Can I weld on a compressor tank?

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I have this 25 gallon compressor and the tank has a hole and a crack in it.  I really don't want to junk the thing because the motor and head are both real workhorses, something hard to find in todays market without spending a ton of money.  I was thinking about using a small drill bit to stop the crack on both sides and welding it up.  Then using a slightly larger bit, 3/16 or so and trying to fill the hole with weld.  Or using a larger bit, 1/2" and trying to fit a piece of metal in there.  I don't claim to be a master welder but I know my way around my 110v Mig and have done quite a bit of bodywork and other projects with it.  Is this something I could reasonably do or am I asking for disaster?My other option is I have a newer tank from an oil less compressor.  I could put the head and motor from this tank on there but that would require cutting the welds and removing the mounts from the old tank and welding them to the new one.  If both are a really bad idea I might be able to rig up something to bolt it on by welding nuts to the mounts on the new tank.  I would rather have it welded if possible though.For reference both of those black circles are about the size of a nickle.Edit:  The more I think about it, it's probably a bad idea to try and weld that hole up.  It looks like it's caused by rust so their are probably more just waiting to happen even if I do get it properly repaired. Attached ImagesLast edited by pyro9862; 06-20-2009 at 10:05 AM.
Reply:I wouldn't and I take risks I shouldn't from time to time.  Here's why I say no.Those holes/cracks indicate the underlying cause for them which is corrosion from the inside perhaps as a result of inadequate drainage over the years.  I've tried to locate them before and couldn't but there were several photos of air tanks in a thread that failed as a result of such corrosion and they aren't a pretty sight.  I don't recall if any resulted in death or injury but I would draw the line at trying to repair that tank.  Your best bet - get a new one as that tank shell has been compromised and weakened by corrosion.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:It's shot! Convert the other tank or find one. Don't weld any tanks. And this will be repeated so just to save everyone the trouble do a search on here for air tanks it has all been covered.
Reply:You could weld just about anything. Don’t bother, the tank looks to be at the end of life.Secondly, after welding the tank MUST be pressure tested, and not by compressed air or any other gas. [ BOMB]  testing is done by hydraulic pressure, very little stored energy if something lets go.
Reply:Originally Posted by transit. . .very little stored energy if something lets go.
Reply:You can buy a new ASME tank in a selection of sizes (vertical of horizontal), already set up with a platform and fittings, from many distributors including Graingers. That's probably the safest and cheapest way to go.
Reply:Long ago, I was working in one of our garages. There was a loud BOOM. A mechanic was mounting a tire on a rim. Good thing the work is done in a tire cage behind a wall. It looked like a 75 mm shell went off.
Reply:im a superintendent on construction at a prison. we had some plumbers come in torepair some leaks in a low pressure steam heat system. i identified all the leaks before the work  started. guess what.. every leak we fixed just let the pressure build up a bit and caused a new leak 3 feet away. that tank reminded me of that project(which i put a stop to).we replaced the system.. please replace the tank.
Reply:Make a bbq grill out of it.  No pressure there.  25 gallon is just the right size for the back porch.Esab Migmaster 250Lincoln SA 200Lincoln Ranger 8Smith Oxy Fuel setupEverlast PowerPlasma 80Everlast Power iMIG 160Everlast Power iMIG 205 Everlast Power iMIG 140EEverlast PowerARC 300Everlast PowerARC 140STEverlast PowerTIG 255EXT
Reply:Sounds like I'm replacing the tank then.  I'll check out Graingers to see what they have for new ones.  Most likely I'll try to cut the mounts off this tank and bolt them to the mounts on the new tank since these are much higher and should fit over it.  The only thing I have to worry about is the compressor head will sit directly over the inlet on the new tank and opening for the pressure switch will sit directly under the motor.  I think I could route the fill line with some type L copper pipe and sneak it in and probably run the line over a little bit with black iron for the switch.  I could even mount the head and motor on a piece of plywood and have it totally seperate from the tank as the compressor generally never moves.  In any case I'm inclined to agree with everyone here, the tank is shot and new holes will just continue to pop up.  I just hate to throw away the head and motor as they are fine and would be a small fortune to replace with something of equal quality.
