Donaldson Language of Filtration I

January 2021
Donaldson Language of Filtration I

Do you understand filtration terms like Beta Ratio? How about Micron Rating or Efficiency?

Filtration Terminology can be pretty confusing. Luckily, Bergey's Truck Centers & Donaldson Filtration is here to help make these terms easy to understand with our Language of Filtration series. Come join us so you can make the right choices for you fleet maintenance needs.

Our objective is to help you understand filtration language in simple terms, so you can make informed filter buying decisions that protect your valuable equipment.

Filtration Terms


There are many terms we use when discussing filtration that is not part of our everyday vocabulary. These terms are part of a filtration language that can help us make better decisions about what we are purchasing. If we are installing it on a piece of equipment, does it meet OE specifications? Does it align with the environment that the equipment will be operating? We are going to look at each of these terms so we can use them to evaluate how well a filter performs.

Filter Design

Filter Design: The Chicken Coop

Think of filtration like a chicken coop. The fencing has holes that are small enough to keep the chickens in (and the foxes out), but will also allow other things like the feed, sunlight, and air to pass through. So that chicken wire is designed as a filter to stop big particles from passing through. It seems like an oversimplification of what a filter is, but it gets you in the mindset that a filter is designed to do a specific job.

Microns: Size Does Matter!

We're talking about beta ratio and efficiency today. This is how liquid filters are rated on performance. We are going to take a look at micron size to better understand how it plays a role in determining beta ratio and efficiency for filtration specifications. A micron is a unit of measure which equals 1 millionth of a meter, or 0.000039 inches (µm = micron). 

Micron Sizes
100 microns
80 microns
25 microns
2  microns

Particles that are 2-6 microns are actually what are wearing out modern, high pressure common-rail injectors. So the need for high efficiency fuel filtration is greater than ever before. Take a look at the chart below to see another example of the differences in micron sizes.

Fuel System Micron Size
Contaminant Impact on Components

Contaminants Have a Big Impact on Component Life

Contaminants have a big impact on component life. 70% of component replacement is due to surface degradation. Abrasive particles cause wear, loss of performance and ultimately to failure. So, a filter's ability to remove those unwanted contaminants plays a critical role in maintaining the critical components in a fleet of equipment. 

Do Cheap Filters Really Save Money?

According to an article in Machinery Lubrication Magazineprobably not. Although you could save a few dollars on a filter, it could lead to some issues such as dirty oil, dirty fuel, poor combustion, poor fuel and oil economy, and higher emissions. Ultimately this leads to more component failure and downtime.

Beta Ratio: What is it?

So now let's get into beta ratio and efficiency and what they mean. In a nut shell, beta ratio and efficiency are two ways to tell the same story.

Typically hydraulic filters are rated using a beta ratio with a micron size and a beta with that micron size. Lubrication filters are rated using efficiency, with a micron size and an efficiency of that micron size.

Once you understand beta ration, you can do a calculation to figure out the efficiency of that filter.

Beta Ratio

Calculating Efficiency

Filter Efficiency

In this example, for every 500 particles of 15µm (microns), 5 make it through. That would calculate to a beta ratio of 100. And since the beta ratio is the same regardless of how many particles there are, 100 particles would only allow 1 to pass through. Therefore this filter has an efficiency of 99% at 15µm.

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Donaldson Language of Filtration I