Dust collection systems require the proper airflow to operate correctly.  Without the correct air flow, dust will not be removed from collection points and the collection equipment (baghouse, cartridge collectors, cyclones, etc.) will not operate with maximum efficiency. However, if too much air is being pulled through the system, a variety of issues might ensue, such as product being lost, removal efficiency lowered, utility usage increased.

Conventional Way to Measure Airflow

The normal way to measure airflow is to insert a pitot tube in the ductwork to measure the air velocity in an airstream, and then calculate the velocity (and airflow).  This is a manual process that requires a trained individual.  It is time consuming and to a certain degree an art, since the velocity in a ductwork changes depending how close to the wall you are.

Effective Way to Measure Airflow

Obviously, you cannot walk next to a piece of equipment or meter and check the velocity through the ductwork.  However, if you have a cyclone dust collector you can.  Cyclone pressure drops are based on the airflow through them.  The more air you send through a cyclone, the higher the pressure drop.  Each cyclone design has its own equation to determine pressure drop based on the airflow.  With this equation, you can estimate the airflow based on the pressure drop in your cyclone.

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The GPC Dust Collector is an efficient way to handle your dust collecting needs. Simply click below for direct access to the GPC spec.

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Exhaust Fans: The Motive Force of a Dust Collection System

In this video, Aerodyne discusses how system changes and fan performance affect your dust collection system.

 

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The key function of a collector is to remove the maximum volume of dust from the airstream.  Additionally, an important part of the process is keeping the removed dust from re-entraining.

Baghouses and Cartridge Collectors

Baghouses and cartridge collectors collect the dust on the filters and during cleaning, the material is knocked loose and falls to the hopper.  How well the material falls to the hopper is dependent on the dust that is being collected, the can velocity (speed of air between the filters) in the baghouse, and the design of the baghouse.  

Basically, if the dust is very light and/or irregular in shape, then it might not easily fall to the hopper, instead it might float (like a leaf).  This could cause it to be re-entrained in the airflow and go back on the filter.  If the airflow is very high then the can velocity could hold up dust after cleaning, thereby causing re-entrainment of the dust.  The design of the unit can affect re-entrainment as well.  Some units have the dust coming in the unit below and at a rather high speed, which can increase dust re-entrainment.  Others will have the dust entering from the side of the filters, thereby being at a much lower velocity and out of the path of falling dust.

Cyclones

Cyclones use centrifugal force to push the particulate dust outward.  Most cyclones also use tapered walls to concentrate the dust as it gets lower in the cyclone until it falls into the hopper, while the clean air leaves the cyclone through the center.  The point where the air stops traveling down the walls and begins to travel up the center is called vortex reversal.  Depending on dust size, concentrations, and cyclone design, dust can be re-entrained by the clean air leaving the cyclone.

Wet Scrubbers

Wet Scrubbers are very good at low re-entrainment.  This is because when the dust meets a droplet, they become one larger particulate and then fall out of the airstream easier.  Most well designed wet scrubbers have a mist elimination section that will further collect droplets before leaving the collector.

 

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5 Signs Your Dust Collection System Needs a Pre-Filter

Watch the video from the Dust Efficiency Clinic discusses how using a pre-filter will optimize your dust collection 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.

 

 

Simple Timers

For many years, pulse-jet baghouses were cleaned by simple timers.  The timers would start the cleaning cycle every so many minutes.  You would be able to change how often your filters are cleaned by changing the time between each cleaning.  This design makes sure that the filters are cleaned regularly, whether they need to be cleaned or not.  The main issue with this is that every time a filter is cleaned, it increases the chances of it failing.  Filters are cleaned by pulsing high pressure air into the filter.  This expands the filter, which causes the top layers of dust to fall off.  But that expansion can also cause holes or rips in the filters.

Pulse-On-Demand Controller

So it would be beneficial to minimize the cleaning of the filters to only when it’s needed.  The pulse-on-demand controller does just this.  It measures the pressure drop across the filters.  When the pressure drop gets over a certain amount, it will begin the cleaning process.  Many of these controllers also have “bag break” technology, which will tell you when one of the filters has a hole.  You will then be able to replace the filters only when they are needed.  Some controllers can even isolate the row where the broken bag is located, so you won’t have to replace all the filters.

Installing a Clean-on-Demand controller, “bag break” technology, and cyclone pre-filters (Check out other Aerodyne blogs for more info) can help you decrease the maintenance on your filters, extend filter life, and lower operating costs (less air usage).

 

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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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Do the rotary valves under your dust collectors cause maintenance headaches?  Are they clogging?  Are you having to drop everything and assign extra labor to fix them?

