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Old 06-03-2017, 12:38 PM   #1
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I need a "Filter Microns 101" Course...

Trying to understand the fuel filters on my boat (twin Ford Lehman SP135s) and filters in general. As mentioned in a previous thread I have dual Racors that have 30 micron elements then two on-board engine filters with 5-7 microns. What I don't understand is why 30 micron in the Racors and why only filter down to 5-7 mics when 2 mics are available. It would seem that my setup allows a lot of "stuff" to get through to the on-boards which are more difficult to change out. Then there is stuff less than 5-7 mics that get into the injectors/engine. Is there a reason that I wouldn't want to get as much filtration as possible as soon as possible in the system? I know that filtering down to 2 would cause more frequent filter changes but...that would seem to be a good thing? What am I missing?

Thanks for any comments!
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Old 06-03-2017, 01:04 PM   #2
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Trying to understand the fuel filters on my boat (twin Ford Lehman SP135s) and filters in general. As mentioned in a previous thread I have dual Racors that have 30 micron elements then two on-board engine filters with 5-7 microns. What I don't understand is why 30 micron in the Racors and why only filter down to 5-7 mics when 2 mics are available. It would seem that my setup allows a lot of "stuff" to get through to the on-boards which are more difficult to change out. Then there is stuff less than 5-7 mics that get into the injectors/engine. Is there a reason that I wouldn't want to get as much filtration as possible as soon as possible in the system? I know that filtering down to 2 would cause more frequent filter changes but...that would seem to be a good thing? What am I missing?

Thanks for any comments!
You can do anything you want and will get plenty of advice, some of it ignorant like mine.

It seems to me there are two camps to this continued debate on filtering. The first camp is the one in which I fall that says that you should filter the fuel as the engine manufacturer intended. Folks a lot smarter than I and with the appropriate engineering background came up with those recommendations for a reason. They also specified fuel filtration that matched the fuel pumps in the engines. So I would say look at your engine information and see what they suggest. If they suggest 30 micron primarily filtering with 5 micron secondary, then do that.

The other camp feels that, in general, you can't have too much filtering. If 30 micron filtering is good, 20 is better and 2 is best. They never want to touch their on-engine filter so want the primaries to do all the filtering so the on secondaries never get dirty. They distrust the manufacturing recommendations for a variety of reasons ranging from being too general and not specific to their installation (not a bad reason actually) to some vague conspiracy theories involving lawyers, filter manufactures, and black helicopters.

Nothing wrong with highly filtered fuel, but there are two potential problems I can see with using 2 micron primary and secondary filters. The first as you mentioned is more frequent filter changes. Not a really bad thing, but if your engine manufacturer doesn't care about particle size before 5 microns, do you need to filter down to 2 microns? The more important question is whether your fuel system can handle the added restriction of 2 micron filtration when it was designed for 5 micron filtration. It takes more effort to pump fuel through two, 2 micron filters than it would through a 30 and a 5 micron filter.

In the few minutes it has taken me to type this, I won't be surprised if you get 5-6 responses giving you 5-6 different answers.

To read something from someone that actually knows about what he writes, check this out.
https://www.sbmar.com/articles/fuel-filtration/
https://www.sbmar.com/articles/marin...-seaboard-way/
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Old 06-03-2017, 01:16 PM   #3
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Lots of different theories. If the manufacturer goes to only 5 microns that is what would run as both primary and secondary, but he goes to 2 micron at any point I would run 2 micron filtration both on the primary and secondary as it will require no more suction or pressure than the lowest size filtration. I have a friend that uses Racors of 2 micron and changes the primaries (which are factor 2 micron filters) every ten years.
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Old 06-03-2017, 01:23 PM   #4
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Thanks. My understanding is that the FL 135's were manufactured for the 30 and then 5-7 microns that have been used. They have last 30 years and are in very good shape. Now they meet me. New guy who knows little to nothing talking about changing things. If engines have eeyeballs they are probably rolling back in their head...I think I just answered my question. Just trying to understand a little is all. I do think that the fuel flow is so low/slow on these that it would make little difference flow or fuel pump wise but its all those things that I don't know are happening that scares me away from changing. I believe Brian at American Diesel said if I wanted to go to 20 mics on the primaries then that would be ok.

