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My gas kiln is powered by two venturi burners, of uncertain specification and unknown origin. I have a feeling that they are more than a little inefficient, and in any case are sometimes very finicky to use. I also suspect that they are over-powered for the size of kiln I have. It may be that they could be re-jetted, or something, but to be honest I'd rather just get some modern burners.
So, before I buy some new burners, I'd like to be sure I'm getting the correct specification.
The kiln is a traditionally designed down-draft, more or less cubic in shape, with a sprung arch. The overall interior volume is 20 cubic feet.
The burners fire horizontally into minimally bag-walled fireboxes, from diametrically opposite corners.
Gas is bottled propane.
The walls of the kiln are 4-inch thick soft IFBs, with a further 2 inch layer of ceramic fibre on the outside.
Chimney is a little over 12 feet.
The maximum performance required from the kiln is to fire to cone 6 in 8 hours (less would be good). Often, I'm only firing earthenware to cone 03.
According to what I can find, the kiln theoretically requires 200,000 Btu per hour, so 2 x 100,000 Btu burners should be about right.
Any kiln gurus out there who can tell me if I'm about right in my findings? I'd like to get it right!

Many thanks!

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@Joel - Thanks for confirmation! I would certainly consider making my own burners, but for the fact that I'm hoping to get a large propane tank in the future, rather than relying on a series of linked bottles. Being in France, this won't be allowed unless the burners meet the appropriate norms, and have documentation to prove it. Effectively, that means buying commercially made stuff.

 

@Neil - Thanks - I'm in Europe, so can't really call Ward. The import duties on pretty much anything from the US to Europe are horrendous. I did however use information from his website to arrive at my guesstimate for Btus required for my size of kiln! As for safety systems, that's one of the reasons I'm wanting to ditch my current burners - I daresay you can retro-fit flameout cutoffs, etc., but with my other misgivings about them I'd rather just start from scratch.

 

@Mark - There are burner manufacturers in Europe, of course, but the information they give (at least, on their websites) varies enormously. So I'm trying to get a definitive answer as to the specification of burners need for my size of kiln before seeing which supplier best fits my requirements.

 

It seems that my guess of 2 x 100,000 Btus is about right, unless anyone else thinks I'm way out?

 

Many thanks to all!

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Here is how to estimate what you need in Btus straight from the mouth of Mark Ward

http://www.claytimes.com/articles/kilnvolm.html

 

Thanks Marcia - yes, I came across that page whilst doing my researches - it's partly what I based my guesstimate on.

The information in Olsen's Kiln Book also points in the same direction. I think I'm about right (fingers crossed)!

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So, I was firing the gas kiln last night to cone10 and didn't even reach 1psi on my regulator. Thought I could share my figures.

 

The orifice I am 99% sure was 1.5mm or about 1/16th which olsen tells me has a fuction 10,492.70 and 1psi has the function 4.2661. If you multiply them both together you get the BTU which gives me 44-45k BTU max for a size of slightly over 6 cubic foot.

 

I think I am looking at 6-8k btu/cf for my gas kiln conversion even with thin electric kiln walls.

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I'm terrible at this math stuff...according to the Ward link my 2' x 3' x 4' downdraft requires...?...I'm never sure.

That said, my kiln is only 4 1/2" softbrick thick with a 1/2" outer layer of fiber blanket sandwiched within sheet steel and a 7" softbrick flat roof and about a 12' chimney.

 

I have two squirrel cage blowers on with 2" Sticktite burner tips on about 12" length pipes with the appropriate propane sized orifices.

My propane tank is a 250 gallon that has 1" gas pipe running about 22' away from the valves.

 

It takes a lot of adjusting and monitoring to get this puppy to cone 10 which is why I decided to go with cone 6-7 clay and glazes last year.

 

Per Ward's formula 2' x 3' x 4' x 30,000 BTUs/cu. ft. = 720,000?

 

At any rate, I can do a strong cone 7 firing, fairly even in 8-10 hours.

 

IMG_6152-XL.jpg

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10,000 btu/ft3 seems a good estimate so 240,000 btu/h for your kiln. Smallest burner on the website seems good for that. I have found with my kiln it seems to use even less that that. Never actually measured it though.

In the ward article raku burners are made powerful to quickly fire the pot so I think the 30,000 is way off. The 16,000 9" hard brick might give a better representation to what you have but even then probably worse that 4.5 insulating brick.

Edited by High Bridge Pottery

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Yeah, you'll need to figure out the BTU requirements for 4.5" of brick. In addition to being thinner than the typical 9", there are more gaps, unless you've mortared everything tight and the joints haven't split.

You can build those burners pretty easily. The things that cost the most are the retention tip at the end of the burner tube, the pilot valve, and the gas solenoid valve. The pilot valve shuts down the gas if the pilot light goes out, because without a pilot the main burner won't re-light if it goes out, and you'll be pumping unburned gas into the kiln. The solenoid valve works via electricity, so it will shut down the gas if the power goes out, because if the blowers shut down then you'll be pumping pure flaming gas into the kiln, and there will be big flames shooting out of every hole. You can probably build those burners for $600-ish.

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I think I'll stick with my burners as you suggest, and maybe add the little venturi pilot burners from Ward or someone. Then add the solenoid and baso.

But I'm pretty lazy til I get my ADD on...

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1 hour ago, Rex Johnson said:

I think I'll stick with my burners as you suggest, and maybe add the little venturi pilot burners from Ward or someone. Then add the solenoid and baso.

But I'm pretty lazy til I get my ADD on...

If wind isn't an issue, just get the little Honewell target pilots. They work great, and you can get them really cheap from other sources online, like $25 each.

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Well, thought about that, but the kiln is outdoors, and a windy desert outdoors, so...it'd be good to have a little more powerful venturi like Ward sells to do candling anyway. I candle with the main burners, fans off, until it gets up to at least 700-800 degrees before I flip on the fans and turn the gas up.

Creates a bit of soot and isn't real reliable ass far as the flame retention remaining  inside the ports.

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