Page 147 - Know and Understand Centrifugal Pumps

Know and Understand Centrifugal Pumps

Presssures are Equal.
Figure 9-3
- ~~~
With the pump running at its Best Efficiency Point, and all valves in the
system open, the factors of pressure, velocity, and area are in harmony
at all points around the volute. All radial loads are in equilibrium
(Figure 9-3)
If a discharge valve should be throttled (increasing the resistance head,
Hf), the pressure gradients around the volute would tend to equalize
toward discharge pressure. In a worst-case scenario, if a valve should
close completely, the pressures around the volute would become
discharge pressure. The pump would move to the left of its BEP on the
curve. The velocity would become zero because no fluid is moving
through the pump. The only remaining variable is the area, which is
greater through the E-F-G-H arc of the volute circle (Figure 94).

to the left of the

The Area is greater
in the E-F-G-H- arc
of the volute circle.

P=
V= Zero velocity

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