April 17, 2013
The Importance of Proper Alignment Technique and Being Aware of Movement
By James Pekarek
During the OJT portion of a Fixturlaser GO Basic Training class, with the Army Corp of Engineers, the class aligned two electric motors driving large winch gearboxes on a dredging barge. These winches are used to move the barge into position during dredging operations.
The class wanted to rotate both shafts to perform the alignments, so to take the alignment measurements, we momentarily disengaged the winch drum from the gearbox rotated the gearbox and motor shafts to the each measuring position and then re-engaged the drum to take the alignment measurements. We could have treated this as a non-rotating shaft alignment and broken the coupling loose to do so, however more accurate misalignment data is obtained when both shafts are rotated.
During the second winch gearbox alignment, we were struggling to keep the horizontal coupling values in tolerance. The coupling values would be near perfect during the live horizontal correction using the Verti-Zontal Compound MoveTM and then be more than 2 times out of tolerance upon the recheck. The vertical alignment remained spot on. Hmm, something must be moving?
After some analyzing and carefully watching the dual inclinometer values for the sensors, I noticed that during the “live” horizontal correction, the motor coupling and sensors were very slowly moving 5-6 degrees up and down with the movement of the barge sitting on the water in the river. The winch was coupled to some large positioning booms outside that were swaying very slightly in the passing wakes. This was happening too slowly to perceive with the eyes or even feel, but the inclinometers did in fact pick up the movement which was causing a “false” misalignment condition.
We then disengage the winch drum and held the sensors in place with a steady rest fixture while performing the live horizontal adjustment, the alignment came in perfectly and the recheck confirmed a perfect alignment both vertically and horizontally. Our customer is very happy with the Fixturlaser Go Basic and they are excited to begin aligning the other rotating machinery on their boats.
Very interesting story/situation. Awesome job catching the problem during the alignment class, and a great example of how accurate inclinometers are. This is definitely something that could have cost this customer a lot of time and money to diagnose….
Like Andrew said, this really shows the value of training…good job!
That is an excellent example of how to stay level-headed and look for the problem instead of blaming the tool.