Categories: Shaft Alignment,Machinery Diagnostics,Other Topics

Don’t Forget a Lift Check!

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By on October 22, 2020

 

 

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.

 

Additional Resources:

How to perform a lift check

Fixturlaser Runout probe

Runout probe blog post

 

About the Author

Mike Keohane has been involved in machinery reliability since 1985. He started as a field service engineer for IRD Mechanalysis. Prior to that he was a wireline logger for Schlumberger Well Services. He joined VibrAlign in 1992 and supports clients in Georgia, South Carolina, Alabama and the Florida Panhandle. In addition to precision alignment, he has field experience in vibration analysis, field and shop balancing, oil analysis and ultrasonics. Mike holds a BSME from Michigan State University. Mike and his wife and two children currently live in Peachtree City, GA.

2 responses to “Don’t Forget a Lift Check!”

  1. Phil Hendrix says:

    We teach Hands On Precision Mtce I think you know. The hardest thing in the world to get mechanics and even engineers and mgrs to Do the 5 things (including lift check) before you ever mount the laser #%?!€ Saves Time, Sweat, $$$, and Heartache!!’n

  2. Michael Keohane says:

    Phil,

    Thanks for the comment! We always stress that a little work up front saves a lot of pain down the road. It still amazes me that so many people don’t do the basics until they, almost inevitably, run into problems.