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Old 15-03-2010, 20:42   #1
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Fuel Filter Micron Size

Fuel filter size.
Hi Everyone, I am trying to make sure I have the right sequence of fuel filter size.
I have day tanks with water separator filter prior to day tank. After day tanks I have a Racor filter water separator 2 micron then at engine I have 10 micron primary filter. It seems strange to have the primary filter bigger than the Racor as far as micron size. The Racor could be 2 micron,10 micron, or 30 micron, Any suggestions do I have the correct set up, it seems that the 2 micron would stop everything and the 10Micron primary filter would never be required as the 2 micron would of stopped anything bigger??
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Old 15-03-2010, 20:50   #2
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2 microns stops up in a heart beat. It's a waste. 30 microns is the stuff you can see. Algae is trapped at 30 microns. Let the last filter stop the really small stuff. You'll run longer in a case where you have a problem using a 30 micron. Filter a lot of people get anal thinking 2 micron is better. Most engines would suggest a 30 micron for the first filter then use the suggested secondary as per the specs. Over filtering is a waste of money and actually provides less filtering should you really get a problem.
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Old 16-03-2010, 07:31   #3
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A micron is a pretty small particle - one millionth of a metre, or one thousandth of a millimetre, or 0.000039 inches.

Some comparative sizes are:
Diameter of average human hair 70 microns
Lower limit of visibility (naked eye) 40 microns
White blood cells 25 microns
Talcum powder 10 microns
Red blood cells 8 microns
Bacteria 2 microns
Carbon black 0.6 microns

See http://www.filtercouncil.org/techdata/tsbs/89-5R3.pdf
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Old 16-03-2010, 07:50   #4
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You don't mention what filter size you have before the day tank. 2 micron after the day tank may be overkill but shouldn't be a problem because the fuel is filtered before getting to the day tank. I would go with 10 micron on all three filters. Just my opinion.

Filters are not absolute. A 10 micron filter does not stop 100% of 10 micron sized particles. I think Racor claims 95%.
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Old 16-03-2010, 08:10   #5
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Paul is right. If you use a 2 micron filter, not only will your engine likely starve for fuel, but you could end up damaging your lift pump.

I did exactly what you're proposing and had fuel starvation problems (though I didn't realize it). I took a diesel class last summer and it was there I discovered my mistake. Luckily, I don't appear to have damaged the lift pump but changing the fuel filters to the less course grade did wonders for how the engine runs.
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Old 16-03-2010, 08:58   #6
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Check with your engine manufacturer. See what they recommend. New Cummins diesels are using a 2 micron filter. I am using 10 micron filters inside my dual Racors.

I don't think older engines could benefit with 2 micron filters. Plus what Paul says.

Be sure to use a biocide so the chances of your filters clogging are reduced.
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Old 16-03-2010, 13:31   #7
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Quote:
Originally Posted by DeepFrz View Post
... Filters are not absolute. A 10 micron filter does not stop 100% of 10 micron sized particles. I think Racor claims 95%.
There are 2 typical filtre “micron” ratings: 50% Nominal, and 98.7% Absolute.

Nominal rating usually means the filtre can capture a given percentage of particles of a stated size (e.g. 50% @ 10 micron; the smallest size particle the filtre will catch 50% of the time on a consistent basis). Who cares about 50% of the time? The Nominal rating is just a way to get a lower number for marketing and really doesn’t have any technical value.

Unfortunately, I believe that Racor uses undefined (50%?, 60%?, I doubt 95%?) “Nominal” micron ratings.

Absolute rating is the smallest typical particle size retained by a filtre media at 98+% efficiency. This is also referred to as the Beta=75 or 98.67% efficiency rating.

For additional information about nominal and absolute micron ratings, see the previously linked Technical Paper
http://www.filtercouncil.org/techdata/tsbs/89-5R3.pdf

And what the experts say about 2-micron filtres
http://www.seaskills.com/files/SeaSk...WhitePaper.pdf

The flow rate of a filter is the filters ability to pass a volume of fluid in a given time. Flow rate is affected by the amount of media and the restriction of that media. Generally, a filter that has high efficiency at removing small particles is going to be more restrictive to flow than a filter of the same size with same amount of media that has a lower efficiency at removing small particles.

To increase the flow-rate without sacrificing filter performance, a filter with more media surface area (bigger) may be used. While the media has the same restriction per sq: in., the larger surface area of the media will provide a higher flow rate. An increase in flow-rate can also be accommodated by adding another filter in parallel. Other media types are also available that may provide increased flow without sacrificing filtration performance.
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Old 16-03-2010, 16:18   #8
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Although that report by "experts" agrees with my belief of using 10 micron primary filter elements I dislike that report. There certainly is no scientific evidence stated in it.

