When shafts are not aligned with each other in the vertical and horizontal planes, what is the most common symptom?

When shafts are not aligned properly in both the vertical and horizontal planes, the most common symptom observed is an increase in machine vibration levels. Proper alignment ensures that the forces acting on the components are evenly distributed. Misalignment creates additional stresses and dynamic forces on the shafts and connected machinery, leading to unwanted vibrations. These vibrations can result from uneven wear or operational imbalances, which can further affect the overall performance and longevity of the equipment.

In the context of machinery, excessive vibrations often indicate misalignment and can lead to premature failure of components if not addressed promptly. Monitoring vibration levels is a critical aspect of predictive maintenance.

The other symptoms listed, while they may occur due to misalignment, are not as immediately indicative as an increase in vibration levels. For instance, bearings developing rotational oil whirl can result from operational issues other than misalignment, and bearings wearing until they align themselves is more of a misconception since they shouldn't be expected to realign on their own. Changes in shaft alignment measurements can certainly occur, but they are often a consequence of the existing misalignment rather than a direct symptom. Thus, the most prominent and observable impact of misalignment is indeed the rise in vibration levels.