1. When the power supply of the single-stage furnace is outage.
       2. When the gas supply or water supply to the single-stage gas generator is stopped for more than 4 hours.
       3. When the single-stage gas generator skirt is burned through and the air supply from the bottom of the furnace overflows from the ash tray and cannot be handled.
       4. When the water jacket of the single-stage gas generator breaks or becomes welded, and it cannot be repaired immediately during operation.
       5. There is a problem with the feeding facilities, manual feeding cannot be achieved, and the gas furnace outlet temperature reaches above 600°C.
       6. When a serious failure occurs in the gas pipeline or dust collector and cannot be dealt with.