Page 110 - Rotating Machinery Pratical Solutions to Unbalance and Misalignment

Rotating Machinery: Practical Solutions

reaction to the unbalance. The real source of these characteristics
is thus the unbalance. The amplitude of both the radial and axial
vibrations will be reduced when the rotor is balanced.
Figure 7-2 depicts misalignment of a sleeve-type bearing to
its shaft.

VIBRATION

Figure 7-2. Sleeve Bearing with Misalignment

TYPES OF MISALIGNMENT

Misalignment in couplings can manifest itself in three basic
ways. The first is parallel offset as shown in Figure 7-3. In this
type of misalignment, the two shafts can be offset vertically, hori-
zontally, or a combination of both.
This type of misalignment is often found in small equipment
that has a common base plate, and the equipment is doweled to
the base plate. Many manufacturers dowel the equipment in this
fashion, but it is always wise to check for proper alignment. This
often requires discarding the dowels.
The second type is angular misalignment, and is depicted in
Figure 7-4. In this type of alignment, the angularity again can be
in the vertical plane, the horizontal plane, or both. Misalignment
will almost always be in both the vertical and the horizontal
planes.
In most cases, misalignment in couplings will not occur as
either a pure parallel offset or as a pure angular misalignment, but
rather as a combination of both. This is the third type of misalign-
ment and is shown in Figure 7-5.