IRRIGATION
TECHNOLOGY BITS |
Pumps and discharge One HP Pumpset gives a discharge of about 2200 gallons per hour. Discharge rates according to the size of pumpsets: 1 HP (1"X 1", 1.5" X 1.5") : 2000 - 3000 gph 1.5 HP (1.5" X 1", 2"X1.5") : 3000 - 4000 gph 2 HP (2"X2", 2.5" x 2", 3X3.5) : 5000 - 6000 gph 3 HP (2.5" X 2". 3" X 2.5") : 6000 - 7000 gph 5 HP (4" X 3". 3" x 2.5".2.5 X 2) : 1000 - 12000 gph. While erecting a pump 1. Maximum suction head shall not exceed 7 meter (20 ft). Suction head is measured from water surface of source to pump level vertically. 2. Suction pipe shall be erected vertically, it shall never be allowed in a slanting position. 3. There shall not be any leak on the suction side. 4. Foot valve must rest atleast one metre above the water bed. If foot valve touches ground, it will suck dirt and sand, and pumping to avoid frictional loss. 5. Polythene pipes are preferable to avoid frictional loss. 6. Usually centrifugal pumps are used where suction is less than 7 m. A single stage pump is used where total head (suction head + delivery head) is not more than 40 ft (13 ms). Stage pump @ 1 stage for every 40 ft. may be used. Thus for 120 ft. total head, a three stage pump shall be used. 7. Where suction head is more than 20 ft. Ejecto pumps (jet pumps) shall be used. A jet pump will pump water from wells upto 100ft deep. 8. Single phase pumpsets are available upto 1.5 HP. Above 2 HP. only three phase pump sets are available. So small farmers having an area upto 3 acres may go for single phase pumpsets rather than 3 phase to avoid 3 phase electric connection which may not be readily available. Commanding potential of pumpsets 1 HP upto 2 acres 2 HP upto 4.4 acres 3 HP upto 5 acres Area and depth of irrigation A 5 HP pumpset gives an approximate discharge of 11000 gph. If this pump is worked for 10 hours it gives a discharge of 110000 gallons of water approximately. If the area of the farm is 5 acreas the depth of water will be 110000/22000 which is 5 inches. (22000 gallons = 1 inch in 1 acre). Calculation bits 1 cubic metre of water weights : 1 tonne or 1 MG 1 cubic metre per second : 1 cusec. 1 atm. at sea level : 10 metre column of water 1 HP : 75 kg m s-1, 746 watts 1
cm column of water of height 10 m exerts a pressure of 1 kg/cm2 |