Welding gurus

hey everyone, im in the process of making some custom air tanks, my question is how many of you have been able to weld together an air tank that holds 150psi? Is it possible to do it by hand? I welded the first air tank and tested it with water and so far no leaks, but under pressure? Thanks for any input.

What are you welding it with? Arc, mig, or tig? What type of metal are you using? If your using old street signs then you may have a problem but if your building them into your bumpers that are 1/4 wall then you won't have any problems. 150 psi to a 1/4 box section is nothing, now if it were 1000 psi then I might worry a little.

Arc, good luck. Mig, better, less porous, tig, if done right there is no porosity but the metal has to be absolutely clean and free from contaminents.

Why do you need custom ones? Size? Wouldn't it be easier to just buy a small 5 gallon tank and mount it somewhere??

How did you design the ends of the tanks? are they flat plate lap welded or flat plate cut and butt welded? The ends are critical...a weld subjected to flex will eventually fail...Look at a commercially built pressure vessel...the ends are formed so the weld is stressed in tension. With flat plate, the ends flex in a cupped manner while under pressure, this flexes the weld. The amount is tiny, but can eventually cause the weld to crack.

The reason I brought this up is I have seen air tanks on semi trailers "repaired" by welding on new ends after the originals rusted thru. I have seen a large number of failures...If the tank(s) will live in the passenger compartment...well...better safe than sorry...commercial tanks are cheap.

i made a tank out of my front bumper, never had an issue at 175psi

I migged it btw

it's being mig welded, bought new steel 3/16" round tubing. I am making the tanks because of the size. They will be placed in between the bumpers so they are out of the way and does not effect ground clearance.

Stitch welding with a mig does not seal well, I was making a propane fitting adaptor 200PSI, and I could not do a single pass weld, or it would over heat the threads and dammage the adaptor so I had to stitch weld it, two passes and it still had a very small leak.

I wet back over the leak area with the oxy torch and it sealed it up.

So try to do a continious weld without stopping, if you get a leak oxy to tig heat the leak and it will seal up.

Its really tough to make a sealed weld. Thinner material is more difficult 3/16in woudl be easy, it will take lots of heat.

I guess thats the best way to do it, but one problem is i dont have a torch. I will pressure test the tank today and go from there. If it leaks I will try and figure out a way to use or maybe just buy a torch. Thanks everyone for the replies.

alright, I tested one of the tanks earlier, set it at 140psi and it held air. I put it into a bucket of water to make sure that there are no air bubbles. So im finishing up the other air tank and then will start installing them in the jeep. Thanks everyone.

etaniyani said:

alright, I tested one of the tanks earlier, set it at 140psi and it held air. I put it into a bucket of water to make sure that there are no air bubbles. So im finishing up the other air tank and then will start installing them in the jeep. Thanks everyone.

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itll only be a small boom if the weld fails, its all good

once theyre in the jeep, obviously its a concern if the welds break, but not anything serious because they will be surrounded by my bumpers. No one will die or get hurt, hopefully