| 摘要 |
PURPOSE:To restrict a responsive amplitude of a Lance tube and to enable damage of a boiler tube or the like to be prevented by a method wherein said Lance tube is constituted by connecting a plurality of pipe members having different wall thicknesses in such a way as a resonance point where a natural frequency and the number of rotation of the Lance tube are coincided to each other is set before a point where said Lance tube is projected most into the boiler. CONSTITUTION:A natural frequency is reduced by properly selecting a combination of pipes (combination of the lengths l2, l2, l3 or thicknesses t1, t2, t3) and a point (lambda0=1) where a natural primary frequency of the Lance tube and the number of rota tion of the Lance tube are coincided to each other is made faster than a point project ed most into the boiler (a change-over point for an advancing or reversing movement of the Lance tube). In turn, if the point is passed by a dangerous speed at a time when the speed of the point is faster than the change-over point at the advancing or reversing movement of the Lance tube, a vibration response under an unbalanced condition of the Lance tube is of only a displacement amount of the Lance tube, resulting in that the vibration response can be reduced more. Due to this effect, it is possible to prevent a damage or the like of the boiler tube caused by vibration of the Lance tube 20.
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