As part of my trying to get smarter than I am (not hard!) about fuel
and oil issues, in the course of searching for info about the
oil-change-into-fuel-tank issue, I stumbled on discussions of fuel
polishing.

Our setup is now such that the pump is the last thing before it returns
- it sucks through the two filters in series, with the vacuum gauge in
between the pump and the filter line, drawing the fuel from the same
supply point as the engine. We have two honking big 30 and 10 (in
series) micron filters driven by a 3.5gpm Walbro pump, and monitored
with a gauge, for the polisher. I've run that enough, now (at the
slip, so no slosh, yet) to have circulated the fuel several hundred
times. No change in the vac gauge, yet.

I debated doing a separate feed, but decided that getting the fuel from
the same point as the engine in the tank would have the best likelihood
of making sure that what the engine pulled would have first been
polished.

That's because - as above - I'll have run the polisher excessively, as
well as all the time the engine is running, plus any time the batteries
are charged and we're sailing, as the wind generator will more than
take care of that load (.8A), and it's pulling from the same point, at
least somewhat assuring that that point will get lots of fuel flow, and
by extrapolation, said fuel will have been through the filters many
times.

However, I'm scratching my head a bit about filter sizes. In one of
the threads I read, it was observed that a 30 micron filter will also
catch many smaller particles, and ditto the 10. After enough passes,
effectively, it appears that the fuel will be down to something on the
order of 2 microns, perhaps even less.

One of the assertions I've recalled seeing in the past (not that it
showed up in this recent search) was that multiple passes, as the
filters eventually started filling with catch product, yielded finer
filtration as time went on. That makes sense to me - I suspect the
only problem would be how fast the filter got so full as to inhibit
transfer through it. In my case, the filters are very big - the cases
are 3.5x11 inches - so I expect it will take a very long time to cause
the vacuum to rise enough to warrant a change.

So, I'm wondering if that postulate is right - that lots of running
will make my tank have a net particulate of only tiny (relative, of
course!) size? Other commentary in the past showed very extended
standard filter changes with this sort of arrangement, apparently as a
product of this polishing.

I have this dual Racor setup, as well. I have only the filter which
came in the new one (10), and some spares of the original on the boat
(30), plus a spare of the engine filter (2). I'm about to buy spares
for all of these as part of our provisioning.

So, more head scratching, from a very long-ago thread in this space,
someone suggested 2 was appropriate. Certainly, with the dual setup I
have now, swapping over and doing a filter change is easy - much easier
than changing the engine filter (2) and repriming, etc. I had been
going to do 10s in the Racors, on the presumption that the polishing
had reduced it to that level, and likely I'd never have to change them,
anyway. However, if all the above is right, perhaps I'd be better off
with 2s, on the likelihood that even those would not likely need
changing very often, having had the fuel polished to that or better
levels, already, by the time it got there.

So, two questions from all this.

1) Is my polishing setup appropriate - is the 30 followed by the 10 a
good practice?

2) For those who have done it, or if there's still a professional
filtration person looking into this group who can give empirical
commentary vs usage experience, will I be changing 2s in the dual Racor
setup often, or will the polishing likely reduce the particulate to
that or below?

And, doing a Columbo, thinking of something I forgot...

I also have an electric priming pump, operated by a momentary push
switch. However, when we bought the boat, it was next to the engine,
after, not before, the Racor. Logic suggests it should be in front of
the Racor, to refill it, before priming, rather than sucking all that
air into the system. Or, is that not a problem? I've never changed a
Racor, so I don't know what's really involved, but I can say for sure
I'm not enthusiastic about having to pour fuel into the body as is
suggested in the instructions.

My apologies for asking what might be stupid newbie questions - but
I've had the good fortune never to have to deal with a stopped diesel
engine, and would like to keep it that way. A very well equipped tool
kit is just fine with me if it never leaves the locker...

Thanks for putting up with me - likely there will be a flurry of this
sort of thing as we approach, and then do, our sea trials...

L8R

Skip, installing and filling more engine stuff so we can fire it up and
service it soon...

Morgan 461 #2
SV Flying Pig KI4MPC
See our galleries at www.justpickone.org/skip/gallery!
Follow us at http://groups.google.com/group/flyingpiglog and/or
http://groups.yahoo.com/group/TheFlyingPigLog

"Twenty years from now you will be more disappointed by the things you
didn't do than by the ones you did do. So throw off the bowlines. Sail
away from the safe harbor. Catch the trade winds in your sails.
Explore.
Dream. Discover." - Mark Twain

On 20 Nov 2006 19:47:14 -0800, "Skip Gundlach"
wrote:

So, two questions from all this.

1) Is my polishing setup appropriate - is the 30 followed by the 10 a
good practice?


It can't hurt but is probably overkill. I polish through my regular
Racors with 10 micron elements. It seems to work OK, no hard data but
I've had no fuel issues since I started doing this.

2) For those who have done it, or if there's still a professional
filtration person looking into this group who can give empirical
commentary vs usage experience, will I be changing 2s in the dual Racor
setup often, or will the polishing likely reduce the particulate to
that or below?

