Proper Racor Primary Fuel Filter size?

[RichH]

The engine mounted 'guard' filter that is mounted on most QM & GM Yanmars are in the range of 15-18µM (nominal rating.
The 'engine mounted' filter should NOT be considered as part of the 'workhorse' portion of the fuel filtration system .... but only as a 'last resort' filter to protect the high pressure pump and injectors. The small engine mounted 15-18µM filter that is 'challenged' by a HIGH load of much smaller particles will (by design) quickly 'blind off' and prevent flow to the engine, even when challenged with a high load of 5-15µM particles; the capture mechanism in such filters by 'bridging' of particles (two or three 5µM particles 'bridging together' and getting stuck in the 15µM 'pore' of the filter media). the filter that is preceding the engine mounted 'guard' filter should be SMALLER in µM than the 'guard' filter (but of vastly larger effective filter surface area - sq. ft.).

Racor filter media is typically 2, 10 & 30µM. For good (fuel oil) 'filter practice' to gain the maximum service life the so-called 'primary' should be approx. 5X (in µM) LARGER than the next succeeding (so-called secondary) stage - the engine 'guard filter' is ignored as its just there if all hell breaks loose - such as one of the preceding filter stages breaks its pleats, bypasses or begins to extrude soft particles.
So, a proper system for your (2 or 3GM) usage should be 30µM (primary) ---> 10µM (secondary) ----> engine 'guard filter'.

Running a 2µM filter in place of a 10µM will result in much heavier workload on the engine's lift pump (possibly causing premature failure of the pump diaphragm), rapid 'choking' if indeed the filters are challenged by a high 'dirt load' --- as there are exponentially MORE (by wgt.) smaller particles than larger particles. At constant flow (engine rpm) conditions (typically for small marine diesels at .5 to .75 gallons per hour at WOT) A 2µM filter will have ****1/5**** the flow rate capacity and ****1/5**** the on-stream-service-life of a 10µM filter !!!!! If your system was designed for 10µM and you replace with a 2µM (erroneously thinking than 'smaller' µM must somehow be better) you will need a 2µM that is FIVE TIMES the surface area of the 10µM to do the exact same job - to maintain the flow rate and the obtain the same in-service time/ gallons 'thoughput'.

Simple speak: Primary should be 5X the µM rating of the secondary, ignore the 'guard filter' mounted on the engine' - but change it regularly..... and BEST advice is to change out with the LARGEST surface area filter that will fit.

BTW - filters only remove the crud that flows to them. If you regularly clean the tank internals, so that all the deposited resins (formed by FUNGUSES - Cladosporium Resinae, etc.) are removed from the WALLS, there will be little chance of these particulates coming loose (from the tank walls) and unexpectedly 'choking' your filters. Sure, you can gain particles from the suppliers dirty tankage; but, that is rare in the USA.

CLEAN OUT your Tank on a regular basis !!!!
Install press/vac. gages on the filters so you know WHEN to change the filters ... there isnt any other way, except when the engine stalls which is usually during a heavy/rough sea state.

hope this helps.
))

 

[tsmwebb]

...
So, a proper system for your (2 or 3GM) usage should be 30µM (primary) ---> 10µM (secondary) ----> engine 'guard filter'.

... If your system was designed for 10µM and you replace with a 2µM (erroneously thinking than 'smaller' µM must somehow be better) you will need a 2µM that is FIVE TIMES the surface area of the 10µM to do the exact same job - to maintain the flow rate and the obtain the same in-service time/ gallons 'thoughput'.
...

Wow, thanks for all of that!

My 2gm20Fs were installed with R26S's (2 micron) elements as the only suction side filtration. This was done by the Yanmar dealers (a large and reputable branch). I haven't been able to locate a official Yanmar recommendation on what suction side filters to use. I am not naive enough to think that the dealers did either... But, as nearly as I can tell, the system has worked well despite years of hard cruising. I understand what you're saying about area and lift pump workload if too small a filter is used. My question is, is 2 microns smaller than what Yanmar intended for the 2gm? It's not like the 2gm sucks much fuel and people use the same sized canister filters on much larger engines. Engines that might well have 5 or more times the flow rate...