Thanks for taking the time to respond. Now I am trying to figure out where the less than 5 micron stuff goes after it gets through. Brian also said that because the fuel pump is oil lube and not fuel lubed they don't get by. I have NO understanding of what that means and maybe I heard him wrong...
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Old 06-03-2017, 01:27 PM   #5
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I believe part of it is the different requirements of the newer, electronic common rail engines which require better filtered fuel (2 microns) and the older systems which don't have the same requirements. BUT

I don't see any reason not to change the Racor to 10 micron and the on engine to 2 micron and provide "cleaner fuel" as long as the flow thru the filters is adequate.

And, there are smarter people than I who will comment here.
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Old 06-03-2017, 01:42 PM   #6
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Lots of different theories. If the manufacturer goes to only 5 microns that is what would run as both primary and secondary, but he goes to 2 micron at any point I would run 2 micron filtration both on the primary and secondary as it will require no more suction or pressure than the lowest size filtration. I have a friend that uses Racors of 2 micron and changes the primaries (which are factor 2 micron filters) every ten years.
OK, a couple questions.

First, I don't know hydraulic physics at all. However, it would seem to me that you will get more resistance in a system that has two 2 micron filters in series than a system that has a 10 micron and 2 micron filter in series. Is this wrong?

Secondly.... I'm guessing that you misspoke when you mentioned your friend replaced the primaries every ten years and actually he replaces the on-engine secondaries every ten years? Given that, then I'll just remark that I've never owned a particular boat for more than 10 years. If your friend has only replaced his on-engine filters once or twice over 10 to 20 years, he might as well never bother replacing them.
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Old 06-03-2017, 01:49 PM   #7
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One question, how old are you engines?

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Old 06-03-2017, 01:57 PM   #8
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Lou, if that question was meant for me, the OP, they are 1987 vintage. 4,100 hours on them. Need to get them to 8,200 in the same shape. Just want to do what I can to make that happen. If that means leave it the same, fine. If I can help it by changing a couple of filters to be more efficient then that is great too. Just want to do things that actually help and don't just make me feel better.
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Old 06-03-2017, 02:40 PM   #9
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Four things

-- Go to boat diesel and read their fuel filtering articles
-- Second, educate yourself on what beta ratio means
-- Third, any filter when it starts out will only but "approximate" for it's listed micron rating and quickly start plugging up or going finer over time.
-- Lastly and for whatever it is worth, clean fuel turned over frequently trumps the normal fuel filter size discussions

BTW, my engines use a 30u primary and on engine of about 5u. Quite honestly, anything within reason will suffice for your application. Even what you have now.
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Old 06-03-2017, 03:01 PM   #10
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FWIW, for old school Lehmans I like you use Racor 900s with either 10 or 2 micron elements in them.

The 900s offer a very large increase in filter element surface area over the 500s.
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Old 06-03-2017, 03:19 PM   #11
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Four things

-- Go to boat diesel and read their fuel filtering articles
-- Second, educate yourself on what beta ratio means
-- Third, any filter when it starts out will only but "approximate" for it's listed micron rating and quickly start plugging up or going finer over time.
-- Lastly and for whatever it is worth, clean fuel turned over frequently trumps the normal fuel filter size discussions

BTW, my engines use a 30u primary and on engine of about 5u. Quite honestly, anything within reason will suffice for your application. Even what you have now. h




That post +1....


ttps://www.sbmar.com/articles/marine-fuel-filtration-the-seaboard-way/
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Old 06-03-2017, 03:24 PM   #12
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"Quote:
Originally Posted by Bigsfish View Post
Lots of different theories. If the manufacturer goes to only 5 microns that is what would run as both primary and secondary, but he goes to 2 micron at any point I would run 2 micron filtration both on the primary and secondary as it will require no more suction or pressure than the lowest size filtration. I have a friend that uses Racors of 2 micron and changes the primaries (which are factor 2 micron filters) every ten years.
OK, a couple questions.

First, I don't know hydraulic physics at all. However, it would seem to me that you will get more resistance in a system that has two 2 micron filters in series than a system that has a 10 micron and 2 micron filter in series. Is this wrong?

