Non-Destructive Testing of Baked Anodes Based on Modal Analysis and Principal Component Analysis

Baked anodes quality control is still mostly based on core sampling and characterization. Only a small proportion of the production can be tested by this method due to the costly, time consuming, and destructive nature of the analytical techniques. Furthermore, the core properties are not necessarily representative of those of the whole block. A rapid and non-destructive method for anode quality control based on vibration modal analysis is proposed. A number of baked anodes produced under different conditions at the Alcoa Deschambault smelter were selected. These were excited mechanically at different locations and the vibration signals of the blocks were measured by accelerometers. Principal Component Analysis (PCA) was used to cluster the vibration modes of the anodes. It is shown that the proposed approach allows detecting and distinguishing different types of anode internal defects. Some of the tested anodes were cut and imaged in order to confirm the results visually.