| 摘要 |
PROBLEM TO BE SOLVED: To remove a metal oxide and impure foreign matters adhered to the tip of a burner by immersing and cleaning at least the flame opening-near portion of the burner, wherein plural inner pipes for the flow of a combustion- supporting gas are inserted into an outer cylinder for the flow of a combustible gas, in a cleaning liquid to which ultrasonic vibrations are given. SOLUTION: When a burner 1 for an optical fiber preform is cleaned, the burner 1 is immersed in a cleaning liquid 8 in a posture that a hydrogen- charging pipe 5 and an oxygen-charging pipe 6 are opened on the outside and that a flame port 4 is lowered. Air in an outer pipe 2 and air in an inner pipe 3 are thereby discharged from the hydrogen-charging pipe 5 and the oxygen- charging pipe 6, respectively, and the burner 1 is immersed in the cleaning liquid 8 up to the height of the water level of a water tank 9 for ultrasonic cleaning. The ultrasonic waves are then generated from an ultrasonic wave oscillator 7 to clean the burner. An about 10% hydrogen fluoride aqueous solution and an about 3% nitric acid aqueous solution are used as the cleaning liquid 8. The oscillation frequency of the ultrasonic wave oscillator 7 is preferably 10-100 kHz. Thereby, a metal oxide adhered to a place close to the flame port 4 can efficiently be removed.
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