Smokin' Coke Forge Posted March 12, 2011 Share Posted March 12, 2011 After a long winter of tool making and doing demo's at a local indoor forge/museum, I'm now finally ready to install my side draft chimney on my outdoor forge. One thing that I'm struggling with, though. I've probably read every post on side draft chimney construction on this site and on Metal Artist Forum, as well as on Avilfire, but there hasn't been one mention of whether it is safe to use galvanized pipe for the flue. Nearly every article recommends contacting a local HVAC contractor for the pipe, yet the only smoke, spiral, or ductwork pipe I can find in either 10" or 12" diameter, or have made, is galvanized or stainless. Stainless is way beyond my budget, but what I know about galvanize poisoning and metal fume fever makes me think that stainless is my only answer. Does anyone out there know for sure, or have any experience with whether or not the supersucker box will get hot enough to cause the zinc coating on the lower section of chimney pipe to burn? I'd hate to wake up dead because I tried to stay safe by drawing the coal smoke away with a galvanized chimney. I know better than to burn up galvanized stock in the forge. I'd also rather be viewed as really stupid by asking if it's OK to use it for the chimney, than to be found dead because I didn't ask. Thanks for your honest input. - Jim Quote Link to comment Share on other sites More sharing options...
Glenn Posted March 12, 2011 Share Posted March 12, 2011 IForgeIron pushes safety first, including the warnings about galvanized metals, and fume fever, heavy metal poisoning, etc. The new blacksmith has no idea and no knowledge about some of the things that can do them harm. Therefore we need to both warn them and educate them as to what to look for, what to avoid, and how to use the different tools and metals safely. The common problem with galvanizing comes from it getting too hot and vaporizing the zinc, or the galvanizing being sanded or abraded with wire wheel or grinder and putting zinc dust into the air. When you breathe the vapor or dust it causes problems. I can not advise you as to your set up as each forge and chimney is different. Each blacksmith forges differently, one building a small fire generating a small amount of heat and the other building a large fire generating a large amount of heat. That amount of heat and the chimney configuration must be considered on an individual basis. I would NOT use galvanized on the supersucker box as it would get way too hot and vaporize the zinc. It should be constructed from bare plate or bare sheet steel, and not galvanized material. My side draft hood was constructed from plate steel and was about 2 feet wide by 3 feet tall. The hood itself got way too hot to have been constructed from galvanized material, as it would have vaporized the zinc. I would NOT use galvanized pipe for the first 6 feet of distance, based on MY hood (not a supersucker) and the way I use MY forge. Quote Link to comment Share on other sites More sharing options...
DanBrassaw Posted March 12, 2011 Share Posted March 12, 2011 I bought 6" snap-together black stove pipe, uncurled it, and snapped two together to end up with a 12" pipe. I had some mixed results with it STAYING snapped together though, I think because I didn't flatten it out enough. I just banded and screwed the trouble sections. Quote Link to comment Share on other sites More sharing options...
NRunals Posted March 12, 2011 Share Posted March 12, 2011 I used 12" pipe for my side draft, and like you all I could find was galvanized. I decided to strip the zinc off of the first 4 feet of pipe with a 50/50 muriatic acid/water mix. I put the mixture in a 5 gal bucket and soaked each piece for a few minuets. As for the stuff I left galvanized, being that it's 4 feet away from the fire I can put my bare hand on it at all times so that tells me that it is totally safe. The stripped pipe has such a shorter life than the galvanized though. It's been a little less than two years, and I may have to replace the two stripped pieces soon. Quote Link to comment Share on other sites More sharing options...
kevan Posted March 13, 2011 Share Posted March 13, 2011 I agree with the sentiments expressed about safety first. The 12 inch, 18 foot galvanised pipe on my super sucker DOES NOT get hot enough to affect the surface and cause the vapours that we all fear and even if it did the draught UP the stack is so strong that the only direction of toxins is up and out. The box into which the fire exhausts is NOT galvanised and should not be as this would definately get too hot. Err rather on the side of caution. On my forge,the stack is outside the walls of the building. My 2c worth. Quote Link to comment Share on other sites More sharing options...
Smokin' Coke Forge Posted March 16, 2011 Author Share Posted March 16, 2011 Thanks to all for your advice and suggestions. I've decided to stay away from the galvanized stuff altogether, and was able to find 6" Black pipe to piece together as recommended by DanBrassaw. That was a great idea that I hadn't considered before. I must say that I was intrigued by NRunals' suggestion to use muriatic acid and water to remove the galvanizing, as that suited my budget the best. My only hesitation was that if I didn't remove all or enough of the zinc, I'd still have some risk. Maybe I'm making too much it, but I'd rather be safe than sorry. Regardless, thanks to everyone for your advice. Hopefully the next person trying to figure out if galvanized chimneys are safe will land on this topic before spending as much time as I did trying to figure it out. Thanks again! - Jim Quote Link to comment Share on other sites More sharing options...
clinton Posted March 16, 2011 Share Posted March 16, 2011 look at the vent on your hot water heater (if you have a gas heater) gets pretty hot, I can not touch mine without a burn and I do not see any burning of the galvanized coating after years of use. I breath in way more zinc welding metal studs I can assure you Quote Link to comment Share on other sites More sharing options...
Jack Evers Posted March 16, 2011 Share Posted March 16, 2011 Zinc melts at 787 degrees F. It does not form zinc oxide until around 1600 F. If you can even briefly touch the pipe you're likely OK, but err on the safe side. Here's a link http://periodictable.com/ZincSafety.html Quote Link to comment Share on other sites More sharing options...
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