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Accident handling plan with large vibration of the unit 2020-04-10


1. Large vibration of the unit:

 

1. The alarm of the vibration increase screen of the unit is issued

 

2. The operating noise of the local unit increases.

 

Second, the danger of bearing bush vibration:

 

1. Dynamic and static friction. The friction between the dynamic and static parts will not only directly cause damage to the flow passage, reduce the economics of the unit's operation, but also cause the axial thrust to increase, causing the temperature of the thrust pad to increase and even causing damage to the thrust pad. Depending on where the friction occurs, steam seals, blade damage, impeller and diaphragm deformation, and large shaft bending may result.

 

2. Accelerate the wear of other parts. It mainly includes bearing bush, journal, generator rotor slip ring and exciter commutator.

 

3. Accelerate the damage of other parts. Damage to the vibrating component usually takes a long time process, but as the alternating stress of the vibrating component increases, this time process will be greatly shortened, so that a short time of large vibration will also cause fatigue damage to some components After a short period of large vibration impact, the black metal like bearing bush will cause surface fatigue cracks, resulting in spalling, flaking and chipping.

 

4. Fracture and loosening of fasteners: Excessive vibration will cause breakage of the bearing foot bolts, loosening of the foundation and the platen, and cracking of the second grouting, which will reduce the rigidity of the bearing and the vibration of the bearing. Cracks in the foundation and surrounding buildings.

 

5. Direct or indirect major equipment accidents. Excessive vibration will cause malfunction of steam turbine protection, damage to generator insulation and breakage of water-cooled generator diversion pipe. Excessive vibration will also cause damage to the shaft system and cause the machine to die.

 

III. Reasons for large bearing bush vibration:

 

1. The oil pressure of the bearing is low, and the oil temperature is too high or too low, which causes the oil film to become unstable and produce oil film oscillation.

 

2. During the startup process, the warm-up is poor, the expansion is uneven, and the center of the rotor changes.

 

3. Dynamic and static friction occurs on the steam turbine unit.

 

4. Water shock occurred in the steam turbine.

 

5. The sudden drop of vacuum causes the temperature of the exhaust cylinder to rise and causes the rotor center to change.

 

6. The turbine blade is damaged or the internal parts are damaged and fall off, causing the rotor mass to be unbalanced.

 

7. Loose bearing bush or increased clearance.

 

8. The failure of the shaft seal system of the main engine causes the shaft seal temperature to fluctuate greatly.

 

9. Loose parts of generator exciter.

 

10. The dramatic change of the ambient temperature causes the 7 # vibration to increase

 

Fourth, the unit vibration treatment:

 

1. When the vibration of the unit reaches 0.125mm during normal operation, the load should be appropriately reduced, the cause should be identified and dealt with, and the value reported should be long.

 

2. Check whether the lubricating oil pressure and oil temperature of the unit are normal. If abnormal, adjust in time.

 

3. Check the working condition of the shaft seal system. If abnormal, adjust in time.

 

4. The vibration of the unit due to other reasons should stabilize the load and the parameters of the steam inlet, and at the same time check the thermal expansion, expansion difference, axial displacement, temperature difference between the upper and lower cylinders of the cylinder and the sliding pin system without jam.

 

5. When the vibration protection action condition is reached, the protection action steam turbine should trip, otherwise, the vacuum emergency stop should be destroyed immediately.

 

6. If water shock occurs in the steam turbine, it should be handled as a water shock accident.

 

After the unit is braked, pay attention to the idle time of the unit and listen to the sound inside the unit. Check that there is no abnormality in each meter, and the indicated value of the shaft vibration decreases, and tends to be stable, eliminate the cause of the failure, and recover after finding out that there is no abnormality.

 

The crew checked whether the main engine lubricating oil pump is connected, otherwise it was started manually. Check that the generator is disconnected and the factory power is automatically switched over. The boiler has been disconnected. Check that the equipment on the furnace side should be off. The main body of the engine and the drain door of the pipeline are opened, the steam extraction electric door and the check door are closed, and the drain door has been opened. Two small machines are hit by hand, and the electric pump is connected to maintain the water level of the steam drum. The shaft seal steam supply and deaerator steam source are cut to the auxiliary steam belt to maintain the normal water level of the exhaust device and the deaerator. After the fire is extinguished on the furnace side, maintain the operation of the fan after the secondary air volume is purged for 5 minutes. Keep empty pre-continuous rotation.

 

The unit speed is 600RPM, the jacking shaft oil pump is connected, the unit speed reaches zero, the shaft seal is cut off for steam supply, and it is put into operation. Adjust the cooling water of the main oil cooler according to the oil temperature of the unit to ensure that the oil temperature is within the normal range. During the shutdown of the unit, if the vacuum has been broken, the drain doors of each exhaust device should be closed as soon as possible to open the main unit to drain the atmosphere. After the unit is put into cranking, find the cause of the unit's vibration, and it must be cranked for four hours before restarting.

 

7. Due to the dramatic changes in the ambient temperature, the 7 # vibration increase can adjust the temperature difference of the steam side excitation side of the hydrogen cooler, increase the sealing oil temperature, reduce the vacuum setting value, reduce the unit load

 

V. Precautions:

 

1. After the vibration of the unit is increased, the development situation should be closely observed, and the load can be appropriately reduced or the door can be closed. However, if the vibration of the unit has exceeded the limit, even if the protection is not activated, it is absolutely not allowed to adopt the method of reducing the load, and an emergency shutdown of the vacuum must be taken immediately.

 

2. After shutdown, it must be remembered that the high side has suddenly opened and should be closed manually. Especially the cooling water gate

 

3. Due to vibration shutdown, during the shutdown process, it is not allowed to hang the brake during the speed reduction process. Be sure to wait until the speed is stopped before cranking for 4 hours before restarting.

 

4. After the unit is put into operation, the bending of the large shaft should be measured, and if there are obvious abnormalities, the operation time should be extended. Record the cranking current, and compare with the previous value, there is no big change.

 

5. After the unit is shut down, the furnace side is first purged, and then the wind smoke system is turned off to prevent the furnace from dissipating heat and ready to start at any time.


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