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Nominal vs Absolute micron rating? #3229906 12/28/13 11:09 AM
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Sayjac Offline OP
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From reading this board and several threads I've thought that the 'nominal' micron rating was a vague spec. I was under the impression that it was 'supposed to mean' at 50%, yet there have been several threads here where that didn't appear to be the case. Someone here once concluded based on Wix or some other filter spec that it could mean any percent. Based on the definition explained by Cummins engine I'm now inclined to agree with that conclusion.

"Nominal micron rating is just a commercial trick for all efficiencies lower than 98.6%, meaning that for the same micron rating (for ex. 10 ) in the case of nominal rating, not all particles will be captured in the filter as in the case of absolute micron rating. "
Cummins filtration FAQ.

It seems that similar to the old single pass efficiency test spec the term nominal rating is an unreliable and outdated spec. So, the absolute rating (98.6%) is really the only reliable term.

Thoughts?

Re: Nominal vs Absolute micron rating? [Re: Sayjac] #3229951 12/28/13 12:10 PM
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dnewton3 Offline
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I typically interpret it to mean 50%, but since there is no industry or certification standardization for it, anyone's interpretation is as good as another.

This is why ISO and beta data the only real way to judge pure filtration efficiency.


The act of preventative maintenance, in and of itself, is FAR MORE important than brand/grade/base choices among lubes and filters.
- under maintaining something is akin to abuse/neglect; that can kill equipment by shortening the lifespan
- over maintaining something has never been proven to be anything but a waste of time and money
Re: Nominal vs Absolute micron rating? [Re: dnewton3] #3230000 12/28/13 12:58 PM
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Sayjac Offline OP
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Originally Posted By: dnewton3
...This is why ISO and beta data the only real way to judge pure filtration efficiency.

Agreed. I've just seen the terms nominal and absolute used in several recent postings regarding oil filter efficiency, so I thought I'd look for more information. But, ISO test rating and beta seems the most transparent to me.

Re: Nominal vs Absolute micron rating? [Re: Sayjac] #3230004 12/28/13 01:04 PM
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Jim Allen Offline
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Nominal is a bit vague but it is a common, but old, standard for the smallest particle that can be captured in a 50% volume on the first pass. There are several sources for that on the web (I'll let your fingers do the googling) and I have printed them out in my files, as well as been given that definition by several pros in the industry.

Absolute is technically the smallest particle that can be captured 100%. There are several standards organizations that fudge that a bit but it's always near to 100%. The 98.7% the the ISO 4548 multi pass test which is my chosen standard. It can be fudged a little too but is generally done the same way across the industry.


Jim Allen
Keepin' the Good Old Days of Four Wheeling Alive
Re: Nominal vs Absolute micron rating? [Re: dnewton3] #3230127 12/28/13 05:03 PM
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Garak Offline
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Originally Posted By: dnewton3
This is why ISO and beta data the only real way to judge pure filtration efficiency.

Assuming the beta ratios aren't whitewashed. wink


Plain, simple Garak.

2008 Infiniti G37 - Shell ROTELLA T6 Multi-Vehicle 5w-30, Wix 57356
1984 F-150 4.9L - Quaker State GB 10w-30, Wix 51515
Re: Nominal vs Absolute micron rating? [Re: Sayjac] #3230328 12/28/13 09:54 PM
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Re: Nominal vs Absolute micron rating? [Re: ZeeOSix] #3230726 12/29/13 10:46 AM
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Sayjac Offline OP
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I actually read this source before posting and the sentence regarding nominal rating that stood out to me was;
"Many filter manufacturers use similar tests but, due to the lack of uniformity and reproducibility of the basic method, the use of nominal ratings has fallen into disfavor."


As for the absolute rating, unsurprisingly it appears to be what Jim was saying regarding 100%. But the link seems to imply that to be a bit unrealistic. Otoh, the filter council link uses 50% and 98.7% respectively for nominal and absolute rating. But then goes on to say that either single pass or multipass testing can be done to test for absolute. Afaik, the multipass test in now the accepted standard.

Seems to me that without the specific ISO test procedure ie., ISO4548-12 also listed with the the term absolute there is some room for fudging what really the absolute efficiency rating could mean. But, I'd be more willing to accept the an absolute rating as 98.7% along with the micron level and the ISO test listed.

That said, an ISO4548 test standard with a percent and a micron level or a beta leaves the least wiggle room for efficiency rating.

Re: Nominal vs Absolute micron rating? [Re: Sayjac] #3231139 12/29/13 06:09 PM
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Originally Posted By: sayjac
That said, an ISO 4548 test standard with a percent and a micron level or a beta leaves the least wiggle room for efficiency rating.


Definately, the IOS 4548-12 test method seems to nail it down pretty tightly. Here's a summary of what the ISO 4548-12 test measures. You've probably seen this posted before.

"ISO 4548-12
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Methods of test for full-flow lubricating oil filters for internal combustion engines -- Part 12: Filtration efficiency using particle counting, and contaminant retention capacity.

This part of ISO 4548 specifies a multi-pass filtration test with continuous contaminant injection and using the online particle counting method for evaluating the performance of full-flow lubricating oil filters for internal combustion engines.

The test procedure determines the contaminant capacity of a filter, its particulate removal characteristics and differential pressure.

This test is intended for application to filter elements having a rated flow between 4 l/min and 600 l/min and with an efficiency of less than 99 % at a particle size greater than 10 microns."

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