FieryFurnace Posted August 5, 2011 Share Posted August 5, 2011 Nine months after installing my forge, at least the first two sections of galvanized air duct pipe are shot. I mean, "poke your finger through it" shot. The pipe is the heaviest (24 gauge) galvanized air pipe I could buy and was recommended to me by smiths on here that I know are knowledgeable and have lots of experience. I am using the Hofi hood and it places the pipe 3 feet away from the fire at the nearest point. The lower five foot section of pipe is so rusted through it is just coming off in chunks and the second section is following suite. The top section still seems to be somewhat in tact but I'm not sure. The lower section of pipe gets too hot to touch when I'm pumping the blower pretty hard. I am using stoker coal so the flame gets pretty far back up in the hood. I'm not sure how to tell if the galvanization is burning but I'm not worried about any poisoning because the pipe is outside. I'm guessing it is a moisture/coal soot problem as apposed to too much heat. If it was heat then just the lower section of pipe would be shot. I'm currently working on taking the bad pipe down and putting up a new fabricated pipe made from sheet steel that is about 16 gauge. (Still working on how to roll that stuff! LOL) I'm also going to lower the height of the rain cap to try to help keep moisture out. Anyway, thoughts and theories on why this stuff went bad so quick would be appreciated, as well as prevention ideas so I don't end up spending $80 every nine months to keep the forge hood up. Thanks! Quote Link to comment Share on other sites More sharing options...
Glenn Posted August 5, 2011 Share Posted August 5, 2011 If the galvanized pipe gets too hot it will look frosted. If your exhausting that much heat up the chimney, you may want to rethink your set up. Larger diameter chimney, larger fire, different shape fire pot, etc. Quote Link to comment Share on other sites More sharing options...
jake pogrebinsky Posted August 5, 2011 Share Posted August 5, 2011 Usual enemy of chimney parts is "creosote",folk term for all the combustion byproducts.Acidity is what did your pipe in,in this case,i'd guess made worse by sulfur in the coal. 24ga.is paper thin(terrible what they sell,nowadays),plus,it probably had a sticker on it saying that it's not to be used as chimney. Plain steel,no zink,may do better.I hope so,anyway,as the composition of your coal is not that easy to change. Best of luck,hope that un-galv.pipe works better. Quote Link to comment Share on other sites More sharing options...
Harley Posted August 5, 2011 Share Posted August 5, 2011 I got tired of having to replace pipe every so often so I contacted a chimney sweep who also does relining of chimneys. He told me the best pipe for what I do is made from 316L stainless. I replaced all my pipe with 10 inch 316L stainless three yrs ago and it looks as new as it did the day I installed it . costly though . four - four sections cost me $500.00 but it looks to be paying for itself in the long run. I have a coal stove in the shop for heat and will be buying 6 inch 316L for that also as I plan to be smithing until the day I can no longer pick up a hammer. Mark A.K.A. Harley Quote Link to comment Share on other sites More sharing options...
John B Posted August 5, 2011 Share Posted August 5, 2011 I'm currently working on taking the bad pipe down and putting up a new fabricated pipe made from sheet steel that is about 16 gauge. (Still working on how to roll that stuff! LOL) I'm also going to lower the height of the rain cap to try to help keep moisture out. Hi Dave, The chimney does not have to be round to be effective, and put a drain port in the base for any accumulated water to drain out Quote Link to comment Share on other sites More sharing options...
John McPherson Posted August 5, 2011 Share Posted August 5, 2011 Culvert pipe, the type that goes under a driveway, is relatively cheap, heavy wall, and rigid. They have used them at the NCABANA state fair site for years. Quote Link to comment Share on other sites More sharing options...
