After a shaft alignment check, if it’s out of tolerance, some maintenance personnel will skip the pre-alignment checks and proceed directly to correcting the vertical and horizontal misalignment. Frustration begins to set in as the alignment results go back and forth and seem inconsistent. The laser shaft alignment instrument says to add 20 mils to the front feet and 50 mils to the rear feet. So they do. The hold down bolts get tightened. The new alignment results are again confusing, as now they show to remove shims and the frustration level gets higher!
Sound familiar? What should you do?
Stop, take a breath, back-up and take a look at the big picture. First and foremost, when reusing the existing shims you need to evaluate those shims and make a note of the total amount of shims under each foot of the movable machine.
We advise our clients to clean under the motor feet and consolidate shim piles with no more than 5 shims under a given foot. While that may seem like a waste of time, it will actually speed up the alignment process. Knowledgeable aligners who do this regularly and mic each shim pile, consolidate and replace it with clean, new shims. And that is a good thing! But that’s only half of the picture.
We think it is also important to know and document the total shim count under each foot. This is the shim count we found during a recent training session under the feet of a 25 HP motor. Can you imagine the problems that would occur if the shims were replaced individually without comparing and seeing the big picture?
What would you do in this situation?
Check back for part 2 of the story.
3 Comments
Just by looking at the shims you are going to build in a angular soft foot. should only be .007″ from front foot to back foot at a 10″ span between feet with a 1800 rpm motor. Also looks like soft foot was over corrected and shims were added to re correct the problem. I would suggest starting over. If soft foot is that large have motor feet machined flat.
[…] my previous blog entry “Why do people struggle with alignment? Part 1”, we discussed the importance of not only micing, cleaning, and consolidating shims but also noting […]
I would agree that there is a softfoot problem. However, the problem could be with the base, the motor or a combination of both. I would start over focusing on all the preliminary aspects: base, shaft runout, pipe strain, check the motor feet, mechanical looseness, shims, housekeeping, etc. Then I would check softfoot.