Thursday, 21 November 2013

1.8 Dangers of electrostatics (sparking, earthing etc...)

Check out this full explanation I found on a revision website...

 http://www.gcsescience.com/pse7-electrostatic-charge-spark-fuel-fire.htm

How can Fuel Flowing through a Pipe cause an Explosion?
Care must be taken to avoid sparks when putting fuel in
cars or aircraft. The fuel itself is an insulator (a hydrocarbon)
and charge can be transferred as the fuel flows through
pipe if the pipe is also an insulator. The transfer of charge
happens because there is friction between the fuel and
the pipe. As the nozzle (the end) of the pipe is brought
close to the fuel tank, a spark can jump between the two
igniting the fuel. This can cause a serious explosion,
particularly with aircraft which are filled at a very high speed.
The spark can be avoided if the pipe nozzle
is made to conduct by connecting an earthing strap to it
and so any charge can be safely conducted away.
An earthing strap connects the pipe to the ground (the Earth).
In addition, a cable can connect the pipe to the fuel tank,
so that there can be no difference in charge between them.

There's also a nice animation on the BBC bitesize page...

http://www.bbc.co.uk/schools/gcsebitesize/science/add_edexcel/static_elec/staticact.shtml


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