Abstract: The disclosure, for classification, is to a pressure vessel with fill valve admitting thereinto material to drop into a perforate diaphragm to be transferred, vacuum pulling in the material upon the perforate membrane or diaphragm, to upstand thereabove, the gas plenum below the diaphragm having activating gas inlet valve means communicating therewith and opened at intervals temporarily to break the vacuum. When a batch of material has been drawn in, the fill valve and the vacuum (and air break) valves are automatically closed, the activating gas inlet valve is opened to admit activating gas, as compressed air, to pass upwardly through diaphragm and activate the material to a highly flowable state. A discharge valve is then opened to let the pressurized material flow out through a discharge line to point of transfer.