Water Source and Storage Calculations - Basic Mathematics for Water and Wastewater Operators - page 226

Solution: Use Equation 15.11 to calculate the bowl horsepower:

Bowl head (ft)Capacity (gpm) ×

Bowl bhp =

3960 × ( Bowl efficiency/100 )

185 ft ×

×

600 gpm 185 ×

×

600
84

= = = 33.4 bowlhp

3960 ( 84/100 ) 3960 0 .

■ Example 15.13
Problem: The bowl bhp is 51.8. If the 1-in.-diameter shaft is 170 ft long and is rotating
at 960 rpm with a shaft friction loss of 0.29 hp loss per 100 ft, what is the field bhp?

Solution: Before field bhp can be calculated, the shaft loss must be factored in:

0.29 hp loss × 170 ft

= 0.5 hp loss

100

Now the field bhp can be determined:

Field bhp = Bowl bhp + Shaft loss (hp) = 51.8 + 0.5 = 52.3 bhp

■ Example 15.14
Problem: The field horsepower for a deep-well turbine pump is 62 bhp. If the thrust
bearing loss is 0.5 hp and the motor efficiency is 88%, what is the motor input
horsepower?

Solution:

Total bhp
Motorefficiency/100

62 b hp + 0.5 hp

Motorhp = = = 71 mhp

088 .

When we speak of the efficiency. of any machine, we are speaking primarily of
a comparison of what is put out by the machine (e.g., energy output) compared to
its input (e.g., energy input). Horsepower efficiency, for example, is a comparison of
horsepower output of the unit or system with horsepower input to that unit or sys-
tem—the unit's efficiency. There are four types efficiencies considered with vertical
turbine pumps:

• Bowl efficiency

• Field efficiency

• Motor efficiency

• Overall efficiency