There has been a big ongoing debate on one of the trawler lists
regarding this question. Most engine manufacturers, including
Cummings and Cat, are recommending 10 micron elements in the Racors
followed by a 2 micron engine mounted filter. Since the engine
mounted filter is frequently much more difficult to change, some have
advocated 2 micron elements in the Racors on the assumption that the
engine mounted filters would then last more or less indefinitely. The
manufacturers have countered that the engine mounted filter should be
changed on its recommended schedule regardless. I have come full
circle and gone back to 10 micron elements in the Racors.

Although you sound like you've done all the right things, I'd offer
one word of caution. Fuel problems often do not occur until the boat
starts moving around and stirs up sediment accumulated in the bottom
of the tank. This is almost impossible to address with dock side
polishing so I'd recommend extra filter and vacuum guage vigilance the
first few times you go out, especially in rough conditions. If you
can run your polishing system while underway in rough conditions, that
should speed the cleaning process. Don't forget to use a good fuel
conditioner in the recommended quantities. I've been using mostly
Biobor and it seems to work.

Regarding your other question on filter changes and filling the Racor
cannister with fuel; it depends on the boat. If your tanks are below
the level of the Racors, then you will need some way of topping off
the filters after you change out the element. On my boat the tanks
are higher so it is not a problem. I just crack open the inlet valve
while watching the fuel level in the cannister.

Hi, Wayne, and thanks for the lengthy response.

Wayne.B wrote:

There has been a big ongoing debate on one of the trawler lists
regarding this question. Most engine manufacturers, including
Cummings and Cat, are recommending 10 micron elements in the Racors
followed by a 2 micron engine mounted filter. Since the engine
mounted filter is frequently much more difficult to change, some have
advocated 2 micron elements in the Racors on the assumption that the
engine mounted filters would then last more or less indefinitely. The
manufacturers have countered that the engine mounted filter should be
changed on its recommended schedule regardless. I have come full
circle and gone back to 10 micron elements in the Racors.

Although you sound like you've done all the right things, I'd offer
one word of caution. Fuel problems often do not occur until the boat
starts moving around and stirs up sediment accumulated in the bottom
of the tank. This is almost impossible to address with dock side
polishing so I'd recommend extra filter and vacuum guage vigilance the
first few times you go out, especially in rough conditions. If you
can run your polishing system while underway in rough conditions, that
should speed the cleaning process. Don't forget to use a good fuel
conditioner in the recommended quantities. I've been using mostly
Biobor and it seems to work.

I'd commented many times privately, but forgot to include it in my note
here, that I was hoping for some really snotty sailing in our sea
trials, during which time the polisher would be running all the time,
for just that reason. As little as it draws, likely I'll be running it
non-stop during nearly any of our sailing. Unlike another poster in
one of the threads I researched, I'll not have it connected to the
ignition but rather maintain the ability to control it separately, but
expect to have it operating any time the engine's turning, as the
alternator will keep up with whatever draw is happening.


Regarding your other question on filter changes and filling the Racor
cannister with fuel; it depends on the boat. If your tanks are below
the level of the Racors, then you will need some way of topping off
the filters after you change out the element. On my boat the tanks
are higher so it is not a problem. I just crack open the inlet valve
while watching the fuel level in the cannister.

My filters are about 2' above the tank, unfortunately. Thus the
question about using the priming pump as filler. Certainly, it would
suck the fuel, if the top was closed - but I don't know if that would
just leave some air in the top, or if that air would be sucked into the
system. With the priming pump before the filters, I could fill the
canisters before closing them, and *then* do the prime sequence if
needed. Of course, if I'm changing by just shutting/changing the
valve, going to the other filter, the lines would stay full, and the
only thing I'd be dealing with would be the racors.

I *do* have the polishing filters equipped with drain valves, so could
draw fuel from those to fill the Racor in question. However, I'd have
to hope I got the right amount, so I wouldn't have to deal with any
excess or shortage. Hm. Looks like I'll be re-mounting the pump
upstream of the Racors...

Or, any reason not to??

More "hmmm..." - perhaps I could put a line on the end of the 10micron
polishing filter valve, mounted above the Racors (see the November
gallery) and use that as my fill medium. That might solve both
problems...

Thanks...

L8R

Skip, back to the engine room in the cold rainy weather (had to put on
jeans, today!)

Morgan 461 #2
SV Flying Pig KI4MPC
See our galleries at www.justpickone.org/skip/gallery!
Follow us at http://groups.google.com/group/flyingpiglog and/or
http://groups.yahoo.com/group/TheFlyingPigLog

"Twenty years from now you will be more disappointed by the things you
didn't do than by the ones you did do. So throw off the bowlines. Sail
away from the safe harbor. Catch the trade winds in your sails.
Explore.
Dream. Discover." - Mark Twain

Skip Gundlach wrote:
My filters are about 2' above the tank, unfortunately. Thus the
question about using the priming pump as filler.

