Originally Posted By: ZeeOSix
Originally Posted By: zrxkawboy
Originally Posted By: SnowmanCO
Stating that they test to the ISO 4548-12 spec with very loose claims (99% of particles "greater than" 20 microns) would be impossible to disprove.
I went round and round with Zee on this at one time. I said that >20 means >20, and he insisted repeatedly that it actually means 20. Not sure how to argue against that kind of "logic".
The concept of numerical limits were taught early in math. As a number ever closely approaches 20, then it's for all practical purposes 20. In other words 20.000000001 is technically still >20, but for all practical purposes you can just say it's 20. Nothing earth shattering in the world of numbers. It's been discussed in many threads over the years, and the non-mathematical types never seem to grasp it.
If you've been following along lately, you'd see why the term >20 microns is used in the efficiency statement. Find the test report table out of ISO 4548-12 that was posted lately.
There are two ways to look at this topic:
1) that the spec ">20um" means that it could be rated at 30, 40, 50 etc, because it being viewed without an upper bound
2) that the spec ">20um" means it uses the 20um as the "as rated at" size as a point and not a range
It would be lovely if we could use the "greater than or equal to" symbol (the arrow with secondary line under it), but that's not a common QWERTY keyboard feature.
The way the most industries would look at this is that they view 20um to be nominally accurate to 10% of the magnitude or better. That means a stated "whole number" (ex: 10, 13, 18, 25, etc) is accurate to 1/10th of that value. Because they "rate" it at the magnitude of "20", the implication in filtration is that anything in the ".x" factor is ignored. This is very common in the engineering world. Whatever resolution you want to state a specification at, your measurement sensitivity should be 10% of that; an order of magnitude more refined. Hence if I want to state something as "20", I should be measurement accurate at "20.x" magnitude. And if I want to measure a part down to the thousandth (such as .125" of an inch), then my measuring tool needs to be accurate down to the ten-thousandth. Fram likely uses equipment that can measure to perhaps 1/10th of a microm, and so they state at the "whole" value.
Fram simply states that the size of particle is ">20um" as the pragmatic limit of their 99% efficiency. If you all want to waste time on debating if that's "20.1" or "20.9" or "20.x", I really don't care. The industry of filtration is not playing games here. By stating ">20um" Fram is stating that they are 99% efficient at catching stuff "as big as, or larger than" 20um (give or take the decimal fraction thereof).
The argument some of you make is silly. I get what your stating ... If a company has a filter that is 99% at 35um, it can claim that the filter is "99% efficient at >20um" because 35 is larger than 20. While your game of semantics it technically accurate as we use the English language, that is NOT how the filtration industry views things. Just because you want to play word games does not mean the filtration industry is going to agree with some of you.
Zee has it right.
