Grounding Fuel Cells

[bob darcey]

Our Tech people are starting to require that the metal filler necks of our fuel cells be grounded to the chassis. I'm not exactly a whiz with electrostatics, but that seems counter-intuitive to me, i.e., grounding the filler neck might actually increase the chance of a spark discharge at the filler neck (where there's lots of O2 available). I have read some of the procedures for aircraft fueling, and am curious what (if anything) the SCCA requires. Have there been fires caused by static discharge while fueling formula cars??

[DaveW]

I'm not an electrical whiz, but it seems to me that the only way grounding the filler neck would lessen the chances of a spark is if you also attached a ground strap to the (metal) filler can before you started filling.

[Dano]

I've got to agree with Dave... when the truck (big fuel can) would pull up to my (rented) Cessna the first thing they did was to clip the grounding wire from the truck to the exhaust pipe on the plane. This would insure that the truck and plane are same potential.

Dan

[Larry]

I know of nothing in the GCR that either requires or recommends anything like this. Have you asked Tech for their GCR reference?

Larry Oliver
International Racing Products

[Jonathan Hirst]

I still fill up my jerry cans at the the local Municipal airport and as stated above, the first step is dropping the end of the ground wire from the truck into the plastic can prior to filling.

Filler can to fuel cell would seem more critical than grounding the fuel cell to the frame.

[TimW]

Rubber rolling on tarmac is what generates static build up on vehicles, which is why rolling gas trucks and planes should be grounded prior to fueling. Filling a race car from a plastic scribner jug seems to have a very low likelihood creating a spark in fueling. Certainly lower than driving 6 hours on I80 and stopping for gas with metal nozzle at Texaco.

Indy car refuling rigs have a ground wire from the nozzle to earth in the pits, and the buckeye itself is the ground point on the car for dissapating any buildup.

[bob darcey]

Larry, this is a vintage club (RMVR) requirement, not an SCCA Tech deal; thanks for the info that there is no similar requirement in the GCR. I believe our Tech people are attempting to follow aircraft regulations, but, as cited above, the situation is very different. Are there examples of fires caused by static discharge (I don't know of any), or is this a non-problem??

[Rick Kirchner]

Plenty of problems lately, note the new warning stickers on gas pumps. For a while it was blamed on cell phiones, but more likely due to static from synthetic clothing and interior upholstery, and people getting in and out of the car while fueling. Also truck beds with liners, etc cna contribute if you are filling the jug or can while in the bed.

[Frank C]

With a quick search, one can find evidence of refueling fires caused by static electricity and some reasonable guidelines for preventing such fires. It doesn't look like these fires should be much of a problem for us. It appears that static electricity generated by sliding in and out of a car seat may be the main source.

For lots of links to scary headlines: ESD Journal
[I don't know about this organization's credibility, but don't show it to your tech inspector or anyone from Topeka!]

Guidelines from the Air Force Civil Engineer Support Agency: AFCESA
[Rick may have seen this - his advice matches up]

Guidelines from the American Petroleum Institute: API
[Another pretty credible group]

- Frank C

P.S. I don't see how grounding the fuel filler neck to the chassis is going to help at all without grounding the chassis.

[bob darcey]

Thanks for all the good replies. I did stumble into the NFPA (National Fire Protection Assoc.) 407 regulations for aircraft refueling. Prior to 2001, NFPA 407 required that the fuel rig, the aircraft and the filler nozzle and neck all be grounded. They have since revised that to say that all devices involved must be bonded, i.e., tied together electrically so as to have a common electrostatic potential; grounding to earth is (as far as I can tell) no longer required. Makes sense, but I still haven't seen where this is a problem with race cars.

[Greg Mercurio]

Beam me up Scotty. I would hope that this intellectual exercise will terminate in the conclusion that there is NOT a problem with fuel cells, nor regular fueling procedures from either fuel jugs or cans and that the silly Tech person in Colorado is suffering from hypoxia and therefore not fully oriented in all spheres. If this is a problem, send an email to Bill Pichardo and have him discuss this with the official in question. That's his "job".

Aircraft are grounded to the fuel truck or the pump stand to give a low potential path for stored static electricity. As a pilot who's fueled a plane innumerable times in 35 years, I can say I've NEVER seen a spark jump from the plane to the ground cable, not once, even when flying IFR for 5+ hours in really unstable air into Denver.

We have enough stuff to worry about, this ain't one of them. However, if you're really worried about blowing up your paddock space and your crew and your neighbors, touch the nozzle of the fuel jug to the gearbox before you stick it into the filler neck.

[Larry]

If we really want to get into the refueling of aircraft:
1. There is a grounding cable from the aircraft to a true grounding point (meaning a steel loop embedded in Mother Earth).
2. The fuel truck is grounded by the same kind of cable going again into Mother Earth.

I don't see any relationship between fueling an aircraft and a race car. I have never heard of an incident that caused a race car to catch fire as a result of lack of grounding during refueling. It sounds like we are fixing things that aren't broken.

If, however, it is a necessary fix, then we should ground the car and ground the fuel jug...but I don't see the need.

Larry Oliver
International Racing Products

[bob darcey]

"We have enough stuff to worry about, this ain't one of them."--gm

I agree. Thanks.

[Rick Kirchner]

I didn't mean to imply that the problems that the industry has been seeing at automotive pumps had anything to do with the safety of fueling our cars, or aircraft for that matter. Apples and oranges.

It's only related by the tendency for folks to to make the jump from cars in general to cars in particular, which is probably how the whole thing got started.

I'd think our cells are pretty well grounded anyway. Most sit on the metal floor pan, and are surrounded and in contact with the container shell. At least 50% of cells are the black rubber variety, who's conductivity ought to be pretty good. Don't know about the ATL/FuelSafe models.

Modern street cars have plastic tanks suspended by cushioned insulated straps, and linked to ground only thruogh the wire going to the filler neck and the sender. Have a problem with any of those connections and all sorts of bad things could happen. But that's not us.

If you've been carrying the gas cans around in a truck with a bedliner, it probably wouldn't hurt to set them on the ground for a second before proceeding.

[Bill Hetzel]

At ThunderHill, depending on who is running the pumps, you may be asked to put the jugs on the ground before you begin fueling.

Years and years ago, I remember that gas trucks had chains that hung down and touched the ground.

You could also buy rubber and steel mesh grounding straps at your local speed shop that bolted to the rearend and dragged on the ground. Now, we could attach one of these to our lower wishbones and ground the car but, SCCA would mandate that they be changed every year due to too much exposure to the sun.