238 



THE IRRIGATION AGE. 



POWER IRRIGATION 



BY E. C. REYBOLD, JR. 



ELECTRIC PUMPING. 



When one is about to pump for irrigation purposes, 

 and electricity can be secured at reasonable rates, there 

 is no need for hesitation. With a well designed steam 

 or gasoline plant but little trouble is experienced, but 

 even at that there is no comparison between such power 

 and electricity that can be favorable to the former if 

 electricity can be purchased at a cost equal to the cost 

 of fuel and labor. If a pumping plant operated by 

 steam or producer gas is of considerable size (say 50 

 h. p. or more), and is well designed, electricity must 

 be sold at a very low rate to compete with coal at less 

 than $4.00 per ton. The above conclusions are from a 

 financial standpoint only, as there is always a great ad- 

 vantage in favor of electricity when the petty annoyances 

 and troubles usually experienced with steam, gasoline or 

 producer plants are considered, not the smallest of which 

 is that of delivery of fuel to the power plant. 



From the standpoint of the individual farmer it is 

 scarcely necessary to consider any 

 plant of more power than about 25 

 h. p. which will pump sufficient 

 water for a section of land lying 20 

 feet above the source of supply, or 

 for half a section lying 40 feet high. 

 And if electricity can be secured at 

 present prices throughout the West 

 2 cents to 3^ cents per kilowatt- 

 hour for pumping purposes electric 

 pumps are to be recommended. 

 When a number of land owners to- 

 gether install a large pumping plant 

 the kind of power to be used de- 

 pends entirely upon the precise con- 

 ditions at hand, and although elec- 

 tricity is always used wherever pos- 

 sible, it does not have the clear field 

 that it does for small individual 

 plants. 



Electric motors are used quite 

 generally for running working heads 

 placed over deep or shallow wells, 

 and but few windmills that are blown 

 down in a section where electricity is obtainable are re- 

 placed. Such pumps will deliver ample water for resi- 

 dences and barns, but they are insufficient in capacity 

 for irrigating any more than a small tract of land. 



Rotary pumps are also frequently driven by motors, 

 but gears must be used on account of the slow speed of 

 the pumps. 



Motors are peculiarly adapted to driving centrifugal 

 pumps on account of the high speed of each, and as a 

 major portion of all power irrigation is accomplished 

 with such pumps, the combination is a fortunate one. 

 Either horizontal or vertical centrifugal pumps may be 

 driven by belts, but the ideal unit consists of a motor 

 direct-connected to a pump of similar speed. The loss 

 of power in the belt is thus obviated, and much floor 

 space saved. Vertical centrifugal pumps are often di- 

 rect-connected to motors with vertical shafts, a flexible 

 coupling being used between in order that the motor 



may be required to carry only the weight of its own 

 revolving parts. Vertical motors are more expensive 

 than horizontal, and such units are not frequently used. 



The most desirable combination of all consists of 

 a horizontal centrifugal pump direct-connected to a 

 motor that is mounted upon the same bed plate. A 

 flexible leather link coupling should be used between in 

 order that neither shaft may exert any strain upon the 

 other, and that the motor armature may float as it de- 

 sires. The end thrust of the pump should be com- 

 pensated by special bearings and collars, or better by 

 the special automatic water balance used by some manu- 

 facturers. The pump should be equipped with one or 

 two ring-oiling bearings, the latter being essential with 

 pumps of very large size. All motors have two ring- 

 oiling bearings, and the matter of lubrication of hori- 

 zontal motor operated units is of small consequence. 

 - The same is not true of vertical units. 



The open type of runner is used by some manu- 

 facturers, but the enclosed type is rapidly coming into 

 general use. 



The speed of rotation of a centrifugal pump is de- 

 termined by the head against which it operates, and the 

 diameter of the runner, varying directly as to the square 

 root of the head, and indirectly as to the diameter of 



Horizontal Centrifugal Pump Direct-Connected to Motor." 



the runner. If a motor of a certain speed is to be di- 

 rect-connected to a pump, the runner must be properly 

 proportioned for the head against which it must op- 

 erate, and for the quantity of water to be discharged. 

 Alternating current is used almost entirely for irrigation 

 work, and such motors may be obtained running at any 

 one of about six speeds, their cost decreasing with the 

 increase of speed. The majority of motor manufac- 

 turers make motors of each size in but two or three 

 speeds for standard types, although they are prepared 

 to make them at any synchronous speed on special or- 

 der. When once selected the speed cannot be changed. 

 The above applies only to induction (alternating cur- 

 rent) motors, as it is usually possible to obtain a direct 

 current motor running at any reasonable speed, and it 

 is also possible to change the speed of such a motor 

 without great difficulty. Induction motors do not have 

 brushes or commutators, as do direct current, and there 



