PURPOSE: To effectively prevent the bridge of powder from being formed by placing a porous material on the inner wall surface of the lower part of a storage tank, connecting a pressure reducing device and a pressure device to the porous material by a pipeline and repeatedly applying the pulsation of air or fluidity due to a continuous pressurization and degasification to the inner wall surface of the lower part of the storage tank.

CONSTITUTION: Powder material is thrown into a storage tank 1 from an upper conveyor or the like and exhausted from a lower exhaust pipe 2. A porous material 3 such as an artificial graphite, a ceramic material, etc., is provided on the inner wall surface of the lower part of such a storage tank 1 where a bridge is formed. A pressure air device 5 and a pressure reducing device 6 such as a vacuum pump are respectively connected through valves to a connecting port 4 formed on the tank wall facing the porous material 3. Then, the respective valves are selected by a controller 7, so that pulsating or continuously pressurized air is applied so as to apply fluidity to the powder material by the pressure air device 5 through the porous material 3, and the degasifying operation due to pressure reduction permits the formation of a bridge to be effectively prevented.