2 micron fuel filters - SailNet Community
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post #1 of 13 Old 12-06-2011 Thread Starter
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2 micron fuel filters

Just finished helping deliver a motor yacht from Deltaville, VA to Port Everglades, FL. It was my first experience on the "dark side" and I can say it does have it's attractions -- sipping cappachino while driving the boat from a nice chair in a warm cabin is one. But that's not the point of the post.

We burned roughly 500 gallons of fuel doing the 1000 miles or so on the ICW. We changed the oil filters once and were surprised to see that the previous owner was using 2 micron filters in the primary Raycor units. My friend (the new owner) emailed the PO and was told he used 2 microns because with clean fuel "the engine will last forever". I'd heard somewhere that using such fine filters on the "pull" side of the engine's fuel pump puts excess wear on the fuel pump. Another member of the crew had tried once to get a micron recommendation from his engine's maker and was told that the secondary filter on the engine was in the 6-10 micron range. He had heard elsewhere that on big diesels like the one on this boat (a 300+ hp Lunkers) 30 microns on the primary Raycor was all you needed.

Who's right? And if you don't need or shouldn't use filters as fine as 2 microns, why does Raycor make them?

Any thoughts from the august membership of SN?
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post #2 of 13 Old 12-06-2011
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2 micron is wayyyy overkill. Most of the big yachts I used to work on had 30 mic primary and about 15 micron secondary. They also had on-board polishing systems, where it was occasionally filtered down to 2 micron but more often 10 micron. They also had valves/manifolds to change filters underway if one plugged up.

Once did a delivery on a Down Easter where we chewed through the entire inventory of 2 micron filters in about 10 hours of rough weather. Pulled in and bought 6, 30 micron primaries and made the rest of the trip, another 40 hours, on just one of them..

Even the on-engine filters for Yanmar and Universal / Westerbeke are in the 15-17 micron range as that is all they need.

I actually run a 2 micron in my on-board polishing system but a 10 or 30 micron primary in my Racor 500 depending upon what I have on-hand.. I never run a 2 mic in my engines primary, there is no need to, and it causes undue wear on the pump...
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post #3 of 13 Old 12-06-2011
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I work on an 80 foot westbay. The engines are Detroit V92 DDEC 1100 Horse power each. The Manufacturer recomends 30 Micron Primary filters.

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post #4 of 13 Old 12-06-2011
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The small engine 'guard filter' you see mounted on many engines is indeed 15-17M and is a 'last chance' filter in case any 'upstream' filter becomes damaged (breaks a pleat) or 'soft/deformable' particles begin to extrude through the 'upstream' filter, etc.

To protect the engine 'guard' use a 10M (nominal rated, 97% efficiency) Racor.etc. immediately upstream of the 'guard'. If the history of the tankage is such that the 10M prematurely plugs with 'hard particles' such as rust, sand, etc. then a 30M should precede the 10M. (30M) --> 10M ---> 17M (engine guard).

In nature particles become exponentially more numerous the smaller the particle size distribution. What that means on a practical basis is that beside the 2M requiring 5 times the 'pump power' / work (∆P) to operate the filter at its 'rated' flow, it will plug/choke 5 times FASTER then a 10M filter.
20M is universally accepted as the 'most damaging' particle size in a small diesel engine.

------
In a recirculation system, a high flow constantly recirculation-polishing filter, the 'most efficient' filter (above filter sizes) will be in the 5M to 10M rating . After several tank 'turnovers' through a 5 or 10M, the 'resident' average particle size in the tank will approach 'sub-micronic' (crystal clear fuel). A 5-10M will have % of 'capture sites' at 1M and will operate between 20%-50% efficiency .... at 0.5-1M, etc. Since the fuel 'turns-over' many times through the same filter over and over and over you eventually (given enough time) remove essentially ALL 'detectable' particles. Most importantly, (and with non-constant displacement pumps - NOT a 'gear pump' etc.) The 10M "turns the system over" FASTER than the 5 (about twice as fast) and MUCH faster than a 2M @ about 5 times faster. Even if you only remove 10% of 0,5M per 'turnover' you will after 10 'turnovers' reach a stability of 'essentially all particles removed'.
Especially when a 'slug' of particles breaks loose from the tank walls (dirty tank) the 'recovery' back to 'normal' particle levels (using a 10M, for example) in the tank will be 'magnitudes' FASTER ... back to 'normal' levels; if you use a 2M then that 'recovery' will take ~5+ times 'longer'. All such filters have a *gallons per minute per psi differential pressure (GPM/psid) rating* ... a 10M will have ~5 times the GPM/psid of a 2M. For recirculation filters, you want a LARGE M (about 5-10 times the size of your 'target' size rating), and you want a BIG surface area filter for even lower pressure drop - all to gain the 'fastest turnover'. Well designed and engineered recirculation polishing filtration is a mathematical 'trick' using the 'Newtonian laws of exponential decay' vs. TIME ...... plus, larger M retention filters are 'cheaper' to boot.

