Page 88 - Rotating Machinery Pratical Solutions to Unbalance and Misalignment

Rotating Machinery: Practical Solutions

of the machine. The machine is shutdown and a trial weight is
added to the near end. Record the weight and the angle from the
reference mark to the location of the trial weight.
Re-start the machine and measure and record the new ampli-
tude and phase location for the near and far ends. Stop the ma-
chine and remove the trial weight. Place a trial weight at the far
end, recording the weight and location. The location must be ref-
erenced to the near end and recorded as degrees clockwise from
the reference point.
Re-start the machine and again measure and record the near-
and far-end amplitudes and phase angles.
The remainder of the process of determining the amount and
location of the correction weights is best explained through an
example. Like the single plane method, the recorded data will be
transferred to polar graph paper and additional information mea-
sured and calculated.

Example 5-4
A machine had the following data recorded: What are the
recommended corrections?

Original readings: (N0) Near end: 7.1 mils @ 60 degrees.
(F0) Far end: 5.4 mils @ 215 degrees.

First trial run: (N1) Near end: 4.9 mils @ 120 degrees.
(F1) Far end: 3.7 mils @ 230 degrees.
(T1) Trial weight: 8 ounces @ 270 degrees
Second trial run: (N2) Near end: 5.1 mils @ 35 degrees.
(F2) Far end: 8.6 mils @ 160 degrees.
(T2) Trial weight: 10 ounces @ 180 degrees
What are the recommended corrections?

For this example, the following conventions will be used.

1. The convention N0 > N1 will represent a vector whose length
is from N0 to N1 and the > sign denotes the direction in