Page 88 - Centrifugal Pumps Design and Application

70 Centrifugal Pumps: Design and Application

Specific Crossover Designs

A successful multi-stage pump development should produce a product
that has excellent hydraulic performance, low manufacturing cost, and
requires a minimum initial capital investment. These three items become
the basic design requirements during the layout of horizontally split
multi-stage pumps. Hydraulically, the pump design should achieve the
best possible efficiency, as well as the highest head per stage, thereby
minimizing the number of stages required. The best available technology
should therefore be utilized to produce the most efficient volutes and im-
pellers. Although crossover design has only a secondary effect on pump
efficiency, it too should use every available "trick" to achieve the best
possible results.
Figure 6-5 shows short and long configurations of the two basic types
of crossovers normally used on multi-stage pumps. Both have been tested
by the West Coast pump companies. Results of these tests indicate that
the radial diffusion type is approximately one point more efficient than
the diagonal diffusion type.

Figure 6-4. Results of crossover performance study.