Handbook of Civil Engineering Calculations

Htod,m

Oil A - viscosity 400 ttu Oil C- viscosity 900 ssu

Oil B - viscosity 600 ssu Oil O- viscosity 1000 ssu

FIGURE 4. Regenerative pump performance when handling water and oil. (Aurora Pump

Division, The New York Air Brake Company.)

different viscosity oils to be handled by the pump—400, 600, 900, and 1000 SSU. What
effect does increased viscosity have on the performance of the pump?

Calculation Procedure:

1. Plot the water characteristics of the pump
   Obtain a tabulation or plot of the water characteristics of the pump from the manufacturer
   or from their engineering data. With a tabulation of the characteristics, enter the various
   capacity and power points given, and draw a smooth curve through them, Fig. 4.


2. Plot the viscous-liquid characteristics of the pump
   The viscous-liquid characteristics of regenerative-type pumps are obtained by test of the
   actual unit. Hence, the only source of this information is the pump manufacturer. Obtain
   these characteristics from the pump manufacturer or their test data, and plot them on Fig.
   4, as shown, for each oil or other liquid handled.


3. Evaluate the effect of viscosity on pump performance
   Study Fig. 4 to determine the effect of increased liquid viscosity on the performance of
   the pump. Thus at a given head, say 100 ft (30.5 m), the capacity of the pump decreases as
   the liquid viscosity increases. At 100-ft (30.5-m) head, this pump has a water capacity of
   43.5 gal/min (2.74 L/s), Fig. 4. The pump capacity for the various oils at 100-ft (30.5-m)
   head is 36 gal/min (2.27 L/s) for 400 SSU; 32 gal/min (2.02 L/s) for 600 SSU; 28 gal/min
   (1.77 L/s) for 900 SSU; and 26 gal/min (1.64 L/s) for 1000 SSU, respectively. There is a
   similar reduction in capacity of the pump at the other heads plotted in Fig. 4. Thus, as a
   general rule, the capacity of a regenerative pump decreases with an increase in liquid vis-
   cosity at constant head. Or conversely, at constant capacity, the head developed decreases
   as the liquid viscosity increases.

Hood, ft

Wotir

Wotir

H9od-copocit*

Capacity,

L/s

Capacity,

gal/min