Which peaks in the spectrum are associated with unbalance in a machine with a supported rotor?

The peaks in the spectrum that are associated with unbalance in a machine with a supported rotor primarily appear at the fundamental rotating frequency, which is referred to as 1X. This indicates that unbalance causes the rotor to vibrate at a frequency that corresponds directly to its rotational speed, generating vibration signals that are seen in both the vertical and horizontal directions.

Unbalance occurs when the mass distribution of the rotor is not uniform, leading to a centrifugal force that causes vibrations as the rotor spins. Therefore, monitoring both vertical and horizontal directions allows for a comprehensive understanding of the unbalance condition in the rotor.

While other frequencies like 2X or 3X might appear in the spectrum under different conditions (such as misalignment or resonance), they are not direct indicators of unbalance for a supported rotor. The 1X peak specifically signifies the fundamental frequency of vibration related to the rotor’s unbalance, making it the most relevant choice in this context.