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Go Back   SailNet Community > On Board > Gear & Maintenance > Engines > Diesel
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Diesel This is a new forum dedicated to diesel engines and their applicable accessories.


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  #11  
Old 01-08-2011
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I would strongly agree with the usage of a biocide (or rather an enzyme that targets the 'dissolving' of the fungal cell and metabolic byproducts debris). The 'biocide' (enzyme) prevents/retards the formation of the nucleation sites upon which such particle 'grow'. These agglomerated bio-particles are usually soft or 'deformable' particles and can easily blind a filter or be easily extruded through a filter. A small volume/flow polishing system is usually inadequate (because to total amount of fluid filtered vs. TIME) to remove them and when such a filter becomes 'loaded' can quickly release/extrude these particles under increasing differential pressure across the filter.

I restate, in case you are missing the point of a well designed high flow, high turnover recirculation polishing system ......
• less total TIME to remove particles;
• the ability of the (coarse ÁM) filter to ultimately yield a resident particle level that is essentially 'sub-micronic' ... solely due to the % of 'small capture sites' in the filter medium and the VAST amount of fluid that passes through such a filter (a statistical reduction). With enough 'turnovers' a 10 or 15ÁM filter can easily result in less than .5ÁM particles in a tank - visually 'crystal clear' fluid. A small flow system will take 'thousands of hours' to do the SAME job and the 'smaller' the retention rating the vastly LONGER it will take (in the previously posted example case - about 200 times LONGER.

In-line filtration typically in most diesels is 'below' 20ÁM; 20ÁM almost universally acknowledged as the 'most destructive' particle (hard particle) for such service. Fungal debris is typically soft/deformable but readily 'packs' or 'slimes' the upstream of most filters.

Still the fact remains that recirculation polishing will not / ever 'clean' a tank. Only mechanical scrubbing of the internals or chemical cleaning (such as Starbrite "Tank Cleaner", etc.) will 'clean' a tank.
An efficient high turnover recirculation polishing system will greatly extend the time interval between cleanings, retard the 'contamination' by constant removal of the 'nucleation' sites & fungal spores, yield a consistent almost 'sub-micronic' particle level, reduce the challenge of particles to the "racors" to essentially NIL .... and most importantly, will allow the system to quickly 'recover' if indeed a large 'slug' of particles breaks loose from the tank walls. A small flow, low turnover system cannot do this ..... and the component cost is about the same for both!

:-)

Last edited by RichH; 01-08-2011 at 02:54 PM.
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Old 01-08-2011
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The higher the turnover the shorter the time to filter the fuel, but most yachts have not got an unlimited electrical budget to devote to fuel polishing. Large fuel pumps consume lots of energy they also noisy and pluming them is not compatible with most tank fittings.

To clarify your point Ritch how much fuel on average should be filtered each day to make a practical difference to fuel quality ?
My system does 20% a day normally , but when the tank is agitated as in offshore conditions about 400% (4x the typical tank volume is filtered, because I leave the polishing sytem on). I get the impression you feel much more should be filtered to make any difference. If this is correct how much more?

Last edited by noelex77; 01-08-2011 at 03:58 PM.
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Old 01-08-2011
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No no no...... a high turnover pump delivering to a LOW differential pressure filter will require LESS amperage at HIGH FLOW .... than a small pump that is 'straining' (almost 'dead-heading') against a high differential pressure filter. Simple 'work' relationship as seen by 'amperage (times volts) draw'.