If the polishing system is totally seperate from the engine
fuel feed, you can't. But you could connect the discharge of
the polishing pump to the upstream side of the engine
filters and use that to prime the system. Put in a needle
valve so you can throttle the flow.

This could also be a big help spotting air leaks in your
fuel feed line. Happens often and can be very frustrating.

DSK

On 20 Nov 2006 19:47:14 -0800, "Skip Gundlach" wrote:

I'd do the separate feeds. A friend of mine had one feed going to his heater and
engine and somehow that got air in the engine line. Would you believe a Hans Christian?

moral of this story was separate feeds and check your anchor for easy deployment
before shoving off. an electric fuel pump plumbed in for bleeding would have sped up
the job too. he won't even sail with me now unless I check the anchor before we
leave the dock.

I'd err on the side of caution.


I debated doing a separate feed, but decided that getting the fuel from
the same point as the engine in the tank would have the best likelihood
of making sure that what the engine pulled would have first been
polished.

I can add nothing to the debate on filter size, but I run two fuel tanks and
a seperate day tank in the engine room. I have a high volume fuel transfer
system with an inlet and outlet manifold. Each manifold has 3 ball valves.
Between the manifolds I use two RACORs with a strainer and a ten micron
filter.This allows transfer from and to any tank. Additionally, the day tank
is slightly higher than the engine and generator, which allows self priming.
Steve

"Skip Gundlach" wrote in message
ups.com...
As part of my trying to get smarter than I am (not hard!) about fuel
and oil issues, in the course of searching for info about the
oil-change-into-fuel-tank issue, I stumbled on discussions of fuel
polishing.

Our setup is now such that the pump is the last thing before it returns
- it sucks through the two filters in series, with the vacuum gauge in
between the pump and the filter line, drawing the fuel from the same
supply point as the engine. We have two honking big 30 and 10 (in
series) micron filters driven by a 3.5gpm Walbro pump, and monitored
with a gauge, for the polisher. I've run that enough, now (at the
slip, so no slosh, yet) to have circulated the fuel several hundred
times. No change in the vac gauge, yet.

I debated doing a separate feed, but decided that getting the fuel from
the same point as the engine in the tank would have the best likelihood
of making sure that what the engine pulled would have first been
polished.

That's because - as above - I'll have run the polisher excessively, as
well as all the time the engine is running, plus any time the batteries
are charged and we're sailing, as the wind generator will more than
take care of that load (.8A), and it's pulling from the same point, at
least somewhat assuring that that point will get lots of fuel flow, and
by extrapolation, said fuel will have been through the filters many
times.

However, I'm scratching my head a bit about filter sizes. In one of
the threads I read, it was observed that a 30 micron filter will also
catch many smaller particles, and ditto the 10. After enough passes,
effectively, it appears that the fuel will be down to something on the
order of 2 microns, perhaps even less.

One of the assertions I've recalled seeing in the past (not that it
showed up in this recent search) was that multiple passes, as the
filters eventually started filling with catch product, yielded finer
filtration as time went on. That makes sense to me - I suspect the
only problem would be how fast the filter got so full as to inhibit
transfer through it. In my case, the filters are very big - the cases
are 3.5x11 inches - so I expect it will take a very long time to cause
the vacuum to rise enough to warrant a change.

So, I'm wondering if that postulate is right - that lots of running
will make my tank have a net particulate of only tiny (relative, of
course!) size? Other commentary in the past showed very extended
standard filter changes with this sort of arrangement, apparently as a
product of this polishing.

I have this dual Racor setup, as well. I have only the filter which
came in the new one (10), and some spares of the original on the boat
(30), plus a spare of the engine filter (2). I'm about to buy spares
for all of these as part of our provisioning.

So, more head scratching, from a very long-ago thread in this space,
someone suggested 2 was appropriate. Certainly, with the dual setup I
have now, swapping over and doing a filter change is easy - much easier
than changing the engine filter (2) and repriming, etc. I had been
going to do 10s in the Racors, on the presumption that the polishing
had reduced it to that level, and likely I'd never have to change them,
anyway. However, if all the above is right, perhaps I'd be better off
with 2s, on the likelihood that even those would not likely need
changing very often, having had the fuel polished to that or better
levels, already, by the time it got there.

So, two questions from all this.

1) Is my polishing setup appropriate - is the 30 followed by the 10 a
good practice?

2) For those who have done it, or if there's still a professional
filtration person looking into this group who can give empirical
commentary vs usage experience, will I be changing 2s in the dual Racor
setup often, or will the polishing likely reduce the particulate to
that or below?

And, doing a Columbo, thinking of something I forgot...

I also have an electric priming pump, operated by a momentary push
switch. However, when we bought the boat, it was next to the engine,
after, not before, the Racor. Logic suggests it should be in front of
the Racor, to refill it, before priming, rather than sucking all that
air into the system. Or, is that not a problem? I've never changed a
Racor, so I don't know what's really involved, but I can say for sure
I'm not enthusiastic about having to pour fuel into the body as is
suggested in the instructions.

