When designing a dust collection system, the ductwork is like the highways of the system. They allow the dust to move from the area of production to the dust collector. The dust should move fast enough so it doesn’t fall out while not moving too fast to cause undue wear and pressure drop. What this means is when you are designing your dust collector ductwork, pay attention to the ductwork diameters. When picking the ductwork diameters throughout the system, make sure the velocities correlate with the design velocities shown below.

Low Velocity Causes Dust Build-Up

A velocity that is too low will cause major issues in your ductwork. Dust will fall out and begin to pile up in the ductwork. This will do three (3) things:

• The dust builds up, decreasing the area of the ductwork, until the open area is large enough to get the velocity back up within the range to prevent further dust buildup.
• Dust buildup will increase the weight of the ductwork, and could cause issues with the support of the ductwork.
• If the dust is explosive, the dust buildup creates fuel for an incident and could cause serious problems.

The table below is from the Industrial Ventilation Booklet (5-1) and gives the velocity ranges of various applications and dusts.

Nature of Contaminant	Examples	Design Velocity
Vapor, gases, smoke		Any desired velocity (1000-2000 FPM suggested)
Fumes, metal smokes	Welding	2000 – 2500 fpm
Very fine light dust	Cotton lint, wood flour, litho powder	2500 – 3000 fpm
Dry dusts & powders	Fine rubber dust, Bakelite molding, powder dust, jute lint, cotton dust, shavings (light), soap dust, leather shavings	3000 – 3500 fpm
Average industrial dust	Grinding dust, buffing lint (dry), wool jute dust (shaker waste), coffee beans, shoe dust, granite dust, silica flour, general material handling, brick cutting clay dust, foundry (general), limestone dust, packaging and weighing asbestos dust in textile industries	3500 – 4000 fpm
Heavy dusts	Sawdust (heavy and wet), metal turnings, foundry tumbling barrels and shake-out, sand blast dust, wood blocks, hog waste, brass turnings, cast iron boring dust, lead dust	4000 – 4500 fpm
Heavy or moist dusts	Lead dust with small chips, moist cement dust, buffing line (sticky), quick-lime dust	4500 fpm and up

 

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How Tough Dust Can Affect Your Dust Collection System

Watch this video from the Dust Efficiency Clinic and learn how to deal with all these tough dust issues.

As always the Dust Efficiency Clinic offers its ‘outside the box’ thinking and solutions to your tough dust problems.

 

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To learn more about which dust collector, please contact our experts at 440-543-7400 or visit our website: www.dustcollectorhq.com.

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To improve efficiency and safety, there is no substitute for an on-site inspection by an experienced expert. Click below to start with a free 20-minute phone consultation by clicking the button.

 

 

When protecting vessels from explosions, one of the most common ways is to install explosion vents. The explosion vent is an engineered weak spot in the vessel that fails when the internal pressure reaches a certain point. This failure allows the pressure to be released in a controlled way so that the entire vessel doesn’t explode. The explosion vent needs to be installed so that the venting is away from any equipment, walkways, roads, picnic areas, etc.

Explosion vents are primarily used when the vessels are located outdoors, however they can be used indoors, if certain criteria is met. To install an explosion vent indoors, the vessel has to be located by an exterior wall. The vent would then be ducted through the wall, so in case of an explosion it is directed outdoors. An indoor explosion vent will usually need to be larger than an outdoor explosion vent. This is due to additional combustion of material in the duct and the inertia of the air mass in the ductwork.

The following is an explanation taken from FM Global 7- 76 Section 3.1.8

During the early part of the venting process, unburned dust is ejected into the duct ahead of the flame front from the vessel. When the flame front moves into the duct, dust starts to burn within the duct and generate additional combustion products. Those combustion products expand in ALL directions, thus slowing down or even reversing the flow out of the vessel and the pressure builds up within the vessel.

