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Thread: How to ground a diesel tanks

  1. #1
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    I've ordered to an inox producer, the suitable inox 316 diesel tank for my 10 metre sailing boat under construction. I've readed that the tank must be electrically grounded. My boad is made of wood (streep planking) externally sheated with two layers of fiber glass and epoxy resin. What I've to do to ground the inox tank ?

    Many thanks in advance for your suggestion

    Daniele

  2. #2
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    I'll... (snip) ...knows?

    [edited to remove ignorance]

    [ 11-10-2003, 10:35 AM: Message edited by: NormMessinger ]

  3. #3
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    Nigel Calder, in both Marine Diesel Engines and Boatowner's Mechanical and Electrical Manual, shows a diagram of a "proper" diesel fuel tank installation. The diagram shows a grounded fuel fill, running from the fill neck just below the deck, to ground.

  4. #4
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    The tanks on Patience are 316L stainless 2mm thick. 810 litres of diesel. For fifteen years no bonding, no grounding, no problem.
    My suggestion would be not to bother.

    IanW

    [ 11-10-2003, 10:33 AM: Message edited by: Ian Wright ]

  5. #5
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    It's a cultural thing. US sailors like to ground and bond everything, UK sailors not. I vote not.

    IanW

  6. #6
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    Isn't Calder British? Can diesel be ignited in normal atmospheric pressure by a refueling type static spark. My preconcieved misconception is that it will not.

  7. #7
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    I don't think a static spark could be hot enough to light diesel, but I'm not certain. I do know that Loon's tanks are not grounded.

  8. #8
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    "Isn't Calder British?"

    Yes, but he lives in the 'States and publishes mainly for the American Market.

    "Can diesel be ignited in normal atmospheric pressure by a refueling type static spark."

    No, it can't, not unless you boil it first.

    Norm, you must be the first poster ever to admit to a limit to your erudition, could you be stating a trend?

    IanW

  9. #9
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    I'm 99.9% sure that Ian, Norm, and Donn are correct. Grounding a gasoline filler-neck is a VERY good idea, but it takes more than even the strongest static charge to ignite diesel.

    We don't hear of it much, but probably a dozen times a year a gasoline explosion is started around cars or boats by a pilgrim wearing dry woolen clothing; a touch in the wrong place at the wrong time. Rather volatile stuff that 'motion lotion'. There've been seemingly reputable reports of a cell phone, ringing at just the wrong time, setting off gasoline fumes.

    That current regs. call for grounding a diesel tank is an affect, and has nothing to do with safety, unless you assume, as the regulators and insurors probably do, that the boat might be converted to gasoline someday.

    It might, however, before you discard such grounding, be a good idea to check with a likely insurance company. Running a wire to a ground is very simple, and will be easier now than later; proper gauge wire, filler neck or tank mounting to engine block. Check the regs and just do it. It will take a half a day, beginning to end, even if it is foolish. Then, when the insurance company asks if the tanks are grounded you can say, "Yes", and not have to worry about it.

    Insurance companies are getting jumpier and jumpier these days.

    [ 11-10-2003, 02:46 PM: Message edited by: Jack Heinlen ]

  10. #10
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    G'day all,
    IMHO the only real way to ground an object in an insulated vessel is to go through the hull to a conducting material, usually a copper strip fixed on the outside of the hull.
    Check out many Amateur Radio books under grounding, ARRL antenna handbook has a topic on boat radio installations and grounding systems.
    Regards, Mark aka "Banjo"
    http://banjosbackyard.blogspot.com

  11. #11
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    I don't do engines or electric work on boats but ...

    If a boat is under 20' (with some exceptions), the Coast Guard requires grounding of all metal.

    I believe the grounding is to prevent damage to you in case of an electrical problem not to prevent a fuel explosion.

    I believe that the engine block is not the proper place. I blieeve the alternator/generator is.

    My book is outside or I would look up the matter.

  12. #12
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    If a boat is under 20' (with some exceptions), the Coast Guard requires grounding of all metal.
    I didn't know that. I've had lots of boats under 20', and none were grounded in any way. Passed all sorts of CG inspections, too.

  13. #13
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    Okay, we've two opinions on the original poster's question: a copper strip to the outside of the hull, or to the alternator.

    Donn, you've got Calder, what does he say? I don't know, and it seems the original poster needs to know.

    My rec. would be finding out what the EU regulations say, and I'm sure they say. If you do what the regulators say, how can you go wrong?

  14. #14
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    "Norm, you must be the first poster ever to admit to a limit to your erudition, could you be stating a trend?"

    Weeeelll.... It may not really believe that, it may just be a defensive mechinism. [img]tongue.gif[/img]

  15. #15
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    Donn, you've got Calder, what does he say? I don't know, and it seems the original poster needs to know.
    Calder, and everyone else I've read says a ground plate on the outside of the hull. Same for lightning redirection.

