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Old 10-16-2019, 12:39 PM   #1
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"Micron" defined

So.. A micron is officially defined as one millionth of a meter. Pretty small.
A human red blood cell is about 5 microns, the diameter of a human hair is around 75 microns.

I know fuel injectors are finicky and prone to clog but seriously, is there really a need to filter my fuel down to 10 microns? Won't my Raycors with a 20 or 30 micron filter catch everything which needs to be caught ?

There is no way to visualize 5 or 10 microns. It's just too small for our eyes and probably too small to matter in an injection pump or injectors. Am I missing something ? Come on you engineers, enlighten me !

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Old 10-16-2019, 01:10 PM   #2
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Can you imagine fuel pressures in excess of 30,000 psi?? ANY solids in the fuel flow at that pressure will erode your injectors over time. It's that erosion over time that impacts the performance of the engine. Particles as small as 5 microns can be extremely damaging to modern injectors when they flow thru laser drilled orifices at extreme pressures. Unless you just like black smoke, low fuel economy, degrading horsepower, and replacing injectors every 100 hrs, run the best, most effective fuel filter you can find.
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Old 10-16-2019, 01:14 PM   #3
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Quote:
Originally Posted by Pete Meisinger View Post
So.. A micron is officially defined as one millionth of a meter. Pretty small.
A human red blood cell is about 5 microns, the diameter of a human hair is around 75 microns.

I know fuel injectors are finicky and prone to clog but seriously, is there really a need to filter my fuel down to 10 microns? Won't my Raycors with a 20 or 30 micron filter catch everything which needs to be caught ?

There is no way to visualize 5 or 10 microns. It's just too small for our eyes and probably too small to matter in an injection pump or injectors. Am I missing something ? Come on you engineers, enlighten me !

pete
As a start - a 10 micron filter does not filter all particles above 10 microns.
Perhaps look up beta ratios and start there.
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Old 10-16-2019, 01:40 PM   #4
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Originally Posted by smitty477 View Post
As a start - a 10 micron filter does not filter all particles below 10 microns.
Perhaps look up beta ratios and start there.
Is my perception that a 10 micron filter filters out everything ABOVE 10 microns correct?
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Old 10-16-2019, 02:03 PM   #5
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Thatís the dumbed down version. In reality, itís more nuanced. Consider that a range. The effective filtering also changes as it gets used. Dumbed down version is that it works better as you use it.

You obviously are wanting to lead this discussion to some outcome. Might be useful to start closer to that. But filters are a hot button discussion because of all the dumbed down truths (which do serve a useful purpose). You wonít get a common agreement on what you should do.
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Old 10-16-2019, 02:06 PM   #6
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Sorry, you did specifically mention your racors. They donít need to be 10 micron, thatís what your on engine filters will take care of.
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Old 10-16-2019, 02:11 PM   #7
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Sorry, you did specifically mention your racors. They donít need to be 10 micron, thatís what your on engine filters will take care of.

+1

We have 30 micron in our racors. The secondaries on the mains are 10.
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Old 10-16-2019, 02:33 PM   #8
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Is my perception that a 10 micron filter filters out everything ABOVE 10 microns correct?
No - a 10 mic filter does not filter out everything above 10 microns.
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Old 10-16-2019, 02:41 PM   #9
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The older engines arenít as picky for filtration so you might get away with lesser filtration, but as has been said ďdo you feel lucky?Ē. I want to do the best filtration that is reasonable. So for my Lehmans I use a 10 micron on my primaries and the standard secondaries which I have been told are in the 5 to 7 micron range. They arenít marked and so far I have not found any specs, maybe someone else has. I donít like to have to change the secondaries any sooner than necessary so I run the 10 micron primaries. I have not had any issues with them clogging or building pressure so why not? I agree that a 10 micron will not catch all particles larger than 10 micron. And yes they do improve with usage due to micro caking. As stuff builds up on the filter essentially the holes in the filter get smaller so it traps smaller particles.
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Old 10-16-2019, 02:51 PM   #10
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Quote:
Originally Posted by Pete Meisinger View Post
So.. A micron is officially defined as one millionth of a meter. Pretty small.
A human red blood cell is about 5 microns, the diameter of a human hair is around 75 microns.

I know fuel injectors are finicky and prone to clog but seriously, is there really a need to filter my fuel down to 10 microns? Won't my Raycors with a 20 or 30 micron filter catch everything which needs to be caught ?

