The present invention relates to air filters of the type having a continuous sheet of media folded in zig-zag or accordion fashion to provide a succession of substantially parallel media walls held in spaced relation by corrugaed spacers. More specifically, the invention relates to a pleated media air filter mounted in a square or rectangular frame for use in high dust loading applications.
Typical HEPA filter packs of rectangular configuration employ a continuous sheet of fiberglass, or other media, folded in transverse pleats held in spaced relation on both sides, i.e., in upstream and downstream directions, by identical spacer elements typically of corrugated aluminum. The height of the corrugations defines the amplitude of the spacers which, in turn, determines the lateral spacing of the adjacent media walls.
In conventional HVAC applications for HEPA filters, the final pressure drop is normally established at 2 inchest w.g. for filters with initial resistance of 1 inch w.g. at rated capacity. In non-HVAC applications involving unusually high dust loading, e.g., when installed in negative air machines on asbestos abatement job sites, HEPA filters are commonly operated to a final pressure drop of 3.5 inches w.g. or higher. Furthermore, it is common in such applications for the filters to be loaded to the final pressure drop of 3.5 inches w.g. within a few hundred hours of operation as compared to a final pressure drop of approximately 2 inches w.g. in many thousands of hours in typical HVAC applications. Thus, not only is the dust loading much greater, it is also vastly more accelerated.
It is a principal object of the present invention to provide a HEPA-type filter pack having superior dust-holding capacity.
A further object is to provide an air filter pack of accordion-pleated media in a rectangular frame which has superior operating charcteristics under conditions of accelerated loading.
Another object is to provide a novel and improved high efficiency air filter particularly suited for us in non-HVAC applications involving dust loading to relatively high final pressure drop.
Other objects will in part be obvious and will in part appear hereinafter.