Quality Criteria of Sorting Operations

ABSTRACT DIFFERENT possibilities of sorting index defini-tions are explored and two sets of superior mutually deterministic sorting efficiency and deficiency indexes are proposed whereby the accuracy of any sorting or siz-ing systems can be objectively evaluated by sampling the composition of inflow and outflow conduits. Sorting effi-ciency versus sorting errors and degree of grade purity versus grade contamination are expressed by means of a simple mathematical model comprising weighting para-meters representing raw material inflow rate, grade distribution in raw material, relative cost of grades and distribution of outflow rates. Statistically significant samples drawn from outflow conduits determine frac-tions of pure grade. The concept of optimal sorting aper-tures was introduced whereby any of the sorting deficien-cy indexes can be minimized.