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stupid questions about chimney


jrgpots
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Jed 

I dug out some homemade burners I used about 30 years ago. I used them as natural draft but they can be air powered with slight orvice change.

They work great as the 3 inch is large enough for the 1/2 inch pipe inside to still allow air around pipe.

The back view shows some spider nests as they have been sitting about 30 years in a shed

This gas pipe in is 1/2 inch on top

They are made from 3 inch pipe tees. I custom threaded the inlet gas pipe (easy you have all the pipe threading tools as I did. These also neck down to 1 1/2 inch pipe with flame retention nozels from Laguna clay. I'll pm you for more details

I spray everything with high heat silver engine  paint-it holds up well and does not let the pipe rust up much .All my steel on any kiln is sprayed with it-any hardware store carries it

Heres the photos-that worked just fine but I eventually went with commercial venturies.

 

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Edited by Mark C.
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2 hours ago, Mark C. said:

I spray everything with high heat silver paint-it holds up well and does not let the pipe rust up much .All my steel on any kiln is sprayed with it-any hardware store carries it

High heat engine paint works great as well. Have also had good luck with high Heat black for bbq grills. I see your retention nozzle also improves mixing.

Edited by Bill Kielb
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4 minutes ago, Bill Kielb said:

High heat engine paint works great as well. Have also had good luck with Heat black for bbq grills. I see your retention nozzle also improves mixing.

I meant to say engine paint -I fixed it above.I like silver over flat black as its a personal deal-also the metal % is higher I think in silver paints. Its  super reflective as well

Edited by Mark C.
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  • 3 weeks later...
3 hours ago, jrgpots said:

How long should the flame be?   Should it hit halfway to the opposite wall or longer? 

Looks reasonably oxidizing in second picture so that’s really good  but ought to be a bit longer IMO. Flame tips will be hottest ( A good reason for flame trenches BTW) and yours look to run from the point of burner entrance about  3/4 of the way back so not bad but probably a tad short.  Pressurized  And shelves this might look very different so I would hang a couple thermocouples in  a loaded kiln and see how this works. Raise the tips, more heat towards top. Lower the tips more heat towards bottom. To some extent this will change in reduction towards more heating on the bottom as the tips will be lower as you block off primary air so only way to know the entire performance is to go through a firing but your reduction flame may end up significantly undersized and become difficult to deal with to get even reduction. It’s a downdraft so 4-6” flames from the lower sight port will be key to how well this can perform.

It’s not uncommon for some of these kilns To start off a few hundred degrees hotter on top and then flip during reduction to hotter on the bottom by the end of firing. Slower speed can even this out BTW, but often it ends up pretty even by cone ten which is just fine For most firings. You won’t know until a full reduction firing though but it gives you insight into aiming your burner higher or lower as needed. In real time data below notice how the top and bottom temps flip after going in reduction and the flame tips lower. You will need to test yours to see how it performs in your kiln.

 They actually can fire about five hundred degrees per hour early on and in the end the difference is small, say 25- 50 degrees so very workable with an eight to nine hour speed firing. We could allow them to articulate this burner somewhat to get closer, but this is very workable actually And would only confuse them. We set the burner elevation so around this firing speed (400 - 500 degrees per hour pre reduction) everything ends up fairly even at the end. If they go slower early on, the bottom ends up warmer than the top by a bigger spread. We actually have three thermocouples in this kiln and can watch top, middle, bottom. Most folks only have single thermocouple so it’s difficult to see this when it is happening for most.

second pic, really good sight port reduction flame (propane)

Note, this is natural gas power burner and this kiln easily can go into body reduction at about 1550 degrees. Some kilns can not perform this way, especially atmospheric and propane. Early reduction probably not suitable until 1600 degrees for many.

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Edited by Bill Kielb
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