May 7, 2015
Clean, Clean, Clean! To Eliminate Soft Foot!
By Tom Shelton
There are many things that can affect the precision shaft alignment process, which needs to be checked and eliminated during the Pre-Alignment Steps, such as pipe strain, disintegrating bases, bearing or coupling wear, etc…. One of the main issues concerning shaft alignment of rotating equipment is the challenge of soft foot and its detrimental effect on the alignment process as well as equipment reliability.
The causes of soft foot are varied and often elusive. Eliminating soft foot is a critical step in the Pre-Alignment Process as set forth in the VibrAlign Training. Gain control of soft foot and you will eliminate one of, if not the major cause of “shaft alignment frustration!”
One major contributor to soft foot, that is often overlooked, is dirt and debris in between the base foot pads, shims, and the moveable element’s feet. We are aligning rotating machinery to tolerances measured to 1.0 mil (.001”) and/or 0.1 mil (.0001”). It doesn’t take much debris under the machinery feet to cause issues.
Yes, it takes time to clean up some of the machines in the field, but it is time well spent! The time spent cleaning the base and feet contact zones will save immeasurable time on the actual alignment process. Why? Because soft foot is a significant contributor to non-repeatability. Fixturlaser Shaft Alignment Tools are intended to align machines in one to two moves using the VibrAlign Vertizontal Process. This process is dependent on the thorough performance of the pre-alignment steps, two of which address the elimination of soft foot.
Here is a good example of cleaning the base and motor feet from a recent training class.
AFTER A THOROUGH CLEANUP
Once the cleanup and pre-alignment steps were completed, the actual precision shaft alignment was completed in one move in about 15 minutes with zero frustration!