The classification of polydisperse materials is widely used in many industries. Of the wide range ofclassification equipment, the most promising are multistage gravitational classifiers. The classification process inmultistage gravitational classifiers is quite complicated and requires the necessary experimental research to ensurethe given efficiency. To receive reliable information allowing to obtain the most effective recommendations for theirstructure and use, a set of experimental research was carried out. The research results showed that multistageclassifiers of small sizes provide a consistently high quality of separation, however their performance, for anapparatus with a cross section of 80x80 mm no more than 100 kg/h, is insignificant, as a result of which they cannotbe used for most production processes. Classifiers with higher performance must have significant sizes. It isadvisable to use multistage shelf classifiers with boundary separation sizes of 0.5-2 mm. With a boundary size of lessthan 0.5 mm, a steady decrease in the separation efficiency is observed, and with a boundary size of the order of0.05-0.1 mm, the classification efficiency decreases sharply. With an increase in the boundary separation grain ofmore than 2 mm, a decrease in the classification efficiency is also observed (figure 1). The experiments to determinethe separation efficiency in the modernized and conventional structures of classifiers in the separation of quartz sandwith particle sizes of 0-2 mm relative to the boundary separation size of гр = 1 mm showed the following. Themutual arrangement of the efficiency curves shows that an increase in the separation efficiency for the modernizedclassifier is up to 10% when the optimum, providing the highest quality separation, air velocity per section of theapparatus is achieved. Similar results were obtained for other materials (sylvinite, meal, gypsum) for variousboundary separation sizes (from 0.5 to 2 mm). In general, the separation efficiency in the modernized structure of theshelf classifier for various materials was 5-10% higher than in a conventional one. The experimental research of themodernized classifier structure showed that the proposed structural additions, ceteris paribus, contribute to a moreuniform distribution of material over the working volume of the apparatus, which, of course, leads to an increase inthe quality of separation.