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During operation, boiler exhaust fans often experience accidents such as motor burnout, shaft misalignment, runaway impellers, and bearing damage, which pose a serious threat to the safety of equipment and workers, and cause certain economic losses to enterprises. For example, on March 17, 1997, an overspeed accident occurred in a boiler exhaust fan (model: Y4-73-No16D) at a facility in our province. The broken impeller blade flew out of the casing and reached a distance of 10 meters; fortunately, no one was there at the time, which prevented any casualties. Post-inspection revealed that all impeller blades had fallen off ； The wheel hub is severely deformed ； Bending at the main journal: 0.15 mm ； There is a large amount of dust accumulation in the fan casing and the inlet flue, etc. The main reasons are: insufficient implementation of accident prevention measures for the induced draft fans, infrequent maintenance, and lax enforcement of the regular major repair system and inspection system. How can accidents involving exhaust fans be effectively prevented? Through the analysis of numerous accident cases involving exhaust fans, the main causes of these accidents are as follows: (1) The furnace operator failed to follow the operating procedures strictly, or even carried out illegal operations, which led to the exhaust fan starting under load and causing the motor to overheat and get damaged. (2) The fan does not undergo regular major repairs, or the quality of such repairs is inadequate; this leads to looseness between the impeller and the shaft as well as loosening of the rivets on the hub, resulting in shaft displacement or the impeller spinning out of control. (3) The dust collector does not provide effective dust removal, or no dust removal equipment is installed; the flue ducts are not cleaned regularly, resulting in excessive dust accumulation, which causes severe wear on the impeller blades of the exhaust fan. (4) The impeller blades lack anti-wear measures, and they get worn out by dust; in severe cases, this can lead to blade breakage and bending of the main shaft. (5) Regular maintenance was not carried out properly; the fan bearings lacked oil and water, resulting in overheating and damage to the bearings. (6) Unclear electrical work techniques, poor sealing of the motor terminal box, loose wire connections, and missing phases in the circuit can cause damage to the bearings or the motor. (7) Inadequate or insufficient routine inspections, or delayed response to detected faults, allow the failure of the induced draft fan to escalate into a more serious damage incident. (8) Inadequate and vague systems, as well as improper operations by furnace operators after drinking alcohol, can cause damage to the exhaust fans due to human error. Based on the above analysis of the causes, the following preventive measures should be taken: (1) Strengthen operation management and prohibit illegal operations. There must be strict operating procedures for the startup and operation of the boiler exhaust fan. If the exhaust fan must be started under no-load conditions, it is strictly prohibited to start it under load, especially when the boiler is being ignited as the flue gas temperature is too low. If the exhaust fan is started under load (i.e., with the inlet dampers fully open), the starting current will increase significantly, the starting time will be prolonged, and the fan motor is prone to overheating, which may lead to damage due to overload ； When the boiler (especially a pulverized coal furnace) is started up, attention must be paid to the sequence in which the blower and induced draft fan are turned on; the order cannot be reversed. That is, the induced draft fan should be turned on first and operated for 10 minutes to remove any ash or flammable gases accumulated in the furnace and flue pipes, before the blower can be started. If the blower is started first and then the exhaust fan, this not only increases the load on the exhaust fan, leading to overheating and damage of its motor, but may also cause an explosion in the furnace. (2) Support regular major overhauls of the exhaust fans, and ensure strict control over the quality of these repairs. The induced draft fan should be overhauled regularly. Eliminate potential hazards related to accidents at an early stage; overhauls must be thorough and comprehensive. It is necessary to carefully check the wear on the impeller, the balance of rotation between the main shaft and the impeller, whether there is any looseness or damage in the internal connections, whether the inlet dampers operate smoothly, as well as the lubrication and cooling conditions of the bearings. (3) Perform surface strengthening treatment on the impeller blades to improve their wear resistance. Since the exhaust fans convey flue gas at around 200°C, the gas contains a large amount of fly ash as well as corrosive gases such as SO2; as a result, the fan blades suffer severe wear, which can lead to issues such as reduced fan output, vibration, and blade breakage. Therefore, surfacing welding should be performed on the working surface of the blade or on areas that are severely worn in order to improve its wear resistance. For surfacing, a DC welding machine should be used, along with the manual arc welding method. Special wear-resistant surfacing electrodes (such as Wear-Resistant No. 1, Mo-Cr-B cemented carbide wear-resistant electrodes, etc.) should be employed, and these electrodes must be dried at 300–350°C for 1 hour before use. Before welding, the dust and rust on the surface of the blade should be removed, and it should be preheated to 100°C. Welding should be carried out using a low current, low voltage, controlled heating rate, short arc length, and symmetrical welding techniques. Practice has shown that blades that have undergone surfacing treatment exhibit **improved wear resistance, which not only addresses the frequent wear of fan impellers but also lays a solid foundation for the safe operation of the fans. (4) Implement flue gas dust removal measures, clean the flues regularly, and improve the working environment of the exhaust fans. Units equipped with dust removal equipment should strengthen the management of their dust removal operations in order to improve efficiency ； Units without dust removal equipment should regularly and in appropriate quantities add boiler-specific descaling agents into the furnace, and promptly remove ash accumulated in the flue ducts to prevent blockages and damage to the impellers. (5) Strengthen the daily maintenance and routine inspections of the exhaust fans, and address any issues that arise promptly. The boiler operator must regularly check the voltage, current, oil level, temperature, and noise of the exhaust fan. Check whether the cooling water and other systems are functioning properly. If faults such as fan vibration, oil leakage, bearing overheating, loose foundation bolts, damaged coupling cushions, or interruptions in the cooling water supply are detected, they must be addressed promptly. When a loud noise from the fan, severe knocking sounds, or a humming noise from the motor is heard, or if a burnt smell is detected, or if the motor’s temperature rises sharply, the machine should be stopped immediately, and appropriate actions taken for prompt repair. During routine maintenance, electricians must be careful and thorough when wiring, securing the wire ends firmly to prevent missing phases. At the same time, the outlet holes in the junction box should be sealed tightly as much as possible using rubber gaskets, to prevent a flow path from forming between the front bearing of the motor and the air, which could affect the lubrication of the bearing and lead to overheating and damage of the bearing. (6) Establish and improve equipment management systems, increase training for boiler operators, and enhance their operational skills.