Defining a Filter
Filter Efficiency and Filter Life - Are they important selection parameters to consider?
January 25, 2022
As introduced in our last blog, we will explain some of the fundamental aspects of filtration technology and how they relate to each other as well as to your application. Filtration media have many different properties that impact its performance in certain applications. When selecting the best filter media for your application, consider the following important properties:
Depth vs. Membrane Filtration – presented in December blog
- Filter Efficiency
- Hydrophilic vs. Hydrophobic
- Pore size rating
- Chemical Compatibility
- Flow rate and throughput
- Thermal Stability
Filter Efficiency measures the percentage of particles which are removed from the fluid by the filtration membrane. In the filtration of liquids, filter efficiency is given based on particles at or above a certain diameter in size. In gas filtration, efficiency is stated as including all particles, including those at the most penetrating particle size. This efficiency is reported in terms of the percentage removal of the particles by weight, which does not reveal the number of particles that may pass through the membrane. This is a type of nominal filter rating. For high-efficiency filters, this is often replaced by a beta rating. Membranes rated as 1µm or finer are often rated using titer reduction values or log reduction values.
Do you know what efficiency is required in your application?
Filter life is a measure of how long a membrane will last before requiring replacement or cleaning. It can be stated either in terms of time (e.g., 30 days between changes) or volume of fluid filtered (e.g.,10,000 liters processed between filter changes). A filter material’s actual life will depend on the particulates and conditions it is exposed to in usage. Filter life ratings from lab testing with standard contaminants can be used for comparison, but do not necessarily predict actual service life. To predict actual life, testing with the application fluids under operating conditions is required. Typically, the useful life of a membrane can be determined by a two-to-four-fold increase of differential pressure in a constant flow system or a drop in pressure of 50-80% in a constant pressure system.
If you have questions related to this content or other filtration concepts or how they apply to your specific application, please contact us.
Thank you for your interest. We will be in touch soon.
Jacques Hestres, Product Manager for Media – Membrane at Pall Corporation
Joseph Vickers - Portfolio Lead, Membrane & Media
Antoine Pozniak - Product Manager Media - Membrane at Pall Corporation
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