Poll: How Often Do You Clean Out Your Diesel Tanks?

[noelex 77]

I had some deris and sludge visable in fuel samples taken from the bottom of the tank. This was about 3 years ago. As my fuel tank was 3/4 full (about 750L) I installed a perminant fuel polishing system and vowed to clean the tank when possible.

The polishing system worked well and the fuel samples became spotless over a period of few months use. I opened up the large access hatches 12 months after the initial problem with a view to manually cleaning it.
However the tank was very clean. So just bolted the hatches back on.

It's difficult to be positive how much the fuel polishing worked as I had not inspected the tanks prior to installing it.

If you could clean the tank easily I think this is the best option, but a high pressure polish with a large pump (DIY or professional) and/or a lower volume pump that uses the agitation while sailing to stir up the tank, like I have used, can be effective. Ideally such systems work better as a preventive measure but my experience suggests polishing can work even if there is an existing (minor) problem.

Finally a plea to all boatbuilders. This is what we want on the top of our fuel tank.

[Strait Shooter]

I just built (4) 10" inspection plates into (2) new 85 gal aluminum tanks. I built in fuel polishing pick ups and returns and hope to have the grand kids clean the tanks for me in ten years.

[Dockhead]

Originally Posted by noelex 77

I had some deris and sludge visable in fuel samples taken from the bottom of the tank. This was about 3 years ago. As my fuel tank was 3/4 full (about 750L) I installed a perminant fuel polishing system and vowed to clean the tank when possible.

The polishing system worked well and the fuel samples became spotless over a period of few months use. I opened up the large access hatches 12 months after the initial problem with a view to manually cleaning it.
However the tank was very clean. So just bolted the hatches back on.

It's difficult to be positive how much the fuel polishing worked as I had not inspected the tanks prior to installing it.

If you could clean the tank easily I think this is the best option, but a high pressure polish with a large pump (DIY or professional) and/or a lower volume pump that uses the agitation while sailing to stir up the tank, like I have used, can be effective. Ideally such systems work better as a preventive measure but my experience suggests polishing can work even if there is an existing (minor) problem.

Finally a plea to all boatbuilders. This is what we want on the top of our fuel tank.

You guys are lucky. That really is the way fuel tanks should be built.

You can't even see my fuel tank; it's entirely built into a walled-off part of the engine room with no access at all. You have to remove the built-in microwave in the galley to even see an inspection hatch. To see any part of the tank itself, you have to dismantle the companionway stairs and the cabinetry behind it. Ekhhh . . .

I guess the right thing for me to do, long term, would be to put in some kind of low pickup for sampling and polishing. I guess continuous polishing is the way to go to keep the tank from ever getting dirty in the first place.

I also very much like the idea of a gravity fed day tank. Fill it with clean fuel and you don't have any worries at all in rough weather.

[Strait Shooter]

The use of these help also H2Out® AVD2 ~ Product ~ H2Out

[NSboatman]

Hey folks -

this is an area where I have a little experience. Full disclosure up front: I am working with a company that is building next-gen fuel filtration and polishing systems for any size fuel storage sites (1000l to 400,000l and more). We are actively dealing with this in many industries, including marine, on a daily basis.

Most of the comments thus far are mostly correct from a technical standpoint- but there are a few changes that have occurred in the fuel manufacturing and distribution chain around the world that have moved the goal posts and dramatically complicated matters.

In short - Diesel fuel today ain't what it was only a few short years ago.

The (government mandated) move to ULSD (below 15 ppm sulphur) removed much of the lubricity inherent in diesel. Without lubricity, engines don't run for long, so additives are put back into the fuel to bring lubricity back up. these additives are all members of the surfactant family, and change the chemistry of the blend, bringing with them the ability to absorb and attract more water. they also change what's called the interfacial tension in the fuel molecules. This has a significant effect on the ability of water to exist in emulsion in the fuel, and makes it almost impossible to filter out using traditional absorptive (racor and equiv type) filters. Even big-ship centrifugal polishing/purifying systems are not removing this water effectively - they also have this issue.

