Adequate Refueling Ground?

[FlyingMonkey]

At the rear of my hangar is a tailwheel tie-down that consists of a steel plate bolted to the concrete floor with (I think) four stout bolts. If I attach a wire from the airplane's exhaust to that tie down, will that provide adequate grounding for static discharge while refueling (using gas cans) in the hangar? or would I be better off running the wire to one of the building's structural steel I-beams?

 

Thanks!

[Roger Lee]

That won't be a very good ground. You really need something that goes into the earth. Many metal hangars have grounding rods so maybe the hangar would be better if its metal.

[paul m]

If everything used in the refueling process (like Tuff Juggs) is non-metal, do you still need to ground?

[Ed Cesnalis]

It is bonding that is important, grounding isn't very common anymore. Bonding is from truck to plane ( you can't do this with a plastic container ) and grounding is from truck to ground. ( can't do that either ) Sounds like you intend to ground your plane?

 

Flying is one source of static and gas moving through a hose or nozzle is another.

 

AOPA advises: Should you find yourself needing to fuel from containers, always use metal cans, because they can be grounded. Never use a plastic container to fuel an aircraft.

 

http://flighttrainin.../refueling.html

[Jim]

AOPA advises: Should you find yourself needing to fuel from containers, always use metal cans, because they can be grounded. Never use a plastic container to fuel an aircraft.

 

http://flighttrainin.../refueling.html

 

Why would using plastic fuel containers on an airplane be any different than using them on a motorcycle or ATV?

 

I think the grounding procedures for aircraft are largely applicable to fuel pit and fuel truck operations where static buildup could be a significant problem. I've always used plastic fuel containers, just being careful to make sure I touch both the aircraft and the container before I pour the fuel.

[paul m]

Thanks for the article Ed. Just trying to understand the physics better, so a few questions:

 

1) Why don't I ground my car when I fill up at gas station?

2) If I am filling cans at the gas station should I ground them? Does it matter if they are plastic or metal?

3) If my plane is composite how does grounding the exhaust pipe matter? There is no direct conductivity to the fuel opening in the wing (as there would be in a metal plane), is there?

[Ed Cesnalis]

1) you would want to bond your car to the fuel pump and ground the pump. The car doesn't fly and build up big charges like an aircraft.

2) plastic doesn't conduct so you can't ground them.

3) carbon fiber conducts

[Ed Cesnalis]

Why would using plastic fuel containers on an airplane be any different than using them on a motorcycle or ATV?

... I've always used plastic fuel containers, just being careful to make sure I touch both the aircraft and the container before I pour the fuel.

 

The motorcycle or ATV do not build up static charges from flying through clouds as often as aircraft.

 

To be safe you would want to be protected as you pour the fuel when the static charge is being created.

[Jim]

The motorcycle or ATV do not build up static charges from flying through clouds as often as aircraft.

 

To be safe you would want to be protected as you pour the fuel when the static charge is being created.

 

My airplane is sitting in the hanger when I refuel it. Plenty of time to bleed off the static charge from flying through the clouds.

[paul m]

Thanks Ed. Echoing Jim's point, if my plan is to refuel before flying for the first time that day as opposed to after a flight is the risk greatly diminished? And one last question, If I am going to ground the plane, why does it matter if I use plastic or metal cans. I ground one side or other (either the plane or the dispenser), but not both or is that not right?

[Ed Cesnalis]

I have no real idea if our light sports build much of a charge when flying. If I have to stop for fuel I do bond to my exhaust.

 

When I fuel I ground my fuel trailer to the hangar and bond my CT to the fuel trailer and this mimics what is done at the airports.

 

Grounding your plane to the hangar will give stray electrical current somewhere to go but if a spark results from pouring the gas you would be at risk.

 

I'm an insulation contractor and when we take a hose into an attic and pump fiberglass insulation through the hose static charges can build fast and the results are sparks arc-ing from your flesh to the gang nails that fasten the trusses. It can be quite painful and looks like a little lightening display in a dark attic.

