|1. Bag filter
|2. Detecting a
|3. Mitigating the
consequences of a filter bag failure
|4. Preventing filter bag failures|
The use of pressure differential sensors but also more original options, such as triboelectricity measurement, can be used to detect damages of a filter baghouse that could lead to leakage of powder. This page explores those different possibilities but also how to prevent and mitigate damages to filter bags.
The damage of a bag filter can have different levels of consequences depending on the filter type, size, position and process on which it is operated. It can be a simple dust emission within a process area, quickly identified and repaired. But it can also lead to environmental problems if the dust is toxic, or to immediate process safety risks in case the leakage dust concentration is such that there are risks of explosions.
Bag filter damages can be due to different causes :
Once damage, the filter baghouse is not able anymore to retain particles that can then leak to the "clean" side of the filter and be released to the environment, sometimes through other process equipment (duct, fan...).
For most critical filters, industrials must consider the risk of filter breakage and put in place measure to prevent, detect, mitigate those failure of the filtration in their process. Some elements are given in this page.
In case of damage of a filter, it is critical to be able to detect a leakage as soon as possible in order to correct it and avoid potential quality, safety or environmental consequences. The following possibilities can be explored :
Filter bags are creating a pressure drop when the air is crossing the filter material. It is possible to monitor this pressure and detect in case there is a sudden decrease of the pressure drop which could indicate that a filter is broken and let the air flow without resistance.
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Bulk solids, when in movement, are generating charges. The charging process is called triboelectrification . This phenomena can be applied to detect a bag failure. In normal operation, there is no dust flowing behind the filter, so no static electric charges created by the clean air, but if dust is suddenly entrained through the filter, charges will be created and it will be possible to detect them, indicating that the filter baghouse is not anymore tight.
It is important, in case of filter leakage, to be able to manage the effects. The following solutions can be applied.
Figure 2 : installation of a safety filter
It is possible to prevent damages to filter baghouse thanks to the following practices :
 Triboelectricity : a parameter for solids flow measurement, Dechene and Averdieck, PBE, 1987