Dust Collection Myths Debunked

By Oneida Air Systems
www.oneida-air.com

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There are many misconceptions about the science of dust collection. In this article, we debunk 6 of the biggest dust collection myths in the industry!

MYTH: The only harmful dust particles are the ones you can see – the smaller, microscopic dust particles are too tiny to have effects on your health.

False. Any and all dust particles are harmful to your health, regardless of size. While a single particle may not have an effect on your health, tools do not generate a single dust particle. Over time millions of particles filling your lungs will certainly cause health issues, just as larger visible dust particles would.

Industrial hygienists are most concerned about particles in the PM 10 range (between 10 and one micron in size). These particles can penetrate the deepest recesses of the lungs and are very difficult for the body to expunge, contributing to emphysema and other respiratory disorders.

It is essential to filter 99.9% of small particles. Collecting dust at the source (where it is emitted) prevents the dust from escaping to the environment or shop air to be inhaled. For optimal protection, wear a HEPA-level-effective dust mask and invest in a cyclonic dust collector with HEPA-grade filter media capable of filtering particles down to 0.3 microns in size.

MYTH: Dust collectors work better at higher elevations where the air is thinner.

False. At higher altitudes the air is thinner (less dense). Due to this lack of air density, the dust collector does not move as much air as if it was at sea level. As your shop is higher in elevation, the effect increases. While the fan motor may spin more easily thanks to the lower air pressures at higher elevations, it will have to do far more work to move an equivalent volume of air. The effective CFM of any dust collector is lowered by 25% when above elevations of 4000 ft above sea level. In one example, a measurement taken at an elevation of 8500 ft above sea level (that of Estes Park, Colorado) lowered the effective CFM of a 2HP dust collector by over 35%. Therefore, shop owners at higher elevations will need a more powerful dust collector to accommodate the lower air density.

If you’re searching for a dust collector for a high altitude location, you may want to consider one of our SMART Boost systems – they can adjust for differences in air density to optimize static pressure and CFM in high-altitude locations by spinning the fan wheel faster.

Myth: A dust collector’s CFM rating is what you get at each tool.

Usually False. Dust collector manufacturers publish CFM (airflow) ratings obtained through a variety of different testing conditions. It’s common for manufacturers to publish “free fan” CFM ratings, which are measured without connecting flex hose or ductwork to the collector. This leads to inflated ratings that are not based on real-world working conditions.

When these components are connected, they increase the static resistance the dust collector must overcome to move air. This results in reduced CFM/airflow that the dust collector is able to pull through the dust port back to the dust collector. The smaller the diameter of the pipe, the less CFM will be delivered at the end of the duct run. Ultimately, the CFM you get at each tool is dependent on the amount of resistance against airflow (measured in inches of static pressure loss) that exists in your setup from such components. With traditional fixed speed collectors, this loss is more significant. Dust collectors with static pressure ratings of more than 20” of static pressure to help reduce the losses of CFM caused by ducting. When looking at dust collectors, keep an eye out for specifications that are measured in real world conditions (such as X feet of pipe/flex hose at Y diameter) to get the best idea of how the collector will actually perform at a tool.

Myth: Cyclone separators work by centrifugal force alone.

False. Cyclones use both centrifugal force and gravity to separate dust. The dust laden air enters the cyclone and, using centrifugal force, the particles are pushed to the outer wall of the cyclone and slow down as they spin around the perimeter. Then, gravity pulls them down into the container as they drop out of the airstream, so that only the smallest particles and air are pulled up and go through the fan and into the filter. This is why it is important to vertically mount your cyclone; a horizontal orientation prevents gravity from helping with separation. Our signature cyclone shape is engineered for the optimal ratio of diameter and height, providing a class-leading 99% separation rate – even for the smallest dust particles.

Myth: More horsepower equals more suction power.

False. There are many factors that determine the suction power of your dust collection system and the motor’s horsepower is only a small part of that. The horsepower rating simply means how much work it can do – i.e. how big of an impeller can it spin (Torque) and how fast can it spin (RPM). While dust collectors with higher horsepower rating may have higher theoretical airflow ratings, the shape, design, and layout of the overall system will play a much bigger factor in determining your system’s suction power.

It’s important to remember that while it may not be visible, air is still a fluid. It wants to move along the path of least resistance, it’s sensitive to temperature, it can be compressed (but doesn’t like to be), etc. Not only that, but dust-laden air requires that a certain air velocity be maintained, lest the dust fall out of the air and settle within the ducting.

If your dust collection system is performing poorly and leaving dust on the tool, upgrading the horsepower alone will not remedy the issue – and it may be that you do not need to upgrade the horsepower at all! Start by examining for:

Air Leaks: Locations where the air takes the easy road out of the system instead of working for you.
Hairpin Turns: Sharp 90 degree turns and splits don’t allow for the air to move gradually and instead create extra pressure, slowing down the air speed overall.
Rough Terrain: Corrugated piping and hose can create air resistance up to 5x greater per foot compared to smooth-wall ducting.
Clogged Filters: Dust collectors work by moving air but if the filter is all backed up then there’s nowhere for the air to move to. Routine maintenance is important!

Myth: Filters work better when they’re clogged with dust.

False. Traditional style filter medias such as nanofiber, cellulose, spunbond, etc. reach peak particle efficiency after they have been “seasoned” for a period of time to develop a layer of very fine dust (known as filter cake) over the media. Seasoning the filter leads to some suction loss but increases the ability of the media to filter out fine dust. However, a clogged filter does not get better. It actually makes the overall dust collection worse by restricting the airflow needed to capture dust at the tool.

In contrast, HEPA-Grade Media Cartridge Filters (like the ones sold by Oneida Air Systems) do not require seasoning. HEPA media works at peak filtering efficiency right out of the box and return to that level of filtration after every cleaning. If the filter is allowed to clog up, the dust collection system will experience a significant drop in suction, and may accumulate thick layers of resinous dust that stick to the media and become more difficult to remove over time. Frequent cleanings improve air quality, keep ducts clear, optimize airflow, and extend the filter’s lifespan.