Civil Engineering Reference
In-Depth Information
Pumping Unit
Water Level
EL 13.75
Can
Flow
4 fps
Flow Turning
Valves
Note: Example shown is for 15,000 gpm
Max Velocity 5 fps
Grating
2"
ELO
Fig. 29-17.
Can pump vertical turbine pump application
Unbalanced loads to the pump impeller
•
Pump bearing failure
•
Pump seal failure
•
Reduced pump efficiency
•
Using a long-radius reducing elbow in place of the standard-radius elbow eliminated
the column separation and reduced the velocity distribution to acceptable limits. A
reducing elbow of two standard pipe diameters, 24 in. to 18 in. (600 mm to 450 mm),
was required to maintain the pipeline velocity distribution within reasonable limits.
Sump and suction piping design is an art as well as science. Initial design is based
on scientific principles, but dynamics within sumps require models to completely refine
the design. Hydraulic model testing should be used in large pumping applications.
CENTRIFUGAL PUMPS
Figures 29-18 to 29-22 show a variety of centrifugal pumps.
The nonclog centrifugal pump is often used to pump liquids carrying low concen-
trations of solids, such as alum or iron salt sludge. The ''nonclog'' impeller is designed
with clearances to pass solids. Heavy sludge, such as lime-softening sludge, unless
mixed to keep in suspension, may concentrate too much for reliable application of
centrifugal pumps.
The prudent designer arranges centrifugal pumps so the impeller is always below
the suction static water level. In circumstances where a submerged impeller is not