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post #5 of 13 Old 12-07-2011
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Quote:
Originally Posted by billyruffn View Post
Just finished helping deliver a motor yacht from Deltaville, VA to Port Everglades, FL. It was my first experience on the "dark side" and I can say it does have it's attractions -- sipping cappachino while driving the boat from a nice chair in a warm cabin is one. But that's not the point of the post.

We burned roughly 500 gallons of fuel doing the 1000 miles or so on the ICW. We changed the oil filters once and were surprised to see that the previous owner was using 2 micron filters in the primary Raycor units. My friend (the new owner) emailed the PO and was told he used 2 microns because with clean fuel "the engine will last forever". I'd heard somewhere that using such fine filters on the "pull" side of the engine's fuel pump puts excess wear on the fuel pump. Another member of the crew had tried once to get a micron recommendation from his engine's maker and was told that the secondary filter on the engine was in the 6-10 micron range. He had heard elsewhere that on big diesels like the one on this boat (a 300+ hp Lunkers) 30 microns on the primary Raycor was all you needed.

Who's right? And if you don't need or shouldn't use filters as fine as 2 microns, why does Raycor make them?

Any thoughts from the august membership of SN?
My thought is that I got confused reading about 2 micron OIL filters in the fuel system. Further reading did clarify.
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post #6 of 13 Old 12-07-2011
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some of the newer diesels require much cleaner fuel than the 8V's of old, but nonetheless, 10 micron should do just fine.

2 micron for polishing systems, but be prepared to change them more often, as they do clog quicker/easier
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post #7 of 13 Old 12-08-2011
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For many years on yanmar 3gmc, have used 30 mics on primary
and 15 mics on seconary.
On a shake, rattle and roll passage on a sailboat...2 mic. is a
problem waiting to happen and one would need to carry an
extra fuel filter.
2 mic may make sense polishing.
2 micron for polishing.
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post #8 of 13 Old 12-08-2011 Thread Starter
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Quote:
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My thought is that I got confused reading about 2 micron OIL filters in the fuel system. Further reading did clarify.
See what happens when a blow boat guy goes to the dark side....he gets the liquids in the engine confused!
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post #9 of 13 Old 12-09-2011
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Success with Racor R15S 2 micron

I hesitate to provide a contrary view, but I can vouch for a 2 micron primary filter working just fine and being beneficial if you address underlying problems. My layout is a Racor 2 micron primary, and the standard Universal diesel secondary on the engine. I have 600 hours on this arrangement through all sorts of conditions.

When I switched my fuel to a % of biodiesel when I bought our boat, I knew there would be sludge in the 20 year old infrequently used tank wanting to come out. I immediately switched the Racor to 2 microns so as not to suck any crud into the injection pump. I changed filters a few times in the first 100 hours and they had a moderate amount of crud each time. I then did a manual self-polishing by routing the electric fuel pump back to the tank and running it a while. By the way, on my Universal 5432 the fuel pump is external and electric.

Anyway, I've now put 600 hours on this arrangement and change my primary and secondary filters every year out of an overabundance of caution. I have motored through truly nasty conditions and still my 2 micron Racor is essentially pristine when I change them every year.

I trust in the wisdom that clean fuel makes a diesel happy, and since my fuel pump is electric and external, and I always carry a spare just in case (though I have yet to need it in 5 years!) I have no concerns about the added strain on the pump.

My view, simplified and boiled down, is that if your fuel tank is dirty enough to clog a 2 micron filter in any serious way, you have bigger and more pressing problems than your fuel pump. Clean the tank, install a 2 micron, and you will never again have to worry about any damaging particles hitting your delicate and expensive fuel injection system.

Here's a picture of my secondary filter (downstream of the also clean Racor R15S) after 150 hours of use:Stories of Aeolus- Our Gulf 32 Pilothouse: Secondary fuel filter change and she's spotless!

Aeolus
Gulf 32
Bainbridge Island, WA

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post #10 of 13 Old 12-09-2011
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I'm sure we'll get a raft of grief but I'm with Windrope. We have a Racor FG500 primary fuel filter that I have been running 2 Micron filters in exclusively for the past 10 years without difficulty. My thinking is that, with a filter system rated for 60 gallons per hour, but pulling somewhat less than a gallon per hour for our Perkins 4-108 at a cruising RPM of 2500-2700 RPM, that filter would have to get awfully foul before our fuel flow were choked off. Moreover, by not screwing around with the secondary filter on the engine itself any more often than necessary, I avoid having to bleed the engine which--on our boat--is a serious PITA!

FWIW...

"It is not so much for its beauty that the sea makes a claim upon men's hearts, as for that subtle something, that quality of air, that emanation from the waves, that so wonderfully renews a weary spirit."
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