Fuel Filters ???

[Anonymous 121765]

Guys,

I have a Universal (Westerbeke) 3M20A engine, about 15 years old.
I have bought my fuel filters from NAPA for years now. But, my last fuel filter change out brought up some questions.

My primary fuel/water separator is a Racor, is a 10 micron filter.
FROM THERE IT GOES INTO AN OLDER BARREL TYPE OF FUEL PUMP.
My friend who has an older 25XP has the same filtration setup.

My question is this:

If my fuel goes thru a 10 micron filter, than to the fuel pump (which my friend says is a 7.4 micron basket screen), then onto the secondary filter to the injectors, why is my secondary a 10 micron also. Seems to defeat the purpose.

My background is in process piping design. The thinking thusly is that when filtering, you use a step-down approach. So, lets follow the flow:

The primary is a fuel/water separator, complete with a water draw-off @ 10 microns. From there it hits the suction side of what I found was an older model fuel pump.

My friend Len said the basket filtration is 7.4 microns. Yes, this is a step-down in filtration. NAPA, (8) years ago said that the change out filter in the downstream (secondary filter #3390) was a 2 micron filter.

I did further research today & found out this was incorrect. The #3390 NAPA filter was a 10 micron filter, so let's recap.

My existing filtration system is a 10 micron in the primary filter to my fuel pump (@ 7.4 microns+/_ ? filter) on to my secondary filter at the pressure side of my fuel filter (#3390, a 10 micron filter) running to my injectors.

What's wrong with this setup???.......if at all.

I've hadn't had any problems with my fuel pump basket screen, and my secondary filter during changeouts. When cut in half the secondary filter shows clean. WTF?

I would just like to know why this is different from how industry applies to filtration. I was taught that stepdown filtration system work. The only thing I can think of is possibly low flow rate.....DUH

Any suggestions, I can't wait for the replies...............

CR

 

[kloudie1]

Ron, check the model/part number of the pump.. I doubt that the pump screen is as small as 7.4 microns .. Not saying that your number is wrong, just that I have never seen a screen type that was that fine. It is probably a good bit bigger than 10 micron.. I believe your observation is a good one.. the primary would serve you better at 20 micron with the secondary being 10.. Since filters get more efficient as they get dirty, the primary is probably catching lots of stuff and you are probably not using the secondary much at all. I think Rich has some experience with filtering processes and will provide some good info.

 

[RichH]

I doubt very much that your 'screen' is 7.4µM, as such 'metal membranes' are exceedingly expensive and very flow restrictive, such screens are usually in the range of 50-150µM, your's probably' is 74µM.

Filtration such as fuel filtration is not a screen door, the filter only remove a % of particles at their 'rating'. So, if the primary filter is 'passing' 5-10% of the particles at its 'rating', then the next in series at the very same 'rating' will have a higher statistical potential to remove the remaining particles - kind of like raking leaves with bamboo rake in which you dont get all the leaves on the first stroke of the rake but the second and third passes of the rake eventually get most all of the leaves.
Also, the second filter in the series acts as a 'guard' in case the first filter has a 'breakthrough' of particles --- it happens.
Third reason is that most contamination in diesel fuel is 'soft' and 'deformable' particles that under increasing pressure across a filter will tend to 'extrude' through the first filter; and, even if the 'extrusions' are much smaller than the rating of the second filter, many/most will be captured by the second filter.

Usually the 'last' filter in most engine 'set ups' is a very small surface area filter but with its 'rating' at up to 2 or 3X the rating of the upstream filter. Being small in surface area the speed of the fluid through the 'pores' will be 'fast' so when there is a 'break-through' occurring in the 'upstream' filter, the small downstream will quickly 'choke' or 'blind off' with particles; hence, stopping the fuel flow ..... These 'small' engine mounted filters shouldnt really be considered 'filters'; its much better to consider them as a "FUSE".

 

[Chris Patterson]

I think my Westy sounds a lot like yours, and for sure I wondered about that screen. It sure didn't appear to be doing much, but I can certainly see where it might catch the shrapnel if the Racor pukes.
(I use a R24T 10m primary).

 

[ggrizzard]

Rich, I'm in the same boat with Capn Ron. First filter is racor 10 micron, (Though they're getting harder to find at WM and the other local suppliers in the size that fits my very old racor model). So, as a "Simple Man", please confirm that when I run this set up with a NAPA 10 micron secondary filter, Am I doing OK, or Fair or 'it's a crap shoot'!

