[tweake]

looking at doing an aluminum outside corner repair on a tank.
its cracked and leaking. nothing flammable !

so whats the best way to grind the oil weld down ?

i'll see if i can hot link this pic

do i grind (bur bit?) it down to original sheet ie normal corner on the left in the pic,
or grind it flat like on the right which would make the center very thin.

the reason is its probably very dirty. i suspect the original weld did not penetrate well so it will have seeped into the corner.

was toying with the idea of grinding it flat, doing a small bead in the center thin part, then doing a wide bead over the whole thing.
i think i might get time this weekend to make a mock up and do some practice.

btw the thread that pics off is interesting. https://www.glen-l.com/phpBB2/viewtopic ... 7&start=15

[Darrin]

Not pressurised I take it?? If its not the base of a 40 000 gallon tank!! I’d just grind the affected area with a rotary burr, like your firs pic and build it up from there?? Maybe some more experienced guys can chime in, ive not done tank work!!

[Poland308]

Or groove it out with a thin wheel.

[MinnesotaDave]

I like square corners like the left picture.

[cj737]

Or groove it out with a thin wheel.

I'd go this way too. Not knowing the exact wall thickness or condition of the weld, a V groove down the center should allow you uncover the unfused root without disturbing the edges and distressing them.

If the thing is oil-soaked, you're in for a hot mess. Clean it, preheat it to drive out the impurities, clean it again, then clean it some more. I've done a far number of ally engine case repairs (among other parts) that I run the torch over without filler to put some extra heat into it, and check for porosity. When it comes time to weld, I run my machine at 65% Balance, and 50%. And I will either use 4943 or very often 5356. I find they perform better and endure the heat cycles better.

Remember, all the heating and welding up the seam can cause internal pressure and when you approach closing the seam (depending greatly upon size of the tank) you may need a vent elsewhere lest you blow your weld back out. Or, you need to wait and let things cool down and whip it closed separately.

[motox]

tweak
interesting thread.....
craig

[tweake]

Not pressurised I take it?? If its not the base of a 40 000 gallon tank!! I’d just grind the affected area with a rotary burr, like your firs pic and build it up from there?? Maybe some more experienced guys can chime in, ive not done tank work!!

good point.
its ~200 gallon tank. fits on the back of a pickup.
nothing oily, mostly water.
alum size, not to sure. possibly 3mm 5 series sheet.

this has been "repaired" at least once maybe twice. looks like a cold mig job.
thats why i'm hoping to get a crack at it, rather than it being sent back and its gets another blast with a mig.

[Rstamp]

I would cut a slot in it with a thin 3" cut off wheel , then bevel the edge lightly wire brush it good, preheat it to drive off moisture light up on it when both sides puddle stab filler right at the base of the puddle an move out putting the rod right in the little hole in the base of the bead I use 5554 at work to put asphalt trailers back together that way

[tweake]

well i made a couple of mock ups.
one was the right hand pic where the corner is ground flat.
i fully suspected it to melt right through and be a mess. but it went straight forward.
penetrated well for modest input. but i think its not enough metal in the corner and would really need a 2nd bead to build the corner up.
the other i simulated a cut through with a disk. this one was more problematic.
i ended up running 140 amp (3mm material) to get any decent penetration. thats probably due to martial is thicker on the angle and your trying to weld 4mm thick weld. however doesn't look like any need for 2nd pass.
but cutting it with a thin disk may mean that if previous weld didn't penetrate then dirt could still be present. with grinding the whole corner flat you completely remove the old material edge and any dirt with it.
btw i had a good pop, looks like some crap on the backside came through somehow. how can i avoid that happening? pre heat and burn it off ?

[cj737]

well i made a couple of mock ups.
btw i had a good pop, looks like some crap on the backside came through somehow. how can i avoid that happening? pre heat and burn it off ?

Yes, and grind out some of the existing weld.

[tweake]

well i made a couple of mock ups.
btw i had a good pop, looks like some crap on the backside came through somehow. how can i avoid that happening? pre heat and burn it off ?

Yes, and grind out some of the existing weld.

existing weld will be long gone no matter what way as i suspect thats whats causing the cracking issue. but tank will certainly not be clean on the inside.

