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#1 CTBlacksmith

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Posted 20 January 2010 - 12:53 AM

Where do you guys get your chimney pipe for your forges? i recently built a hood for my forge and i need to get a larger pipe to vent it. i was thinking about getting 10 or 12 inch pipe but i cant find any. And would it be better to just build a side draft chimney instead of having a hood? Thanks in advance for any response.
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#2 Bad Creek Blacksmith

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Posted 20 January 2010 - 05:28 AM

I went to a Heating and Air condition company and bought single wall duct work.
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#3 unkle spike

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Posted 20 January 2010 - 06:48 AM

I got 12" at Home Depot when I did mine a few years back....and I have an overhead hood, and if I had it to do again I would build a side draft, I have used them, and they work much better.
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#4 ThomasPowers

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Posted 20 January 2010 - 12:05 PM

The pipe sold flat with a side seam you lock can be put together with two pieces to make larger pipe diameters.

I bought 10" spiral seam ductwork pipe at a ReStore for $4 for a 10' length. Wish I had bought it all then as now they wanted $25 for a 4' length.

I see a lot of this sort of ductwork thrown in construction dumpsters during commercial remodeling---you might check with an HVAC company and see if they have any leads on discards...My problem is I seldom have the time when I am in the big city to track down permission to raid the dumpsters.
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#5 clinton

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Posted 20 January 2010 - 12:31 PM

like thomas said find sheet metal workers they throw away tons of this stuff, if you catch the guys at break time you can score big time, try at noon or 10:00 break
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#6 CTBlacksmith

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Posted 20 January 2010 - 01:27 PM

I work with my dad framing houses in the summer so maybe i can find some then. thanks
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#7 Dave Leppo

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Posted 21 January 2010 - 06:41 AM

I recently put up a 12" culvert pipe, 20' long - bought new for this purpose. This smoke stack was not as cheap as the round ductwork it replaced, but will likely last 10 times as long. This is a side draft setup similar to Hoffi's blueprint, but using the 12" vewrtical pipe and a 14" horizontal pipe.
:)

#8 reefera4m

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Posted 21 January 2010 - 10:55 PM

WOW! I'd be VERY Careful with some of these suggestions. A coal forge with a blower puts out a LOT of heat, especially when using the blower. While I only use my coal forge outside, I do have a wood stove in my shop. Wood stoves run cooler than coal stoves and yet the building code require at least a double-walled insulated chimney pipe (sometimes triple) where ever the pipe passes through ceilings, walls or roofs. Below the ceiling you can use single wall - it radiates the heat back into the room but there is a requirement for a 'thimble' a pass-through piece at the ceiling. Not following the code will invalidate your insurance, put you and your shop at risk and may cost a lot more in the long run.

Double wall chimmney pipe is Expensive! The best place to find it is Craigslist. You can save 50% or more if you're lucky or persistent. I saved more than 50%!

Also, I would recommend two things when building your chimney; 1) minimum 8" diameter pipe and 2) the chimney extend a minimum of 4' above the highest point of the roof (or what the code calls for, whichever is greater). The taller the chimney the better it will draw - 12' being the shortest recommended. My shop has a 9' ceiling, then a 7' loft. I used single wall to the ceiling and 12 feet of insulated doublewall chimney pipe through the ceiling, loft and roof. It draws great - no smoke at all in the shop - ever! And no worries about starting the ceiling or roof on fire. However, if you were to touch the single wall chimney pipe you'd get 3rd degree burns in a heartbeat!

Also, you need to keep the forge at least 36" away from any combustible wall (sheetrock is combustible, therefore 36" clearance minimum)
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#9 ThomasPowers

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Posted 22 January 2010 - 11:31 AM

I have NEVER seen a coal forge chimney get as hot as yours is running---they tend to be much cooler than woodstoves as there is a lot of room air drawn into the stack as well as the hot gasses; where wood and coal stoves all the air in the exhaust stack has gone through the stove.

How is yours designed that it gets so hot?
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#10 petere76

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Posted 22 January 2010 - 12:24 PM

Most of the coal forges I have seen dont heat up the ducting or the hood that much. There is obviously some heat in the uptake or the system would not effectively draft. Most of your heat is localized to the coal mass. There is a certain radiant factor next to the foge which you can feel but it's not that much.

Side draft hoods seem to work the best in my part of the world. The overhead hood arrangement works well in open buildings but it gets smokey on startup and after a day of breathing the fumes its hard on the operator. Use a min of 10 inch pipe. Going through the wall or the overhead check your building codes as they may require double wall inuslted piping and a 2 in clearance to combustable materials. This is a fairly standard code. If you are going to invest the time and money in the shop, might as well do it right.

Peter

#11 reefera4m

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Posted 26 January 2010 - 01:03 AM

Next time you see a forge at welding or even forging with a chimney, put you hand on the chimney. I you get burned Posted Image use at least double-walled insulated pipe through all ceilings and roofs. It doesn't take all that much heat to start a fire in very dry wood.

I've seen a number of forges with chimneys, the last one in W. Wa at a blacksmith school. The chimeny pipes throught the ceiling and roofs were double-walled.

If you don't get burned, ignore this advicePosted Image, and the heck with the code.
'No arsenal, or no weapon in the arsenals of the world, is as formidable as the will and moral courage of free men and women.'- Ronald Reagan

#12 unkle spike

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Posted 26 January 2010 - 07:03 AM

I have a charcoal grill thermometer in my overhead hood at eye level, I see it around 400F sometimes, most times it is around 300 degrees during active forging.
Jeff Phillips

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#13 ThomasPowers

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Posted 26 January 2010 - 11:23 AM

What is this "wood" you speak of and why does it pertain to your smithy? OK it's a poor joke; but my smithy's original part had *no* wood in it's construction whatsoever and the extension I am working on has only 4 pieces---telephone poles as uprights---and I am thinking of sheathing them with sheetmetal.

If your "code" treats forge chimneys the same as woodstove chimneys then the code needs to be modified; but you better follow it in the meantime to assuage the insurance companies.

Thomas
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#14 reefera4m

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Posted 27 January 2010 - 11:26 PM

What is this "wood" you speak of and why does it pertain to your smithy? OK it's a poor joke; but my smithy's original part had *no* wood in it's construction whatsoever and the extension I am working on has only 4 pieces---telephone poles as uprights---and I am thinking of sheathing them with sheetmetal.

If your "code" treats forge chimneys the same as woodstove chimneys then the code needs to be modified; but you better follow it in the meantime to assuage the insurance companies.

Thomas



Ceiling joists, roof rafters, plywood sheathing, anywhere the chimney passes through a ceiling or roof is at risk.

Creosote and carbon that builds up in a chimney pipe will ignite at 400 degrees under the right (or wrong) conditions, adding additional heat to the chimney pipe. If my shop wasn't worth much I wouldn't loose any sleep over it but........
'No arsenal, or no weapon in the arsenals of the world, is as formidable as the will and moral courage of free men and women.'- Ronald Reagan




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