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Old 06-20-2013, 04:48 PM
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Default grounding a plastic gasoline tank

I am installing a plastic gasoline tank in my boat. Im not sure how to ground it. Here are the specs:

Plastic tank.
It has a sending unit.
All fittings on the tank are metal.
Standard marine fuel fill hose.
Perko locking fuel fill (chrome plated zinc alloy? not sure if the filler is zinc alloy or this refers to the chrome, but it feels like plastic..): http://www.marinesupplydock.com/Perk...1399DP0CHR.htm

What and how should everything be grounded? I hope I dont have to ground the fuel pickup because I would have to remove and re-caulk a big hatch to access it.

Also Id like to mention I usually fill the boat with plastic jerry cans which I often keep on and slide around the deck of the boat.

Thanks for the help.
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Old 06-20-2013, 05:42 PM
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I've never seen a grounded fiberglass or poly tank...but fittings that are metal are supposed to be grounded..


Here's what the feds say..:

FEDERAL LAW
183.572 - Grounding
Each metallic component of the fuel fill system and fuel tank which is in contact with fuel must be statically grounded so that the resistance between the ground and each metallic component of the fuel fill system and fuel tank is less than 100 ohms.

Fuel flowing from the dispensing nozzle into a fuel tank is a potential source of a static electric charge which could cause a spark between the dispensing nozzle and metal component of the fuel tank fill system. To prevent such a spark from occurring, metallic components of the fuel tank fill system and metallic fuel tanks must be grounded.
Grounding or bonding may be accomplished by connecting the metallic components electrically by running a wire from one component to the next, and so forth to the boat’s ground. Grounding can usually be accomplished by a connection to the common bonding conductor or the engine negative terminal.
If the fuel tank deck fill fitting is nonmetallic, and nonconductive hose is used as a fill pipe, there is no need for grounding the fill fitting. Chrome-plated plastic fill fittings are treated the same as metallic fittings.
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Old 06-20-2013, 05:56 PM
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You can ground the tank by using a ring terminal on a wire. Install the ring terminal onto one of the five screws that mount the sender to the tank. Other end of the wire of course is routed to a ground source.
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Old 06-20-2013, 07:33 PM
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The sender base is going to be grounded to make the gauge work. I suppose you could run a pigtail up to the filler to bleed off static.
The tank itself? You ground that with weed eater string connected with a tywrap
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Old 06-21-2013, 12:47 AM
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Should I run a separate wire from the sending unit base to ground, or just pigtail the filler to the sending unit and call it good, because the sending unit is already grounded? Is grounding to the negative bus bar sufficient or should I run it separate all the way to the engine? Do you think I need to bother to run a wire to the fuel pickup and/or vent fittings?
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Old 06-21-2013, 05:51 AM
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Since you're using that metallic fuel fill, I believe you have to run a ground wire from the fill to the tank. If you don't have access to through bolt a wire to one of the fuel fill screws you can strip 3" or so of the grounding wire (#10 ga. would work fine) and put that inside the end of the fill hose as you're putting it on the fill.
Are you installing a new fuel fill, or is that what's already there? If it's already there you should have a grounding wire on it now. If you're installing a new one, along with the fill hose you need access to the fill fitting to double clamp it.
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Old 06-21-2013, 06:20 AM
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You can't ground plastic. Even if you ground a metal fitting, only that fitting is grounded, and everything else is ungrounded. As a result, if you have three metal fittings (fuel fill, fuel pickup, and vent) you would want a ground wire going to all three. That's why you aren't supposed to fill gas cans sitting in a pickup truck with a bedliner.
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Old 06-21-2013, 07:18 AM
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replace the fuel fill, if its zinc coated its junk anyhow. replace it with a plastic fill to eliminate any static discharge at the gas station
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Old 06-21-2013, 07:57 AM
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Quote:
Originally Posted by jobowker View Post
You can't ground plastic. Even if you ground a metal fitting, only that fitting is grounded, and everything else is ungrounded. As a result, if you have three metal fittings (fuel fill, fuel pickup, and vent) you would want a ground wire going to all three. That's why you aren't supposed to fill gas cans sitting in a pickup truck with a bedliner.
Doesn't removing a plastic tank from the bed of a truck and placing it on the ground "ground" it? That is, it dissipates static electricity. That is what I always thought.

