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Bulk Density & Powder Handling

Bulk Density & Powder Handling 

An important factor in Powder Handling and Materials Handling Processes is the bulk density of Dry Bulk Solids. The bulk density of a powder plays a crucial factor when determining materials characteristics, as properties such as flowability, storage, and stacking are all affected. 

An example; if a customer was to request Materials Handling Equipment from Trantec, we would generally use the bulk density of the product to indicate required capacities for any storage bins or containers (such as Hoppers, FIBC Dischargers, Sack Tip Stations, etc.). 

What does Bulk Density mean, and why is it important? 

Before going ahead, we’d first like to touch upon exactly what the term ‘bulk density’ means. 

Bulk density is one of the properties of powders, granules, ingredients, flavourings, and any other types of dry bulk solids. It is the weight of the total particles of material divided by the overall occupied volume. The total volume consists of particle volume, internal pore volume, and inter-particle void volume. 

The bulk density would not be described as a natural property of a product as it is able to change its density when the powder is disturbed. When the container filled with the material is shaken, tilted, or stirred, the powder particles may settle closer together, leaving less pore space, resulting in a higher bulk density. 

For the above reason, the bulk density of dry bulk solid will be reported as:

  • Freely settled – Also known as the ‘poured density’, this refers to the when a powder has been freshly poured without any disturbance. 
  • Tapped density – Refers to the bulk density of powder after being compacted through tabbing/vibrating the container.  

How do you calculate the Bulk Density? 

The bulk density (P) is calculated by dividing the weight of a powder (W) by the total volume (V), as detailed in the below diagram: 

Calculating the Bulk Density:

Bulk density (g/cm3) = bulk solid weight (g) / bulk solid volume (cm3)

Formula: P (bulk density) = W (weight) / V (volume)

Bulk density of rock salt = 200g (weight) / 92.17cm3 (volume) = 2.17g/cm3 (bulk density)

If you are a beginner, please see below how to calculate the weight and volume of a product. I will be using 200g of rock salt as example material. Please note that rock salt carries an average density of 2.17g per cubic centimetre. 

Calculating Volume:

Volume (cm3) = bulk solid weight (g) / bulk density (g/cm3)

Formula: V (volume) = W (weight) / P (bulk density)

Volume of rock salt (cm3) = 200g (weight) / 2.17g/cm3 = 92.17cm3 (volume)

Calculating Weight: 

By now, we are already aware that the weight of rock salt is 200g. If this information was unknown, the way to calculate the weight of a powder, or dry bulk solid, would be to multiply the bulk density by the volume of the material. 

Weight (g/kg) = bulk density (g/cm3) x volume (cm3)

Formula: W (weight) = P (density) x V (volume)

Weight of rock salt = 2.17g/cm3 (density) x 92.17cm3 (volume) = 200g (weight)

Trantec’s Solution… 

Trantec now offers a FREE product testing service, introducing our Test Lab located at Renown Works, Clayton-le-Moors. Our test facilities are fully equipped with Metering Feeders and Flexible Screw Conveyors, with machine configurations available for ALL our served industries. 

To request further information as to how Trantec can assist you with material testing, or for an informal chat about your application, get in touch on +44 (0)1282 777566, or alternatively, send us an email by using the contact form located on our Contact Us page. 

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