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Hi all!, I am in the process of making a wood burning pool heater and am working on designing a heat exchanger. This heat exchanger would be exposed to high heat ( that is it's purpose) say about 500-800 ?degrees I am toying with the idea of using copper as my heat exchanger which would travel in an up and down fashion in the woodstove, with the pipes being close together; closer the better, can fit more pipe in an given area.I realize soldering the copper will not be good as the solder prob will melt in the woodstove, leaking water so I was thinking of welding the copper.Will brazing copper hold up in the heat? I am not really sure what brazing is, or how it is done.I am also considering using some other metal, but this was my first thought.I am aware copper gives off toxic fumes when welded ( or mig'ed anyway), so that is a concern. Hoping you all would help with welding ideas or other ideas!Thanks so muchMatt; ................not so much a MIG newbie now....
Reply:It can be tigged...http://www.weldingweb.com/vbb/showthread...ghlight=copperPulser has done this......zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Unfortuatnely I do not have a TIG, only a mig, however did see this....trwatks WeldingWeb Apprentice Join Date: Jan 2007Location: Sarasota Fl.Posts: 19 Re: TIG Copper --------------------------------------------------------------------------------trwatks WeldingWeb Apprentice "..............I have also used everdur orsilicon bronze (98% copper 2% silicon ) with tig and mig to weld copperwith great results." So this gives me hope, anyone else with experience with this?ThanksMatt
Reply:Why not just use a coil of tube?
Reply:If the pipes are full of water, the solder can not melt. It'll never get over 212 or so depending on if you have any pressure in the system. Phos bronze type with a tig torch should work. Its sort of like silver solder which is another option for you.David Real world weldin. When I grow up I want to be a tig weldor.
Reply:Originally Posted by TSORWhy not just use a coil of tube?
Reply:Originally Posted by David RIf the pipes are full of water, the solder can not melt. It'll never get over 212 or so depending on if you have any pressure in the system. David
Reply:are there any pool/spa places where you live? If you can get a hold of a ready built gas unit that died, that'd be an option as well. Molest the heat exchanger of it, or build a firebox to burn wood in it. Try local hotels, heating/cooling places. Most hydronic boilers are a copper tube with fin construction.
Reply:It's not gonna be much cheaper to piece together 100' of copper pipe... .Miller EconotigCutmaster 38Yes ma'am, that IS a screwdriver in my pocket!
Reply:Do you have an oxy-acet. set up? If you do go by an HVAC supply house and get some brazing rods, the temps will not get high enough to melt the filler material.
Reply:Originally Posted by Mr mattThat is a very interesting thought! I was not sure if the heat could transfer fast enough to keep the solder intact, I guess to say it the other way - I was not sure if the water could cool down the solder fast enough.Matt
Reply:Originally Posted by Mr mattThat is a very interesting thought! I was not sure if the heat could transfer fast enough to keep the solder intact, I guess to say it the other way - I was not sure if the water could cool down the solder fast enoughNot really sure what you mean, sorry. I do not have a TIG only a MIG - can I use silver solder with a MIG.I bet I am misunderstanding this THanksMatt
Reply:I'm pretty sure that you can get silicon bronze wire for GMAW.Miller EconotigCutmaster 38Yes ma'am, that IS a screwdriver in my pocket!
Reply:You could use 5/16" acr tubing and build a manifold to supply water and return water and insteadof having a bunch of welds you only have a few in your manifold system which could very easily built outside of the heating chamber and not exposed to teh heat of the fire.
Reply:I have never done it but you can Mig Cu with Silicon Bronze wire and 100% Argon. Dare say Oxy would be cheaper though.A good guess is better than a bad measurement
Reply:Solder WILL melt with water in the pipe. Just go into a burned house and look at the copper plumbing. Just use a coil of sopper or SS.
Reply:What are you heat exchaing? 800 degrees is pretty hot for a brazed joint, but... even though furnace temps or whatever may exceed 800 degrees, the tube temperatures may be significantly less depending on the fluid on the other side. Brazing is almost always the way to go with copper. Most heat exchangers I have come across that aren't swaged are brazed.
