I know that airplanes are grounded upon landed before they are refueled. Why not cars too?
Dont planes build up a huge amount of static when flying through the air?
I thought that tires are designed to have some amount of conductivity, so that the car isn’t entirely insulated from the road – precisely for this reason. Unfortunately, I can’t find a cite… all I remember specifically is an old physicsland homework problem involving exactly this. Specifically, it was to determine how much time before a static charge would dissipate after stopping, given tires of resistance x, so that a race car could safely be refueled. Or maybe the other way around…
I believe the fuel hose has a metal mesh protective sheath that is connected to the fill nozzle and the pump. That would act as a grounding line.
Um… but isn’t earthing via the fuel nozzle exactly what you want to avoid? Surely that would potentially lead to a spark jumping from the car body to the metal fuel nozzle, which is where the fuel is at?
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Also, isn’t the word “nozzle” utterly ridiculous once you read it a few times?
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You could make a fairly convincing argument that perhaps cars should be grounded, but you are fighting a hundred plus years of history where folks have thought that they haven’t needed to be grounded. You are going to face a lot of reluctance to the idea, especially from the guys who have to pay for the grounding equipment.
Cars are dealing with much less fuel than airplanes, so any resultant BANG isn’t likely to do anywhere near as much damage. However, pump fires do happen. A handful per year (a pretty small number considering how many millions of cars there are out there filling up every day) are generally caused by things such as static discharge, which could be prevented by grounding the car before fueling. The ground that’s in the nozzle that David mentioned doesn’t always help, because sometimes the discharge is between the car and the nozzle as you are getting the nozzle near the car, and the gas that’s left in the nozzle from the previous customer ignites. There’s usually only a few drops of gas left in the nozzle, so while the guy fueling may have to change his shorts afterwards, there’s generally not much harm done. Another common occurance is that the driver builds up a charge and then touches the car near the nozzle, and ignites the vapors nearby. This occurs more often with women than men. Men are more likely to just stand outside in the cold and fuel their cars. Women are more likely to go back inside the car when it’s cold, or to grab their purse or cell phone, etc.
A little education about static discharge among the general public would probably go a long way towards reducing the handful of pump fires that do occur every year.
Regulations (in Michigan, at any rate) require gas cans to be filled on the ground, as opposed to (say) a pickup bed or the trunk of your car, ostensibly for static charge issues as mentioned.
In the military, field refueling operations were always grounded, i.e., a metal clamp was attached to a metal part of the vehicle; the metal clamp was cabled to a ground rod that the fuel operator had to figure out how to drive six feet into hard clay.
Grounding straps… are these this the answer to a question I have had?
Every now and then I see a car with a strap hanging freely down from the rear bumper or frame, between and behind the wheels. There is a small triangular emblem attached to it, point up. The strap is long enough to just touch the ground.
What are these straps?
If you have a plastic gas can in a plastic bedliner you can get enough static build up to start a fire when the nozzle is removed. This happened in the pits at Willow Springs Raceway one year. Guy filled a 5 gallon plastic fuel jug from pump with the jug in the back of a pickup. When he removed the nozzle it flashed off. Very spectacular. Race was red flagged and Fire 1 (the big truck) rolled. luckily there was a clear thinking individual who grabbed a very large CO2 bottle and got the fire out before the place burned to the ground.
I used to own a small plane. I wonder if the grounding is related to the fact that you are being refueled from a truck, who itself is somewhat insulated from the ground by its tires?
I actually had to smile every time they tried to fill up my plane and tried to figure out where to ground it. The plane was built primarily of composites with virtually no exposed metal (except the engine, but it wasn’t convenient to the gas tanks).
J.
Yep. If there is the proper fuel air mixture you will get ignition. Either there isn’t the proper mixture or there isn’t enough charge on the car to cause that much spark. Liquid gasoline doesn’t burn.
I know that cars build up enough charge that the manned toll booths on highways had a set of brushes to discharge the cars so the guy in the booth didn’t get a shock when you gave him the money.
Yes. Yes it is.
I reduced my 4 year old daughter to hysterical laughter a few days ago by pointing to her nose and saying, “nozzle”, then her mouth, “muzzle”, nose, “nozzle”, mouth “muzzle”.
So the word nozzle is an inherently funny word.
Depends where you fly out of. Locally here, I pull the Cessna up to a pump island, swipe my credit card, and pump the gas myself. Just like a car (except that I need a ladder to get on top of the wing).
I suspect the reason may be that the fuel-to-weight ratio of an airplane to a car is vastly different, with the volume of gas pumped also being much higher. This would allow a much higher static potential to be accumulated during pumping, I would guess.
Why would any static charge build up with pumping? At that point, everything is electrically connected, since the pump nozzle and gas tank inlet should all be (locally) grounded.
The issue is when there’s a charge difference between the nozzle and the vehicle, and the nozzle is then inserted or removed and creates a spark.
I was told by a fuel handler that the fuel moving through the rubber hose itself builds up a static charge. Friction, after all. Military fuel trucks always ground themselves and the acft before doing anything else.
Hmm… My understanding about the fueler grounding themselves, would be so that they don’t transfer some newly generated charge when they grab the pump handle and pull it out of the tank, causing a spark. public safety sort of campaign that supports that explanation.
Charging by friction is a misnomer. Friction has nothing to do with it. The two materials need only make contact. Rubbing only exposes more surface.
Ah-hah. Here’s acar talk column supporting what I said above, about tires being conductive enough that a car is “grounded” to the road it sits on.