Field dynamic balancing is a dynamic balancing process performed on the rotor while it is mounted in its own bearings and frame—not on a dedicated balancing machine. In other words, when the rotor’s vibration condition is unsatisfactory at the worksite or during machine testing, field dynamic balancing is carried out to improve the machine’s operational vibration performance. The objective of field dynamic balancing is to reduce mechanical vibration, dynamic shaft deflection, and bearing forces—caused by imbalance—to permissible levels; therefore, field dynamic balancing evaluation is typically based on in-situ machine vibration standards.
The primary vibration characteristics of rotor imbalance faults are: (1) the time-domain waveform of vibration approximates a sine wave; (2) the 1× rotational frequency dominates the spectrum; (3) amplitude increases with rising rotational speed; (4) phase remains stable at a fixed operating speed; (5) the shaft center trajectory forms an ellipse; and (6) forward precession observed from the shaft center trajectory is synchronous.
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