Categories: Shaft Alignment,Machinery Maintenance,Other Topics

Base Bound Machinery Corrections

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By on December 2, 2016

Most aligners are familiar with a bolt bound situation, which occurs when the motor cannot be moved enough to achieve proper horizontal alignment.  A base bound condition occurs when a motor cannot be lowered sufficiently to achieve proper vertical alignment.  Here is an example.  During a customer’s recent pump replacement, the motor was left in place, and the pump was exchanged with a similar pump.

feet-lock-1Horizontal alignment was corrected quickly, but vertical alignment could not be achieved.  Even with all of the shims removed from the motor, the motor was still too high for precision vertical alignment.

The mechanics switched the moveable and stationary detectors, to see if moving the pump slightly could correct the vertical misalignment.  Several attempts were made to get the alignment closer, but none proved effective.


The pump could not be moved by this amount without causing serious pipe strain.  The customer was perplexed by the fact that this just didn’t make sense.

If the motor needed to move down, and it could not be done, it just seemed logical that the pump needed to be moved up.  So they contacted VibrAlign, thinking that there must be something wrong with their laser.  We helped them understand that the issue wasn’t with the tool, it was related to the combination of offset AND angular misalignment, and worked out a quick solution.

feet-lock-2From the shim screen, selecting the Feet Lock™ function allows the user to determine various combinations of vertical correction possibilities.  The only requirement is that two sets of feet must remain stationary.  They can be:

  • both sets of motor feet,
  • both sets of pump feet,
  • or one set of feet from either machine.


feet-lock-3In this case, the opposite drive end (outboard) feet of both machines were left stationary.  Using Feet Lock™, it was easy to see that moving the drive end of the motor UP 28.6 mils was quite doable, and moving just the drive end of the pump UP 5.6 mils could be done without causing excessive pipe strain.



The final alignment was well within tolerance, and quick to achieve using Feet Lock™.

feet-lock-4There are many methods to correct bolt bound and base bound conditions, and most of them require heavy lifting, grinders, undercutting bolts, re-drilling holes, or even bringing in portable milling machines.  But utilizing the Fixturlaser NXA Pro, and its powerful Feet Lock™ function can often make bolt bound or base bound conditions simple to overcome.


For more information, please follow this link to see a good instructional video on offset and angularity.


About the Author

Stan Riddle joined VibrAlign in 2008. He has over 35 years experience in aligning industrial machinery. Stan received his AAS Degree in Machinist Technology from Surry Community College in Dobson, NC, and also holds a diploma in Industrial Systems Technology from Forsyth Technical Community College in Winston-Salem, NC, where he was also an instructor in the program.

Stan began his maintenance career working as a machinist and millwright for companies such as Weyerhaeuser, R.J. Reynolds, and Tyco Electronics. He also has over 25 years experience in Predictive Technologies, such as vibration analysis, thermography, oil analysis, and ultrasonic inspection. He is a certified Level III Vibration Analyst with the Vibration Institute, and is a Past Chairman and Board Member of the Piedmont Chapter.

Stan and his wife live in Yadkinville, NC.

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