A Complete Guide to Bag Filters and Air Filtration

What are Bag Filters?

A bag filter, is a form of air filtration media used within manufacturing units. The purpose bag filters, as with any filter, is to ensure the removal of impurities from the overall solution; in this instance ensuring the air filtered is purified from oils, dust and dirt contamination.

Think of a filter bag as a ‘sieve’ that is letting air pass through, and stopping any other particles transferring through the conveyor system.

To ensure that your bag house dust collection units are running at maximum efficiency, pleated bag filters are used due to their long-lifespan and high filtration surface area.

The Difference Between Pleated Bag Filters and Standard Bag Filters

Between both pleated bag filters and standard bag filters there are differences in usage, material and performance.

Pleated bag filters are up-to three times larger in cloth area, which allows the bag house to collect more contaminant, but also negates the need to invest in a larger bag house for the filter bag.

You will also find that pleated bag filters do not use a filter cage due to their one-piece design.

Pleated filters in comparison to standard filter bags also use caps at the bottom to prevent leakage.

Furthermore, pleated bag filters are used at ‘surface’ level, whereas standard bag filters are used as a depth filter solution. 

The difference here is that depth filters capture any contaminant throughout the whole medium of the filter media, and are made using different materials to a bag filter (surface filter).

Understanding Air Filtration in manufacturing units

In dust collection systems within industries such as; cement, limestone etc. all manufacturing units have dust collection/extraction systems where pleated or standard bag filters are installed.

All of the dust (smaller particles of cement, dust and limestone) that are generated throughout the manufacturing process are sucked into the bag house and the filters arrest those particles so they are not thrown in the atmosphere.

This process serves two purposes:

1. Saves the environment from pollution 
2. The particles collected by  hopper which is at the base of those filters, and the material can be recycled and then used for different application. 

How Bag Filters are Made

The manufacturing of bag filters is a clever process in which the required media membrane for the air filtration system is identified and put through conditioning to ensure that it is proficient in air filtration. 
 

Choosing the Media 

First the media is produced by determining the material required to be used in the air filter. There are over 20 variants of media that can be used, and depending on the industry and substance being filtered, these materials will vary.
 
This process is fully automated where the fiber is carefully selected, during the manufacturing of the media there are various check points in place for quality assurance procedures – this is to ensure the membrane isn’t damaged or broken during production and maintains a robust and agile filter bag.
 
A good filter media will repel water, and have a low coefficient of friction. Meaning, that the filter bag media is easy-to-clean, with substances not being able to stick to it.
 
Once the media has been created it moves onto the treatment process, whereby the filter bag media may be calendared, stocked and in roll form.
 

Pleating the Bag Media

Once the roll is created, it is then Fed into a Pleating Machine. This machine pleats the Media, and provides the optimum surface area for filtering. 
 
The pleating process is used as pleated filter bags are shorter than standard filter bags, and therefore the drop out area is larger, and there is a lesser chance of abrasion. 
 

Producing the Filter Core

As the filter core is produced, the inner and outer metal core of the filter is manufactured in using a CNC machine for precision control.

A CNC machine uses Computer Aided Design (CAD) for exact precision, and saftey for workers when producing the filter case. 
 
The filter bag core is made out of SS, or Exp GI, and the inner core is added for cases where extra strength is required. During this part of the process,  the top cap is produced and lower Base for support of the filter bag. 
 
Finally, perforations of the casing are also given to filtering. 
 

Bonding the Filter Media to the Casing

During the final stage of filter bag media production, the pleated media is bonded together with the casing.
 
A ‘snap ring’ is installed below the cap to ensure that the filter retains it’s shape, stays in tact and contributes to it’s longer-lifespan and robustness. 
 

Quality Assurance

Once the filter bag is produced, a final quality assurance check takes place.
 
Here, an officer should inspect the filter quality, along with the matching of the customer requirements for the filter bag.
 
Once satisfied, loads the filter bag onto the finished goods zone ready for distribution.

The Advantages of Using Pleated Filter Bags Over Standard Filter Bags

Pleated filter bags offer more filtration than traditional filter bags. They have a larger filtration surface area, and filtration capacity.

Additionally, pleated bag filters have a longer lifespan; two-to-three times the amount of standard bag filters due to the treatment of the filter media.

With tighter emission controls and strict laws, pleated bag filters help us keep us and the environment lot cleaner. 
 
Furthermore, with less resistance through the filters, there is a reduction of energy required, thus reducing costs to the customer, and the carbon footprint.
 
Pleated filter bags generally have up-to a 58% less emission level with around 50% lower energy consumption compared to it’s standard counterpart.
 
Additionally, there is a 70% maximum of less cleaning air consumed during filtration.
 
Finally, a pleated filter bag uses types of media for finer particle retention, which again helps in lessening the environmental impact of the dust collection unit.

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