Add to this the (also govt mandated) addition of a certain percentage of bio-sourced fuels, and there is an enormously variable new source of both water and other contaminants. the Fatty Methyl Esters (FAME) of bio-sourced fuels are highly unstable and also very hygroscopic; increasing both the water content and tendency of the fuels to gel and be less predictable at variable temperatures.

As has been noted, the growth of bacteria in fuel tanks is directly related to water - the bacteria (not algae please...) grows in the water, feeding on the fuel components. biocides do kill the bacteria, but there is still the organic matter that is slushing around in your tank. dead or alive, it still clogs stuff up badly. Another lesser known issue with these bacteria are their byproducts of consumption - which is acetic (and others) acid. many terrestrial tanks are finding severe corrosion of metallic components under the new fuels, and so far all indicators are pointing to a high acid concentration near corroded areas- directly as a result of the bacterial byproducts.

The end result is a fuel that can contain a lot of water in emulsion, which is not being filtered out by almost any of the exiting polishing systems on the market (ask them to show you their SAE J1488 2010 test results... where they measure the ability of a filter to remove emulsified water from ULSD and bioblends... they won't have any). This fuel is radically unstable and can degrade in a matter of months - and folks... this is the fuel we all buy right now, whether we know it or not. it's mandated in most of North America and Europe. Around here, we're getting anywhere from a 2% to a 10% bio-blend depending on the time of year, but you don't really know because the blenders are allowed to average it over a full year. could be 10% in the summer and 2% or less in winter... you'll never really know unless you test on each fuel delivery (which is possible - but a simple biofuel test kit is a couple hundred bucks!).

Combine this with modern common rail diesels with very tight tolerances and high injection pressures and almost zero ability to handle either water or sludge and you've got a perfect storm.

What can you do about it? Well of course I'd like to suggest you buy one of our systems - but they are not ready for the non-commercial/recreational market yet... will come soon. They are the only 3rd party certified SAE J1488 (2010) fuel polishing systems on the market that can remove all the emulsified water from new blends of fuel. if you'd like to learn more go to Puritas Energy - Puritas Energy to read the whole story.

in the meantime (I am dealing with this on my boat too) all you can do is try to burn your fuel reasonably quickly, keep it as dry as possible, use a biocide and have lots of filters handy to change out when the clogs come thru. AND clean your tanks whenever you get the chance.

who knew fuel was so dang complicated? I just wanna burn the stuff!!

best regards-

bg

[Dockhead]

Originally Posted by NSboatman

Hey folks -

this is an area where I have a little experience. Full disclosure up front: I am working with a company that is building next-gen fuel filtration and polishing systems for any size fuel storage sites (1000l to 400,000l and more). We are actively dealing with this in many industries, including marine, on a daily basis.

Most of the comments thus far are mostly correct from a technical standpoint- but there are a few changes that have occurred in the fuel manufacturing and distribution chain around the world that have moved the goal posts and dramatically complicated matters.

In short - Diesel fuel today ain't what it was only a few short years ago.

The (government mandated) move to ULSD (below 15 ppm sulphur) removed much of the lubricity inherent in diesel. Without lubricity, engines don't run for long, so additives are put back into the fuel to bring lubricity back up. these additives are all members of the surfactant family, and change the chemistry of the blend, bringing with them the ability to absorb and attract more water. they also change what's called the interfacial tension in the fuel molecules. This has a significant effect on the ability of water to exist in emulsion in the fuel, and makes it almost impossible to filter out using traditional absorptive (racor and equiv type) filters. Even big-ship centrifugal polishing/purifying systems are not removing this water effectively - they also have this issue.

Add to this the (also govt mandated) addition of a certain percentage of bio-sourced fuels, and there is an enormously variable new source of both water and other contaminants. the Fatty Methyl Esters (FAME) of bio-sourced fuels are highly unstable and also very hygroscopic; increasing both the water content and tendency of the fuels to gel and be less predictable at variable temperatures.

