kiln element proximity to insulation

Phil Hoppes · Post by **Phil Hoppes** » Tue Dec 09, 2003 12:15 pm

Tony,

I think we are saying the same thing. The Paragon elements are in a fiber not a cement btw. Not sure how they do that, I'm guessing it is a slurry of some type with fiber and when it dries the elements are then embedded inside of the material. Anyway, it make a much nicer ceilling than brick as it does not rain on my glass.

Phil

Brock · Post by **Brock** » Tue Dec 09, 2003 12:23 pm

Yeah, but . . . . . . . . . my kiln switches go to 11! Nigel

Tony Serviente · Post by **Tony Serviente** » Tue Dec 09, 2003 12:37 pm

I have Kanthal elements on mullite cores. Some are up tight against fiber board, others have an inch or more air clearance, and there is no difference in failure rate over a period of years and thousands of firings. In fact, the failures of the elements always come down to either the connections, or corrosion from glass. Have never had one "burn out".

Brock · Post by **Brock** » Tue Dec 09, 2003 12:41 pm

Absolutomento, Tony! Brock

charlie · Post by **charlie** » Tue Dec 09, 2003 1:34 pm

Brock wrote:Not in my experience. I had to add some insulation to the roof of one of my kilns, and the element has been in contact with the ceri-wool for years. Now, two of them are like that. No problem. Anyway, I've never understood what you just proposed. The element is the hottest thing in the kiln, how can it get hotter by touching insulation? Mr. Science

heat buildup because of lack of heat conduction away from the element? or relection of heat back onto the element? it will be hotter than the rest of the kiln space, but perhaps not hotter than the element itself.

Brock · Post by **Brock** » Tue Dec 09, 2003 1:36 pm

heat buildup because of lack of heat conduction away from the element? or relection of heat back onto the element? it will be hotter than the rest of the kiln space, but perhaps not hotter than the element itself.

agreed . . . Bill Nye

Bert Weiss · Post by **Bert Weiss** » Tue Dec 09, 2003 3:48 pm

Phil Hoppes wrote:Bert,

I'm using nichrome elements both in quartz tubes for the top and mullite rods with doughnut supports for the sides. Joppa's been selling these elements longer than I think I've been alive without people having problems so I don't think, for nichrome and fiber insulation, touching at least on one side is a problem.

Phil

Phil

Your design has a BIG PROBLEM. I looked in to using quartz tubes and nichrome elements and was told by Duralite that they are not compatible. The nichrome gives off an oxide that will coat the inside of the quartz and significantly lower it's efficiency. Kanthal doe not have this problem.

You could wind the coils around the quartz.

Most pottery kilns use kanthal because it can take higher temps. A Kanthal element can drive a kiln up to 2300Âº. Nichrome is only good to somewhere around 1900 or so.

Bert

Phil Hoppes · Post by **Phil Hoppes** » Tue Dec 09, 2003 4:26 pm

Bert,

The elements in the quartz tubes are the elements sold to me by Duralite. I do not know the exact material, I was just assuming that they are nichrome, but I have to believe that they are compatiable with the quartz as this is what Duralite sells as a set. If nichrome and quartz don't work, then I'm guessing that the top elements are probably kanthal. I'll look into it since you mention it. The side elements I know are nichrome. [update. They are kanthal inside the quartz tubes. The side elements are nichrome but I don't think they should pose an issue with the quartz tubing.]

Phil

Bert Weiss · Post by **Bert Weiss** » Tue Dec 09, 2003 6:48 pm

Phil Hoppes wrote:Bert,

The elements in the quartz tubes are the elements sold to me by Duralite. I do not know the exact material, I was just assuming that they are nichrome, but I have to believe that they are compatiable with the quartz as this is what Duralite sells as a set. If nichrome and quartz don't work, then I'm guessing that the top elements are probably kanthal. I'll look into it since you mention it. The side elements I know are nichrome. [update. They are kanthal inside the quartz tubes. The side elements are nichrome but I don't think they should pose an issue with the quartz tubing.]

Phil

Phil

You are probably fine. They most likely sold you Kanthal for the quartz. I see no reason why you can't run differrent elements at once. I'm glad to hear that you don't have the wrong stuff.

Whatever Paragon used to enclose the elements is special stuff that obviously works. Just because it is soft doesn't insure that it is not an insulator. It would have to be a radiator in order to make sense as a system. (Does that mean that you need antifreeze in it?)