Reply:If you mount the compressor seperate from the tank use a hose, not hard pipe to connect to the tank to avoid vibration issues. A good hydraulic shop can fab you a good hose cheap. The old shop I used to work in had the tank mounted in the attic rafters and the compressor in the shed out back behind the shop wall to limit noise. They just ran a long drain down the wall so you could drain the tank easily each day.
Reply:Originally Posted by lugweldMake a bbq grill out of it.  No pressure there.  25 gallon is just the right size for the back porch.
Reply:pyro, if you do wind up mounting the compressor/motor seperate from the tank, I suggest the hose verses solid pipe too but run a section of coiled copper (supported) or SS braid reenforced teflon line before the hose to disipate the heat of compression.  If not, the hose (if not meant for compressor discharge service) will fail before very long due to the heat.It's nice to hear you plan on replacing that tank.  We'd like to see you stick around here for awhile.  Besides, I don't think you'd want to live with a buddy or family member getting hurt if they were in the area should it fail in use.  Smart choice.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:Well this thread is no longer welding related but I always hate when I reply to a thread and never find out what happened.  I cut the mounting bracket off the old compressor and have it ready to mount to the new one.  You can see now what I meant about the old and new inlet holes not lining up.  They're so different because the new tank was an oi less model.  I'm going to mount this lining the finned copper up with the new inlet so I can re-use that same piece.  That brings the mount further up on the new tank then it was on the old.  That isn't going to hurt anything, I'll just have to shorten the handle up a little so it's not too long.  As for attaching it I'm going to drill two holes in the old mount that line up nicely with the new mount so those can simply be bolted together.  I don't see that that is adequate and need to attach the front somehow.  I was thinking about just putting some kind of strap around the whole deal to hold it down but that is kind of hacking it.  My second idea is to bolt/weld two piece of angle iron to the corners the new mount extending forward so I can add a set of bolts towards the motor.Right now I'm stuck because I need a 3/8 black iron street elbow to run the compressor outlet out from under the pump.  I'm going to put that and the switch setup right next to the inlet.  I also need to come up with the metal to make my mounting bracket as I only have real heavy angle iron around.  An old bed frame or something would work nicely.
Reply:Forgot the pics.And what do you guys thing about vibration.  Is smoothing out the old welds good enough or will the vibration eventually cause the old mount to eat through the new tank? Attached Images
Reply:It would be ok to weld the mount to the tank, just give it 3 or 4 2 inch long beads along the length.  That's better than letting the mount vibrate against the tank.
Reply:Originally Posted by 76GMC1500It would be ok to weld the mount to the tank, just give it 3 or 4 2 inch long beads along the length.  That's better than letting the mount vibrate against the tank.
Reply:I was under the impression I shouldn't try welding to the tank at all.  This picture is it all finished minus the wheels and I want to change that piece of 1/4" aluminum pipe going to the pressure switch.    I extended the mount on the new tank out and bolted this setup down to it.  To solve the vibration issue I threw in a few washers to the head/pump mount is actually sitting about 3/16" above the tank.  Those sides aren't touching.  It's good to know that if for some reason this doesn't work out I can just drop it down and weld it to the tank.Thanks for the help guys.
Reply:Again, forgot the pics. Attached Images
Reply:I would avoid welding to the tank itself. If you choose to do so, it should be retested. If you have any undercut or porosity, the tank can fail under pressure at that point with little to no warning. Even at a measly 100psi theres a LOT of force on that tank trying to rip it apart.Stick with bolts and if it needs more support, just add some rubber "feet" that can rest on the tank.
Reply:Weld onto the tank?  Glad you replaced the original end-of-life tank.Regarding the 'new' replacement tank, do NOT weld onto the tank itself!!!!For the mounting bracket, rig up whatever you want/need to adapt the existing motor/compressor bracket to the bracket on the tank.  Make your bolts or welds to the brackets and you should be fine, but do NOT bolt or weld to the pressure tank itself.   The best laid schemes ... Gang oft agley ...
Reply:It's ok to weld to the tank, it's not ok to try to repair a crack, especially a corrosion related crack.  Don't introduce any weaknesses, though, like under cut.