As has been noted, the growth of bacteria in fuel tanks is directly related to water - the bacteria (not algae please...) grows in the water, feeding on the fuel components. biocides do kill the bacteria, but there is still the organic matter that is slushing around in your tank. dead or alive, it still clogs stuff up badly. Another lesser known issue with these bacteria are their byproducts of consumption - which is acetic (and others) acid. many terrestrial tanks are finding severe corrosion of metallic components under the new fuels, and so far all indicators are pointing to a high acid concentration near corroded areas- directly as a result of the bacterial byproducts.

The end result is a fuel that can contain a lot of water in emulsion, which is not being filtered out by almost any of the exiting polishing systems on the market (ask them to show you their SAE J1488 2010 test results... where they measure the ability of a filter to remove emulsified water from ULSD and bioblends... they won't have any). This fuel is radically unstable and can degrade in a matter of months - and folks... this is the fuel we all buy right now, whether we know it or not. it's mandated in most of North America and Europe. Around here, we're getting anywhere from a 2% to a 10% bio-blend depending on the time of year, but you don't really know because the blenders are allowed to average it over a full year. could be 10% in the summer and 2% or less in winter... you'll never really know unless you test on each fuel delivery (which is possible - but a simple biofuel test kit is a couple hundred bucks!).

Combine this with modern common rail diesels with very tight tolerances and high injection pressures and almost zero ability to handle either water or sludge and you've got a perfect storm.

What can you do about it? Well of course I'd like to suggest you buy one of our systems - but they are not ready for the non-commercial/recreational market yet... will come soon. They are the only 3rd party certified SAE J1488 (2010) fuel polishing systems on the market that can remove all the emulsified water from new blends of fuel. if you'd like to learn more go to Puritas Energy - Puritas Energy to read the whole story.

in the meantime (I am dealing with this on my boat too) all you can do is try to burn your fuel reasonably quickly, keep it as dry as possible, use a biocide and have lots of filters handy to change out when the clogs come thru. AND clean your tanks whenever you get the chance.

who knew fuel was so dang complicated? I just wanna burn the stuff!!

best regards-

bg

That's a useful explanation. I'm no expert, but what you say corresponds exactly to what I have read and been told.

One slight correction -- in Europe, biodiesel is not required for seagoing vessels, only vessels primarily operating in inland waterways. In the UK, 100% mineral diesel continues to be widely available. I guess it must be the same in other European countries. In the UK, adding biodiesel to the standard type of diesel fuel for seagoing vessels -- fuel sold under standard BS ISO 8217 -- is prohibited.

Biodiesel -- FAME -- in its present form, in fact, is a menace to seagoing vessels, and could easily kill someone, for all the reasons described in the post above. It should not be used until some form of it is invented which is safe for use in seagoing vessels.

The RYA warn that boaters must not put biodiesel in their boats without extensive preparation and modifications, and without using different operating habits. Among other things, they say that one should install sumps or low point pickups (and use them to remove water frequently), as well as dual filters. See: http://www.rya.org.uk/SiteCollection...0technical.pdf

and

Low-sulphur fuel now being supplied | Cruising | RYA

[belizesailor]

Just had mine polished for the first time in over 10 years. In my case the boat has been in almost continuos service (charters or cruising) since day one...this helps a lot...it was actually not bad. Polished beacause it just sat unused for about 8 months...longest time ever unused.

[NSboatman]

Hey dockhead - thanks for the correction. interesting links too.

I presume all the mineral diesel is still ULSD though, correct? Not many places in the developed world are running LSD or regular high-sulphur diesel anymore.

sometimes too much emphasis is placed on the biodiesel part - the issues are still bad with regular ULSD. I know of recent cases in Florida where contamination and clogging of an otherwise good system occurred in less than 3 months - and they're not running any Bio there.

