Phenomenon: 

1. The swinging of ammeter pointer is too big, or the current abnormally increases and exceeds the rating. 

2. The air pressure at the fan inlet or outlet changes. 

3. The vibration and shaft-moving of the fan exceed the specified value, and the place of the fan has  abnormal noise of impacting or abrasion. 

4. The bearing temperature rises abnormally. The temperature of motor shaft  and coil rises abnormally, in serious case the smoke emits and there is burning smell, even there the flame appears. 

5. The motor power switch trips. 

6. DCS alarms, and when the main fan is in failure,  MFT acts. 

7. When the limestone fan is in downtime due to failure, the bed pressure drops, and the concentration of SO2 in flue gas rises. 

Causes: 

1. Due to abrasion, dust accumulation of the blades and high humidity of fume gas, the impeller is corroded, thus causing rotor unbalanced and  center asymmetric. 

2. The anchor screws of the fan or motor is loose. 

3. There are sundries or dust accumulating at the damper at the fan inlet , so the pin of the pulley of the connecting rod falls off. 

4. The quality of lubrication oil of the bearing is poor, the oil amount is not sufficient, the oil ring cannot bring the oil normally, the oil is mixed with water, causing bearing to abrade. 5. The cooling water for bearing is too little or interrupted. 

6. The quality of manufacturing and maintenance of bearing and rotor is poor.

Treatment: 

1. In case of the following circumstances, the fan running shall be immediately stopped.

(1) When the fan is  strongly vibrated,  impacted and abraded. 

(2) When the temperature of bearing of the fan or motor abnormally rises, and it is still not effective after the measures have been taken for treatment. 

(3) The bearing has phenomenon of burning and smoking. 

(4) When the motor temperature is too high and exceeds the permitted limit. 

(5) When the electrical equipment is in failure and the fan shall be stopped.

(6) or the fan or motor has serious defects, which endangers the equipment or personal safety. 

(7) When fire occurs and endangers safety of equipment. 

(8) When personal injury happens, and the fan must be stopped for rescuing. 

2. When the vibration, impacting or abrasion cannot cause equipment to damage, the load of the fan can be properly  reduced in order to make it continuously run, and the  fan load, operating situation of the fan shall be checked at any moment and the causes of accident shall be found out and shall be  eliminated as soon as possible. If the defects still cannot be eliminated or are continuously aggravated , they shall be reported to the shift chief-operator for stopping. 

3. When the temperature of the fan bearing rises,  the oil amount, oil quality, oil ring and cooling water shall be checked. Attention shall be paid to see whether the color and the viscosity of the lubricating oil is normal or not, and whether there is water entering into the oil, whether the oil level is within the specified scope or not, the cooling water of the bearing is blocked or not, the cooling water amount is sufficient or not and the temperature of the cooling water is  too high or not. Find out the reason, try to deal with the problem. If necessary, inform the maintenance personnel for treatment. If after the above treatment, the bearing temperature still continuously to rise and exceeds the allowable limits, it shall be reported to the shift chief-operator for stopping the running of the fan. 

4. If the motor trips due to fault, and the fan needs restarting, it must be approved by the shift chief-operator. 

5. In case before the motor trips due to fault, there is no too big current or mechanical defect, the switch shall be closed immediately once after tripping. If the switching is successful, at the same time restart the other rotating equipment in sequences. If the switching is not successful, it shall be reported to the shift chief-operator for contacting the electrical person for inspection and treatment. 

6. If the two limestone fans trip due to fault at the same time, the limestone feeding system shall be immediately stopped to isolate the limestone supply line and the boiler and to contact the maintenance person to eliminate the fault as soon as possible. If only one limestone fan is shutdown due to fault, then the damper of the fan shall be closed, and the other limestone fan shall be started and its damper shall be opened in order to provide airflow.