Identifying a wire on my diesel tank

[boatpoker]

Originally Posted by BAD ORCA

Should a fuel tank also be grounded to the engine block?

Yes, both diesel and gas should be grounded from the fuel fill to tank to engine.

[boatpoker]

Originally Posted by a64pilot

Often pretty much everything metal is bonded together with the ideal of it all being protected by an anode that way.
Other school of thought is to isolate all the metal bits so that stray current can’t get them all. Both schools seem to work.
Then there is the idea of bonding all metal bits as a part of a lighting protection scheme, who knows if that’s effective or not.

I’d buy the bonding to prevent static discharge, except the way to do that is to bond the fuel filler to the vehicle being fueled, and I’ve never seen that on boats, or ground vehicles, only aircraft for some reason?

Real answer is to see where it goes, likely to the engine block eventually, but may go to other metal bits on the way. Often bonding is a series connection as opposed to each metal bit having its own bonding wire.

Nothing to do with corrosion (you're confusing galvanic and stray current corrosion). It's all about electrical safety/static discharge/fire hazard and is an ABYC Standard (it should be black or green with a yellow stripe)

From ABYC H-33, Diesel Fuel Systems

[Nicholson58]

Originally Posted by Dsanduril

Looks like it is strapped to the fill hose. My bet, if you trace it to the other end it is connected to the metal deck fill plate to allow static discharge from the nozzle when filling. Since the hose is non-conductive someone put in a conductor to connect the fill plate to the tank electrically.

This is a high probability. Normally the rubber hose isolates the tank. Grounding the deck port lessens the chance of a static spark at the fuel dock. Diesel is not a problem but there is gasoline present.

[boatpoker]

Originally Posted by Nicholson58

This is a high probability. Normally the rubber hose isolates the tank. Grounding the deck port lessens the chance of a static spark at the fuel dock. Diesel is not a problem but there is gasoline present.

Here in Ontario one is not allowed to fuel ones own boat. That responsibility lies with the fuel dock hand (often a summer help kid). I know of two cases this year where diesel tanks were filled with gasoline. Two is a low count, most years it's four or five.

[Dsanduril]

Originally Posted by boatpoker

You are correct except that the most fuel fill hoses are wire re-inforced therefore conductive.

Only if the wire is connected to the metal appurtenance at either end of the hose. In a properly constructed commercial assembly with swaged end fittings the wire is exposed at the ends before the swage is applied and thus the entire hose assembly becomes conductive.

In all of the boat assembly pictures so far in this thread the hose end is applied directly to a nipple/barb (no swaged hose termination) and thus the hose material acts as electrical insulation/isolation between the tank/fill port and the metallic reinforcing in the hose. There are two ways around this; an external wire as posted by the OP or exposing the reinforcing at each end and connecting it by some means to the rest of the metal components.

[boatpoker]

Originally Posted by Dsanduril

Only if the wire is connected to the metal appurtenance at either end of the hose. In a properly constructed commercial assembly with swaged end fittings the wire is exposed at the ends before the swage is applied and thus the entire hose assembly becomes conductive.

In all of the boat assembly pictures so far in this thread the hose end is applied directly to a nipple/barb (no swaged hose termination) and thus the hose material acts as electrical insulation/isolation between the tank/fill port and the metallic reinforcing in the hose. There are two ways around this; an external wire as posted by the OP or exposing the reinforcing at each end and connecting it by some means to the rest of the metal components.

Sorry using the wire from the hose and a grounding conductor is also contrary to ABYC.

The external and separate grounding conductor is the only way to meet the standard. Clamping the external grounding conductor under the hose clamp is another common fault that is contrary to the standard.

[StoneCrab]

A flowing hydrocarbon like diesel or gas generates a static charge. It would be proper to ground the deck plate to the tank. The marina fuel hose should also be grounded for this reason.

Airports and home heating trucks often have a separate grounding wire with a clip which is attached to the plane, so the ground is obvious and intentional.

Whether the tank should be grounded to the boat's house ground is subject to debate. It would literally be a floating ground if you are not on shore power.

Due to the low vapor pressure of Diesel, it is safer than gas when the tanks are being filled. The drain wire gives the electrons somewhere to go, instead of building up a high voltage charge, which eventually generates a potentially lethal spark.