Milky diesel

[sailmaryann]

I have diesel in my tanks that is very milky. I have a polishing unit, and 3 levels of Racor filters, but after an absence of just 2 months, the diesel that was clear before I left turned into a dark milky solution.
After numerous attempts at solving the problem, I found that heating the diesel fixed the problem, and the now clear diesel remains clear for several days. I am still testing if it becomes cloudy again after a while. Heating by just 10 degrees centigrade more fixes the problem (from 30 to 40 degrees), and this I can achieve by putting the diesel in the sun here.
I suspect the issue to be paraffin wax, which may have been part of a 'winter' diesel supply at the place I tanked up last time (5 months ago). This is surprising as I am in French Polynesia, but it may be a case of a supply destined for Australia.
Anyway, I am now planning to empty my 700 liter tank into drums that I will leave in the sun for a day or so before putting it back into my tanks. I hope this will fix the problem...

My question is: Has anyone experienced this before? What causes it? Is there a better method than the one I plan to implement?

Thanks for any help on this.
Olivier
SY Mary Ann

[StuM]

If it's got a "cloud point" around 30°C, it sounds like some form of bio-diesel, not fossil fuel. (They didn't fill you up with coconut oil did they? That's about the right temperature for that )

[MartinR]

If this would be paraffin related, then the diesel would be bright and milky, not dark. And winter fuel has a lower cloud point than summer fuel, so the chance of clouding is much less. Paraffin clouding is easily countered by adding a few percent of kerosene to the fuel.

I see two possibilities. The first is contamination with Bio-Fuel. Not perfect, as you absolutely do not want to have this in your tanks, it promotes fungi and bacteria growth.

Secondly, if you bunkered from a barge or a shore installation that caters to fishing boats/coasters, then you probably received Marine Diesel Oil (MDO) instead of Marine Gas Oil (MGO). Check with the supplier! Marine Diesel Oil needs slight preheating and must be run through a separator, so is not useable on a yacht. If you have a big old engine, you might be able to run on it, a modern engine is likely to be damaged.

[GordMay]

Greetings and welcome aboard the CF, Olivier.

[Diesel Bill]

Years ago we took on board some several thousand gallons of marine diesel oil to run 6 diesel engines on deck to off load wheat in Estonia. I remember the fuel was a much darker brown than #2 diesel. The deck engines appeared to start and run O.K. They were
Cummins 5.9 12 valve older models with inline jerk pump style injection pumps. No electronics in the fuel system. It just seemed to be a lower grade than #2 D.F.M.

[sailmaryann]

Originally Posted by StuM

If it's got a "cloud point" around 30°C, it sounds like some form of bio-diesel, not fossil fuel. (They didn't fill you up with coconut oil did they? That's about the right temperature for that )

Could be biodiesel, although I tanked up at a Total station at one of the marinas in Papeete, French Polynesia.
One question remains however: Upon heating to about 40C , the stuff clears up AND REMAINS CLEAR even when returning to 30C.
I am not complaining that it stays clear, as it means I can use it, but I am wondering why it would become stable all of a sudden, after having clouded up in the first place?

[sailmaryann]

Originally Posted by MartinR

If this would be paraffin related, then the diesel would be bright and milky, not dark. And winter fuel has a lower cloud point than summer fuel, so the chance of clouding is much less. Paraffin clouding is easily countered by adding a few percent of kerosene to the fuel.

I see two possibilities. The first is contamination with Bio-Fuel. Not perfect, as you absolutely do not want to have this in your tanks, it promotes fungi and bacteria growth.

Secondly, if you bunkered from a barge or a shore installation that caters to fishing boats/coasters, then you probably received Marine Diesel Oil (MDO) instead of Marine Gas Oil (MGO). Check with the supplier! Marine Diesel Oil needs slight preheating and must be run through a separator, so is not useable on a yacht. If you have a big old engine, you might be able to run on it, a modern engine is likely to be damaged.