 

If I used plastic containers I would have my forearms on the wing hoping that it would create a bond.

 

Conclusion:

 

Grounding your aircraft to the hangar is not the same thing as bonding a fuel station (that is grounded) to your exhaust.

[sandpiper]

Jim - I would not be refueling while the plane is in the hangar. Too much risk IMHO.

 

I knew a guy who was de-fueling a restored show quality plane in his hangar. When it was all over three planes and the hangar were gone.

 

Probably not likely to happen but for the little effort to move my plane out of the hangar I'm not gonna risk it.

[FlyingMonkey]

Hmm...so far I have heard don't use plastic cans, plastic cans are fine, ground/bond the airplane, don't bother. I would have thought there would be a consensus on fueling these things!

 

You *do* ground when you fill up your car. ever get a shock when you touch your car getting out? that's a static buildup from rolling down the road discharging. If you somehow manage to get out of your car and not touch metal, when you grab the metal nozzle the static discharges. When you put the nozzle in your tank, the metal nozzle contacts the inner metal fuel filler neck, grounding (or bonding, not sure I know the real difference) the whole thing during the fueling process.

 

Ever hear not to get back in your car while fueling? That's because you can build up static rubbing against the carpet, seats, etc while ungrounded, then discharge when going back to the nozzle which can ignite fuel vapors. There are plenty of internet videos of this happening.

 

As for grounding gas cans, you should always discharge static from them. Always fuel them by placing them on the ground, not in a trunk, truck bed, or on a tailgate. Otherwise you can risk a static discharge while touching or fueling them, which could be...bad.

[FlyingMonkey]

Jim - I would not be refueling while the plane is in the hangar. Too much risk IMHO.

 

I knew a guy who was de-fueling a restored show quality plane in his hangar. When it was all over three planes and the hangar were gone.

 

Probably not likely to happen but for the little effort to move my plane out of the hangar I'm not gonna risk it.

 

Okay, once you are out of the hangar, how do you deal with the static hazard? I think any place you fuel is relatively safe if you take the proper precautions...I'm still trying to figure out what those precautions should be.

[Roger Lee]

Hi Andy,

 

Kind of like power verses no power on landings isn't it.

 

People fuel in every way possible that's just the way the world is. Are there some hazards, yes, but how viable or how much of a real potential for something to happen? Who can really say because the circumstances and factors all have to come together just right. Can't be too bad or we would see many hundreds of aircraft fueling fires per year.

Sounds like after everyone weighs in there will be a choice for you to make.

[Ed Cesnalis]

A typical nylon shell jacket can build up a charge just by walking around and that charge will have to go somewhere.

 

If you are going to fuel with cans, use metal and make a wire with 3 alligator clamps on it, one clips to the fuel can, one to the airplane exhaust pipe, and one to ground.

 

The vapor pressure and flash point of gasoline just doesn't mix well with the static charges that build up with gasoline flowing through plastic.

[Ed Cesnalis]

The fuel truck used to bond to your aircraft and ground the fuel truck to the ground cable. Now they just bond. I think some of our members simply ground their aircraft to the hangar. This is forgoing the more important bonding.

 

As you fill your wing tank you are creating a static charge on the surface of the fuel, since our airframes conduct then I assume our tanks are bonded and that this charge can likely be conducted to ground.

• Remove small containers from vehicles before dispensing fuel.
  
• Ground and/or bond all containers before opening and dispensing fuel.
  
• Physically touch the outside of containers, grounds, and bond wires to bleed excess charges off your body.
  
• Touch the outside of metal and plastic containers with the fill nozzle before opening
  and dispensing fuel.
  
• Do not use old or rusty containers or worn bonding and grounding clamps or worn and frayed wires.
  
• When handling fuels, avoid synthetic fabrics. Wear cotton clothing and coveralls to
  minimize static build-up.
  
