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Patrick

Used hard brick gas catenary arch kiln build

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Your 16ga chimney will be extremely hot and will most likely fail after just a few firings.. .  I'm speaking from experience on this one.  Mine would start to glow at about cone 5 on.   I had to extend a short brick chimney that transitioned to metal from a short 5ft to about 12ft. This got the metal above the kiln shed roof and out into the open air keeping it much cooler.  You could touch the metal part with a stick before I raised it and the stick would instantly burst into flames.

On a friend's kiln he had a short brick chimney then a light gauge metal extention. we were firing it and  at about cone 8 it failed and actually collapsed down into the brick section. It partially blocked off the exit flue and severely choked the firing until it melted away enough and we were able to finish.

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On 3/11/2019 at 5:53 PM, Russ said:

Your 16ga chimney will be extremely hot and will most likely fail after just a few firings.. . 

Thanks for the food for thought Russ.  Been chewing on it, and here's where I am at.  Any additional thought would be appreciated.

Let's say you're right and my cone 6 firings would soften it up enough to where it would sag - a possibility since it will be sticking out at about a 45 degree angle from the kiln, and not standing up straight.  I would be willing to bet a couple of pieces of 1" angle iron welded to the bottom corners running the entire length  and supporting the chimney from those pieces would keep it stable.  It seems to me that the piece of angle iron surrounded by air would not get close enough to temps high enough to soften.  I could be wrong, but I think that might keep it in one functional piece.

I initially thought about cutting small holes in the bottom to introduce cooler air, and then I remembered I would be mounting an oxygen sensor in there. Duh.

See image below and keep snide remarks private. ;) ... I know.  Just don't say it.

Red = sheet.  Green = supports/mounting points attached to not-yet-existing steel frame.  Blue = O2 sensor.

PITA? Maybe. Functional? I think so.

KilnFrontWallStackedChimney.jpg

Edited by Patrick

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18 minutes ago, liambesaw said:

That looks like an abstract painting of Jabba the hutt riding a red french fry like a witch on a broom.  

Why not use brick for the chimney?  The steel and whatnot seems like a royal pain.

First ... You are absolutely correct and I appreciate your vision! LOL!!!

Second. Slowly running out of brick (180 or so left out of 1000), and I'm milking the "forced air burners don't need a chimney" ideology.

... Jabba the Hut.  ... That's rich.

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I would not bother with a metal  chimney unless you line it with  ceramic fiber which is cheap.

You can use steel but not at the exit point as it's just to hot there.The flue gets incrediably hot and steel needs to be futher up and awway from that.

I have found that over the years  people try all kinds of things-tghis is one of those times.

I will not  try to talk you out of this but will add as Russ did I have seen steel fail before. 

If you are out of bricks use ceramic fiber as a liner in your steel area.

I use stainless steel in three of my gas kilns-two have the stack made from stainless after 8 feet of brick.

Start looking in slavage yards for stainless pipe-say 8 inch-that will hold up better than steel.You could drill holes and hold it with honemade buttons-see my post on making them

Keep us in the loop on the 1st fire I'm going to learn something new for sure, as you will

 

Yes I did heal up fine it took 8 weeks of no throwing-then some PT on my crushed hand-I went to SF for the hand workup.Light work during xmas season thensome time off.

Back to normal now-loading-throwing trimming today-usual day for me.

Edited by Mark C.

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4 minutes ago, Mark C. said:

Yes I did heal up fine it took 8 weeks of no throwing-then some PT on my crushed hand-I went to SF for the hand workup.Light work during xmas season thensome time off.

Back to normal now-loading-throwing trimming today-usual day for me.

Thanks for the pointers. Stainless did cross my mind.

Good to hear about you being back at it!

Edited by Patrick

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My second thought regarding the oxygen sensor was to use a IFB and a stainless steel tube on the rear wall, removing it from the chimney equation.  If I do that, I'll probably just set up some kind of "Don't go near here or you'll die like Liambesaw said" kind of barrier and let it exhaust straight out of the wall.

Edited by Patrick

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Hey Patrick   Ummmm  my vote is NOT to just let it exhaust out the back.   I'll revert back to the been there done that mantra..  mypotter friend (bless his heart) had the same wood roof joists as you do above his kiln. They were 3 or 4 feet above the arch of his kiln.    They charred after just the first firing... and he had a brick / metal chimney.  the charring was just from the radiated heat from the kiln!  Just imagine if he let the exhaust straight out the back how fast the fire department would of joined the firing party.  I used firebrick for about 6 feet then I switched to regular old red brick pavers till I was thru the roof then switched to a metal chimney.  The pavers were seconds and we're quite cheep... .25 cents each as I remember.    My metal chimney is actually hot water tanks welded together but as Mark said stainless steel would be by far preferable.  Go to a scrap metal place and ask them to keep their eye out for one.

Just my 2 cents.

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have been following this since the beginning but i have no experience that might help.   except for using insulated stainless chimney sections on the fireplaces and woodstoves in two of the houses i lived in.   the sections come in 2 or 3 foot lengths and screw together.    have been trying to remember the brand name but it has escaped the filing system in my head and is flying around somewhere in space.    just remembered it, METALBESTOS!

if you do a brick chimney to start and at some reasonable point change to this stuff, would that work for going through the metal roof?  i took mine through a wooden chimney on one house and used the steel chimney with an insulated sleeve through the floor and roof above in the second.  

will post this now so i don't lose it and check the internet for the brand name.  

edit    well, things have changed significantly since the last one i did in 1990.    i did find something that looked a little like the one i used, it is called Dura-vent.  i do not think it would be as good as the one i used.  mine was very heavy and rated to be used with only 2 inch clearance from combustibles.   i put it into a 2 foot by 2 foot square wood shaft and its outer dimension was 1 foot.  the inner flue was 8 inches, i think. 

Edited by oldlady
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The kind of stainless I have for stack material came from pulp mills-its a heavy wall about 3/16 and is super heavy. single thinkness not the double walled thin stove pipe used in wood stove piping. 1/8 would work well to.I bought it by the # and it is spendy-lasts a lifetime and is hard to work with. You can cut it -torch is best-it can be welded  as well.It can be ground  down as well.I looked for long while before finding mine.We no longer have a pulp mill . Brewerys use stailess but its all small stuff.

My big kiln has 12 inch diameter my salt kiln has 8 inch

I have seen it glow red with zero effects.It will never rust or change.

Edited by Mark C.

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On 3/10/2019 at 7:41 PM, Patrick said:

Lastly, I have been nostalgically building a monitoring system out of a raspberry pi 3 b+, an arduino uno, two adafruit  max31855 thermocouple boards, two 18.5" K-type thermocouples, and a bosch 12028 automotive oxygen sensor. 

You should add a rotary actuator with a gas valve and make it automated :D I did a very basic program after firing and recording what the voltage needed to be every 15 min. No safety but saved turning it up a smidge every 15min.

 

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On 3/16/2019 at 7:01 AM, High Bridge Pottery said:

You should add a rotary actuator with a gas valve

Have a particular model/type/source in mind? I ain't above tryin' anything once. ;)

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On 3/16/2019 at 7:01 AM, High Bridge Pottery said:

You should add a rotary actuator with a gas valve and make it automated :D I did a very basic program after firing and recording what the voltage needed to be every 15 min. No safety but saved turning it up a smidge every 15min.

 

I've never had to turn up a gas kiln that often. Every hour or so works fine.

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