The disadvantages of Rotary Valve

Most dust collectors are equipped with a motor-driven rotary airlock valve that empties contents from the hoppers. Rotary valves have been used for many years and are probably the most widely used airlock design. However, maintaining rotary valves is difficult and time consuming. These valves run continuously, regardless if dust is present, which leads to wasted electricity. In addition, the valves can wear out rapidly, resulting in costly repairs and replacements.

Best Alternative: Aerodyne Vacu-Valve ^®

A highly cost-effective alternative is Aerodyne’s Vacu-Valve ^®  Trickle Valve System. The Vacu-Valve relies on the negative pressure of the material handling system to hold the duckbill sleeve closed. As the dust or material builds up, the sleeve is forced open, allowing the contents to discharge. Once emptied, the negative pressure then immediately closes the duckbill again. This trickle valve system requires no lubrication, power, or controls. Materials that would normally jam or wear out a rotary airlock valve, the Vacu-Valve handles with ease. There is a variety of duckbill sleeve options designed for specific applications; and the Aerodyne Vacu-Valve ^® is available in an open or closed design, to further accommodate the particular application.

Aerodyne’s Vacu-Valve ^® is the solution! Have a look at this infographic and to learn how the Vacu-valve solves these issues and improves the discharge efficiency of your baghouse, filters and cyclones.

 

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How Do Vacu-Valve Dust Valves Work?

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If you are like many plant engineers who are working within the confines of a limited work space, rest assured that you don’t need to compromise on the efficiency of your industrial dust collection system. A traditional, high-efficiency cyclone is not the best solution for facilities with low ceilings.

Space Limitation

If space limitations prevent you from properly orienting this type of cyclone in an upright position, this will result in a loss of efficiency due to particulate settling on the side of the collector and being carried out with the exhaust gas. Attempting to solve this problem by installing your vertically oriented dust collection cyclone outdoors may encourage condensation that can shorten service life and reduce efficiency.

Horizontal Cyclones

Today, more plant engineers are choosing a horizontal configuration for reliable, high-efficiency dust collection. These options include the Aerodyne GPC Cyclone and counter-cyclonic dust collectors, such as the Aerodyne SplitStream™ Dust Collector.  The SplitStream™ Dust Collector uses a secondary air stream that directs material toward the collection hopper, and may be installed horizontally with virtually no loss of efficiency.

Because this design does not rely on gravity to bring the dust to the hopper like conventional cyclones, its operational efficiency is not affected by horizontal installation. In addition, this type of dust collection system may be suspended from a ceiling, conserving valuable space on the manufacturing floor.

The SplitStream™ Dust Collector the ability to increase/decrease process temperature while collecting dust. The unique counter cyclonic design element of the SplitStream™ Dust Collector ensures that a minimal amount of particulate comes in contact with the interior walls. This eliminates excessive wear and enables abrasive particulate collection.

 

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How Do Horizontal Dust Collectors Work?

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As maintenance staffs become smaller and have less time to do preventative maintenance, technology needs to step in and help. 

Level Switches

That is where level switches in dust collector hoppers fit in.  An airlock works by allowing dust from the dust collector to leave the vessel while preventing air from leaking in or out of the system.  Some airlocks operate by emptying the hopper as soon as dust falls and some require a buildup above them to help seal the valve and provide motive force. 

The main thing is, that dust often times will not constantly be falling through the valve.  This means that walking next to a vessel won’t always tell you if the airlock is operating correctly. 

Installing a level switch in the hopper will help.  The level switch measures the amount of material in the hopper and if too much is in the hopper it will provide a signal (alarm).  This will tell maintenance that the airlock is not operating correctly and it needs to be investigated.  Depending on the system’s controls, the alarm can be a local alarm (light and/or horn) or feed into the central computer.

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Dust collection systems can range from being fairly simple to extremely complex. 

It’s important to know that you have the proper system for your application. Some questions always come up when looking at dust collection systems.

To make life easier, we have put together some common questions we get asked along with answers and explanations. Have a look.

Volume 1:  

Volume 2:

 

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Heavy dust loading in the dust collector leads to high maintenance dust collectors.  Since most dust collectors are fabric filters (baghouse, cartridge collectors, shakers, etc.), heavy dust loading will cause/require high frequency of cleaning of the filters.  Most filters are cleaned by injecting high pressure air into the clean side, causing the filters to expand a bit.  This causes dust to fall off the filters.  Filters wear out due to the frequent expanding and contracting.  So the more often you have to clean a filter, the faster the filters will wear out.

