Page 198 - Centrifugal Pumps Design and Application

11

High Speed

Pumps

By Edward Gravelle
Sundstrand Fluid Handling Division

The trend toward higher process pressures, which has developed over
the past half century or so, has provided impetus to exploit the advan-
tages of high speed to better provide high head capability in centrifugal
pumps. High head centrifugal design may be provided by using high ro-
tating speed, by series multi-staging, or by a combination of both.
The advantages of high-speed design are several. Fewer and smaller
stages are required to meet a given head objective, and not infrequently,
single-stage designs can provide capability that would otherwise require
multi-staging. Smaller, more compact design tends toward shorter shaft
spans that can result in lowered shaft deflection and improved shaft dy-
namics. Compactness, involving fewer and smaller components, is eco-
nomical of materials, which becomes increasingly important when ex-
pensive materials are required for handling severe process fluids.
Minimal spares inventory and relatively quick and easy maintenance are
attributes of high speed, which are often very attractive to users, to
whom pump availability is central to the viability of their businesses.
Lightened pump weight can translate into smaller and less expensive
mounting foundations.
Conversely, other considerations are involved in a movement toward
higher speeds. About 95% of all pumps in industry are driven by electric
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