There is no way to visualize 5 or 10 microns. It's just too small for our eyes and probably too small to matter in an injection pump or injectors. Am I missing something ? Come on you engineers, enlighten me !

pete

10 Microns is equal to about .00039". Clearances in certain areas of OLD STYLE fuel injection pumps are routinely .0005" or less. The same goes for old tech fuel injectors. (newer tech pumps and injectors have even tighter tolerances) Many small particles in fuel are abrasive. Having an abrasive particle that is a significant percentage of the clearance available means that the particle will likely cause some wear. Combine that with the fact that a 10 micron filter stops a large PERCENTAGE (but not all) particles 10 microns and larger and it becomes more obvious why good filtering is important.


EDIT - here's a good whitepaper on various size particle damage to injectors


https://www.google.com/url?sa=t&rct=...S17UJL1H61aWcy


Ken
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Old 10-16-2019, 02:53 PM   #11
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If you want to understand filtration watch this video by Parker Racor.



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Old 10-16-2019, 03:26 PM   #12
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The std secondaries on Lehman's take a WIX 33166 filter. Mfgr. Nominal micron rating is 10. I run either 20 or 30 in Primary Racor's.
I have seen 3166's rated as 2 microns on some retail sites. I claim BS.
Nominal is a pretty vague word, but my engines and injectors have been running fine for 600+ hours so I am guessing the nominal 10's are getting the job done. The newly installed Racors may extend the life of the secondaries, trap water, and are easier to change but probably won't contribute much to injector pump or tip life.
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Old 10-16-2019, 03:56 PM   #13
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In the long run, having very clean fuel extends the life of fuel components and keeps the tanks clean (if your engines have a high fuel return). Any fluid flow causes erosion. Fluid carrying debris causes more erosion. I filter my fuel to 2 microns. My Detroits have a mechanical injector with a piston that is activated by a rocker. Lot of tight clearances. I haven't changed an injector in 10 years.
Other engines have injector pumps and a valve in the injector. All injectors have nozzles. The more debris in the fuel, the faster the fuel components wear. My stuff always seems to last longer and have fewer maintenance problems than the equipment of other operators. That comes from 60 years of running marine diesels.
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Old 10-16-2019, 05:56 PM   #14
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Quote:
Originally Posted by Comodave View Post
The older engines arenít as picky for filtration so you might get away with lesser filtration, but as has been said ďdo you feel lucky?Ē. I want to do the best filtration that is reasonable. So for my Lehmans I use a 10 micron on my primaries and the standard secondaries which I have been told are in the 5 to 7 micron range. They arenít marked and so far I have not found any specs, maybe someone else has. I donít like to have to change the secondaries any sooner than necessary so I run the 10 micron primaries. I have not had any issues with them clogging or building pressure so why not? I agree that a 10 micron will not catch all particles larger than 10 micron. And yes they do improve with usage due to micro caking. As stuff builds up on the filter essentially the holes in the filter get smaller so it traps smaller particles.
On my Lehmans the primary filters are 10 microns. The first on-engine filter is a Donaldson 9 micron while the second filter is a Racor 2 micron.Click image for larger version

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Old 10-16-2019, 10:46 PM   #15
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So Pete, there you have it! You ARE missing something! A micron IS very small measurement in some respects - but relative to the molecular structure of your engines fuel injectors - it's a huge boulder. There is a world of technology that those of us who study physics, chemistry, dynamics, thermodynamics, and the engineering sciences in general do understand and appreciate even though you cannot see it or touch it and fuel filters can make a difference.
Thanks for asking, now let me tell you about man's impact on the planets weather!
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Old 10-17-2019, 02:28 AM   #16
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Several trawler guys (actual commercial fisherman) have said our 855 Cummins, popular in the industry here, will run on vomit.
I never quite understood this as it has or at least I thought it had, 2 x 2mic on engine water separator/filters after the 10mic racor.

Ordering some spares yesterday and it seems the on engine are actually 20mic so probably pointless replacing them seeing as there are 10s in front.
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Old 10-17-2019, 03:06 AM   #17
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So, this discussion strikes me as a little curious.

It is generally true that when engineers see the world, they see it through the lens of tolerances and probability densities, and when others see the world, this might not be the case. But, this doesn't mean that a typical operator or maintainer can't understand how things work.

And, I certainly don't think one needs beta ratios to understand fuel filtering enough to make an informed decision about what one needs. Percentages are easier for most people to grok. Starting with beta ratios is like asking the average person to measure the kiddie pool in fathoms vs inches, just because some commercial skipper does. Why bother? Inches (or centimeters, for my metric friends) communicate the same information in a more accessible way. I think.

