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

476 Centrifugal Pumps: Design and Application
Figure 18-30. Vibrationai response of inboard bearing housing.
ings. The transfer function (Figure 18-31) was plotted with a fell scale
amplitude equal to 0.4 (0.05 per major division on the graph paper).
The inboard bearing of Pump A had a major response at 420 Hz with a
transfer function amplitude of 0.24. This frequency was almost coincident
with seven times running speed (418 Hz) which would amplify the
vibration levels at seven times running speed and appeared to be the primary
cause of the high vibration at seven times running speed. The
flange bolts were tightened and the frequency increased to 430 Hz which
indicated that the response near 420 Hz was primarily associated with the
bearing housing and its attachment stiffness to the case.
A similar major response near 432 Hz occurred in the vertical direction.
The transfer function amplitude was lower and the frequency was
higher than measured in the horizontal direction because the bearing was
slightly stiffer in the vertical direction compared to the horizontal direction.
When the flange bolts were tightened, the response near 432 Hz
was increased to 440 Hz.
The outboard bearing was more massive and stiffer and not as responsive
as the inboard bearing. There were no major responses in the horizontal
direction near the excitation frequencies of interest. A vertical response
was measured near 580 Hz; however, because it was above the
frequencies of interest, it should not cause an increase in vibration on the
bearing housings.