April 21, 2020
Thinking Outside the Alignment Box on Flexible Bases
By Tom Shelton
Here is another example of the complexity of completing a precision shaft alignment on a flexible base. Some industries use pump skids that are moved to different areas of a plant for various reasons. Whether they exist to save money, allow for quick removal or process changes, the flexibility of these types of bases make maintaining a precision shaft alignment very difficult. To keep them in a precision aligned state often takes thinking as flexible as the bases!
This rotary lobe pump is driven by a motor and a gearbox. The motor to gearbox is not align-able as it is a direct connection with a C-Face mount. This motor/gearbox assembly has 8 feet which makes it difficult to move. Notice that the base also has 6 feet. The pump has 4 feet.
The first thing that had to be done is to stabilize the base. To do this we used a torque wrench to adjust the base feet until we had even pressure on all 6 feet. Essentially, taking the soft foot out to limit the inconsistent flexing of the base. It will be difficult to do without a torque wrench.
We then moved up to the machines mounted to the base. Knowing that moving the drive unit would be more problematic, we centered the motor/gearbox unit over the hold down bolt holes, verified that we were higher than the pump, corrected any soft foot then tightened the hold down bolts of all 8 feet. This is now the “Stationary” machine. We then completed the alignment with the pump as the “Movable” machine, first by performing the Pre-Alignment Steps Pre-alignment – VibrAlign then the precision shaft alignment as outlined in our VibrAlign Training – VibrAlign.
After the alignment was completed, we decided to move the pump to a new location and see if moving with a forklift or resting on a new surface would affect the alignment… It did. We then simply used the torque wrench and balanced the pressure on the base feet and the alignment was back.
To read another example of how we conquered a flexible base alignment click this link;