I want to cut a air compressor tank open

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I have this salvage 80 gallon vertical air compressor tank I want to cut apart (yard art here I come) and don't want to win the darwin award for stupidity. I want to cut one end off near the weld seam.I know all about the no-no's on cutting into gas tanks, fuel tanks, etc. but not sure if this tank poses the same problems. I drained about a pint/quart of old scum/oil residue out of the bottom pet ****. The tank has been sitting for about 6 months with all the other fittings taken off so it is just residual contaminated air in it. Is the air being contaminated by the oil residue a problem? Is the inside walls of the tank coated with oil now? I don't care if it burns, just don't want it to blow up.I'd rather not fill it with almost 80 gallons of water but will if that is what is recommended. Or how about car exhaust? I can rig that up. Purging it is not an option. I can cut it with a plasma cutter or a sawzall or a cutoff wheel (ugh). Obviously the plasma cutter is my first choice.Opinions please. thanks.
Reply:I wouldn't be too concerned about cutting a known air tank under these circumstances, although, the option of purging it with Carbon Monoxide from a car exhaust certainly wouldn't hurt anything.Nitrogen or Co2 are superior purging agents if you have them available.Appreciation Gains You Recognition-
Reply:I agree with franz I would not be too concerned about cutting it. And if car exhaust makes you fell a Little better, dont hesitate to pump some in while you cutno you cant fix it with a hot pass.BORN TO LOSE, LIVE TO WIN.
Reply:Dave,Shouldn't be a problem.  I've cut two small truck air system tanks open using my O/A torch with no surprises.  I would not expect there to be enough oil residue in the tank to form an explosive mixture, but the CO idea from the car exhaust is cool!Be well.hankj
Reply:As long as all the fittings and plugs are out, plasma away.  Car exhaust is overkill.  Explosions happen when the fumes are between the lower explosive limit and upper explosive limit of the chemical the base oils  in compressor lubes typically do not have a LEL or UEL they have too high a vapor pressure to worry about.  Solvents and fuels are a different story.  Diesel and kerosene are not too bad.  Gasoline can be a little scary.Ron ShopFloorTalk Millermatic 350P, M-25, M-40 gunsDynasty 300DX, Coolmate 3, Crafter CS-310 TorchTrailblazer 302, 12RC, WC-2430A spoolgunSpectrum 2050Thermal Arc Plasma Welder PS-3000/WC-100B
Reply:Thanks guys. I cut it open Saturday and all is good. Two observations..... this tank had been used constantly in a car dealership for probably 12 or so years. There was so much residual crud in it I was amazed. Probably enough to fill a shoe box. This was a vertical tank and it was even stuck to the top dome with a big pile of it in the bottom also. A rusty, oil impregnated mess.I cut it with the plasma cutter right below the weld on the top dome. It came apart ok but I was surprised that there was a double wall at that point. Looks like the dome pressed into the cylindrical part and then was welded. Hence the two thicknesses at that point. The plasma cutter only cut the 1st thickness (probably because I didn't expect it to be double thick and it looks like there was a slight air gap between the two thicknesses at the point I cut it. But it popped right out for me. Oh yeah, the heated up residual oil stunk something fierce.I guess the point of this for anyone else is to consider cutting it about 3/4" away from the weld and you would only have the one thickness there.I'll post up what I made (yard art) in another thread in a few days. Have to get it painted up first.
Reply:Hey Dave,Did you do the CO routine?
Reply:This is the place we learn the advantage of drilling a hole before making the cut.The overlapped design is relatively common in tank construction as it eliminates a lot of problems during fitup and welding.Appreciation Gains You Recognition-
Reply:Franz, yep, sounds logical. Cutter, no purge, just 'went for it' I had figured just cutting it would be safe but it never hurts to ask either. I'm always willing to learn. I still stayed away from the open holes when cutting. Didn't want to see a flame come shooting out with me standing in front of it. All was well though.
Reply:See 'ladybug yard art' in the projects/pictures forum for the result.
Reply:Nothing like resurrecting a 9 year old thread, eh??  But I have this question too, but different sort of. I have a small contractors-style compressor I'd like to salvage the tank from and convert into a small wood stove/heater. Approx. 11" dia. x 24" long. Having read about all the dangers of welding and cutting on tanks, I'm hesitant to do it. I plan to use a metal-cutting blade in my jigsaw to cut a small door and chimney hole as well.Even though it's only held air, I'm wondering if this is safe to do. There are other small holes in it already from hoses, pressure gages, etc. I'll probably slosh some soapy water around inside first. My concern is weather the smoke from cutting with the jigsaw can ignite inside the tank and exploding.  Anyone who's done that trick of lighting the smoke stream from an extinguished match knows that smoke can ignite!Any advice is welcome. If this had held anything flammable, I definitely wouldn't even bother with this project, but I don't want to ignorantly continue if this is still a bad idea!Thanks guys, and happy 2013!Mark
Reply:Go for it. About the only caveat I'd offer is if you were cutting the tank apart with oxy/acetylene. In that case, any unburnt fuel MIGHT accumulate and cause problems.Lincoln PrecisionTig 275Miller 251Miller DialArc 250Bridgeport millHossfeld bender & diesLogan shaperJet 14 X 40 latheSouth Bend 9" 'C'Hypertherm 900Ellis 3000 band saw21"Royersford ExcelsiorTwo shops, still too many tools.