My apologies for asking what might be stupid newbie questions - but
I've had the good fortune never to have to deal with a stopped diesel
engine, and would like to keep it that way. A very well equipped tool
kit is just fine with me if it never leaves the locker...

Thanks for putting up with me - likely there will be a flurry of this
sort of thing as we approach, and then do, our sea trials...

L8R

Skip, installing and filling more engine stuff so we can fire it up and
service it soon...

Morgan 461 #2
SV Flying Pig KI4MPC
See our galleries at www.justpickone.org/skip/gallery!
Follow us at http://groups.google.com/group/flyingpiglog and/or
http://groups.yahoo.com/group/TheFlyingPigLog

"Twenty years from now you will be more disappointed by the things you
didn't do than by the ones you did do. So throw off the bowlines. Sail
away from the safe harbor. Catch the trade winds in your sails.
Explore.
Dream. Discover." - Mark Twain

In article . com, Skip
Gundlach wrote:

So, two questions from all this.

1) Is my polishing setup appropriate - is the 30 followed by the 10 a
good practice?
This is probable great overkill and will reduce the overall efficiency
of the 'turnover' of the recirculation system. A recirculation
polisher is effective because it can 'turn-over' or pass a LOT of fluid
through the filter set - depending on capture by all the capture sites
in the filter media that are much smaller that the 'rating'. Adding
'sequential' filters will drastically reduce the recirculation volume
..... and the system will take MUCH LONGER to turnover and down to
'acceptable' resident particles in the tank (a 'mathematical anomoly'
of recirculation filtration).



In a high turnover recirculation system, adding additional filters will
add flow resistance which will slow down the 'turnover'. A nominally
rated 10uM filter is probably closer to 30uM on an absolute basis, plus
the 10uM filter will have smaller diameter cellulosic fibers than a
30uM nominal. I'd go with the 10uM nominally rated filter even though
a 10uM filter will have approximately 1/3 the flow capacity of a 30uM.
(Cavaeat: if the system is fouled or if you havent cleaned the tank in
some time ----- indications a repetetive plugging of the main line
racors, etc. and you're too lazy or cant clean the tank--- then use a
30uM to 'hog' the system down to low particle levels THEN use the 10uM
to clean-up further. If you use a 30 immediately followed by a 10 it
will probably take 10 times as long to do the same job as when you use
'single' filters in a recirc. loop. .... unless you have a 'humongous'
pump to do all the 'work'.
Id also do this in an independent loop being careful to discharge the
recirculation loop near the bottom of the fuel tank or directly onto a
side wall to minimize 'whipping up a froth' of air-oil bubbles.
Obviously air bubbles being entraned into the main fuel line will
eventually separate into large bubbles and eventually 'stall' the
engine or fuel system .... 'flooded discharge' from a recirculation
system is a 'necessity' or you may have to put in a 'air bubble trap'
on the main fuel line. Keep it simple and be sure of a flooded
discharge or alternatively discharging onto the tank wall.

Filter 'ratings' in such 'fuel' filters are extremely 'arbitrary' and
usually NO realistic connection to the 'actual' removal of the filter
!!!!! Even the technically superior Racors are probably no more than
95% efficient at their 'rating'. .... meaning they can pass a
'basketball sized' particle and still be honestly rated at whatever you
but ..... the rating is '% weight removal' at the designated particle
size.

Recirculation filters should be set up as PRESSURE FEED not vacuum feed
where the pump is at the END of the circuit ..... the filters will be
vastly more efficient versus on-stream service life due to the better
deposition of particles ON the filter surface than IN the filter when
in vacuum feed mode. The Walbro has an integral screen of about
100-200uM so you dont have to worry of large particles harming the
pump; although, you must remember to clean the integral pump inlet
screen occasionally. Do NOT use compression fittings on a pressure
feed system single or double flared connection (or better) only .... in
fact you should probably replace ALL compression fittings ANYWHERE in a
fuel system as they ALWAYS eventually leak (air gets sucked INTO the
system on a leaky compression fitting when the system is in vacuum
mode) over time.

2) For those who have done it, or if there's still a professional
filtration person looking into this group who can give empirical
commentary vs usage experience, will I be changing 2s in the dual Racor
setup often, or will the polishing likely reduce the particulate to
that or below?
If the recirculation system is well designed and maintained you
probably NEVER will encounter ANY challenge of particles to the racors.
The recirculation system (if ON often or anytime the engine is running)
will keep the particle background in the tank to well below submicronic
levels thus no challenge to the Racors. Racors however willl
eventually fail due to being soaked by free or emulsified water
(causing 'digestion' of the cellulosic component of the filter media)
and 'flexure fatigue' of the pleats due to pulsations coming from the
mechanical lift pump on the engine.
Whats NICE about a recirculation system is that you can remove the
majority of 'crud' in very 'inexpensive' filters and keep a single
racor (and engine mounted 'last chance' or 'guard' filter) from
plugging. You dont need prefilters (primary) in a system that has an
adequate recirculation filtration system. In such a system you can
even run a 'hard line' bypass (no filter) when changing a plugged racor
as the fuel tank will have essentially ultra filtered oil and you can
run for sseveral minutes with this clean already filtered oil as you
change out the racor.
The dip tube of the recirculation should pick up the fuel at the VERY
bottom of the tank to ensure that youre down into the crud and water
thats usually in the bottom. The water can be removed in the
recirculation loop by simply adding and 'empty' filter housing and
letting the water 'settle out by gravity' in the empty housing, etc.
..... a clear plastic 'tail' tube with a valve on the bottom of the
empty filter housing will show when there is water in the empty
'knock-out' pot.

