Humidity can cause problems in the process described above.  Humidity is a way to express the amount of water in the air, (the higher the humidity, the higher the amount of water in the air).  When high humidity air enters a dust collector with fabric filters, there is a chance that the water vapor will condense and create water droplets or the dust on the filters will absorb the water as the airflow passes through.  Many dusts change their physical properties when the water content increases.  Some become sticky, some become hard like concrete, etc.  When this happens to the dust cake, it affects the ability of the air to pass through and the ability of the dust to fall off during cleaning.

When dust becomes sticky, it will adhere to neighboring dust particles and not want to fall during cleaning.  Dust that becomes hard (like concrete) will prevent air from passing through.  When one of these issues develop in a dust collector the pressure drop across the dust collector will increase.  Over time, an increased pressure drop will lower the airflow being pulled through the system.  This will decrease the airflow being picked up at hoods, therefore lowering dust collection at where operators are located.

Humidity can also be introduced in the dust collector in the compressed air.  When air is compressed, the temperature of the air increases, thereby increasing the water content of the air.  The compressed air is at its saturation point.  As the air moves through the line, it cools, thereby condensing water in the system.  If additional drying technology isn’t installed, the compressed air will have water droplets in it as it is used in the dust collectors.  This will cause the filter cake to wet and cause issues as described above.  This is why it is important to dry compressed air when dealing with dust that is affected by water.

However, sometimes no matter how you treat your compressed air, you continue to have issues.  This could be because the airline travels outside and in winter time it gets very cold. It could be because you are located near a large body of water, and humidity is high.  One way to minimize the effect on your dust collector is to minimize the dust getting to your dust collector.  Cyclone pre-filters are ideal for these applications.  Cyclones collect dust and water droplets using centrifugal motion.  This means they aren’t affected by the changes to the dust as a filter is.  Cyclone pre-filters can often remove up to 80% of the dust before a dust collector with filters.  This means you can lower the number of water droplets going into your dust collector and minimize the cleaning required, thereby not getting as much water from the compressed air system.

To learn more about the different types of Dust Collection methods,  please contact our experts at 440-543-7400 or click on the button below to get our whitepaper, Top 5 Reasons to Use a Cyclone as a Pre-Filter.

To learn more about optimizing your system, request a dust collection system evaluation today.

Filters are cleaned by blowing compressed air into the filter. If the filter is a bag (in a baghouse) then the filter has a metal cage for support. The compressed air expands the bag slightly moving it away from the cage. This dislodges the top layer of dust on the filters allowing that dust to fall into the hopper below. If the filters are cartridges, the support is an integral plastic housing. The compress air still expands the filters, dislodging the top layer of dust.

Every time the filter is expanded it is wearing out.  Over time, a hole can develop and expand enough to let dirty air through the filter.  Or the filter can get caught up on the cage and rip, thereby bypassing the filter.

The best way to minimize this issue is to perform baghouse filter cleaning only when required. Manual or adjustable timers can be used, but without constant monitoring, they will either clean too often or not enough.  A clean on demand controller is best for a baghouse.  It uses a differential pressure transmitter to monitor the pressure drop across the filters.  When the pressure drop is high enough, it will initiate cleaning until the pressure drop is lowered below a certain level.  Depending on the model of controller you have, you can also monitor the unit for broken bags and inoperative air valves.  The other benefit is that by cleaning only when required, you are saving on compressed air usage.

The main drawback of clean on demand controllers is when the bags are plugging up, you begin cleaning more often.  And if you are not properly monitoring the situation, they will begin continuously cleaning.  This happens when the bags are plugged up and no matter how much cleaning the pressure drop will not fall below the shut off pressure.

When selecting your dust collector controller, remember that effective baghouse filter cleaning means avoiding both over-cleaning and under-cleaning your baghouse filters.

So when picking out your dust collector controller, remember that you don’t want to clean your bags too much, but you don’t want to under clean them too.

There’s no substitute for an onsite inspection by an experienced expert to increase the efficiency and safety of your dust collection system. Our engineering team is available to answer any questions you have about your application. To fill out our contact form, click here.

 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.

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