[31fords]

I have a job coming in to repair small leaks on an aluminum gas tank. This is a brand new tank which has never seen any flammable liquid as of yet. The builder has applied very low pressure air to test for leaks and there are a few I would like to try to repair.
The rectangular tank is very close to 1 ft. X 1 ft. X 2 ft. long using 1/16 thick aluminum sheet. (dont know which code) The process used was MIG using spool gun with I will presume DC power.
I have plenty of good welds with thin steel, also silicon bronze brazing using TIG. did only a few beads on aluminum with good results, but plan on practicing a lot before attempting the repair.
The leaks are mostly pinholes around the fill and outlet areas and a few where the inner baffle plates attach to main outer skin.
.
I would like to get an idea of what process you more experienced guys would use.

I'm thinking along the line of aluminum bronze using AC, or Jody's rule of 33.

Please let me know which process I should use and any special notations I should be made aware of.
Thank you
P.S. every time I need a refresher course I go to Jody's site

[Olivero]

well, I would never weld a pressurized gas tank, well..... I might depending on what's in it but I wouldn't give it to someone else to use ESPECIALLY if its flammable or toxic gas.

But safety and responsibility concerns aside, depending on the thickness I would TIG it. I once got an expansion tank for a hydronic system which had a leak near the bottom, the boys at the plant had tried to stick it back together but kept not succeeding, lit up with my TIG and revealed the leak in 10 seconds, welded it back up and just padded it with beads for good luck.

Especially if they are pinholes, you should see the hole open up once you light up on it and will be able to patch it very carefully, HAZ is also a concern to take into account so you want to find it and fix it very fast to reduce that HAZ.

But yeah, that ought to do it, you said the tank was aluminum? Make sure to bring your cleaning on if you can adjust balance, problem with tigging used tanks is the inside of the tank can contaminate the weld, especially if the hole has been exposed to humidity and oxidized and Blaaa blaa blaa.

BUT there is also a way to solve that, drill the hole out to an 1/8" hole and then plug it back up.

Good luck and please, consider the safety concerns a new tank is cheaper than the lawsuit or the injury someone could attain from it failing.

[31fords]

Olivero:
I know the complete history on the aluminum tank, another welder by trade made it for a buddy of mine and it has never had any flammables inside the tank. Only low pressure air to check for leaks. The leaks are pinhole size. I was also thinking of purging it with argon but wonder if it would make any difference. The tank is made from 1/16 inch aluminum.

[cj737]

The purge won't hurt, but it's not necessary. If the tank was MIG'ed, it was done with DC, you're right about that. Is your question basically can you braze it successfully or should you weld it? I think in this instance (new, unused, clean) I'd opt to weld it. If the pressure test revealed pinholes, and they are accurately marked, I'd drill them open cleanly to insure you get full depth closure. Dropping weld over a hole will create a void that would be prone to leaking later.

It would be wise to know the series of aluminum used and match your filler rod appropriately. At least 4043/4943 or 5356 series rod. You shouldn't need pulse but instead just good heat control to get a complete seal.

[dave powelson]

I have a job coming in to repair small leaks on an aluminum gas tank. This is a brand new tank which has never seen any flammable liquid as of yet. The builder has applied very low pressure air to test for leaks and there are a few I would like to try to repair.
The rectangular tank is very close to 1 ft. X 1 ft. X 2 ft. long using 1/16 thick aluminum sheet. (dont know which code) The process used was MIG using spool gun with I will presume DC power.
I have plenty of good welds with thin steel, also silicon bronze brazing using TIG. did only a few beads on aluminum with good results, but plan on practicing a lot before attempting the repair.
The leaks are mostly pinholes around the fill and outlet areas and a few where the inner baffle plates attach to main outer skin.
.
I would like to get an idea of what process you more experienced guys would use.

I'm thinking along the line of aluminum bronze using AC, or Jody's rule of 33.

