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.
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.