A lift check isn’t always done when performing a precision shaft alignment, nonetheless excessive lift can be the cause of alignment frustration.
Here is a recent example from a very experienced aligner. This particular alignment was on a 150 HP motor driving an extruder through a gearbox. The horizontal alignment came in as expected but the vertical was giving him fits. He had taken care of the usual suspects such as soft foot but still wasn’t getting the expected results. After a few attempts he decided to check the lift using his ACOEM RT300 with the runout probe. Here are the documented results:
The motor shaft only lifted 1.5 mils but the gearbox lifted 22.6 mils. While gearboxes can have a slight amount of lift inherent in the system, due to gear loading, this amount seems excessive, and a bad bearing is suspected.
The issue is under current investigation, however it isn’t surprising the alignment was problematic.