Freezing Fuel?

PhotoPilot

New Member
AVGAS won't freeze, but as it gets colder water that has been absorbed will seperate and either freeze or collect in the lowest point of the system. Jet fuel is very similar to diesel and can gel at low temps if the proper additives haven't been added.
 

pilot602

If specified, this will replace the title that
AVGAS will freeze. It's just very unlikely that it will freeze in the kinds of temperatures it would normaly be exposed to. Any liquid will freeze at some point.
 

Wm226

New Member
Thanks Guys!

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Jet fuel is very similar to diesel and can gel at low temps if the proper additives haven't been added.

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Out of curiosity, what type of additives are added to help prevent fuel from freezing?
 

avi8tor

Well-Known Member
There are different gardes of Jet Fuel. The difference between the grades is the Max. Freezing Temp., and the flashpoint. Some additives that can be added to jet fuel include anti knock additives, anti oxidants,and corrosion inhibators. For everything you ever wanted to know about Jet Fuel.

Click Here
 

PhotoPilot

New Member
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AVGAS will freeze. It's just very unlikely that it will freeze in the kinds of temperatures it would normaly be exposed to. Any liquid will freeze at some point.


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Agreed, but I seriously doubt that the temps found naturally on our planet would do the trick. Probably should have actually looked up the freezing point before posting, though . . .
 

sorrygottarunway

Well-Known Member
I wished they had mentioned something about prist in that link....

I'm getting the feeling that when people ask for prist, it is similar to when I ask for mayo on my sandwich at the deli.
 

EatSleepFly

Well-Known Member
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I wished they had mentioned something about prist in that link....

I'm getting the feeling that when people ask for prist, it is similar to when I ask for mayo on my sandwich at the deli.

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Prist is an anti-icing additive that lowers the freezing point of water.

Jet fuel contains small amounts of dissolved water. At altitude, the cold temperatures make it impossible for the water to remain in a dissolved state, so water can actually appear in the fuel as supercooled droplets. This is detrimental because it can freeze in lines and at filters.

Prist isn't very soluble in fuel, but it is in water. Therefore, when water particles form, the Prist is dissolved in it, lowering the freezing point to prevent it from freezing in lines/filters.
 

sixpack

New Member
The oil cooler on some Turbine engines is used to heat the fuel to prevent fuel freezing. Don't know the specifics because I don't fly jets (YET).
 

mtsu_av8er

Well-Known Member
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The oil cooler on some Turbine engines is used to heat the fuel to prevent fuel freezing. Don't know the specifics because I don't fly jets (YET).

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Actually, the oil cooler's purpose is to cool the oil (think radiator and coolant). It has a secondary purpose to heat the fuel somewhat, but it's not going to heat the entire fuel cell. It's only going to heat fuel that's in transit to the engine in question. So, it won't prevent the fuel in the tank from freezing - at all.

Does that make any sense?
 

EatSleepFly

Well-Known Member
Depends on the engine. The Garrett engines on a B100 have both an oil-to-fuel heat exchanger (to keep fuel from freezing on its way into the engine) and an oil radiator to keep the oil temps within normal limits.
 

mtsu_av8er

Well-Known Member
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Depends on the engine. The Garrett engines on a B100 have both an oil-to-fuel heat exchanger (to keep fuel from freezing on its way into the engine) and an oil radiator to keep the oil temps within normal limits.

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Wow...now that's neat!! Got any graphics to scan in? That sounds pretty neat, and I'd like to see some diagrams, charts....or just draw it, man!!!!
 

CAVOK

New Member
Since fuels are a mixture of hydrocarbons....the water in them (if any) is what will freeze at a relatively high temperature. The mix of hydrocarbons themselves all freeze at different temps...usually between -40 and -70 degrees C, and when a hydrocarbon freezes it becomes waxy (spelling?) like candle wax. So what happens is the fuel starts to freeze and gets chunks of "wax" floating around...as it gets colder it all turns into this "wax". Needless to say...the fuel pumps have trouble pumping wax, so that is where the problem starts. Our airline uses -40 C, as the "standard freezing temp" for the various grades of jet fuel we can use.


....Just got back from "Polar Operations Training" yesterday. I was anxious to type some of my new found knowledge
.
 

dakovich

Well-Known Member
ask anyone who drives a diesel car in the winter. the diesel gels up and if you don't use a fuel conditioner you'll be chillin on the side of the road waiting for the tow-truck
 

EatSleepFly

Well-Known Member
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Wow...now that's neat!! Got any graphics to scan in? That sounds pretty neat, and I'd like to see some diagrams, charts....or just draw it, man!!!!

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Mtsu, if you feel I'm incorrect, come out and say it and please feel free to back it up.

I made my previous statement based on what I learned in B100 ground school. This afternoon after coming across your unanswered question, I went back and found this reference in our Ground Training manual on the oil-to-fuel heat exchanger:

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An oil-to-fuel heat exchanger, located in the oil tank, regulates the fuel temperature automatically when the engine is running to prevent freezing of water that is suspended in the fuel. During engine start, the "Fuel Anti-Ice Lockout Valve" is energized closed. By so doing, fuel flow through the heat exchanger is temporarily stopped, thus providing increased fuel pressure to the engine while the engine speed is low.

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And this quote from the AFM/POH in reference to the engine lubrication system:

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A dry-sump high-pressure lubricating system is provided to lubricate and cool the compressor and turbine bearings and the reduction gearing. The system also supplies actuating pressure to the propeller control system and to the torque sensing components. Included in the system are a high pressure pump, three scavenge pumps, an oil filter with a bypass valve, a pressure regulator, and an oil tank. A magnetic chip detector forms part of the drain plug in the lower sump of the output housing. An external oil radiator with non-congealing capabilities keeps the engine oil temperature within operating limits.

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Unfortnately, neither of the engine schematics I have show this in detail, and I don't draw. Sorry to bring up an old post, just wanted to answer your question a little more thoroughly. If that doesn't answer it, I'll go bug the mechanics sometime for you.
 

mtsu_av8er

Well-Known Member
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Wow...now that's neat!! Got any graphics to scan in? That sounds pretty neat, and I'd like to see some diagrams, charts....or just draw it, man!!!!

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Mtsu, if you feel I'm incorrect, come out and say it and please feel free to back it up.

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Whoa....


I was being sincere!!! I really do think it's neat, and would like to see some diagrams...lol. I'm an engines and systems geek....I kinda dig that stuff!!!! No sarcasm in that one!!!
 

EatSleepFly

Well-Known Member
OK, just thought it sounded a little condescending, thats all...


Anyhoo, I'll ask a mechanic tomorrow just to make sure its not a mistake in the training manual.
 
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