The solid-wall bowl of classifying decanter centrifuge has a cylindrical section for good separation and clarification of the liquid or classification of the solids and a conical section for dewatering the solids or concentration of the precipitated coarse particles. The product is fed info the decanter through the feed and is conveyed to the separating / classifying chamber through the distributor. The liquid level can be adjusted by regulating plates. The coarse solid particles are forced to the wall of the bowl by the centrifugal force. The scroll conveys the precipitated solids particles to the solids discharge. The clarified liquid or the classified fine particles are discharged from the separating chamber via replaceable regulating plate.