I have been running commercially produced bio diesel in my backhoe for a decade or so. The backhoe does not get daily use, so fuel sits in the tank for a long time.
Recently I have been seeing a red flakey sediment in the sediment bowl. More recently the unit stopped working, running for a few minutes and then starving for fuel. I pumped the tank out and extracted the gunk shown in the photo; a red, waxy/polymer-ish substance.
When I pulled the access plate off the tank I found this stuff all over the tank walls. Idon't think it is a decomposing tank coating as I asked that question on some tractor forums. Here is what the tank looks like, after I scraped off what I could reach with a putty knife.
Notice there seems to be a 'waterline' mark where the fuel level must have sat for awhile. Above the waterline the stuff seems to be sort of flowing like melted wax.
Any ideas? Similar to a recent post, but a different color.
It's likely residual glycerol and soaps from the biodiesel
Time, oxygen, moisture, heat, poorly-made BD and contaminants in the tank present opportunity for the BD to degrade and gum-like by-products are the result.
If your experience is like mine was, you may find this gunk throughout your engine's injection gear and may necessitate an injector pump rebuild, along with stripping and cleaning fuel lines, fuel filter and maybe injectors.
I found that only some solutes will shift it. Gasoline, alcohols, kerosene and diesel will not dissolve it; Carb cleaner (toluene, acetone, methanol) is excellent and household cloudy ammonia is good too in the tank, followed by pressure washer.
The molecules are small enough to pass through filters with ease, and seem to settle out after the engine is turned off, hence they coat upwards-facing surfaces.
An expensive and time-consuming lesson.
The glycerol and soaps are dissolved in the residual methanol dissolved in the biodiesel so the solution goes right through filters.
Sodium Hydroxide caustic solution will dissolve the crud readily; the cheap oven cleaners work well too. Locate the lowest point in the fuel system and look for accumulations there. On some vehicles there is a screen on the fuel inlet pipe in the tank; it will be clogged with the crud.
Well, there you have two separate explanations. You will have to find which is true for you.
In my case it was not glycerol and soaps as none of it was water soluble, even boiling water. It was definitely a breakdown product of BD, and it always seemed to reduce down to an off-white powdery soft gum.
Incidentally I was told by someone who organises biodiesel production in the Pacific islands that storage of BD in unlined steel drums can also cause BD to degrade.
Thanks for the info! Glad to have the info on what will clean it. Not so glad to think about an IP rebuild!
I put the tank back in service with petrodiesel, so I'll see how it goes. As far as I can tell, the stuff is only precipitating in the tank. Sand size particles of it make it to the first sediment bowl and the inlet screen of the lift pump. I haven't seen it in the main fuel filter's clear sediment bowl, nor have I seen the off-white precipitate in the filter bowl. I have in cool temperatures seen what I thought was gelled fuel in the first sediment bowl.
The reaction that produces that material from biodiesel is auto-oxidation, where two biodiesel molecules become bonded to each other to form one molecule that weighs somewhere about twice as much and that as you see is largely insoluble in biodiesel. It precipitates out. Probably the larger molecule product can react again to form a larger molecule about three times as heavy as the starting material molecule. It's like polymerization. I believe the fatty acids that react are the ones with double bonds in them, I'm not sure about that part. If you do an online search for the key words "biodiesel autooxidation (spelling?)" that will pull up a variety of information about it.
Thanks WesleyB. Mine was not an off-white precipitate, it was dark brown gunk. It only ended up off-white inelastic gum after I subjected it to all the solvents I mentioned above excluding carb cleaner.
Yes I have similar experience w/ my boat fuel tank. See previous posts...
It is a light brown coloured gummy film that accumulates on the inside of tanks and likely anything else where B100 is in contact with (perhaps only where oxidization can effect it). I've noticed this film on the inner walls and bottom of my Stainless Steel boat fuel tank. I was able to access inside the tank with a wooden stick that had a chisel point cut onto it. I was able to scrape at it and film does come off, but not very easily / cleanly. This is not my only experience with said gummy film, we've probably all observed it were a BD spill has occurred (on our processing equipment) that eventually turns into a gummy brownish stain. I suspect it is the result of the B100 being exposed to air and drying out somewhat, concentrating it and eventually leaving an amber coloured, gummy film. Does this sound familiar? I can't believe others have not experienced this phenomenon. Maybe they're not looking for it?
Contrary to John Galt's theory of it being "glycerol and soaps dissolved in the residual methanol dissolved in the biodiesel" is unlikely in my case as I always water wash fuel a minimum of 6 times using 120% water to volume of BD & it tests for soap at around 30. PPM. I am more inclined to follow WesleyB's theory about "auto-oxidation".
Is this occurring inside fuel lines, pumps and injectors too? So does this mean we will all eventually have to clean these deposits from our fuel systems? If so I suspect this is something none of us Biodieselers have bargained for & will be difficult to perform.
I wonder if it would pay to seal off any air flow thru tanks, breather vents, caps etc when not in use to try to reduce oxidization?
BTW for about 3 years I have been using the antioxidant Baynox Plus http://www.biofuelsystems.com/...us_solution_data.pdf
blended into the BD during final phase of heated drying. However this issue with gumming & particles I have noticed for about 5 years. Perhaps I will inquire with Bayer about this issue.
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