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aluminum fuel tank - best welding practice

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  • Ltbadd
    replied
    Originally posted by CODE4 View Post
    The two tanks are completed. 3/8 NPT couplers welded in, clean out ports, filler necks, and draw tubes.

    The owner did the cutting himself with a circular saw, carbide tipped blade, and piece of flat bar as a fence. He did an alright job, I did what I could with the fit up - from what you can see some of the joints were not ideal, but pressure testing both came out fine. Both tanks have two baffles each.
    Nice job, well done

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  • CODE4
    replied
    A few more photos.

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  • CODE4
    replied
    The two tanks are completed. 3/8 NPT couplers welded in, clean out ports, filler necks, and draw tubes.

    The owner did the cutting himself with a circular saw, carbide tipped blade, and piece of flat bar as a fence. He did an alright job, I did what I could with the fit up - from what you can see some of the joints were not ideal, but pressure testing both came out fine. Both tanks have two baffles each.

    Click image for larger version

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  • H80N
    replied
    Originally posted by WillieB View Post
    ...I'd be surprised if 90 gallon tanks would be a big problem. I'd still keep the holes in baffles small, maybe only at the bottom. Two per tank wouldn't be a bad thing.
    For what it's worth... my 41ft Morgan displaced around 27K pounds... would expect this 45 footer to be in the same neighborhood.... tanks are typically mounted way below the water line ....
    Sooooo.... a 650lb tank would probably not make much difference against that mass... I would baffle it well though...

    27K divided by 643 = 41.99 or 2.381% of the total displacement... Not a Lot...
    Last edited by H80N; 03-27-2015, 08:56 AM.

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  • WillieB
    replied
    The father of an OLD girlfriend spent his life with milk trucks. He would always volunteer for the 350 mile middle of the night round trips to avoid daytime local farm pick ups. A full or empty truck doesn't slosh. He described the air ride suspensions as REALLY unstable. I'd be surprised if 90 gallon tanks would be a big problem. I'd still keep the holes in baffles small, maybe only at the bottom. Two per tank wouldn't be a bad thing.

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  • Helios
    replied
    Don't forget

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  • WillieB
    replied
    I've got to think the odds of a porous weld are reduced with a good TIG weld. I wouldn't have the nerve to try with any other process.

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  • H80N
    replied
    Originally posted by CODE4 View Post
    Kevin,

    I have a Dynasty 280DX on hand - I was under the impression that an outside corner joint to fill would yield a stronger weldment than a butted L Shape fit?

    I am planning on pressure testing the tanks as well as baffling them.
    .
    That Dyn 280 is plenty enough machine for the job...
    But then again... I am a bit prejudiced... I prefer TIG when I can..

    If it were me I would go with the rounded fuel tank corners... they distribute the stresses instead of concentrating them...

    Be careful pressure testing... it does not take much pressure to baloon a tank like that and destroy it...(lots of surface area there) I would be very conservative... like ONE HALF PSI or LESS..and go over the seams with bubble water.. and look for bubbles...

    just my 2cents worth...

    Leave a comment:


  • Tryagn5
    replied
    Originally posted by CODE4 View Post
    Kevin,

    I have a Dynasty 280DX on hand - I was under the impression that an outside corner joint to fill would yield a stronger weldment than a butted L Shape fit?

    I am planning on pressure testing the tanks as well as baffling them.




    Arizona Joe,

    I suggested stainless to the guy, Russ, however he wanted AL - his call. I brought up several points to consider including the strength of the assembly, etc.
    Yes a corner joint is stronger, but if doing it with a spoolgun or push pull gun it is difficult even set on pulse. Since you have a dynasty should be rather easy, but will be a long weld. As long as there is a baffle in the tank it will be fine.
    Kevin

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  • CODE4
    replied
    Originally posted by Tryagn5 View Post
    What kind of welders do u have? If it were me, i would pulse weld the unit together, with my optima and xmt. Also everything would be press braked, where it could be. When i make fuel tanks i overlap the seams..ie think of to L's being sligthly overlapped. Same with the ends, much easier then trying to fill the end gap, but if you have a nice tig setup ie dynasty thats not much of a probelm. Also on the end caps i set inside the seam by 1/8 or so. Also besure to pressure test the tanks. Fyi besure to reinforce the tanks, ie use a baffle in the center with the corners cut off weld it in before the sides of course.
    Kevin
    Kevin,

    I have a Dynasty 280DX on hand - I was under the impression that an outside corner joint to fill would yield a stronger weldment than a butted L Shape fit?

