A good filter must be able to retain contaminants through the entire section.
To achieve this, the density of the filter must gradually increase from the outer surface to the inner surface. This "graduated density" allows the larger particles to remain trapped near the outer surface while the smaller ones penetrate the inner area and then remain stuck in the center of the filter.
Otherwise, the filter would only work as a surface filter; immediately clogging the surface area, differential pressure would increase rapidly and dramatically reduce both the ability to retain dirt and the life of the filter.
To complement the filter cartridges, Sepra is able to supply the respective plastic and stainless steel containers.
Magnetic filters are also available which, unlike cartridges, allow better removal of magnetic metal particles below 1μm.
