Apparatus for breaking up solidified particulate material in a storage container has a housing lowerable into the container on the lower end of a suspension element. A flailing element holder is rotatably mounted on the housing for rotary movement relative thereto about a substantially vertical axis when the housing is suspended in the container. An elongated flexible flailing element projects from the holder, and the holder is rotated relative to the housing to cause the flailing element to engage and break up solidified particulate material when the housing is suspended in the container. The housing has a torque-balancing device mounted for rotation relatively thereto about a substantially vertical axis, and the torque-balancing device is rotated in a direction opposite to the direction of rotation of the flailing element holder to substantially balance torque produced by rotation of the flailing element holder and thereby substantially prevent angular movement of the housing about a vertical axis when the flailing element holder is rotated.