1. The negative pressure of boiler hearth is increasing, the flame monitor can not monitor the flame.
2. There is completely no indication of fire detection.
3. When the fire is extinguished, FSSS protection acts and the fire signal alarms. Primary fan, coal mill, and coal feeder trip out, and the induced draft fan or the forced draft fan may trip.
4. The electrically operated gate of the attemperation water is closed, the fuel oil quick- closing valve is closed.
5. OS screen alarms, vertical disk luminous word flashes for alarming.
6. The steam temperature, steam pressure and load decrease sharply.
7. The oxygen indication is full.
8. The water level firstly drops then rises.