The better you filter the tank contents removes the submicronic
particles that are the nucleation sites upon which larger and large
particles 'grow'/aggloerate. Stands to reason if you continually
remove these very small particles ... then you will have infinitely
less particles growing. The caveat here is that you still have to get
inside the tank every few years and clean out all the crap thats stuck
to the walls .... but not as often as if didnt have a recirculation
filtration system.

The best reason for having a high turnover recirculations system is
when due to degrading oil (cracked oil, or oil thats becoming fouled
with microorganism growth) and the crap has formed on the walls .....
even if the crap does break loose from the walls during a heavy sea
state the reciruclation will QUICKLY restore the tank back to low
particle levels. STill need to clean the tank occasionally.

The BEST way to operate the fuel system is to continuously MONITOR the
main fuel system filters with a vacuum or pressure gauge (measured as
pressure drop across the filter versus maximum engine rpm) ... so you
know WHEN to change the filters. Ditto on the recirculation system.
ALL filters should have an operational 'recommendation' of liters per
minute versus 'differential pressure' .... when the operating flow to
the engine is getting close (flow through the filter vs. what the gagte
is telling you - then its time to change the filter ---- READ the
technical specification that come with the filter or go to the filter
manufacturers website for the 'tech' / flow data. Be aware that the
tech data for flow vs. 'delta P' should be for *fuel oil* and NOT for
water --- big difference in flow/pressure requirements. If the tech
info is in 'water flow' contact the filter manufacturer and get the
'fuel oil' flow rating. Change the filters when the pressure/vac.
gage shows (versus the performance curve of the filter) that the flow
rate 'could be' 200-150% of flow of the engine demand at full throttle
..... look at the engine fuel consumption vs. horsepower curve and then
compare to the fuel filter(s) performance (flow vs. differential
pressure) curve. Size the filters based on the 'performance flow rate
vs. operational differential pressure curve .... NOT the maximum flow
rate on the 'box' .... when filters get dirty their flow begins to shut
down .... plan on it and know the gage pressure when you should change
the filter.
Not all the particles that a filter 'captures' are 'hard' particles;
many of the particles retained will be 'soft' particles and will begine
to 'extrude' through a filter if the differential pressure across the
filter becomes 'high'. Best is to maintain your own 'history' of
operation (make notes, etc.) and then stick to the maintenance & filter
changeout depending on YOUR operational history, etc..
No sense having ANY filter installed and not knowing WHEN to change it
...... other than having a stalled engine !!!!!!!!! Otherwise, you're
just throwing away good filters or risk stalling the engine (usually at
the worst possible time).

Before you add a recirculations system .... better to get inside the
tank and scrub out and mechanically remove all the crap .... then you
wont NEED all those expensive 'filters'. Filters only remove
'symptoms', the cause is usually a dirty tank or taking onboard
extremely dirty fuel.

When to NOT buy fuel: before pumping into the tank, take a clear
glass, pour some fuel into to it and hold the full glass between you
and a strong light. If there is any 'haze' to the fuel .... get your
fuel somewhere else. When to clean out the tank .... ditto with the
glass in front of strong light.

Hope this make 'sense'.
;-)

A 'DAY' tank is probably the BEST insurance for any fuel system. If
all hell breaks loose upstream (plugged filters, tank violently
'particulating', etc. ... all you have to do is open the vent on the
day tank lock out or isolate the 'trouble' and simply run for several
hours solely on the day tank .... until you can 'sort out' the problem.

My day tank is mounted well above th engine plane so I can still get
fuel oil by gravity feed even if the mechanical lift pump craps out.

Wow, Rich!

What a detailed response - I scarcely know where to begin...

Rich Hampel wrote:
In article . com, Skip
Gundlach wrote:

So, two questions from all this.

1) Is my polishing setup appropriate - is the 30 followed by the 10 a
good practice?
This is probable great overkill and will reduce the overall efficiency
of the 'turnover' of the recirculation system. A recirculation
polisher is effective because it can 'turn-over' or pass a LOT of fluid
through the filter set - depending on capture by all the capture sites
in the filter media that are much smaller that the 'rating'. Adding
'sequential' filters will drastically reduce the recirculation volume
.... and the system will take MUCH LONGER to turnover and down to
'acceptable' resident particles in the tank (a 'mathematical anomoly'
of recirculation filtration).


