368 



THE IRRIGATION AGE. 



PUMPING PLANTS FOR IRRIGATORS 



The University of Arizona in an 8-page brochure 

 by G. E. P. Smith, entitled "Timely Hints for Fann- 

 ers, No. 67," makes the following suggestions of great 

 value to those contemplating the installation of pump- 

 ing plants, and to those whose present plants are un- 

 satisfactory. 



In the first place the location of the well demands 

 attention. In many places the water table slopes so 

 rapidly that in conjunction with the surface slope it 

 dictates the location of the well that will have the 

 lowest lift. Often differences in the water-bearing 

 character of the formations nearby are the basis for 

 decision. Especially is this true in narrow river 

 valleys. 



Shallow wells of great lateral dimensions are com- 

 mon in parts of Arizona. In places where shallow 

 gravel beds are underlain by non-water-bearing strata 

 they are justifiable. But more often the depths of the 

 gravel beds are greater than can be reached by such 

 wells, in which case drilled wells are far more effective 

 in developing water. They cut across the bedding 

 planes and tap more strata than a dug well, and since, 

 as is well known, waters percolate along beds of un- 

 consolidated gravels far more easily than in a vertical 

 direction, the drilled wells are the best yielders. 



Casings for drilled wells may be of the California 

 "stovepipe" type, or, if the soil material is quite uni- 

 form and not too coarse, and short holes under fifty 

 feet are desired, then the Kansas method can be used. 

 This consists in punching slots, perhaps %xl inch in 

 size, in heavy galvanized iron, and riveting the sheets 

 into cylinders with the burr on the outside. Such 

 wells, is inches in diameter and 20 to 40 feet long, make 

 excellent feeders in the bottom of a dug well. 



PUMPS. 



The advantages of the centrifugal pump for the 

 individual irrigator are so conspicuous and its adop- 

 tion so general that the discussion will be confined to 

 that type. 



Pumps are usually purchased wholly on the repu- 

 tation of the makers and without regard to details of 

 construction. Little will therefore be said regarding 

 these features. Both open and closed runners give 

 high efficiencies if well designed and built. Much de- 

 pends on whether the channels and blades are finished 

 or left rough. Machining these surfaces adds materi- 

 ally to the cost but greatly reduces the friction and 

 eddying of the water. In the best pumps the im- 

 peller, if enclosed, is cast in two pieces, and all sur- 

 faces of impeller and casing are machined and pol- 

 ished. Many pumps have only the runner machined. 

 There are also many makes of pumps which are left 

 entirely rough. These last are of very poor construc- 

 tion, verv inefficient, and should not be purchased. 

 The bearings of the pump shaft, or at least the outboard 

 bearing:, should be self-oiling of the ring-oiling type, 

 end thrust should be compensated, and the packing 

 gland should be of approved construction. 



Where electric power is available, pump and 

 motor should be direct connected on the same bed 



plate. Such a plant requires the very minimum of 

 attention and should give a combined efficiency ex- 

 ceeding 48 per cent. Such a unit can be set deep in a 

 well pit, just above the water level. 



If the water table fluctuates greatly between wet 

 and dry seasons a horizontal pump must either be set 

 so high that the suction is apt to be too great or else 

 it runs a risk of being submerged. A vertical pump 

 can be run submerged and is especially adapted to 

 cases in which the water table rises and falls greatly 

 or to cases where the water level drops to the limit 

 of suction when pumping begins. It is advisable to 

 keep the suction lift less than 12 feet. If this can- 

 not be done with a horizontal pump, then a submerged 

 vertical pump should be installed. 



Centrifugal pumps are exceedingly sensitive to 

 change of speed and in each installation the most effi- 

 cient speed should be determined and then maintained. 

 A revolution counter should be purchased with every 

 pump. Overspeeding may be justifiable sometimes, but 

 never should the speed fall below the best speed. 



Deep well pumps should be used in drive wells if 

 the water level is at a considerable depth and the well 

 is driven from the surface of the ground. Pumping 

 by air lift is entirely feasible, though of low efficiency. 

 A greater draught may be made upon a poor well by 

 an air-lift than by any other method, but the cost of 

 pumping is high and air lifts are not recommended 

 where the lift exceeds 80 feet. 



POWER. 



The choice here is very wide. Gasoline and steam 

 engines occupy the field at present, but in a few locali- 

 ties in Arizona electric power is available. Suction 

 gas producers, hot air engines, and internal combus- 

 tion engines using crude oil give promise of coming 

 into use. Suction gas producers, especially, are well 

 adapted to Arizona conditions, and will furnish 

 cheaper power than any other type of plant except 

 water power. They are only available for plants larger 

 than fifteen horsepower. 



Large irrigating plants should have a competent 

 engineer. An efficient steam plant burning crude oil 

 or New Mexican coal is at the present time preferred. 



The small irrigator is usually not a mechanic and 

 besides he is a very busy man. He needs an engine 

 which will work with a minimum of attendance and 

 repairs. A breakdown in the dry season may mean 

 ruin. Small differences in efficiency are often out- 

 weighed by other considerations. The greatest care 

 should therefore be taken to select an installation which 

 will give the least possible trouble afterwards. 



The symmetry of a pumping plant deserves far 

 more consideration than it usually receives, especially 

 in the case of gasoline plants where the fuel bill is the 

 principal item in the cost of pumping. If the engine 

 is too light the speed of the pump is too low; if the 

 engine is too larsre its own efficiency is teatly reduced. 

 Both engine and pump should work up. to full rated 

 capacity, or nearly so. 



The symmetrical design of a pumping plant is 

 not a simple matter. One unfortunate irrigator in the 

 Santa Cruz Vallev was recently observed to have around 

 his well two boilers, two engines, and three pumps. 

 He stated further that he had sent for a fourth pump 



