Page 238 - Centrifugal Pumps Design and Application

212 Centrifugal Pumps: Design and Application

Figure 12-6. Water injection pump with full cartridge puliout, featuring a
springplate on the high pressure end to preload the internal gasket that seals full
differential pressure (courtesy BW/IP International, Inc. Pump Division, manufac-
turer of Byron Jackson/United™ Pumps).

for differential thermal expansion. Finite element analysis of the spring-
plate assures that all design goals are achieved. This mechanical design,
with the proper materials of construction, is also suitable for boiler-feed
service.
The cartridge puliout design is especially advantageous when the
pumps are located in an unfavorable environment, such as an offshore oil
production platform. All critical assembly operations are performed in a
service shop where high quality mechanical work is more easily
achieved,

Auxiliary Take-off Nozzles

As shown in Figure 12-3, double-case boiler feed pumps are well
suited for incorporating auxiliary take-off nozzles that are necessary
when reheat and superheat attemperation sprays are required.

Double-Suction First-Stage Impellers

Figures 12-1 and 12-3 show double-case pumps with double-suction
first-stage impellers to reduce NPSH requirements. In some installations,
this feature eliminates the need for a separate booster pump.

Mounting of the Impellers

Impellers are assembled on the shaft with a shrink fit to prevent me-
chanical looseness under all operating conditions and are positioned axi-