Fuel polishing - how often?

[DeepFrz]

Posted by Charlie: I don't know that you need to do this every year. It has been five years since I cleaned my tanks and have had no problems but I think it would be prudent of me to do it again -- like last year.

Yep. I don't think that tank cleaning needs to be done every year but my personal thoughts are they should be inspected every year, every two years at the least and cleaned if necessary. The way that Ken's fuel polisher is installed is the way they should be installed. Having seen pictures of a fuel tank with proper fuel polishing system I am convinced. The tank shone and was opened because a tech. dropped an aluminum tab from a bottle of additive. Instead of just closing up the system they opened tank, drained the fuel and dug out the tab. While at it they took pictures of the tank. The difference from what we usually see of the inside of fuel tanks was enlightening. I'm sure you can attest to that Charlie.

[thinwater]

Originally Posted by Toys_with_time

Commercially available or do you have to build your own?

Before I jumped on the UV bandwagon consider several things:

1. It only reaches the bug that are in suspension, and the filter will get most of those. It does not reach the ones living on the tanks walls.
2. Does the UV increase fuel degradation? The answer is yes, we just don't know how much.
3. No commercial systems. There is a reason.

I think you are much better off with Biobor. It will reach every portion of the system.

[s/v Jedi]

Biobor is a biocide, i.e. a poison. It is old tech, the Egyptians used poison. We have something better today and it's enzymes. Use Startron.

[laika]

My understanding is that biobor fills a different niche as a microbiocide, and startron a fuel preservative and lubricator.

I know biobor is still very much a go-to with the general aviation crowd. But then fuel preservation and lubricating low-sulfur diesel is not so much on the list of requirements.

[DeepFrz]

Diesel Additives - Practical Sailor Print Edition Article
The tests found that a combination of the Star Tron and Biobor was the best combination to prevent corrosion and biological growth.

This test also highlighted the need to keep the fuel clean and dry. They are also testing vent filters to see if they can help prevent corrosion. They also highlighted the need for very close examination at least every five years.

[Kiwi.]

Let's go back to the original problem: dodgy fuel in parts of the world we all love. I have always cleaned/polished the fuel from the dodgy dock before it got anywhere near my tanks, let alone my motor. We're not talking power boats here, that need to take on a couple of thousand gallons; my hundred gallons (400 odd litres in my part of the world) might take me a hour to put on board instead of 15 minutes but I know it's clean because it's gone into my 5 gallon plastic tin that is continuously pumped through a couple of filters (50 and 10) before it goes into the tank. A hose from your polishing system up to the cockpit with a hose fitting into the bottom of a plastic 5 gallon tin is all you need.


After that Kenomac has it completely correct: leave the tank absolutely full when you winter over. All of the nasty stuff forms on the surface of your fuel where air meets condensation and fuel. If there is no space for air and condensation then no "bug" forms.(One of the reasons you get bad fuel from poor places, they never fill their supply tanks.) So polishing fuel that you put back into the same tank misses most of the problem which is on the surface (not the bottom) of the tank.


For about 20 years, I only had a few hours a week to go boating so I bought a 50ft stink pot with two 3 hundred gallon tanks. At least twice a year I'd take the stink pot for a hard bouncy ride and then run one tank dry through my polisher into the other tank. The initial stirred up bottom would produce a bit of stuff, but 90% of the crap came from the last gallon on the surface of the tank.



Xlantic has it right as well; a day tank is the best. Every super-yacht in the world has one for just this reason. A day tank has the return to the main tanks at the top, so the surface "bug" problem never forms (it's full every day), and the feed to the motors at the very bottom, so that there is never any crap in the tank; the polisher feeds the day tank until it over flows back to the main tanks. You then just need a basic filter and water separator after the day tank.



DeepFrz and Kenomac both have it completely right regarding leaving your polisher on a timer when you're not there. I'd never get to sleep thinking about fuel moving around my boat when I'm not there. Just fill the tank right up (through your polisher) and it will be fine when you come back.



