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Technical Reference

Combining the ISO Rating and The ultimate solution is monitoring filter media
Filter Performance Ratings performance at removing particles in the 4 μm,
6 μm, and 14 μm ranges. Fluid analysis and
Many of the components with filters have field monitoring are the only ways to get these
recommended or specified fluid cleanliness measurements. Combine data from several tests
levels to ensure their performance and to form a range of performance. Remember,
longevity. This is usually specified per ISO 4406 actual filter performance will vary between
and with a three number rating expressed applications.
in x/y/z format. In this rating each number is
a code representing the number of particles ISO Rating System
greater than a certain size. In the example The international rating system for fluid
above x is a code representing the number of contamination levels is called the ISO contamination
particles greater than 4 micron, y greater than code and it is detailed in the ISO 4406 document.
6 micron and z greater than 14 micron (see Many component manufacturers publish filtration
ISO rating system below for more details). level recommendations using the ISO code.
While filters, on the other hand, have a given Manufacturer’s ISO contamination levels are based
efficiency performance based on the media on controlling the particle counts of 4 μm, 6 μm
used which is usually expressed in a beta rating and 14 μm particles in the system fluid. This level is
or efficiency percentage. A direct connection identified by measuring the number of particles 4μm
and greater, 6 μm and greater, and 14 μm and greater
between the beta rating scale and the ISO in one milliliter of the system fuild sample.
rating scale cannot be made.
ENGINE LIQUID FILTRATION TECHNICAL REFERENCE
ISO 4406 Contamination Codes
Range of number of particles per milliliter

ISO 18/16/13 Code More Than Up to & Including
24 80,000 160,000
23 40,000 80,000
22 20,000 40,000
21 10,000 20,000
20 5,000 10,000
19 2,500 5,000
µm 4 6 14 18 1,300 2,500
à
17 640 1,300
16 320 640
Many application differences exist in engine 15 160 320
liquid filters that need to be understood to 14 80 160
begin to correctly apply a filtration media to 13 40 80
obtain a desired fluid cleanliness. For example,
is it a contained system like the lube oil system 12 20 40
where the same fluid is re-circulated and the 11 10 20
fluid will be put through the filter multiple times 10 5 10
(multi-pass) or is it a fuel system where the 9 2.5 5
fluid is consumed and needs to be cleaned in 8 1.3 2.5
one time through the filter (single pass). What 7 .64 1.3
is the fluid cleanliness that is being started with 6 .32 .64
and what are the application environmental 5 .16 .32
conditions. These are just of few of the things 4 .08 .16
to consider when choosing the correct media to 3 .04 .08
apply.
2 .02 .04
1 .01 .02

112 • Engine Liquid Filtration www.donaldson.com