Thanks for the thread guys. G.

 

[Anonymous 121765]

Guys,

I checked with my pal Len, & he said it was 74 microns. I assumed he meant 7.4.
So my bad.

One other thing different, is that Len has a nice '87 Newport 30. His primary fuel filter is a 2 micron. I do believe his Newport manual has it @ 2 microns. This is partly why I ended up posting this thread. I always assumed that a 10 micron should be first in line then maybe a 2 micron secondary.

Kloudie & Rich saw the fuel pump screen size was wrong. I do like their input, as they know more about the filtration application here than I. Chris, & Ggrizzard are questioning the screen rating also.

I'm not as concerned with pump filter size, but if my having two 10 micron filters inline ok as . Remember I thought I was using a 2 mic secondary filter for years from NAPA (the ones who said the #3390 was a 2 micron).

So, is using a 2 mic filter OK in the secondary or would that put a load on the pump. If I remember, the orig. secondary filter was a 2 mic. I will put in a call to Westerbeke & let you all know what they recommend. This may FUEL further debate (no pun intended).

And, it only started out as a simple filter changeout. Question everything I always say.
Also, thanks for the input guys.

CR

 

[Stu Jackson]

Ron, this subject is like anchors and religion.

Here's my take:

1. You got it right having the primary in front of the fuel pump.
2. The fuel pump filter does pretty much squat, although if it was before the primary it'd would get crudded up first.
3. Primary / secondary filter "concept" industrially is usually coarse, fine, finer... On my boat, I've chosen to use a finer filter or an equal filter to the engine mounted secondary. Why? Because it's simply a hell of a lot easier to change the primary than the secondary filter, and I need only change the secondary every twice time do the primary. It's as simple as that.

I keep a log of when I need to change. I, too, have found the secondary clean even doing it this way.

Your boat, your choice.

Here's some more, read the links in my Reply #1:

http://c34.org/bbs/index.php/topic,7378.0.html

 

[Windborne]

Since my buddy Capt Ron has invoked my name a couple of times I'll join in. I have kept my fuel line system the same as it was since buying my boat a few years ago. First stop from tank is Racor R12S 2-micron, then fuel pump, original Universal 74 micron, then to secondary. Not sure if secondary is Universal which would be 2 micron or Napa replacement 3390 10 micron.

Either way, my Racor does all the work. Fuel pump and secondary filter remain clean. If 2 micron on Racor seems too small can only say I've had to change once a year as recommended and not more often.

Agree with Stu. Racor is easiest to get to and change so I'm happy letting it do all/most of the work.

Len Keller
Windborne
1988 Newport 30 MKIII
Madeira Beach, FL

 

[Anonymous 121765]

Stu,

Too funny man. But, you forgot to mention "politics" as well.

Just got off the phone with Westerbeke.
The secondary filter they use is a P/N 298852. This is 2 microns.
All the universals use the same filter.

So, I was correct in assuming this, but I had bad NAPA info. They said yesterday that they DON'T make a 2 micron with this thread size. They did say that it was a
20mm x 1-1/2 thread.

I am going to stay with this 2 micron filter, albeit the next changeout.

Thanx guys.

CR

 

[RichH]

CapnRon

I forgot to comment on your 'step down' approach .... filter geeks call this pre-filter / final filter filtration; and, without investigating real test data on the actual fluid to establish the actual particle size distribution.
Pre - final filters are usually selected thus: The final filter is usually selected first for flow rate with 'decent' flow rate verse 'differential pressure' output (gpm/psid), then the same surface area filter is selected at 3 to 5 times the µM rating of the final filter. This is done for service life extension of the usually more expensive final filter. The 3-5X larger µM filter will begin to remove most particles at that 'rating' but will also remove a small percent at the final filters µM rating. IN nature the smaller the particle size the 'exponentially' more number of them present. This leaves the final filter fairly 'unchallenged' with respect to the 'total load' of particles and in most cases of 'hard particles' can result in the 'set' staying online 3 to 5 times longer than when using 'just' a final filter.

