By Greg Mehos and Dave Morgan, Jenike & Johanson

Extensive experience has shown that designing equipment without regard to the actual bulk materials being handled often leads to flow problems, such as arching, ratholing, erratic flow and even no flow. By measuring the flow properties of a bulk solid, the flow behavior of the material can be predicted, and more reliable hoppers and bins can then be designed. Two primary flow patterns can occur in a bin or a silo: mass flow and funnel flow. In mass flow, the entire bed of solids is in motion when material is discharged from the outlet. This behavior eliminates the formation of stagnant regions in the vessel, and affords a “first-in, first-out” flow sequence, which provides a more uniform velocity profile during operation. A uniform velocity profile also helps to reduce the effects of sifting segregation.»

By Thomas G. Troxel, Jenike & Johanson, Inc.

Blending and segregation are two opposite and competing processes in solids handling that ideally fit the expression “two sides of the same coin.” But, if you think about it, coins have three sides and sampling completes the idiomatic expression perfectly. Blending is a necessary and essential process operation widely employed in many industries and materials, from nano-scale powders to run-of-mine ores. Segregation is almost always an unwanted consequence of handling operations that reverses the blending process or creates a need for blending where it might not otherwise be necessary if it were not for the effects of segregation. Sampling is the vitally important tool for measuring and quantifying a blend, understanding the sources and effects of segregation and for troubleshooting problems. »