When a bulk solid flows in a silo, shocks and self-excited vibrations can occur. The frequency of the vibrations triggered by the bulk solid can be greater than 1 Hz, sometimes even in the audible range above 20 Hz, although small amplitudes usually prevail. If audible vibrations are generated, one speaks of “silo honking”, in the case of vibrations with a longer time interval of “silo quaking”. Since there are no generally applicable rules for avoiding the effects mentioned, an overview of models on the causes and experiments to explore the relevant mechanisms is given. Using examples from the literature, problem solutions are presented.

Storage and Flow of Solids

Silo Quaking and Silo Honking

The storage bin, silo or hopper is one of the most important items of equipment in any bulk solids handling installation, since a poorly flowing hopper can have repercussions extending throughout the plant. All too often hoppers are ‘squeezed in’ after the remainder of the system has been designed, and this can result in various flow problems, such as those described generally as ‘arching’ or ‘rat-holing’ (section 2.3.4). Obviously, if this occurs, even the most sophisticated and expensive equipment downstream of the hopper will be unlikely to perform effectively because of the erratic supply of material. Part of the problem is often a lack of appreciation by designers and operators that, for a system to operate satisfactorily, bulk solid must flow from the hopper when required and in a predictable manner. Thus, as with any other part of the handling system, gravity-flow storage hoppers should be designed or selected to handle the actual product under consideration.

The design of storage bins and hoppers

When a process modification evolves a new, or a partly unknown, material, it is very important to establish a good basis for the material characteristics. If a material sample is available, it is possible to measure various material parameters and characterize the material perfectly. An accurate measurement of only a few material parameters will allow for a better selection of the necessary process steps for the product handling and selection of the right storage equipment. In this paper, different ways to characterize powder and bulk material are introduced. A system to select the right storage and handling equipment is discussed.

Storage and Flow of Solids

Citations

Silo Quaking and Silo Honking

The design of storage bins and hoppers

Characterisation of Powders-Precondition for Plant Engineering

Silo Design for Flow

Formation of stable arches in vertical and inclined main ore chutes

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