One of the most common questions we get asked is: How long should my filters last in my dust collector? And the short answer is: it depends. Let’s give you the long answer.

There are basically two kinds of failure in your filters. There’s what we call end of life failure, and then there is early filter failure. Let’s discuss early filter failure first. Early filter failure is when our filters suffer some kind of damage that they were not designed to withstand. This can come from one of three things: 

• Temperature
• Chemical attack,
• Abrasion

Temperature is simple enough, that’s where the maximum operating temperature for the filter was exceeded. This can take the form of the gas getting too hot, maybe we went above our maximum operating temperature, or it can take the form of sucking up sparks or embers or something else that physically caused heat damage or even caught the bags on fire or burnt them. All of these things obviously will lead to varying degrees of failure in a filter. 

The second type of failure is chemical attack. This often happens when we have process applications where the gas stream contains many different chemicals. It may be that we have to operate above the dew point so that we don’t have those chemicals condense onto the filter itself. Or it could be that there’s been some sort of upset condition in the process that has introduced more water, moisture, oxygen or some other compounds that then react badly in the dust collector to attack the filters. 

And our final early filter failure mechanism is abrasion. Abrasion comes in many forms, the most common is where we have dust particles coming in and because of some problem with the design the baghouse maybe it’s not optimally designed for extremely abrasive dust. As the dust comes in, it’s impacting the filters directly and it’s wearing holes usually in the bottoms of the filters. But this can also happen in pulse jet baghouses. For example, if we reuse old cages and they’re bent, often when the pulse jet fires the cages and bags will hit and rub on each other. Or it could be that the cage has rust or is bent and has a sharp point on it which begins to cut through the filter media causing holes and failures.

Now let’s talk about end-of-life failure. End of life failure refers to when our filters simply reached the end of their life. As opposed to early filter failure is caused by something that wasn’t designed for, end of life failure is inevitable. Eventually the dust collector filter will reach a point where you need to just replace it. But why does this happen? Well, imagine we’re looking at a cross section of a filter bag under a microscope. You have your big pieces of dust your small fines here.

Normally you would have the dust cake that forms on the surface of the filter during operation, which is the pulse off by the cleaning system. And then it reforms, and it pulses again and again. But over time little by little a few of the fines begin to make their way into the depth of the filter.

When this happens and we clean the filter, it’s only able to clean this dust that’s on the surface. The cleaning system cannot remove this dust from inside the depth of the filter. So eventually with time, we get build up like this in the depth of the filter. Now when the clean air tries to make its way through the filter media, it only has to go around the fibers of the material but it also has to try to wiggle around all that dust that’s built up inside. So, when this happens, two things occur. One is it begins to choke off the airflow, so that’s when you see your differential pressure rise and no matter how much cleaning you do, you can’t get it to go back down.

The other thing that begins to happen is because there’s so much dust in the depth of the filter, any new dust that comes in begins knocking these old pieces of dust out the other side. So, you start to see little bits of fines coming out as emissions, even though there’s no hole in the filter. When this happens, the only thing we can do is replace the filter.

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Whether you’re designing a new system, looking for help with a technical problem, or just need some replacement parts or service on your dust collector, please reach out to us and let us know how we can help.