Reply:I had the same "plan". WAS going to build my own hot water "boiler" for home heat. Anyway, I considered all the same things you are thinking about and finally I bought a 60' roll of 1 1/8 copper tube Type M on Ebay. I think I paid about 170.00. Anyway, I was just looking at it sitting there... The main issue there is how to bend it.If you have ever tried to solder a fitting with even a DROP of water in the pipe you just can't do it!! Now maybe at 2000 degrees or something.... I would think the solder would last quite awhile in your application. I think sometimes stainless is used also. You could definitely weld that but I have heard it is hard to do!Mike
Reply:Schd 80 black iron pipe for boilers. Be very careful with this thing!I work with boilers everyday and your plan on heat exchanger sounds to incomplete. Or should I say more like a boiler to me, just thinking of your safety.300 degrees can produce steam in a moving system. And my boilers at 450 t0 550 degrees put out 90 PSI on 4" steam line. Be-carefulMiller Thunderbolt 225Millermatic 130 XPLincoln HD 100 Forney C-5bt Arc welderPlasma Cutter Gianteach Cut40ACent Machinery Bandsaw Cent Machinery 16Speed Drill PressChicago Electric 130amp tig/90 ArcHobart 190 Mig spoolgun ready
Reply:Originally Posted by STwelderSchd 80 black iron pipe for boilers. Be very careful with this thing!I work with boilers everyday and your plan on heat exchanger sounds to incomplete. Or should I say more like a boiler to me, just thinking of your safety.300 degrees can produce steam in a moving system. And my boilers at 450 t0 550 degrees put out 90 PSI on 4" steam line. Be-careful
Reply:Originally Posted by turboblownSolder WILL melt with water in the pipe. Just go into a burned house and look at the copper plumbing. Just use a coil of sopper or SS.
Reply:I have to agree with some of the guys that you're probably not going to melt out the solder with water in the pipe. I've plumbed a ton of copper and have always had to either boil out the water or stuff bread down the pipe to create a void to allow the copper to heat up enough. The fancy guys have freezers that freeze the water in the pipe and allows them to cut it and drain off the water before soldering.Here's a thought, I have a defunct power washer that has a diesel fired flame thrower (basically) inside it that super heats water for high pressure spray washing. The coils in that thing are steal and not copper and that should work for you as well. They are coiled around the inside of the chamber and transfer heat quite well. They could be mig welded on the ends. If you can find an old broken power pressure washer that had a heater you could scavenge coils from or pickup cheap you might have a workable solution.You need to make sure that you have some sort of pressure relief valve otherwise your building a bomb. I know, because the unloader valve on my unit failed to unload and fortunately only blew the rubber feeder hose but it could have been worse and blew out one of the coils. Then you would have shrapnel everywhere. Anyway, you might be able to scrounge something from a pressure washer that is more reasonably priced that will meet your objectives.Michaelp.s. funny story on my spray rig. I was jacking with the igniter for the diesel flame unit with my best friend standing up on the truck. He was next to the exhaust port on the blower. I asked him if raw diesel was coming out of the exhaust port becuase I didn't know if I had a spark problem or the fuel atomizer was broken. The next thing I know he leans over and sticks his face into the exhaust to take a whiff at the same time the igniter fired. It shot a fireball (along with insullation from inside the tank) straight up over the top of his face. The good thing was he had his eyes closed when he leaned over the exhaust port, the bad thing was he had no hair on his face or the top of his head in a matter 2 seconds. Millermatic 25115" Rockwell Drill Press10" Logan Lathe5hp - 2-stage 80 Gallon CompressorHome Made Sand / Soda Blaster
Reply:Things you might want to know, in no particular order:1) copper (K, which is the heaviest wall) would be ok, but expensive. Steel is cheaper, even if the copper is free: sell the copper, buy steel and a six pack with the money.2) If you insist on using copper, DO NOT use soft solder in the firing zone. Use silver braze (any of the assortment available that the HVAC guys use) Soft solder WILL fail. Thermal cycling is a killer for it, if a steam pocket forms, it will fail almost immediately, and it has ow strength even at 225F. Best to form a coil and have joints outside the zone exposed to the fire3) A safety valve is recommended. The volume of water in the heat exchanger is small so the risk is small, as the energy that can be stored is small, but the risk is still there. The valve should be at the INLET end. If there is a blockage, the pump can, potentially, overpressurize the coil, and the safety at the inlet prevents this. The coil should really never be significantly above atmospheric pressure.4) you want a way to kill firing if there is an overheat: for wood fired, that is likely to be some form of diverter for the combustion products. For oil or gas, it would be to cut off fuel, coal would be choke off air or dump the fire. This should