PUMPS AND PUMPING STATIONS
I. To lift the water from source to the treatment plant which is at higher level compared to the source
II. To lift the treated water to the elevated tanks
III. To increase the pressure in the distribution system.
IV. To lift the water at the treatment plant if sufficient natural ground slope is not available as to cause gravitational flow between different units of treatment plants.
Classification of Pumps
Based on their Principal of power required
i. Displacement pumps
iii. Airlift pumps
iv. Impulse pumpsiv.Diesel engine pumps
v. Stand by pumps
Based on the type service
i.Electrically driven pumps
ii. Gasoline pumps
iii. Steam engine pumps
Based on the type of operation
i. Low lift pumps
ii.High lift pumps
iii.Deep well pumps
Under most of the situations in water supply scheme, displacement and centrifugal pumps are commonly used.
i. Reciprocating pumps
ii. Rotary pumps
The location of a pumping station is primarily governed by the place where it is to recerive water. The points to be kept in mind while selecting a suitable site are.
i. The site should be away from all the sources of contamination or pollution
ii. The site should be above the HFL of the river.
iii. Its future growth and expansion is easily possible
iv. Possibility of fire hazards is also to be considered
FACTORS AFFECTING THE SELECTION OF A PARTICULAR TYPE OF PUMP
1. Capacity of pumps
2. Importance of WSS
3. Initial cost of pumping arrangement
4. Maintenance cost
5. Space requirements for locating the pumps
6. Number of units required
7. Total life of water required
8. Quantity of water to be pumped.
HEAD POWER AND EFFICIENCY OF PUMPS
The total head against which a pump works is made up of
i. The suction Head(Hs)
ii. The Delivery Head(Hd)
iii. The Head loss due to friction entrance and exit in the rising main(Hf)
The suction HEAD is the difference in elevation between the low water level and center line of pump.
Delivery HEAD is the difference in elevation between the pump center line and point of discharge
Total HEAD (H) =Hs+Hd+Hf
The work done by the pump in lifting „Q? cumecs of water by a head(H) =WQH kg-m/sec. Where,
W = Specific weight of water, 1000 kg/m3 Q = discharge to be pumped, m3/sec.
The water horse power of the pump is given by
WHP(out put) = WQH/75
If „n? is the efficiency of the pump then
BRAKE HORSE POWER of the pump is given by
BHP(INPUT) + WQH/75n
ECONOMICAL DIAMETER OF THE RISING (PUMPING) MAIN
The economical diameter is a particular size of the pumping or rising main which while passing a given discharge of water gives the total annual expense to be minimum.
If the diameter chosen is more than the economic dia, it will lead to higher cost of the pipe line on the other hand, if the dia of the pipe is less than the economical dia, the increased velocity will lead to higher friction headless and require more HP for the required pumping and the cost of pumping shall be much more than the resultant saving in the pipe cost.
An empirical formula given by LEA
Connecting the dia and discharge is given by
D = 0.97 to 1.22 SqRt(Q)
D = economical diain m
Q = Discharge to be pumped in cusecs
This relation gives optimum flow velocity varying between 0.8 to 1.35m/sec
FOR RIGOROUS ANALYSIS The total cost of pipe and pumping should be woeked out at different assumed velocities (b/w 0.8 to 1.8m/sec) and a graph plotted between the annual cost and the size of the pipe. The economical size is one which gives the least annual cost.
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