Page 215 - Centrifugal Pumps Design and Application
P. 215
High Speed Pumps 189
Figure 11-5. Inducer characteristics curves.
Commercial inducers have tended to result in performance suction spe-
cific speeds on the order of S s = 20,000 to 24,000. This level of perfor-
mance entails some compromise from the standpoint of consideration of
inducer cavitation but provides respectable inducer design, though per-
haps not ultimate design. These suction specific speeds generally
produce dramatic improvement in suction performance, frequently pro-
viding up to 80% NPSHR reduction over uninduced pumps.
Freedom from long-term cavitation erosion to the inducer itself is pro-
vided by observing experimentally established cavitation limitations in
the inducer design. The cavitation limitation is related to tip speed, fluid
specific gravity, and the inducer material as follows:
where K is an experimentally established constant which varies with the
inducer hydraulics and material of construction.
Commonly used 316 stainless steel is considered to possess "good" re-
sistance to cavitation erosion, but exploitation of materials with superior