--Tom.

 

[Maine Sail]

The engine mounted 'guard' filter that is mounted on most QM & GM Yanmars are in the range of 15-18µM (nominal rating.

Rich,

I know some of the older manuals say the engine mounted filter or "guard" is a higher nominal rating but the replacement element that you you buy, listed as part number 104500-55710, are a 3 micron element not a 15-18 micron. I have confirmed this with Yanmar tech support via phone as well.

Would 30 micron to 3 micron set up tend to plug up the 3 micron filter faster if you had a dirty tank??

Would this make a 10micron primary ok if the secondary "guard" element is a 3 micron or would you still advise a 30? There seems to be a lot of misinformation in the Yanmar manuals vs. what the parts distributors are selling..?

My Westerbeke secondary is also a 3 micron rated filter and I put a 10 micron Racor element in front of it but keep a fairly clean tank. I have also used 30 to 3 sequence before with no real noticeable difference in how clean the secondary filter came out.

 

[RichH]

The filter industry is clouded with a lot of 'jargon' when it comes to ratings. Unless one is deeply involved within this and adjacent industries it is VERY easy to be mislead and misdirected by the 'filter ratings'. This jargon goes back to the days when most filters were (some still are) not very accurate.

What the Yanmar tech support folks are omitting is the removal efficiency (%) AT the µM rating. What they are offering is on a removal efficiency approaching 98% is a 15-18µM filter!!!!. The Yanmar filters (from the various suppliers who private label for Yanmar) will at 3µM be anywhere between ~60-90% removal efficiency .... AT 3µM. Typically by ASTM methodology (a redefinition) of the filter industry standard: Oklahoma State University (OSU) F2 test stand using AC (fine) test dust.
Take that Yanmar so-called 3µM (undefined with % removal) and you will find that it will pass MUCH larger than 3µM particles - the typical is 3µM @ ~60% efficiency, 5µM @ ~70% efficiency, 10µM @ ~85%, 15µM @ ~98% .... and the manufacturer can still call it a 3µM filter ... a ***NOMINAL**** 3µM !!!!!!! Unless you KNOW the value of the NOMINAL rating in % removal efficiency (usually published by 'ethical' manufacturers), you can easily fall into the trap of installing very ineffective filtration. A filter with a 'rating' but without the published removal efficiency % ... is simply an UNKNOWN and definitely not to be trusted to do the job you want to do .... at the so-called rating.
The standard for fuels and fuel oils: The OSU F2 test stand compares the log of influent particles versus effluent particles AT various retention µM sizes - also known as the Beta Ratio Removal Efficiency. What I gave was the 15µM **98%** (wt.) removal rating - the same (still nominal) rating of 15µM that would be defined by the 'front line' fuel filter manufacturers such as ParkerHannefin/Racor etc. - very little 'slight of hand' and 'filter jargon' from the front line manufacturers.

According to most engine builders, etc., the most damaging particle size in an IC engine (fuel) is in the range of ~20µM.
I suggest you call back to Yanmar and ask for their REMOVAL EFFICIENCY (wt.) % AT the µM rating. If they dont tell you this % removal efficiency, then you are definitely speaking to someone who has NO IDEA of what they are talking about. (Take this from someone who has been deeply involved in 'filtration' for the past 40 years with the front-line (and better) manufactures as clients, as an employee - engineer/scientist, as employer, distributor and consultant.)

Your statement of "... but I keep a fairly clean tank. ... is MORE important than the usage/selection of filters !!!!!! A (well designed) filter will only do the job that is intended ... retaining debris. If you have a CLEAN tank then the debris will be at an absolute minimum and the filters will have a very small job to do.

 

[ronbo]

There continues to be the misconception that the secondary filter is always 2 microns. Maybe on some engines but as mentioned by knowledgeable people here, that's not always true. In fact, according to Westerbeke in Marysville my 82B has a 25 micron filter. A little hard to believe but that's what they emailed me. Perhaps someone can confirm or refute.

Ronbo