Causes of Damage：

1. The operating speed for rinsing the drum water level is too fast, the water level gauge glass tube is damaged due to uneven heating caused by the suddenly changing of pressure and temperature. 

2. Large stress occurs due to the suddenly attracting of external cold air or the touching of cold water drop on the water level gauge glass tube. 

3. The upper and lower packing of the glass tube is pressed too tightly or the packing is dry.

4. The maintenance to the water level gauge during operation is not sufficient; the water level gauge has not been cleaned for a long time, so the water level can't be seen clearly. 

Treatment：

1. When the water level gauge of drum is damaged, the damaged water level gauge will be immediately disconnected. 

2. If one of water gauges of steam drum is damaged, the monitoring to the other water gauge shall be monitored and the positive measures shall be taken to repair the damaged water level gauge. 

3. If the two water level gauges of steam drum are both damaged, if the  following conditions are available, the boiler is allowed to run 2 hours. 

(1)The automatic control system of feed water is reliable.

(2) The alarm device of water level is reliable. 

(3) The water level gauge indication on the two dial is correct and has been calibrated with drum water level within 4 hours , the indication is normal. 

(4)If there is no local water level gauge running, the stability of boiler load and combustion shall be kept as far as possible, and one local water gauge shall be restored to run as soon as possible. 

4. If the automatically regulating device of the feed water or the alarm device of water level does not act reliably, then it is permitted to maintain operation of the boiler according to reliable electric contact water level gauge for 20 min. 

5. If the local water level gauges are completely damaged, and the electric contact water level gauge does not operate reliably, the boiler shall be immediately stopped.