Hurricane Sandy exposed this issue in a big way in NYC last fall - many of those wonderful standby systems that weren't flooded died after a few hours of picking up the load - due to bad fuel from having it sit around in their tanks forever. I'm sure not much of that was Biodiesel!

bg

[Capt Phil]

Excellent info, NSboatman... I knew that there had been some government mandated formulation changes in diesel fuel as well as gasoline manufacturing but didn't know or wouldn't share what the full ramifications were.
I recall talking at length with a research engineer from a major oil company about 30 years ago when California was mandating getting lead out of gasoline and requiring that refineries replace it MTBE. The research engineer told me that they warned the CA EPA this might help maintain octane levels but was totally soluable in water and should not be used because it was bound to get into groundwater. Of course the government scientists told the researchers they were crazy and embarked on probably the biggest groundwater contamination boondoggle the country has ever seen.
The problem is that government agencies are so politicized and become so vested in their point of view, they are deaf to any other solution than their own.
Thanks for the good post... Phil

[onestepcsy37]

i emptied out my diesel tank today. 25 gallons of diesel to the town collection site. now i'm going to manually clean out the tank through the access hole and put some fresh diesel in. sure hurt to see $100 worth of diesel go into the collection tank.

upon first inspection i see that there are some black spots on the tank bottom. they come off just by wiping them with my finger. wonder what that is...

[s/v Jedi]

Originally Posted by onestepcsy37

i emptied out my diesel tank today. 25 gallons of diesel to the town collection site. now i'm going to manually clean out the tank through the access hole and put some fresh diesel in. sure hurt to see $100 worth of diesel go into the collection tank.

upon first inspection i see that there are some black spots on the tank bottom. they come off just by wiping them with my finger. wonder what that is...

Diesel is not like gas that goes bad; I use diesel that is 6 years old. As long as you polish it and use the enzyme based treatment, you can keep it for a very long time.

[SimonV]

I know we keep talking about fuel polishing. But in theory every time you run the motor you are polishing the fuel. Your diesel motor only uses a fraction of the fuel your pump pulls out of the tank moves through the filters and puts a majority back in the tank. From what I can find the smallest fuel pump moves about 30 us gallons an hour, mine mover 50gph at 7psi. So in just 1.6hrs I have filtered my 80gal tank. Instead of building a stand alone fuel polisher why not put an in line fuel pump beef up your normal filters and save space. Fuel polishing does not remove the crud on the bottom and clinging to the sides of the tank.

[Paul Elliott]

I voted "every two years". That's been how often I do an ocean race/return, so I have a real incentive to make sure my fuel system is clean. I occasionally probe the low point in the tanks using a vacuum pump to make sure there isn't a lot of water down there. I've started using biocide when fueling (starting with a scrubbed tank).

VALIS has 75-gal and a 25-gal aluminum fuel tanks (diesel), and a Racor filter with centrifugal water separator. I have had the filter clog and engine stop after being bounced around in big seas -- this was during an offshore pre-race shakedown, before I had cleaned the tank. It turned out that there was way too much water and bacterial slime. Fortunately, I carry lots of spare filters.

My tanks have access ports on top, but the internal baffles do make it hard to access all areas of the tank. I pump the tanks into multiple jerry cans, and use low-lint paper towels to mop out the residue and scrub out the slime. By taking the fuel from the top of the tank I end up with mostly good diesel in the jerry cans. Once I get down to the nasty stuff, that goes into jerry cans that I mark "contaminated". The good stuff I filter and re-use in the boat, or in my tractor. The bad stuff gets recycled.

I think it's time to inspect my tanks again!

[Dockhead]

Originally Posted by SimonV

I know we keep talking about fuel polishing. But in theory every time you run the motor you are polishing the fuel. Your diesel motor only uses a fraction of the fuel your pump pulls out of the tank moves through the filters and puts a majority back in the tank. From what I can find the smallest fuel pump moves about 30 us gallons an hour, mine mover 50gph at 7psi. So in just 1.6hrs I have filtered my 80gal tank. Instead of building a stand alone fuel polisher why not put an in line fuel pump beef up your normal filters and save space. Fuel polishing does not remove the crud on the bottom and clinging to the sides of the tank.

The problem with letting your engine polish your fuel is, as was mentioned above, the fact that your main engine fuel pickup is located some distance above the bottom of the tank. It is especially designed that way so that it won't touch the water which is building up at the bottom.

Fuel polishing systems are designed to tackle the water at the bottom, taking it out continuously. For that the pickup needs to be right at the bottom, done I guess the way Jedi described above. If you continuously take the water out as it forms, then there is nothing for the bacteria to grow in. That's the idea, anyway, but it sounds right to me.