Fuel Filters can't be rated less than 4 micron absolute under ISO 16889

[Freebore]

I've observed several references to fuel filters with micron ratings below 4. This may be due to companies continuing to use data from old test standards when they do that because the test standards for fuel and hydraulic filters changed in 2002. Using the current industry standard ISO test methods, there are NO fuel filters, regardless of brand, that can be rated lower than 4 micron absolute. If they are, ask what standard they are rated with as the ISO 16889 has replaced the older standard.

Filters previously rated 2 or 3 micron absolute using the old test method can only be rated 4 micron absolute or higher using the current industry standard test method. A 2 micron rating before 2002 now becomes 4. 6, a 3 micron rating is now 5. 1. Here's a sample of old vs new - NIST (ISO-MTD) reflects the new test dust:

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The old standard ASTM test method for rating filter efficiency (ISO 4402) was replaced by following ISO contamination control standards: 4406:99, 11171, 11943, and 16889. There were two main factors that influenced this. One of the factors that influenced the change was a drive in many areas of the world to standardize on ISO test methods. The other factor; the standardized test dust used for many years was no longer available. The change in both test method and test dust only affects the efficiency ratings of the filters that were previously rated less than 4 micron absolute.

Regarding the test dust, a “medium” test dust as defined by the ISO 16889 filter test method (ISO MTD) has replaced the “fine” dust that was previously used for filter testing (ACFTD). As a result of the change, the new standardized test dust doesn’t have enough sub 4-micron particles to allow for test accuracy below 4 microns.

See this link for the background on the test dusts:

http://www.machinerylubrication.com/Read/418/test-dust-ACFTD

As far as efficiencies (Beta ratios), the Filter Manufacturers Council published bulletin 89-5R3 in October 2005 and referred to nominal as 50% efficient (Beta 2) and absolute as 98. 7% efficient (Beta 75). One might argue that 99. 5% efficient (Beta 200) is absolute, but keep in mind, that is only 0. 8% above Beta 75 and it is still lab data that can be affected by variability in sampling.

 

[JR]

Very intersting. Apparantly, a lot of manufacturers are still using the standards from 11 years ago because I see a lot of ratings under 4 micron. You say the standard only affects the filters with a sub 4 micron rating, can you explain how that is? If a filter is previously rated at say 3 microns and it's new NIST rating is 5. 1, then it has the same efficiency as a filter also previously rated at 5 microns (under the old standards)?

 

[Freebore]

diesel4life,

All filters tested using the ISO 16889:1999 Multipass test use the NIST ratings and the efficiency correlates to particle counts of the media used for testing. I am not sure how one would correlate efficiencies between the new and old methods except that if the old filter claimed a Beta 75 rating at 3 micron for the old method, then the Beta rating (efficiency) under the new standard should not be any worse.

The Machinery Lubrication site is one I reference often for work as they have some of the best public literature on the topic. Rather than going into a lot of detail on Beta ratios, their site has several articles about the topic.

http://www.machinerylubrication.com/Read/564/filter-beta-ratios

One thing I have observed in filtration ratings is if filter has a Beta ratio of say 75 for 3 micron (which is 98. 7%), then it stands to reason that it will be even better at stopping larger particles and possibly be a Beta 200 (99. 5%) for 5 microns (as long as we are talking the same test standard and comparing apples to apples). Few companies reveal all of this data to the public. However, these tests are conducted in a lab under controlled conditions. While lab tests help differentiate between filter's abilities to clean in a lab environment, the real test happens on machines where filters are exposed to vibration, heat, cold, pulsating flows, etc.