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Types of Filters for Dust Collector Systems

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Originally posted on: https://robinsons-fs.com/types-of-filters-for-dust-collector-systems/

Dust collector filtration systems are crucial for removing pollutants from industrial airstreams. There is a wide range of dust collector filters based on cost, reusability and functionality. Here is your guide to the different types of filters for dust collector systems.

Dust collectors are made up of several different components with the filter working at the centre of the air-cleaning system. Other components like the fan, inlet, outlet, and hopper or receptacle all work together to help the filter accomplish its critical role—capturing particulate matter from the incoming airstream.

There are many types of filters for dust collector systems, and the type depends on several factors, as we shall see.

Industrial Dust Collector Filter Types

Filters for industrial dust collection systems can be broadly classified depending on the type of collector system.

Although there are several dust collector types, such as inertial separators, electrostatic precipitators, wet scrubbers, and unit collectors, we will classify the filters based on baghouse and cartridge dust collectors.

Types of Filters for Baghouse Dust Collector Systems

Baghouse filters are highly reliable, efficient, and versatile.

A well-maintained baghouse can achieve efficiency levels of up to 99% by mechanically separating particulate matter or dust from an incoming air stream. Depending on the type of baghouse, the separated dust may collect on the inside or outside of the filter.

In a baghouse, an inlet brings contaminated or dirty air from the facility into the dust collector. The fan blows the air over the filters, whereby dust particles deposit on the filter’s surface. In contrast, clean air passes through and is released into the atmosphere or pumped into the facility for reuse.

Baghouse Filter Classification Based on Filter Shape

There are four dust collector filter types based on their shape. We discuss these below.

Round bag filters

Round filter bags are the most widely used in baghouse filtration systems. They consist of an internal bag filter whose diameter is larger than the external filter bag.

Flat bag filters

A flat filter bag has a width ranging between 35mm to 50mm and an area between one and four square meters. They have a larger filtration area per unit volume. These filters fit in a frame, and the dust collects on the exterior surface.

Two-layer filters

A two-layer filter has a larger filter area than a round filter because the bag folds into two layers, almost doubling the filtration area.

Diamond filters

A diamond filter is smaller than a typical round bag. It is ideal for external filtration.

Baghouse Filter Classification Based on Filter Direction

Classifying baghouse filters based on filter direction means checking the direction from which the dusty air flows. This grouping system gives rise to two types of filters.

Internal Filter

In this system, the dirty air flows from the inner side of the filter to the external side. Dust or particulate matter collects inside the filter, and clean gas passes through to the outside.

You can change the filter in this arrangement easily.

External Filter

In this arrangement, the polluted air flows from the exterior side of the filter to the inner side. The particulate matter or pollutants collect on the outside of the filter.

Baghouse Filter Classification Based on Filter Media Material

The filter material determines various aspects, such as the filter’s lifespan, the extent of downtimes, and the performance of the filtration system.

The following are common types of baghouse filters based on the material.

Woven Filters

A woven filter features a repeating pattern that ensures the gaps between the filter’s fibres are small in order to keep out large particles. The filter is ideal for mechanical shakers and reverses air baghouse filters.

You may find a woven filter with a PTFE (Polytetrafluoroethylene) membrane. The membrane prevents particles from sticking to the fibres of the filter.

Nonwoven Filters

Pulse-jet baghouse filters use nonwoven filters to remove extremely small-sized aerosols, contaminants, and dust particles.

Felted Filters

A felted filter works through impact action and interception to filter out particulate matter. The particles hit the filter surface and are intercepted and trapped on the filter’s surface.

Fibre Filters—Natural and Synthetic Fiber Filters

Natural fibres like cotton and wool were standard in baghouse filters before synthetic fibres. Wool and cotton are cheap, but you won’t want to use them in extreme temperatures.

One advantage of a wool filter is that it can be shaped into thick felt filters and even used in humid or moist environments.

The following are synthetic fibre filters used in baghouse dust collector systems.

Fibreglass filters

A baghouse fibreglass filter is ideal for industries with high acid concentration levels. If your facility produces high levels of hydrofluoric acid, chlorides, cyanides, and bromides, you’ll want to avoid fibreglass filters.

Teflon filters

Industries that produce a lot of silica dust, like glass recycling, often use a Teflon filter. Teflon withstands high temperatures and is highly resistant to chemicals and abrasion. However, Teflon filters are more expensive.

Polyester filters

Polyester filters are ideal in dry heat environments. They resist dry heat, chemicals, and abrasion well.

A facility or an industrial plant that produces a lot of fine carbon dust can use polyester filters. Polyester filters aren’t the best option if your facility has humidity because they are easily damaged.

