Page 172 - Rotating Machinery Pratical Solutions to Unbalance and Misalignment

Rotating Machinery: Practical Solutions

VERTICAL ALIGNMENT

As with any precision alignment method, the vertical align-
ment should be corrected first. Again, use caution to rotate the
equipment in its normal operation direction, and never back up to
obtain a reading.
Starting with one of the dial indicators at the 12 o’clock po-
sition, and set to its plus (+) bar sag, rotate the machine in its
normal direction of operation to the 6 o’clock position. Be care-
ful to observe the movement of the indicator as it passes
through the 180 degrees of rotation, noting its direction of
travel. The indicator is now read and recorded. Note that the
other indicator is now in the 12 o’clock position and should be
set to its plus (+) bar sag.
Rotate the machine 180 degrees. Bring the first indicator to
the 12 o’clock position where it should return to its plus (+) bar
sag reading. Bring the other to the 6 o’clock position where the
second reading is taken and recorded. Rotate the machine 180
degrees again, and assure the second indicator returns to its
plus (+) bar sag reading at 12 o’clock.
The data can now be transferred to the graph, used in the
calculator method, or input to a computer program.

GRAPHICAL SOLUTION

The graphical method employs the same principles used in
the rim and face method of Chapter 8. A suitable scale for the
vertical and horizontal scales must be determined. Use the same
principles used in the other method, usually 1 mil per inch in
the vertical, and a scale such that the entire machine will fit the
graph.
Remember, all graphical points are measured from the stem
of the stationary machine dial indicator. Starting at the left of
the graph, draw the first vertical line and properly label it the
outboard foot of the stationary machine. Use the scale factor