***"To clarify your point Ritch how much fuel on average should be filtered each day to make a practical difference to fuel quality ?"***
All depends on the nature of the particles, the degree of fungal, etc. contaminiation, etc.
.....On a strictly practical basis, here's a simple eyeball test determined by the 'current health/hygiene' of your actual system:
• WHEN you have hazy fuel (denotes typically contaminated to a significant amount of 5-10ÁM and above particles), & whatever your total tankage volume, etc., turn on your recirc. system and record the total time it takes to arrive from a 'hazy' fuel to a 'crystal clear' (≤.5ÁM) resident level.
The 'eyeball test' is done with the fuel in a CLEAR clean glass container and held between your eyeball and STRONG white light. 'Any' haze you can 'visualize' means particle contaminated fuel (above ~5ÁM) .... simply run the system and estimate/record the time it takes to become 'crystal clear' / no haze. (This haze/no haze will be very consistent with 'nephalometry evaluations', etc. that can be correlated with 'particle amounts' - eyeball is just as sensitive.) With a 1-2 gpH pump it will take sometimes many hundreds of hours until clear (per 100 gals). In contrast, about 2-3+ hours at ~3 gals per MIN. per 100 gal. tankage.
Recirculation polishing filtration is all about dilution (exponential decay) of the number of particles STILL IN the tank.
If you had 2 tanks, one empty and one full you could easily filter/pump between them in a 'single pass' high efficiency filtration; but, since the return of a recirc. system only SLOWLY (volume per time) *dilutes* the amount of tank particles .... youll typically spend many hundreds+++ of hours waiting for such a 'dilution' with a small pump.

- Whats the ~volume of your tank?
- Whats the retention ÁM (and brand) of your recirc. filters?, and
- Whats the pump? (I need to look at its output performance curve vs. backpressure, etc.) Vacuum or pressure feed to filters?
- Whats the (clean) system gage pressure on your recirc. filter?
Then I can make some generalized assumptioins/guesses and then give you a close estimate of how long a 'moderately' contaminated system will take to 'clean-up' ... based on your approximate parameters.
Total Volume gallons, ÁM and 'brand', ID of pump.

Here's a 60 gph / 1 gpm Walbro that 'deadheads' at 2.3 AMPS. Walbro FRB-13 Industrial & Marine Fuel Pump from Fuel-Pumps.net

;-)

Last edited by RichH; 01-08-2011 at 05:22 PM.
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Old 01-08-2011
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Thanks RichH, I will get the Walbro pump then. I guess since you recommend putting the pump before the racors, a vacuum gauge to monitor the filter will be ineffective on the polishing circuit. I would think you would want the pump after the filter to keep it from sucking debris into it? What is the advantage to having the pressure on the dirty side of the filter?
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  #15  
Old 01-08-2011
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I have had good experience with Walbro
the pumps are made to go before the filter, and the filters are designed to have fuel pushed through and not pulled through. .
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Old 01-09-2011
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Ritch I think we are talking about the same thing at slightly cross purposes.
The fuel pump I use is rated at 60l an hour, about ╝ of the pump you recommend, but still in the same ball park.. Certainly much more than the 1-2 gph (are there pumps this small?) you mention.

With the pump you recommend at 60gph this is still very much what I would call low volume fuel polishing. I believe this is effective and I assume you feel the same.

The alternative method of fuel polishing involves much higher volume pumps. The advantage of this type of polishing is that the high volume will stir up the tank contents. (even better if it can be aimed and directed), but because of the power draw, large hoses, pumps, filtration equipment and the need to open up the tank, it is only suitable to be used occasionally (maybe once a year or less) usually by commercial operators.

Both these systems, occasional use with high volume equipment and frequent use with a low volume pump are called fuel polishing which confuses things.


Anyway to answer you questions.
Whats the ~volume of your tank?
1000L usually with only about 300l in it.
Whats the retention ÁM (and brand) of your recirc. filters?,
10 Micron Raycor 900-
Whats the pump? (I need to look at its output performance curve vs. backpressure, etc.)
Pump is unknown. (it came with the boat) similar to pumps rated at about 60l an hour. When in operation with fuel pumped through the filter about 50l an hour is returned to the tank.
Vacuum or pressure feed to filters?
Vacuum
- Whats the (clean) system gage pressure on your recirc. filter?
The gauge reads almost 0


Then I can make some generalized assumptioins/guesses and then give you a close estimate of how long a ‘moderately’ contaminated system will take to ‘clean-up’ ... based on your approximate parameters.
That would be appreciated.
The fuel is clean it looks crystal clear in the jar. (before the fuel polishing system was installed it was very slightly hazy
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Old 01-09-2011
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Quote:
Originally Posted by Capnblu View Post
Thanks RichH, I will get the Walbro pump then. I guess since you recommend putting the pump before the racors, a vacuum gauge to monitor the filter will be ineffective on the polishing circuit. I would think you would want the pump after the filter to keep it from sucking debris into it? What is the advantage to having the pressure on the dirty side of the filter?
For pressure feed use a pressure gage; For vac. service use a vac. gage or a press./vac. 'combo' gage.

