Abstract: In a suction conveying installation in which different bulk materials are conveyed from respective supply containers to a separator which may serve as a weighing container, the separator is adapted to serve as a mixer and comprises at the bottom at least one ventilation valve to be opened after the end of the separating or weighing operation while the suction fan of the installation is still running, so that air is drawn into the container from the bottom to entrain and mix the materials. Constructional details of the separator including various valve arrangements are described, also certain control arrangements including a pressure monitoring device downstream of the separator.