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Dust Collection and Valves Blog

    The Pulse-On-Demand Controller – the Wave of the Future

    Posted by Tom Hobson on Aug 29, 2018 11:30:00 AM

    While Aerodyne doesn’t manufacture baghouses or their controllers, it seems like we’re always working with them. However, as we like to say, the pulse-on-demand controller is the wave of the future.  Sure, the old baghouse controller is still functional, but the rising cost of energy and the growing concern about waste make the pulse-on-demand controller the ideal choice.

    The pulse-on-demand controller measures the pressure drop across the filters.  When the pressure drop gets above a certain amount (as set by the user) the cleaning system will automatically start up.  It will continue to clean until the pressure drop get below a certain amount (again set by the user).  This process then repeats itself throughout operation.

    This means that you won’t have to clean your filters unless you need them, which makes everyone’s life easier, except maybe for the bag manufacturer!  Less cleaning also means that your filters will last longer, and you’ll save extra money otherwise spent using more compressed air.

    To increase the time between required cleanings, you can also add a cyclone pre-filter before the baghouse section to decrease the loading on the baghouse, so that it takes longer for the filter’s pressure drop to increase. This way, your bags will last longer while your compressor works less, saving your facility money.

    Learn more about pre-filter.

    Download Whitepaper

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    Topics: dust collector, cartridge collector, Dust Collection System Evaluation Guide, horizontal cyclone, traditional cyclone, pre-filter

    The Power of Variable Frequency Drives (VFDs) in Dust Collectors

    Posted by Tom Hobson on Aug 28, 2018 9:15:13 AM

    Over the past few years, the relative cost of VFDs comparative to motor starters has dropped, making the VFD an attractive replacement.  When used in a dust collector, VFDs provide many more benefits than do motor starters.

    First, the VFD allows you to soft-start a system. When you start up a dust collection system in very cold or arctic weather, if you immediately start it at full speed, the fan could draw very high power. However, when the process gets up to steady state (i.e. a higher operating temperature than ambient air), the power level will then go down significantly.  The VFD allows you to avoid this power dip by slowly ramping up the fan speed as the temperature increases, so you won’t have to oversize your motor to compensate for startup.

    The main benefit of the VFD, however, is that it allows you to fine-tune your dust collection system to handle real-world conditions and requirements.  It’s easy to change the fan’s operating speed, thereby increasing its speed when more airflow is required, or to decrease it when a higher speed is unnecessary. For example, if you’re sizing a dust collection system and plan on opening up another line or expansion, you can install a larger fan and operate the system at a lower speed, increasing fan speed whenever practical.  The VFD also allows you the flexibility to adjust the entire system if your initial design flow was too light or heavy.

    An ideal instance showing the benefits of a VFD is seen in a facility which was transporting scrap material pneumatically.  However, the facility’s pneumatic system design had a higher static loss than the actual losses after installation. This caused the fan to have a much higher airflow, allowing it to transport large heavy scrap that damaged the fan and the other equipment downstream.  By contrast, installing a VFD on the fan would allow them to cut back on the airflow, thereby preventing the larger scrap from entering the system in the first place.

    Finally, the VFD also allows you to adjust your dust collection system based on unforeseen changes that happen over its lifetime.  It’s a truism that all systems requirements can change over time: equipment is constantly changed, modified, added and removed.  Naturally, all this alteration likewise affects the dust collection system.  However, you can mitigate this by using a VFD which allows you greater flexibility in adapting to these changes.

    The next time you’re designing and/or installing a dust collection system, save yourself a possible headache in future by installing a VFD.

    Find out more. Dust Efficiency Clinic


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    Topics: dust collector, cartridge collector, horizontal cyclone, traditional cyclone, variable frequency drives

    Benefits of a Horizontal Cyclone: A Short and Sweet Space-Saver

    Posted by Tom Hobson on Jun 29, 2018 2:15:00 PM

    Almost everyone in this industry is familiar with using a cyclone for dust collection. Cyclones work great as pre-filters, decreasing loading and minimizing contamination before a baghouse or cartridge collector. However, many times you don’t have the head room to install them.  Or you have an existing dust collector and no room to install a cyclone pre-filter. 

    Traditional cyclones are tall, vertically oriented structures. Indoors, they take up a lot of room. If they are outdoors, there can be maintenance issues.  There are even installations where a hole in the roof is required to install the cyclone. That is obviously very expensive.

