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Bulk solids   Mass flow   Core flow   Bridging   Lab equipment  

Funnel flow / core flow / ratholing

Sometimes useful, mostly painful

The type of flow where part of the product in the silo is at rest (stagnant zones) is called funnel flow, core flow or ratholing.

Core flow: part of the contents is at rest

Funnel flow is only applicable for coarse, free flowing products, where ageing or decay is not important. In all other cases mass flow should occur, for the following reasons:

  • The product will be liable to ageing and decay, when the silo is filled again before it is completely empty.
  • Contamination will occur if the silo is used for several products.
  • Flooding: the collapse of stagnant zones leads to uncontrollable flow of product.
  • Flow will stop completely in the case that the product keeps building up, so that the outlet is blocked.


  BSE bulk solids engineering
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