Structure, working principle and maintenance of bag filters

What is a bag filter?

A bag filter is a filtration type dust collector that mainly collects dust from exhaust gas from industrial process.
By selecting suitable filter (filter bag), it is applicable to various exhaust gases with a wide range of temperatures and compositions. It has the advantage of being able to collect submicron particles that cannot be collected by cyclones.

 

Structure and working principle of bag filter

In short, the structure of a bag filter is the same as that of a vacuum cleaner. This system filters the gas containing dust using a filter (filter bag), and only the clean gas is discharged.

Filter materials include fibers such as polyester, heat-resistant nylon, and glass fibers, and are selected depending on the properties of the gas and dust.

If a large amount of dust adheres to the surface of the filter, the dust collection capacity will decrease, so when the dust collection capacity begins to decrease, backwashing (pulse jet) is used to remove the adhered dust. The dust that is brushed off is stored in a dust box and is periodically discharged.


Bag filter maintenance

Filter bag is a consumable item. If the filter is damaged, dust will leak out and it will need to be replaced. The lifespan varies depending on the application and type of dust, making it difficult to determine when it is time to replace it.

In recent years, dust meters (dust monitors) have been increasingly installed on the secondary side (gas discharge side) of bag filters to constantly monitor the dust leak amount. In fact, simply constantly monitoring the amount of dust leakage (dust concentration) with a dust meter can help optimize timing of replacing filter cloth and reduce maintenance costs.



Trouble caused by filter (filter bag)
breakage and its countermeasures

Problems caused by dust leakage

When bag filters are used for many years, the filters become damaged and deteriorate due to the friction of powder particles. As you can imagine, if the filter breaks, the collected powder will be released into the atmosphere, but it can also cause damage to the equipment.

For example, if a filter is broken, dust will leak out, and the leaked dust will adhere to the inside of the blower to cause corrosion. Due to this corrosion, loads are given on various parts of the blower, and in some cases, it may even stop. It is important to understand possible problems and take countermeasures before such a situation occurs.

Countermeasure: Monitoring dust concentration

Traditionally, working environment measurements based on manual analysis methods have been the mainstream, but there are periods when monitoring is not possible using only this method, and there is a possibility that leaks may go unnoticed. To avoid this, it is necessary to constantly monitor the dust concentration using a dust meter (dust monitor).


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