water horse Power,
Brake Horse Power,

29. Pumps Economical Diameter of the Pumping Mains
An empirical formula given by Lea,
where, D = economical dia in m
Q = discharge to be pumped in cumecs
It gives, optimum flow velocity: 0.8 – 1.35 m/s
To reduce cost of pipe
Reduce dia
Increased flow velocity
Increased pumping cost
Higher frictional loss

30. Economical Diameter of the Pumping Mains
Pumps
Economical Diameter of the Pumping Mains
Annual cost
Economical dia
Lowest cost
Size of pipe

31. PUMPING STATIONS
While selecting a location for pumping station, the following points should be kept in mind.
The site should be away from sources of contamination or pollution.
It should be above the HFL of river.
It should have potential for future growth and expansion.
The pumping machinery is able to draw sufficient water so as to meet the peak demand during busy times.
Possibilities of fire hazard must be considered.
The proximity of site to railways must be ensured to get coal for power production.

32. Setting of Pumps
Placed either below the level of water in sump well or above it.
Piping and Valves at the Pumping Stations
Sizing of the pump units and the standby capacity