What can cause vibrations in a turbine?

The occurrence of vibrations in a turbine can be attributed to various factors, and one significant cause is an imbalanced rotor. When a rotor is not evenly balanced, it produces centrifugal forces that create vibrations during operation. An imbalanced rotor may arise from uneven wear, deposits, or manufacturing defects, which can lead to increased wear and potential damage to the turbine components.

While the improper air gap in the generator (the choice provided) can lead to losses in efficiency and heat buildup, it is not a direct cause of vibrations within the turbine itself. High steam pressure can impact turbine performance, but it generally does not result in the mechanical vibrations associated with an imbalanced rotor. Excess lubrication, on the other hand, is typically not a cause of vibrations; rather, it can help in reducing friction and improving the operation of moving parts.

Therefore, an imbalanced rotor stands out as the principal factor leading to vibrational issues in the turbine, making it the most relevant answer to the question about causes of turbine vibrations.