February 18, 2015
Adjustable Motor Plate Alignment using the Verti-Zontal Alignment Process
By Matt Rybalt
Recently while visiting a client’s site, we were asked for alignment advice regarding an electric motor coupled to a mixer. The customer shared that the electric motor sat upon an adjustable base plate with adjustment bolts (jack bolts) in the vertical and horizontal planes.
Despite the base plate having vertical jack bolts, VibrAlign’s typical instruction in this application is to simply add/remove shims for the vertical adjustment. Shimming at the motor feet was not possible due to an obstruction blocking the right side motor feet. Challenged by this barrier, we decided the vertical jack bolts were a viable alternative for making vertical corrections.
This particular motor & mixer operate at 3560 RPM with a history of costly seal and bearing failures. To complicate matters, this production function needed to be operational in less than 90 minutes, making both precision and efficiency critical variables.
After an initial inspection, we loosened all the vertical jack bolt jam nuts, easing the tension on the base plate. This allowed us to measure each adjustment point for soft foot. Through this process we identified that the base was not flat and thus when the back left bolt was torqued it resulted in deflection (soft foot). We vertically adjusted this isolated foot which subsequently resolved the issue. After completing the remaining Pre-alignment steps, we set up the Fixturlaser EVO alignment system selected the 3600 RPM tolerance and measured the motor shaft condition.
The initial results indicated severe misalignment with the vertical angle more than 5 times tolerance, the vertical offset was almost 11 times tolerance, the horizontal angle was more than 12 times tolerance and the horizontal offset was 13 times tolerance!
We began the Verti-Zontal correction process and because of the vertical jack bolts, bypassed the shimming screen straight to the live screen. Using the EVO live screen with the sensors in the vertical plane allows you to perform vertical adjustments on this type of machine while simultaneously observing the motor shaft position.
Through this process we identified that a half turn of the vertical jack bolt was a change in position of roughly 5 mils (.005”). Staying focused, we were sure to account for the same allotted torque on both the inboard and outboard feet vertical jack bolts. We also discovered and compensated for roughly .005”- .010” of excessive gap displacement at each foot.
Next we made our horizontal adjustments utilizing the horizontal jack bolts.
Lastly, we evaluated our vertical alignment figures to assure there was no unintended movement. Once confident in the alignment condition, we torqued the jam nuts utilizing a cross-pattern tightening sequence and re-measured for final confirmation.
All in all, 3 specialists spent 50 minutes working on the machine. This is proof that with an effective precision shaft alignment tool and efficient alignment procedure, you can help correct/prevent rotating asset failure while working with (not against) production.