  16. #16
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    One method I liked, back in the fish boat days, was to take a length of copper tubing, beat it flat, and run it the length of the inside of the boat. On mine, it was right on top of the keel. Then everything metal of any size at all got electrically connected to that, including the stem knee thru bolts and some bolts in the way of the transom framing, and everything in between, including: metal cases of radios et al, stove, sink/plumbing, engine block, and ALL thru hull fittings. You get the idea. Bulkheads were drilled thru, down low but out of the bilge, with a bronze bolt connecting the tubing. This whole shootin' match was connected to zincs on the outside of the hull (on the shaft, bearing, and rudder post). The (diesel) fuel tank filler lines (which were bronze) were connected from just under the deck down to the copper strap. The connection jumpers were of various gauges of stranded copper wire, depending, frankly, on what I had around at the time, but always seeming extra big. Connections were all bolted, with bronze or brass bolts. Think lightning protection as well as corrosion prevention. Also, you will be surprised how much better your depth flasher and radios work.
    This whole bonding system should be independent of the electrical system, except for the ONE point that the system ground is connected to the bonding system, which should be with as big a conductor as anything in the electrical system. The bonding system is not the electrical system's return path.

    Sorry to jump in, and I don't mean to lecture, but I think this is a matter of paramount safety concern as well as good maintenance.

    (Edited to add And by the way, tell us about your 10 meter under constuction.. Congratulations! Where is the work being done?

    [ 11-10-2003, 10:06 PM: Message edited by: ChuckG ]

  17. #17
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    Chuck...Calder suggests that a long narrow ground plate provides the most effective lightning dispersal, but he places it on the outside of the hull. He explains why, but it is beyond my comprehension.

    [ 11-10-2003, 10:11 PM: Message edited by: Donn ]

  18. #18
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    Stepping slightly sideways,,,,,, Patience has a ground plate, a sintered bronze block on the underwater part of the hull, but I use it for a ground plane for the VHF, GPS ect, and potential SSB set, not as an anti static device.

    IanW

  19. #19
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    It's me again! [img]smile.gif[/img]

    A large body of water is the best ground one can get and salt water is even better.

    Any electrical system including engines should have good grounding, to do this one should have a copper strap going through the hull to the under water copper plate or strip.

    As stated before, this then becomes your main ground connection that goes to the ground rail in your electrical distribution board. The rest of the system then uses this rail in the board as the common ground connection point.

    As for radio systems, good grounding is imperative for not only safe operation but reduces static, provides some protection to operator and equipment from lightening stikes, improves range, and provides some ground plane to antennas that need it. Note some VHF antennas are designed in such a way that they dont need a ground plane, ultimately a good grounding to earth for the radio is still optimal for the reasons stated above.

    FOLLA?
    Regards, Mark aka "Banjo"
    http://banjosbackyard.blogspot.com

  20. #20
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    We're getting into two different topics here, grounding a stainless tank and bonding all the metal parts. When researching fuel tank construction two years ago, I came to the conclusion that stainess was NOT a good material for diesel fuel tanks as they may have a tendency to pinhole due to the action crevice corrosion. Since stainless is stainless because of the oxide layer that forms on it's surface, when oxygen is excluded by the coating of oil, any moisture contamination will tend to start pinhole corrosion. Lloyds specified stainless tankage in the 60's (dates hazy), only to find that failures made them rescind this specification in later years. I'd be concerned that grounding a stainless tank would lead to even more possibility of problems. Regular steel is more protected by the oil inside and if well painted outside, should last for a long time.

    The other question of bonding has been thrashed quite soundly on this forum with the general opinion being that when a chunk of metal such as a through hull is fitted through a wooden hull it is electrically insulated until wired to another piece of metal, at which point a circuit becomes possible and thus the possibility of stray current corrosion arises. It's your choice but I cut all the bonding wires that Victoria came with.

    Good luck,
    Jamie

  21. #21
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    First of all let me thanks you all for the very deep argumentation and suggestion.
    I leave near to Florence in Italy, and the 10 metres sail boat under construction is a lovely English project. I started on 1998 and I will put into the water on 2005 God allowing.

  22. #22
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    Dan, All these answers boggle me? Diesel installations are connected with metal piping/tubing, therefore electrically connected read bonded if you like, to the engine via supply and or supply and return. Assuming this is electrically a D C setup, the engine (block) is the major component on the ground side. This is not to be confused with a bonding system for radio ground plane, electrolysis prevention, lightning prevention or fuel fill to tank piping that is not metal with no insulated breaks such as hose etc. to prevent static sparks (irespective how small) from igniting fuel vapors at the fill pipe. The reason that diesel is safer than gasoline, its high flash point, something over 120F?, this won't happen. I think the and USCG and insurance surveyors require gasoline fill plates be bonded to their respective tanks, and that any piping in engine compart carrying gas, diesel, or lube be of matal. Don't know about hydraulic oil? Could you possibly get this bonding requirement clarified?

    Anyway, good luck and try not to get confused, cbob
    Help!

  23. #23
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    Hi,
    i think the main concern here is if you are likely to have ELECTRIC MICE on your boat!!
    don
    [URL=http://invertedvboats.bravepages.com/]<br />[URL=http://invertedvboats.20m.com/]

  24. #24
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    The grounding I'm used to seeing for fuel tank fills has been simply a short jumper wire from the metal fill pipe right under the deck to the metal fill pipe going into the top of the tank (jumping past the flexable connecting hose). As has been pointed out, this serves only to disapate any static charge in the fuel filling hose (can be significant). This is important for a gasoline system & I think I'd still go with it on a diesel system if up to me. (I believe the static build up comes from the fuel flowing through the hose & not much to do with the wordrobe of the pump jockey ).

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