TABLE OF CONTENTS The technology of alignment presented thus far is fundamental theory. The methods will work to move the shafts to a more coaxial orientation and less vibration in most, but not all, situations. The world is less than ideal, and physical systems are bound by complicating factors that give the appearance that the alignment methods are not working. The symptoms of complications are usually one of the following:
Vibration is still high after precision alignment.
The alignment method is taking longer than expected with more moves, possibly undershoots or overshoots. The machine does not respond normally.
The reason for this behavior may not be obvious, but is usually caused by one of these factors:
Nonrepeatable measurements
Poor foundations
Bent shafts
Casing distortion
Bar sag
Mechanical changes
Thermal growth
These factors are the subject of this chapter. They are fundamental to the practice of alignment. They are based on science, not magic, and need to be mastered to achieve competency in the practice.
When the results of alignment efforts turn out less than satisfactory, knowledge is the aligner's best asset. Insufficient knowledge of these can make the task a frustrating experience. Good knowledge of these factors, and how to handle them, defines the difference between an apprentice and a master mechanic.
All of our knowledge about the orientation of the shafts is based on measurements. These measurements must be repeatable, not necessarily accurate. The test for repeatability is a duplication of the measurement display when returning to the same...
