Automation of the processes of surface measurement and of deposition by welding for the recovery of rotors of large-scale hydraulic turbines

Large-scale hydraulic turbines of electric power plants usually present erosion due to cavitation. Periodically they need to be repaired through material deposition by welding. In this context, the present work deals with the development of an automatic methodology to perform this task. It starts with the automated measurement of the surface affected by cavitation by means of a three lines laser optical sensor, which is used to obtain the mathematical description of both the eroded and original surfaces. Next, this methodology defines the location of the weld beads in each layer and the welding trajectories for a plasma torch with automatic wire feeding to appropriately fill these cavities. Finally, the automated measurement of the recovered surface is performed and analyzed to evaluate its geometry. Practical results of the developed strategy were obtained in a specimen that reproduces the geometry and welding conditions of a typical cavity of one of the blades of a hydraulic turbine. The proposed methodology produced very good results.