Absolute vs. Nominal
Absolute vs. Nominal
(OP)
Hi,
I would like to know how we can convert a fluid filter absolute micron rating to nominal micron rating. If there is a way.
Thanks.
dtai
I would like to know how we can convert a fluid filter absolute micron rating to nominal micron rating. If there is a way.
Thanks.
dtai





RE: Absolute vs. Nominal
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http://www.fsifilters.com/filtration_abs.nom.asp
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All from a Google search – thanks Google !
RE: Absolute vs. Nominal
The formal definition my company uses is: absolute- an arbitrary term used to describe or define a degree fo filtration...
nominal- (see absolute)
The point of it is, those terms are marketing terms. If you talk to a sales rep, look past the terms and ask about initial efficiency or beta ratio. Incidentally, beta ratio is a strange term equating efficiency to an absolute number the following are true: Beta ratio 100 = 99%; 1000 = 99.9%; 10,000 = 99.99%. Beta 1000 is in reality the best one could market. There are some which market beta 10,000, but they have not been found to live up to the hype.
ChemE, M.E. EIT
"The only constant in life is change." -Bruce Lee
RE: Absolute vs. Nominal
The way we use the terms is to mean that the rating tells you what the largest particle allowed to pass though is within a certain %.
A 50 micron rated absolute will trap almost all 50 micron particles and larger. A 50 micron nominal will trap most 50 micron particles.
However, with the units we build, filter life is a major consideration. Our market is filtering machining and grinding coolants; water, oil and so on.
A one micron filter will trap 99% of all 1 micron particles and last less than an hour before it is clogged. A 25 micron filter can also trap 99% of all 1 micron particles and larger and last weeks or months.
What we do with our filter units is to take them into a customer's operation and run them. We collect the output and have it analyzed for particle size and count. Then we match this with filter life until we hit a combination the customer likes.
We supply a unit with a 25 micron nominal bag and 25 micron string wound filter following that removes over 99% of all particulate down to one micron.
Filter material and even supplier can make a huge difference in results. Supposedly identical filters from two different suppliers can give filter life of a few hours for one and a few weeks for the other while providing equivalent filtering by our testing.
Filters are cheap and the testing isn’t all that expensive.
Also, you might subscribe to cutting tool engineering. They do a lot on coolant management.
tom
RE: Absolute vs. Nominal
Also, as Tomwalz pointed out, there is quite a bit of variation between filters of the same make, just like any other manufactured product. Handling, shelf-life, process variations, and variations in raw material all play a role in this. If consistency a primary concern, I would consider avoiding string wound cartridges and go with a depth resin bonded cartridge.
ChemE, M.E. EIT
"The only constant in life is change." -Bruce Lee
RE: Absolute vs. Nominal
Thanks for the nice comments.
Tom
RE: Absolute vs. Nominal
RE: Absolute vs. Nominal
just make more big holes and it can be rated "nominal". It's like "average".
Nominal means it can be hole for elephant and flea- but "average hole" is nominal.
Absolute means no bigger holes than stated. Correct me if I'm wrong.
Tess
RE: Absolute vs. Nominal
ChemE, M.E. EIT
"The only constant in life is change." -Bruce Lee
RE: Absolute vs. Nominal
Here in the UK, we say "The fuel consumption is nominally this, that or the other", and we mean that "that is the figure I found in the book - but don't necessarily rely on it because I haven't checked yet".
In other parts of the world (certainly in the US), the same expression means "Having measured the fuel consumption, I'm pleased to say that it came in right on spec at....."
Not normally a problem, until the day it comes to bite you.
A.