Dust collection needle felts

Some of the dust collection techniques employed do not employ textile filter media e.g. settling chambers, electrostatic precipitators, cyclones and wet scrubbing devices, and whilst these are mentioned here for completeness, for the remainder of this section it is intended to concentrate solely on dust collectors that engage textile filter media comprising woven or (mainly) needle felt constructions. 

The linear densities of the fibres that are used in needle felt constructions are usually in the range 1.66-3.33 decitex. In many cases, such fibres will be blended, typically in ratios of 50/50 or 66/34 the greater the proportion of finer fibres, the greater the fibre surface area and thus the more efficient the final structure. For example, it can be shown that the specific surface area of 1 kg of 3.33 decitex polyester fibre is 166 m, whereas for the same weight of 1.66 decitex fibre, the surface area is 234 m. For this reason, in recent times the use of micro-denier fibres (typically < 1 decitex or < 10 pm) has found favour where fine dusts are collected, ensuring a much greater surface filtration area and therefore less dust penetration into the body of the felt. However, as productivity rates are much slower with these fibres (they... 

Whilst needle felts are produced to countless specifications in order to address the nature, volume and velocity of the dust being collected, the type of filter employed, to meet a standard test requirement or an equipment manufacturer s specification, their area densities will generally fall between 340 and 640 gm the greater the dust load and intensity of cleaning, the greater is the area density. 

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