They are used in many solids handling processes by a wide range of industries. The objective of all silo designs is to obtain reliable and controllable flow of particulate solids in such processes. However, the fact is that various problems in solids flow occur very frequently in many solids handling processes.
No flow takes place when the outlet of the silo is opened. A stable arch that prevents flow is formed above the outlet. This may happen both with fine powders and coarse solids, and is generally attributed to the development of cohesion in the solids or to mechanical interlocking.