Method for non-destructively examining an anode of an aluminium electrolysis cell

A method for non-destructive flaw detection of aluminium reduction cell anodes, including the building of a computed model of an anode or the use of a specified model with known data on a geometry and specific resistance of the anode, the geometry and coordinates of internal defects, characterized in that:

• 1) using the computed model of the anode with the known data on the geometry, specific electrical resistance of the anode as well as on the geometry and coordinates of the location of an internal defect manifested as a specific resistance irregularity, a crack or a cavity inside the anode, a numerical method is used to calculate a spatial current flow through the anode, as well as an amplitude and direction of vectors of the magnetic field intensity or induction near the outer surface of the anode, under boundary conditions of placement on outer surfaces of the anode of at least a pair of electrically conductive contacts, which supply through the anode a specified amount of electrical current;
• 2) several cyclic calculations at step 1) are carried out under boundary conditions of placement on the outer surfaces of the anode of at least a pair of electrically conductive contacts, provided that the contacts are moved with a discretization interval that does not exceed at least double the length of an assumed defect;
• 3) results of calculations at step 2) are represented in a form of a 3D-matrix of amplitudes and directions of vectors of calculated intensities or inductions of an electromagnetic field at discretization points near the outer surface of the anode;
• 4) at least a pair of electrically conductive contacts that supply the specified amount of electrical current through the anode are placed on the outer surfaces of an inspected anode;
• 5) at least one sensor is placed near the outer surface of the inspected anode, and the amplitude and direction of the magnetic field intensity or induction vectors at the same discretization points as at steps 1)-3) are measured and represented as a 3D-matrix of measured magnetic field intensity or induction vectors;
• 6) the 3D-matrices of calculated and measured magnetic field intensity or induction vectors at the same discretization points near the outer surface of the anode are compared;
• and, in the event of a permissible deviation (less than 20%) of the measured and calculated values of the amplitude and direction of vectors at the same discretization points near the surface of the anode, the anode is recognized as high-quality;
• in the event of a significant deviation (more than 20%) of measured and calculated values of the amplitude and direction of vectors at the same discretization points near the surface of the anode, the anode is recognized as poor-quality.