The Negatives of Pulsing Bags Too Often

Using bags, cartridges, and filters for dust collection is one of the best ways of capturing dust particles in the airstream. The filter allows the air to pass by while preventing the particulate from passing through. The dust particles then begin to build up on the filter. This build up helps prevent smaller particles from passing through, but also makes it harder for air to pass through. Over time this dust layer will prevent the air from passing though, thereby plugging up the filters.

To prevent plugging of the filters, they are often cleaned by blowing air through them in the opposite direction of airflow. Baghouses and cartridge collectors use compressed air which expands the filter slightly so that it drops off material. The dust then falls into the hopper below. The periodic expansion of the filters will over time cause holes to form.

Dangers in Cleaning Out Filters

For filters and other inline filters, it is not as easy to clean filters during operation. Usually the filter needs to be pulled out of service and then air is blown through the filter (in the opposite way) to remove the dust from the filter. However, using high pressure air to blow out the filters can also cause holes to develop in the filter.

When these holes develop in filters, air will rush through the holes, taking dust with them. Since the holes in the media have lower resistance than the filters, air will find it easier to go through the hole than the filters. This will cause the hole to grow in size over time. And as more and more air passes through the hole, more dust will bypass the filter and contaminate the cleaned air.

Pressure Gage Is Recommended

When using filters, it is always recommended to install a differential pressure gage across the filter. As dust builds up on the filter, the differential pressure will increase. And as the pressure drop across the filter increases, less air will be flowing through the filter. So when you notice a high pressure drop across the filter, this means it is time to remove and replace or clean the filters. If you don’t replace the filter and the pressure drop decreases then it probably means that you have a hole (or holes) in your filter.

So when you are cleaning your filters, be sure to check that no holes develop. The holes can be caused by high airflow when blowing out or after repeated expansions by compressed air. The use of differential pressure gages will help you identify if a hole develops before noticing dust in the clean air. If you find that you are cleaning or replacing filters too often, installing a pre-filter such as a cyclone can lower the dust loading on the filters, thereby extending their life.