Static electricity and refuelling?
Submitted: Saturday, Jul 12, 2008 at 19:56
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Member - V8Diesel (WA)
Hi,
further to a previous post, I thought I'd start a new one on this topic so it's easy to find in a search.
If I am filling a steel 44 gallon (205l) drum on the back of a ute or trailer, exactly what should I earth and to where?
I was thinking about running one of my jumper leads from a scraped bare metal section of the drum down to a copper rod pushed in to the ground where possible or jammed under the tyre. That's how I used to earth generator trucks and it was considered standard practice at the time.
I am assuming the pump and nozzle are earthed and the flow wont build up a charge as otherwise we'd all be in strife.
I know in helicopters they clip a earth strap on to the airfarme first.
I should also point out I must have put at least 30,000 litres of fuel in 44's at one time or another without a problem.
On another note, two of us used to lock fingers and lift full 44's up on to the back of HJ75's. To get them down we'd just dump them off the edge on to 7.50 x 16 tyre. That's why I'm a cripple now I guess.
Reply By: Member - Graeme W (NSW) - Saturday, Jul 12, 2008 at 20:24
Saturday, Jul 12, 2008 at 20:24
When I worked on helicopters, the copper rod into the ground or the earth lead from the aircraft under a skid was generally accepted practice when away from base and nothing else was available. A nearby drainage grate could also be used if available, to clamp the earth lead to.
Procedure was: aircraft to ground, tanker to ground, tanker to aircraft. The person carrying out the refuel would dissipate any static from themselves through this process, simply through connecting the earth leads to ground.
I would think the process you've described above would be more than adequate for fuelling drums.
I would assume though that vehicles could still build up a fair bit of static, so it's better to be safe than sorry.
As an example, if the rescue sling from a helicopter was lowered to you and you simply reached up to grab it, you would quite possibly find yourself sitting on your backside from the static build up jumping to your outstretched hand. Letting the sling touch the ground and standing on it would dissipate the static.
Graeme
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315014
Reply By: Member - V8Diesel (WA) - Sunday, Jul 13, 2008 at 08:55
Sunday, Jul 13, 2008 at 08:55
OK, what if I just dragged the nozzle on a bare metal part of the ute / trailer, then did the same thing on the drum. Surely that would dissipate any static charge? Even just touching everything first should do it.
As I mentioned earlier, I have filled countless 44's on the back of utes in all conditions. You'd think if it couldn't build a charge travelling 1,000km's in dry desert winter air, then it wouldn't do it.
While I'm thinking about it. What about detonators? I've lugged heaps of them all over the place too and you just pick them up. Surely that would be a prime case for static discharge danger. You can't use two way radios anywhere near them by law, but I've never had to carry an earth strap in the vehicle.
Hmmmmmm..........the obvious question still remains - what is the difference between filling a drum on a vehicle and refuelling the vehicle itself? I've had plenty of static 'zaps' from cars. I had a Fairlane that was notorious for doing it.
AnswerID:
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Follow Up By: Mike Harding - Sunday, Jul 13, 2008 at 09:29
Sunday, Jul 13, 2008 at 09:29
>As I mentioned earlier, I have filled countless 44's on the back
>of utes in all conditions.
The problem is... you have to be right every time... the static only has to be right once.
A post above raises the valid point of the vehicle not being earthed and he's quite correct but usually when the driver alights from the vehicle he discharges the static to earth through his body - if it's a high charge you'll feel the familiar Zap! If the drum is sitting on a mat in the ute it may not be discharged
There have been a number of petrol station fires in the USA caused by static, some have been shown to be due to women getting back into the car for their handbags which charges them up again, when they get out and touch the filler area a nice spark jumps across between the vehicle and their fingers through all that petrol vapour = boom.
When I fill up, I get out of the car place one hand flat on the paintwork above the filler area and the other on the metal of the pump nozzle (whilst the nozzle is still on the pump) I then pick up the nozzle by the plastic handle and fill up - easy, quick, simple and safe. You could do the same with the drum.
Mike Harding
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Follow Up By: Dave(NSW) - Sunday, Jul 13, 2008 at 09:51
Sunday, Jul 13, 2008 at 09:51
It's the static from the fuel dropping into the drum you have to worry about, That's why you should use an earth strap.Fuel flows into your car down a filler pipe and doesn't create as much static so filler nozzle is enough earth.
Dave..
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Follow Up By: Member - Paul C (NSW) - Sunday, Jul 13, 2008 at 18:20
Sunday, Jul 13, 2008 at 18:20
I could be wrong here but the charge of coulombs is built up whilst the flow of fuel is at high levels. ie whilst being pumped.
A lower flow would not be able to build up enough charge to create a spark between materials at different potentials. The charge would be dissipated relatively quickly once the trigger is released.
A good example of this is "sucker" trucks which vacuum dust through suction hose with reinforced metal spirals. Exposed metal can give a shock whilst suction is present with dust flowing. Turn off the suction and you will not get a shock because the friction required to provide enough coulombs to create a spark is negated.
I have spent hours tracing circuits to find the cause of electrical shocks only to find exposed metal spirals in a suction hose is the only likely culprit.
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