#1) Impingement
Impingement is the process that all media filters use
to trap dust. Simply stated, in order to trap particles the impingement
process relies on media being placed in the path of oncoming airborne particulate
and striking the particulate as it flows by in an effort to stop it. The
degree of effectiveness of this method depends on the amount of material
contained in the media filter placed in the path of these oncoming airborne
particulate.
Commercial filters using this type of process cover
the entire range of efficiencies. The finer and more dense the media used
the greater the efficiency. High efficiency particulate air (HEPA) filters
have high efficiencies along with very dense fibre packing, however the
tradeoff associated with these filters is a reduced volume of filtered
air - all things being equal.
Impingement type filters always have a built-in compromise
between air flow and efficiency. The greater the efficiency of the filter,
the lower the volume of air that is filtered. The greater the flow of air
the lower the efficiency except in the case of Dynamic filters which also
use polarization and agglomeration to trap particulate.
Engineering Dynamic's unique induced polarized media
air filters are the exception to this principle. Dynamic air cleaners are
not subject to compromise between air flow and high efficiency, and they
meet all the demands for increased air flow and high efficiency.
#2) Polarization
The second major scientific principle used in Engineering
Dynamic filters is polarization. It is well known that an electrical charge
will have an influence on any substance that comes in proximity to the
charge. Dynamic polarization takes advantage of this principle to enhanced
the effectiveness of the filtration media.
In the case of Engineering Dynamics filters, a strong
but harmless (6000 volt) charge is established on a screen within the filter
media itself. Very close to this static charge and directly influenced
by it is the fibre filtering media through which the airborne particulate
must travel. As a direct result of this static charge, the fibres and the
airborne particles that come close to them take on an electrostatic charge
known as a “POLARIZED” charge. As a result the polarized airborne particles
are drawn together with the fibre media in the same way polarized magnets
are drawn together when held close to each other. The attraction is both
certain and powerful. With tens of thousands of charged fibre strands in
each filter the efficiency of this polarized process is greatly enhanced.
In addition, as each particle attaches itself to the fibre strands it in
turn becomes part of the collection process thereby increasing the effectiveness
of the filter as it loads. Any particles that may escape through the influence
of the polarized filter media travel through the system without any residual
charge and are returned again to be filtered out on subsequent passes.
This polarization process accounts for a good portion of the filtering
efficiency of all Engineering Dynamics filters.
#3) Agglomeration
Airborne particles as explained above enter the Dynamic
filter and are polarized by the induced static charge and take on characteristics
of millions of tiny magnets. As a result four distinct possibilities can
occur:
1) These magnetised particles can attach themselves
to the charged fibre strands in the filter.
2) They can strike or become attached to each other
and form larger particles. (Agglomeration)
3) These larger (Agglomerated) particles can become
attached to the fibre filter strands.
4) The particles may pass through the filter and AGGLOMERATE
and be captured on subsequent passes.
The combination of induced electrostatic polarization
along with the process of agglomeration makes the Dynamic air filter completely
unique and a highly efficient air filter and in many cases, compares favourably
with a HEPA. This is achieved with its very low resistance to air flow.
To all this you can order the optional fibre mesh replacement pads with
an activated carbon center screen to ensure you have a potent air filtration
device !
Read the EDL bulletin on air filtration standards!
- HERE
