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My theory is that for instance in the case of a tanker refuelling an air craft, they are both earthed to a common ground to prevent any potential difference between them causing a spark. If they are not, as the fuel nozzel nears the tank a spark could jump the gap and ignite the fuel. Would the static electricity (potential difference), use the fuel as a conductor? or a conductive hose to complete the path to ground?
Fuel may be a conductor but I do not believe it would be used as the sole conductor to ground for earthing purposes.
Trev.
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When I filled up with Diesel at Charters Towers the other day they had an earthing strap for connecting to 44gal drums in the back of utes (plus a sign making it compulsory): locals were using it without any argument.
My Daimler Ferret handbook makes it clear that it should be earthed when refuelling and I use a chain from body to ground when doing so - especially as one of the guys had one flash and fire when refuelling.
It is a good principle to earth any container when being filled with fuel (metal of course - no point trying to earth plastic) to avoid the risk of a static discharge spark igniting the fuel/air mixture surrounding the fill point. Better safe than sorry with this stuff I think!
