Dust collection systems pick up dust generated by process equipment and move it away for disposal or to be recycled. They use hoods to gather the air around the dust generation equipment. The dusty air is then sent to the dust collection equipment through ductwork. The dust collection equipment often consists of a pre-filter to help collect the dust followed by the main dust collector. An exhaust fan is often at the end and it powers the system by pulling the air through each of these components.

Dust Collector System with Ductwork

The first stage of the dust collection system are the collection hoods. Well-designed hoods are engineered so the dust generated by the equipment can be collected with the least amount of airflow possible. Once the dust leaves the pickup hoods, it travels through ductwork until it reaches the dust collector(s). In a well-designed dust collector system, the ductwork will be sized so that the airflow has enough velocity to keep the dust from falling out in the ductwork. Usually, the airflow needs to be between 4000 and 5500 FPM to keep dust from falling out. So, if the airflow in the system changes from its designed conditions the velocity in the ductwork will also change.

When The Airflow Is Too High

With too high of an airflow, the air velocity in the ductwork will increase. This will cause increased pressure drop in the system but it will also increase the erosion of the ductwork walls by particles making contact with the walls. Increased erosion of the duct walls will cause holes to develop, which will further affect the airflow in the system

When The Airflow Is Too Low

With too low of an airflow, the air velocity in the ductwork will decrease and could allow dust to begin dropping out and building up within the ductwork. This can cause the ductwork to become heavy and fall. If the dust is explosive, this dust can cause or feed an explosion and is a safety risk. If enough dust piles up, it could end up plugging the ductwork, thereby cutting off airflow through the ductwork.

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Dust collection systems consist of four major items.  All of them are important and can cause a dust collection system to underperform.  The major items are the exhaust fan, dust collector, ductwork, and hoods/pickup points.   While the exhaust fan provides the motive power to collect the dusty air, its performance is affected by each of the components.  This means that if one of the other components isn’t operating as designed, the whole system will be affected.  Ductwork is usually by far the largest component and often the most overlooked.  Depending on the size of your system, the ductwork can span hundreds of feet and have dozens of side streams.  The ductwork is like railroad tracks, it moves the dusty air from one place to another.

Often times, additional lines will be added to a dust collector system after installation.  Without proper evaluation of the system, this could negatively affect the performance of the whole system.  This means that just because the dust collector system was operating correctly before, it might not after an additional pickup point or hood is added.  What happens is that when you add additional pickup points, you change the balancing of the system.  This could change the airflow to each and every hood and pickup point in the system, so while the system was originally adequately venting an area, it might not after a change.

A few things can be done to address this, such as changing fan speed, adding dampers, modifying ductwork, etc.  The main thing you need to keep in mind is that if you slow the airflow through ductwork too much, you begin to build up dust within the line.  This will further restrict your airflow and become a fire / explosion hazard.

So when you are looking at changing your dust collector system, review the system parameters or hire someone to review so that you do not cause additional issues.

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If you are having operational issues on your dust collection system, contact Aerodyne at 440-543-7400 or dc@dustcollectorhq.com.