As an aside, my wife tells me we're moving to the dark side and buying a catamaran so she can cook and talk to me at the same time! When we do (the male on this boat is not necessarily the captain) I will immediately install two small day tanks (say three gallons each) fed from my polisher. I find it almost unbelievable that all production catamarans run one fuel tank. (Please tell me I'm wrong!) The greatest advantage of two motors is if one dies you have the other. But, the most common reason for running diesels to stop, is fuel quality or lack thereof, so one tank supply to two motors is crazy.


Yes, the water-diesel interface is also a good "bug" breeding space. So make sure your diesel outlet is at the very bottom of the tank. Some boats have it a half inch above the bottom, I'm sure that that is to insure that the builder gets a few years and out of warranty before the sludge gets to the input!

[s/v Jedi]

Originally Posted by DeepFrz

Diesel Additives - Practical Sailor Print Edition Article
The tests found that a combination of the Star Tron and Biobor was the best combination to prevent corrosion and biological growth.

This test also highlighted the need to keep the fuel clean and dry. They are also testing vent filters to see if they can help prevent corrosion. They also highlighted the need for very close examination at least every five years.

If you have a severe and acute infestation, then adding poison obviously helps. That said, in order to prevent trouble and maintain the fuel system, Startron by itself is more than capable. Here is the actual text on this:

Star Tron Enzyme
This product was a clear winner. The tank bottom sample showed some darkening but no pitting. All other samples showed only patina. Early observations led us to add an additional test sample containing Biobor JF (for its biocide) and Star Tron (for its corrosion-fighting) to see if the pairing worked well, which it did. Previously (PS, July 2009), Star Tron was tested against registered biocides including Biobor JF and Valvtect Bioguard. Although the manufacturer does not claim Star Tron to be a biocide, it did show an ability to control biological growth, giving us one more reason to recommend this product. While we have not been impressed with the Star Tron line in gasoline applications, in diesel it seems to be a winner. Bottom line: This is our Best Choice.

[Glenn.Brooks]

So after years and years of using Raycor filters (40 years actually ) last fall I finally got a load of black gelatin like substance clogging the sediment bowl. Had to take the Raycor out of the boat and disassemble to clean, as the jelly like substance clogged the bowl and wouldn't drain/flow out.

Is this black crud you all talk about ever the consistency of jelly? I was thinking maybe a fuel line is starting to deteriorate and putting dissolved rubber back into the tank...where it clings to each other like a jelly fish and builds up in the filter.

BTW, I have a fuel guage opening in the tank, which I open routinely to inspect the tank and can see no growth inside the tank- it's 25 years old and made of Aluminium. I think the crud and water got delivered to the tank at the fuel dock - sort of like an unwanted additive...

Thanks


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[DeepFrz]

It may have come from the fuel dock. If you are still in the area it would be good to talk to the fuel dock owner/manager or other boaters that have fueled there. They should be filtering to 30 micron on the output of their tanks. If it is rubber then it should have some tendency to stretch and would likely be a little firmer in composition.

Yes, the stuff is like you describe. A few drops of household bleach on the crap will tell you if it is biological or tar like precipitates. If it turns kind of white it is biological growth.

I have experienced this stuff clogging the fuel line, not making it to the filter. Didn't know about the bleach trick at that time so I'm not sure what it was.

[leftbrainstuff]

Originally Posted by Toys_with_time

After a bad experience with (Greek) diesel fuel last year that cost me $$$$ I have installed a fuel polisher. Intend to run it both summer and when the boat is laid up for winter. System consists of 2 Separ filter / water separators (30 & 10 micron), a small pump and a 12v timer. My fuel tank is 300 litres and the continuously rated pump will move about 90 litres per hour.

The timer can be set for any combination of days and times up to 9 programs. So the question is how often and how long should I run it in summer and ditto for winter?

TwT


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Depends on how much crud and sediment lives in your tank. Also depends on how clean and whatntype of diesel you have.

