Gradient Density Media

One of the misapplied areas of filtration media is the use of a thick bulky filtration media to capture particulate throughout the cross-section of the matrix. This applies to both liquid and air applications, but is most frequently a problem with liquid.

The situation occurs when particulate begins to accumulate and collect in the filtration media. Typically, the vast majority of particles tend to concentrate within the top quarter to half of the media thickness. Typically, particulate does not penetrate deeper, especially with thicker materials, such as nonwoven fabrics. This particulate accumulation tends to blind the media and results in less dirt-holding capacity than theoretically calculated. In the case of a pleated cartridge, non-gradient bulky media limits the number of potential pleats and almost always reduces the service life of the filter compared to a thinner gradient density media of similar micron rating and efficiency.

For increased dirt-holding capacity, consider the use of gradient density filtration media. This may be accomplished even by reducing the thickness of the base media, while adding open, less dense layers on the up-stream side. Although each circumstance is different, you will likely achieve multiple objectives; greater flow rate, more dirt-holding capacity and longer media, filter life and in the end happier customers.

Non-Gradient Media Even Density Throughout (Courtesy of Polymer Group, Inc. )	Gradient Media Up-stream Side - Less Dense (Courtesy of Polymer Group, Inc. )
© 2004 American filtration and Separations Society