    All of these challenges can be overcome by selecting a horizontal cyclone.  Because they are horizontal, they are usually ⅓ the height of a traditional cyclone.  This means they can fit in low headroom areas.  The other benefit is that both the inlet and outlet of the cyclone are on the horizontal plane.  That means the cyclone can replace a 90° turn of ductwork (vertical or horizontal), further saving cost

    What’s more, some types of horizontal cyclones have a design that increases the efficiency of dust collection, so that a smaller cyclone can match or exceed the efficiency of the tall cyclone. This saves space and cost, because material costs make up a significant portion of the cost of a cyclone

    The short version of the story is this. The next time you are thinking about replacing your baghouse or cartridge collector because you can’t install a cyclone pre-filter, investigate a horizontal cyclone.

     

    Find out more.  Horizontal Cyclone

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    Topics: dust collector, cartridge collector, Dust Collection System Evaluation Guide, pressure drop, horizontal cyclone, traditional cyclone

    The Hidden Dangers of Overfilled Hoppers in Dust Collection System

    Posted by Tom Hobson on Jun 29, 2018 8:25:10 AM

    All dust collectors include a hopper that collects the captured dust.  These hoppers are not designed for storage of the dust, however.  They are there for the dust to collect until it passes out of the dust collector through an airlock, such as a rotary valve, double-dump valve, trickle valve, etc.  Adequate discharge intervals are important.   If enough dust builds up in the hopper, then the dust will get re-entrained into the air.  This could cause a few issues. 

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    Topics: dust collector, cartridge collector, Dust Collection System Evaluation Guide, hoppers, airlock, overfilled hoppers, wear and tear

    Five Causes That Lead to “Leakage” in Baghouse Filters

    Posted by Tom Hobson on May 24, 2018 2:57:49 PM

    Baghouse filters are great for dust collection; however, if they develop a hole, then there is a clear path for the dust to take through the filter.  Over time, the hole will increase in size, allowing more and more dust through.  Filters with holes decrease the removal efficiency of the dust collection system and could violate your air permit.

    The filters in a baghouse are the primary dust collecting component.  The filters build up an initial layer of dust, preventing dust from penetrating the filter while allowing air to pass through.  As the dust layer increases in thickness, it is harder for air to pass through.  This is measured by an increasing pressure drop.  Since most dust collection systems don’t use Variable Frequency Drives (VFDs) and airflow transmitters to control the airflow, the airflow through the system will decrease as the pressure drop across the bags increases.  Most baghouses use compressed air blown down the bag, to expand the bag off its cage to jar the most recent layers of dust off the filter. Other baghouses use a shaking cycle to remove the top layer of dust.

    Over time, the constant expanding and contracting of the bag during the cleaning process could cause a hole to develop in the bag.  There are a few different ways for the bag filter to develop holes:

    1. Gradual expansion of natural gaps in the filter during the cleaning process.
    2. The bag being caught and ripped on the metal cage during the cleaning process.
    3. High temperature causing localized failure of the filter.
    4. Abrasive dust gradually wearing out filter materials.
    5. High velocity of the air gradually wearing out the filters.

    There are bag break sensors available on the market that will let you know when they detect a bag break.  Often, this is done by measuring the amount of dust particles after the baghouse and when the concentration suddenly jumps, an alarm is set.  Certain baghouse controllers will measure the compressed air used during the cleaning process.  From this, they can tell which row of bags have a hole so you can replace only a row of bags instead of all the bags in the baghouse.

    A yearly maintenance inspection of the baghouse will help you avoid operational issues that could develop throughout the year.  This can prevent you from getting a fine or having to shut down the system in an emergency.

    Find out more.  Dust Efficiency Clinic


     


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    Topics: dust collector, cartridge collector, air leakage, Dust Collection System Evaluation Guide, pressure drop, pressure drop causes, air flow, Filter leakage

    Five Major Air Leakage Issues That Cause Problems to Your Dust Collection System

    Posted by Tom Hobson on May 17, 2018 1:40:53 PM

    When selecting the airlock for your dust collector, it is important to think about air leakage.  A little air leakage through the airlock isn’t a usually a big deal with many baghouse applications, but air leakage can cause major issues with some applications.  So it is important that you identify if your system will have issues with air leakage and then select the proper airlock valve.