PTFE Tetratex filters

Filters with a PTFE Tetratex membrane are ideal for industries with high heat levels, acids, and alkalis.

Nylon filters

Nylon filters resist the effects of alkalis well, but they won’t work well where there are mineral oxides or high temperatures. They also resist abrasion well.

Polypropylene filters

Polypropylene withstands most alkalis and acids quite well. It is ideal for facilities that produce lots of moisture and chemicals.

The smooth surface of Polypropylene filters ensures minimal blinding, zero moisture intake, and optimum release of caked dust.

Types of Cartridge Filters for Dust Collector Systems

Cartridge filter dust collectors are ideal for their high efficiency and easy filter change outs. If the collector is vertical, changing the filter is even easier.

Cartridge dust collectors are also ideal for their versatility in that you can use them in different industrial applications such as:

  • Woodworking plants for filtering sawdust
  • Welding fumes
  • Plasma and laser cutter fumes
  • Sandblasting or rock grinding
  • Seed, grain, and feed processing facilities
  • Foundries for filtering hot air, carbon monoxide, and silica dust
  • Metal and paper packaging materials industries
  • Mining operations
  • Fibreglass industries
  • Cosmetic industries for filtering cosmetic powders
  • Pharmaceutical facilities
  • Graphite industries

Cartridge Filter Classification Based on Filter Media Material

Discussed below are types of cartridge filters based on filter media material.

Polyester-Cellulose Blend Cartridge Filters

A polyester-cellulose cartridge filter is 85% cellulose and 15% polyester.

Polyester-cellulose filters meet the minimum efficiency reporting value (MERV) industry standards. For the most part they are disposable, although cleaning is an option if they are monitored and changed regularly.

Nanofiber Cartridge Filters

A cartridge filter with a nanofiber coat has the highest MERV rating possible for a standard filter.

A polyester cellulose cartridge filter has a nanofiber coating which raises its MERV rating.

Nanofiber filters have an increased lifespan and a more remarkable ability to trap particulate matter on their surfaces.

To further enhance a nanofiber filter, manufacturers can treat it with a fire retardant to make a nanofiber FR filter. Nanofiber FR filters are ideal for handling explosive or flammable dust because they are fire resistant.

Spunbond Filters

A spunbond filter is one of the most durable options. It is less prone to damage and is ideal for fine fumes or dust. Its MERV rating is lower than that of a nanofiber filter, but it exceeds the minimum standard. Spunbond is the ideal filter media for cleaningand filters can be reused many times.

Spunbond Oleophobic or Hydrophobic Filters

Industrial facilities that expose filters to oily substances and moisture use oleophobic or hydrophobic spunbond filters. Although they can be more expensive, they provide optimum resistance to oil or water damage.

Spunbond PTFE

Spunbond PTFE filters help to filter sticky materials since they have a nonstick surface coating. They are specialized filters, which can make them more expensive.

What About Industrial HEPA Air Filters for Cartridge Dust Collectors?

Not all cartridge dust collectors use a HEPA filter.

Industrial HEPA Filters

Foundries and pharmaceuticals usually use an industrial HEPA after filter as a secondary measure to ensure zero-emission of heat, silica dust, and carbon monoxide or drug chemicals.

Types of Filters that Apply to Both Baghouses and Cartridge Collectors

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Some filter types apply to both cartridge and baghouse filtration systems.

Pleated Filters

A pleated filter has a larger filtration surface because the woven fabric has deep pockets that provide a lot of space for dust to collect.

If your baghouse requires frequent filter changes, consider using a pleated filter because the larger filtration surface area means the filter lasts longer than a traditional filter. You won’t have to change it often.

As a plus, you won’t require a filter cage, meaning the process of changing the filter is more straightforward.

Cartridge systems use reusable pleated nonwoven filters—a design that allows greater filtering area while using less space. Cartridge filters also mean less air-to-cloth ratio, filter size, and pressure drop.

“Pressure drop” or “differential pressure” refers to a situation where there is intense resistance in a dust collector system caused by blockage to the airstream because of caked dust collecting on the filter.

Because of the pressure drop, the system must work harder to maintain the proper airflow for optimum filtration. Pulse-cleaning the filters with compressed airstreams helps relieve the pressure build-up.

Round/Spherical and Oval Pleated Cartridge Filters

Depending on the manufacturer, the pleated filter in a cartridge dust collector may be spherical or oval-shaped.

Wrapping your head around all these types of filters for dust collector systems can be challenging. However, this can be easy if you let us assess your filtration needs and help you determine the correct filter type based on your dust collector system and materials to be filtered.

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