Last whence I checked, Racor's filters for my filters were rated (nominal) as follows:
-- 2 micron filters: 98% efficiency
-- 10 micron filters: 95% efficiency
-- 30 micron filters: 90% efficiency.

This means, for example, that when tested under standard conditions in the standard way, the 2 micron filter retained at least 98% of the particles 2 microns or larger -- letting no more than 2% pass back out.

I think at one point I chased down the Perkins spec for the secondary filters for my Perkins 6.354MGT and 6.354(M) motors and I found it to be
-- 99% efficiency @ 14 micron (SAE).

Assuming the folks in Peterborough, England knew what they were doing, and I suspect they did, I don't need a primary (or secondary) filter rated "better" than that for the fuel injection system to enjoy a normal life with normal maintenance.

In a 2-stage filtration system, the primary fuel filter doesn't normally provide much protection to the fuel injection system. It primarily protects the secondary fuel filter from being clogged by the "big chunks" and failing prematurely before scheduled replacement, enabling the secondary fuel filter to protect the injection system.

But, what if we were talking about a new common rail fuel system instead of my venerable Perkins 6.354s? Well, then, that would be a totally different case. Those things can be crazy high pressure with really tight tolerances. They probably have N-ary fuel filter rated to 98-99+% at 2 or 3 microns. And, depending on the application, they might have three stage filtering -- 30 micron to protect a 10 micron to protect the 2-3 micron filter to protect the injection system.

But back to Racor's numbers. I forget (if I ever knew) if they are ratings under the applicable ISO (Europe) or SAE (North America) process. It matters to some engineers, sometimes. But, it doesn't matter to me. The 2ndary fuel filter is just to get the big chunks out to extend the longevity of my primary filter, remember?

I don't happen to know the applicable SAE or ISO or ANSI procedures well enough to speculate about how they are testing. But, how the test is conducted matters a lot. For example, one can pass a set of contaminants through the filter in a one way flow (single pass) -- or continuously recycle the filtered fluid (multipass), adding more contaminants with each pass to make up for what has filtered out.

The multi-pass approach is more interesting, I think, because the missed particles get passed through again -- and can be misses again. A round ball may pass through each time, but a rod-shaped containment may be hit-or-miss depending upon orientation and tumble. The other thing that is interesting -- way more interesting, I think -- is that as the filter clogs up, the pathways become smaller, and it filters more efficiently. By taking measurements over time, this performance curve can be drawn and visualized, perhaps along side a curve showing changes in pressure over time as a result of the increasingly clogged filter.

Don't hold me to this, but I think the fuel filter ratings we see are often ISO or SAE ratings that are single-pass. I suspect manufacturers have multi-pass curves, but that may be proprietary or I just haven't seen it.

One important thing to note about the applicable tests, whether SAE or ISO or ANSI, is that they test under specific, controlled lab conditions. The real world has a funny way of making such numbers look pretty. As a for example, I don't think either of the applicable standards tests under vibration (but, I could be wrong). But, just like trying to get a small part out of a container with a slightly less small opening -- the more one shakes the more likely it is that one will get the part into an orientation that can fit through the opening. We could also consider actual fuel pressures and tolerances, etc.

The point is, even given a rigorous standardized multipass nominal rating, I'd expect at least some loss of efficiency in a real world engine vs lab conditions.

Also in the real world, although as a filter clogs it gets more efficient, it also gets harder to move fuel through. At least until the resulting pressure difference opens a bypass (if present, unlikely), eliminating filtering or stalls an engine by starvation (more likely).

The upshot is that, although there are different standardized and proprietary testing methods, the micron rating is a pretty darn good measure. And, none of these measures are absolute.

And, as for those beta ratios, c'mon. Talking about efficiency that way instead of as a percentage is just changing to units less familiar to many. Beta ratios are just a count of the particles on the input side of the filter to those on the output side of the filter. So, for example, if we want to talk about the ratio at 5 microns, we'd have a ratio of the concentration (count of particles per volume) of particles greater than 5 microns on the input side to those on the output side.

-- B5 = {count of particles > 5 microns in some volume of fluid on the input side}
----------------------------------------------------------------------------------
{count of particles > 5 microns in some volume of fluid on the output side}

So, in other words, for any arbitrary micron rating, one can just convert from a percentage to a beta ratio like this:
-- Given a % efficiency = x%
-- Express it as a fraction: x/100
-- This means that if 100 particles were at the input, (100-x) particles would be at the output
-- B = 100/(100-x)

And, we can go the other way, too:
-- Given a B, as above
-- We want an x, as above
-- Take our formula from above: B = 100/(100-x)
-- Do algebra to isolate x: x = 100*(B-1)/B
-- So the filter is x% efficient

The upshot is, I understand beta ratios -- and think that it made sense to start with percentages. I'll let the reader be the judge.