Inertia of the air within the duct also increases explosion pressure within the protected vessel. When the explosion vent opens and combustion gases first start flowing into the duct, those gases must push all the air out of the duct. During the time required to eject the air, the pressure continues to grow within the vessel because the combustion gases are obstructed from reaching the open atmosphere. In a long duct, that mass of air can delay the venting of the combustion gases enough to significantly increase the pressure in the vessel.

So if you’re installing a vessel indoors and you want to vent it outside, keep it as close to the outside wall as possible.

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Are you in compliance with the 2018 version of NFPA 68?

Simply click the button for direct access to the webinar to learn more about how to these recent changes may require modifications to your system.

 

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To learn more about which dust collector, please contact our experts at 440-543-7400 or visit our website: www.dustcollectorhq.com.

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To improve efficiency and safety, there is no substitute for an on-site inspection by an experienced expert. Click below to start with a free 20-minute phone consultation by clicking the button.

 

 

There are multiple ways to collect dust from the air. The most common are:

• Using filters such as bags and pleated filters
• Using centrifugal motion in a cyclone
• Using water (as in a wet scrubber)

The Important of Particle Size

The particle size of the dust is important in all three of these techniques. Basically the larger the dust particles are the easier it is to capture. And inversely, the smaller the particle is the harder it is to capture, which means it’s more likely to pass through the dust collector and out of the exhaust. Bags and filters build up a dust layer that allows air to pass but prevents particles from passing. Cyclones use centrifugal motion to capture particles, which means the larger and heavier the particle is the faster it spins out of the air-stream. Wet scrubbers use water droplets to increase the particle size of the dust, thereby making them easier to capture.

Particle Size Distribution

What this means is that to figure out how effective your dust collector is, a particle size distribution is required. For example, cyclones have a removal efficiency curve that tells you what percentage of particles will be removed at a certain particle size. This can be used to calculate the total removal efficiency when a particle size distribution is provided. Filter bags and cartridges get high dust removal down to around 1 micron in size; however, if most of your dust is sub-micron in size, they will not provide high removal efficiency. And wet scrubbers can be used to increase particle size, but the design must take into account the particle size.

So one of the first steps to correctly select and design a dust collection system is to run a particle size distribution test. This will allow you to pick the best equipment for your application and to make sure it will provide the removal efficiency you require.

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Are you in compliance with the 2018 version of NFPA 68?

Simply click the button for direct access to the webinar to learn more about how to these recent changes may require modifications to your system.

 

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To learn more about which dust collector, please contact our experts at 440-543-7400 or visit our website: www.dustcollectorhq.com.

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To improve efficiency and safety, there is no substitute for an on-site inspection by an experienced expert. Click below to start with a free 20-minute phone consultation by clicking the button.

 

 

Not only do NFPA regulations require a DHA (Dust Hazard Analysis) to be done on all systems that might have explosive dust, they also require the DHA to be updated every 5 years and whenever the system changes. 

Simple Changes in Documentation

The change can be adding , removing,  or changing equipment or changes in the material going through the system. 

Since a DHA has already been done, the scope of the change is much less.  Using the information in the original DHA, the equipment that is being changed can be analyzed to make sure it complies with NFPA.  This report will then be added to the existing DHA so that a record of change is documented.  Usually the report is considered a mini-DHA or System DHA. 

The mini-DHA or System DHA often can be conducted by a 3^rd party consultant working with the equipment manufacturer.  This usually can be done without a site visit.  Aerodyne offers the Mini-DHA/ System DHA for our cyclone separators.

 

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Are you in compliance with the 2018 version of NFPA 68?

Simply click the button for direct access to the webinar to learn more about how to these recent changes may require modifications to your system.

 

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To learn more about which dust collector, please contact our experts at 440-543-7400 or visit our website: www.dustcollectorhq.com.

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To improve efficiency and safety, there is no substitute for an on-site inspection by an experienced expert. Click below to start with a free 20-minute phone consultation by clicking the button.