Allowable Unbalance Calculator - VIBSYS TECHNICAL SERVICES

According to ISO 1940, the success of dynamic balancing can be verified either by assessing the vibration levels against ISO standards or by calculating the allowable residual unbalance values. The calculation of allowable unbalance is particularly useful when balancing is performed at lower speeds, as it provides a reliable benchmark for determining whether the rotor meets the required quality grade.

After balancing, the residual unbalance (the unbalance left in the rotor) must be less than the allowable unbalance level defined by ISO 1940 standard.

✅ If the residual unbalance is below the allowable limit, the balancing activity is considered successful.

❌ If the residual unbalance is above the allowable limit, the balancing activity is deemed unsuccessful, and corrective measures must be repeated.

The allowable unbalance (gr-mm) calculated above must be divided by the radius at which the balancing mass is applied in order to determine the allowable unbalance mass (g) at that location.

If the residual unbalance mass remaining in the rotor is less than this allowable mass, the balancing activity is considered successful. Conversely, if the residual unbalance exceeds the allowable mass, the balancing is deemed unsuccessful and further correction is required.

Note for selecting Balancing Grades as per ISO 1940:

G 6.3 – Small electric motors, Fans, Pumps, Water turbines, Paper machines, Centrifuges, etc

G 2.5 – Large electric motors, Gas & Steam Turbines, Compressors, etc

G 1 – Grinding machine drives