    Some dust collection system issues that could come with air leakage include:

    1. Decrease airflow at pickup points – If an airlock leaks too much air into a system, it could decrease the airflow at the pickup point, thereby causing less dust to be collected.
    2. Blowing dust out of the airlock – If too much air leaks out of the system through the airlock, the collected dust might be blown out of the airlock, causing the collected dust scatter on the ground around the dust collector.
    3. Dust that reacts with water – Humidity from outside the process can cause dust to become sticky, bridge, or even explosive in special circumstances.
    4. Systems that are oxygen deficient for reaction or explosive prevention – Outside air can introduce oxygen to the system which could feed a reaction or move the process into the explosive zone.
    5. Systems that have a high pressure or low vacuum - Leaking airlocks can bleed pressure or allow outside air into a high vacuum, requiring the pressure control system to work harder.

    If you have an issue like this, you might want to look at your airlock.  While rotary valves are the industry standard, and currently the only valve approved for explosion isolation in the NFPA, they do constantly leak air into or out of the system.  The reason is the rotor has a small clearance between it and the valves housing.  This allows a path for air to travel.  So while this path is small you will always get some leakage into or out of the system with a rotary valve.

    Other valves that will minimize leakage include

    • Double dump / knife valve – This valve uses what is essentially two valves in series. And while one of the valves is open, the other is closed.  This prevents air from leaking in or out since there is no direct opening through the valve.  The major drawback of this valve is that the capacity of the valve is severely restricted.  A rotary valve will have a higher flowrate through the same diameter valve.  The other advantages include that these are better with chunky or fibrous materials.
    • Trickle valve – A trickle valve (like the Vacu-Valve®) uses the vacuum of the system to seal a sleeve. This prevents air from leaking into the system.  Gravity will then pull the dust through the sleeve once enough material is built up above the valve.  This valve can be used if: the system has negative pressure; the dust is free-flowing dust and won’t bridge; and the dust is not explosive.  The advantages of a trickle valve include no moving parts, low cost, low maintenance, and no power is needed.

    In summary, when designing your dust collection system, don’t just pick a rotary valve, make sure that air leakage will not cause an issue.  And if it does, then look for an alternative that will minimize the leak leakage.

    Evaluate your current dust collection system for operational efficiency. Simply click the button to get direct access to our evaluation guide.

    Download Guide

     


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    Topics: dust collector, cartridge collector, air leakage, Dust Collection System Evaluation Guide, pressure drop, pressure drop causes, air flow

    Cleaning Baghouse Filter Could Be A Bad Thing?

    Posted by Tom Hobson on Apr 26, 2018 9:15:00 AM

    While not cleaning your baghouse filter is bad, cleaning your filters too much isn’t a very good idea either.  If you don’t clean your filters enough, dust will build up on them faster and they will plug up faster; however, cleaning them too much can cause issues too.

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    Topics: dust collector, cartridge collector, cleaning baghouse filter, baghouse filter

    Why Are Airlocks Needed Under Dust Collectors?

    Posted by Tom Hobson on Apr 19, 2018 9:05:32 AM

    Airlocks are very important for proper dust collector operation.  The airlock prevents air from entering or exiting the bottom of the dust collector.  The opening at the bottom of the dust collector is meant for discharging the dust from the system.  When air is entering or leaving from this area, it will cause issues. 

    If the dust collector is under negative pressure (fan after the dust collector), then air will leak into the system from the opening.  This will re-entrain dust that has already been removed from the process air.  This will also decrease the air being captured at the pickup points (hoods), thereby making the dust collection system less effective.

    If the dust collector is under positive pressure (fan before the dust collector), then air will blow out of the opening.  This will cause the dust being captured to fly out of the dust collector and scatter on the floor and re-enter the facility air.  Installing an airlock will prevent the above conditions.

    Some applications have limitations on humidity, temperature, oxygen levels, etc.  If an airlock is not installed, there will be no way to control the conditions, as the outside environment will leak into the system.

    Evaluate your current dust collection system for operational efficiency. Simply click the button to get direct access to our evaluation guide.

    Download Guide

     


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    Topics: dust collector, cartridge collector, Dust Collection System Evaluation Guide, pressure drop, pressure drop causes

    It is the Spring Cleaning Time for your Dust Collector!

    Posted by Tom Hobson on Mar 27, 2018 8:26:11 AM

    Now that winter is winding down, it’s time to get ready for summer!  That means planning vacation with the family!  Cleaning up the yard!  Send the kids outside so they burn off all that energy they accumulated over the winter! 

