Precoating

What is precoating?

Precoating describes the process of applying an additional layer on a cartridge filter. During the filtration, harmful particles stick to the layer instead of the filter. A cleaning mechanism frees the filter from the layer with the extracted substances. This results to a longer service life of the filter, because instead of replacing it, a new layer can be applied on the filter which ensures another safe filtration. 

In particular, when extracting sticky dust emissions, such as resins, it comes increasingly to a strong and rapid saturation of filters. The particles stick together and decompose the pores of the filter material, so that after only a short time, a saturation filter can absorb no further harmful particles. During precoating, an additional layer protects the filter cartridge from this sticking and facilitates its cleaning as well as the filtration of very fine solid particles.

The coat is applied before (= pre) filtration. The precoating powder is poured into the connection piece when the system is turned on. Only at a consistent pressure potential, the layer can take the path of least resistance and accumulate an even layer for optimal protection. The dirt particles settle on the powder and leave a so-called filter cake. This consists of the protective layer and the particles adhering to it.

After each filtration, the cleaning process takes place. By means of compressed air surges, the formed filter cake falls into the dust container of the system. Re-application of the precoating powder results in a new layer on the filter on which further particles accumulate. Only with a continuous repetition of the process, a reliable filtration can be ensured. Each subsequent cycle thus has a new layer on which further harmful particles can adhere.

The separation of these particles by means of compressed air pulses makes the filter usable over a longer period without showing any great loss of power. This process also supports connected extraction systems, especially in the case of high levels of dust, damp or sticky dusts. As a result, integrated saturation filters also last longer because the sticky substances adhere to the precoating layer on the filter cartridge. Filter changes are reduced.