If you'd ask me what is interesting about "Multi-Pass Beta Ratio (MPBR)" testing, it isn't that the units is a beta ratio vs percentage efficiency. It is that by taking periodic measurements as the filter loads over time, the multi-pass regiment provides a nice way to plot curves of filter performance over time. And, those curves can be interesting. I think.

Regardless, back to the POs question: What micron rating should be used on the primary filters? Generally speaking, nothing smaller than the Nth stage fuel filter. From the pictures, it looks like it is a 1970s or early 1980s trawler. Maybe a classic for Lehman? It probably has a 95% @ 10 micron (SAE) filter. Wild guessing. So, nothing finer grain than that is needed. And a 30 micron secondary filter is probably very appropriate to "take the big chunks out" to keep its life acceptable for the prescribed service lifetime.

Would it make sense to use a finer grained primary filter than 10 microns? Probably not or Ford (or American Diesel or Bomac) would have spec'd one for the primary. Could one sensibly choose to use 10 micron 2ndary filters? Sure. They'd extend the life of the primary filter -- at the expense of the life of the 2ndary filter. If the fuel is good, it might be a good trade for convenience. If the fuel is not so good -- it might clog up too soon and create an unfortunate surprise underway. And, that is the risk of filtering too finely on the primary -- get some unexpected junk, and it'll be clogged up when it might not need to be.

I mentioned that my Perkins engines call for a 95% @ 14 micron primary filter. What do I use as a 2ndary filter? I usually use 10 microns. Won't hurt nothing. Except when I goof and order 30s -- in which case I happily use those. Won't hurt nothing, either.

Reminds me of my old engineering methodology professor. He liked to ask (and answer), "What do you call something over spec? Waste." He was a civil engineer and also liked to say, "Any damn fool can pour enough concrete to build a bridge. It takes an engineer to make it safe and cheap."

I guess what this whole long note comes down to is that I think the original poster's question was a very reasonable one. And, yes, I, personally, think a 20 or 30 micron secondary will catch everything that needs to be caught for a 10 micron primary.

Of course, I also don't think that there is likely to be much of a difference in price, if any. And, I don't think with decent fuel one should be clogging 10 micron filters really fast. And, if you are, I hope you have many spare 2ndaries. So, as I said, I prefer to go with the 10s, myself (even with a 95% @ 14 micron primary filter manufacturer's spec). So, with all due respect to my old prof, I'm not seeing much waste in this one, within reason, either way.

My thoughts -- for whatever they are worth.
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Old 10-17-2019, 06:34 AM   #18
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Engine manufacturers, especially of yacht engines are only worried about getting thru the warranty. PERIOD. After that, they make money on parts, Volvo for example. If after warranty your injectors fail, or fuel pump, or better yet the injector pump fails, that's easy money. And then after all those expensive parts, maybe you'll buy another new engine.
Manufacturers filters, oil change interval and other recommendations aren't there to get 50 years of service out of your engine. They are just minimum recommendations.
If you have clean fuel and oil, your engine will last longer than other engines in the same service meeting the minimum maintenance recommendations.
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Old 10-17-2019, 08:02 AM   #19
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Well that's nice that the engineer says that , but Joe's mechanic says...Ö.
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Old 10-17-2019, 09:07 AM   #20
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Beta ratio and similar arithmetic "% of a certain size passing" calculations are a very big deal when comparing both fuel filter manufacturers and filter setups. For simplicity, a follower of Tony Athen's regimen of sequential fuel filtration using high beta ratio filters will be on very safe ground. Especially for today's diesel engines.

BTW, Tony did not invent sequential fuel filtration. The practice has been around for a very long time following in the footsteps of sequential sizing used for thousands of years. Sequential sizing today in the food or pharmaceutical business is extremely important. % passing, beta ratio or other analytical sizing methods are the norm.

Beta ratio is not at all difficult to understand. I'd dare say that 99% of TF readers, if so inclined, could spend 5 minutes or less and be more than capable of discerning the issues. Further Internet study for the bored reveals all sorts of tidbits. Heck, one can even get a PhD in filtration analysis.

The OP's question is dead on it would seem. The definition and use of micron as it applies to fuel filtration is relevant. As usual the devil is in the details.
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