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.

 

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.

 

 

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. 

Dust collections systems are complex entities.  They consist of multiple pieces of equipment, and if one of them is not operating correctly, could cause the failure of the whole system.  All dust collection systems consist of the dust collector (cyclone, baghouse, cartridge collector, wet scrubber), exhaust fan, ductwork and hood/pickup points.  Each of these is extremely important to the operation of the system. 

If the dust collector isn’t properly maintained, the system will gradually lose efficiency over time, until it isn’t performing to the optimum.  Often, this isn’t even noticed by the operators because it gradually changes.  However, a new worker or outside observer will notice it, since they will see dust building up around the pickup points.  This gradual efficiency loss can be caused by dust collector issues, dust buildup in the ductwork, or fan issues.  It could also be caused by modifications of the dust collector system after it was installed.

One way to monitor a dust collector system is with pressure drop across the dust collector.  This is a very good way to see if the dust collector is plugging up.  The one issue with this is that if you aren’t constantly monitoring the system, the dust collector could plug up, and a decrease in airflow through it could provide the same pressure drop.  Regular inspections of the dust collector and ductwork should be scheduled to make sure issues are not developing.

Another great way to check your system is to measure the airflow at various parts of your system.  These measurements will tell you if the system is operating correctly.  The reason you want to take multiple measurements is that when you have more than one pickup point, air will travel the path of least resistance.  This means that if one of your pickup points is plugged up, more airflow might be coming from the other pickup points, and the total airflow at the dust collector might be nearly the design amount.  However, the plugged up pickup point isn’t operating as designed.

Often times, dust collection systems are designed for a specific function, then over time, it is changed by either adding or removing pickup points.  This could seriously affect the performance of a dust collector system.  If the changes are made without running calculations, pickup point airflows could change, which could allow dust accumulation around certain areas.

If you have modified your dust collection system in the past, it is a good idea to run some calculations on your system, to make sure it is operating correctly.  If you are planning on modifying your system, design the change so that your system will operate correctly.  If you don’t know if your system has been modified and/or you have dust buildup, check the system design.  If you don’t have the time or expertise for this, consultants can be hired to help you out.

Click here to get a free guide for helping you to evaluate if your current dust collection system is properly and efficiently operating.

 

Baghouses and cartridge collectors are usually designed to handle a maximum of 6” W.C. of pressure drop.  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 to 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 flow.  The other controller option 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 an acceptable 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 separate 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.

1. 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.
2. Wet or humid dust are conditions that can cause premature plugging. 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.
3. 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.  In this case,  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.
4. 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.
5. 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.
6. 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.

 

Click here to get a free guide for helping you to evaluate if your current dust collection system is properly and efficiently operating.

 

When your dust collectors are having issues, one of the first places to look is the airlock valve.  Often times, dust is hygroscopic and when outside air leaks into the system, humidity follows.  This can cause the dust to absorb the humidity and become sticky or harden like cement.  This can lead to plugged filters, hoppers and damage to rotary valves.  While rotary valves are the industry standard airlock, they constantly allow air leakage.  A low leakage valve is required. Double dump valves however are very low leakage, since there is no direct connection to the outside atmosphere.  The valve always isolates the conditions above it from the conditions below it.  This minimizes air leakage, thereby minimizing humidity from affecting the dust.

So if you have a non-explosive application that is hygroscopic, look into a double dump (flap) valve.

Find out more information now.

If you are having operational issues on your dust collection system, contact Aerodyne at 440-543-7400 or dc@dustcollectorhq.com.

A simple dust collection system is composed of the exhaust fan, dust collector (cyclone, baghouse, cartridge collector, wet scrubber, etc.), ductwork, and hoods.  An issue with one of these components could cause your dust collection system to fail or not work as designed.  However, the dust collector is usually the most complex component and the most likely to develop issues, but is often the most neglected.  Just like an automobile, proper maintenance of a dust collector could save a whole lot of issues in the future.

A variety of issues can develop in the operation of dust collectors.  We will discuss baghouses specifically, but cartridge collectors have very similar issues, while cyclones and wet scrubbers have their own set of items that need attention.

Plugged filters.  Bag Filters are the primary component in dust collection.  If they aren’t operating correctly, the dust collection will not be operating properly.  The filters can fail if they get plugged up or develop holes.  When plugged up, they will not let the proper amount of air through, which will cause the airflow through the system to decline; thereby, picking up less dust at the pickup points.  Plugged filters can be spotted by monitoring the pressure drop across the bags or noticing less air movement at the pickup points.  When filters are plugged up, they should be replaced and quickly. 

Holes in the bag filters allow dust past the filters; thereby, decreasing the removal efficiency in the system.  This can cause you to violate your EPA permit, cause damage to the exhaust fan and/or cause issues with the neighbors.  Holes in the filters can be spotted by bag break monitors, stack testing, or noticing dust in the exhaust.  When bags are broken they should be replaced, however, it is often difficult to identify which bag has the hole so often times multiple (if not all) bags should be replaced.