Secondly.... I'm guessing that you misspoke when you mentioned your friend replaced the primaries every ten years and actually he replaces the on-engine secondaries every ten years? Given that, then I'll just remark that I've never owned a particular boat for more than 10 years. If your friend has only replaced his on-engine filters once or twice over 10 to 20 years, he might as well never bother replacing them.


As explained to me the restriction in flow can never be greater than the smallest filter size, so you can stack ten 2 micron filter and the glow will the same as one filter.

Second, correct I meant to say he replaces the primaries and not the secondaries I asked him why he even bothers to replace the secondaries and it said it made him feel better. LOL
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Old 06-03-2017, 03:54 PM   #13
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I don't think that the CAV type filters are available in 2 microns, 5-7 is what I have seen. I use a 10 micron in my racor 900s. I would rather change them several times rather than changing the secondaries once. Brian said no problem with this setup.
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Old 06-03-2017, 04:01 PM   #14
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Both my primary and secondary filters are two microns. That's how the boat was originally outfitted.

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Old 06-03-2017, 04:11 PM   #15
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Quote:
Originally Posted by firstbase View Post
Lou, if that question was meant for me, the OP, they are 1987 vintage. 4,100 hours on them. Need to get them to 8,200 in the same shape. Just want to do what I can to make that happen. If that means leave it the same, fine. If I can help it by changing a couple of filters to be more efficient then that is great too. Just want to do things that actually help and don't just make me feel better.
So for the last 4100 hours in 30 years they have been working perfectly the way they are, I would not touch anything. If it was not the right setup your engine would not have last 30 years in perfect shape ( I assume they are ).
I hear your concern and I got the same, and reading things about fuel filtration setup and best practice just made me more worrying with all the expert advice about it. But I don't think that any engine built 30 or 40 years ago has the same requirements as contemporary engines.
But I am not an expert

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Old 06-03-2017, 04:14 PM   #16
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Lehmans don't need 2 micron filtration since the injector tolerances are not as tight as the new common rail injection engines which have very close tolerances.
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Old 06-03-2017, 06:25 PM   #17
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Your fuel can never be too clean.
Do as Smitty suggested, and read up at boatdiesel.com, and sbmar.com.
Diesel fuel is formulated much differently today than it was when your engine manufacturer wrote his spec.
It is much cleaner in terms of emissions, but is now capable of carrying more water in suspension.
Your filtration needs to be up to the task by TODAY's standards.
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Old 06-03-2017, 08:35 PM   #18
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Final micron size is determined by the injector nozzles. Some have finer sprays than others. So the secondary filter needs to be at the manufacturer's recommended size or smaller. Common (at least in bigger engines) is 30 primary and 10 secondary.
I use 2 micron in my primary because of an issue with my boiler nozzle plugging. My Detroit mains together pump 75 gallons an hour and burn about 8. So the fuel goes thru the primary and secondaries many times. (like fuel polishing) The Racors catch about 90% of the water, but the secondaries will also trap about an ounce. I change the secondaries once a year. Mostly for the water they hold. A 2 micron filter lasts about 500 hours, changed when vacuum gets to about 7", but I don't buy fuel just anywhere.
Running a 2 micron primary keeps debris out of the fuel system and makes gears in my Detroit pumps and other fuel system parts last longer and the injector pumps in my generators last seemingly forever.
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Old 06-03-2017, 08:40 PM   #19
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I don't think it makes much difference at all. Use a 30, 10 or 2 mic primary, whatever makes you happy. 2 mic will tend to clog faster. And don't run your secondaries for ten years!!! Filters age. A couple of years, max on both primary and secondary.

Most of the stuff in our filters is soft bio goop or asphaltenes, none of which is particularly abrasive. Probably could run fine with no filters at all.
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Old 06-03-2017, 08:45 PM   #20
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I need a "Filter Microns 101" Course...

Micron ratings can be fairly complex. It is imperative to know the efficiency (Beta Ratio) associated with the given micron rating. When a company publishes a micron rating without this information, it does not tell the customer how efficient the filter is at the given particle size. For instance, if Company X rates a filter at 15 micron, they may be referencing a nominal micron rating which could mean the filter is anywhere between 50% and 90% efficient at that particle size.

This might be more in Filter Microns 202, but here is some good reading material:

http://www.baldwinfilter.com/literat...9;s/89-5R3.pdf

http://www.baldwinfilter.com/literat...9;s/04-2R1.pdf
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