I polish once a week. This lets me always know what condition my fuel us in. Knowing the condition of your fuel is more important than blindly following anstrict polishing regime.

Racor do a lovely little 2W fuel polisher. Its a tad pricey at $400 bit this would run all the time as it is very low flow.

For your 90 L / hr once a week should be fine.

Remember nobody ever got in trouble for having diesel that was too clean.


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[leftbrainstuff]

Originally Posted by holmek

I'm having trouble understanding this whole paranoia. I live on a farm and have diesel tractors. I fill the farm bulk tank ( 2000lt ) once a year. The tractors have 2 fuel filters in line, no sweat - ever. Most boat motors are marinised versions of regular diesel engines, so what is it with the "polishing"?
So long as you have a water trap filter and a regular diesel filter, what is the worry?! There has been talk of the diesel reverting back to tar/crude/bitumen if it is not used within a short time period, - baloney, mine sits in the bulk tank on the farm for the whole year, and then some. Let's get some expert fuel engineer advice here, tempered with the fact that OLD diesel in my farm tank is just fine.

The issue is primarily related to replenishment from suspect marine fuel tanks which often ingest lots more water than land based tanks.

In the military back in the day when we used drums we would always carefully ensure the drums were tilted so the filler bungs werent ever submerged.

In fact in the Australian Army it was a chargeable offence to not do so.

Many navies have published extensively on this topic. Most ships used to ballast fuel tanks with water anyway.

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[Nicholson58]

I posted #29 a few pages back with links to two excellent articles on polishing for diesel marine engines. I urge anyone serious in clean oil to read these.

On the question of jello sludge - YES. If you have water in the tank, the algae & bacteria will form a jelly like goo at the interface. I cleaned our tanks when we got the boat. There was a layer about 4 inches deep of black jelly that looked like rotting garden slugs.

Hard deposits: YES We had those too. These may look like they would stay put but bits move around always. If you can see it, its way bigger than 10 microns. I built servo-hydraulic equipment for several years. 3 microns was barely acceptable; 1 micron was the target. The stuff in the tank photos above is an injection pump and injector killer.

Condensation is the least concern for water. Most water either comes with bad fuel or enters your leaking O-Ring at the fuel fill. Remove the O-Ring and bend it. Look for cracks.

Users of the filter systems I noted in my previous post find the inside of their tanks become spotless & shiny after a few months & they stay that way.

[DeepFrz]

leftbrainstuff posted: Racor do a lovely little 2W fuel polisher. Its a tad pricey at $400 bit this would run all the time as it is very low flow.

That thing should never be called a fuel polishing system. You really need to move more fuel than that in order to scrub up any loose stuff that has settled in the tank. And the price is outrageous.

p.s.: I said LOOSE stuff.

[onestepcsy37]

I added an electric fuel pump to my perkins 4-108. Not that the mechanical pump wasnt working, but because it made bleeding the system incredibly easy.
A side benefit is that I can run the electric pump while the engine is shut down and it pushes diesel from the tank through both filters and back into the tank, a pretty cheap "fuel polishing" system. From observation I estimate that it cycles the tank completely every 15 minutes. A two hour session would give me eight cycles at a cost of about 10 amps.
Real sludge can only be removed by getting your hands inside the tank and manually cleaning it. Easy if you have a readibly accessible tank with a large cleanout port on top, like on a CSY...

[Kiwi.]

Originally Posted by onestepcsy37

Real sludge can only be removed by getting your hands inside the tank and manually cleaning it. Easy if you have a readibly accessible tank with a large cleanout port on top, like on a CSY...

I wish that was true, and it is 90% of the time. I spent many years hopping onto racing boats that were going off into big seas for the first time in a year. There's nothing like falling off steep, tide driven, 3 meter (10ft) swells (and I do mean falling) to stir up that stuff. On a race boat that uses it's engine for ten minutes to get off the dock, a hidden layer of the black crap is often sitting there ready to move around in a big sea. Very embarrassing having done well in a hundred mile race to drop the sails in front of the club house and have the motor stop one minute later.