Refractory brick lining measurement and monitoring in a rotary kiln with terrestrial laser scanning

Rotary kilns are industrial furnaces used for the continuous processing of raw materials at high temperature, consisting in long steel cylinders lined with refractory bricks and revolved by gears. They are subjected to complex stresses and deformations due to high temperatures and heavy loads, so monitoring and planned maintenance are essential to avoid very expensive unexpected shutdowns and other damages to the exterior shell. The interior of a rotary kiln has been acquired with a terrestrial laser scanner during a maintenance shutdown for checking the wear of the refractory brick lining. Up to now, the refractory lining of the surveyed plant was checked every year taking manual measurements, but this technique produced discontinuous data only. The 3D model has been unwrapped to show the deviation between the current state and the design drawings. The model showed the degradation of the refractories and the thickness of the incrustations in a continuous way on the whole surface. In addition, in this application laser scanning can be considered as a diagnostic imaging technique because degradation patterns can give some indications on the deformation of the steel casing. By selecting some reference points integral to rotating parts, instead to the motionless structures outside the furnace, a permanent reference system has been established to reliably repeat monitoring over time.