    It’s also a good time to check your dust collector. Now that you will be able to open the doors to your facility without freezing the workers, dust that has accumulated over winter will be dislodged.  And while you shouldn’t have dust layers on your equipment (NFPA specs and OSHA frowns upon it), we all know that it happens at times. 

    So now is the time to check your dust collector!

    Check for the following and if you have any of them, get your dust collector a checkup.

    • High pressure drop
    • Dusts exhaust
    • Dust piles by the pickups
    • Noise from the fan
    • Damaged or inoperative airlock

    Download Aerodyne DC Evaluation Guide.

    Download Guide


     

     

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    Topics: dust collector, cartridge collector, Dust Collection System Evaluation Guide, dust collection system checkups

    What Causes Pressure Drop in Baghouses and Cartridge Collectors?

    Posted by Tom Hobson on Mar 23, 2018 10:07:46 AM

    Baghouses and cartridge collectors are usually designed to handle a maximum of 6” Water Column (W.C.) of pressure drop.  This means that when the baghouse pressure drop is 6” W.C., the airflow through the system is enough for proper operation.  When the pressure drop across the bags is greater than 6” W.C., the airflow through the system is less than it should be. The baghouse uses a control system to keep the pressure drop through the system less than 6” W.C.  Most baghouses use compressed air to clean the bags, but shaking and sonic cleaners are also used. 

    The two main controllers used are timers and clean on demand.  A timer is a simple controller which will turn on the cleaning cycle at a set time, such as every 5 minutes.  The timer can be changed, and a manual clean is usually available.  While the initial cost of this timer is less, it can end up wasting a lot of money if the timer is cleaning more often than required.  If the timer isn’t cleaning enough, then the dust collector is not operating at its optimal.  The other controller is clean on demand.  This controller uses a differential pressure transmitter to monitor the pressure drop across the bag.  When the pressure drop gets to a certain point, it will begin cleaning the bags until the pressure drop is lowered to a certain point.  This can save you a lot of money by minimizing the compressed air required.  However, if your bags are plugged, the cleaning can be continuous as the pressure drop will never fall below the cutoff point.

    Filters will have high pressure drops due to a variety of reasons or even a combination of reasons working together.  These include heavy dust loading, wet or humid conditions, worn diffusers, humid compressed air, improper cleaning, and old filters.

    • Heavy dust loading will plug filters faster than lower dust loadings. The faster dust covers the filters, the more the cleaning is required.  However, every cleaning doesn’t get 100% removal so over time the dust layer will get thicker and thicker; thereby, increasing the pressure drop.
    • Wet or humid dust can cause pre-mature plugging. This is because when the dust gets wet it can form a mud.  This could prevent air from passing through, thereby increasing the pressure drop.  If the dust is hygroscopic and/or if the filter is pleated, the filter can plug up even faster.
    • Dirty air entering a baghouse usually goes through a diverter, which directs the air evenly to each bag. Many times the diverter is some metal shape.  Over time, abrasive dust will wear away the diffuser changing the airflow.  This usually means some filters will get heavier dust loadings than others.  The filters getting the heavier dust loading will then plug faster, increasing the pressure drop through the system.
    • Humid compressed air can cause major issues with certain dusts. If the dust is hygroscopic, then adding moisture to the system can cause problems.  Some dust becomes a mud while others form a concrete like substance.  Since the humidity is coming from the cleaning air, the humidity is meeting the dust in the filter holes, thereby plugging them up faster, and making it even harder for them to be cleaned.
    • If the cleaning system isn’t operating properly, the bags will not clean effectively. This could be anything from stuck/broken air valves, misaligned venturi, bags stuck on cages, or too low compressed air.  Since the bags are cleaned by an expansion of the bag and losing the dust layer, if air isn’t delivered correctly, the bag may not fully inflate and not fully clean.  So any obstruction or barrier to full inflation would cause premature plugging.
    • As mentioned above, over time all filters will plug up.

    The best way to keep your dust collector working properly is to have a professional maintenance crew inspect and maintain your dust collectors.  Not only does this open your maintenance staff for other work, it allows them to use their experience to keep your baghouse operating at peak performance.

     

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    Topics: dust collector, cartridge collector, Dust Collection System Evaluation Guide, pressure drop, pressure drop causes

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