What is funnel flow?
In case of funnel flow the product flows through the core. Owing to this areas exist where the product is at rest (stagnant zones).
This can result in the following problems:
When the silo is filled again before it is completely empty, ageing and decay of the product will occur.
If the silo is used for several products, contamination will occur.
In some case the stagnant zones grow, so that at a certain moment the product only flows from a channel (rat hole) above the opening. Then the risk is great, that flow will stop altogether.
The collapse of stagnant zones can lead to uncontrollable flow of product (flooding).
For these reasons funnel flow is only applicable for coarse, free flowing products, where ageing or decay is not important.