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What is bulk density?

When you’re generating saleable product, weight in KG or LBS is often the most important number. Operators often have the target weights engrained in memory. Unfortunately, the movement of material in a conveyor, through a blender or screener, or in a storage silo is all based on volume, usually in KG/M3 or LB/FT3. The capacity constraint is almost always the volumetric rate it can move or capacity it can hold.

This is why Hapman and any quality supplier of processing equipment will be adamant about receiving accurate bulk density information about the materials being moved. And if you’re moving multiple materials, we’re going to want to know about all of them.

We have found that customers often don’t know this value and documentation with these details can vary from the material as it exists in the process. The bulk density as it’s shipped in a densified bulk bag is often significantly higher than when the material is processed and conveyed in a conveyor. Various flours could be 50-75 lbs/ft3 (800-1200 KG/M3) densified in a bulk bag, as hard as a rock. Once that material goes through a bag conditioner, lump breaker, several conveyors, and a blender, it will be aerated and fluffed to a state where it may be 50% of the bulk density as arrived.

The most common value readily available is typically density called out on SDS sheets, which almost always refers to specific density or specific gravity and is irrelevant for processing equipment sizing as it refers to the density of a single solid piece of material often 2-3 times greater than the bulk density. Most OEM’s are looking for Loose Bulk Density (LBD), which often are given as a range.

If you guess at a bulk density or use a bulk density from the wrong part of the process, you can find equipment grossly undersized unable to make the desired rate and regularly plugging or spilling resulting in low Overall Equipment Effectiveness (OEE). Less of an issue, you may find you have more capacity than needed and could have reduced project cost by 20% or more with smaller equipment.

The best scenario is to pull samples of the actual material that will be conveyed or processed as close to where a piece of equipment will be located. This will account for potential of aeration (lower LBD), settling (Higher LBD), and the fact that values for Loose Bulk Density often aren’t available. The Hapman team can collect this for you or we can send you a sampling cup for you to collect the sample yourself.

Click here to watch a video on Bulk Density Calculations.