Also typical and without 'actual' test data evaluation, the final or smallest µM retention filter, is usually chosen to be 1/5 of the size of the smallest orifice 'equivalent' in the system, as particles can and will 'clump' together and 'bridge' across fine orfices. History shows that removing all particles that are 5 times smaller size than the 'orfice' size effectively removes the potential for 'bridging' / blocking orfices. Most diesel injectors have an 'equivalent' orfice size of ~50µM, hence the standard recommendation of using a 10µM.

The Racor division of Parker, has been doing fuel filtration since Mathusala was a 'pup'. IN diesel fuel theyve determined over many years of 'typical' pariticle contamination (mostly fungus) that 30µM --> 10µM ---> 2µM (final filter) ---> ~15µM (small engine 'guard' filter or what I call a 'fuse' filter) is the absolute best. However, the SAE has determined that the 'most damaging' µM size in a diesel engine is 20µM, therefore there is usually NO need for the 2µM (great 'overkill' and 99.9% not needed); and besides and remembering that there are exponentially MORE numbers of particles the lower you go in µM size and which would unnecessarily overwhelm the filtration , the 2µM is usually omitted because it takes five times MORE of surface area of a 2µM to equate to the operating flow characteristics of a 10µM AND since most particles in diesel fuel are 'soft and deformable' such teeny 2µM particle will require a HEAVY load onto the lift pump (premature failure?); and, are vulnerable to 'extrude' through the 2µM because of the usually high pressure drop 'through' the 2µM.
Simple answer here regarding 2µM: use a 2µM IF AND ONLY IF your engine manufacture SPECIFIES a 2µM .... most do not.

So the 'typical' is 30µM (if the system has a 'history' of being contaminated with 'hard' particles) ---> 10µM ----> 15-17µM (small engine 'guard' or 'fuse') in case the upstream filters fail, have a (rare) pleat rupture and/or particle 'breakthrough'.
Racors typically have a 'removal retention efficiency' of ~95-97+% (wt) at the 'rating' µM.

Unless your engine mfg. specifies 2µM, the 'smallest' filter in your system should be 10µM, ...... even one 10µM, followed by another 10µM

 

[Anonymous 121765]

Rich,

Thanks, that's a great line of thought man. So what Westerbeke has told me makes sense. I knew it was a good idea to post my filter questions. I was also worried about the step-down filter flow rates being a problem if my assertion was wrong.

CR

 

[Stu Jackson]

The only thing, though, to consider is what Rich also mentioned, kinda in passing: flow rates. The flow rate of the standard Racor filter that most of us use, the R12 or R24 variety, is VASTLY higher than the actual flow rates of the engines we use.

 

[jviss]

http://forums.sbo.sailboatowners.com/showthread.php?t=96168&#post529691

 

[redhead78]

Ron with my new beta 35, i was told by my dealer, 30 micron in my raycor 500 secondary,which is a cartridge in a glass body, then the primary on the engine is a 10 micron, screw in type. So far ok..Red

 

[jviss]

I'm pretty sure the Kubota tractors, from which many of these engines come, my Universal M25 included, use a 20 micron secondary filter.

In addition, the water trapping and filtration in the Racor or Dahl primary filters are two separate functions. The filter could not possibly trap water, since a liquid water molecule is about .0001 microns in size. I don't know how the water in these filters trap works.

 

[RichH]

I don't know how the water in these filters trap works.

Simple gravimetric settling to the bottom of the filter bowl/sump.
You can take an empty filter housing (bowl down, head up, in/out connection on top) and use it to trap water ... the water will wind up in the lowest portion of the housing - called a water 'knock-out pot'.
Do the same thing with the filter housing reversed (bowl on top, in/out on the bottom etc.) and you now have an air 'knock-out pot'.

Some 'advanced tech' filters use a large pore hyrdophobic membrane (TYVEK/TYPAR/PTFE, etc) that affects the separation of fluids .... the water doesnt pass through the hydrophobic membrane/media and is diverted to a sump but the oil passes right on through.

 

[Stu Jackson]

I'm pretty sure the Kubota tractors, from which many of these engines come, my Universal M25 included, use a 20 micron secondary filter.

After over 25 years with our C34 Association, the best information we've been able to "discover" is that the Universal secondary filter is "somewhere between 10 and 15." Ron Hill, our technical guru, who has been contributing to our mail list (since 1988) and then the message board (since 2001), has posted that a number of times. It seemed also to be confirmed by Maine Sail in the link you provided earlier.