If the tank is left in the bed of a truck and has any static electricity build up, then isn't there the possibility of the metal fuel hose nozzle acting as ground source, which can result in a spark when the grounding act occurs? A spark that is right in the fuel/air mix, which is the ratio is correct can result in ignition?
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Old 06-21-2013, 07:58 AM
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Quote:
Originally Posted by Raybo Marine NY View Post
replace the fuel fill, if its zinc coated its junk anyhow. replace it with a plastic fill to eliminate any static discharge at the gas station
I couldn't believe they're getting $41 for a freaking zinc fitting. It must be an expensive lock.
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Old 06-21-2013, 08:02 AM
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You cannot ground plastic
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Old 06-21-2013, 08:09 AM
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I think the more appropriate term is "bonding" and all metal components in the system must be "bonded", including the filler cap on the gunnel. The bonding should ultimately terminate at a common grounding point.

Putting the plastic on the ground (versus pickup bed) dissipates the surface charge (essentially grounding it as previously said) from static electricity which, unlike a metal container, can not simply be accomplished by briefly touching the fill nozzle to the container before opening and filling.
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Old 06-21-2013, 08:11 AM
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Quote:
Originally Posted by MIKE F View Post
I couldn't believe they're getting $41 for a freaking zinc fitting. It must be an expensive lock.
Wow, I just paid $54 for a very nice lockable stainless fititing for 1 1/2". Nice thing is you do not have to keep it locked.
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Old 06-21-2013, 09:03 AM
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Quote:
Originally Posted by MAXIMUM B View Post
You cannot ground plastic
Why not?

If it has a static electrical charge, and if that charge is dissipated by bonding/grounding the plastic to a ground source, what do you call this?

Are we talking the same language, that being the connection of a component to a ground source? Or, two or more components being connected together (bonding) and then one or more of the components being connected to a ground source?
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Old 06-21-2013, 12:35 PM
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Thanks for the replies. I needed a locking fill, and that's what my marine store had. The old fill was plastic and I wish I could have just gone with all plastic. can I bond all my metal fittings in series, just wire one after another and terminate it at the sending unit? Now I wish I hadnt caulked my hatch over the tank/fuel pickup fitting cause it is a real pain to remove it and grind off the caulking and recaulk it, and I just sealed it with 3m 4000 so it will be nice and stuck on. Will I blow up if I don't bond that fitting in?
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Old 06-21-2013, 01:34 PM
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This doesn't specifically reference marine poly fuel but it does describe the need for grounding plastic tanks during fueling/transfer of fuel:

http://www.fs.fed.us/t-d/pubs/pdfpubs/pdf95512323.pdf
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Old 06-21-2013, 02:15 PM
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Quote:
Originally Posted by jethro1 View Post
Why not?

If it has a static electrical charge, and if that charge is dissipated by bonding/grounding the plastic to a ground source, what do you call this?

Are we talking the same language, that being the connection of a component to a ground source? Or, two or more components being connected together (bonding) and then one or more of the components being connected to a ground source?
No. The plastic of the tank is not conductive. You cant ground something that does conduct electricity in the first place.

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Old 06-21-2013, 05:04 PM
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I am not talking about grounding a tank made of plastic which cannot conduct electricity. I am talking about grounding it so as to eliminate/dissipate any static electrical build up that it might have.

If this is not bonding or grounding, what would you call it?
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Old 06-22-2013, 12:47 PM
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Quote:
Originally Posted by jethro1 View Post
I am not talking about grounding a tank made of plastic which cannot conduct electricity. I am talking about grounding it so as to eliminate/dissipate any static electrical build up that it might have.

If this is not bonding or grounding, what would you call it?
Well, it's actually the same thing. Static electricity can build up on almost any surface for a variety of reasons, but if the item that has the static isn't conductive, attaching a wire won't do anything. The electricity - static or otherwise, can't "flow" off the item unless it has a conductive path.

The electronics industry has ways to deal with this, but it's nothing that's practical (or necessary) on a boat. As long as any metal that touches fuel is grounded, then touching a grounded hose nozzle to a grounded fill wont cause a spark since everything that matters is at the same potential.

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Old 06-22-2013, 01:01 PM
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Strange. A fabric covered wing that is sprayed with nitrate dope is not consider to be a conductor. However, the FAA recommends (see below) that the wing be grounded so as to prevent the build up of a static electrical charge, the discharge of which has been known to light up the fabric and burn the airplane to the ground. I don't see much difference between a non-conducting fabric being grounded n order to dissipate a static electrical build up versus a non-conducting plastic tank being ground in order to dissipate a static electrical build up. A spark emanating from a plastic tank in a combustible fuel/air mix has got to be at least as dangerous, and certainly more common, than a spark lighting up a fabric wing.

As mentioned in the beginning of this chapter, nitrate dope is very flammable. Proper ventilation and a rated fire extinguisher should be on hand when working with this and other covering process materials. Grounding of work to prevent static electricity build-up may be required.
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