Sunday, Sep 13, 2009 at 20:30
G'day fisho,
You are partially correct. Your car isn't earthed fully. The carbon in tyres will allow leakage to earth but it is a high resistance path and the discharge can be slow. Your car can build up a static charge and then, just like a capacitor, store that charge for a while. If you place an earthed nozzel to a statically charged car it could create a spark, and susbsequently a fire.
For this reason, the "earth" of the bowser should also be resistive, acting to limit the current flow. Fuel tankers actually earth the vehicle first, before any other actions take place, in order to eliminate static.
The poor chap in this scenario may have been a victim of heat or static. Generators have rubber feet for vibration damping. Thus a generator can also build up a charge. The gerry can can also be charged. A spark could occur when the two items are brought into contact and the charge in each tries to equalise. If the generator was earthed (and it is recommended that generators are earthed for electrical safety reasons when operating) and the fuel container was placed on the ground for a few seconds, then you could eliminate static being an issue in this instance.
In the circumstance described above, the fuel vapour still had to be in contact with something hotter than its flash point. That might have been the generator exhaust system, or it might have been a spark from a discharge. The investigation that follows may reach a conclusion about which it was but in the mean time we should all be aware of any likely causes of fires like this.
Cheers
russ
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