Fuel Polishing - Page 2 - SailNet Community
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post #11 of 15 Old 09-11-2006
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Copper, brass, bronze are REACTIVE with diesel fuel. Such materials will lessen the 'shelf life' of diesel ... normally 6 months in warm weather without coming in contact to 'copper'. Stainless steel tubing with carefully made/assembled double flared fittings is best. Use the MINIMUM of copper containing parts in your system.

For any recirculation system you want lots of 'volume flow' with little pressure drop across fittings, valves, etc. so the pump doesnt have to 'work so hard' and most of the 'pressure' is used to drive the filter .... use a tubing bender and make long radiused elbows, etc. Keep the amount of connections, valves, etc. to a MINUMUM to keep the pressure losses to a minimum.
For a recirculation system consider: the pump 'pressure feeding' the recirculation filters (pressure feed) as the filters will have better on-stream service life (Its the way that debris deposits on/in filter media; although you must make precise connection so that it doesnt leak. The reason for vacuum feed in fuel systems is: use of cheap compression fittings (always eventually leak) and such a leak will suck air and stop the engine .... instead of filling the bilge with oil. Pressure feed is best but the connections, etc. must be 'perfect' ... steep fines are involved if you inadvertantly pump fuel overboard.
Ultimately you want the polishing system to 'turn-over' and re-filter ALL the fuel many many times in as little time as possible. 10-20 uM 10" long 2.5" dia. depth type 'industrial' filter cartridges are probably the best choice: are economical; and, with many many tank turn-overs will result in the tank will 'equilibrate' down to essentially 'submicronic' particles in very short time. Consider an industrial filter housing made from carbon steel with a cast steel/cast iron 'head' but with a drain valve ... to which you attach clear plastic (tygon, etc.) tubing so that when the filter housing traps free water you can SEE the water in the bottom tube and can easily drain it. Use EPDM gaskets or 0-rings whenever possible as it 'swells less' than the common (and qucikly becoming obsolete - Buna, Neoprene, etc. gaskets, etc.)

Stay away from 'self contained' spin-on filters .... very expensive and sometimes hard to get in 'far away' places. Usage of such 'spin-on' filter 'lock' you into using a single manufacturer. There are literally 'hundreds' of industrial filter manufacturers ... so the availability is much much greater.

Totally scrub-out and clean the fuel tank internals BEFORE you apply a polishing system ... no sense in wasting a lot of filter cartridges for 'naught'. Clean out the tank every few years.

Hope this helps. :-)

Sorry but Im a very infrequent visitor here as the Sailnet site only allows usage of Internet Explorer as a browser. As a 'mac' user, I dont want to buy IE 'just' to visit this site. If you have any questions, comments, etc. email me direct @ RhmpL33@att.net

hope this helps.
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post #12 of 15 Old 09-11-2006
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I'm on a Mac, and using Camino, and it works just fine. You might want to try it sometime. Safari works as well. Unless you're running pre-OS X, you should have both as options.


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post #13 of 15 Old 09-11-2006
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Im running the Safari browser on OS10.4.7 and this is the only website that I HAVE to use MSIE on .... same thing with all the OS10.3 too. Dunno and quit trying.
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post #14 of 15 Old 09-11-2006
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Sailamel -
You're absolutely right ... a recirculation system should have its own separate dip tube and that tube should go 'all the way to the bottom' of the tank for water removal AND to pick up the heavy fractions of alkenes, waxes, etc. (decomposition products of old fuel) that are/become the 'nucleation' particles for subsequent 'sludge' to grow on, etc., etc. Whats nice about a recirculation system, if designed right, it can also remove free water from the bottom of the tank; but, its own diptube has to be in the very bottom of the tank to do this. You can also apply filter cartridges/elements in the recirc. loop that are 'filled' with a starch (hydroxymethylcellulose) that will absorb free and emulsified water .... the same stuff thats in baby diapers to absorb 'moisture'.

Water uptake from 'condensation' is really a phenomenon of physical chemisty 'equilibrium' and although changing ambient temps. has minor influence, the moisture will keep entering through the vent until the 'load' is totally saturated. The issue of keeping a full tank goes into two directions; the chief argument against is that unless on a passage the oil quickly degrades as it has a relatively short shelf life, so unless travelling, why load up with oil that eventually goes bad and then fouls the filters and forms 'coke' deposits in the exhaust header and water injection to the wet muffler/silencer? All those folks who have blocked exhaust systems with 'carbon' / coke .... yup, mostly due to keeping old degraded fuel in the tank!!!!! For me, I keep ONLY enough fuel on board to do the job plus a little in reserve .... and I use a desiccant chamber on the tank vent line to 'strip' out water vapor. Silica gel or activated alumina desiccant is easily 'regenerated' in a kitchen oven. I use dyed Silica Gel that turns from blue to pink when needing regeneration. ... No problems even in my black iron tank.

What I recommend on 'serious' fuel systems is an independent 'day tank' of a few gallons of filtered oil located at a height above the engine .... if all hell breaks loose (blocked filters, broken lift pump, etc. etc.) , then you can simply open the bottom **** of the day tank and run for several hours until you 'can sort things out' etc. Since the tank is above the engine, the daytank will still deliver fuel to the injector pump - by gravity.

.... and even with recirc filters, day tanks, multi-pass filters, if you dont get into the tanks once every few years and physically scrub/clean the tank internals ... you ARE ultimately going to have fuel problems.

Hope this helps.
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post #15 of 15 Old 09-11-2006
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I like Rich's suggestion of a gravity-fed day tank, it can solve MANY problems. I've also been told that copper fuel lines should neve be used with diesel, apparently because the sulfur content (which is supposed to be reduced these days) reacts badly with the copper. But, people often use it.

Marine suppliers of "bronze" components usually won't talk about the alloy they are using and many of them actually use an alloy with copper in it, or both tin and copper, so "bronze" kind of transitions into brass for fittings, unless you are doing assays you can't really tell what you are buying. I wouldn't expect galvanic problems from mixing them--but I would assemble all the fittings using anti-seize or a protective film like TefGel. Never teflon tape--as tape strands can get downstream in the system and if they aren't caught in the filters, jam the injectors or pressure pump.
I'm a firm believer in applying "coatings" to anything that has to be threaded together. To make sure that it won't come apart, or that it will come apart, either way.
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