I realize reading it, that my secondary or guard filter is probably 10uM
since it is a Yamaha
(Yamaha and Yanmar ... and Universal and Volvo, etc. dont make
filters .... they buy filters and have someone pait their name on the
filter .... then sell it at 5 times the market price)
part intended for the filter that came with the engine.
I assumed that these were all 2uM from reading previous semi informed
threads.
In real life and without doing an intensive particle distribution
analysis typically any 'terminal/final' filter should be protected by
a pre-filter that is approx. 5 times the retention size of the filter
doing the most-important-work. For best economy, what you want is
that all the sequential filters ----- FAIL all at the same time; and,
for most normal particle distributions in nature the 5:1 sizing will
usually hit the mark the first time out. The next way in 'real life'
is to simply record the differential pressure (gage) across each
filter VERSUS actual gallons/liters filtered, then you can adjust
filter AREA to balance the flows and service life. A fuel oil system
isnt a 'constant state system' so the best is probably just go with
equal surface areas in each and 5X larger retention in the prefilter.
Usually the way filtration of pleated filters works is that (for
constant conditions) if you double the surface area you get about 3
(2.7) times the service life.

PROBABLY A PUMP PROBLEM
probably the beginnings of a pin hole in the diaphragm or a check
valve isnt closing all the way.
I would appreciate your specific answer to the question I've posed which
will apply to many small sailboats. Since the smallest Racor I can buy is
rated at over 15 times the fuel flow of my 20 hp diesel with return line to
the top of the guard filter instead of the tank, does it not make sense to
run a 2uM element in my primary?
NO, not ever. Use a 10µM in FRONT of the 2µM. If the final is 10µM
then use a 30µM RAcor in front of it (Racor doesnt make 50µM) The
10µM will capture a LOT of 2µM particles - the 10µM Racor is probably
60% efficient in capture at 2µM (guesstimate) ... and this will
prolong the life of the final 2µM.

. I don't think my engine fuel pump is
running very hard. I had a lift pump because the filter and fuel pump were
mounted high above the engine.
PUMP should be as LOW as possible; BUT, once the delivery system is
filled it really doesnt matter as the 'siphon effect' will take over -
vertical measured difference between the **maximum/current** fuel
level in the tank versus the vertical height that the pump is
located. Whats really important with (any) pumps is to have some
(siphon) pressure filling the system AND ****the height of fuel****
versus the height of the pump. In your below mentioned 'problem' I'll
bet the farm that this was during the tank being fairly empty... if
the tank was totally filled it would pump MORE (due to this 'siphon
effect' from the tank - also called 'net positive suction head').

PLUS boat engines fuel systems are hooked up ALL WRONG versus the
'hydraulics'. If that lift pump was located back at the tank (like
modern trucks and automobiles are) the pump could possibly develop
upwards of 15 psi pressure, enough to push oil through a partly
clogged filter (they usually stop flowing at 15-20 psi **pressure**
differential. In vacuum mode the best a single stage pump can attain
is about 6" vacuum (about 1/6th of atmospheric pressure - 14.7 psi or
30 inches of vacuum.), so the max. a pump located DOWNSTREAM of a
filter can do is about 2.5 psid (6"vac) if that diaphragm pump is
'pulling' a vacuum, it may be 'stalling' because of the 'vacuum'.
PLUS a diaphragm pump isnt perfect as it pumps a small amount
backwards each time the diaphragm moves down .... until the poppet
check valve fully closes. That 'jiggles' the crud in the filter and
'compresses' the deposited dirt making it additionally harder to pump
through the filter. A small constant displacement gear or vane pump
(with 'blow off valve' to the return line) would be much better.
Pumps dont like to 'pull' they are better at 'pushing' .... filters
will last longer in a pressure feed system than in a vacuum feed
system (has to do with the way the debris is depositied IN the filter
media). If you need to 'protect' the pump use a fine mesh strainer,
NOT a filter.

