Hey DT,

Wow!! That's amazing! What sort of relative humidity would there be
in the area. I would have thought that as the exterior surfaces of
the flex line began to cool, that it would form a heavier and heavier
layer of "ordinary" frost from the ambient room air. Is the LOX taken
from that frost? Or some other action? I guess if the frost built to
the point that it fell off, or the flex "flexed" and knocked it off,
then it would expose the super-cold surface directly.

Pretty interesting.

As a gruesome aside to what started this thread...many years ago near
Hamilton, Ontario, a semi-trailer tanker, with a tank diameter of only
about 5 feet, was rounding a corner too fast and rolled over onto its
side. It had a smallish cat-walk at the tank top around the filler
cap, which "hung out" from the tank top, due to the small diameter of
the tank. When the truck rolled, this cat-walk ended up laying right
into the passenger seat of a convertible car that was alongside. The
lady passenger was killed instantly, and other than the seat back
being pushed flat back, there was not so much as a scratch or a mark
on the rest of the car, not even the dash-board.

How come I always remember these gruesome bits??

Take care.

Brian Lawson,
Bothwell, Ontario.
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On 17 Dec 2003 21:09:57 GMT, (DT) wrote:


Actually quite real.
Nitrogen supercools tarmac.
Oxygen condenses on tarmac, soaks in.
Tarmac goes boom as it warms up, or a fly lands on it.


Interesting, although I don't recall any warnings about this in all my years of
working with cryogenics, though. LN2 isn't all that much colder than the
condensation temperature of oxygen (-270 F) but if the tarmac got to full LN2
temp (-320 F) it could work. Certainly LN2 doesn't cause oxygen to condense
appreciably in typical lab conditions.

Now, chilling from liquid hydrogen definitely does it. On un-insulated flex
lines, the LH2 (at -420 F) would condense oxygen and nitrogen directly out of
the air, and it would actually 'rain' in the vicinity of the LH2 lines. The LN2
tended to gas off fairly quickly, leaving it LOX enriched. If the droplets of
liquid air hit grease, you got little *poofs* as they ignited.

Note, temperatures are from memory, I don't have a chart handy.

DT