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6.5 Static Runout Procedure II
When dial indicators are used, the form in figure 18 should be used. The plot of this data
will be only the plot of the runout at the location of the lower dial indicators. The origin is
the position of the shaft at 0 degrees. The center of runout is again the intersection of the
lines from 0 to 180 and 90 to 270 degrees. This plot is also shown in figure 18. To
correlate the runout plot to the plumb of the center of runout, one set of plumb readings is
required at 0 degrees. In this example, the plumb data from figures 14 and 15 are used. The
position of the thrust runner with reference to the runout plot can be determined by
measuring the out of plumb from the thrust bearing to the elevation where the lower dial
indicators are located on the plumb plot. For this example, we will assume that the dial
indicators are located at the thrust bearing elevation and at the same elevation as the fourth
plumb reading elevation. These values can then be used to plot the center of the thrust
runner with respect to the 0-degree point. As with the other method of measuring static
runout, the plot is a top view of the unit. To make the center of runout plumb, it must be
moved under the center of the thrust runner. This is accomplished by plumbing the unit as
described in the next section.
will be only the plot of the runout at the location of the lower dial indicators. The origin is
the position of the shaft at 0 degrees. The center of runout is again the intersection of the
lines from 0 to 180 and 90 to 270 degrees. This plot is also shown in figure 18. To
correlate the runout plot to the plumb of the center of runout, one set of plumb readings is
required at 0 degrees. In this example, the plumb data from figures 14 and 15 are used. The
position of the thrust runner with reference to the runout plot can be determined by
measuring the out of plumb from the thrust bearing to the elevation where the lower dial
indicators are located on the plumb plot. For this example, we will assume that the dial
indicators are located at the thrust bearing elevation and at the same elevation as the fourth
plumb reading elevation. These values can then be used to plot the center of the thrust
runner with respect to the 0-degree point. As with the other method of measuring static
runout, the plot is a top view of the unit. To make the center of runout plumb, it must be
moved under the center of the thrust runner. This is accomplished by plumbing the unit as
described in the next section.
If plumb readings were obtained with the Permaplumb system, the runout diameter will be
determined with dial indicators as discussed above. The plumb data from the Permaplumb
system provides the out of plumb of the center of runout. To correlate the plumb data to
the runout data, the total out of plumb from the thrust bearing to the location of the lower
dial indicator must be calculated. This distance should have been input as part of the setup
data in the computer. If this is done, the total out of plumb for that distance will
automatically be calculated. The thrust bearing center can then be plotted on the runout
plot from the out of plumb data. Once again, the unit will be plumb once the center of
runout is directly below the center of the thrust bearing.
determined with dial indicators as discussed above. The plumb data from the Permaplumb
system provides the out of plumb of the center of runout. To correlate the plumb data to
the runout data, the total out of plumb from the thrust bearing to the location of the lower
dial indicator must be calculated. This distance should have been input as part of the setup
data in the computer. If this is done, the total out of plumb for that distance will
automatically be calculated. The thrust bearing center can then be plotted on the runout
plot from the out of plumb data. Once again, the unit will be plumb once the center of
runout is directly below the center of the thrust bearing.
6.6 Correcting Excessive Static Runout
In the event the measured static runout is greater than the recommended maximum
allowable value, some correction will be required. Before any corrective action can be
taken, the source of the excessive runout needs to be determined. The most likely cause is
non-perpendicularity between the thrust runner and the shaft, but a dogleg or a bend in the
shaft can also cause excessive runout. If the plumb readings and plots indicate that the
shaft is straight, the problem lies in the thrust runner not being perpendicular to the shaft.
This may be due to inaccuracies in machining or to an improper installation procedure. The
thrust block is usually a shrink fit onto the generator shaft. Normal procedures call for the
weight of the unit to be put on the thrust block while it is still warm. If the block was
allowed to cool before any weight was applied, it may cock slightly when weight is applied,
causing the runner not to be perpendicular to the shaft. To minimize machining
inaccuracies, the thrust block and keys should be match marked to the shaft so that they can
be installed in the same orientation as they were in before they were removed. If the thrust
block was installed properly and there is still a problem, shimming may be required to
reduce the runout magnitude. Depending of the thrust block design, shimming the thrust
allowable value, some correction will be required. Before any corrective action can be
taken, the source of the excessive runout needs to be determined. The most likely cause is
non-perpendicularity between the thrust runner and the shaft, but a dogleg or a bend in the
shaft can also cause excessive runout. If the plumb readings and plots indicate that the
shaft is straight, the problem lies in the thrust runner not being perpendicular to the shaft.
This may be due to inaccuracies in machining or to an improper installation procedure. The
thrust block is usually a shrink fit onto the generator shaft. Normal procedures call for the
weight of the unit to be put on the thrust block while it is still warm. If the block was
allowed to cool before any weight was applied, it may cock slightly when weight is applied,
causing the runner not to be perpendicular to the shaft. To minimize machining
inaccuracies, the thrust block and keys should be match marked to the shaft so that they can
be installed in the same orientation as they were in before they were removed. If the thrust
block was installed properly and there is still a problem, shimming may be required to
reduce the runout magnitude. Depending of the thrust block design, shimming the thrust