static electricty

What are the fuel tanks made of ? I doubt you would be likely to have any problem as all metal on the vehicle should be at the same potential. A spark only jumps between parts at different potential.

If the tanks are metal and you put one hand on vehicle metal and one hand on a spare fuel tank - BEFORE you open any vent / filler - you should drain away any difference in potential between the roof fuel and vehicle fuel tanks.

I would be more concerned about parking over very dry grasses with a hot exhaust system !

There are some aditives that can be added to fuel which aids in the dissapation of static electricity. Someone on this forum may know more about them and where you can get them.

Hi Joe,
For me, there shouldn't be a problem provided,
1. Your roofrack is metal and attached to your vehicle.
2. Your vehicle is metal and attached to your roofrack.
3. Your fuel tank is attached to your vehicle.
4. You touch the vehicle before connecting hoses and opening the tank.

Why do I say all the above?
Everything that has the potential to generate a spark is joined together and at the same "voltage"
By touching the vehicle before you start doing anything to do with fuel you are ensuring there is no stored electrical energy in you, the tanks, the rack or the fuel tank.
If you receive a small "jolt" from the above that is good, you've just discharged the static buildup in everything concerned. Mind, no jolt is also good, there was no buildup to discharge!

Geoff.

if the tanks stay on the roof why don't you just syphen?

Joe

I carry explosives in vehicle for my work. Our regulations state that when refuelling, an earth wire be connected from vehicle to a sound ground - we use a suitable wire length with 2 alligator clips - connect one end to vehicle and other to an upright at the service station - if we use gerry cans for refuelling we would connect cable to vehicle and other end to star picket to ground (some guys even pour water at base of picket to increase conductivity) - use could use same principle here. Biggest thing, as mentioned above, is to discharge the potential your body may have built up by rubbing on seat covers etc - touch body work before opening fuel vessell

Cheers

Plastic fuel tank, rubber hose,, all on the same chassis, where is the problem?
Aircraft do it because the aircraft sits on rubber, and the bowser or truck is isolated from it. The problem is from you rather than the tanks etc. When you get a shock it is normally from getting out of your car and you are earthed then touch the car. Do that first, touch the hose on the car before starting and off you go. Notice that no petrol station requires you to earth your car first, but worksafe etc may for special circumstances

The problem exists because the fuel rubbing against itself will generate a static charge. This is in addition to any charge you may have built up by rubbing against seats etc. The charge will be generated while the fuel is flowing through the hose so this should be earthed while the refuelling is in progress.

I think the safest way would be to earth the car and the fuel line.

At work we use an air operated pump for transferring hydrocarbon fuels, ie petrol, from tank to tank. The hose has a metal wire coiled around it that is designed to earth the hose and reduce the static build up. In addition to this we insert a ground spike and use an alligator clip to earth the pump.

A similar arrangement should not be hard to come up with. Maybe use a tent pole stuck in the ground connected to the fuel hose via a wire wrapped around the hose a couple of times and clipped to the pole with a metal clip. A similar wire attached to the pole and the car would not hurt either.

Duncs

Geoff provided a farely comprehensive reply, but to answer one or two more points raised, here is my perspective.

I dont give a toss about regulations stating you must earth your vehicle to the ground. That sounds like crap to me. Does anyone do this when refueling from a bowser?

In Geoff's reply he is basically stating that because the fuel containers are on the roof rack and uninsulated from the vehicle, there would be no difference in earth potential and this is the critical factor, not whether the vehicle is grounded.

When necessary, I refuel from Jerry cans located in racks, on the drawbar of the trailer, using a "tanami" pump. Now, because I have a Tregg coupling, the only earth between the trailer and vehicle (to equalise earth potential) is the safety chain. This may be all that is needed, but for safety's sake, I have no problem in using a jumper lead cable to connect between the vehicle and trailer as an extra precaution.

Static electricity can be generated merely by the flow of fuel through the plastic delivery tube, thus the need to have the same earth potential between the container (where ever it is) and the vehicle.

Now, getting back to the local petrol station bowser, I have no idea how the potential is equalised. (If, indeed it is). Perhaps the delivery hose contains some sort of earth path (mesh) in the construction of its "rubber" hose to provide the link.

GDAY
BOWSER HOSES HAVE A VERY HIGH CONTENT OF CARBON AND SOME ALSO HAVE AN EARTH STRAP BUILT IN ,,SO THERE IS NO PROBLEM AT A BOWSER.
When the hoses are made , the earthing is checked with a multi meter .

I didnt mean to yell....sorry

But isnt the idea of the earth strap that the vehicle is earthed BEFORE opening or filling fuel?
What is the point of earthing the vehicle IN the filler with FUMES etc all around? Isnt this EXACTLY the moment and precisly the PLACE you DONT want it to cause a spark?
A spark or smoulder is very unlikely to ignite liquid petrol but a spark will easily ignite petrol vapour?

thanks for the replies I,very helpful