Outdoor wood boiler welding

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Hello, A buddy of mine wants me to do some welding on an outdoor wood boiler he is building. The welding I'll be doing is on new 1/4" plate and needs to be water tight (the reason I'm welding it not him). I'd like some opinions on what method to use? I have a 250 amp wire feed and a 300 amp stick/tig welder. My first thought is to wire feed it with .035 wire 80/20 shielding gas and setup fpr spray transfer. Or would dual shield wire be better? Or should I stick weld it with 7018?  I'd like to wire feed it so I'm not working on it for a week. I've welded things before that had to be water tight and always had to go back and fix pin hole leaks. So I'm looking for ideas for someone that been there done that.Thank you, Vince
Reply:uh....is this actually a boiler as in pressurized.  If so, I'd be reeeeeeeal careful with this.I don't want to sound like a smart a$$ (which I am sometimes) or a know-it-all (ain't happen'n) but welding boilers is for skilled professionals only....no amatuer projects here.I guessing that since you're asking what processes/procedures to use that you are not too experienced at this.  Again, please don't think I'm being a jerk but I'm just concerned.  Even a boiler under just a little pressure is a potential disaster if it fails.BTW...I'm just a novice welder but do have experience with power plants and medium to high pressure boilers.  I've seen the effort that goes into the design, engineering, manufacture and testing of boilers and believe me it's not a simple task.  I understand that your not building a 500MW unit but just the same....boilers can hurt you bad!Trick Question: What is your (or your friend's) criteria for sizing the pressure relief valve.Miller 211 w/ spool gunMiller Dynasty 200DXLongevity 60i IGBT plasmaO/A w/ crappy chinese torch/gaugesSouth Bend 10K latheGrizzly 4029 10x54 millGrizzly 7x12 hor bandsawangle grnders, bench grnder, bench belt sndr7.5 hp 80gal cmprsor
Reply:most outdoor wood boilers are open the the atmosphere and are not pressurized just for what you mentioned toooo dangerous
Reply:Our OWB is a 200 gallon open water loop as most are - they do not actually "boil" anything (unless they are over-fired) and most have a 2" pipe that vents to the atmosphere for pressure relief.The heating and cooling cycles might put weird stresses on the joints - I think the firebox often reaches fairly high temps in the 600degF or more range.  I have never seen any of the metal in mine change color and I have burned that sucker pretty hot.I would bet that there is nothing special about the firebox welds - full penetration with fresh 7018 sounds like a good idea to me (not sure I would know what a bad idea was if it bit me in the _____).You might try calling some folks that service the OWBs and see what they do for firebox repair.Hobart LX235Victor 250 Oxy-Acetylene Rig (welding and cutting)Bobcat 773F-350, 1999, 4x4, 16' 10K# trailerOutdoor Wood Burner - 10 cords/year
Reply:spray MIG needs 90/10 at a minimum. 80/20 won't workAs you're aware--every start and stop is a potential leak point.Miggin' then grinding out leak points and tiggin' them--can be timeeffective.Last edited by dave powelson; 03-16-2011 at 06:23 PM.Reason: additionBlackbird
Reply:I've done similar work on a BBQ smoker.  The smoker is a round tank over a rectangular firebox.There's a water tight plate between the cooking area and the firebox.  You can pour water in on top of this plate to steam the meat.  The contraption at the end will open/close to let in smoke.  The plate was welded up in sections since it's a compound curve.  This end is mostly flat, but the far end has about a 2 inch vee to it.  This lets the water drain out properly.The angle down the middle is an expansion joint of sorts.  I've seen other cookers where this is a solid plate and it will oilcan after it gets hot the first time.All of this was welded with 6010.  I haven't had any troubles with welds cracking when it gets hot/cold cycled.I would imagine your non-pressurized boiler would be built similarly (minus the doors, etc, etc).Dynasty200DX w/coolmate1MM210MM VintageESAB miniarc161ltsLincoln AC225Victor O/A, Smith AW1ACutmaster 81IR 2475N7.5FPRage3Jancy USA1019" SBAEAD-200LE
Reply:Sorry vpd66...my mistake.  I did some Googling and now see that this is a wood fired water heater.Ya gotta understand that here in Houston, Tx we don't know s&!t about circulating hot water heating systems, in-floor heating, baseboard heaters or any of that.  But if you come across a wood fired air-conditioner let me knowMiller 211 w/ spool gunMiller Dynasty 200DXLongevity 60i IGBT plasmaO/A w/ crappy chinese torch/gaugesSouth Bend 10K latheGrizzly 4029 10x54 millGrizzly 7x12 hor bandsawangle grnders, bench grnder, bench belt sndr7.5 hp 80gal cmprsor
Reply:No it isn't pressurized, it is open to the atomisphere. I've been a welder by trade for 20 years. I also welded a different OWB for another guy and he has had no problems and that was 5 years ago. I welded that one with wire feed .035 75/25 gas. I did have to go back and fix quite a few pin holes when I pressure tested it. This is why I'm asking if there is a better process for welding these. Also, I can get my welder into spray transfer with80/20.
Reply:Originally Posted by vpd66No it isn't pressurized, it is open to the atomisphere. I've been a welder by trade for 20 years. I also welded a different OWB for another guy and he has had no problems and that was 5 years ago. I welded that one with wire feed .035 75/25 gas. I did have to go back and fix quite a few pin holes when I pressure tested it. This is why I'm asking if there is a better process for welding these. Also, I can get my welder into spray transfer with80/20.
Reply:I have to disagree with you about spray transfer and 80/20. Where I work we spray transfer with 80/20 and this is why I switched at home. I was not bragging about being a welder for 20 years, just stating it so I quit getting replys like the first one thinking I'm some newby not knowing what I'm doing. This is why I hate forums. Where are all the guys that have welded on this OWBs. I know there have been many homebuilt units.