Science of Water : Concepts and Applications

Water Treatment Calculations 331
The water horsepower can now be determined:
Example 10.11
(158.1 ft)(700 gpm)(8.34 lbgal)
33,000 ft-lbmin 28 whp
Problem:
The pumping water level for a pump is 170 ft. The discharge pressure measured at the pump discharge
head is 4.2 psi. If the pump fl ow rate is 800 gpm, what is the water horsepower? (Use Equation 10.12.)
Solution:
The fi eld head must fi rst be determined. To determine fi eld head, the discharge head must be converted
from psi to ft:
The fi eld head can now be calculated:
Then the water horsepower can be calculated:
(4.2 psi)(2.31 ft/psi) 9.7 ft
170 ft 9.7 ft 179.7
ft
(179.7 ft)(800 gpm)
whp
3960
36 whp
Example 10.12
Problem:
A deep-well vertical turbine pump delivers 600 gpm. If the lab head is 185 ft and the bowl effi ciency is
84%. What is the bowl horsepower? (Use Equation 10.11.)
Solution:
Example 10.13
Problem:
(bowl head, ft) ( capacity, gpm)
Bowl bhp
(3960)(bowl efficiency100)
(185 ft 600
gpm)
(3960)(84.0100) (185600 gpm)
(3960
0.84)
33.4 bowl bhp
The bowl bhp is 51.8 bhp. If the 1-in. diameter shaft is 170 ft long and is rotating at 960 rpm with a shaft
fi ction loss of 0.29 hp loss per 100 ft, what is the fi eld bhp?