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Filter Ratings: Impact of Test Dust Changes on Filter Performance |
Introduction
For years, AC Fine Test Dust (ACFTD) has been used for purposes of calibration, filter testing, and component contamination sensitivity testing. Filter manufacturers have traditionally used ACFTD for multi-pass testing to determine ratings for filter efficiency and dirt capacity.
- Is ACFTD the industry standard?
- How do the new dust and the subsequent new filter ratings affect actual filter performance and system fluid cleanliness?
- But what has changed in your system?
- Reminder:
Is ACFTD the industry standard?
Is ACFTD the industry standard?
Yes. The current standard, ISO 4572, requires the use of AC Fine Test Dust (ACFTD). However, this test dust is no longer being manufactured. Some filter suppliers have substituted ISO Medium Test Dust (ISO MTD), also called SAE 5-80, which artificially shifts laboratory performance of filters. The filter efficiency (Beta ratio) and dirt capacity are both affected by changes in test dust.
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How do the new dust and the subsequent new filter ratings affect actual filter performance and system fluid cleanliness?
They don’t. Publishing a higher Beta rating using the new dust implies that the filter will perform better and provide a cleaner system. But the filter has not changed and neither has its performance.
Figure 1: Variation in Filter Ratings Using ISO MTD vs. ACFTD
A 
x > 200 filter in ACFTD can exhibit Beta ratios of 5000 or higher when tested in ISO MTD.
A filter tested in ISO MTD will likely show higher dirt than the identical filters tested in ACFTD.
Figure 1: Variation in Filter Ratings Using ISO MTD vs. ACFTD
x > 200 filter in ACFTD can exhibit Beta ratios of 5000 or higher when tested in ISO MTD. Top
But what has changed in your system?
| Is the filter any different? | NO |
| Is the filter more efficient? | NO |
| Is the fluid any cleaner? | NO |
| Does the filter remove more dirt? | NO |
| Will the filter life change? | NO |
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Reminder:
Publishing Beta ratios based on ISO MTD can mislead the user to believe the filter will clean the oil more effectively. While the results in the laboratory will be changing, the filter performance and actual contamination levels in the field will remain the same.
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