Handbook of Civil Engineering Calculations

FIGURE 12. Pump performance curve (A If a Laval Pumps, Inc.)

TDH was calculated above to be 26 lb/in^2 (179.1 kPa); Sf= (25 gal/100 revs)(0.757) + 3 =

21.925.

4. Determine the pump horsepower
   The viscosity of a sewage sludge is dependent upon the percent solids and may be found
   using Table 3.
   Using Table 3, a 5 percent solids sludge has a viscosity of 1,050 cp. Therefore:

Nf= 2.2 Vl,050 cp = 22.36

Using the values outlined above, the motor horsepower is calculated:

HP 175 rpm r (175 rpm)(21.925) (25)(22.36) 1

• -iir K

043

*

25 gai/io

°

revs)(26 psi)+

id*—-

+

^u

2

I

= 1.3hp(0.97kW)

The resulting horsepower of 1.3 hp (0.97 kW) is at best an informed estimate of the horse-

power which will be absorbed at the pump shaft during pumping. It includes no service

factor or margin for error, neither does it allow for inefficiency in power transmission sys-

tems.

Speed -RPM

Test Medium:

top

Displacement:

U.S. gal/1 OO rev

25

Port Size:

3 inches

(76.2 mm)

U.S. GPM (m CAPACITY
3
/hr)