Guys, this simply isn't rocket science, no matter how many times it comes up, at least for our Universal/Kubota engines. The secondary is between 10-15, 'cuz that's what you get if you use a Universal replacement, and pretty much what all the equivalents are unless you go looking for something else.

Soooo, the ONLY choice left to YOU as a skipper is this:

"Do I want a 2, 10 or 30 micron primary filter?"

This pretty much cuts to the chase. Thanks to Rich for the details, which I'm sure he's tired of retyping.

Your boat, your choice!

 

[jviss]

Simple gravimetric settling to the bottom of the filter bowl/sump.
You can take an empty filter housing (bowl down, head up, in/out connection on top) and use it to trap water ... the water will wind up in the lowest portion of the housing - called a water 'knock-out pot'.
Do the same thing with the filter housing reversed (bowl on top, in/out on the bottom etc.) and you now have an air 'knock-out pot'.

Some 'advanced tech' filters use a large pore hyrdophobic membrane (TYVEK/TYPAR/PTFE, etc) that affects the separation of fluids .... the water doesnt pass through the hydrophobic membrane/media and is diverted to a sump but the oil passes right on through.

Gravimetric? I understand what you mean, and having studied chemistry I know what gravimetric means, and there's nothing 'metric' about this. I think you mean "simple gravity settling...."

I guess this assumes that the amount of water introduced to this filter is much less than the volume of the filter?

 

[Jan11]

Just got off the phone with Westerbeke.
The secondary filter they use is a P/N 298852. This is 2 microns.
All the universals use the same filter.

So, I was correct in assuming this, but I had bad NAPA info. They said yesterday that they DON'T make a 2 micron with this thread size. They did say that it was a
20mm x 1-1/2 thread.

I am going to stay with this 2 micron filter, albeit the next changeout.

Thanx guys.

CR

Not meaning to start a war, BUT... All Universal diesels use the same fuel filter which is the 298854 filter which is 25u. This crosses to Wix 33390 (NAPA 3390) which is 10u and has a 20mmx1.5mm thread.

This from Westerbeke in 2009:
10 microns for the on engine spin on filter is fine. Do not go any smaller in micron rating. Our #298854 spin on is rated at 25 micron. Stay with 10 micron in the Racor as well. You want the Racor to be doing the majority of filtering.

Kind Regards,

Westerbeke Corp.


The 298852 filter is a lube oil filter replaced by 299381 according to Torresen which is a nominal 21u and 3/4"x16. http://shop.torresen.com/ships_store/?p=details&mfc=Universal&sku=299381&sectionid=

 

[RichH]

Not to start a war either; but, you have to know the 'super-secret handshake' before you compare µM ratings between the various filter manufacturers, etc.

a µM 'rating' without a statement of the removal efficiency at that 'rating' is meaningless.

a *µM absolute* rating or *µM 100%* rating means 'essentially all' particles at that 'rating' are removed.

a *µM nominal* rating is meaningless unless presented as *µM (95%)*, etc.

For the typical filter material used in fuel filtration and similar 'coarse' filtrations, the exact SAME filter material can be rated as (example):
25µM 'absolute'
25µM 100%
3µM (97%) or 3µM 'nominal'
1µM (70%) or 1µM 'nominal'
0,1µM (25%) or 0,1µM 'nominal'
,,, etc. .
.... for the same exact filter material, but different 'ratings' by the manufacturer!!!!!

So, when speaking about filters, if someone gives you a rating as 20µM and nothing more .... that person usually has absolutely NO IDEA of what he/she is talking about.
Even Racor the world leader in in mobile fuel filtration also reports in its catalogues in this 'undefined' manner ..... but if you search further in the fine print of their 'tech manuals' ... "all filters are 'nominally' rated at 97-98% (wgt.) removal efficiency unless otherwise stated", etc.
Beware of a filter rating such as 10µM ... that doesnt include that 'qualifier' ... nominal, %, absolute, etc. ... or some fine print statement in an accompanying 'tech manual'. There's lots of 'shysterism' in the filtration industry, especially when applied to 'cheap' stuff, unless you know 'filter-speak' or are aware of the 'super-secret handshake'.


Other
FWIW - Gravimetric Settling is a universally and long known means of the separation or assay/analytical. separation, segregation, classifying, or sorting methodology in 'chemistry' involving the use of gravity for the separation, etc. of 'solids from liquids' and 'liquids from non-miscible liquids', etc. when the components have different 'specific gravities'. ;-)