Jessica Stank details some common micro bin flow issues and explains how to solve them.
Ingredient storage bin construction may not seem like a crucial detail in a processing facility, however, using a bin type that is not appropriate for your ingredients can create flow problems. These flow problems can create other issues that can alter the quality of your batch.
What are bin flow problems?
A bin flow problem can be anything that obstructs the flow of material out of the bin. You can have too much flow or not enough. There can be issues with materials hanging up in the bin, preventing flow. There are several issues that can affect the flow of your bulk powders.
Why should you solve bin flow problems?
Bin flow problems can have several negative effects on your operation. They can cause product inconsistencies, product contamination, loss to waste, and other problems with accuracy and efficiency. The fact of the matter is bin flow problems can affect your bottom line in more ways than one.
How to solve bin flow problems
Dead zones are a common problem. They occur when material moves through the centre of the bin, but the material at the edges of the bin doesn’t move through. When this happens, the same material will stay in the dead zones as other material gets added. As the material sits in the bin, mould and other contaminants can accumulate.
Dead zones usually occur in the bottom corners of the bin. Bins with the proper angle of repose can avoid dead zones. The storage bin can be constructed with an angled bottom, or you can add inserts to create the proper angle.
Clumping and packing
Clumping and packing usually occurs when materials bond together. This might occur when fibrous materials interweave together, or when hygroscopic materials absorb moisture and stick together. If these clumps are strong enough to hold together, they can clog the end of the bin or get caught up in the feeder. As material settles and packs it will build up at the end of the bin and stop material from flowing.
You can solve clumping and packing problems by adding movement to the bin or feeder, such as vibration or agitation. Controlling environmental conditions such as excessive humidity, can also help.
Static can cause light materials to stick to each other or stick to the edges of the bin. This often occurs in especially dry conditions with lighter materials and those with relatively high surface area.
Bin flow problems caused by static can be solved by grounding, anti-static coatings or coverings, or environmental corrections. If a bin is securely grounded, the static charge will dissipate, and won’t cause sticking. Anti-static coatings or coverings on the inside of the bin can also prevent static from building up. Finally, maintaining a stable level of humidity can help to reduce static electricity, for example.
Ratholing and bridging
Akin to the dead zone issue, some bulk powders are prone to hanging up inside the bin, slowing or even stopping the flow of material. Bridging is when material forms a bridge or an arch over the bin discharge point, and ratholing is where the material flow creates a channel or a hole above the outlet. These are similarly problematic, causing material to collect in a way that stops the necessary flow.
These problems can be addressed in a similar manner to the dead zone problem mentioned earlier. Adding aeration or vibration to the bin can help solve these flow problems and keep your difficult bulk powders flowing.
Flushing is another common issue affecting dry mix processing and dry mix processing equipment. Ingredients with a shallow angle of repose are usually more prone to flushing. These materials might be light or heavy, but they generally have uniform and symmetrical particles that don’t interlock. This makes them easily aerated and they will flow very quickly, almost like a liquid. These materials can quickly become unmanageable and flood containers, disrupt weighing devices, spill over the floor, and create dust clouds.
You can help with flushing by designing a bin with an angled feeder or adding a shutoff gate. Both of these will stop the free flow of material, saving on waste, cleaning, and issues with accuracy caused by an inability to stop the flow of the material.
It is important to assess the flowability of your various microingredients and take action if you notice bin flow problems. Once identified, it’s a good idea to solve these issues as soon as you can. The right bin construction from the start can help to prevent bin flow problems. Or, in some cases, you can make changes to correct the problem with an existing micro bin. Whichever way you do it, it is always worthwhile addressing any bulk powder flow issues in your micro bins.
Jessica Stank is with Apec.