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Dust Collector Filters
Industrial air filters for
dust collectors come in a distinct
variety of formats. Certain dust collector filters technologies work best with certain
applications. On this page, you can learn about HEPA air filters,
electrostatic precipitators, pleated bag filters and cartridge filters.
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Grain of Sand
80-2000 µm
Human Hair
30 - 200 µm
Settling Dust
10 - 100 µm
Inhalable Dust
8.0 - 12 µm
Respirable Dust
1.0 - 5.0 µm
Smoke Particle
0.01 - 1.0 µm |
Characteristics of Dust
On one end of the spectrum you have tiny suspended
dust particles that can be filtered through an ambient air cleaner. This
may be background haze you barely notice, yet causes serious respiratory
conditions.
Respirable dust is 1.0 - 5.0 microns in size and able to
penetrate deep into the respiratory system, past the body's cilia, mucous and
natural defense mechanisms. Inhalable dust is bigger, around 10 microns in
particle size, enters the body, but gets trapped by the bodies natural filtering
mechanisms in the nose, throat and upper respiratory tract. For this
atmospheric dust, you need filtration capable of capturing the smallest
particles, either electrostatic precipitators (ESP), high quality media or HEPA filters. Most
electrostatic air cleaners can use a HEPA after-filter. Anything with a
post filter capable of capturing a good percentage of particles one
micron or smaller will provide a noticeable difference.
When looking at efficiency, you should always go by
ASHRAE compliant filter media testing. Dust spot testing
is often misleading. ASHRAE is the industry standard for describing filter
efficiency based on different particle sizes.
HEPA Air Filters
Many people have heard of HEPA air filters.
They have a reputation for being highly efficient. Here's
a little more information. High Efficiency Particle Arresting (HEPA) media
was developed for
protection against harmful particles emitted from radioactive substances.
Any filter that is HEPA rated can capture 99.97% of particles 0.3 microns in
diameter. This is according to ASHRAE testing. HEPA will stop any harmful respirable dust and most smoke
particles. But this does not mean HEPA is your total solution. HEPA
filters are usually a very fine weave. This means they constrict airflow
and clog easily. If you are collecting tooling dust, wood cutting dust or anything heavier
than light atmospheric dust, you will need more course prefilters to take out
the bigger particles. Using a prefilter extends the life of a HEPA filter.
For dust collection, HEPA filters are best used as
post filters on a multiple filter dust collection system or as a post filter or
main filter in an ambient air cleaner used to remove light atmospheric dust from
breathing zones.
Electrostatic Precipitators
Also called electronic air cleaners or ESP,
electrostatic dust collectors also collect fine particles. As far as dust
collection is concerned, ESP is pretty limited. Electrostatic cells do
well with smoke and mist, but will load up very quickly with any amount of dust
greater than light atmospheric. Like HEPA, most ESP is best used for
ambient air cleaners. Although, extremely large electrostatic
precipitators are used in smoke stacks to remove fly ash.
Pleated Bag Filters
 For a long time,
fabric bag filters have been the staple
filtration mechanism for dust collectors. They are now being replaced by
pleated media bag filters. The pleats greatly increase filter surface area.
Layers of deep pockets made of woven fabric pack away heavy loads of dust.
Pleated bag filters come in all shapes and sizes. When space is an issue,
pleated bag filters the size of large box filters can often provide adequate
dust collector filter media area. The picture to the right shows a pair of
extended media filters. The surface area is extended by
using deep pockets. In other cases, huge tube shaped pleated
filter bags replace hanging, suspended or cage supported fabric bags from a baghouse. Often washable, efficient and capable of heavy loading, pleated
filters, whether bag or cartridge, have become the current norm for industrial dust collection media.
Cartridge Filters
 To date,
cartridge filters are the most advanced form of media filtration.
Also using extended surface area, manufacturers of replacement filters are
constantly developing and improving media technology used in cartridges. Offering
high efficiency across a broad range of particle sizes, cartridge filters can be
used for just about any dust collection application. Cartridge filters are
cylindrical shaped and open on one or both ends. Pleated filtration media wraps
around the cylinder walls. When installed, one end is sealed off, leaving
the open end as the exhaust. Air is sucked in through the filter sides and
out the open end. Capable of reverse pulse cleaning, huge banks of
cartridge filters can be used to continuously collect dust from a factory's
central dust collection system.
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