be automatic, if possible.5) CHeck the laws in your jurisdiction: if may not be permissable to build this yourself no matter how small. More likely, there is a maximum size before license and permits are needed. This will be based (in most places) on heating surface (surface exposed to the fire on one side, pressure/cooling fluid on the other), air admission or grate area, fuel consumption capacity or burner BTU/Hr rating, design pressure, and several other possible factors. In many places, if the tubing is less than a certain diameter (6"ID is common) and the TOTAL VOLUME for heating and retaining the heated fluid is less than some size (Some places this is less than 1/2 cubic foot, others more than 1.5 cubic foot), the boiler is exempt from registration and license, and may be exempt from construction code requirements (or may not be).This one matters a lot if you have insurance on your house: Violate the legal codes, the insurance won't pay if there is a fire or injury involving it.The Illinois law is fairly typical ( http://www.state.il.us/osfm/Boilers/BoilerWebpage.pdf -- this was handy as I dug it up earlier)... For what you are doing, see sec 5(b)(5) (page 8), where the exemption from inspection and license is based on no stem generated, tube size 3/4NPS or less (or 1"OD tube), total volume less than 6gal, no drums, headers, or steam spaces, and temp of the water doesn't exceed 350 degrees (Note: 350 degree water corresponds to a pressure in excess of approx 150PSIG). You arn't planning on pressure above atmospheric. You don't want steam. Does the laws apply? Depends on the jurisdiction. The potential to build pressure is there if the tubing plugs. Would I much worry about it? Personally, no, but that is me.6) positive, continuous flow is required to keep the tubing full of water. I would also suggest an open tempering tank: water from the pool goes into the tempering tank, and the water to be heated comes out of it and returns to it. This will greatly reduce the risk of a hot spot in the pool where someone can get hurt. Why an open tank? It provides a clear boundry limiting the portion that could become pressure retaining if the tubing plugs up. Also, NO VALVES that could block flow. If it was me (I would really go solar, but just for the sake of argument...), I'd go with a few 20 foot lengths of 1/2" sch80 steel pipe (black pipe, NOT galvanized), which is about 1.0 gallon for 80 feet. Threaded steel (forged steel, not cast) fittings to make the joints. Figuring a 2' diameter for the coil, 4 lengths will give ten or eleven turns (about 70feet of pipe) and a bit to get out of the firebox. 1/2" pipe is inexpensive and bends easily. Size the coil so that it is near the walls of the firebox above the typical fuel height.... the radiant heat is your big win here... it won't be dead efficient. You can let the pipe soot up a little, but brush off any heavy buildup.
Reply:As long as the water in the pipe stays as water you are all set, the solder will NOT melt. But I would recommend brazing it anyways.To prove the point:Make a camp fire as hot as you can with a good bed of coals. now fill a PAPER cup with water and an egg...Place in fire on coals.Stand back and watch it boil.Remove cup and egg and enjoy...The cup can not burn since the water keeps its temperature below flash point.Me!
Reply:ME!You said it! Done it my self.David Real world weldin. When I grow up I want to be a tig weldor.Personally I would use stainless steel tubing ... it's better suited to your purpose I think. It might even be somewhat cheaper than copper and will definately last longer than copper. It should be far easier to weld as well. The chlorine in the pool water is going to react with the copper and the stronger the chlorine solution in the pool the faster the tubing will deteriorate.We don't use any copper on bleach or chemical lines in the laundries it gets eaten up by chemicals such as chlorine.Washman
Reply:Originally Posted by Me!As long as the water in the pipe stays as water you are all set, the solder will NOT melt. But I would recommend brazing it anyways.
Reply:That's why we said to braze it.
Reply:Originally Posted by WashmanPersonally I would use stainless steel tubing ... it's better suited to your purpose I think. It might even be somewhat cheaper than copper and will definately last longer than copper. It should be far easier to weld as well. The chlorine in the pool water is going to react with the copper and the stronger the chlorine solution in the pool the faster the tubing will deteriorate.We don't use any copper on bleach or chemical lines in the laundries it gets eaten up by chemicals such as chlorine.Washman
Reply:Two cents more ....Every compatability chart and reference I can find on the web says copper is not reccomended with Chlorine water solution.Some say "Not recommended" and most say "Extreme corrision potential"Washman
Reply:You can mig it. I'd reccomend RN67 mig wire, and 75% argon/25% helium. You can even spray arc it if you got enough heat.
Reply:stainless would be better here is whyhttp://jchemed.chem.wisc.edu/JCEsoft...CLCU/PAGE1.HTMChuckASME Pressure Vessel welder
Reply:Edit: redundantLast edited by rat4spd; 10-06-2007 at 10:30 PM. |
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发表于 2021-9-1 00:55:36