Aug. 1, 1925 
Tests of Deep-Well Turbine Pumps 
243 
be neglected. Maximum speed occurs at the point of zero discharge, 
and in this particular instance the speed gradually lowers as the 
capacity of the pump increases. 
ISO-EFFICIENCY CURVES 
For practical use the data, first plotted in the form of characteristic 
curves, have been translated into the form of performance curves 
(figs. 10, 11, 12, 13, 14, 15, and 16). 
In the selection of a pump, the pumping head is the first considera¬ 
tion; next is the desired capacity. For example: Assume that the 
pumping head is 105 feet and the desired capacity is 800 gallons per 
minute. With a 24-inch, 3-stage pump of the make corresponding 
Gallons per Minute 
Fig. 11—Performance curves, pump No. 2 
to curves in Figures 9 and 10, an average speed of 898 revolutions per 
minute would give the best efficiency. At this speed a range of 
capacity of 500 to 1,000 gallons per minute would be possible without 
reducing the efficiency much below 60 per cent. For the set of 
conditions assumed, the power for 800 gallons per minute would be 
approximately 31.5 horsepower. 
The curves emphasize tne importance of considering the efficiency 
of the pump in relation to its speed. Intending purchasers should be 
impressed with the fact that the various types and makes of pumps 
have different characteristics, and that a hydraulic engineer, well 
versed in the performance of pumps, should be consulted before 
expensive pumping equipment is bought. 