• Avoid the use of velcro on or around fuel dispensing and handling equipment.
  
• Do not use chamois to filter flammable fuels.
  
• Do not use radio transmission equipment or cell phones around refueling
  

[Doug G.]

The cell phone thing has been shown to be a myth. (By the Mythbusters, among others, and the warnings have disappeared from most commercial gas pumps.

[Ed Cesnalis]

The process of bonding and grounding can be defined as providing an electrically conductive pathway between a dispensing container, a receiving container and an earth ground.

 

This pathway eliminates the buildup of static electricity and allows it to safely dissipate into the ground. The Code of Federal Regulations, 29 CFR 1910.106(e)(6)(ii) states, "Category 1 or 2 flammable liquids, or Category 3 flammable liquids with a flashpoint below 100°F (37.8°C), shall not be run/dispensed into containers unless the nozzle and container are electrically interconnected. The National Fire Protection Association (NFPA), NFPA Code 30, 2008 edition, Chapter 18, Section 18.4.2.2 states that all liquids above their flash point must have static control that complies with Chapter 6 Section 6.5.4. Where the metallic floorplate on which the container stands while filling is electrically connected to the stem or where the fill stem is bonded to the container during filling operations by means of a bond wire, the provisions of this section shall be deemed to have been complied with." This means that all containers of Category 1, 2 or 3 liquids (liquids with a flash point lower than 100°F) need to be bonded and grounded during dispensing. This includes non-metallic containers, even though the construction material may not be recognized as conductive (for example, polyethylene). If the containers are not properly bonded and grounded, the resulting static spark could be capable of raising the vapor temperature above the flash point, causing an explosion.

 

The diagram below is an example of a complete bonding and grounding system. The bonding wire is shown connecting the lids of the receiving container and the dispensing container. The grounding wire is shown connecting the dispensing container to the common ground within the facility. The common ground is in turn connected to an earth ground. (Any ground source that is adequate for power circuits or lightning protection is sufficient for protection against static electricity.) This system provides an electrically conductive pathway for static electricity to follow and safely dissipate into the ground.

 

 

Sources

29 CFR 1910.106

National Fire Protection Association, NFPA 77, Recommended Practice of Static Electricity

Uniform Fire Code, UFC Div. VIII Sec. 79.803

(Rev. 2/2013)

[Ed Cesnalis]

Even if you bond aircraft to gas can and ground as well you may have a funnel employed that could supply the source of static ( gas thru the funnel ) and if not bonded could discharge.

[sandpiper]

Hey Ed - In Alaska we often filled from metal cans in the bush. The fuel went into the plane via a funnel with a chamois filter. Worked great so long as you knew what side of the chamois to put downstream and the chamois wasn't dry. So, why do you say not to use a chamois? Kept the water and other contaminants out.

[Doug G.]

Do how does this supply to filling a container at a gas station? No bonding goes on there. (I assume that the nozzle is grounded to the pump and the pump is grounded to a physical ground.)

[Ed Cesnalis]

John,

 

That comes from this USFS doc. http://www.fs.fed.us/t-d/pubs/pdfpubs/pdf95512323.pdf

 

The doc doesn't say why, but the reason is that the passage of fuel thru the chamois increases the static charge and danger of spark.

[Ed Cesnalis]

Do how does this supply to filling a container at a gas station? No bonding goes on there. (I assume that the nozzle is grounded to the pump and the pump is grounded to a physical ground.)

 

The nozzles are wired and contact with your gas fill creates a bond.

[sandpiper]

Ed - Well AK would have had plenty of static electricity especially in the winter and more so in the interior. Didn't hear too much about anyone blowing up but there was more than one caught his plane on fire trying to warm the engine with a firepot. I guess it was the lesser of the evils. This was done from the early days of aviation up thru the '80's at least. Probably still happening but I know I stopped when I got one of those new funnels that keeps contaminants including water out of the tank.