Please let me know which process I should use and any special notations I should be made aware of.
Thank you
P.S. every time I need a refresher course I go to Jody's site

1-Before I would start:
sniff the tank for volatiles, if nose detects, then check with LEL meter, visually inspect inside for fluid.
....Trust---but verify!
material & temper of the sheet?
weld filler used by the weldor that doesn't know how to seal weld?
construction photos of baffles & baffle to tank wall joint, the fit-up and those welds?
" " of end plates, fit to tank shell and tank shell joint?
" " of filler and outlet fit-up b4 welding?
" " tank shell halves, fit-up and joint method b4 welding?
amount of tank wall distortion from welding, any freely flexing areas of tank wall?
visual inspect and mark weld/joint areas for cold starts/laps/cold stops, craters, porosity pin holes

From your description, this is a hack-together tank shell of OOHHH--TOO---THIN material, that can
further distort/rupture in an un-friendly way under pressure test. I would suspect that even getting
it seal tight would be pointless, since it will crack in actual use--which you haven't bothered to indicate
exactly what the end use is to be?

On fragile, questionable tanks as the above--for p-test I use regulated air with one or more 'blow-off' patches
of duct tape (to release any significant pressure buildup), begin pressure flow with one hand feeling the pressure on
the blow-off patch, which looking at the tank shell for any amount of flexing/movement as pressure increases.
The total pressure may only be 1-2#. On a tank like this, probably not more than a pound. I don't watch the gauge,
I'm looking for tank wall distortion, while feeling the relative amount of pressure against the patch.
(I don't have scars from blown up tanks/ mine don't leak and actually see good service in use.)

-Filler, probably 5356--depending on actual sheet alloy, using AL bronze is incredulous....
-Seal welding with TIG requires a skill level as does seal welding with MIG
-grind/carbide burr back the weld-only, then wet/fill/run puddle (watching and getting really good edge wet-out/fill/flow, before, over, and past the leak point; fade down and backfill if needed for NO CRATERS)
--use wet sponge or water bottle spray with air blowoff to stop heat spread and distortion. Don't let tank get hot.
More distortion= more stress into an already stressed tank.

'The leaks are mostly pinholes around the fill and outlet areas
and a few where the inner baffle plates attach to main outer skin.'

--Leaking at the baffle plate to skin joint, indicates cracking thru, due to:
-no flanges on the baffles, skimpy amount of weld on (I'd suspect) a tee joint
*****this TIGHT cracking occurred during previous pressure testing....soo....at this point the tank is even more fragile and apt to rupture without internal baffle support. Addressing/repairing the baffle to tank wall connection is first/major priority.
How to do? Depends on questions asked prior. Usually involves cutting thru tank wall to install flanges/etc.; plug welding flanges as needed, etc......and depending on rest of tank details---this effort makes it not feasible.
Welding over the tight crack of the baffle to skin joint is a band-aid joke that fails promptly in service, if not in pressure test.

From seeing failures, I firmly believe in fully flanged baffles, fully welded out on the lapped flange side-not intermittent or stitched, since those love to create stress cracks through the skin.

inlet/outlet/all fittings--burr/grind out leak areas and proceed as prior noted.
Using doubler plates for such fittings, really helps in stress distribution, tank strength, etc.

That's some of what's involved in a simple tank fix job.

[Poland308]

Hydro test tanks! Use of air is very dangerous. One place I used to work had two guys next to an aluminum water tank for a cement mixer truck. They were pressure testing it for leaks with air. It exploded one guy died from shrapnel and the other lost an arm and a leg.

[Otto Nobedder]

31fords, I see a lot of people didn't read the original post very well. I'm in agreement to TIG weld the repairs, HFAC, and I agree with drilling the leak points to ensure penetration.

The two problems I see are, this should have been 11 gauge (1/8") in the first place, as evidenced by the blow-through leaks at the inner supports/baffles, and now you have to try to fix 1/16" aluminum without blowing holes in it.