    I am planning on pressure testing the tanks as well as baffling them.


    Originally posted by Arizona Joe View Post
    Why don't you make an exact replacement tank that won't rust out of stainless steel? By using aluminum you are changing the design of the tank. Hence, you are taking unnecessary risk. For instance, how do you know if the aluminum tank can handle the slosh loads on a sailboat?
    Arizona Joe,

    I suggested stainless to the guy, Russ, however he wanted AL - his call. I brought up several points to consider including the strength of the assembly, etc.

    Leave a comment:


  • Arizona Joe
    replied
    Originally posted by CODE4 View Post
    Good morning,

    Looking for suggestions or bookmarks for best welding practices of aluminum fuel tank.

    GTAW
    5052 0.125" ALUMINUM
    Approximate dimensions of 48" x 48" x 12"
    I am making two units for diesel tank replacement for a sailboat.

    Cuts and fits are tight, I am looking for beat practices on welding methods - back stepping my welds? Suggested bead length, if any?

    I admit I am much stronger with carbon and stainless, but have limited time running aluminum.

    Thanks.
    Why don't you make an exact replacement tank that won't rust out of stainless steel? By using aluminum you are changing the design of the tank. Hence, you are taking unnecessary risk. For instance, how do you know if the aluminum tank can handle the slosh loads on a sailboat?

    Leave a comment:


  • Tryagn5
    replied
    process and welder....

    Originally posted by CODE4 View Post
    Good morning,

    Looking for suggestions or bookmarks for best welding practices of aluminum fuel tank.

    GTAW
    5052 0.125" ALUMINUM
    Approximate dimensions of 48" x 48" x 12"
    I am making two units for diesel tank replacement for a sailboat.

    Cuts and fits are tight, I am looking for beat practices on welding methods - back stepping my welds? Suggested bead length, if any?

    I admit I am much stronger with carbon and stainless, but have limited time running aluminum.

    Thanks.
    What kind of welders do u have? If it were me, i would pulse weld the unit together, with my optima and xmt. Also everything would be press braked, where it could be. When i make fuel tanks i overlap the seams..ie think of to L's being sligthly overlapped. Same with the ends, much easier then trying to fill the end gap, but if you have a nice tig setup ie dynasty thats not much of a probelm. Also on the end caps i set inside the seam by 1/8 or so. Also besure to pressure test the tanks. Fyi besure to reinforce the tanks, ie use a baffle in the center with the corners cut off weld it in before the sides of course.
    Kevin

    Leave a comment:


  • H80N
    replied
    Originally posted by CODE4 View Post
    I am not boat savvy by any means, and I have not see the actual boat either. He cut the tanks out and brought them to his garage where I measured out the existing ones.

    Next time I meet him I will see what I can get for boat specs.

    I will be sure to snap some pictures of the fit up, before and after pictures.

    The tanks are going to get several NPT bungs, fill ports, and sending unit flanges cut and welded in as well.
    May sound like an odd point.... but..

    make sure the owner grounds the metal of the tanks to the bonding or grounding point in the boat...
    Basicly running a metal strap or wire from the tanks to the boat's common ground... otherwise salt water electrolytic corrosion can damage them in pretty short order....

    Leave a comment:


  • CODE4
    replied
    I am not boat savvy by any means, and I have not see the actual boat either. He cut the tanks out and brought them to his garage where I measured out the existing ones.

    Next time I meet him I will see what I can get for boat specs.

    I will be sure to snap some pictures of the fit up, before and after pictures.

    The tanks are going to get several NPT bungs, fill ports, and sending unit flanges cut and welded in as well.

    Leave a comment:


  • H80N
    replied
    Originally posted by CODE4 View Post
    Definitely more questions than answers

    No problem. The owner is installing them in his older 45 ft sailboat. They are going to be fully fiberglassed into the floor, replacing the original rotted out carbon steel tanks.

    They will be supported on 48" x 48" side, laying flat.

    Baffles will be installed before the last panel is welded on, H shape is pretty accurate.

    I understand what you mean regarding butting the edges up on the corner seams, to make an outside corner weld vs a modified Tee joint with weaker weld joint.
    I had a 41ft Morgan 416 Out Island and she could pound pretty hard in a blow... round bottom... fin keelers on the other hand can really be really brutal...

    type and make boat..?? Columbia 45 maybbe...??

    Leave a comment:

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