1. MFT is manually acted on operation desk emergency boiler stop button .
2. The induced draft fan is fully stopped.
3. Primary fan is fully stopped.
4. The second fan is fully stopped.
5. High pressure fluidized fan is fully stopped.
6. The steam drum water level is low  III value.
7. The steam drum water level is high Ⅲ values.
8. The pressure of boiler hearth is high Ⅱ value (2 out of 3) (delay 3 seconds).
9. The pressure of boiler hearth is low Ⅱ value (2 out of 3) (delay 3 seconds).
10. The primary air flow to the distribution board is low and  3 seconds are delayed.
11. The pressure of high pressure fluidization air mother- tube is low Ⅱ value and 3 seconds are delayed.
12. The main valve is closed.
13. Bed temperature is higher than 990 ℃.
14. Bed temperature is  below 650 ℃ and the air duct burner is not in operation.
15. Bed temperature is below 540 ℃.
16. Air volume is less than 25%  (delay) or oxygen is < 1%.
17. Sowing coal air is lost (delay) , (two coal -sowing fans are fully stopped and the bypass is not opened or the pressure of main tube is low).
18. Fuel is fully interrupted and coal -sowing fan is fully stopped.
19. The superheater protective device is acting. The flue gas of superheater is at high temperature, the steam flow rate is low.(lsh)