January 27, 2016
Soft Foot Concerns In The Stationary Machine?
By Mac MacCormack
VibrAlign has numerous blogs on soft foot and the frustration that goes along with not eliminating it. Repeatability (or the lack of) can be a major issue. Vibration analysis will pick it up if it is severe enough.
When performing a precision shaft alignment most, if not all, soft foot will be eliminated in our pre-alignment steps. Those pre-alignment steps are performed on the moveable machine, not the stationary, therefore it would be unlikely that one would detect soft foot at the stationary machine when performing a precision alignment.
As you know from previous blog articles, soft foot can show up in different forms.
What if one is certain that soft foot was eliminated in the moveable machine yet there are still repeatability issues or vibration analysis keeps indicating to soft foot? Chances are the soft foot may be in the stationary piece of equipment. James Pekarek wrote a blog on 01/15/2014 titled “Don’t bet against your alignment tool” in regards to repeatability issues that turned out to be due to a broken stationary foot.
Soft foot can show up in vibration analysis.
Vibration Before Correcting Soft Foot
Vibration After Correcting Soft Foot
I recently completed a precision shaft alignment class where the class ran into a bolt bound situation which required movement of the stationary machine to get out of the being bolt bound. After successfully making the required adjustment they ran into a second issue. Every time the hold down bolts were tightened on the stationary, the alignment would move out of tolerance. Classic indication of soft foot. Long story short, the soft in the stationary was corrected and within minutes a precision alignment was completed!
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