ISO 1940 defines balance quality grades — written as a G number — that set the allowable residual imbalance for a rotating part at its working speed. A lower G number means a finer balance and less residual vibration. The grade is chosen to suit the machine type: very fine grades for precision spindles, and G6.3 as the established standard for general industrial fans and blowers.
Balancing every impeller to G6.3 keeps residual vibration low enough to protect the bearings, motor and structure while remaining practical and economical for the duty. We balance to G6.3 and supply the balance and full-load run-test report with each fan, so you can verify the rotating quality of the unit on arrival rather than taking it on trust.