Centrifugal Pumps Design and Application 2nd ed - Val S. Lobanoff, Robert R. Ross (Butterworth-Heinemann, 1992)

208 Centrifugal Pumps: Design and Application
Diffuser Casings with Balance Drum
Diffuser-type pumps have all impellers facing in one direction, resulting
in high axial thrust forces. Figure 12-2 shows a diftuser-type pump
with a balance drum to carry the axial thrust forces. The inner case assembly
is vertically split, and the symmetry of the diffusers provides radial
hydraulic balance.
Diffuser Casings with Balance Disk
Figure 12-3 shows the diffiiser-type configuration with a balance disk
that carries the axial forces. Except for the axial balancing device, the
construction is similar to the previous diffuser-type design. Balance disk
construction is used for clean services such as boiler feed because of its
ability to completely balance axial thrust at all operating flow rates.
Figure 12-2. Diffuser-type in-line impeller, double-case pump with balance drum
(courtesy Dresser Pump Division, Dresser Industries, Inc.).
Applications
Common applications for double-case pumps are:
« Boiler feed pumps in central station and large industrial fossil-fueled
power plants.
• High pressure and/or high temperature pumps in oil refineries or
chemical plants.