Phenomenon: 

1. The water level inside the water gauge is higher than the normal allowed water level. 

2. The water level alarm alarms and the high water level signal lights. 

3. The indicating positive value of the electric contact water level gauge increases. 

4. The flow of feed water is abnormally larger than that of steam. 

5. The salt content in steam increases. 

6. The temperature of superheated steam drops. 

7. When the boiler is seriously overflow and water hammer occurs in the steam pipe, and steam emits from the flange.

Causes: 

1. The automatic regulator for feed water is in malfunction, and the  feed water control device is in failure. 

2. The indication of water level gauge, steam flow and feed water flow gauge are not correct, the operator misjudges and makes wrong operation. 

3. The feed water pressure suddenly rises. 

4. The external load sharply rises. The pressure of main steam main pipe suddenly becomes low, and the load of this boiler increases greatly, thus causing the water drum level to rise high 

5. The operators are careless and did not sufficiently monitor the water and did not adjust in time or makes wrong operation. 

Treatment: 

1. When the boiler steam pressure is normal, the water supply pressure is normal and the boiler steam drum water level exceeds 50 mm, the correctness of water level meter of the electric contact must be verified and must be quickly compared with steam drum water level. When necessary, the water level gauge must be flushed. 

2. If the water level is too high due to the failure of automatic regulator of feed water, the feed water shall be manually controlled instead of automatically controlled, and the control  valve shall be turned down to decrease water-feeding. 

3. If the water level rises due to abnormal pressure of feed water, it is required to  immediately contact with the person on-duty for steam turbine in order to make the water pressure normal. 

4. If the water level continues to rise, open the water-discharging valve of emergency or the regular blow-down valve to discharge valve. 

5. After the above treatment, if the steam drum water level is still rising and is more than 100 mm, turn down or turn off the water-feeding valve. Open the re-circulation valve of the  economizer when water-feeding is stopped, and quickly compare the steam drum water level with the water level gauge , and when necessary, flush the water level gauge.

6. According to the situation of steam temperature dropping, turn down or turn off the  attemperation water valve; when necessary, open the water draining valve of the superheater. 

7. If the water level of steam drum exceeds the visible water level of the upper part of the water level gauge, immediately damp down and stop the boiler, and shift chief-operator, contact with the operator for steam turbine to reduce the load or emergency shut down the boiler. 

8. Strengthen water-draining from the boiler, pay close attention to water level. When  water level is shown in the water level gauge, adjust it to the normal water level.

9. After the fault has been cleared, recover the boiler unit operate as soon as possible. 

Prevention for overflow of Boiler: 

1. Continuously to strengthen the monitoring to water level gauge, regularly compare the water level of each water level gauge, if the water level is inconsistent with the water level gauge, immediately find out the reason. 

2. Rinse the water gauge regularly in order to ensure the correctness of the indication.