[Poland308]

If you cut with a thin wheel first and then grind off a little of the weld you should be able to find a happy place. As far as the holes or crap pulling through, I would just go back after and re grind the same way. If there’s lots of contamination you may need to repeat the grind weld process several times, but probably only in a few areas.

[tweake]

well the day came far earlier than expected.
the boys came back with a big leak, but it was a new leak. an entire corner had cracked open.
so now there is 3 leaks to fix.
big one first.

cracked corner

image005.jpg (40.65 KiB) Viewed 1227 times

image006.jpg (42.94 KiB) Viewed 1227 times

you can see the sort of welding i'm up against ! and thats some of the better welding on this tank.

so tonights effort was to grind that off and reweld it.
i ground it a little to much and ended up with a bigger gap than i wanted. then i had no end of trouble getting 5356 to flow.
ended up starting to blow holes. switched to 4043 and that went fairly nice.
then capped it with 5356. not sure how the two fillers react with each other.
a few moments of teaching the tungsten to swim as you can see.

fixed

image008.jpg (45.43 KiB) Viewed 1227 times

would have really liked to use the tig finger and stubby gas lens on this but they are in transit. that tank was getting fairly warm to have my hand on.
had to use my stick welding glove to rest on.
the other leaks is tomorrows job.

[cj737]

What settings were you using on your machine to weld that with? I ask because your cap weld looks a bit "roped up" and not wetted in. Outside edges are a real challenge with aluminum to get right.

One trick you might try, is to lay/clamp some flat stock just outside the weld are, parallel to the corner joint. This will act a bit like an argon dam, and help you trap that gas and get things really cooked in. Even if you tack some ally flat bar that you later knock off and flap disk the tacks. Some 1/4"x2" stock works great. It also can help prevent heat soak on thin sheet as you roll along, buying you some time with the arc before burn-through.

I find it interesting that others have difficulty with 5356, or it cracking. I find that to be true with 4043, but never have I had that issue with 5356. I do also use 4943 instead of 4043 for the same reason. I do wash the weld with post flow to aide in cooling it though, so perhaps that's the difference?

[tweake]

pedal set at 140 amp max. last bead was foot to the floor for most of it.
frequency is fixed, no idea what it is. balance is somewhere around 70% en (dial isn't really marked).

the original welds where not done my me. that was someone else using a mig. no idea what spec filler they used.

[tweake]

well its done.
the last two where more pain than fun. my welding is to horrible to show.
ground off the small leak to find a big long crack. instead of 1" weld its 2 feet of weld, and just nasty.
i could smell the gunk cooking. plenty of rubbish floating in the puddle. holes to patch up, some thick bits which required welder at max and pedal to the floor. fair bit of tidy up. just ewwww.

last one was under some timber. pulled it off, cleaned it up. tons of suspect welds, couldn't find anything for ages. but then noticed a crack in the middle of the plate. something must have punched in at some point, just enough to crack it and not dent it. a quick gouge out with burr bit and fill it up.

[cj737]

Weld for strength, then weld for pretty. Repair work, especially on unknown ally thats been in "service" absolutely sucks. You never know what you'll get in to, and you always will encounter smutz you hoped to avoid. Short of grinding everything out to bare edges, its a labor of aggravation in my experience.

I've had to repair a few ally Jon boats that live their lives in brackish water, highly alkaline too. Nightmare of contamination to weld up. It takes far longer to clean and prep than to weld. And then the welding is a major source of tricks, techniques, patience and cussing. So I doubt your welds are so ugly that you should be embarrassed; instead you should be proud of yourself for getting it done properly!

[Poland308]

Sometimes (Doesn’t Leak) is the only measure of success.

[tweake]

the good news is it didn't leak. the lads where using it today.
the bad news was while i was doing the tank someone else was adding a bit to the platform the tank sits on.
unfortunately they used 3/8 plate and the forklift forks would not fit in. spend part of the morning cutting all the new steel out.

and to top it off, i get home and there is a parcel from weldmonger sitting here for me. its actually arrived really really quickly. pity the tank job was brought forward so much.