About common agrrangement the gasoline fuel tank

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

  1. hookcap2017
    Joined: Jul 2017
    Posts: 14
    Likes: 0, Points: 1
    Location: CA,US

    hookcap2017 Junior Member

    I have a question, I split the one gasoline fuel tank into two gasoline fuel tank, because the bulkhead of the structure.
    So, if I use that the pipe connect the two gasoline fuel tank? this plan could do?
    upload_2017-8-29_17-39-32.png [​IMG]
     
  2. SamSam
    Joined: Feb 2005
    Posts: 3,566
    Likes: 111, Points: 63, Legacy Rep: 971
    Location: Coastal Georgia

    SamSam Senior Member

    Is that a side view or a top view?
    Do they have two separate fill inlets?
    How many outlets?
    How big are the tanks?
    What size is the 'connect piping' ?
    Is the connect piping flexible hose?
     
  3. Barry
    Joined: Mar 2002
    Posts: 821
    Likes: 31, Points: 28, Legacy Rep: 158

    Barry Senior Member

    No, unfortunately not as per ABYC
    For GASOLINE, you cannot joint the bottoms of any fuel tanks.

    You need to install two draw tubes, each fitted with antisphon valves then a valve to select between each of these tanks ( see below for an alternative **)

    Does your boat have return lines? And what is the material of the tanks, aluminum or steel?

    Re your drawing, you would not need 3 connect lines in any case

    **If you installed two draw tubes and two antisiphon valves you could "Y" the two antisiphon lines and draw from both tanks simutaneously but this can create a problem in the future. If the lines are common and offer the same pressure losses/resistance, the fuel pump will pull an equal amount off each tank so that the level remains the same BUT, if you have a restriction in the antisiphon valve, ie accumulation of dirt, more fuel will be pulled from the fuel line of least resistance and depending on the location of the shut off valve etc, may never equalize. So when one tank, the one that has the least fuel line resistance gets low enough to draw air, you will never get the fuel out of the other tank.

    My previous question about the engine having a return fuel line is of extreme importance, you need to check this out
     
  4. gonzo
    Joined: Aug 2002
    Posts: 12,345
    Likes: 197, Points: 63, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    The pickups have to be from the top,not any of the sides. A three way valve would be a good choice in case one tank empties before the other on gets contaminated.
     
  5. hookcap2017
    Joined: Jul 2017
    Posts: 14
    Likes: 0, Points: 1
    Location: CA,US

    hookcap2017 Junior Member

    No, the pipe is stainless steel.
     
  6. Barry
    Joined: Mar 2002
    Posts: 821
    Likes: 31, Points: 28, Legacy Rep: 158

    Barry Senior Member

    So then the connecting pipes are stainless welded to a stainless tank?
     
  7. Barry
    Joined: Mar 2002
    Posts: 821
    Likes: 31, Points: 28, Legacy Rep: 158

    Barry Senior Member

    An interesting standard about stainless tanks in the ABYC manual, H.24.18.2.2 Stainless steel gasoline tanks shall be cylindrical, with domed heads, and a capacity of less than 20 gallons, 75 litres
     
    hookcap2017 likes this.
  8. hookcap2017
    Joined: Jul 2017
    Posts: 14
    Likes: 0, Points: 1
    Location: CA,US

    hookcap2017 Junior Member

    No, this engine is outboard.
    Stainless steel
     
  9. hookcap2017
    Joined: Jul 2017
    Posts: 14
    Likes: 0, Points: 1
    Location: CA,US

    hookcap2017 Junior Member

    No, I use the flanges or the coupling.
     
  10. Barry
    Joined: Mar 2002
    Posts: 821
    Likes: 31, Points: 28, Legacy Rep: 158

    Barry Senior Member

    So the joint will then be solid as it is unlikely that the coupling would be able to move a bit. Therefore when the tanks are moving slightly but independent of each other, you will have some strain, flex, within the materials elastic range.
    Stainless, the effects dependent on what series that the tanks are made out of, can work harden, become brittle and crack at loads well below their ultimate strength. The openings that you have for these flanges, couplings would not meet the ABYC
    guidelines. The reason being is that the are not as safe as they should be. Any holes that are in a gasoline tank, (ie a drain hole for cleaning) must be terminated by a tapered pipe plug.

    Another footnote in the manual is that even if the tanks are stainless and below 20 gallons (75 litres) the only allowable alloys are 316L or 317L
    The L is for low carbon and when welded offers more corrosion resistance at the weldment than non "L" designation
     
  11. hookcap2017
    Joined: Jul 2017
    Posts: 14
    Likes: 0, Points: 1
    Location: CA,US

    hookcap2017 Junior Member

    I already design the fuel supply line(P3), those piping feed the Outboards, the Outboards not need return oil. The V1 is quickly close valve.
    That is to say, those tanks feed the Outboard that respective, but, if I use that three pipes connect the two gasoline fuel tank? this plan could do?

    upload_2017-8-30_8-11-27.png
     
  12. hookcap2017
    Joined: Jul 2017
    Posts: 14
    Likes: 0, Points: 1
    Location: CA,US

    hookcap2017 Junior Member

    Oh, those tanks will fill PU of round.
     
  13. Barry
    Joined: Mar 2002
    Posts: 821
    Likes: 31, Points: 28, Legacy Rep: 158

    Barry Senior Member

    You are using two deck fills and you illustrate two fuel lines going to the outboard. What is the reason to have non compliant and unsafe connecting pipes between the tanks. (the deck fills and tanks must be grounded by the way)
    So your question "Will this plan do" No. Not if you want to be compliant. If at any time you have the boat surveyed by a qualified surveyor, say for insurance purposes or financing purposes (by either you or a future buyer) he should notice that the tank material with the size of the tanks that you have do not meet standards and your connecting pipes do not meet standards.

    I do not understand your comment in your subsequent post "oh, those tanks will fill PU of round"
     
  14. Mr Efficiency
    Joined: Oct 2010
    Posts: 6,206
    Likes: 127, Points: 63, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    Two separate pick-ups with a Y junction into a single delivery line may indeed drain unevenly, but if it happens, a ball valve on both lines before the "Y" junction will prevent the scenario of not being able to draw fuel from the tank that isn't empty.
     

  15. Barry
    Joined: Mar 2002
    Posts: 821
    Likes: 31, Points: 28, Legacy Rep: 158

    Barry Senior Member

    you mean an on off valve on both lines before the Y, that was the first recommendation
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.