Page 120 - Rotating Machinery Pratical Solutions to Unbalance and Misalignment

Rotating Machinery: Practical Solutions

ment should be suspected.
Phase analysis is useful in the final determination of the exact
cause of the high axial vibration. If phase readings taken on both
outboard bearings of a machine indicate that the bearing housings
are vibrating in phase with one another; and the same is true for
the second machine; and a notable phase shift is seen when taking
readings across the coupling, the source of the axial vibration is
somewhere in between. The coupling or misalignment is obvi-
ously suspect. If a phase shift is noted between the two bearings
of the same machine, a bent shaft should be suspect.
In following chapters, several precise methods for alignment
of machine shafts are presented. In addition, several supplemen-
tary considerations for alignment are discussed. These include
alignment of equipment trains, alignment of equipment with
drive shafts and alignment of U-joint types of couplings. Thermal
growth considerations are also presented.