July 1, 2013
IS VIBRATION INTERFERING WITH YOUR PRECISION SHAFT ALIGNMENT?
By James Pekarek
During a recent Fixturlaser XA Pro training class, at a Texas petrochemical plant, we were performing an alignment on a 25 HP, 3600 RPM electric motor & water pump. At first the class was having a little trouble bringing the alignment into the 3600 tolerance due to two separate issues.
The first was severe vibration coming from the surrounding equipment causing our coupling and feet values to fluctuate slightly while making the live horizontal correction. This vibration was also causing inconsistent results when two sets of alignment measurements were taken.
The second issue we encountered was the motor was bolt bound by 15 mils at the rear feet when performing the horizontal move portion of the Verti-Zontal Compound MoveTM. Both issues were easily rectified with a few simple settings in the XA Pro.
To overcome the vibration we did two things. We first extended the sample time setting (outlined in red) from three seconds to eight seconds (after the running the built in repeatability test to determine the best setting). We then enabled the level two vibration screen filter (outlined in green). These two settings effectively eliminated the issues caused by the vibration.
The measurement results then repeated with in specifications and the screen filter allowed for the horizontal adjustment with steady values.
The bolt bound issue was easily solved using the Feet Lock Function of the XA Pro to find an alternate solution.
In this instance, the best solution was to lock the rear feet of the motor and the pump. By doing so we were able to move the front feet of both machines in the opposite direction the motor was bolt bound. This allowed the horizontal alignment to come in very nicely. The pump front feet only required a 7.0 mil move, which did not introduce any pipe strain.
NOTE: The piping configuration of this particular pump allowed for moving the pump without introducing pipe strain. Always determine if moving a pump will cause pipe strain before doing so.
By combining these three features of the XA Pro, we were able to perform a difficult alignment on a high-speed pump and eliminate fairly severe vibration issues as well as a bolt bound situation.