Low-bulk-density powders with small particle size, low to zero moisture content and low to no cohesiveness can become easily aerated during bulk bag filling leading to poor bulk bag densification. In addition to especially challenging lightweight powders, many other powders, pellets and granules’ material properties make them prone to aeration during filling and difficult to compact. In fact, reducing the amount of air that enters into the material during the filling process is one of the greatest technical challenges in bulk bag filling.
This article will:
- define and discuss the relationship between aeration and densification
- outline the challenges and risks that arise from aeration during the filling process
- discuss bulk bag filling system solutions to increase bagged material density
What is aeration with respect to bulk bag filling and when is bulk bag densification critical?
Due to certain material characteristics such as particle size and shape, some products tend to trap air between particles resulting in reduced bulk density and stability of the material. This can be compounded by aeration during the bulk bag filling process which is the introduction of more air into a dry bulk material being filled in a bulk bag. A good indication of whether a material will benefit from densification during the bulk bag filling process is the difference between its tamped (density of the material once it has been compacted via vibration), and un-tamped bulk density. The use of a sophisticated densification system such as Spiroflow’s CTE Cone Table can result in significant deaeration of the filled bulk bags which has several benefits discussed below.
What happens to filled FIBC bulk bags that have not been deaerated / have poor densification?
When air is trapped or introduced in between powders and other solid particles during the bag filling process, the material can behave more like a liquid than a solid and be extremely unstable during transportation and storage. These bags will be unsafe to stack in storage and shipping, increasing shipping and storage costs, and can be prone to tip over onto an operator, creating a safety risk. Highly-densified, compact bags with flat tops, on the other hand, are safer and easier to handle, stack and store.
A bag filling process that results in aerated, poorly densified bags can result in trailers being shipped under max weight, significantly increasing transportation costs. In addition, if the same weight of material can be achieved in fewer or smaller bags there can be a significant saving in bag costs.
Air (oxygen) in the bag can also pose a health risk for the food and beverage industry – bacteria feeds on oxygen. More oxygen in a bulk bag means that the food product or ingredient will not last as long in storage. While densification can help reduce the amount of air (oxygen) in bulk bags, if this is also a critical factor you could also consider a nitrogen purging fillsystem, which fills the bag with nitrogen prior to and during filling and then seals the bags to minimize product exposure to oxygen.
Bulk Bag Densification Filling System Options
A safe and effective bulk bag filling process aims to deaerate material as close as possible to its tamped bulk density and remove the angle of repose formed by the peak of material when pouring a dry bulk solid for a safer, more stable, flat-top bag.
Vibratory Deaeration Deck / Platform / Table
Most bulk bag filling densification systems use some type of vibration technology on the bulk bag filling platform / table (on which the bag sits while it is is filled) in order to better compact and densify the product in the bag. A programmable vibratory deaeration deck can help to densify the material at timed intervals during the bulk bag filling process and minimizes filling cycle times while improving bag stability.
However, it is important to compare vibratory decks as they are not all designed the same and thus, do not deliver the same vibratory force or rate of densification.
The Spiroflow Cone Table Elite (CTE) High-Density Bulk Bag Filler’s patented cone table densification is ideal for powders, granules or pellets that have a significant difference between their tamped and untamped bulk density or are easily aerated during bag filling. The CTE filler’s unique coned densification table makes direct contact with the bag resulting in maximum vibration energy transfer. The cone shape directs product to the bottom corners of the bag to create a stable foundation and pushes up a column of product every time it comes into contact with the bag, removing the angle of repose. Its assembly consists of a truncated pyramid welded on a frame with two integral electro-mechanical vibrators.
The Spiroflow Cone Table Elite Process
- Build a stable base
2. Transfer maximum energy
3. Stretch the bulk bag
4. Removes the angles of repose
Bag Stretch for Improved Bulk Bag Densification
When using the Spiroflow Cone Table Elite Bulk Bag Filler, a bulk bag still typically spends 50% of the filling cycle hanging from its loops which promotes stretching of the bag. As a bag stretches during filling, volumetric efficiency increases. A stretched and densified bulk bag will not slump and will hold more product. Additionally, due to the unique design of the Cone Table, bag stretching is also improved during the periods of densification.
In other densification methods, bulk bags are not hung by their loops during filling; the introduction of a vibratory filling deck or table means that the bag maintains contact / is sitting on the table through the cycle, preventing the bag from stretching.
Don’t Sacrifice Speed for Best-in-Class Bulk Bag Densification
When it comes to bulk bag densification, many traditional systems will result in a significantly slower fill cycle due to the time it takes the machine to allow material to settle and stabilize. Because of the unique design of the CTE filler, fill rates of more than 40 bags per hour can still be achieved on a semi-automated bag filling line.
No More Unsafe, Unstable Bags
When a bulk bag is properly stretched during filling and the material is deaerated with a flattened angle of repose for a flat bag top, the result is a very safe and stable bag. Learn more about how the cone table on our CTE Bulk Bag Filler can deaerate your material or fill out the contact form below with questions.