Advice on cleaning fuel tank

[Nyaminyami]

I cleaned a 1300 litre stainless steel diesel fuel tank in situ that had 300 litres of diesel that had sat for the 5 years before I bought the boat, in a marina in Mallorca, Spain.
On inspection with a torch through the 200mm hatch the fuel was clear but on the bottom of the tank and in the corners and under the baffle plates was a thick, tarry deposit that had accumulated under the return pipe into the shape of a 250mm diameter amoeba. A wooden broomstick would not move this except it would bring up sticky globs stuck to the broomstick.
I wanted not to waste the fuel so drained it with a 12v submersible pump and scrubbed the diesel by multiple passes over 24 hours though a series of filters which I had to keep changing. I accumulated a 2kg pile of what I can only describe as that pasty, smelly substance I found in my child's nappy at 02.00hrs on my watch, some years ago. Nasty!
Once drained, I put about 50 litres of water into the fuel tank and added about 1kg of caustic soda from the hardware shop, agitated it, closed the hatch and left it for 24 hours.
After that I used the broomstick to mechanically break up the amoeba and by this stage the water was dark and cloudy and quite thick with globules of the 'baby-poo'.
After adding more water and washing-up liquid I pumped this out and then used a pressure washer lance to clean the inside of the tank until all I could see was stainless steel, clean as a pin. After pumping out all the free water I dried the tank with a vacuum cleaner and put it in reverse and left it for a couple of hours blowing for the final drying.
However, a difficulty arose from the dry, tarry deposits that I could not see in the high corners.
I added about 700 litres of fuel for crossing the Balearic Sea to Mainland Spain and engines alternately sputtered to a halt seven times en route.
The sloshing of the fuel had loosened the unseen hardened gloop which had then congested the filters which had to be changed on each occasion.
A longer journey than anticipated but memorable for many reasons not least being shadowed for an hour by a large pod of dolphins that came right up to the boat, gave a magnificent display of aerial gymnastics and fin-waving , rode the bow pressure wave and I swear were trying to congratulate me on having a good stock of filters aboard.

[Grattaway]

Well I have seen plenty of tanks that look like this in old caterpillar bulldozers and other farm vehicles. The usual solution is to full the tank up with diesel and carry on. The tar like substance has been there for a number of years and generally isn't going anywhere. If it is you have fuel filters to deal with it

[jmschmidt]

If it can be removed without much difficulty take it to a radiator shop have them flush and clean it. I've done this with both fiberglass and metal fuel tanks for about a $100.

[dennismenace111]

Originally Posted by Grattaway

Well I have seen plenty of tanks that look like this in old caterpillar bulldozers and other farm vehicles. The usual solution is to full the tank up with diesel and carry on. The tar like substance has been there for a number of years and generally isn't going anywhere. If it is you have fuel filters to deal with it

My thoughts exactly...if it aint broke, dont fix it. This stuff has probably been there for years.. if the diesel fuel wont melt it, and cause filters to clog up or the engine to run improperly, then take the Alfred E. Newman approach....Why Worry...

[sailingchiro]

I have dealt with a dirty tank clogging filters in the most worst time (heavy weather or during docking) and found removing it was the best way to clean it. My mechanic at the time poured a bunch of nuts, bolts, and washers in the tank. Put in the back of a pick up with some gasoline in it and drove on a gravel road for an hour. Came back and the tank had been vibrated clean. Magnet pulled all the hardware out, The gasoline was used for another solvent. I think he used the gas for a bon fire.

[Shenandoah52]

Originally Posted by sailingchiro

My mechanic at the time poured a bunch of nuts, bolts, and washers in the tank. Put in the back of a pick up with some gasoline in it and drove on a gravel road for an hour. Came back and the tank had been vibrated clean. Magnet pulled all the hardware out, The gasoline was used for another solvent. I think he used the gas for a bon fire.

Lol, that is exactly how I cleaned my tank mentioned in my post above. Except I built a simple gimbal fixture (a little rope and a 2x4) for my tank and hung it from a gantry crane at my shop, poured in a half gallon of 3/4" gravel and a gallon of diluted Purple Power.

The gimbal allowed me to shake it and roll it through all axis, the diluted Purple Power (1 part water, 3 parts Purple Power) got between the steel of the tank and the hard goop through every crack the slamming of the gravel created and it floated that stuff right off. Flushed and vacuumed out the tank, and after about ten minutes the inside of the tank looked brand new.

It's an old mechanics' trick I've used for a long time. You just don't want to be the first one to post that kind of stuff on forums...

[sailingchiro]

It's an old mechanics' trick I've used for a long time. You just don't want to be the first one to post that kind of stuff on forums... [/QUOTE]

I have no shame.

[Shenandoah52]

Originally Posted by sailingchiro

I have no shame.

No, you have bigger balls than I do.

