Main hazards
Causes damage to the thrust bearing of the steam turbine, and in severe cases causes wear of the static part of the steam turbine.
Main phenomenon
1. The axial displacement indication increases, a sound and light alarm sound, and the expansion difference changes accordingly.
2. The metal temperature and return oil temperature of the thrust bearing increase.
3. The vibration of the unit increases and is accompanied by abnormal noise.
main reason
1. The main steam parameters, vacuum, and unit load fluctuate significantly, causing the axial thrust to increase.
2. Turbine water shock.
3. The thrust pads are worn, the lubricating oil pressure is too low or the oil temperature is too high, causing the oil film to be destroyed.
4. The through-flow part is scaled, the blades are broken, or steam leakage is serious, resulting in an increase in axial thrust.
5. The balance drum and steam sealing disc are worn.
6. The extraction operation mode has changed.
7. The generator rotor moves in series.
8. Cycle down.
Key points to deal with
1. When it is found that the axial displacement increases, the changes in load, steam parameters, shaft seal steam temperature, vacuum, lubricating oil temperature, thrust pad temperature, differential expansion, etc. should be checked, and adjustments should be made, and the thermal engineering calibration should be notified if necessary.
2. When the steam temperature and steam pressure decrease, notify the boiler to increase the steam inlet parameters and appropriately reduce the load to reduce the axial displacement.
3. When the axial displacement rises to the alarm value and the report value is long, reduce the load or appropriately adjust the extraction operation mode to bring it down to normal.
4. When the axial displacement increases and is accompanied by abnormal noises, the unit vibrates violently and the vacuum should be destroyed for emergency shutdown.
5. Water impact occurs in the steam turbine, and the vacuum should be destroyed for emergency shutdown.
6. If the axial displacement increases due to severe blade fouling, the report value should be reduced appropriately to restore the axial displacement to normal.
7. When the axial displacement reaches the threshold, the unit should automatically trip, otherwise it should shut down due to emergency failure.
8. When the axial displacement increases, the temperature of the thrust tiles rises abnormally. When the temperature of any tile rises to 90°C, reduce the load; if it rises to 107°C, the vacuum should be destroyed and the emergency shutdown should be performed.
Precautions
1. During the process of lifting and lowering the load of the unit, the monitoring of vibration and other parameters should be strengthened to ensure that the steam parameters match the load and cylinder temperature, and prevent the load steam parameters from changing significantly.
2. Guarantees the quality of soda drinks.
3. Strengthen monitoring of the operation of high/low heaters and deaerators to ensure normal water levels.
(Source: Thermal Power Plant Technology Alliance)