aluminum fuel tank - best welding practice

[CODE4]

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.

[Portable Welder]

I would use a 3/32 filler rod, bend up as much as possible with a press brake.

Just go through and tack it up and then weld it up.

The biggest thing to do is corner to corner welds so you can get a nice thick weld.

what I mean is dont overlap the plate onto the other, bring your edges together and put the tack when the first meet.

[H80N]

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.

More questions than answers...

How many baffles and confifuration..?? "H" shape baffle..?

Rounded edge or sharp..?? ( Radius bent corners spread the stresses... sharp ones concentrate stresses)

Strap mounts or tabs??

Mounting place.. flat and supported or will it support itself over an open area..??

lets see... 12 Cubic foot = 90 gallons..(89.76623376 US Fluid Gallons)

90 X 7.15 Lbs Per Gal = 643 Lbs... fuel weight..

and SEVERAL times that in a pounding following sea during a storm...

.. things to consider

How about some pics of the proposed mounting place..?? and old tank..??

[CODE4]

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.

[H80N]

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...??

[CODE4]

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.

[H80N]

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....

[Tryagn5]

process and welder....

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

[Arizona Joe]

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?

[CODE4]

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.

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.

[Tryagn5]

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

[H80N]

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...

[WillieB]

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.

[Helios]

Don't forget

[WillieB]

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.