42 



BULLETIN 1061, U. S. DEPARTMENT OF AGRICULTURE. 



motors. Electric energy was used in this case because of the 

 desirability of having the city current for use for other power and 

 in the suburban residences. The cost of electrical energy is greater 

 than that of steam power or that furnished by internal-combustion 

 engines, although the first cost of the electrical plant is less than 

 either of the other types. The plant is very economical when 

 interest on investment and depreciation are considered together with 

 the cost of operating. 



The pumps are equipped with a combination of screw and inclosed- 

 centrifugal impeller. They are primed by means of small exhaust 

 pumps of the chamber-wheel type driven by small motors. Greatest 

 capacity is had at the low lifts, where it is desirable. As the lift 

 increases the capacity decreases, but the need of large capacity also 

 decreases. The capacity of the plant when operating at a lift of 4.5 

 feet is 1.3 inches in depth removed from the area in 24 hours. The 

 motors which drive the pumps run at practically constant speed, and 

 therefore the revolutions of the pump remain constant regardless of 

 lift. 



METHOD OF MAKING TEST. 



The height through which the water was elevated was obtained by 

 reading gages in the suction and discharge basins. The quantity of 

 water was determined by using a Price current'meter in the discharge 

 flume. The voltage and revolutions per minute were also observed. 

 The results of the test are given in Table 36. It is believed that the 

 two units under favorable conditions will show identical results. 



Table 36. — Test of pumping plant in Little Woods Tract, New Orleans, La., Nov. 14, 



1914. 

 UNIT NO. 1. 



Time. 



Speed. 



Volts. 



Actual 

 lift. 



Discharge. 



Kilo- 

 watts. 



Elec- 

 trical 

 horse- 

 power. 



Water 

 horse- 

 power. 



Effi- 

 ciency. 



10.00 



10.15 



10.30 



11.00 



11.15 



3.15 



3.30 



3.45 



4.00 



4.15 



4.30 



R. p. TO. 

 119.8 

 121.2 

 120.7 

 120.7 

 121.2 

 121.4 

 120.8 

 120.5 

 120.7 

 121.1 

 121.0 

 120.7 



2,246 

 2,288 

 2,300 

 2,298 

 2,298 

 2,304 

 2,320 

 2,320 

 2,320 

 2,320 

 2,316 

 2,320 



' Feet. 

 5.76 

 5.83 

 5.85 

 5.85 

 5.87 

 5.91 

 6.29 

 6.39 

 6.41 

 6.44 

 6.46 

 6.54 



Sec.-ft. 

 173.7 

 176.8 

 177.9 

 175.5 

 173.7 

 172.1 

 171.0 

 169.2 

 170.2 

 168.1 

 166.3 

 167.4 



G. p. TO. 



77, 800 

 79,200 

 79. 700 

 78,600 

 77,800 

 77, 100 

 76, 600 

 75, 800 

 76, 200 

 75,300 

 74,500 

 75, 000 



174. C 

 174.9 

 174.8 

 175.1 

 175.0 

 178.0 

 174.4 

 172.6 

 171.6 

 173.4 

 171.0 

 166.4 



233.0 

 234.2 

 234.2 

 234.6 

 234.5 

 238.5 

 233.7 

 231.3 

 230.0 

 232.3 

 229.1 

 223.0 



113.5 



116.8 

 118.0 

 116.2 

 115.5 

 115.3 

 121.8 

 122.7 

 123.5 

 122.6 

 121.6 

 124.1 



Per cent. 

 48.80 

 49.75 

 50.35 

 49.50 

 49.25 

 48.35 

 52.10 

 53.10 

 53.70 

 52.75 

 53.10 

 55.70 



Mean.. 



120.8 



2,304 



6.13 



171.4 



76, 960 



173.4 1 232.4 



117.6 



51.37 











UNIT NO. 2.1 











1.15 



1.30 



1.45 



2.00 



2.15 



120.4 

 121.1 

 12X8 

 121.0 

 12X8 



120.8 



2,300 

 2,308 

 2,310 

 2,310 

 2,320 



6.10 

 6.14 

 6.15 

 6.20 

 6.25 



170.2 

 171.5 

 171.2 

 167.0 

 169.2 



73, 200 

 73, 890 

 76,700 

 74, 800 

 75,800 



176.5 

 178.0 

 176.1 

 174.0 

 173.0 



233.5 

 238.5 

 236.0 

 233.0 

 231.8 



117.5 

 119.3 

 119.2 

 117.3 

 120.0 



49.7 

 50.0 

 50.5 

 50.4 

 50.47 



Mean.. 



2,310 



6.15 



169.8 



76, 060 



175.5 



235.2 



118.7 



50.47 



1 A mud lump was found in suction basin under one suction pipe. 



