The Importance of Micron and Efficiency Ratings for Filter Media Selection

Article written by FCX Performance, Inc

The filter media plays the biggest role in the filtration process, so it is critical to ensure you’ve picked one that’s most suitable for your process.

When it comes to media selection, it is important to:

1. Know the micron size range of particles you’re removing 

Knowing the micron size range of particles needing to be removed from the process fluid can help you easily determine what filter media micron rating is appropriate for your filter so you can refine your fluid and protect downstream equipment. 

What is a micron? A micron is a common unit of measurement for a distance and determines a filter’s removal rating (1 micron = 0.000039 inch). The human eye can see down to about 40 microns. 

What is a micron rating and how does it impact my filter media selection? A micron rating determines the size range of debris that can be filtered or removed from liquid or gas streams— or more precisely, what you’re filtering out. Your micron rating can vary depending on what you’re trying to protect, the contaminant’s characteristics and your quality standards. Filtration media is available in sub-micron sizes up to several thousand microns, so it is imperative to know the micron size of whatever contaminant(s) you want to remove in order to select the appropriate media.

2. Understand what efficiency rating is most effective for your filter media 

What is an efficiency rating and how is it calculated? An efficiency rating measures the effectiveness of a filter to remove a given size contaminant, usually expressed in a percentage or a beta ratio. Similar to micron ratings, efficiency ratings also vary depending on the type of filter media. Efficiency ratings** are calculated by the number of particles exiting the media divided by the amount entering. Beta ratios** are calculated by dividing the particles entering the media by the particles exiting the media. Below is the formula for calculating the efficiency rating:

Efficiency Rating= (particles in – particles out)/particles in
Ex. (100-5)/100 = .95 = 95%

Beta Ratio= particles in/particles out
Ex. 100/5 = β20

**Efficiency and Beta Ratio are calculated for a defined micron range (Ex. >20 micron). 

3. Define your true needs for your filtration process 

It is common for end-users to believe they should go with the lowest micron ratings and highest efficiency to get the best results. After all, how can better be bad?

Over-filtering can lead to an array of issues including downtime and cost overruns. If you filter finer than necessary, you risk wasting product you could sell, stripping the product’s good qualities or changing filters too frequently. This wastes money, time and product. On the other side, if you don’t filter tight enough, you risk the potential of harmful contaminants not being removed from your product, possibly damaging downstream equipment. An optimal filter media selection provides the best combination of removal efficiency and run time; filtering out what is required and nothing more.

Don’t overlook the critical details. Your filter media is the most important part of the filtration process. Knowing the micron and efficiency ratings you need are the first steps in determining what filter media is best suited for your application.