Strange crystals in diesel filter

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cpedw

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Needle shaped clear crystals, about 25mm long, were found in the pre-filter on a friend's boat today. They were a small quantity (perhaps 10 or 20) and they were only in the bottom part of the filter, below the glass bowl.

Looking at this thread http://www.ybw.com/forums/showthread.php?384585-Gritty-crystals-in-diesel suggests it may be connected with fuel treatment but these crystals look nothing like the ones shown in that thread. They used Fuel Set to treat their diesel this year.

Has anyone seen anything similar?
Is it something to worry about?

Derek
 
I would suggest its salt. diesel fuel will absorb a certain amount of water in the parts per million range dependent on temperature. maybe your diesel just absorbed some water and left the salt behind. i would not worry
 
Sorry no photo. It's strange that the only place the crystals were found is under the glass bowl.

Derek
 
cpedw said:
How? There's only one way in and out of the under-bowl space and that's through the bowl (apart from the drain plug).

Derek
Click to expand...

The glass bowl has a large diameter hole in the bottom. Any water separated from the fuel will drop to the bottom of the bowl, then fall through the hole into the space under the bowl.
 
I’ve read both the new threads on ‘diesel crystals’ (and the older one linked to in one of them), and I’m posting on this one as it’s the longer of the two. I’m not going to discuss the older thread as the crystals were differently shaped, and in a different place (the diesel tank).

In essence:

  1. The reports (taken together) are of long (25mm, i.e. one inch!) clear needles between the glass bowl and the metal base plate, in which the drain plug is located, and where any water from the fuel sits.
  2. The typical presumption is that they are salt crystals formed from seawater in the fuel.

Doubt has been raised about needle shaped crystals from seawater, as halite (NaCl) (usually) has a cubic, not needle-like, crystal form. However, calcium carbonate, not sodium chloride, forms first when seawater evaporates (e.g. http://www.ocean-sci.net/5/285/2009/os-5-285-2009.pdf) and I wonder if calcium carbonate is forming here, too.

There are two main crystal forms of calcium carbonate, calcite and aragonite, and the latter does have a needle form (which calcite does not). The above reference notes that aragonite is likely to be the dominant form between 8-40 degrees C, and calcite the likely dominant form between 3-8 degrees C. (If memory serves, organic substances can also affect the form of calcium carbonate which is precipitated, so organics from the fuel might also influence the form.)

In summary, I therefore wonder if what is being seen is the result of slow precipitation of aragonite in the relatively warm conditions of an engine space.

But that’s going out on a very long limb on precious little evidence, and my chemistry may be wrong, too. So someone may well come along in a moment to show that I’m barking up the wrong tree entirely, and give a more convincing explanation of this odd and intriguing puzzle!
 
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