Welding an Air Compressor

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Hey guys...Welp, between my various adventures out on the farm, i picked up a 60 gallon air compressor. I restore old tractors, and decided that it would be really good for sandblasting, painting, etc. I bought it off of craigslist, and found out it needed a new pressure switch, as the old one leaked like crazy.Alright, $40 later, thats fixed. The problem was that the little line didn't fit the new switch.Its called an unloader valve, and somehow, i dont know how it works, but its purpose in life is to make sure that when the compressor starts, that the pump and motor can start easy, because, thanks to it, theres no compressed air built up in the cylinders. Not knowing anything about this, i just clamped it off, and moved on with life. It went boom at about 90 psi. It was a pretty impressive show, and scared the crap out of me. Not to self: NEVER clamp shut a compressor line. Bad idea. Anyway, i tried to make a new one with some stuff from the hardware store, and that diddnt work. It only made it to about 15 psi. Screw it, says I. I bought a plug from lowes, and screwed it in. This promptly blew this line out of the top of the tank.Probally shoulda seen that one coming. Anyway, now i need a new one. Instead of going around looking for parts for a 10 year old unit like this one, waiting on them, etc, i want to make one. I bought a used unloader valve off craigslist, and im pretty sure i can make that work.All that leaves left is this tube.It was just a copper tube before, but after the unloader line blew, i saw what a huge show and how much power that little thing let loose, and i got scared of what this big copper line could do, with twice the air, once this thing gets up to psi. I was accually planning on buying some 1/4 inch plate and welding up a cage on the top "shelf" of this compressor, so that if it blew, it would blow up, not out. But it went poof anyway.So, im thinking i could get some black iron pipe, screw it on the compressor tank, and into the pump, connect the angle with an elbow, and cut and weld the black pipe to size. I know it was copper for a reason, which is probally to help the heat disperse. but im not too worried, i dont mind a little hot air..Unless theres some glaring reason to not do this, which im missing, what kind of rod should i use?? Im new at this, and not very good with 6011, so im thinking 7018. Heres my plan:And heres the peice that broke, and bent:
Reply:Me thinks you may be out of your comfort zone."The man of great wealth owes a peculiar obligation to the State, because he derives special advantages from the mere existence of government."  Teddy RooseveltAmerican by birth, Union by choice!  Boilermakers # 60America is a Union.
Reply:why rethink the wheel ? just use the compression fittings and use a new piece of copper. same thing happend to me, but instead of all that drama. I just sweated in all my copper tubing. It will never get hot enough to blow out again.
Reply:If I think I know what you're talking about, it sounds like the pressure switchGo to any good electrical supply, and get a new one for around 20 bucks.  They have a low and high pressure adjustment.  The plumbing might not match, but that's just a matter of changing the plumbing"Any day above ground is a good day"http://www.farmersamm.com/
Reply:New copper line is fairly reasonable, and if you need easily bent line, ask for refrigerant line"Any day above ground is a good day"http://www.farmersamm.com/
Reply:I'd just go with the copper myself. Thats what I used to repair an old compressor I picked up cheap years ago. That line is either 1/2" copper tube or 5/8" tube/1/2" copper pipe. ( Copper tube is measured by OD, Pipe by ID, thats why the 5/8" tube is  also 1/2" pipe.)If not I can see 2 other options. First you can just get a HP hose fabed for this at a place that does hydraulic lines. You may have to get one end done in JIC and use a NPT/JIC adapter so you can tighten the line. We used to get these fabed all the time to connect compressors to hard line systems to eliminate the vibration between the compressor and the lines. Second option is even simpler. It's called a union. A union is a special pipe fitting that designed to do exactly what you are doing, connect threaded pipe between 2 fixed points. They are easy to get, HD and most places sell them as it's the only way to often make threaded connections in places. Be advised I don't know what pressure rating the pipe Home Depot sells is. It's primarily sold for Natural gas and water not pressurized air. Not all pipe and fittings are created equal. You've already seen what can happen if things go BANG, so I'd probably spend the extra cash and make sure if you go the pipe route you get quality pipe and fittings from a supply house that can take the pressure, especially if this is a 2 stage unit and can build 175 psi. I usually just pick up steel fittings at the hydraulic place for my air lines, since all their stuff is rated at 3000 psi + in steel fittings. The couple extra bucks is cheap insurance.Unless you really know what you are doing, I'd skip any plans to weld the pipe and just work with any of the 3 above options..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:I think you need to just stop jury-rigging your equipment before you kill yourself or someone else.  High pressure air in a large tank is not something to be disrespected.  Quit being cheap, take it to a compressor repair shop and have them make the necessary, proper, safe repairs to it.  It will be money very well spent in the long run.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:Dude, S - T - O - P !!!!!!!!!!!!!If you have to ask, then you should NOT weld things having to do with compressed air.Do NOT weld on the air tank.Do NOT weld any fittings.Do NOT weld any pipes.Do NOT weld -anything- that is part of the pressurized air system.You have already seen what happens when the pressure burst some parts.  And copper is usually quite malleable and will split but not fracture or send out shards of shrapnel.Where it was copper, replace with copper.  Use the correct/appropriate fittings.  Do not, repeat N-O-T , weld anything with air pressure in it.  You are not ready.If you aren't sure what you are doing, or know how to KNOW what you are doing, then STOP.  Pay to have it done right and safely.Because you already saw and experienced what happens when you don't do it right or safely.  The best laid schemes ... Gang oft agley ...
Reply:If you are going to do this yourself, read and consider moonrise's post. Then, take pictures that are clear and sized appropriately (600X400 or so) and show the general layout as well as each point of concern. Identifying the make and model will help, as well.I will guess that this will be simple, but it isn't clear from what you wrote and your diagram what the problem actually is. From the initial description, I would guess that the problem was NOT the pressure switch. Most of the less expensive units use the pressure control switch to unload the outlet from the pump, rather than using unloders built into the pump valves. If this is the case, then the most likely problem is the check valve at the tank that prevents the tank from leaking back into the line from the pump. If the check is bad, a) you will have a constant leak back to the unload valve, and b) you may be restricting the aitflow from the pump, and the pressure pulses are what blew the line. There are other possibilities, as well, but without pics, tough to tell.As a side note, check the safety valve (or better yet, replace it), as well as open up the tank (pull a big plug) and look inside. You are looking for excessive rust pitting at the bottom, oil deposits (deposits and vapors carried over may ignite in the tank... the tank isn't built for combustion). There have been a few threads over the last few years on inspecting this gear.  Your comment "this blew the line out of the top of the tank" gives me concern.
Reply:I think any advice I could offer would be undermining Darwinism in action.Please proceed!We want to see something like this in the signature line:Lincoln Ranger 250Miller Auto-Darkening Elite HelmetLincoln 100Lincoln MigMiller Spectrum 375Craftsman 8 galllon gas powered compressorLongevity 200amp Tig Welder LT-200D
Reply:Originally Posted by Stack of DimesI think any advice I could offer would be undermining Darwinism in action.Please proceed!