Gary Casey wrote:

One thing I just remembered - It is EXTREMELY IMPORTANT to ground all

electrical

devices in the fuel system and ALL LINES WITH FUEL FLOW IN THEM MUST BE

MADE OF

CONDUCTIVE MATERIAL.  As Norm said below, fuel is non-conductive and that

means

that skin friction will allow it to build up a static charge.  This

charge can

build to very high voltages and has been known to arc through the fuel

line.  The

fuel tank itself probably isn't a problem as the flow in it is

essentially nil.

Don't let the appearance of some automotive plastic fuel lines fool you -

they are

made from a special conductive plastic - filled with either metal or

carbon.  If

the fuel pump is in the tank run a ground wire from the housing of the

pump, not

just the negative terminal of the motor.  All this is especially

important on EFI

systems as there is a continuous high fuel flow rate in the system.

Bill Freeman wrote:

 All certified aircraft use flex lines in the fuel system that
are not intentionally
conductive.  Certainly the metal reinforcement in them MIGHT contact the
fittings on the
end, and MIGHT ground the braid, but the liners are rubber or teflon and are
not made
conductive.   It is important to use conductive fuel hose for refueling, so
the nozzle
is at zero potential, but this is only because there is a fuel-air mixture
at the tank neck, outside
of the tank.

Inside the tank the fuel mixture is too rich to ignite, and liquid fuel is
not going to ignite
either.  The only dangerous fuel tanks are the "empty" ones, i.e. with a
shortage of fuel
to cause a richer-than-flammable mixture, so the mixture can fall into the
flammable range.
Grounding your pumps is a very good idea.

Bill

 
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