On Jan 8, 9:36*am, Tim Watts wrote:
harry wrote:
On Jan 8, 12:26 am, wrote:
On Sat, 07 Jan 2012 01:04:13 +0000, Steve Walker

wrote:
Not always a good idea to have electrical conductors in flammable
liquids..

That's when you use intrinsically safe devices and either zener barriers
or galvanic isolators - restricting the voltage (typically 28V dc max)
and current (typically 20-odd milliamps) so that there is not enough
energy supplied or stored to ignite any vapours.

I'd understood the vapour concentration in a typical petrol tank was
too high for explosion risk. Otoh, it's not entirely unknown for one
to go up.
Years ago I saw a pic of static discharges in an Avgas tank - slightly
worrying.

When refueling aircraft, you are supposed to connect an earth lead to
them before you start. Especially important if they have just landed.
The rubber dispensing hose is a special antistatic job too that has to
be tested regularly. *It is of a resistance to discharge any static
electricity but not so low a resistance to cause a spark.
Fuel vapour is displaced out of the tank as the fuel goes in.

Surprised they don't have a vapour recovery system...

What do you do with it after you have recovered it?