If it were me, I'd advise scrapping it and build a new one out of the appropriate material. You'll spend less time beating your head on the floor.

Sil/Bronze "can" work, but you still have to prep everything as for a weld. It's not going to flow in to an un-prepped pinhole.

Poland is right about the hazards of pressure testing with air, but at the (say) 2 PSI max you're looking at, the hazard is small. It still exists, since you didn't build it and already know there are multiple weld failures.

Who the hell calls himself a welder yet tries to MIG 1/16" aluminum into a fuel tank?

Disjointed rant finished...

Steve S

[5th Street Fab]

I agree with Otto even the smallest tanks I've built have been from 1/8". When we get porosity or pin holes we cut that section out and tig it. We only mig the real big tanks to save time. Tig all the smaller ones. It'd be cheaper and easier to cut out a new one out of 1/8 and personally I'd tig it. We pressure check them at 3.5 psi for half and hour (coast guard regs.)

Sent from my SM-G920V using Tapatalk

[Olivero]

No other real way than to TIG it, that's the closest you will get to an unharmed piece of aluminum.

Like others mentioned, drill them out, weld em up and check it. Really simple. Don't need to pulse just be really F ing careful, gravity is not your friend in this case and if you overheat and do the good ole' bloberoony move your gonna be looking at something much worse as you got a blob of metal in the tank AND a bigger hole.

I would turn the cleaning as high as practically possible to reduce your heat input and use some 3/32 or smaller diameter 4043 or 5356 it should do what you need.

Now get to it man, I wanna see it.

[nelson]

Otto/Steve, I agree. Scrap it.
I composed an answer last nite and posted it to the wrong cloud I guess...sure wasn't here. Seems the OP has similar hood time as I do. I'd blow a hole with the first foot press. I suggested use low temp braze and practice thin AL TIGing for the next time you see a job like this.

Am I right about the braze..with good prep and lots of flux if it were an emergency?

[Otto Nobedder]

Otto/Steve, I agree. Scrap it.
I composed an answer last nite and posted it to the wrong cloud I guess...sure wasn't here. Seems the OP has similar hood time as I do. I'd blow a hole with the first foot press. I suggested use low temp braze and practice thin AL TIGing for the next time you see a job like this.

Am I right about the braze..with good prep and lots of flux if it were an emergency?

Yes, brazing can work. I mentioned that, I think. The issue is prep... Finding every single pinhole leak, and drilling it clean to a size that will accept the brazing filler. At that point of prep, TIG welding is as easy as brazing, IF you can control your heat input. Frankly, I'd have the filler in place like lay-wire, and hit it with 200A for about 2/10 second, like flash-tacking.

Given my choice, I'd still scrap it and build from 1/8"

Steve S

[Rudy Ray]

Okay, I've been a "professional" welder for about 15 years now and have never heard of using Silly Bronze on aluminum. Am I missing something? If anything, perhaps Alum Bronze, but I have yet to even try that as my LWS would need to order it because they don't keep it in stock.

[exnailpounder]

Okay, I've been a "professional" welder for about 15 years now and have never heard of using Silly Bronze on aluminum. Am I missing something? If anything, perhaps Alum Bronze, but I have yet to even try that as my LWS would need to order it because they don't keep it in stock.

You're right. Aluminum melts way before bronze so this wouldn't work.

[Rudy Ray]

Okay, I've been a "professional" welder for about 15 years now and have never heard of using Silly Bronze on aluminum. Am I missing something? If anything, perhaps Alum Bronze, but I have yet to even try that as my LWS would need to order it because they don't keep it in stock.

You're right. Aluminum melts way before bronze so this wouldn't work.

So, what I'm getting from this is that most people can not comprehend from the original post or the title of the post that this tank is made from ALUMINUM !

[Olivero]

Just drill em out and weld em up, its not the easiest way but seems he doesen't care and just wants to go at it, I don't blame him.

We are gonna keep fighting over this until you just say its done and works