Abstract: This paper introduces the expansion joint failure of the 410t/h boiler ignition air duct in a factory and treatment measures from three aspects covering equipment manufacture,installation and process operation.According to the provisions of the technical agreement,the metal material performance of the joint point contacting flue gas directly shall not be lower than 0Cr25Ni20Si2.But ordinary stainless steel was used in the manufacturing process.During the installation process,the pre-dislocation amount of 80 mm was not set aside according to the design requirements,resulting in serious bellow deformation of expansion joint,internal casting material damage and falling off in the operation process.During ignition,the rated capacity of the burner oil gun was too large;the atomizing air pressure was too low;the oil combustion of light diesel was insufficient;the temperature of combustion chamber connected by expansion joints was higher than the design temperature;high-temperature flue gas entered into the expansion joint bellows.And these eventually led to expansion joint breakdown.After the breakdown,the expansion joints were rectified and repair welding was carried out;the damaged anchor nail and casting material were repaired.After ignition,the boiler met the needs of operation.It＇s suggested that expansion joint shall be designed and manufactured again according to the actual situation of the boiler installation and operation parameters;new type of seal shall be used to avoid the high-temperature flue gas entering the corrugated tube parts.