1. Water level gauge quality has problem;
2.The installation is not qualified;
3. The method of making the protective device for the boiler drum water level into operation or the method for quitting the operation , or the flushing method are not correct.
4. The overpressure test of the boiler is not disconnected
5. The boiler drum pressure or temperature suddenly changes
6. Antifreezing measures in winter are not perfect.
7. Other damages happen externally.