Solvent for gunk

zoidberg

zoidberg

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The stainless diesel tank in my cockpit locker cannot be removed, for cleaning, without unwanted surgery. There's no top access, save via the stainless 38mm right-angled filler tube and a pair of 10mm stainless stubs for vent and fuel return. In the one side, there's a low level 1/4" BSP outlet tap. That's it. Most of the contaminated contents have been drained.

Removal of the hosetail barb ( 1/4" BSP to 8mm, outlet ) and inspection indicates presence of quite a lot of black gunk. I assume there's lots more inside the tank base. I can get a very narrow 'bottlebrush' in through the open outlet tap, but that cannot reach far inside to clean the flat inner base.

I could possibly introduce a flexible steam pipe via the 90° filler tube, and this could drain via the outlet tap - but I would have difficulty directing it and inspecting results or lack of them.

What solvent might be effective in dissolving this gunk - presumably the debris from many generations of 'diesel bug'?
 
I cleaned out a s/s tank with steam from a hired wallpaper stripper. I steamed it for two days and a lot of muck came out so it's an effective way of loosening the sludge. The difference was that I was able remove the tank from the boat and move it into different positions as I steamed it.

You can't do this but steaming might help by loosening the muck, and you can perhaps flush it out with hot water using a hose through the filler tube.

If it was up to me, and it wasn't practicable to remove the tank, I'd consider cutting a hole and fitting an access hatch.
 
Would it be possible to cut an inspection hatch, for this and future cleans ?

I once was on a big twin engine motor sailer ( expected to take it to Spain from N France ) - the owner seemed suspect as did the filters, on removing the inspection panels in the two big tanks there was a good 2" of grey clay like sludge in the bottom of each tank; we made him scoop them clean while we went to the bar...:)
 
Without access, it's virtually impossible to clean the tank properly. When I got diesel bug, in a boat with a deep narrow keel tank, with poor access, I used fuel polishing to get as much muck as possible out. As the tank was baffled, I couldn't get access to most of it. I found that if I pumped out say 20 litres of fuel through the polishing filters, then poured it back in the tank as quickly as possible, it stirred up some of the crud on the bottom, some of which then got removed on the next polishing cycle. So persistence pays off! The crud which remained on the tank sides and base seemed to be quite firmly affixed, if the crud on the fuel sender was anything to go by. An alternating regime of dosing with Marine 16 and Grotamar seemed to prevent further problems.
 
Petrol will probably dissolve any tarry-stuff.
But, then you have problem of removing the petrol.
If you have 'bug' there may be insoluble crud in there too.
I would have a look inside with an endoscope camera.

I would consider installing either an inspection port (which need not be very big) or a second pickup that draws right from the bottom corner of the tank. Then you can effectively remove any water in future and avoid problems.
One thing I've found effective is to secure something like an old rope end on a flexible plastic pipe and spin it in the tank with a cordless drill, to agitate the mess and flail stuff off the surfaces. Combined with polishing the fuel, it removed the vast majority of the mess in one tank we cleaned.
 
Have a word with Oiltechnics


www.oiltechnics.com


Their support team knows all about their range of biological products which eat hydrocarbons. I bet there's something you can pour into the tank, keep warm for a day or so, then suction out.
 
What about umm.....Gunk?

Buy a gallon from a motor factor, pour it in, bung all the pipes up, and give it a good sloosh round for a day or two.
 
It is worth knowing what the black substance is.

Case 1) If it's actually black, like soot or tar, then it's Asphaltene and Bituminous deposits which have become very common indeed since the introduction of Ultra-Low Sulphur Diesel (ULSD) which was introduced between 1998 and 2006 and is now mandatory pretty much everywhere incl US and EU. There's good evidence that these deposits are more prevalent when Copper are Brass is used anywhere in the pipework, but even without these it still happens a lot.

Case 2) If it's watery and soft goo, possibly red or brown, then it's microbial growth.

I've never had the latter, but have had the former, really quite bad. It was interesting because at the same time I opened two tanks on near identical boats, nearly exactly the same age, and neither of which had previously been opened and inspected (both around 8 years old). One, mine, let's call it Boat A, had only ever been filled with UK sourced red marine diesel, and so had never had any FAME, aka bio-diesel. The other (my brother's boat), let's call her Boat S, had been kept in Greece and filled up through her life with white road diesel to the usual dodgy Greek bowser standard. Both tanks were stainless steel. On opening, Boat A's tank was covered in a very thin but jet-black layer all over. Boat S's tank was spotless!