Inspect these other components.  Baghouses also contain many supplementary items that help them operate effectively.  These can also develop issues which causes the system to fail.  These items include solenoid valves, poppet valves, control panel, bag support cages and venturi, diffuser, hopper and airlocks. These items should be inspected, cleaned and components replaced if necessary.

Other factors to consider:  Failure in the cleaning system will cause high pressure drop.  Damage to the cages could cause holes in the bags.  Damage to the diffuser will cause some bags to plug up faster than others.  Damage to the hopper or excess dust in the hopper will cause higher dust concentrations that decreases removal efficiency.  An inoperative or inappropriate airlock will cause dust build up in the hopper and/or air leakage.

A yearly inspection of your baghouse will help you identify these issues before they develop. This will help your dust collection system operate at peak efficiency and as it was designed.  And as with your automobile, preventative maintenance ends up saving you money in the long run.  If your baghouse stops operating you will have to do an emergency repair or, as is most often the case, it will gradually decrease in its efficiency without you noticing. You will then be wasting your money on operating a system that isn’t effective.  And if you are inspected, you could be fined.

If you are having operational issues on your dust collection system, contact Aerodyne at 440-543-7400 or dc@dustcollectorhq.com or click the button below.

In order for a dust collector to operate at its peak performance, the hopper has to be isolated from the outside.  This means either the dust bin/receptacle is “hard connected”, meaning there are no air leaks or an airlock is used.  An airlock isolates the dust collector hopper from the outside, while allowing the collected dust to exit the system.  Common airlocks are rotary valves, trickle valves, double dump valves, and knife gates.  Some airlocks are low leakage (double dump valve and trickle valves) while others have continuous leakage (rotary valves). 

Airlocks are important because without them air will enter (system under vacuum) or leave (pressurized system) through the dust discharge valve.  If the system is under vacuum, the air entering the system from the dust discharge will re-entrain the dust back into the clean air, thereby lowering removal efficiency.  If the system is under pressure, air will blow out of the bottom, spreading dust everywhere, creating unnecessary maintenance cost for the facility.

If the system is dealing with an explosive dust, an airlock should be used to prevent an explosion from propagating from the dust discharge flange.  Specially designed rotary valves are used to prevent this.

Furthermore, airlocks allow you to change the dust bin without shutting off the system.  If you don’t have an airlock, when you need to change your dust bin, you either have to turn off the system, or operate the unit without any isolation. 

So when you are spending money to capture your dust in a dust collector, don’t forget to put an airlock on it, so you will have the best performance possible.

Read our article on what type of airlock valves to use in particular applications.

If you are having operational issues on your dust collection system, contact Aerodyne at 440-543-7400 or dc@dustcollectorhq.com.

If your air velocity is too low in your ductwork you could get dust dropping out in straight runs.  And dust collecting in ductwork is not a very good idea. 

• It is a fire / explosion hazard. If your system has a low dust loading, small enough that there isn’t enough material to support an explosion (below MEC), dust collecting in the ductwork could put the system above the MEC, thereby making the system an explosion hazard.
• Dust collecting in the ductwork causes the effective diameter of the ductwork to decrease. This causes the pressure drop through the system to increase, which will decrease the airflow through the system.  Lower airflow will cause more dust to escape the pickup hoods, thereby causing greater housekeeping, maintenance, etc.
• Dust building up in ductwork will also cause your ductwork to weigh much more. Depending on the weight the supports were designed for, if too much dust builds up, your ductwork could fall down, thereby possibly creating a dust cloud that could be explosive.

If the air velocity is too high, the static pressure of your system will be high.  This will require you to operate the exhaust fan at a higher speed.  This could increase the noise, power used and wear and tear.  High air velocity could also increase the erosion of the ductwork, thereby developing holes in the ductwork which will leak air into the system and decrease the actual airflow at the pickup points.

Watch for our upcoming article on sizing of ductwork for your dust collection system.

If you are having operational issues on your dust collection system, contact Aerodyne at 440-543-7400 or dc@dustcollectorhq.com.

Baghouses and cartridge collectors often use compressed air / plant air to clean the filters.  By pushing compressed air through the filter, in theory, dust should be removed from the filters.  However,  air compressors are high maintenance pieces of equipment that have high operating costs.  Also, the filters are never completely dust free after an air blast, meaning that, over time they become blinded. This high time-and-monetary cost can be lowered by breaking away from using compressed air and instead using a cyclone pre-filter in your dust collection system.

 By putting a cyclone pre-filter ahead of your filters you can:

• Decrease the loading on filters, reducing their cleaning from twice a minute to possibly once every 2-3 minutes.
• Eliminate the wear and tear on your filters and therefore the risk of your filter developing a hole and compromising the whole filter.

If you are looking to save money on your compressed air usage, a pulse-on-demand controller with a cyclone pre-filter is a good option to explore.

Click below to see how baghouses or cartridge collectors used as pre-filters cyclones can significantly improve your process. 

Contact Aerodyne at 440-543-7400 or dc@dustcollectorhq.com to help you problem-solve your dust collection problems.