A pressure feed is more effective because of the motive force it can develop .... typically most fuel diaphragm pumps can easily generate up to 20-30 psi pressure before 'stalling' but can only develop about 6" Hg Vacuum or about a negative 3 psi @ 'stall' - simple pump 'dynamics'. A pressure system can produce ~10X the force of a vac. system.
Most aux. fuel pumps (not 'lift' pumps) will have an inlet screen at about 70ÁM which is selected by the mfg. to adequately protect the pump 'internals' (dont forget to clean the screen on a periodic basis). If your system is extremely cruddy, you might need an additional larger surface area inlet 'strainer' ~70ÁM ... but thats for a REAL crapped up system.

Why pressure feed is better than vac. feed (but there are 'risks')
A pressure system will have MORE 'total throughput', will last longer in service.
Filters operate on a relationship of flow vs. differential pressure (∆P) 'across' them; the higher the pressure the higher the flow rate. It takes 'work' to operate a filter and the higher pressure available, the MORE total volume you can flow and the (relative) pressure at which the filter 'clogs' will be much much higher - total 'throughput'. More importantly a vacuum fed filter when 'clogged' will 'stall' or shut down flow at ~ 6" hg. Vac. (~-3psi) while the pressure fed will still deliver fuel (depending on the amount of 'dirt loading') to upwards of 20-30 psid ... that translates to about a possible 10 times the amount of fuel filtered before total plugging in 'pressure' mode versus being in vacuum mode.
Also there is a noted difference in the way that most ('hard') debris is captured between pressure feed and in vac. mode feed. In pressure feed (with low 'velocity' and low ∆P) the debris seems to form more ON the surface of the filter media; but in vacuum feed the debris tends to deposit IN the filter media ... and can cause very short 'service life' - pump is stalling AND the filter is prematurely 'plugged'.

(Note - boat builders prefer to use vac. systems for vastly lessened legal risk as its ultimately better -for them, but not you- to have a stalled engine than have fuel oil spilling into a waterway. They dont get fines if your engine stalls and you go onto the rocks; but, if their design causes 'a sheen on the water' ..... BIG $$$$ ouch.)

Rx/Recommendation - if you are using a fuel recirc., etc. filtration system in 'pressure mode' use only metal tube with double flared connections ... or better!. Compression fittings, etc. are notorious 'leakers' and usually can only be routinely 'tightened' - a single time. All these fittings should be assembled 'dry' and with NO 'dope' nor 'tape'.
Pressure feed fuel systems on rec. boats need to be constantly monitored for leaks, including occasionally 'dead heading' the system, by closing the outlet valve to develop max. pressure to validate/test the mechanical integrity, etc. - due diligence.


For vac. feed, just use the 'positive' ∆P values.

hope this helps.

Last edited by RichH; 01-09-2011 at 01:41 PM.
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  #18  
Old 01-09-2011
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Is A1 hose "better" than metal pipe? Now that I already have 80 feet of it...
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Old 01-09-2011
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I'm surprised no one mentioned Facet Fuel pumps
here's one link to a marine supply. Moyers has em.. Most if not all NAPA stores have em too. I have one on my boat and carry a spare. "solid state" is actually a solenoid pump, makes a tick. unless it's pumping free flow or with air in the lines. Then it sounds like a hammer. Just under 40 bucks for the "posiflow" The cylinder type 4000 series pumps seem to be real popular also.


Facet POSI-FLO Pumps, Facet Fuel Pump Kits, Facet Gasket, Facet Marine Products - Discount Yacht Supplies, Vetus Nautical Accessories, Scandvik Parts, Garmin Marine Electronics
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Old 01-09-2011
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I use a Carter rotary vane pump for my dedicated fuel polishing system. It is a 72 GPH pump through a Racor 900. Works tremendously well thus far.

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