Gritty crystals in diesel

[Cap'n Creosote]

I took the diesel tank out of the boat to fit a new feed to the Taylors cabin heater.
Today I tried to syphon the last dregs out of it and open it up. But the 8mm! pipe supplied with the Pella suction pump, blocked up. It's a 7gallon plastic tank so it was quite easy to open the top and pour the remnants into a container. There was some evidence of diesel bug, but what was blocking the pipes and left behind in the tank was this stuff, hard gritty white crystals. What is it, and where has it come from?

http://www.tanygraig.force9.co.uk/John/odds/Diesel_crystals.jpg

2 years ago I had the tank out for other reasons, and it was perfectly clean when I replaced it. I have occasionally dosed the tank with Starbrite diesel treatment. I've noticed this stuff tends to crystallise around the cap, the bottle is rather old. Could the crystals have come from there.

 

[robmcg]

Not been smuggling crystal meth have you? Not had any residue in our tank from using Startron, could the deposits have come from filling up from the marina (ie from their tank)?

 

[Cap'n Creosote]

could the deposits have come from filling up from the marina (ie from their tank)?

I suppose a contaminated supply is possible. If it was rust or sand it would have seemed the most likely explanation, but crystals? they look as if they were growing there.

There was about a small eggcup full.

 

[robmcg]

Or they were growing in the marina tank and ended up in yours during the transfer?

 

[Cap'n Creosote]

Or they were growing in the marina tank and ended up in yours during the transfer?

I hope you are right and it's not something which will precipitate out of the diesel after it has passed through the filters.

 

[macd]

Salt crystals? They Look the right shape.
I couldn't find any reference to NaCl's solubility in diesel, but it barely dissolves in some surprising solvents (such as acetone). Easy enough to check.

 

[vyv_cox]

Salt crystals? They Look the right shape.
I couldn't find any reference to NaCl's solubility in diesel, but it barely dissolves in some surprising solvents (such as acetone). Easy enough to check.

Beat me to the same suggestion. Looks just like salt to me. Many floating diesel bunkers in ports and harbours are contaminated with seawater, the likely source.

 

[jwilson]

Beat me to the same suggestion. Looks just like salt to me. Many floating diesel bunkers in ports and harbours are contaminated with seawater, the likely source.

Could it be that the fuel bug treatments have extracted the pure water from seawater contamination and created crystals of salt.

 

[Cap'n Creosote]

Could it be that the fuel bug treatments have extracted the pure water from seawater contamination and created crystals of salt.

That's an interesting idea. I don't know if that's possible. My chemistry isn't up to it.

There was no visible water in the tank or the glass bowl of the filter, but there was a small amount of black sludge typical of diesel bug in both.
There must have been water at sometime for the bug to grow.

I put a few of the crystals in a small quantity of tap water and they dissolved immediately.

 

[Leighb]

I put a few of the crystals in a small quantity of tap water and they dissolved immediately.

Did you taste it? Salt is pretty distinctive, a tiny bit on the tip of the tongue, might give the answer, though I suppose the diesel might mask it.

 

[LittleShip]

I've seen this twice before, once on Little Ship and once on a friends boat. We came to the conclusion that it was salt. Probably as suggested from the water being removed and leaving the crystals.

First time I came across it a large crystal had completely blocked the fuel line, when it was removed it was clear and resembled a cut diamond.

Not a clue how to prevent this and will look forward to suggestions....... Other than add water to dissolve them :ambivalence:

Tom.

 

[jwilson]

Thinking more about my original suggestion that fuel bug treatments had absorbed the pure water from some seawater in the tank, leaving salt crystals, could it also be that diesel had been used with some % of ethanol in it. AFAIK ethanol and water are miscible.

When I opened up my tank after 6 years use, I extracted about a pint of very dirty black water from the bottom. As the take-off was above this none had ever got to the filters. I had till then never used any diesel bug treatments, though I put some Marine-16 in after this.

 

[Cap'n Creosote]

When I refuel the boat I always fill two 5gall jerry cans and top up the boat's tank when necessary. I use one of those cheap syphon thingies, it's a rigid pipe with a squeezy thing on the top and a flexible pipe to push into the tank filler. The rigid part of the pipe isn't quite long enough to reach the bottom of the jerry can, so there's always a pint or two of diesel left in the can. This means I should never lift any crud from the bottom of the cans into the tank. And if the salt crystals had come from a marina tank there should be some traces left in at least one of the cans.

Today I completely emptied both cans through a funnel with a gauze filter there were a few flakes of paint, a little bit of muck, but no trace of any salt crystals.

I'm beginning to agree with the suggestions that the salt came in as salt water and somehow the water has vanished.

During the 2012 season I did refuel quite a few times with "white" diesel from the ordinary petrol stations. I wonder if this stuff would absorb the water leaving the salt behind? Does road diesel have any ethanol in it?

Interesting that Tom has seen this twice before, makes you wonder if it's more common.