Is this the effective equivalent of what happens with resistors vs
capacitors in series and parallel? Putting these in parallel would
more than double the effectiveness, whereas in series diminishes the
effectiveness?



In a high turnover recirculation system, adding additional filters will
add flow resistance which will slow down the 'turnover'. A nominally
rated 10uM filter is probably closer to 30uM on an absolute basis, plus
the 10uM filter will have smaller diameter cellulosic fibers than a
30uM nominal. I'd go with the 10uM nominally rated filter even though
a 10uM filter will have approximately 1/3 the flow capacity of a 30uM.
(Cavaeat: if the system is fouled or if you havent cleaned the tank in
some time ----- indications a repetetive plugging of the main line
racors, etc. and you're too lazy or cant clean the tank--- then use a
30uM to 'hog' the system down to low particle levels THEN use the 10uM
to clean-up further. If you use a 30 immediately followed by a 10 it
will probably take 10 times as long to do the same job as when you use
'single' filters in a recirc. loop. .... unless you have a 'humongous'
pump to do all the 'work'.

Hm. I've never cleaned the tank - and nothing I got in the otherwise
pretty complete records suggests it's been done in the last 15 years.
For whatever it's worth, however, we had a very rough trip over when we
took possession and brought it 500 miles through the nasty conditions
in the Gulf, and had no issues whatever; the filter, while dirty, shows
no lumps or identifiable spots.

About the length of time to accomplish, I'm not sure I understand why
that should be so. I'm operating on the presumption, despite the
previous, that I have a lousy tank condition. The point of the 30
followed by the 10 is the presumption that I'll have crud which we'll
dislodge pretty quickly. The suction gauge shows a very low level of
suction, so I presume there's little obstruction. I don't know about
"humongous" as a pump, but it seems to be doing reasonably well so far
with the 30 followed by 10. I've not put a bucket under the output to
test what the actual volume is, but opening a small unused port on the
tank to see what's going on shows theres a notable amount of fuel being
moved.

Id also do this in an independent loop being careful to discharge the
recirculation loop near the bottom of the fuel tank or directly onto a
side wall to minimize 'whipping up a froth' of air-oil bubbles.
Obviously air bubbles being entraned into the main fuel line will
eventually separate into large bubbles and eventually 'stall' the
engine or fuel system .... 'flooded discharge' from a recirculation
system is a 'necessity' or you may have to put in a 'air bubble trap'
on the main fuel line. Keep it simple and be sure of a flooded
discharge or alternatively discharging onto the tank wall.

Hm, again. I don't have an easy means of doing the discharge you
suggest. Currently, the discharge is straight down - no tube, no
directional difference. The pickup is the same as the Racors, however
far down that is. We've never experienced (yet, of course -and all
this is in an effort to make sure we don't get the first) a clog in the
old (very rotted by the time I tore it out) fuel lines. However, an
inspection of the tank through that small port above showed no bubbles
evident. Dunno why, as it seems it should be happening, after many
hours of running the fuel through. The pump is evidently a diaphragm
variety, as initially it was very fast and noisy, but that was only
until it sucked up the fuel in the line and filled the filters,
whereupon it settled down very quickly to a very quiet pulsing sound -
so, perhaps that's why no froth?


Filter 'ratings' in such 'fuel' filters are extremely 'arbitrary' and
usually NO realistic connection to the 'actual' removal of the filter
!!!!! Even the technically superior Racors are probably no more than
95% efficient at their 'rating'. .... meaning they can pass a
'basketball sized' particle and still be honestly rated at whatever you
but ..... the rating is '% weight removal' at the designated particle
size.

Hm. Makes the toilet paper and paper towel type filter seem more
effective, doesn't it?


Recirculation filters should be set up as PRESSURE FEED not vacuum feed
where the pump is at the END of the circuit ..... the filters will be
vastly more efficient versus on-stream service life due to the better
deposition of particles ON the filter surface than IN the filter when
in vacuum feed mode.

I admit to being entirely unknowledgeable about all this, other than
what I thought I remembered from discussions on filtration over the
many years I've been looking at it, before having a real life
application of my own. What I *thought* I remembered was that you
absolutely didn't want to have pressure on the filters, but suction.
And, I presume there's some explanation in fluid dynamics or some such
of which I am likewise totally unaware, but I don't know why it should
be one way or the other. Is it that particles are being sucked *in*,
vs pushed *on*, the filter? And, in the case of Racors, why is it that
they have to be suction?

The Walbro has an integral screen of about
100-200uM so you dont have to worry of large particles harming the
pump; although, you must remember to clean the integral pump inlet
screen occasionally. Do NOT use compression fittings on a pressure
feed system single or double flared connection (or better) only .... in
fact you should probably replace ALL compression fittings ANYWHERE in a
fuel system as they ALWAYS eventually leak (air gets sucked INTO the
system on a leaky compression fitting when the system is in vacuum
mode) over time.

I'm pretty sure that's what I have - the nut is free to rotate after
it's loose but the nipple stays in place. Looking at it before putting
it on, the male is somewhat pointed, and the female is like the bell of
a horn, with the nut pushing it down on tightening. That's that I have
in all the connections of the hoses..


