Page 25 - Know and Understand Centrifugal Pumps

Know and Understand Centrifugal Pumps

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sp.gr. = 1.25 sp.gr. = 1 .OO sp.gr. = 0.75

Figure 1-4 _- ~~~

pressure is very important with double mechanical seals, because it
governs the pressure setting of the barrier fluid.

Head versus pressure
Figures 14 and 1-5 show the relationship between head and pressure
in a centrifugal pump moving liquids with different specific gravities.
There is more on this in Chapter 7.

The above graphic shows three identical pumps, each designed to
develop 92.4 feet of head. When they pump liquids of different specific
gravities, the heads remain the same, but the pressures vary in
proportion to the specific gravity.
In the graphic below (Figure 1-5), these three pumps are developing
the same discharge pressure. In this case they develop different heads
inversely proportional to the specific gravity of the fluids.

sp.gr. = 1.25 sp.gr. = 1 .OO sp.gr. = 0.75

Figure 1-5
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