The granular material to be sorted is delivered onto a moving belt (9) and a contact-less inspection is carried out so that sorting can follow through underpressure corresponding to the signals of the contactless inspection (12). The underpressure acts by valves in a cylindrical body on the granular material. The cylindrical body and valve can rotate about an axis as a guide pulley for the belt. The optical or radiometric inspection takes place on a belt (9) which has grid pattern divisions.
