Common Sense of Filter

Compressed air filter

It's a device that filer and purifies the compressed air. Generally refers to high-efficiency &precision filter in the compressed air system.




Working principle of filter

General filter cartridge consists of fiber medium, filter net, sponge and other materials, solid, liquid particles (droplets) condenses on the surface of filter cartridge (inside and outside) through filter material after the interception, which droplets and impurities precipitate to the bottom of the filter through gravity action by automatic or artificial discharge.



Features of general filter

Filter (activated carbon) has a limited period of use, the adsorption capacity of adsorbent will be reduced after absorbing oil. The main material of adsorption filter is absorbent, such as wool, linoleum, and cotton, and then absorbs liquid to internal part and saturating, which loses its structural advantages and quickly fails; mechanical separators and mesh type air filters usually classify by 5,10,20 and 40μm, so they are invalid for most small particles in the oil droplets.



What features apply to filter for fiberglass material?

Fiberglass can effectively separate lubricated oil droplets with 50-0.01μm diameter, it is neither absorbed nor absorbed when filtering, and it's very effective, better than other materials.


What's the working mechanism for a cohesive filter with fiberglass material as filter element?


The air flows from the middle part of filter element via four methods collecting oil drop for gravity action, inertial collision, direct interception, and penetration.


Gravity action: when airflow velocity is low in the filter, and before the oil droplets with 20-50μm diameters reaching the filter layer mostly are collected by gravity free fall, and air flow continues to fall through the filter net. The greater the airflow rate, the lower the efficiency.


Inertial collision: usually more than 1μm diameter suspension particles has a large impulse, and it's inconsistent with air flow path, thus it will inertially hit the fiber layer, the greater the airflow velocity, the greater the collision rate.


Directly intercepting: it already doesn't have usual characteristics of the liquid for particles with 0.3-1μm diameter due to too small quality, they are moving by irregular Brownian movement way, and it's inconsistent with airflow path, which can be captured more fine filter layer. The smaller the particles, the more intense the Brownian movement, the greater the probability of capture.


This article from www.bitemantech.com by Muriel.zhou

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