Science of Water : Concepts and Applications

Water Treatment Calculations 333
Example 10.15
Problem:
Given the data below, calculate the fi eld effi ciency of the deep-well turbine pump.
Field head—180 ft
Capacity—850 gpm
Total bhp—61.3 bhp
Solution:
(field head, ft)(capacity, gpm)
Field efficiency, %
100
(3960) (total bhp)
(180 ft)(850 gpm)
100
(3960)(61.3 bhp)
63%
The overall effi ciency is a comparison of the horsepower output of the system with that entering
the system. Equation 10.15 is used to calculate overall effi ciency:
Example 10.16
(field efficiency, %)(motor efficiency,
%)
Overall efficiency, %
100
Problem:
The effi ciency of a motor is 90%. If the fi eld effi ciency is 83%, what is the overall effi ciency of
the unit?
Solution:
WATER STORAGE
(field efficiency, %)(motor efficiency,
%)
Overall efficiency, %
100%
100
(83)(90)
100
74.7%
(10.15)
Water storage facilities for water distribution systems are required primarily to provide for
fl uctuating demands of water usage (to provide a suffi cient amount of water to average or equalize
daily demands on the water supply system). In addition, other functions of water storage facilities
include increasing operating convenience, leveling pumping requirements (to keep pumps
from running 24 h a day), decreasing power costs, providing water during power source or pump
failure, providing large quantities of water to meet fi re demands, providing surge relief (to reduce
the surge associated with stopping and starting pumps), increasing detention time (to provide
chlorine contact time and satisfy the desired CT (contact time), value requirements, and blending
water sources.