2) For those who have done it, or if there's still a professional
filtration person looking into this group who can give empirical
commentary vs usage experience, will I be changing 2s in the dual Racor
setup often, or will the polishing likely reduce the particulate to
that or below?

If the recirculation system is well designed and maintained you

Heh. Well, so far, it appears that it's not well designed - though it
meets all the various inputs I'd stored over many years while getting
ready for this point. I even had a couple of what looked like
professional designs in pdf. However, my recollection has you with
umpteen years in the filtration biz (recalling some of the endless
threads with jax and and perhaps some others), so my presumption is you
come from an industry perspective, rather than conjecture...

So, if I understand you correctly, I should either completely
disassemble my currently installed unit and start over, or, at a
minimum, reverse the flow, change the suction gauge for a pressure
gauge, and leave one of the canisters empty and, after lots of 30
filter hours, go to only 10 filter and replacements??

probably NEVER will encounter ANY challenge of particles to the racors.

That's encouraging, at least - the rest, so far, is very disappointing
(because I'll have to start over, and I have no easy means of cleaning
the tank)...

The recirculation system (if ON often or anytime the engine is running)

My intent and expectation is that it will be on any time the engine is
running, as well as any time we're sailing with full batteries (the
wind generator should more than keep up with the load, if there's
enough wind to be sailing). I'd assumed that would provide the very
best opportunities for clean fuel other than to have it running nonstop
(never mind how it's powered in that case...).

will keep the particle background in the tank to well below submicronic
levels thus no challenge to the Racors. Racors however willl
eventually fail due to being soaked by free or emulsified water
(causing 'digestion' of the cellulosic component of the filter media)
and 'flexure fatigue' of the pleats due to pulsations coming from the
mechanical lift pump on the engine.
Whats NICE about a recirculation system is that you can remove the
majority of 'crud' in very 'inexpensive' filters and keep a single
racor (and engine mounted 'last chance' or 'guard' filter) from
plugging. You dont need prefilters (primary) in a system that has an
adequate recirculation filtration system. In such a system you can
even run a 'hard line' bypass (no filter) when changing a plugged racor
as the fuel tank will have essentially ultra filtered oil and you can
run for sseveral minutes with this clean already filtered oil as you
change out the racor.

Well, that's comforting to know - though, having already made the
investment, and installed, a dual racor (change on the fly), I expect
I'll keep it. However, I'll also keep a very close eye on the bowls
for water. Currently there's the flame-arrest bowls with not only the
spin-off-the-bowl, but a plug in the bottom. I believe I'll trade the
plugs for a valved nipple so I can drain and check what's there without
the flood which would result in removing the flame arrestor, or even
just the plug...

The dip tube of the recirculation should pick up the fuel at the VERY
bottom of the tank to ensure that youre down into the crud and water
thats usually in the bottom. The water can be removed in the
recirculation loop by simply adding and 'empty' filter housing and
letting the water 'settle out by gravity' in the empty housing, etc.
.... a clear plastic 'tail' tube with a valve on the bottom of the
empty filter housing will show when there is water in the empty
'knock-out' pot.

So, as to the above, if I were to reverse this, the second, very large,
container could be the water accumulator? Wouldn't the other also have
the same properties? That the water would accumulate at the bottom? In
any case, should the empty, if that's what I do, be before or after the
filter in the train? FWIW, both of these have valves at the bottom;
I'd thought I might put a nipple in one of them to use to refill the
Racor space when I changed a filter, but I'd pretty much decided to put
my priming pump, left next to the engine where I found it, in front of
the Racors, to make that easier. Though, I don't know about the
pressure vs suction, any more, nor, as this one has been for the
presumed 15 years before we bought it, in line all the time, rather
than on a separate circuit, which reality was disparaged by a diesel
guy in the yard yesterday (he said it absolutely could not be an inline
pump, despite any prior history)...


The better you filter the tank contents removes the submicronic
particles that are the nucleation sites upon which larger and large
particles 'grow'/aggloerate. Stands to reason if you continually
remove these very small particles ... then you will have infinitely
less particles growing. The caveat here is that you still have to get
inside the tank every few years and clean out all the crap thats stuck
to the walls .... but not as often as if didnt have a recirculation
filtration system.

In our particular installation, that's a bit challenging, as the only
access is in the top (bow) deep corner, 1.5", other than some major
disassembly. It's my presumption that it's never been done in this
boat...


The best reason for having a high turnover recirculations system is
when due to degrading oil (cracked oil, or oil thats becoming fouled
with microorganism growth) and the crap has formed on the walls .....
even if the crap does break loose from the walls during a heavy sea
state the reciruclation will QUICKLY restore the tank back to low
particle levels. STill need to clean the tank occasionally.

