frequently asked questions
what is the difference between the Flotrex and Memtrex series?
Flotrex filters use a pleated microfiber filtration media, while the Memtrex series use polymer membrane filtration media. As such, the Flotrex filters are more economical, but the Memtrex filters have lower micron ratings and sharper retentions than the Flotrex filters. Memtrex filters are typically used as the final filtration step, while the Flotrex may be used as a prefilter or final filter in some applications.
when should I use a pleated or depth filter?
Depth filters are primarily nominally-rated with 0.5 µm – 200 µm ratings, while the pleated filters are primarily absolute-rated between 0.03 µm – 40 µm. Depth filters are typically cheaper and have higher dirt holding capacities. As such, they are often used as prefilters to the final pleated filters and are often used when feed waters have a wide particle size distribution and/or higher levels of suspended solids, such as RO pre-filtration, Oil & Gas, and chemical processing.
Pleated filters, with their lower and more precise micron ratings are used when the particle size distribution is much narrower and for absolute removal of smaller particles, as is the case of pharmaceuticals, microelectronics, and vent filtration. Furthermore, pleated filters have lower pressure drops for comparable flow rates and micron ratings than depth filters due to their higher porosities and thinner media.
what does absolute-rated mean?
Absolute-rated has come to mean an efficiency level that is defined by a controlled laboratory test. While there is no official standard for absolute ratings, a manufacturer will make the efficiency data of these filters available. Veolia’s absolute filters have an efficiency level of 99% or greater. This means that at least 99% of particles with a diameter larger than the micron rating will be excluded by the filter.
what does nominal-rated mean?
Manufacturers do not typically document efficiency data for nominally-rated filters as they do for absolute filters. Nominal ratings are meant only as a guide and typically rank a cartridge filter’s efficiency compared to other cartridges in the same product line. For example, a 5-micron filter from a manufacturer will be more efficient than their 10-micron but less than the 1-micron cartridge. For more information on the distinction between absolute and nominal ratings, see the associated application bulletin in the Veolia library.
how do I choose which pleated filter is right for my application?
The greatest factors in choosing a pleated filter for your application are the hydrophobicity/hydrophilicity of the filter media, its chemical compatibility, and the micron rating. Hydrophobic (“water-hating”) filters are typically used for vent filtration or harsh chemical environments, while hydrophilic (“water-loving”) filters are used for aqueous (water-based) systems. Chemical compatibility is important to ensure that the filter does not become compromised during regular use. The micron rating indicates what size particles will be restricted from passing through the filter. Veolia has the technical expertise to help you find the right filter for your application to maximize lifetime and efficiency. Contact your sales representative or application engineer with any questions.
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