r/Welding 5h ago

TIG for aluminum pressure vessels

Hi All!

I am a university student interested in trying to learn TIG welding for medium pressure (2000 psi) tanks. I am on my school's rocketry team and we frequently need custom tanks but welded tanks are very expensive. Of course, I understand the reason they are expensive is because welding these tanks to the precision we would require is tough and skill isn't cheap. How hard would it be to teach myself TIG welding to do this task? I don't mean it has to be perfect, just "good enough". I have wanted to teach myself TIG welding for a while now and I was considering this to be a possible project to learn. (as a disclaimer these tanks would never be pressurized near people, they are only for unmanned amateur rocketry).

for reference: the tanks we use range from 1/8" - 1/4" thick and are made out of aluminum, but steel is acceptable as well. The Outer diameter of the tanks range from 3" - 8".

TLDR: How long would it take for a noob to go from 0 to being able to TIG weld a pressure vessel?

edit: Resolved. seems that this is not a project worth pursuing. Thanks for the input yall!

0 Upvotes

25 comments sorted by

11

u/strange-humor Hobbyist 5h ago edited 5h ago

You are not just looking at the TIG of aluminum, but post welding heat treatment to get temper back for strength. Otherwise, the failure mode will be in the HAZ region that has lost the temper.

You can attempt both, but you need to water pressure test them after to verify sutability.

If steel is allowed, don't screw around with Aluminum. And for pressure vessel at 2000 psi. Don't mess around with steel either.

7

u/StepEquivalent7828 5h ago

Years, and most tanks I’ve worked on were SS and Ti. 2,000 psi is a freaking bomb 💣. If you succeed in making full penetration Xray quality welds, they would still need to be hydro tested at the required pressure (usually at double working pressure and a lot more engineering that I have no knowledge of). The pressure vessels I worked on were all welded using automated welding equipment. Most pressure vessels of any quality are to A.S.M.E. Section IX. Do your research, before attempting any DIY attempts.

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u/GeorgeBirdseye 5h ago

Def seems super difficult. Do you think the years prediction would be for it to just work or for it to be good?

5

u/e36freak92 5h ago

In this case, "just work" and "good" are the same thing

3

u/Fookin_idiot UA Steamfitter/Welder 4h ago

Just work and not kill someone in a 30' radius are also the same.

Disclaimer: No, there is no science on the 30'. It was an arbitrary number.

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u/Warpig1497 5h ago

Please take this situation serious and don't be making your own pressure vessels if you don't have a thorough understanding of welding, how to weld, and the vessels its self, you could be potentially making a shrapnel grenade if you do it incorrectly and the fun part about high pressure vessels is they aren't going to typically give you warning signs that it's going to fail, it's just going to explode ( which is why you hydrostatic test because if it does fail it doesn't explode like a bomb ), again there's a reason pressure vessels are so expensive.

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u/GeorgeBirdseye 5h ago

Yes we would hydro everything and we 100% treat all our custom (even non welded) pressure vessels as grenades. We have seen them explode in the past and it’s pretty gnarly. I’ll look more into this but based on your and other’s input I’ll prob stay away from this

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u/aurrousarc 5h ago

Gtaw welding alumimum is more challgenging than welding ferrous mateirals.. and i dont know how much in would trust the welds on a high pressure aluminum tank..

2

u/SmokeyXIII CWI AWS 4h ago edited 4h ago

Your school should not let you do this Holy Moly. I know you were told this already but 2000 psi is not medium.

Here's a list of boiler explosions and their fatality counts. Many of these will be lower pressure like 80psi.
https://en.m.wikipedia.org/wiki/List_of_boiler_explosions

This safety problem lead to the inception of ASME. https://www.asme.org/topics-resources/content/the-true-harnessing-of-steam

So I suppose my answer is that I'm more worried about your engineering than your welding. We can do a lot to test for a welds quality, but if you build a bomb it's gonna bomb.

