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POWDER TESTING - physical properties of powder and bulk solids

Mass flow silo

mass flow or funnel flow siloTo avoid problems during the storage and discharge of cohesive bulk materials, silos should always be designed for mass flow. In the case of mass flow silos, the entire quantity of bulk material is in motion during discharge. In the case of funnel flow, only a fraction of the bulk material is in motion. This may lead to:

  • Different residence times of the material in the silo and dead zones
  • Segregation
  • (Eccentric) rat-holing
  • Fluidization or shooting of the material
  • Unsteady flow
  • Time consolidation

Depending on the bulk material properties, ideal dimensions of the silo and hopper or even the wall material, mass flow or funnel flow will be calculated. 

After the bulk solid measurements there is an available online calculation tool to determine the limiting criterion for mass flow / funnel flow. With the measured material data, the necessary hopper angle or the appropriate wall material can be easily determined.


Excerpt from the automatic silo calculation report:



φe> φwh(Ph(hc)) = 33.5 °> 8.8 ° TRUE
critical cone angle  ßcrit  <= 40.4 ° MASSFLOW


Limit criterion for mass flow / funnel flow

Measurements and evaluations of physical properties of powders and bulk solids yield locus time consolidation