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LP tank valve removal UPDATE
(Kevin Beitz) wrote in message . com...
Our local junk-yard cut up the old PL tanks everyday... They take a
hammer and bust off the old valve and light the escaping gas and start
the cutting immediately... So far no problems... I watched them do
this... I would not like to do it...
Automobile and light airplanes have fuel level senders in their
tanks. These are wirewound potentiometers that vary the current flow
to the fuel gauge. In many of them the float works a copper reed back
and forth, with a small graphite runner on its tip that runs on the
resistance wire. This takes place in a metal can with large holes in
it, so that all is immersed in fuel or fuel vapours.
The graphite wears out. The copper runs on the wire, chews it up,
and makes sparks. IN A FUEL TANK. IN FLIGHT. I have never heard of an
airplane blowing up due to this. The combustible mixture of gasoline
is 8% to 18%, and the mixture in the tank is much, much richer than
that.
We frequently find these senders worn out in our airplanes. I'm
never nervous working on the system unless we drain all the fuel to
remove a tank, and then I get really careful, as the mixture in the
tank drops into the combustible range. I prefer leaving a least a bit
of fuel in it and keeping the cap on as much as possible.
The most dangerous place is at the filler neck when the cap is off
and vapours are mixing with the atmosphere, which is why we once in a
while hear of fires caused by static sparks during fuelling. Airplanes
can accumulate considerable static in flight, or even on the ground
during a thunderstorm, or the fueller can make his own sparks in cold
weather by rubbing his jacket on the wing while refuelling. So we
ground everything.
Dan
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