Multivariate control for three variables of an industrial roll-type electrostatic separator

Hotelling´s T² charts have already proven their effectiveness in the multivariate control of electrostatic separation process. The aim of this work is to extend the use of these charts from two to three variables, in order to improve the statistical control of an industrial roll-type electrostatic separator designed for the recycling industry. In the case of electrostatic separation processes, the use of: Hotelling´s T ² chart for three variables would allow to control on a single graph the correlation between the masses accumulated in the three boxes of the product collector. The results of the study carried out on a pilot-plant electrostatic separator for metals and insulators from electric cable wastes in Algeria demonstrated the effectiveness of such a chart in detecting out-of-control situations: accumulation of dust particles on the high-voltage electrodes and reduction of the input flow of raw materials.