Before the selection of a particular pump, there are various factors which must be kept in view.
Broadly, following are the main factors which should be considered while doing selection of pump for a particular scheme:
1. Capacity:
It should be capable of pumping required quantity of water.
ADVERTISEMENTS:
2. Reliability:
It should be reliable and should not fail suddenly and cause trouble.
3. Cost:
It should be cheap in initial cost.
ADVERTISEMENTS:
4. Power:
The power which is used for running pumps should be available easily at low cost.
5. Maintenance:
The maintenance cost of running pumps should be as small as possible.
ADVERTISEMENTS:
6. Efficiency:
Pump should have high efficiency.
7. Depreciation:
It should have long life and depreciation cost should be small.
ADVERTISEMENTS:
8. Cost of labour:
It should be low.
9. Number of pumping:
Units required.
ADVERTISEMENTS:
10. Total lift of the water required.
11. Quality of water to be pumped.
In addition to the above points, pumps should require less floor area; can meet variation in load; have flexibility in operation can be easily started and should have high suction lift. Mostly centrifugal pumps are used in all water-works, because they are most satisfactory, economical than all other types of pumps, for pumping water from wells.
When the water contains suspended impurities, air lift pumps are found most satisfactory. Reciprocating pumps are suitable when the water is to be pumped against high but variable head with higher suction lift. Reciprocating pumps can only be used for pumping very clear water, because if water contains suspended particles, it will interrupt in the working of the pumps.
Now a days the reciprocating pumps are out-dated. For all the ordinary pumping centrifugal pumps should be used, as they work satisfactorily and require less maintenance. For small discharge rotary pumps may be used as they are equally good to centrifugal pumps.
Against very high head but variable head higher suction lift reciprocating pumps may be used. Horizontal spindle centrifugal pumps are very commonly used. As these pumps require priming if placed above the water, hence if large quantity of water is to be pumped, as far as possible these pumps should be kept under water.
If the water’s to be taken from number of wells at a time, the air lift pump may be cheapest, as one compressor unit will operate all the air lift pumps. But the efficiency of these pumps is low.