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Old 4th Sep 2011, 11:07   #1 (permalink)
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flashpoint of JetA1

Hi, max. fuel temperature in the AFM or our aircrafts (Citation CJ1+/CJ2+) is described as +57 degrees Celsius. Given the fact that the flashing point of Jet A1 is at +38 degrees, I was wondering why max. fuel temperature is not also set at +38.

Inputs welcome,
Cheers
Cecco
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Old 4th Sep 2011, 11:34   #2 (permalink)
 
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Hi Cecco,

The flash point of petroleum is about -40degs C.
Have you never driven a petrol fuelled car in summer?
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Old 4th Sep 2011, 13:13   #3 (permalink)
 
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Cool

yes that's for petrol but jet fuel is around +60C
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Old 4th Sep 2011, 13:24   #4 (permalink)
 
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Cecco,

The flash point is the lowest temperature where the liquid gives off vapours that can be ignited by an ignition source. So even if the fuel temperature is above the flash point, it will not ignite by itself. That won't occur until above 200 degrees Celsius.
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Old 4th Sep 2011, 13:47   #5 (permalink)
 
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Many times the upper fuel temperature limit is a function of the fuel serving as a heat sink in the oil cooler.
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Old 4th Sep 2011, 14:51   #6 (permalink)
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@MarkerInbound

Can you specify that? You mean that above the max. fuel temp. the heat exchange fuel/oil doesn´t work properly?
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Old 4th Sep 2011, 15:13   #7 (permalink)
 
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Flash Point of JetA1

Cecco:

The flash point of Jet A1 is approximately 40 degrees centigrade,

The equivalent in Russia was called JT-1 which had a flash point of 28 degrees centigrade, so the risk was a little bit greater.

Tmb
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Old 4th Sep 2011, 23:05   #8 (permalink)
 
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The flash point is the lowest temperature at which the fuel vapor can burn in the presence of a continuous ignition source. If the ignition source is removed, the fuel stops burning.

The fire point is the lowest temperature at which the fuel vapor will continue to burn after the ignition source is removed...much higher than the flash point.

Both of these are specification standards; they are used to characterize a fuel's chemistry and behavior, not necessarily as specific safety thresholds. However, a higher flash point is used to distinguish a greater safety factor in storage and fuel delivery. The US Navy uses JP-5 for shipborne aviation because it has a flash point of around 62C.

Neither of these temperatures is related to the auto-ignition temperature, at which the fuel will spontaneously ignite and burn. This is generally much higher than the fire point.
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Old 5th Sep 2011, 02:09   #9 (permalink)
 
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Quote:
Can you specify that? You mean that above the max. fuel temp. the heat exchange fuel/oil doesn´t work properly?
Yes, think about it. If you had 65 degree fuel (granted, hard to get to but for an example) there is not going to be much cooling of the oil. Sixty five would be the lowest temperature but there is not a 100 % transfer from the oil to the fuel so the oil temperature will remain higher.
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