About common agrrangement the gasoline fuel tank

Discussion in 'Boat Design' started by hookcap2017, Aug 29, 2017.

  1. Mr Efficiency
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    Mr Efficiency Senior Member

    :) OK, yes a valve that can be closed. I recall having a boat with two tanks merging into the one delivery line, seemed to drain fairly evenly, but one day did not, the engine stopped, and there were a few anxious moments before one valve was closed, and fuel started to be taken up. :rolleyes: One tank was empty, the other still full.
     
  2. hookcap2017
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    hookcap2017 Junior Member

    Oh, this standard define the portable fuel tank. My tank is fixed fuel tanks for boat.
     
    Last edited: Aug 30, 2017
  3. hookcap2017
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    hookcap2017 Junior Member

    Hi, man, have you the A14 and H24?
    I read the "construction standards for small vessels",7.3.1.5 A gasoline fuel tank shall have no openings in the bottom, sides, or ends.
     
    Last edited: Aug 30, 2017
  4. Barry
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    Barry Senior Member

    No, this reference is for fixed STAINLESS STEEL TANKS
    Your tanks because of their size are non compliant
     
  5. Barry
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    Barry Senior Member

    Construction Standards for Small Vessels is a Canadian set of standards, though when you compare them, are similar and in many cases exactly mirror the ABCY, USA standards but is not as complete or detailed
    The ABYC manual is probably 400 or more pages plus has supplements that were not printed in the manual (at least my 2008 copy)

    Often the Canadian standards refer to ABYC standards as a requirement for Canada as well
     
  6. Ike
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    Ike Senior Member

    My first question would be, why Stainless steel? It is far better to build in Aluminum or mild steel than stainless. Stainless is subject to crevice corrosion, especially at welds. That is why ABYC recommends that tanks be cylindrical. Only two welds and they are continuous welds. Plus a cylinder is open to the air on all surfaces. No places for moisture to be trapped.

    Canadian standards in TP1332 are virtually identical to ABYC. Sif you can take a look at Construction Standards for Small Vessels (2010) - TP 1332 E - Transport Canada http://www.tc.gc.ca/eng/marinesafety/tp-tp1332-menu-521.htm#wb11
     
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    Cylindrical tanks present problems of effective utilisation of available space, in some boats. Aluminium has enough corrosion problems of its own, too, especially with "foaming in" potentially leading to poultice corrosion. I've also seen then corrode from the inside, where a residue of sludge or god-knows-what lay on the bottom of a tank.
     
  8. Ike
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    Ike Senior Member

    Aluminum will not corrode if installed correctly, just as steel or stainless will not corrode if installed correctly. The most common problems with aluminum are mounting it onto a surface that collects moisture on the one hand, and letting fuel with ethanol in it sit for long periods. The ethanol causes phase separation, alcohol on the bottom and fuel on the top. At the boundary acids form that corrode the tank from the inside out, usually causing pin holes, sometimes bigger holes. Aluminum in it's normal state forms an aluminum oxide on the surface that is invisible to the naked eye, but is easily dissolve by persistent water or other liquids. If the metal doesn't dry out and reform the oxide, it corrodes. The same is true of other metals. Stainless steel in particular. The problem with stainless is the corrosion typically forms in microscopic crevices and is not detectable until it is too late.

    Yes, foaming in any metal tank is foolish as it simply provides a convenient place for moisture to collect between the foam and the tank surface. That is why it is not recommended. If a tank is foamed in, the requirements are that the adhesive bond between the tank and the foam is stronger than the shear strength of the foam. In theory the foam shears first rather than the adhesive bond. But in practice this is rarely achieved and the foam separates from the tank. Over time thermal cycling, shock, vibration and slamming cause the bond to break.

    In the boating world cylindrical stainless steel tanks are usually only seen on what are called "Hot Boats" or Performance Boats, very fast boats with big engines that are mounted in the open as well as the tanks. They are polished and really more for show than utility. Most production boats have aluminum or plastic (Polyethylene) tanks. Custom boats are sometimes built with steel tanks but rarely with stainless because of all the problems. Diesel boats sometimes have integral tanks built into the hull. Not a good practice but all too common. Even Hatteras builds them that way. Hole the tank and you have a real pollution problem.
     
  9. IronPrice
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    IronPrice Senior Member

    Don't do it. The only openings in your tanks should be on the top surface. Anything else is asking for trouble.

    You have a fuel pick up in each tank, if you have filler and breather for each tank you don't need to connect them.

    If you are concerned about weight distribution, use the valves to manage your draw from each tank.
     
  10. hookcap2017
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    hookcap2017 Junior Member

    Thank you very much for your reply.
    1st, All tanks have the filler, breathes and back-fire relief valve for vent air.
    2nd, Those tank is longitudinal arrangement, I hope what the after tank feed gasoline for the 4 outboards. Because the tank not same, one big(after), another small(forward).
    3rd, I only need liquid level indicator of one.

    This way, I connect the tanks of front surface(after tank) and after surface(forward tank).
     
  11. hookcap2017
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    hookcap2017 Junior Member

    Oh, the Pickup from the top side of tank.
     
  12. IronPrice
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    IronPrice Senior Member

    I understand why you want to do this. But (as people have said) you shouldn't do it because it is unsafe and possibly illegal.

    If you had diesel engines it would be easy to fit a transfer pump to move fuel between tanks. It's difficult to get transfer pumps for gasoline. If you can find one that would be a solution.

    The best solution I can think of (without a transfer pump) is: -
    - Have 4 picks (one per engine) in both tanks.
    - Use selection valves to control which tank you are drawing gas from.

    Its possible to get electrically controlled gas tank selection valves. They aren't cheap but you can control them from a remote switch at the helm.

    For monitoring you can use fuel flow sensors and a fuel computer. For example This. You input the volume of gas you pump into your tanks (treat them as one tank if you like) and the amount of fuel used (fuel flow sensors) is deducted from that, so you know what you have left. If you wanted to you could add fuel tank level sensors into the same system.
     

  13. fallguy
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    fallguy Senior Member

    Your reasons are not sound; sorry.

    You are doing this system so that you can get a single gauge reading?, but it will never be right unless your connections are on the bottom. Any corrosion or flaw in welds or connections would thus result in an absolute and complete draining of the tank.

    Big mistake that could result in loss of life.
     
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