Old N Rusty Posted August 5, 2011 Share Posted August 5, 2011 I use a 20' 12" sch.10 316 S.S stack suspended straight up through the roof and directly over the firepot. It extends 6' up from the roof and is well above the ridge line. This stack is always drawing a breeze, and with a good fire flame tips go up into the stack 12" above the fire, and dust is being vaacumed from the air. Straight up seems to me to be the best way , I have had a lot of galvanized pipe and side stack in steel fail and fall. Rusty is all consuming and galvanize does not last. So is a permanent solution with 316 stains less steel really that much more costly to the professional shop? Oh I got another 20 footer for sale $ 400.00 you haul. Quote Link to comment Share on other sites More sharing options...
FieryFurnace Posted August 5, 2011 Author Share Posted August 5, 2011 Ok well the galvanizing hasn't burned off.....at least no frosty appearence. What temperature does the galv burn off at? Stainless is the duh solution, and I can get sheets of it at my steel yard......but I'd have to go in after hours! LOL Stainless is the goal, but for now it is too expensive. The culvert isn't a bad idea and it definately is rigid. It would be a whole lot easier than bending that stuff I got. I think I can get 20' of that for like $150 or a bit more. The only problem I see is installing the stuff. I imagine the thing would be pretty hefty and I don't own a crane or a tractor with a front end loader. Mr. John, I had originally planned on going with a square flue before someone suggested the galvinized stuff I'm using now. I mean this 16 gauge stuff I have now cost me $25.00 for a 4'x10' sheet. However, either I have to weld all four corners or I have to pay the welding shop to bend it. Our welding shop is very pricey and not very friendly. My hofi hood has the ash door and is angled slightly down to the outside to alllow water draining. Quote Link to comment Share on other sites More sharing options...
KYBOY Posted August 5, 2011 Share Posted August 5, 2011 Dave do you have a rain cap over your chimney? Quote Link to comment Share on other sites More sharing options...
Francis Trez Cole Posted August 5, 2011 Share Posted August 5, 2011 I just took down a 35' chimney 24' dia 13 gauge. it had been on the building for 50 years good stuff. The rust that is why I made a brick chimney (used bricks free) and about 12 bags of mix including the footer. $3.50 a bag for concrete. Quote Link to comment Share on other sites More sharing options...
FieryFurnace Posted August 5, 2011 Author Share Posted August 5, 2011 KY BOY, Sure do, but I am going to lower it down a bit to offer a bit more protection. Kind of a shot in the dark but it can't hurt. Brick sure does look good and I've never heard of one rusting away but I'm guessing it's a pain in the neck to move! LOL I'm still in the "shop development" stage so I want to keep mobility for rearanging, an option. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted August 5, 2011 Share Posted August 5, 2011 Check out the used market if possible for stainless---demolition/architectural salvage, restore, etc Also places that do commercial kitchens to see if you can get a tear out. I picked up some SS pipe at the Restore, about 4' long for US$10 a piece that I will be using to do the lower section of the chimney and then switching to the $4 per 10' spiral seamed vent pipe for the upper section. Quote Link to comment Share on other sites More sharing options...
KYBOY Posted August 5, 2011 Share Posted August 5, 2011 Sorry Dave, I know it sounded like a dumb question I had problems with my chimney rusting out because my rain cap was flopping over allowing it to rain down my chimney..That and I used old chimney pipe that I found Im gonna replace my chimney as well, before winter anyway KY BOY, Sure do, but I am going to lower it down a bit to offer a bit more protection. Kind of a shot in the dark but it can't hurt. Brick sure does look good and I've never heard of one rusting away but I'm guessing it's a pain in the neck to move! LOL I'm still in the "shop development" stage so I want to keep mobility for rearanging, an option. Quote Link to comment Share on other sites More sharing options...
FieryFurnace Posted August 5, 2011 Author Share Posted August 5, 2011 I think most of the members on here would agree with my theory that Mr. Thomas Powers is blessed by the "salvage angle." No offence Mr. Thomas, I know you must always be searching and working hard to find the stuff you do. KYBOY: Order twice as much as you need and donate! ;) Quote Link to comment Share on other sites More sharing options...
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