I took samples of the black stuff, mixed it in about 100cm3 of 50% water, 50% clean diesel and put the jar in the airing cupboard to grow. After 6 months, zilch; no growth at all. So it wasn't due to microorganisms (or they were deader than the Norwegian Blue).

I cleaned my tank with a home-made polishing rig and a bottle brush and then used road diesel thenceforth (actually not deliberate choice, it's just that I went abroad). The problem never recurred: on last opening, the remaining black stuff has been largely dissolved, I believe by the FAME. So my suggestion, supposing you believe your black stuff to correspond to Case 1) above, is to use road diesel for a while and very probably the black stuff will reduce. Contrary to the snake-oil salesman's advice I know!

Anyone else had similar (or indeed contrary) experience?

PS: For the avoidance of doubt, if you have any water in there at all, get rid of it now.
 
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Get a sample out and test various solvents on it : petrol, paraffin, Gunk, acetone?(with care), etc. See which works best.
BTW someone suggested steam from a hired wallpaper stripper. You can buy these very cheaply - I've just acquired one for a tenner of a local sale/sell website.
 
ghostlymoron said:
Get a sample out and test various solvents on it : petrol, paraffin, Gunk, acetone?(with care), etc. See which works best.
BTW someone suggested steam from a hired wallpaper stripper. You can buy these very cheaply - I've just acquired one for a tenner of a local sale/sell website.
Click to expand...

Good find. That's probably much less than I paid to hire one many years ago!
 
Work in progress:

I find I can tip the tank about 10-12°, making the fuel outlet tap the low spot - and I can shake it a bit ( until I re-secure it soundly ). There are two 1/2" spigots on top for fuel RETURN and for breather, a low outlet with ball valve and 8mm hose barb for fuel OUT, a 38mm right-angled fuel INLET on top, and a cranked pair of 1/2" spigots for a see-through fuel level sight gauge.

The ~4 litres of old diesel I extracted has swirls of brown/black powdery sludge. I take that to be 'diesel bug'.

Today I was able to cobble together a small carpet steamer with a rubbery hose, and introduced - in several cycles - watery steam in which a little kitchen detergent had been mixed. The dribbled outflow was collected bit by bit in a small tray. The initial fluid was opaque black/brown. Steadily, subsequent 'collections' largely cleared until the 'soup' was milky and half clear. Towards the end of the operation, larger flakes ( 3-5mm ) of black material passed through. The fluid was semi-opaque and milky.

I now have to rid the tank of residual water, and am wondering if blowing in warm air from a hair dryer/hose for half an hour or so would be effective.

I have made up a 'fuel polishing' rig from a recycled 4x4 filter unit married to a 12v pump. I have it in mind to half-fill the tank ( circa 16 litres ) then ''polish' this volume several times around, finally capturing/extracting some for inspection.
 
zoidberg said:
The ~4 litres of old diesel I extracted has swirls of brown/b.lack powdery sludge. I take that to be 'diesel bug'.
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I think that is an unwarranted assumption. Most black sludge in a tank is not the result of biological activity but simple chemical instability of modern diesel. References abound, look for Asphaltane. If it is indeed Asphaltane then steam cleaning will be pointless and a simple solvent will be best (and it's not that harmful anyway). Why don't you try cultivating the stuff in a jam-jar of water and diesel: I bet it doesn't grow!
 
If you think that you have made a partial clean on the interior surface, can you introduce your endoscope and check visually the condition of the walls ? If they are not shiny bright, then try the Sobo stuff for 24 - 48 hours, shaking tank from time to time.
 
sarabande said:
If you think that you have made a partial clean on the interior surface, can you introduce your endoscope and check visually the condition of the walls ? If they are not shiny bright, then try the Sobo stuff for 24 - 48 hours, shaking tank from time to time.
Click to expand...

That's a plan! And 'jdc' is quite right. I 'concluded' instead of 'considered'.

Now to find my el cheapo endoscope....

Oh, the joys of 'pimping' a sailboat!
 
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