We’re not exaggerating when we say that filtration is a topic that touches the daily lives of practically every person living in a developed country today. From the air in our homes to the foods that we eat (including the water that irrigates that food), some type of filter element was used along the way to block the flow of undesired particulates from reaching us. At an industrial level, fluid filtration solutions protect entire populations from harmful contaminants around the clock, making the entire product segment of filtration components just as impactful to everyday life as electricity and water. With such massive benefits, there’s a little irony in the fact that filtration components operate in scales smaller than the human eye can see, holding back minuscule objects such as bacteria spores and invisible dust particulates. As such, there’s a critical balance to be found between effectiveness and lifespan when selecting a filtration solution – this is to say that the smaller a filter’s effective filtration level goes, the shorter its guaranteed lifespan.
To help readers understand this relationship, let’s introduce a unit of measurement to base our later comparisons around: the micron.
A micron is a shortened name of the metric unit micrometer, which can be written as 0.001mm or one one-thousandth of a millimeter. In other words, very small! Throughout this article we’ll use the abbreviation “µm” to describe micron dimensions, as in “1 micron” is the same as “1 µm”.
Defining Filtration Effectiveness by Particulate Sizes
How do microns correlate to filter effectiveness? Fluid filters are most often specified by their micron rating, which describes the size of particulates that the filter will successfully block as the fluid flows through.
Industrial users select filters to isolate out very specific particulates, and no two applications should ever be assumed to be identical. Some users may only need to filter free moisture from compressed air streams using a 5 µm filter, whereas others may need to protect drinking water from bacterial contamination using a 0.1 µm filter.
Determining what micron rating to specify for a filtration application is only part of the effectiveness equation. Next, users must consider filtration testing and efficiency parameters to establish an accurate effectiveness expectation.
- Filtration Test Basis – when a filter says it’s rated to capture 5 µm particulates, there are multiple interpretations of this rating possible based on how the filter was tested. For example, a filter may have a “nominal” rating of 5 µm where actual porosity is slightly above or below this value, which is distinct from an “absolute” rating of 5 µm in which the filter is guaranteed to retain 5 µm and above particulates.
- Filtration Efficiency – simply put, no filter element is 100% efficient (as in, no filter will catch 100% of particulates at a given micron rating) due to manufacturing tolerances and natural variations in materials, fluid physical properties, and particulate characteristics. Most filters offer efficiencies in the range of 80% to 96%, with highly advanced options reaching up to 99.9999%.
As we can see from the above information, defining a filter’s level of effectiveness is more than just deciding on a micron rating. Of course, there are many more factors involved, but to stay focused on the discussion of micron rating and lifespan, let’s conclude that effectiveness is a useful way to understand what level of protection a filter provides to downstream systems.
Managing Expectations around Filtration Element Lifespan
With filter effectiveness out of the way, now we can discuss filter lifespan. In almost all cases, the smaller the micron rating, the shorter a filter’s guaranteed lifespan. Why is this? Three reasons:
- Porosity Enlargement – a filter’s micron rating states the largest possible particulate size that can permissibly pass through in normal operation. As filters age, each pore or flow path experiences friction and particulate wear that can enlarge the opening over time. As these paths widen, larger particulates can pass forward, requiring the filter element to be replaced.
- Flow Restriction – filters with smaller micron ratings are more restrictive to fluid flow than filters with larger micron ratings (of the same element dimensions), which leads to higher pressure drops, higher velocities through filter pores, and lower soil retention volumes. As filter elements soil, these factors increase until the filter can no longer keep up with demand and must be replaced.
- Filter Fouling – too often, buyers purchase filters of a micron rating below their actual requirements, thinking that “smaller is always better”. In such cases, filters pick up more particulates than needed which fouls the filter element and calls for replacement much sooner than necessary.
Filter elements do not last forever, but do offer reasonable lifespans when sized, selected, and installed appropriately for the application at hand. When sized correctly, micron rating quickly becomes a non-issue in filter lifespan, as the requirements of the rest of the process take precedence (such as quality assurance and regulatory requirements).
Tips for Optimizing Industrial Fluid Filtration Performance and Lifespan
Here are several key tips for optimizing filter element performance and lifespan:
- Consult with a Qualified Expert – filtration experts can help properly size, specify, and select filtration solutions based on their application experience and access to multiple filtration OEMs.
- Application Compatibility – filters must be fully compatible with the media types and environments that they’ll serve (not just the filter element itself, but the housing’s elastomers and body material as well). Users must always check compatibility to ensure that no adverse reactions jeopardizing filter lifespan will occur.
- System Hydraulic Profile – filtration solutions are just one piece of larger fluid process or utility systems, and must be specifically selected to work with each system’s hydraulic profile. Filters must be able to support system-wide pressure peaks, flow rate variations, duty cycles, cleaning sequences, and other parameters. Of particular importance are fluid temperature and pressure, as nearly all filter elements perform differently as these parameters change.
Conclusion
In industrial fluid filtration applications, a filter’s micron rating correlates to many wider variables including filtration efficiency, effectiveness, lifespan, and cost. Selecting too low of a micron rating may lead to excessive filter replacement frequencies and wasted operating costs, whereas too high of a micron rating may introduce significant quality risks and contamination potential. Selecting the right micron rating for the job is the most direct way to balance filter effectiveness and lifespan, assuring that processes are fully protected against target contaminants for as long as possible between replacements.