Because of their overall effectiveness and reliability, baghouses and cartridge collectors are the most widely used dust collectors in industry today. The filters in these systems are very effective at capturing several types of particulate matter and have the benefit of being able to be regularly cleaned, which keeps overall system efficiency at peak levels.

But, some types of dusts can prove to be problematic for filters. For instance, fibrous dusts, such as those generated in paper or textile processing facilities, can become embedded in filter media and fail to release during cleaning cycles. Wet or sticky dusts that are common in food processing applications or in facilities with high humidity can provide similar challenges with wet or sticky particulate material becoming caked on the filter surfaces. Many types of filter media are also adversely affected by being exposed to moisture because it may cause the filter to degrade rapidly, allowing holes to develop.

With so much of the efficiency of a dust collector relying on the integrity of its filters, any circumstance that might allow the filters to become impeded with wet, sticky, or fibrous material needs to be prevented. If not, the entire system will experience higher pressure drops, lower airflows, decreased efficiency, and possibly lead to unsafe working conditions or violations of air emission permits.

One proven method of keeping filters from becoming impeded by problematic dusts is to install a pre-filter cyclone in the dust collection system. The cyclone is designed to remove larger, heavier dust, while allowing smaller particles to pass through the cyclone and through the filters. In many applications, 80-90% of the particulate matter entering the cyclone is removed, which is a significant reduction in overall system loading. This is especially true when dealing with wet, sticky, or fibrous dust.  With this decreased volume of dust reaching the filters, filter life is extended, with cleaning and replacement needed less frequently. This means reduced maintenance cost while sustaining optimal operating efficiency.

To learn more about pre-filter cyclones, click on the button below.

For dust collection systems to operate as they are designed, baghouse and cartridge collector filters need to be regularly cleaned.  Many systems employ compressed air for this purpose, periodically sending blasts of air through the filters which effectively removes particulate matter from them. The frequency of these cleaning cycles can be controlled by various methods, such as a pressure drop monitor that allows for detection of a filter that is beginning to clog, or with a simple timer. Air flow is typically controlled with the use of a solenoid operated diaphragm valve.

These valves are the critical component in keeping a system operating at peak efficiency. A valve that is stuck in the closed position or does not open when required will not allow the filters to be cleaned, which will result in an overloaded system that could potentially allow higher than expected levels of particulate to be discharged into the atmosphere or lead to premature system failure due to increased loading.  Conversely, a valve that gets stuck in the open position will result in costly compressed air being constantly sent through the filters.

Maintaining the health of these valves is obviously an essential factor in promoting the long term effectiveness of a dust collection system. The simplest way to achieve this is by making sure that the valves are included in a preventive or predictive maintenance program, so that any issues can be addressed before they become major problems. More advanced systems provide continuous monitoring of valve operation, which can alert maintenance personnel to any problems with the valves or the system in general.

To learn more about how Aerodyne can help you keep your dust collection filter cleaning system operating efficiently,  please contact our experts at 440-543-7400 or click on the button below to watch Dust Collection System Maintenance Video.

When designing a dust collection system, one of the most critical design considerations is fire protection. Filter media that are typically used in baghouses, cartridges, or simple filters are most often constructed out of combustible materials. If your dust collection system is being used for an application that is likely to produce sparks, such as cutting, grinding, sanding, or welding, then there is a possibility that a spark could reach the filters and cause an explosion or fire in the system, which could lead to catastrophic damage and potentially loss of life.

One method of preventing sparks from reaching the filters is to incorporate a pre-filter cyclone as a spark arrestor. Air that is contaminated with dust enters the cyclone through an inlet and is then directed towards the walls of the unit. Centrifugal force then takes over, as heavier particles are carried outwards to the wall of the cyclone, spinning along the walls until discharged at the bottom into a hopper. Because cyclones are typically constructed of metal, any spark that touches the cyclone wall will be drained of heat due to thermal conductivity losses. The combination of reducing the speed of the spark and allowing it to lose energy in the cyclone result in an economical and proven method of spark arresting in dust collection systems.

In addition to working as a spark arrestor, a cyclone provides the additional benefit of collecting 80-90% of dust that would otherwise reach the filters.  This results in longer filter life and decreased load on the system which can greatly reduce energy costs.

To learn more about how a cyclone could be utilized in your dust collection application, please contact our experts at 440-543-7400 or click on the button below to get your Cyclone Brochure.

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.

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.

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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.

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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. 

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.

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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.

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.