When I moved the filter and pump to below
the engine, I got 1000 RPM more WOT with the pump turned off and fuel
flowing by gravity than I used to with the lift pump running all the time.
You're adding 'static head' (weight of the column of fluid) to the
inlet side of the pump .... But probably this means that the pump is
faulty ..... Id remove it, put it on a bench and check it to see if
it HOLDS pressure .. just blind off the pump into a small gage
(either end, sequentially) and see when you give it a few strokes (vac
or pressure) that the gage STAYS at the pressure and NOT leaks back to
zero quickly ..... bad pump valves, pin hole in the diaphragm, hole or
tear developing in the diaphragm etc. If fits a valve its probably
the 'inlet' valve.

I like the idea of the constant fuel polishing but I don't think there is
space or weight capacity for it in my boat. The fuel quality is pretty good
up here and the cool climate of Maine seems to help.
I use a 3 GPM 'turnover' rate for a 100 gallon fuel tank. .... start
with a CLEAN tank, do all the filter work in cheapy filters
***offline*** from the main distribution system. Dont even THINK
about using the engine return line for recirculation-polishing
purposes.

I've currently got a debate on similar issues with differing "informed"
viewpoints being presented in my professional life. If you would like to
get paid for an hour of work to offer another viewpoint, please email me
privately.
If its filtration Im partly 'contracted' to more than a few
manufacturers listed above; but, I can help with the 'proof of
concept' and prelim estimates, etc.; then, I can get you in touch with
the correct application engineers, etc. of the most suitable companies
or their technical distributors. For any filtration application I
will need all the 'technicals' on the 'nature of the fluid', whats the
industry, the purpose of filtration, the approximate % of solids(or
deformables) to be removed, the particle 'distribution' of the fluid,
MOST IMPORTANT the absolute viscosity in centipoise, the absolute or
nominal retention desired (and why), the Temps, Pressures, the
'accuracy' of filtration, specific gravity, explosion hazzard,
materials for the housings, batch or continuous, bio-hazard, haz-mat,
etc., sterilization or Titre reduction if biopharm, .... total
chemicals and physicals plus the flow rates on the fluid, etc.
RhmpL33ATattDOTnet.

Thanks again,

--
Roger Long

Bruce -
YUP, same exact depth-filter media used by the electric power
industry, only nowadays they dont much use the presses for high KV
oils and instead use 'cartridges' 12" or 16" diameter with the same
depth filter material made up in 'cells' (looks like dinner plates
face to face) with upwards of 12 or 20 sq. ft. of surface area per
cartridge. Only problem is such specialized filters are not made in
small nor convenient sizes that could be used on small boats.... a
"cartridge housing" in ss would be in the neighborhood of $8k and a
'press' would be $25-30K (yikes) and thats for a 'small' set. When
such specialized filters are used on transformer, etc. oil, a single
pass through will get the water down to 40 part per million ... in a
single pass. The 'good' electric utilities still use tons of
these. ......... small world. What utility?

For small boats, noone makes better delivery line filters than Racor
Div of Parker-Hannefin - fixed resinated cellulose media; for recirc./
polishing the standard industrial PP 2.5"Ø anisotropic pore depth
filters are probably the best value you can find. As with most
maturing industries, there's a lot of crap and 'snake-oil' starting to
show up on the tech marketplace. :-)

On Dec 9, 9:59 pm, RichH wrote:


Hello Richard:

Here is a thougth I hope you would address...

Ive read about the advantages of an onboard "fuel polishing" system.

Ive also read about the advantages of having a dual (redundant) filter
system with the belief if a filter gets clogged and stalls the engine,
the operator can simply flip a few ball valves and place the spare
filter system in service. I guess that a good thing to have cause, "ya
dont want that crud in the tank breaking loose in rough water and kill
the engine just when you need power most."

Question: If there is periodic fuel polishing is there a need for a
redundent filter system?? My thinking is, hey I got a clean tank and
polish often (please define "often" for me) so why have the extra
plumbing? Am i tempting Fate, over optimistic?

Bob

If the tank is periodically cleaned, and the recirculation polishing
system KEEPS the tankage clean, then NO I dont personally recommend
nor use filters in parallel.

