The spiral sorter ŠT is intended for wet sorting of grains during the treatment of ores and other minerals and also for separating solid particles from liquid – drainage. Together with the mill, it usually creates a closed or open grinding cycle.

An essential part of the spiral sorter is the inclined trough in which the spiral rotates. The mash is fed into the trough through the filling nozzle located on its side. The size of the level and thus the length of the submerged spiral depends on the slope of the sorter. The fine parts of the material are carried away by the water flowing over the overflow edge for further processing. The coarser grains sink to the bottom of the trough and are gradually carried to the sand chute, from where they are taken to be ground into a mill or for other use.

The sorting effect and granularity of the individual products of the sorter depends on the slope of the trough, the amount and density of the supplied mash and other factors.