Page 229 - Centrifugal Pumps 2E

Double-Case Pumps 207

jected to external differential pressure, so any bolting required to hold it
together is minimal. The outer barrel is designed as an unfired pressure
vessel, and can be constructed to the requirements of well established in-
dustry codes.

Volute Casing with Opposed Impellers

Figure 12-1 illustrates the volute-type opposed-impeller configuration,
The inner case assembly is horizontally split and consists of two identical
halves, cast from the same pattern. The double-volute construction pro-
vides radial hydraulic balance. The opposed impeller arrangement mini-
mizes resultant axial thrust, providing inherent axial thrust balance,

Figure 12-1. Volute-type opposed-impeller double-case pump (courtesy BW/IP
International, Inc. Pump Division, manufacturer of Byron Jackson/United™
Pumps).