The BEST way to operate the fuel system is to continuously MONITOR the
main fuel system filters with a vacuum or pressure gauge (measured as
pressure drop across the filter versus maximum engine rpm) ... so you

My Racor setup has the same (make, model, not literally the same)
vacuum gauge as the polishing system. I expected to use that as my
guide - but it's vacuum...

know WHEN to change the filters. Ditto on the recirculation system.
ALL filters should have an operational 'recommendation' of liters per
minute versus 'differential pressure' .... when the operating flow to
the engine is getting close (flow through the filter vs. what the gagte
is telling you - then its time to change the filter ---- READ the
technical specification that come with the filter or go to the filter
manufacturers website for the 'tech' / flow data. Be aware that the

Interesting - neither the Racors nor the other have any such data with
the documentation. IN the case of Racor, I have not had any luck
trying to get information about them, at all. However, the others are
rather more mainstream, so I might be able to discover something about
them...

tech data for flow vs. 'delta P' should be for *fuel oil* and NOT for
water --- big difference in flow/pressure requirements. If the tech
info is in 'water flow' contact the filter manufacturer and get the
'fuel oil' flow rating. Change the filters when the pressure/vac.
gage shows (versus the performance curve of the filter) that the flow
rate 'could be' 200-150% of flow of the engine demand at full throttle
.... look at the engine fuel consumption vs. horsepower curve and then
compare to the fuel filter(s) performance (flow vs. differential
pressure) curve. Size the filters based on the 'performance flow rate
vs. operational differential pressure curve .... NOT the maximum flow
rate on the 'box' .... when filters get dirty their flow begins to shut
down .... plan on it and know the gage pressure when you should change
the filter.

Phew! I only *thought* I thought like an engineer. I'm in way over my
head, here. I'm not sure there's much info on our 30 year old engine
WRT consumption/HP/pressure/vac. I'm pretty sure I'll have to go by
the seat of my pants for the first several changes, after which I can
have the baseline to use...

Not all the particles that a filter 'captures' are 'hard' particles;
many of the particles retained will be 'soft' particles and will begine
to 'extrude' through a filter if the differential pressure across the
filter becomes 'high'. Best is to maintain your own 'history' of
operation (make notes, etc.) and then stick to the maintenance & filter
changeout depending on YOUR operational history, etc..
No sense having ANY filter installed and not knowing WHEN to change it
..... other than having a stalled engine !!!!!!!!! Otherwise, you're
just throwing away good filters or risk stalling the engine (usually at
the worst possible time).

Heh. No kidding. However, I'm wondering if what I'll have to do isn't
a bit like Edison's running a machine until it broke, to see what it
would do, then running the rest of them at 90%...


Before you add a recirculations system .... better to get inside the
tank and scrub out and mechanically remove all the crap .... then you
wont NEED all those expensive 'filters'. Filters only remove
'symptoms', the cause is usually a dirty tank or taking onboard
extremely dirty fuel.

Heh. Fortunately, the polishing system filters aren't all that
expensive, and are huge by the Racor 500 standards of what will follow
all that polishing. And, of course, it was the symptoms, of which I've
had none, yet, that I was looking to address.


When to NOT buy fuel: before pumping into the tank, take a clear
glass, pour some fuel into to it and hold the full glass between you
and a strong light. If there is any 'haze' to the fuel .... get your
fuel somewhere else. When to clean out the tank .... ditto with the
glass in front of strong light.

Gotcha. With any luck what I pull out of the bottom of the polishing
units won't even look like that...

Hope this make 'sense'.
;-)

:{)) More, or less, as per the above. Elucidation/expansion, please?

Thanks

L8R

Skip, up again way too late

On Thu, 23 Nov 2006 19:47:23 GMT, Rich Hampel
wrote:

Recirculation filters should be set up as PRESSURE FEED not vacuum feed
where the pump is at the END of the circuit ..... the filters will be
vastly more efficient versus on-stream service life due to the better
deposition of particles ON the filter surface than IN the filter when
in vacuum feed mode. The Walbro has an integral screen of about

When the filter media sees a pressure differential, how does it know
whether it's caused by sucking on one side or pushing on the other?
Does the filter media actually get compressed by the slightly (tiny)
higher pressure inside the filter housing when it's in pressure feed
vs. vacuum feed? Since the fibers are surrounded by the fluid, the
pressure on each fiber is pretty much equal all around. The only
difference being the difference between the front of the fiber and the
back, which only depends on the differential not the absolute
pressure. So the only way I can see pressure vs. vacuum makin a
difference is if the actual fibers get compressed and get smaller in
diameter by the higher pressure in the canister. But now I have to
understand how only a few PSI difference can cause any significant
deformation/compression of the media fibers.

The only other thing I can think of is maybe the fluid flow rate is
faster for pressure fed vs. vacuum because the pump may be operating
more efficiently that way. But then, assuming the flow rate is
different, the opposite situation would occur. I.e., particles would
be deposited IN the filter for the faster flow rate (pressure) vs. ON
the surface for the slower flow rate (vacuum)

Anyway, enough of my rambling. I'd just like to understand why
particles get deposited ON the filter surface for pressure fed and IN
the filter for vacuum fed.

Steve