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the other(s) and to the side and back walls of the sump. These distances
are also related to the entrance velocity of the pump which in turn can
be a function of the suction bell diameter. The clearance of the bottom
of the pump to the sump floor is generally considered to be about half
of the suction bell diameter of the pump. It should be noted that bell
diameters for the same size and type of pump may vary from one
manufacturer to another.
It should also be noted that different arrangements of pumps and
accompanying baffles are used in sump designs. Many installations are
now using dividing walls between each pump to contribute to the
smooth flow of liquid to the suction bell of each pump, as this is
necessary for optimum operation. It is particularly important to avoid
any cascading effect from incoming liquids that might create air
entrainment or vortexing that will detrimentally affect the pump
performance.

9.2.6 Vertical pump design considerations
Owing to the wide diversity of applications, there are numerous design
options available on a Vertical Turbine Pump. While this provides a
high degree of flexibility in the selection process it should also raise a
warning flag to those who arc constrained by budgetary limitations.
Under these conditions it is particularly important to ensure that the
pump is accurately specified to reflect the need of the application.
One of the most vital considerations must be the assurance and
reliability of part straightness, concentricity and parallelism throughout
the life of the pump. This particular problem stems from the fact that
the shafting must be concentric with the column assembly and the bowl
assembly, and that these two assemblies must also be fully parallel
with each other and with their own individual parts. Although that
involves a lot of accuracy needed during both installation and
maintenance of a large pump, it will be well rewarded with high
reliability and long life.

9.3 Magnetic drive pumps

Magnetic Drive Pumps were originally designed to pump toxic and
other dangerous fluids without the use of mechanically sealed pumping
units. The pumpagc is retained inside the pump casing and a
containment shell, while the impeller shaft is supported on sleeve
bearings which are lubricated by that pumpage. The impeller shaft is
driven by a magnetic field passing through the containment shell from
the driver shaft.

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