Page 141 - Centrifugal Pumps Design and Application

Vertical Pumps 119

Figure 9-6. Installation of 100,000 GPM wet pit pump (courtesy BW/IP interna-
tional. Inc. Pump Division, manufacturer of Byron Jackson/United™ Pumps),

locate the elbow on the discharge column below the mounting elevation.
For this type of configuration, care must be taken by the piping designer
to make sure that any horizontal expansion of the discharge pipe is con-
tained and will not force the pump column with the lineshaft out of align-
ment. Furthermore, the column must be free to elongate axially at the
discharge elbow when filled with water. This can be accomplished by lo-
cating a flexible coupling in the discharge pipe near the discharge elbow.
Wet pit pumps are usually driven by a vertical, solid shaft induction or
synchronous motor as depicted in Figure 9-7. However, horizontal driv-
ers that transmit torque through a right angle gear mounted on the dis-
charge head may also be used. For applications where a wide variation in
flow and/or head requirements exist, a variable speed driver may be
used. Eddy current clutches or variable frequency electric drives are of-
ten used, the latter being the more efficient of the two.