I tried to get set up with nichrome and quartz or straight wire elements, quartz and Kanthal, but neither system met proper standards.

Phil Hoppes · Post by **Phil Hoppes** » Wed Dec 10, 2003 10:09 am

Bert,

I've been trying to figure out how to backflush my Paragon since I got it. Can't seem to find the spigots for the water pump?????

Greg G · Post by **Greg G** » Thu Dec 11, 2003 10:43 am

OK I'll give my elements 1cm (=1.27") clearance and worry about the consequences when the arise.!

Greg G · Post by **Greg G** » Thu Dec 11, 2003 10:57 am

when they arise

Tony Smith · Post by **Tony Smith** » Thu Dec 11, 2003 11:01 am

Greg G wrote:OK I'll give my elements 1cm (=1.27") clearance and worry about the consequences when the arise.!

1 cm = 0.4"

conversion boy

Greg G · Post by **Greg G** » Thu Dec 11, 2003 11:09 pm

Ok, I was drinking home brew when I did the calculation, the damn calculator doesn't seem to work proper when there's a beer next to it! (it's actually0.3937.....)
smart-arse boy

Keith Barnett · Post by **Keith Barnett** » Fri Dec 12, 2003 4:40 am

Greg,

There's a guy who lives at Crib Point on the Mornington Peninsula called Peter Riley who makes top hat kilns. He may be able to give you some advice. If you can't find his number let me know.

Hugo Gavarini · Post by **Hugo Gavarini** » Mon Dec 15, 2003 4:41 pm

My two cents,

Kanthal A1 is magnetic while Nichrome is not.

The rate of power delivery from the element at high temperatures will be proportional to the differences between element temperature and medium temperature both to the fourth power:

Energy Delivered ~ (Telement)exp 4 - (Tmedium)exp 4

So, if you consider the insulation as the targeted medium and it is close to the element, that difference will be almost inexistent. So, your element will release far more energy from the "free" sector of the coil (to the kiln interior and to the glass). The only drawback would be the ceramic fiber crystallization (changing from amorphous to crystobalite crystals) at such high temperature becoming locally brittle and a health hazard. I believe it's not alternative to this lay-out for the elements. Perhaps we shall learn to live together with these issues.

Tony Serviente · Post by **Tony Serviente** » Mon Dec 15, 2003 4:56 pm

Hugo-at what temperature do ceramic fibers crystallize?

Hugo Gavarini · Post by **Hugo Gavarini** » Tue Dec 16, 2003 12:42 am

Tony,

According to my notes, the temperature in which ceramic refractories bearing amorphous silica start the transformation to crystalline silica is 1000Â°C or 1832Â°F. That is below 1260Â°C or 2300Â°F, the maximum working temperature for IFB.

That's why I have chosen 980Â°C or 1796Â°F as my normal operation maximum temperature.

BTW, the maximum operative temperature for Kanthal A1 diameter 1.3mm. is 1186Â°C or 2167Â°F. According to my calculations, the element temperature for 980Â°C (1796Â°F) is 1088Â°C or 1990Â°F, so I think my elements will last a lot of firings. It would be interesting to notice that the maximum temperature for a kiln is not only established by the refractory material but for the heating element properties and lay-out too.

Liam · Post by **Liam** » Tue Dec 16, 2003 8:40 am

Tony Smith wrote:
Bert Weiss wrote: you end up with a mini China Syndrome and the element melts down.

Tony

:?:
I wonder if that phrase's meaning will ever become a trivia question, like "lock stock and barrel" the 3 parts needed to complete a flint lock firearm, who's components could be bought separatley, or all at once, Lock stock and barrel.

Cliff Claven

PaulS · Post by **PaulS** » Tue Dec 16, 2003 1:04 pm

Liam wrote:
Tony Smith wrote:
Bert Weiss wrote: you end up with a mini China Syndrome and the element melts down.

Tony

I wonder if that phrase's meaning will ever become a trivia question, like "lock stock and barrel" the 3 parts needed to complete a flint lock firearm, who's components could be bought separatley, or all at once, Lock stock and barrel.

Cliff Claven

I didn't consider it that way before, Cliff -it's always interesting to hear someone else's interpretation.

Mine is; if you get something lock, stock and barrel, it means you get the key to the door (the lock), the stock (everything in the shop) and the barrel (you need a license to sell licquor, so it includes anything alcoholic in the place)!

and if somebody gets it lock, stock and two smoking barrels, it means they blasted their way in to take everything!

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kiln element proximity to insulation

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