If I had posted that earlier I would have been razzed out of here so fast...

[gamayun]

Originally Posted by dennismenace111

I literally had to break every 10 minutes to clear the fog out of our brains.

You guys are killing me. Before pouring some solvent in there and creating a chemical reaction you might regret (if'n you live through it), you might call up a marine chemist and ask what they recommend to dissolve asphaltene. I don't think it's going to be that easy. That is some serious sludge build up!

[dennismenace111]

Originally Posted by gamayun

You guys are killing me. Before pouring some solvent in there and creating a chemical reaction you might regret (if'n you live through it), you might call up a marine chemist and ask what they recommend to dissolve asphaltene. I don't think it's going to be that easy. That is some serious sludge build up!

Actually we were talking about something totally different... but thats ok... Actually Acetone would do the trick rather well and is not dangerous to use as everyone here states.. Ive used it since I was in college repairing and painting airplanes, cleaning parts and doing alot of other cleaning jobs with it. Yes its volatile but so is gasoline. Your wife probably uses it to remove her nail polish. If not now, then certainly in years gone by.

Acetone would be my first choice to clean the tank...but it shouldnt be used in an enclosed area...it would be best to remove the tank, and do the work outdoors in open air. That would be safe.

The crap on the bottom of the tank is petroleum based. Acetone will soften it enough to remove it. In any case, it wont be a fun job.

My suggestion is that if its not loose and crumbling and finding its way to your filters, dont touch it at all. Its been there for years and no harms been done. If it aint broke, dont fix it

[gamayun]

That's fine, Dennis, as long as you realize that my point was that it might be good for the OP to know what happens when chemicals are mixed. Acetone is flammable and then mixed up with that much hydrocarbon gunk is bound to create a waste disposal problem.

Maybe this paper has some info that could be useful to the OP: jeas_1215_3099.pdf

That link looks funny so if it doesn't work, Google "An Environmentally Friendly Solvent Mix For Asphaltene Deposit Removal" in the ARPN Journal of Engineering and Applied Sciences, Dec 2015.

Basically it says to use methyl oleate, which has low toxicity and high solubility, along with ethanol. Methyl oleate is used to dissolve tar. Cutting to the chase, the paper says that....

"Methyl ester oleate has good solvency for asphaltene. It effectively dissolves asphaltene at 80oC in three hours contact time. For improved effectiveness, ethanol was blended with the methyl ester oleate. Ethanol is a polar solvent with hydroxyl bearing functional group which functions by boosting asphaltene dispersion. Further investigation of the dissolved asphaltene in the blend shows that asphaltene dissolves better in the blend when compared to methyl ester oleate and aromatic xylene respectively. "

The OP will just need to figure out what the commercial name of the product is that contains methyl oleate.

[Checkswrecks]

Had to replace the 35 year old fuel hoses, which meant pulling the 32 gallon tank. Here's the low corner with the sending unit and before de-fueling the fuel level was at about the bottom of the sending unit housing. The floor of the tank was about like soft asphalt and the walls were fairly hardened with a bit of stickiness.


Baffle toward high end of tank:


Capped all of the outlets, poured in a gallon of acetone, swished it around to wet all the surfaces, and let it sit outside in the yard for about two days. Occasionally I'd swish it again in that period.

Drained the acetone thru the fill port back into the gallon can for haz-mat disposal and most of the gunk came out like gritty brown paint. At this point the inside of the tank still has stuff clinging to the surfaces and touching it is pretty oily. Plus from past experience, the acetone dries fast and leaves a hard residue. This is the point to mix up two buckets of hot water with a half bottle of Pine-Sol in each and pour one in. Cap the fill tube and tank inspection port and swish it again.

Put on a pair of long sleeve gloves: https://www.harborfreight.com/oil-re...ves-99677.html

Open the inspection port and get to everything possible with a kitchen bottle brush and scotch-brite pads.

Dump it back into the bucket.

Rinse.

Put in the second bucket of Pine-Sol, swish it and let it sit for another day.

Dump the Pine-Sol, rinse till the water is clear, and let it dry. Getting in there with my phone camera, you can see that even where I missed isn't too bad and the baffled area which I could not get to should look the same.






btw -

It turned out the tank needed to come out anyway, as there were two pin-hole leaks at chafe points where the tank had been in touch with the fiberglass hull.

[slug]

Originally Posted by dmksails

I thought I might have some algae growth in my tank, so I drained it and opened the inspection ports. Yikes! Bottom of tank is covered with a hard tar-like sludge! Not having much luck with putty knife.

Any advice on how to remove this without using dynamite or a flame thrower?

Scrub brush

After a quick scrub the Pros use a hand pump power spray .. like a garden sprayer ... filled with diesel fuel

Buy a good quality one

In Europe the brand is WURTH..,auto parts supplier

The sludge is then removed with a dc fuel transfer pump of other pump