Pumping Calculations - Basic Mathematics for Water and Wastewater Operators - page 205

v oluMe of B iosolids p uMped (C apaCity )
One of the most common positive-displacement biosolids pumps is the piston pump.
Each stroke of a piston pump displaces or pushes out biosolids. Normally, the pis-
ton pump is operated at about 50 gpm. When making positive-displacement pump
capacity calculations, we use the volume of biosolids pumped equation shown below:

Biosolids pumped(gpm)Gallons pumpedper s = troke

No.ofstrokesper minute

(14.20)

×

( )

2 3

= 0 785 . × D × S troke length × 7.48 gal/ft

× No.ofstrokes perminute

■ Example 14.13
Problem: A biosolids pump has a bore of 6 in. and a stroke length of 4 in. If the
pump operates at 50 strokes (or revolutions) per minute, how many gpm are pumped?
(Assume 100% efficiency.)

Solution:

( 0 785 ) ×

2

7.48 gal/ft 3

Volume = . × D × Stroke length × No.ofstrokesper minute

( ) ×

2 3

= 0 785 . × (0.5 ft) × 0.33 ft × 7.48 gal/ft 50 strokes/minute

= 0.48 gal/stroke × 50 strokes/minute

= 25 gal/min

■ Example 14.14
Problem: A biosolids pump has a bore of 6 in. and a stroke setting of 3 in. The pump
operates at 50 revolutions per minute. If the pump operates a total of 60 min during
a 24-hr period, what is the gpd pumping rate? (Assume the piston is 100% efficient.)

Solution : First calculate the gpm pumping rate:

( 0 785 ) ×

2

7.48 gal/ft 3 Volume = . × D × Stroke length × No.ofstrokesper minute

( ) ×

2 3

= 0 785 . × (0.5 ft) × 0.25 ft × 7.48 gal/ft 50 strokes/minute

= 0.37 gal/stroke × 50 strokes/minute

= 18.5 gal/min

Then convert the gpm pumping rate to a gpd pumping rate, based on total minutes
pumped over 24 hr:

18.5 gpm × 60 min/day = 1110 gpd