ABOUT SELECTING PUMPSETS


1 H.P Pumpset gives a discharge of 2200 gallons/hr. normally. Viz. 22,000 gallons in 10 hrs (1 inch of water in one acre - 1 acre inch).

Discharge according to size of pumpset

1 H.P., 1" x 1", 1 1/2" x 1 1/2" pumpsets - 2,000 - 3,000 gph.

1 1/2 H.P., 1 1/2" x 1", 2" x 1 1/2" pumpsets - 3,000 - 4,000 gph.

2 H.P., 2" x 2", 2 1/2" 2", 3" x 2 1/2" pumpsets - 5,000 - 6,000 gph.

3 H.P., 2 1/2" x 2", 3" x 2 1/2" 2" x 2" pumpsets - 6,000 - 7,000 gph.

5 H.P., 4" x 3", 3" x 2 1/2", 2 1/2" x 2" pumpsets - 10,000 - 12,000 gph.

Working out area and depth of irrigation.

Example: 5 H.P. Pumpset. If this pump is worked for 10 hrs, it gives a discharge of 1,10,000 gallons of water approximately. If the area of the farm is five acres, the depth of water will be 1,10,000/22,000 which is five inches (22,000 gallon = 1 inch in one Acre).

Precautions to be taken while errecting a pump

Maximum suction head, shall not exceed 7 mts. (20 ft). Suction head is measured from water surface of source to pump level vertically.

Suction pipe shall be errected vertically. It shall never be allowed in a slanting position.

There shall not be any leak on the suction side.

Foot valve must rest at least 1 mt. above the water bed. If foot valve touches ground, it will such dirt and sand, and pumping system will fail.

Polythene pipes are preferable to avoid frictional loss.

Usually centrifugal pumps are used where suction is less than 7 mts. A single stage pump is used where total head (suction head + delivery head) isj not more than 40 ft. (13 mts). Stage pump at the rate of 1 stage for every 40 ft. may be used. Thus for 120 ft. total head, a 3 - stage pump shall be used.

Where suction head is more than 20 ft. Ejecto Pumps (Jet pumps) shall be used. A jet pump will pump water from wells upto 100 ft. deep.

Single phase pumpsets are available upto 1.5 H.P. Above 2 H.P., only 3 phase pumpsets are available. So small farmers having an area upto 3 acres may go for single phase pumpsets rather than 3 phase electric connections which may not be readily available.

Area-wise requirements of pumpsets:

(1) H.P. upto 2 Acres (1 Ha.) (2) H.P. upto 4 1/2 Acres (1.5 Ha.) (3) H.P. upto 5 Acres (2 Ha.)

Calculation of H.P. Requirement of Pumpsets

HP = QH/75 E Whero Q = Discharge rate in L/Sec. H = Total Head in metres.

E = Efficiency of the pumping unit (Usually between 60 -75%)

75 = 75 kg ms


Source : Agricultural Engineering Wing, Directorate of Agriculture, Thiruvananthapuram