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There are many factors that affect the stable operation of turbines, and any malfunction that occurs during the operation of a power plant’s turbines will directly impact the proper functioning of the power generation system. Vibration of the turbine unit is a very important parameter that must be monitored during its operation, as when the vibration exceeds the specified limits, it can cause damage to the equipment and even lead to serious consequences, such as damage to the rotating components. When the vibration of the unit is excessive, it increases the stress on various components such as blades, shrouds, and impellers, resulting in high alternating stresses that cause fatigue and damage ； It causes wear to the moving and stationary parts of the unit ； Loosen the various connecting parts ； It directly causes operational accidents. When the unit vibration is excessive and occurs on the high-pressure cylinder side, it may lead to premature activation of the safety device and result in a shutdown accident. Common types of vibration faults in steam turbines: 1. Axial vibration of bearings. The reasons for excessive axial vibration of bearings include the following: When a bent rotor rotates, the shaft journals deviate; the center of force exerted by the oil film within the bearing bushes changes periodically along the axial direction as the speed increases, which in turn causes axial vibration of the bearing housing. The center of force on the bearing bush does not coincide with the geometric center of the bearing housing. The bearing housing is not stable. As a bent rotor rotates, it attempts to cause the shaft bearings and bearing housings to deflect accordingly, but the bearings are unable to follow the deflection of the shaft journal, resulting in axial vibrations. The amplitude of the axial vibration is proportional to the degree of rotor deflection, while the phase of the vibration in each bearing depends on the shape of the rotor’s deflection elastic curve. Near the first-order critical speed, the axial vibration phases of the two bearings of the rotor are opposite. Near the second-order critical speed, the axial vibration phases of the two bearings of the rotor are the same. 2. Steam flow excitation: Under normal circumstances, the high and medium pressure rotors in a steam turbine unit are the main components subject to steam flow excitation. The reason is that the steam in the flow within the turbine expands to a certain extent; this, on one hand, generates tangential force torques on the high- and medium-pressure rotors, and on the other hand, it creates an axial force from the high-pressure side to the low-pressure side. Under the action of these two forces, the blades of the high- and medium-pressure rotors, subjected to the impact of uneven steam flows, can cause steam flow-induced vibration in the turbine rotor. 3. Thermal bending of the rotor: The turbine rotor refers to the rotating part in a turbine unit; it plays a key role in the conversion of energy within the turbine. The occurrence of thermal bending faults in the rotor is related to the operating temperature of the rotor itself as well as the set values for steam parameters. Currently, thermal bending failures of the rotor mostly occur during the cold-start and steady-load operation phase of steam turbine units. This is because under such operating conditions, the rotor’s temperature is relatively high; moreover, the blades, impeller, and main shaft are subjected to significant centrifugal stresses due to high-speed rotation, which makes them prone to bending deformation. If no measures are taken after a thermal bending failure occurs, it can lead to other faults such as frictional vibration, thereby affecting the safe operation of the power plant’s generators. 4. Frictional vibration: Under long-term operation, the rotating parts of a turbine, such as blade assemblies and the main shaft of the impeller, can develop thermal bending defects due to external forces and high temperatures. This disrupts the original stable state of these rotating parts, ultimately leading to frictional vibration problems. Under such conditions, the turbine vibration signal remains at the power frequency, but due to the effects of the rotor and other factors, frequency splitting, frequency multiplication, and high-frequency components often occur; sometimes, abnormal phenomena such as waveform truncation also take place. Furthermore, when a frictional vibration fault occurs in the turbine rotor, its vibration frequency and amplitude exhibit fluctuating characteristics; if such a fault persists for an extended period, eddy current phenomena will arise. Methods for troubleshooting turbine vibration faults 1. Analysis of the logic for activating vibration protection mechanisms in bearing covers. Generally, turbine units are equipped with sensors to detect vibrations in the bearing covers; these signals are processed by the TSI monitoring cabinet, and protection actions are taken based on an \"or\" logic – as long as one of the signals exceeds its specified limit, the machine will stop operating. As a result, it is extremely easy during operation for an accident to occur in which the unit shuts down due to a false trigger of a single signal, causing significant losses to the plant’s safety and economy. To prevent such accidents, the original logical relationship needs to be improved in order to enhance the safety and reliability of the vibration protection system for the unit cover. 2. Protection circuit verification analysis: After verifying the probe, care should be taken to ensure it is installed firmly when reinstalling it; the wiring terminals should be wrapped tightly with tape to provide insulation and prevent short circuits due to sticking of the contacts ； Insulation tests must also be conducted on the signal cables to ensure the accuracy of signal transmission, and the wiring inside the TSI cabinet should be organized properly. 3. Analysis of measures to address oil film oscillation: From the analysis of the principles underlying oil film oscillation outlined above, it is clear that improving the operational stability and safety of bearings and rotors is key to troubleshooting such issues. To achieve this, it is necessary to reduce the friction between them, which can be accomplished by using lubricating oils with appropriate pressure and humidity levels. Additionally, it is important to lower the viscosity of the lubricant to prevent excessive load on the oil film. During fault handling, it is essential to avoid having too high a viscosity for the lubricating oil, as this can affect the uniformity of oil distribution and lead to increased friction between components. Furthermore, the oil film oscillation fault can also be resolved by reducing the clearance at the top of the bearing shell, increasing the width of the bearing alloy in the upper bearing shell, and decreasing the contact angle between the shaft journal and the bearing shell. 4. Analysis of measures for troubleshooting aerodynamic excitation. By analyzing the mechanism behind aerodynamic excitation faults, it can be seen that in addressing such faults, it is first necessary to examine and analyze the stable equilibrium state of the turbine rotor, to determine whether the rotor’s center of mass is in the same position as its center of rotation. Furthermore, plant technicians should keep detailed records of the vibration data of the turbine unit’s rotor during regular inspections, and integrate this data with the vibration data obtained when the unit is operating at full load. By creating vibration curves for the rotor, they can assess the operating condition of the rotor through the observation and analysis of these curves. 5. Measures for troubleshooting thermal bending faults of the rotor: Since the working area of the turbine rotor is in the steam zone, thermal bending faults occur quite frequently. Therefore, during the design process, designers should use materials with strong corrosion resistance and high-temperature tolerance as materials for manufacturing the turbine rotor. Furthermore, if the turbine rotor suffers from thermal bending failure, technicians should immediately remove the faulty rotor and replace it in order to completely resolve the vibration issues of the unit. 6. Analysis of troubleshooting measures for frictional vibration faults. Generally, the operating environment of a turbine rotor is quite complex; during operation, it is subject not only to the forces resulting from high-speed rotation and airflow impacts, but also to high temperatures, humidity, and high pressures, all of which can cause damage to the rotor and affect the safe and stable operation of the unit. Therefore, thermal power plants should pay close attention to the regular maintenance and inspection of the rotors. Once a fault is detected during these inspections, maintenance technicians must take immediate action to address it, carrying out necessary repairs on the components that cause frictional vibrations. If the repair cost for a particular machine component is too high, it should be replaced in order to eliminate the adverse effects of such vibrations on the operation of the turbine. In summary, as an important component of the power generation system in thermal power plants, the steam turbine plays a crucial role in ensuring the safe and stable operation of the plant. However, the operational stability of turbines is affected by various factors; in particular, vibration faults can severely impact the normal operation of the generator set. Therefore, power plants should pay close attention to the identification of such vibration faults, conduct a detailed analysis of common ones, and develop appropriate solutions to ensure the stable and safe operation of the plant’s power generation system.