In a previous post, Condition Monitoring and Bulk Fuel Filtration, I discussed the importance of condition monitoring in bulk diesel fuel filtration applications.  I also explained ISO cleanliness codes and what they mean.  In the same post I discussed statistically why you should target a ISO cleanliness code than the code specified.  In this post I am focussing on targeting specific ISO codes in bulk diesel filtration applications.

Parker Velcon shared a nice graphic that further helps illustrate this logic.  For the sake of discussion, let’s say your have a specified ISO cleanliness code of 18/16/13.  Imagine a bell shaped curve with three standard deviations.  If you filter to ISO cleanliness code of 18/16/13, roughly half the the fuel will be out of spec.

ISO4406 Bell Curve1



If you filter to the left side outer limit of the bell shaped curve, then all of the fuel will meet the specified cleanliness code.  In this case, we are targeting ISO cleanliness code of 15/13/11.

ISO4406 Bell Curve 2



Now the right side of the curve outer limit is 18/16/13.

Just remember that fuel filters capture a percentage of the particulate they are rated for.  Furthermore, many filtration efficiency standards are not single pass results, rather multi-pass.  This can be deceiving to many as they think that if they are buying a 10 micron filter (for instance) they are going to remove all particles 10 micron and larger in a single pass.  This is simply not the case.  This is why it is important to target ISO cleanliness codes and not specific particle sizes.  Additionally, one should remember that if single pass results are needed, targeting finer particulate is essential in order to properly protect engines.

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