Among the listed issues, which one can be classified as mirroring imbalance?

Mirroring imbalance refers to a situation in rotating machinery where imbalances in the rotor can cause vibrations that are symmetrical about a particular axis. This can lead to issues with performance and potential damage to the machinery over time.

Each of the listed issues can contribute to or exhibit characteristics of mirroring imbalance:

• Shaft misalignment can lead to vibration patterns that are not evenly distributed, which can mimic the symptoms of mirroring imbalance.

• Thermal rotor bow occurs due to uneven heating of the rotor during operation, resulting in a deformation that also can disrupt the balance of the rotor. This causes vibrations that reflect the characteristics of mirroring imbalance.

• Dirty bearings can cause uneven contact and increase friction, leading to variable operational characteristics that can also demonstrate mirroring imbalance effects.

Consequently, all the given issues contribute to the condition that can be classified under mirroring imbalance due to their effects on rotor dynamics and system vibrations.