Hi,

Do anyone have math to calculate residual unbalance in a rotor and co-relate the same with the balancing grade. i do have the charts related to balancing grades. thanks in advance.

Madhu

I suggest you review this thread, in particualr the 2nd item submitted by "electricpete."

http://maintenanceforums.com/eve/forums/a/tpc/f/3751089011/m/7581085031

John from PA

IRD has a paper that explains balance quality grades very well, Balance Quality Requirements of Rigid Rotors

Simply put, residual imbalance is simply the amount of imbalance that is left in the rotor after balancing. It will be expressed as "mass-distance" such as ounce-inches, gram-inches, or gram-mm. For example, if I balance a fan wheel using 400 grams, and my final calculation says I should have used 410 grams, then I have left 10 grams of imbalance in the rotor. If my balance weight is placed at a radius of 20 inches (from the shaft centerline), then the residual imbalance is 10 grams x 20 inches or 200 gram-inches. How this relates to the final balance quality depends on the weight of the rotor, and the speed at which it runs. This is explained in the paper above.

Are you using a portable instrument that is measuring mils and you are doing basically a field balance. If you are and want to translate mils to ounce-inch of unbalance I can help you in this respect. You can email me at info@diagnalysis.com and I will give you the proceedure
William