What size engine (hp) will pump 100 gals. per hour?

If a filter begins to plug up as stated in the experts opinion:
Quote:
"many of the holes are partially plugged by debris in a very short time, leaving a matrix of MUCH smaller holes to filter the debris. In other words, your 10 or 30 micron primary filter turns into a much finer filter almost immediately".
Does this mean you have a filter that is going to plug up just a short time after "almost immediately"?

If the fuel going into the day tank is filtered with a 10 micron filter there should be no problem running the fuel through a 2 micron filter between the day tank and the secondary filter, although again in my opinion, not necessary. I would go with a 10 micron filter here.

Have you ever tried replacing a secondary on engine fuel filter element when the engine is hot? I doubt that it is easier to replace in a seaway than it is to throw a couple of valves to run fuel through a parallel primary filter.

Anyway, good fuel hygiene goes a long way in taking the worry out of having to change your filter in a seaway. I have had the unfortunate experience of having the fuel line plug up in a seaway by a chunk of "precipitates". An experience I hope none of you ever have, so I recommend you check your tank often and clean it when necessary. Change your filter elements on a regular basis (at least annually) and use a vacuum gauge on the primary filter.
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Old 16-03-2010, 18:38   #9
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Quote:
Originally Posted by Sergy View Post
After day tanks I have a Racor filter water separator 2 micron then at engine I have 10 micron primary filter.
typically I would see a 30mcn upstream from a 10mcn on engine filter.
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Old 16-03-2010, 19:51   #10
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If you look at the factory engine filter, there is no reason to go smaller than what is on the engine. The bigger size and area filter in your racor is going to stop more chunky stuff and still maintain flow. In most cases where you might get crap in the fuel either grown or just stuff like rust it is going to be more of the chunky kind you can see with your eye. That is all by definition larger than 30 microns (see Gords post above). This will protect the smaller surface area of the engine filter. In my engine a 5 micron particle will pass through the engine no problem and little effect. All engine filters I've seen are smaller surface area than say a 500 racor until you get into the bigger engines. Using the larger filters like a 30 will trap more chunky crap yet not lose flow. Every problem I've ever had was from loss of flow. Setting up an effective two stage system is what was designed at the factory and provides a better backstop to the engine. It increases the net effective surface area to afford the engine filter the ability to block the smaller stuff.

Your fuel pump needs to be setup with the type of filtration expected in the design of the fuel system. You want to check the specs and avoid the idea that you can make a better design because the engine designer didn't know that a 2 micron filter is smaller than a 30. The more is better approach to things rarely has merit when not considering the implications.

I set up with twin Racors each on a Y valve so I can change them with the a flip of a few valves and never stop the engine to do it. It's extra work bleeding it but when required in rough weather it's possible and I've done it once. A filter you can instantly flip on and off is the better alternative to smaller sized filters. You can however go overboard with that too. You add too many valves and eventually you get to play the find the air leak game. It might take 15 years but it happens. You can chase air leaks for months. They like to come and go.
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Old 16-03-2010, 20:54   #11
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The water taxis around these parts went to 2 Micron Filters a few years ago...for less than a season....didn't work too well...the reason being they were plugging up filters left and right
they had yanmar engines.....they finally wised up and put 30(s) in.
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Old 16-03-2010, 21:27   #12
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My Yanmar manual specifically recommends a secondary filter size no less than 5 microns. That seems as authoritative as it gets.
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Old 16-03-2010, 23:29   #13
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I can't seem to find any specifications for the required filter size for my volvo 2003 engine...

anybody out there able to set me straight?

My plan for filtering from the tanks is to run through a 30micron filter into the day tank, then a 10 micron to the engine and let the Volvo's filter handle anything else, but I don't know if that will work.

The engine came with 1 Racor 200FG, and that is what I plan to use for the two filters.
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Old 17-03-2010, 04:35   #14
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Originally Posted by rustypirate View Post
My plan for filtering from the tanks is to run through a 30micron filter into the day tank, then a 10 micron to the engine and let the Volvo's filter handle anything else, but I don't know if that will work.
that is an ideal set up.
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Old 17-03-2010, 13:08   #15
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Thanks for confirming that, I figured it woud be the best all around solution.

I will probably also put a return valve and external fuel pump to allow me to polish the fuel from the main tanks through the day tank, then back to the main.

I had also planned to have the excess fuel return from the engine go only to the day tank. This will simplify the overall system.
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