Page 145 - Rotating Machinery Pratical Solutions to Unbalance and Misalignment

Advanced Machine Alignment

ment dial indicators positioned in the 3 o’clock position. The
face indicator should go to zero, while the rim indicator
should go to 1/2 its reading.

3. Small machines can be moved using bar type glue clamps. A
come-along and chain hoist can be employed for moving
some large machines. With caution, jacking bars can be used
to pry the machine into position. A small lead mall may be
used to bump a machine into its final position.

Forms for the horizontal alignment are provided in the ap-
pendix.
Regardless of the method employed to physically move the
machine, always assure the movement is measured and con-
trolled. As with the vertical alignment, several adjustments may
be required to achieve the final alignment. When the horizontal
alignment is completed, check the vertical alignment again to as-
sure it was not disturbed. Machines with uneven base plates could
cause slight changes in the vertical alignment during the horizon-
tal alignment process.
Remember, aligning a machine to within “tolerances” is not
the goal of a good maintenance person. The more accurate the
final alignment, the fewer coupling, seal and bearing failures.

THERMAL GROWTH AND HOT ALIGNMENTS

Many machines operate at either hotter or colder tempera-
tures than when they are being aligned. Some refrigeration com-
pressors operate at temperatures below freezing while some gas
compressors may reach over 300°F. Changes in temperature cause
these machines to either grow or shrink, and can distort the align-
ment. For these machines, consideration must be made for ther-
mal growth.
Although most machines do not operate at these extremes,
thermal growth should be considered for all alignment processes.
Once the fundamental understanding of how to compensate for