welding propane tank

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I'm sure this has come up a zillion times, but I'd like some input here. I've welding on many tanks in chemical plants. I always had the luxury of safety inspectors, the means to flush, inert gases oxygen testers etc.I'm getting an older, (taken out of commission) 500 gallon propane tank. I'd like to weld some 1 1/4 couplings on the top. This will be for a holding storage tank on a hydronic wood boiler system. Maximum psi. will be 30. Pressure isn't the problem. Without purging with argon, whats the safest way to do this. I'm thinking flushing out with water, then refilling to as high to the weld area, open all ports and weld.Any other thoughts?'
Reply:I've seen guys around here do it quite a bit.  I don't really know if it's safe though.  It would be nice to know if the propane is able to disolve in water.  Some gasses do.  My compressor is built with a propane tank as the resivoir.  I bought it that way, and didn't do the welding on it.Call your local propane supplier, and ask them.  They might give ya a straight answer, or maybe not.  Might be a liability thing.I picked up some old natural gas tanks that were mounted on a truck.  I've been wanting to do the same thing, but I'm a little afraid to, just like you.You only get one shot at this sort of thing.
Reply:what I have done in the past is empty tank remove any valving and let sit with opening facing down over night. then and hour or so befor aI weld place air line in tank and let blow for as long as possible. so far so good bigger the tank the longer I wait lol
Reply:Makes sense.  I guess propane is heavier than air, and will settle.  Has to keep you REALLY awake when you strike the first arc.  Don't wann be readin' about ya in the obits.
Reply:I spent many years as an oilfield welder and we weld on stuff all the time that is subject to going boom. NO MATTER WHAT YOU DO there is still always the possibility of an explosion. I've seen guys with 20+ years of experience get blown up or burned to death. A few of them they have never been able to determine what went wrong. Even the safety guys split after they call it safe. When they I do I just follow along, lol. They always want to know why and I always say if it's safe why did YOU leave? BE VERY CAREFUL. It could mean your life as you well know based on your experience. Myself I would just buy or build a tank, but that's just me.The difference between art and craft is the quality of the workmanship. I am an artist.
Reply:Originally Posted by Jolly RogerI spent many years as an oilfield welder and we weld on stuff all the time that is subject to going boom. NO MATTER WHAT YOU DO there is still always the possibility of an explosion. I've seen guys with 20+ years of experience get blown up or burned to death. A few of them they have never been able to determine what went wrong. Even the safety guys split after they call it safe. When they I do I just follow along, lol. They always want to know why and I always say if it's safe why did YOU leave? BE VERY CAREFUL. It could mean your life as you well know based on your experience. Myself I would just buy or build a tank, but that's just me.
Reply:I'd like to pass on doing the welds but I'd really like to get my storage project going. It is spooky though.
Reply:I'm sure this has come up a zillion times, but I'd like some input here.-and myself and others have posted comments on tank welding safety, repeatedly.I've welding on many tanks in chemical plants.I always had the luxury of safety inspectors, the means to flush, inert gases oxygen testers etc.--??But now, you don't wish to follow known, safe procedures, to save lots of money?I'm getting an older, (taken out of commission) 500 gallon propane tank. I'd like to weld some 1 1/4 couplings on the top. This will be for a holding storage tank on a hydronic wood boiler system. Maximum psi. will be 30. Pressure isn't the problem. Without purging with argon, whats the safest way to do this. I'm thinking flushing out with water, then refilling to as high to the weld area, open all ports and weld.-Presumably this tank is condemned due to corrosion and/or age. Any liquid propane residue, etc., will float on top of the hydraulic water bomb--you've just created. Plus whatever propane may come out of the tank shell interior from the heat of welding---all of this in a very small air space--that you created---so theLEL can go crazy--fast....or you're unlucky enough to get ignition on the floating sheen.Any other thoughts?-I'd darn well have a LEL meter---for initial testing, and purge monitoring--at the minimum;if you cannot or will not use O2 meter.-A nitrogen purge for this would suffice. Argon isn't necessary. You're looking at500 gallons = 67 cubic feet67 CF x 5 = 335 minimum CF to possibly bring O2 to 0%using a purge plan and design for this specific job, which you should be ableto do--from your cited experience.(O2 is what makes things burn and go BANG---as a few folks understand--most don't. Most never had basic chemistry. )So, to cut to the quick--(2) 300 CF bottles of Nitro---would suffice. Maybe $140 at the LWS. (Closed casket funerals cost more than that, last time I checked.)Dependent on LEL---after welding--you may need to pressure test with Nitro--Air pressure testing with LEL reading red--can cause, big time explosions--just byitself.Indubidoubly, you'll get 20 other replies, giving you the answers you wish to hear, rather than my response. It's just like Clint Eastwood asks, 'Do you feel-LUCKY?'I'm 'lucky'....done a good 1500 tanks of all manner and variety.Last edited by dave powelson; 08-29-2008 at 08:13 PM.Reason: added commentBlackbird
Reply:Blackbird, you scared the Hell out of me.  I'M DAMN GRATEFUL.Those old tanks I got weren't a bargain.  They're goin' to the dump.Been clutterin' up the yard for 5 years.  Be good to see 'em goTHANKS
Reply:Originally Posted by farmersammBlackbird, you scared the Hell out of me.  I'M DAMN GRATEFUL.Those old tanks I got weren't a bargain.  They're goin' to the dump.Been clutterin' up the yard for 5 years.  Be good to see 'em goTHANKS
Reply:Better listen to Blackbird on the tanks to be safe.I have been around welding on natural gas main for 27 years and it is different than welding on a tank that had propane in it.Anything without 100% natural gas in it should not be welded without caution and specific procedures.Propane I would presume should be the same idea with different procedures. .Propane is the wrong product for me so I am not familiar with their welding and purging.pro-level dumpster diver                                     Hobart 125EZ
Reply:"A nitrogen purge for this would suffice. Argon isn't necessary. You're looking at500 gallons = 67 cubic feet67 CF x 5 = 335 minimum CF to possibly bring O2 to 0%"If I fill the 500 gallon tank up with 499 gallons of water, after a flush or two. Then remove any valves, plugs, on the top of the tank, why wouldn't the top shell be safe to burn and weld?
Reply:Originally Posted by chuck172"A nitrogen purge for this would suffice. Argon isn't necessary. You're looking at500 gallons = 67 cubic feet67 CF x 5 = 335 minimum CF to possibly bring O2 to 0%"If I fill the 500 gallon tank up with 499 gallons of water, after a flush or two. Then remove any valves, plugs, on the top of the tank, why wouldn't the top shell be safe to burn and weld?