Walk into a food processing plant, and you will notice that flour, sugar, starch, spices, milk powder, and other ingredients can become airborne during handling, mixing, grinding, and packing. Other processes, such as baking, roasting, and frying, can generate smoke, oil mist, and fumes.
The extraction system must address all of this while meeting one additional requirement critical in food manufacturing: it must not become a source of contamination itself.
That changes the way the system needs to be designed.
One of the first things we look at when designing an extraction system is where the dust actually comes from.
If dust is being generated at a bag dumping station, for example, the objective should be to capture it there rather than allow it to travel across the production area and then try to remove it from the general room air.
The same applies to:
A properly designed hood or enclosure can make a significant difference to the amount of air the system needs to move.
This is one area where getting the design right at the beginning usually pays off later.
Food plants have strict cleaning routines. The extraction equipment needs to fit into those routines rather than work against them.
Look closely at the construction of the collector, ductwork and hoods. Unnecessary ledges, pockets, rough surfaces and difficult-to-reach corners can collect product dust.
Over time, those areas become difficult to inspect and clean.
Where the application calls for it, smooth surfaces, properly sealed joints and suitable stainless-steel construction can make routine cleaning considerably easier.
The exact material and finish, however, should be selected based on the process and cleaning regime rather than assuming that stainless steel is required everywhere.
It is tempting to compare filters mainly on filtration efficiency.
In a food plant, there is more to consider.
The filter needs to suit the type of dust, operating temperature, cleaning cycle and expected dust loading. Its construction should also be appropriate for the hygiene requirements of the application.
Another practical point is filter replacement.
If changing a filter means opening a heavily contaminated section of the collector directly into the production environment, maintenance itself can become a hygiene concern.
Access should therefore be planned with actual maintenance conditions in mind.
The dust collector may be working perfectly, but if dust is settling inside the ductwork, the system still has a problem.
This can happen when duct velocities are not suitable for the material being transported. Dust can settle in horizontal runs, branches and elbows, gradually reducing the available airflow.
It also means someone eventually has to clean those ducts.
There is a temptation to solve this by simply increasing the duct velocity. That is not always the right answer. Higher velocity means higher pressure drop, more fan power and potentially more noise.
The better approach is to select duct sizes and operating velocities according to the actual material and process.
Many food plants have dry powder processes but use water extensively for cleaning.
That combination needs to be considered during system design.
A collector designed for dry powder may not be suitable for regular washdown. Moisture entering the wrong parts of the system can lead to filter problems, material buildup, corrosion or other maintenance issues.
If washdown is part of the plant’s cleaning procedure, the collector and associated components should be designed with that requirement from the start.
It is much easier to account for this during equipment selection than to modify the system later.
There is another issue that should not be overlooked.
Many common food ingredients can form combustible dust clouds when finely divided and suspended in air. Flour, sugar, starch, powdered milk and several spices are examples.
So, while hygiene is a major concern, the dust collection system also needs to be assessed from a fire and explosion safety perspective.
Depending on the material and process, the design may need to address:
There is no single protection arrangement that works for every food dust application. The material and process conditions need to be assessed first.
Fan selection is often left until the end of a dust collection project.
That can be a mistake.
The fan has to maintain the required airflow against the resistance of the entire system, the hoods, ducts, elbows, filters, dampers and other components.
For many dust collection applications, placing the fan downstream of the dust collector keeps the fan wheel on the clean-air side. This can reduce the amount of dust reaching the wheel and help avoid problems such as buildup and imbalance.
But the final arrangement should always be based on the process and overall system design.
The objective is simple, the fan needs to deliver the required airflow at the actual system pressure, not just a nominal CFM rating.
This is probably the most important point.
A dust collector should not be selected simply because a certain model handles a particular airflow.
Before making that decision, we need to know what the plant is actually doing.
For example:
The answers to these questions determine the practical design of the system.
A dust and fume control system in a food plant should do its job quietly in the background.
It should capture contaminants before they spread, maintain the required airflow, allow filters and components to be serviced without creating unnecessary hygiene problems, and withstand the plant’s cleaning practices.
At the same time, combustible dust hazards, energy consumption and maintenance requirements need to be considered.
The best system is the one that works reliably with the way the plant actually operates.
That is why dust and fume extraction should be designed around the process, hygiene requirements and maintenance routine once the production line is already in place.
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