Notice of Removal: Estimation of the thickness of refractory ceramics by the impact-echo method

A blast furnace surrounded by steel plates from its outer side and by a refractory lining from its inner side is used to acquire pig iron from iron ores. The refractory lining is a wall of refractory bricks which can withstand elevated temperature as high as 1600 degrees. Although the refractory lining has high thermal resistance, it is inevitable for the lining to suffer from degradation of its thickness and properties when the furnace is operated over a long period of time. Therefore, researches using non-destructive testing technique have been carried out to do accurate measurement of the remaining thickness of the refractory lining in a blast furnace. In this work, the state of the refractory ceramics was characterized by the impact-echo technique. To measure the thickness of a refractory lining by the impact-echo technique, the vibration characteristics of the refractory ceramic should be identified first. The vibration characteristic of refractory ceramics has been identified by assuming the ceramics as an isotropic material. However, in practice, refractory ceramics exhibit anisotropic properties since they are manufactured by pressing ceramic powder along one particular direction. Hence, the impact-echo technique should be well refined to reflect the detailed properties of the refractories for accurate characterization of present state.