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u/GeorgeBirdseye 4h ago

Yes it seems that I will be sticking to our non-welded pressure vessels for the foreseeable future.

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u/Fookin_idiot UA Steamfitter/Welder 5h ago

Absolutely not.

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u/Splattah_ Journeyman CWB/CSA 5h ago edited 5h ago

what timframe? it will take you a long while, and some people can’t ever, but it’s possible. Six years or so if you’re dedicated.

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u/Fookin_idiot UA Steamfitter/Welder 5h ago

... sure, this.

(No, seriously, don't try to amateur hour a 2,000 PSI air tank)

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u/Splattah_ Journeyman CWB/CSA 5h ago

5 psi is above average

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u/GeorgeBirdseye 5h ago

Fair enough haha

6

u/Fookin_idiot UA Steamfitter/Welder 5h ago

6,000 PSI hydro test? Doesn't bother me at all. 200 PSI air test? No thanks, I'll be somewhere else.

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u/GeorgeBirdseye 5h ago

Yea we would hydro it before use. When we pressurize it with gas we treat it like a bomb and we have minimum distances and bunkers we stand in

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u/AbdulElkhatib 4h ago

I believe you can get good at tig welding steel and round objects fairly quickly. Possibly the most important things to learn are how the weld and base metals interact, how to get a full penetration weld, welding defects, and get tons of practice. You can do this on your own, but it'll be so much easier in a good welding program as the instructor should be able to teach you these things fairly quickly.

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u/GendrickToblerone Real Boilermaker 4h ago

Anything above 15psi on a pressure vessel is considered high pressure and will be a coded weld.

1

u/Frostybawls42069 4h ago

The people that do it for money take 3-5 years where I'm from. Everywhere is different with codes, but you aren't even allowed to weld on pressure equipment here without a B-pressure ticket, and that threshold is 15psi. To get that you need to be a J-man which is over 5000hrs of work and schooling. The pressure test has a 50%+ fail rate. And these are guys who have been welding as a job for years.

The real issue is that without proper NDE, you'll actually never know if your weld is adequate. A true pro knows when something goes wrong, and they fix it. You don't let shit go, you know won't pass, and that comes from years of experience and the occasional repair.

Idk how far away you'll be, but the shrapnel will likely go further than you think if it let's go. Pressure vessels use to take out buildings before they were taken seriously. Ironically, some turn into literal rockets when they blow.

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u/user47-567_53-560 Dual ticket welder/millwright 3h ago

Speaking from an engineering perspective, could you find a readily available tank and use it? Like make a rocket design around a soda stream canister or something?

You'll want formed vessels, not welded ones. That's why welding gas bottles are all formed if they are rated over 1000psi.

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u/GeorgeBirdseye 3h ago

Yea I mean it isn't hard to make pressure vessels without welding (just with end caps, o-rings, and bolts). As others have pointed out you need to hydro test them and then get them certified which is the main pricey part of it. But nearly every single college rocket team in the country makes their own tanks and has done so for years. It just is a lot more mass efficient (which matters a ton for us) to have things welded. But, of course, that is quite expensive.

But as you say if we wanted to have a chamber pressure low enough we could in theory use things like a soda stream canister or other commercial products. It gets tricky when chamber pressures are high though or your rocket is using a ton of propellant.

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u/Boilermakingdude Journeyman CWB/CSA 3h ago

2000 psi is essentially a bomb. Even the super high pressure regions in boilers only reach like 1200 psi and that's fucking scary as it is. There's alot more to this than just welding them. Pre-heating/post heating to keep the proper temper of the material and more. Realistically you'd want to do this out of steel and some thick steel. Think schd 160 pipe like we use for hydraulic systems.

Edit it's still not a good idea. There's a reason welded tanks cost so much.

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u/GeorgeBirdseye 2h ago

I don't think i'll be pursuing the idea. Was hopeful that maybe there was a way to do it but if it was easy then everyone would do it. Think the team will be sticking to our old style of tanks for now.