Actually, the cloudy diesel is not really dark, but rather strongly milky is what I meant. I tried to use aromatic solvants, and it works with white spirit - I couldn't find any BTX here, and have not found kerosene, which I would probably not want to use in a diesel engine anyway?
I had the diesel analysed by a lab, and it came back with 0.45% water, and no trace of yiest or bio development. I do add biocide every time I tank up.
I tanked up at a Total gas station that serves the boating community in Papeete, French Polynesia. This station has a huge output, and I don't think they would sell MDO.
My engine is a mecanical Nani diesel, which is a Kubota base. No electronics, so it can run on pretty rough stuff, but if I let this cloudy stuff settle, it becomes almost like mayonnaise. When I returned after my 2 months absence, the glass bottom of my primary Racor was full of that stuff, and I only noticed after my engine stalled. I have since purged everything, and the engine runs fine on clean diesel. I have not yet tried to run it on the heated, clear stuff.
Any further idea?
Aprreciate your help Martin.

[MartinR]

If you got it from a Total pump, then it is in all likelihood normal diesel fuel.

Probably you have growth in the fuel. Bacteria, fungi, microbes. You could try with additives for killing these. And when the tank is empty, a thorough cleaning.

Google "diesel bug" and look at the pictures, does this look like yours?

[MartinR]

Sorry, I replied while you were writing your answer.

[MartinR]

The water content is high, I just checked some spec sheets, and the normal limit for diesel is 200PPM, yours is 4500. That might explain it somehow, but I am a little baffled if they could not find any growth in it.

There is always the possibility of some other contamination. Did they check the cloud point and cold filter clogging point?

[sailmaryann]

No it is definitely not diesel bug. I have had that too in the past (I am a liveabord and have been sailing around the world for the past 10 years now, so I've had my share of Bahia problems. If you are familiar with ouzo in Greece or Pastis in France, this is exactly how it appears. I first suspected water, but normally a diesel/water emulsion is not stable, and this is.
I agree 4500ppm is on the high side, but again, what makes this a stable emulsion? Besides, why would it clear at 40C if it is a water emulsion?

On another note, among the tests I have run:
- Add cooking oil: No clearing up until it sits in the sun and reaches 40C
- Add 2 stroke oil: Some clearing up, but fair amount of sludge at the bottom. Clears up in the sun, sludge remains
- Acetone: Some clearing up, slight coating at the bottom, clears up in the sun.
- White spirit: clears up, slight coating at the bottom, clears up in the sun.
- Gasoline: No clearing up until it sits in the sun.

After being heated, my samples have sat in the shade at about 30C for about a week now, and have not clouded up again. It may still happen over time, I don't have enough distance yet.

The lab did not run a cloud point or a cold plug filter point.

Lastly I have added triple the recommended amount of biocide after this first occurred, and see no effect.

Thanks for your interest and help.
Olivier

[DeepFrz]

Check to ensure that your fill cap o-ring is not damaged and the cap is on tight. It sounds to me like you have taken on water and the o-ring is a prime suspect. If you can run it through a water separator you may save yourself some work. If your boat was left in the water that could explain the water and fuel mixing. Draw off a sample from the very bottom of the tank and see if you have a layer of water.

I suppose the fuel you took on had water in it but I suspect it most likely happened in your tank. Good luck.

[MartinR]

Actually a water emulsion looks like Ouzo......

Biodiesel in the fuel or some kind of detergent contamination would help keep the water in emulsion.

[sailmaryann]

Originally Posted by DeepFrz

Check to ensure that your fill cap o-ring is not damaged and the cap is on tight. It sounds to me like you have taken on water and the o-ring is a prime suspect. If you can run it through a water separator you may save yourself some work. If your boat was left in the water that could explain the water and fuel mixing. Draw off a sample from the very bottom of the tank and see if you have a layer of water.

I suppose the fuel you took on had water in it but I suspect it most likely happened in your tank. Good luck.

Thanks for that input, however...
As I stated initially, I have a polishing unit on board (Reverso FPS 60, 60 gallon/hour) which I have been running several hours a day since this happened, with regular purging. I must have turned over my diesel at least 15 times by now, and I do find a tiny bit of water in the separator, but hardly any by now.I also fill my daytank from the main tanks via a Racor filter, and purge that regularly. A third Racor is installed between the daytank and the engine (and another one between the daytank and the generator), and is purged regularly as well. No water there, but cloudiness remains.

If it were water, why would it clear up with just a 10 Degrees C change in temperature? Does that sound consistent with water?

Thanks for your interest and help.
Olivier

[thinwater]

Pollishing an emulsion will only make it more stable. Stop.

Heat is one method. Another is emulsion breaking chemicals. Most are commercial, but try Startron Diesel and a little time. It often induces a clean break. Of the common additives, it did best. Of course, if there are other additives in the tank, all bets are off.

Let us know.