Reverse Alignment - Understanding Centerline Measurement.

Tutorialpg. 189-196Shaft alignment is a key factor in reducing vibrations and increasing reliability in rotating equipment. The most popular method of measurement is "reverse alignment." This method is often considered so complicated that many users have developed step by step worksheets, plotting boards, programmable calculators, and computer-aided laser devices that can guide the aligner through the procedure without a real understanding of the fundamentals of alignment. A need for a good understanding of the reverse method of measurement prompted this presentation. The focus herein is to show how misalignment affects the rotor's behavior. Using a back to basics graphical method, it is shown how to visualize the shaft center lines that enable the aligner to use logic for the easiest and best move. Calculation of thermal growth and how to select an allowable tolerance is also discussed. Hot alignment is presented by showing different online monitoring systems as well as how to misalign cold so that the shafts will be colinear during operation. An alignment trainer is used to demonstrate how an actual alignment is made