However and to thwart "Mr. Murphy", to be ready to take care of
extreme emergencies (wearing belt, suspenders, AND velcro) I recommend
use of a small 1-3 gallon 'day tank' downstream of the filter set,
mounted physically 'above' the engine. The tank would be so designed
that it always is full and cannot drain all by itself unless you
'throw a valve' at the bottom; plus a vent valve that opens to
atmosphere. Then, when all hell breaks loose, such as broken lift
pump, clogged filters, etc. and since the oil would already be
filtered, all you have to do is open the bottom drain and atmospheric
vent ..... and would have 1 to 4 hours of fuel available.
Alternatively, and again for a 'clean' system, you can simply install
a 3 valve bypass (no filter in the bypass) around all the filters so
that you can momentarily open the bypass and change the filters. But
for all filters you must have a means to quickly purge any air that
enters during changeout, so install a small (fuel oil compatible)
12vdc fuel pump between the tank and the first filter to 'push' the
oil through the filters to aid in 'air-bleeding'. When not needed
that fuel pump will just 'sit there' and not add any restriction to
flow due to the orientation and design of the poppet check valves. On
large diesel (prime movers) fuel systems they dont bother to 'bleed'
as they have 'air trap knockout pots installed - just an empty filter
housing installed upside down with a vent valve on top ... but this
can only be used in a pressurized system.

SUMMARY
If you dont have a clean tank, dont have an onboard polishing system,
dont have a day tank; then yes, consider to install a parallel
arrangement thats easily 'bleed-able'. Such a system should ALWAYS be
monitored with gages to know WHEN to change AND for best effect should
be run with ALL filters 'on-line' and filtering. I dont think this is
necessary as if you are using gages to monitor the status of the
filters, you can usually see a problem developing long before you need
to change-out --- again, thats in a system with a 'clean' tank. How
to use such gages: run the engine at FULL/max. rpm, then read the
gages. On the Parker.com/Racor website there are (somewhere)
published charts indicating ----- 'gage vacuum' versus how much fuel
is flowing through the filters----- (if using sequential filters -
then the results of both filters are additive with respect to flow
rate), you want to change out the filters when they reach 75-80% of
maximum differential pressure (∆P), 100% ∆P would be the value of
output of your lift pump .... when its 'deadheaded' (the valve at the
tank is OFF, etc.) .... again all values taken with the engine at max.
rpm or wide-open-throttle WOT ... while the engine is 'in gear' and
'under load'.

OTHER
Again, the best bet is only to buy your fuel from a 'high turnover'
source such as a depot that caters to 'watermen', or carry it in from
a high volume truckstop, keep only the amount of fuel in the tank you
NEED plus some 'reserve'. If you MUST buy your fuel from a 'marina',
FIRST pour some of the fuel into a clear glass container, hold it up
between your eyeball and the sun .... and if there is any 'cloudiness'
to fuel .... go somewhere else. If you dont put crap into your tank,
keep your tank clean .... you wont be challenging the filters. Filters
only do the job they were designed to do .... take out crap; if you
dont put crap into the tank and dont let the crap 'grow' (agglomerate)
in your tank, you really dont need filters. Just remember - the
smaller the tank the greater the vulnerability to fouling and fuel
degradation. For longterm boat 'lay-up', I remove ALL the fuel in the
tank - why feed all those fungals and bacteria?

hope this helps.

My thinking is, hey I got a clean tank and
polish often (please define "often" for me) so why have the extra
plumbing? Am i tempting Fate, over optimistic?

I recirculate any time the engine is on and I have the excess 12v to
run the recirc. pump. I even sometimes run the recirc pump for
several hours while at the dock and charging my batteries from shore
power.

Anytime the fuel begins to have a 'hint' of cloudiness, I polish it
long and hard until its back to 'crystal clear' .... using that clear
glass and the sun. A fuel 'haze' will be particles down in the range
of 1-5µM, crystal clear will be the fuel is virtually free of
particles above 'submicronic' level.