Water Treatment Processes - Mathematics and Statistics for the Environment - page 608

• Bowl or laboratory horsepower refers the horsepower at the entry to the pump bowls. The
following equation is used to calculate bowl horsepower:

Bowl head (ft)Capacity (gpm)

Bowl efficiency 100

×

Bowl horsepower (lab horsepower) = (23.11)

3960 (

)

×

• Water horsepower refers to the horsepower at the pump discharge. The following equation
is used to calculate water hp:

Fieldhead (ft)Capacity ( × gpm)

Water horsepower = (23.12)

3960

or the equivalent equation

Fieldhead (ft)Capacity ( × gpm)

Water horsepower =

33,000 ft-lb/min

■ EXAMPLE 23.10
Problem: The pumping water level for a well pump is 150 ft and the discharge pressure measured
at the pump discharge centerline is 3.5 psi. If the flow rate from the pump is 700 gpm, what is the
water horsepower?

Solution: First calculate the field head. The discharge head must be converted from psi to ft:

3.5 psi × 2.31 ft/psi = 8.1 ft

The field head is, therefore,

150 ft + 8.1 ft = 158.1 ft

The water horsepower can now be determined:

158.1 ft × 700 gpm × 8.34 lb/g al

Water horsepower = = 28

33,000 ft-lb/min

■ EXAMPLE 23.11
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 flow rate is 800 gpm, what is the water horsepower?

Solution: The field head must first be determined. In order to determine field head, the discharge
head must be converted from psi to ft:

4.2 psi × 2.31 ft/psi = 9.7 ft

The field head can now be calculated:

170 ft + 9.7 ft = 179.7 ft