Setting a machine train to have the correct shaft alignment while running is important for a machine to function properly. Typically, manufacturers will provide the expected thermal growth for their components. However, in some cases measuring the actual thermal growth in the field allows better cold alignment settings to be chosen for a given application.
The thermal growth of a machine can be measured with an optical level by measuring the difference in location of several points while it is hot (running at normal conditions) and while it is cold (at ambient temperature). The hot and cold measurements are taken by comparing the distance between several fixed reference points and points on the machine. Using this method it is possible to determine the thermal growth in both the vertical and horizontal directions. Once the alignment measurements are taken, the cold alignment settings can be chosen so that while running the machine will have the optimal alignment.