Science of Water : Concepts and Applications

Water Treatment Calculations 329
Then, determine the pounds of chlorine required using the mg/L to lb equation:
Chlorine, lb (chlorine, mg/L)(volume, MG)(8.34 lb/gal)
(50 mg/L)(0.000290
MG)(8.34 lb/gal) 0.12 lb chlorine
Deep-Well Turbine Pump Calculations
The deep-well turbine pump is used for high-capacity deep wells. The pump, consisting usually
of more than one stage of centrifugal pump, is fastened to a pipe called the pump column; the pump
is located in the water. The pump is driven from surface through a shaft running inside the pump
column. The water is discharged from the pump up through the pump column to surface. The
pump may be driven by a vertical shaft, electric motor at the top of the well, or by some other power
source, usually through a right angle gear drive located at the top of the well.
A modern version of the deep-well turbine pump is the submersible-type pump in which the
pump, along with a close-coupled electric motor built as a single unit, is located below water level
in the well. The motor is built to operate submerged in water.
Vertical Turbine Pump Calculations
The calculations pertaining to well pumps include head, horsepower, and effi ciency calculations.
Discharge head is measured to the pressure gage located close to the pump discharge fl ange.
The pressure (psi) can be converted into feet of head using the equation:
Discharge head, ft (pressure,
psi)(2.31ft/psi)
(10.5)
Total pumping head (fi eld head) is a measure of the lift below the discharge head pumping
water level (discharge head). Total pumping head is calculated as follows:
Pumping head, ft pumping water level, ftdischarge head, ft
(10.6)
Example 10.8
Problem:
The pressure gauge reading at a pump discharge head is 4.1 psi. What is this discharge head expressed
in feet?
Solution:
(4.1 psi)(2.31 ft/psi) 9.5 ft
Example 10.9
Problem:
The static water level of a pump is 100 ft. The well drawdown is 26 ft. If the gauge reading at the pump
discharge head is 3.7 psi, what is the total pumping head?
Solution:
Total pumping head, ft ( pumping water level, ft) (discharge
head, ft)
(100 ft 26 ft) (3.7
psi)(2.31 ft/psi)
126 ft 8.5 ft
134.5
ft
(10.7)