Balance Quality of Rotating Equipment

To determine the allowable imbalance, the following information (numerical values) regarding the rotor is required: The maximum rotational speed nmax at which the rotor is used The mass m of the rotor The position of the rotor bearings The position of the balancing surface For more detailed calculations, the position of the rotor’s center of mass is required. The balance grade is determined based on the type of rotor. The lower the balance grade value, the higher the balancing accuracy. However, as noted in the JIS commentary, special attention is required for G1 and G0.4. The permissible residual unbalance ratio eper is determined based on the maximum rotational speed at which the rotor will actually be used. This can be calculated using the following formula or the diagram on the right. Balance grade = e × ω ω = 2πn/60 = n/9.55 n [min⁻¹] ω [rad/s] Balance grade = e × n 9.55 Determine the allowable residual unbalance from the allowable residual unbalance ratio and the rotor mass. Allowable residual unbalance Uper = eperm [g·mm] Distribute the allowable residual unbalance to the actual unbalanced surfaces (Note: The calculation method for distribution varies depending on the relationship between bearing position, unbalanced surface position, mass, and center of mass; refer to the JIS standard for details).