Page 158 - Know and Understand Centrifugal Pumps
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Shaft Deflection
The dual volute pump
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Some pump manufacturers use a different tactic to expand the
operating window of their products. This is why the dual volute pump
exists. The dual volute pump is designed to operate over a wide range
of flows and heads.
In the casting procedure of the dual volute pump, a second cutwater is
designed 180" opposite the first cutwater and another volute channel
added. This way, all areas exposed to velocity and pressure around the
volute casing are equal. All forces around the volute are equalized or
cancelled (Figure 9-15).
The second cutwater and volute channel create an additional
obstruction to the flow through this pump, and for that reason it robs
some energy from the fluid. This will reduce the efficiency to a small
degree, but the operational range of these pumps is quite broad as you
can see in the graph. The dual volute design casing is an optional cost
accessory with some pump companies, and offered standard with
others.
100% Radial loading IS
highest at shut - on head 1 001
0 50 100 150
Yo Design capacity
DUAL VOLUTE PUMP DESIGN
Figure 9-1 5
F- 141
