Instructions for Preliminary Selection of a Pump for a Given Head-Capacity-Viscosity Condition Given the desired capacity and head of the viscous liquid to be pumped and the viscosity and specific gravity at the pumping temperature, Fig. 5 can be used to find approximate equivalent capacity and head when pumping water.
Figure 5
Enter the chart (Fig. 5) at the bottom with the desired viscous capacity, (Qvis ) and proceed upward to the desired viscous head (Hvis) in feet of liquid. For multistage pumps, use head per stage. Proceed horizontally (either left or right) to the fluid viscosity, and then go upward to the correction curves. Divide the viscous capacity (Qvis) by the capacity correction factor (CQ) to get the approximate equivalent water capacity (Qw approximately).
Divide the viscous head (Hvis) by the head correction factor (CH) from the curve marked "1.0 x Q w " to get the approximate equivalent water head (H w approximately). Using this new equivalent water head-capacity point, select a pump in the usual manner.
The viscous efficiency and the viscous brake horsepower may then be calculated.
This procedure is approximate as the scales for capacity and head on the lower half of Fig. 5 are based on the water performance. However, the procedure has sufficient accuracy for most pump selection purposes. Where the corrections are appreciable, it is desirable to check the selection by the method described below.
EXAMPLE. Select a pump to deliver 750 gpm at 100 feet total head of a liquid having a viscosity of 1000 SSU and a specific gravity of 0.90 at the pumping temperature.
Enter the chart Fig. 5 with 750 gpm, go up to 100 feet head, over to 1000 SSU, and then up to the correction factors:
