So many people have no idea what the difference is between Balancing and Vibration Analysis.  Potential customers will call and ask me to come over and "balance" their blower, or fan, or pump/motor unit.  I would like to think they really know the difference between the two, but they just don't understand the meaning of the words.  So, here is a little primer.

'Balancing' is the act of correcting for imbalance in a rotating assembly.  To balance a rotor you have to add or remove counter weights to offset for the imbalance that is causing excessive vibration.   To do this, you collect vibration data from different points of the rotating assembly, and "analyze" the data to identify the problem, and prepare a solution. So you use Vibration Analysis as a tool to correct for imbalance. 

When new equipment is manufactured, the rotating assembly, whether it be the rotor of the motor, or the centrifugal blower, or the pump, it is "balanced" at the factory to insure the overall vibration is well below a specification.  There are industry standards for overall vibration amplitudes, as well as "balance specs" for individual components of the rotor.  All manufacturers have their own rigorous testing to be sure their equipment operates smoothly with the least amount of vibration and imbalance. 

After the equipment has been in operation for a few years, components wear, or loosen up, or the equipment mounting loosens, and the overall vibration increases to an unacceptable level.  There are so many causes of increased vibration, with imbalance being just one of them. A vibration analyst collects the vibration data to try to determine the cause of the vibration.  He is only as good as his experience with the type of equipment, and his degree of training.  I have found loose motor hold down bolts, which when tightened properly, eliminated all of the increased vibration.

Analyzing the vibration data can identify specific problems with the rotor: bearing wear,  shaft misalignment, machine looseness, etc....  I have suspected possible imbalance in a rotating assembly and found half of the coupling was missing! There was imbalance until I put the other half of the coupling element back on!  High vibrations gone!

Vibration Analysis is one of the best tools you can utilize in your Preventative Maintenance Program.    Invest in PM, it will save you money!