Pleated Filters

This is made even worse if the filters are pleated.  Pleated filters have valleys and ridges which increase the surface area available for air to diffuse through the filter.  However, high dust loading can cause the pleated filter valleys to fill up and not properly clean during a cleaning cycle.  This will severely restrict the surface area available for airflow, which will lead to higher velocities through the filters.  A higher velocity increases the chances of dust getting through the filters.  This can cause holes to develop in the filter.  It can also cause dust to plug a pathway through the filter, thereby further restricting airflow.  It can also cause a decrease in removal efficiency.

So if you have high dust loading in your dust collector, it might be beneficial to install a pre-filter to increase filter life and make maintenance much less of a hassle.

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Pre-filtering may reduce operating and maintenance costs by extending bag or filter life and improving removal efficiencies. This video discusses five warning signs that your dust collection system needs a pre-filter.

If you prefer this valuable information in white paper form, get our whitepaper, Top 5 Reasons to Use a Cyclone as a Pre-filter.

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To help answer this question, NFPA has released NFPA-652 and 654. A combustible dust is defined as a finely divided combustible particulate solid that presents a flash fire or explosion hazard when suspended in air or the process-specific oxidizing medium over a range of concentrations. Basically, what this means is when the dust is in the air and its concentration is enough to cause a flash fire or propagate a deflagration or explosion if exposed to a spark or heat source, then it’s considered combustible.

Combustible Dust Testing

Unless you know for sure that your dust isn’t combustible, you should send the dust sample to a lab for testing. The lab will provide one of three responses – no reaction, combustible but not propagating, or propagating. 

Usually the lab will initially do a Go/ No-Go test. If the dust doesn’t exhibit combustion, the testing will stop. If it does exhibit combustion, they will then do further tests and provide explosion properties ( Kst and Pmax) of the dust. The Kst tells you how quickly the explosion will propagate, while Pmax tells you the power behind the event.

 

Common Knowledge about Combustible Dust

1. A combustible dust mixed with non-combustible dust may or may not pass the go / no-go test; therefore, if you have both in a mixture, get a test.
2. Material that may not burn can still be combustible as a dust, unless you know for sure, getting a test is the safe bet.
3. If you have made a process change that changes the composition, relative concentrations, etc. of the dust, then the combustibility of the dust may have changed and a new test should be done.
4. If you have combustible dust in your facility, then a hazard analysis of the area must be done every five years.

 

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Dust Collector FAQ Volume 1

To make life easier, we have put together some common questions we get asked along with answers and explanations. Have a look.

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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.

As regulations to minimize dust emissions became more stringent, the reliance on filter media became more prevalent.  This means baghouses and cartridge collectors have become the most common dust collectors around. 

Dust Collector Filter

The filters allow air to pass, while dust is captured on the filter surface area.  A filter cake of dust forms, allowing the highest removal efficiency of the filters.  Periodically, the filters will be cleaned to drop dust off the filters/ filter cake, allowing more air through the filters.  The higher the concentration of dust, the faster the filters will require cleaning to keep the pressure drop down.  Every time the filters are cleaned the fabric of the filter wears a bit.  So, if you can minimize the cleaning, then the filters will last longer.

Cyclone Pre-Filter and Dust Collector Filter

Cyclone pre-filters capture a high percentage of the dust before it even gets to the filters; therefore, allowing less clean cycles on the filter media.  Cyclones use centrifugal force to capture dust and droplets and remove them from the airstream.  Unlike filters, the higher the concentration of dust in the airstream, the better the cyclone performs.  Cyclones provide very good removal of larger dust particles, often getting removal efficiencies as high a 99% for 30-40 micron dust particles.  But they do remove lower amounts of smaller particles.  So the cyclone is a perfect companion for dust collection filters as they will remove most of the larger particulate.  This can often be 80-90% of the total dust loading of a system by weight.  The cyclone pre-filter then allows the filters to deal with only the fine dust that gets past the cyclone.  The lower loading of dust on the filters allows the filters to last longer and conserve energy as the cleaning cycle isn’t used as much.

Compact Cyclones

Compact cyclones, such as the Aerodyne GPC, allow cyclone pre-filters to be used in existing facilities where larger (taller) cyclones won’t fit.  The Aerodyne horizontal GPC cyclone provides one of the most compact designs - often ⅓ the height of traditional cyclones.  This can often allow the cyclone to be installed inside or in smaller areas of an existing system.  Traditional cyclones typically require outdoor installation, unless the facility has high ceiling.

So if your filter dust collection system is experiencing operational issues, look into compact cyclone pre-filters as a possible solution before you decide to scrap your current unit and install a new one.

 

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5 Signs Your Dust Collection System Needs a Pre-Filter

Watch the video from the Dust Efficiency Clinic discusses how using a pre-filter will optimize your dust collection 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.