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Indicizer Advisor September 2002

From Johanson Innovations, Inc. the exclusive source for Indicizer technology.

In the last issue we focused on the Flow Rate Index (FRI) and how it is used to measure flowability in free flowing fine powders. You can get a copy of the June Newsletter or this current issue from www.indicizer.com.

In this issue of the Indicizer Advisor we will focus on the Hang-up Indicizer and the two indices Arching Index (AI) and Ratholing Index (RI). Both of these indices measure the cohesive strength of a material under consolidation. AI is the outlet diameter needed to ensure arch collapse in a conical mass flow bin and measures a powders tendency to bridge over hopper outlets. In general, a higher AI indicates poor flow and a lower AI indicates better flow. RI is the outlet diameter needed to ensure rathole failure and cleanout in a funnel-flow bin. In general a higher RI indicates poor flow and a lower RI indicates better flow.

Lets look at how the AI and RI can be used to evaluate the cohesive strength of powders and in turn determine flowability of powders as affected by hopper outlet diameters, storage time and conditions as well as caking tendencies.

AI is the outlet required so that a particular material will flow and continue flowing from the hopper or other storage silo. If the measured AI of a material is 1.0 ft, then you can expect that material to flow out of any mass flow hopper that has an outlet diameter of 1 ft. or greater. The same applies to RI in funnel flow hoppers. If the measured RI is 2.5 ft then you can expect flow from outlets 2.5 ft or greater.

If tests indicate that you will have flow problems then you will need to make an adjustment. You can lower the AI or RI of a material by reducing the amount of material within the bin thus reducing the consolidation pressure acting on the material. If you have an alternate process system with larger outlets you might want to process the material in that system. You can also pre-qualify raw materials from suppliers to make sure that those materials will flow in your systems. Or you can adjust your processing conditions so that your material meets your equipments parameters.


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INDICIZER ADVISOR SEPTEMBER 2002