Page 73 - Know and Understand Centrifugal Pumps

Know and Understand Centrifugal Pumps

Theoretical Centrifugal
Pump H-Q Curve

- Theoretlcal PD
Pump H-Q Curve
\
Pump H-Q Curve

Flow
Pump H-Q Curve
Figure 6-6
facturing in general, we observe that there are more centrifugal pumps.
About 90% of the pumps in industry are centrifugal pumps. And the
PD pumps found in industry have much in common with their
centrifugal sisters. They are mostly rotary designed pumps, with
precision bearings and a shaft seal. Much of the theory, and system
needs, are applicable to both types of pumps.

Centrifugal volute pumps
_~_ -~ - ____~___ ~_____ ~~
This type of pump adds pressure to a liquid by manipulating its velocity
with centrifugal force, and then transforms the force into pressure
through the volute. By observing Figure 6-7, we see that the liquid
enters into the suction nozzle at Point 1 and flows toward the impeller
eye at Point 2. The blades of the impeller trap and accelerate the fluid
velocity at Point 3. As the fluid leaves the impeller, its velocity
approaches the tip speed of the impeller blades. The volute at Point 4 is
shaped like an ever increasing spiral. When the liquid moves at high
speed from the close tolerance in the blades to the open spiral volute
channel with its ever increasing area, the velocity energy of the liquid is
converted into head or pressure energy. With the fluid accumulating its
highest pressures at Points 4, the cutwater then directs the fluid to the
discharge nozzle at Point 5.