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DEF fuel contamination

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Posted by Overmod on Tuesday, August 6, 2019 12:42 PM

CSSHEGEWISCH
The dye in diesel fuel is related to the payment of the appropriate fuel taxes when the fuel is intended for over the road use.

The point is that the dye doesn't compromise the fuel stability in storage, or clog the injectors, or change the gelling point.  Why would a properly-chosen chemical counterpart cause destructive engine changes in the DEF system?

This is a drift from pure railroad subjects, but it might be expanded to some railroad contexts if SCR becomes more universally adopted and 'some other' colorless fluid becomes confused for the DEF.  We have already seen some pretty catastrophic consequences (mechanical, operational, and financial) from the mandated "100% derating" of diesel engines when there are issues with the SCR system: something even the Government wouldn't dare do for an aircraft application. 

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Posted by tdmidget on Saturday, August 3, 2019 11:59 PM

So, are you worried about locomotives falling from the sky, or what? I can't see this having anything to do with rail transportation. It does reflect badly on the aviation community, especially general aviation if the caliber of people that they hire are this bad. But nothing to do with rail.

 

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Posted by Overmod on Saturday, August 3, 2019 9:04 AM

Shadow the Cats owner
The problem is if you dye the DEF fluid any color it clogs the SCR system injectors and then causes massive other problems in the entire emission system of the truck.

That's as silly, chemically, as thinking that gas-blanketing an unbaffled long tank has an effect on slosh, physically.  (Of course, you'd have to pick a dye that would disperse properly, not elevate the slush/freezing point of the fluid, and not induce an effect with any constituent of the DEF, but that isn't going to be a particularly difficult exercise, considering the physical dimensions of the SCR injection system and the active ingredients in the fluids used for 'best effect' in them.)

Note that any possible clogging effect at a metering orifice will be reduced if the flow is increased, as it should be when the engine is redesigned to take advantage of 'mandatory' SCR by eliminating truly stupid kludged excuses for NOx reduction like EGR, and then tuning for higher CR and full pilot injection.  Of course as long as we have twentysomething diesel-phobic wannabee-do-gooders in the line and staff of regulatory agencies, don't expect to see this common sense publicized, even though they sure love to publicize the idea of mandatory SCR in other contexts!

...you can do what the OTR industry has done on our bulk nozzle delivery system at truck stops. There's a magnet in the filler neck of the DEF tank. If the nozzle doesn't make contact with it then it won't turn on the pump. Doesn't matter if the stuff is being dumped in from a box or bottle however.

That's just the problem ... common sense goes out the window if there's a nickel to be saved somewhere.  I'd note that an earlier common-sense mechanical screwup preventer, the intentional restriction of fill nozzles for unleaded gasoline, could easily be adapted as a kind of box-or-bottle solution: shape the cap and connections on the box or bottle to standardized forms or colors that make even tired low-wage workers think when they pick the bottle up, and include a simple plastic latch like a proper version of the catch on medicine bottles to make them think again when they go to open it.

I'd note that you could also design the containers for one of these fluids -- the de-icing fluid would be my choice for logistic reasons -- to require a removable hose and dispensing nozzle with a (now passive) magnetic release, or even just a mechanical catch of the sort that Wile E Coyote super-geniuses keep "designing" for emergency gas cans, but workable for a change, so that at least it would be fully recognizable when some idiot goes to the flight line kludging a refill.  The specific issue of how you redesign the fuel fills on aircraft, which may or may not be amenable to the same magnetic provision that OTR trucks are -- this could easily be researched -- as some kind of mandatory directive then becomes a safety-related action that might, actually, drive an effective mechanical solution.

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Posted by CSSHEGEWISCH on Saturday, August 3, 2019 6:56 AM

The dye in diesel fuel is related to the payment of the appropriate fuel taxes when the fuel is intended for over the road use. 

The daily commute is part of everyday life but I get two rides a day out of it. Paul
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Posted by Shadow the Cats owner on Friday, August 2, 2019 10:45 PM

The problem is if you due the DEF fluid any color it clogs the SCR system injectors and then causes massive other problems in the entire emission system of the truck. So it's a catch 22 you can do what the OTR industry has done on our bulk nozzle delivery system at truck stops. There's a magnet in the filler neck of the DEF tank. If the nozzle doesn't make contact with it then it won't turn on the pump. Doesn't matter if the stuff is being dumped in from a box or bottle however. 

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Posted by Overmod on Friday, August 2, 2019 6:59 PM

blue streak 1
DEF may get into jet fuel with bad consequences.

Let me get this straight: the whole Midwest is full of morons spot-checking for red diesel sneaking where it shouldn't be, but they won't dye the DEF green or some other non-confusable color.  And nobody in aviation thinks of dying the special aircraft de-icing inhibitor?


As my grandfather said, this sure isn't the America I grew up in.

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Posted by Flintlock76 on Friday, August 2, 2019 3:56 PM

Oh, brother...Bang Head

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