ABSTRACT
This chapter presents three boiler feed pump (BFP) cases that demonstrates the considerable challenges in developing good predictive rotor vibration models for multistage centrifugal pumps. These challenges arise from two sources. The first is the multiplicity of liquid-filled annular rotor-stator small-clearance radial gaps that dominate the vibration characteristics of such machines, combined with the dimensional variability of these small radial gaps from inside diameter (ID) and outside diameter (OD) manufacturing tolerances and in-service wear. Second, the potentially large and uncertain hydraulic radial static impeller forces, which vary with a pump's operating speed and points over its head–capacity curve, introduce considerable uncertainty in radial bearing static loads. Since a journal bearing's rotor dynamic characteristics are strong functions of its static load, the inherent uncertainty of impeller static radial forces adds to the uncertainty for rotor vibration modeling and problem diagnoses.
