82 



BULLETIN 414, U. S. DEPAETMENT OF AGRICULTURE. 



sure required to operate the pump. It is placed in the air pipe line 

 between the air tank and the pneumatic pump, and can be adjusted 

 to the proper pressure with an ordinary wrench. The working pres- 

 sure required to operate the pump and raise water to the required 

 height is recorded on the pump gauge placed on the air pipe line 

 between the reducer and the pump. The pressure necessary may be 

 determined by the use of Tables 9 and 10, as described under the 

 hydropneumatic system. 



The size of tank that should be installed is governed both by the 

 quantity of water to be delivered with one charging and by the pres- 

 sure necessary to overcome the friction in pipes and fittuigs and to 

 deUver the water at the required elevation. The following table 

 shows the number of gallons of water that can be drawn from faucets 

 with the pump under working pressures varying from 25 to 55 poimds, 

 and with total starting pressures in a 1,000-gallon air tank varying 

 from 60 to 100 pounds. 



Table 12. — Pumping capacity of a 1,000-gallon air tank, in gallons of water, under 



varying internal pressures. 



Pressure 



Initial pressure in pounds in 1 



,000-galIon 



air tank. 



main- 

 tained in 























pump by 













pressure 



60 



70 



80 



90 



100 



reducer. 













Pounds. 



Gallons. 



Gallons. 



Gallons. 



Gallons. 



Gallons. 



55 



40 



155 



270 



415 



550 



50 



140 



270 



400 



550 



700 



45 



240 



385 



530 



685 



850 



40 



340 



500 



660 



820 



1,000 



35 



470 



650 



830 



1,010 



1,200 



30 



600 



800 



1,000 



1,200 



1,400 



25 



737 



918 



1,239 



1,350 



1,618 



For air tanks of other than 1,000-gallon capacity the amount of 

 water which can be dehvered with one charging can be obtained 

 approximately by dividing the figures in the table by 1 ,000 and multi- 

 plying the result by the capacity of the tank in gallons. 



For the purpose of the assumed camp of 40 convicts, an air-tank 48 

 inches in diameter and 14 feet long (the same size as the hydropneu- 

 matic tank selected) wiU supply all the water necessary for a day's 

 consumption with one charging. Its volume, by Table 11, is found 

 to be 1,300 gallons and if it is charged to an initial pressure of 100 

 pounds per square inch, and the pressure reducer set at 25 pounds per 

 square inch. Table 12 indicates that the volume of water which can be 



dehvered at one charging wiU be r-|™X 1300 = 2,103 gallons. 



When the same tank was used as a hydropneumatic tank, it was 

 found that it would be necessary to charge it twice a day, which indi- 

 cates an advantage in point of convenience in favor of the pneumatic 



