What’s Wrong with Micron Ratings for Hydraulic Filters?

To understand filter efficiency, rely on the Beta ratio, not the micron rating.

What’s Wrong with Micron Ratings for Hydraulic Filters?The purpose of a hydraulic filter is to keep contaminants like dirt and metal shavings from circulating inside a hydraulic system and causing damage. Depending on the sensitivity of your equipment and the level of performance and efficiency you require, you may need to capture extremely small contaminant particles with a high degree of efficiency.

So how are you supposed to know which filters have the capabilities you require?

Traditionally, you would just look at the micron rating.

What Is a Micron Rating?

A micron rating describes a filter’s ability to capture particles at or above the stated size. The particles we’re talking about here are extremely small—a micron is just 1 millionth of a meter long. A filter with a micron rating of 10 will be able to capture any particles 10 microns or larger. For comparison, this means it can capture particles thinner than a human hair (which is 70 microns in diameter) and smaller than what the naked eye can see (our lower limit of visibility is 40 microns).

Interpreting Micron Ratings

The problem with micron ratings is that they only indicate some ability to capture particles of the stated size. They do not tell you how effective the filter is at particle capture.

If you know whether the micron rating is nominal or absolute, you will have a little more information. Nominal ratings indicate an efficiency of about 50 percent, while absolute ratings indicate the filter is 98.7 percent efficient at capturing all particles at or above the stated size on each pass.

Unfortunately, depending on the test methods used, the same filter could be given very different micron ratings.

Beta Ratios are Better

For a much more accurate idea of how effective a filter is at removing contaminants, you should look to the Beta ratio. Beta ratios are measurements arrived at using multi-pass testing, which is now the universally accepted test method for filter efficiency.

A Beta Ratio of 2 indicates 50 percent efficiency, 10 indicates 90 percent, 20 indicates 95 percent, and so on up to a ratio of 1000 which indicates 99.9 percent efficiency.

You can easily compare Beta ratios across filter brands and know that the information you are using to make your decision is accurate—something that cannot be said of micron ratings due to variations in testing methods and results.

Need New Filters?

At Bernell Hydraulics, we carry all kinds of hydraulic filters. Give us a call at 800-326-7252 and we’ll be happy to deliver your new filters to any work site within our local service area. Or, we can ship your filters to you anywhere in the country.

Posted on July 24, 2015