Basically there are two types of filters.
Surface filter :Only the surface area of the filtration medium is
used during the filtration process. These filters choke very fast and require frequent
cleaning. The pressure drop is greater and the life of the filter candle is short.
Examples: cellulose candles, polypropylene moulded candles, ceramic candles, stainless
steel mesh candles, etc.
Depth filters : The full depth of the filtration medium is used during
the filtration process. Therefore the area available for filtration in these filters
is more than that of surface filters. Consequently, the life of these filters is
higher and the frequency of cleaning is lower. The pressure drop is also lower.
Example: polypropylene yarn wound candles.