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Ifnotisabelle

Kiln Wont Reach Temp

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This is my first gas kiln and I have had a successful test firing and bisque firing.

The man who I brought it off gave me his old successful kiln log sheets so I have been working of that.

 

I went to start a glaze firing at 7am in the morning, by 9pm at night I cone 3, 4, 5 had not melted so I called it a night and shut it off.

 

Any suggestions??

 

(attached is some pics of my kiln for reference)

(Internal firing space 650x650x650)

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Biglou13    202

Need more information

 

Oxidation, reduction,, what is area of kiln, what is btu output of burner, it there only one burner, pictures of exhaust, pyrometer, did you over load, how many hours, did tanks freeze,? Did you adjust damper.? How was weather there today! Do you load so there a shelf a few inches below exhaust?

 

I'm going to take a quick stab of and answer. Your kiln is not getting enough air, move burner back an inch at a time and see what pyrometer says.

 

Your hood is too close to top of kiln. I'll bet you can't reach in and adjust damper.

 

Wild guess says 1.5 to 2 inches will be solution,

 

Who are you?

Where are you from?

Welcome to forum?

Please fill out profile, post some images of your work in gallery?

Tell us about your self,

Your history in potter.

Etc etc etc.

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Benzine    609

You can find pyrometers rather cheap in many places, sometimes with a thermocouple.

 

The cheaper versions aren't as accurate, whichnis why John will probably come in here and scold me for even mentioning them. But that is to be expected, because he's basically a mad scientist. But he's also kind of got a "Zen" mentality. So I guess those two things combined, make him basically a Jedi.

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Thanks for answering. Am working on profile now. Here are two images of the hood for a better look'n'see + an image of the exhaust. Oxidation, damper was fully open the whole time. No pyrometer(have to go old school till I can save up for one.) Yes there is only one burner. Weather was sunny and windy but I made sure the burner was protected from the wind. The exhaust is an inch or 2 above the in kiln floor and has small bisque ware objects in front. The burner is an inch away from the side of the kiln and the hood is about an inch above as well.

I think the hood could be too close too...

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Biglou13    202

OK HOOD PROLLY NOT AN ISSUE

where is damper, are you sure its is not blocked?

did last owner of kiln get it to temp ?

my next guess if it breathing ok is your under powered, burner not adequate.

looks like burner is fixed, to kin..... maybe rust or debris in orifice

is this a cross draft design kiln

 

i like fiber kilns.

 

john (yoda) will send you here. Omega engineering for pyrometer thermocouple link. >>> http://www.omega.com

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Bob Coyle    113

You might get some lower cones and try to see just how hot it gets if you can't find a pyrometer. What did the temperature look like through the peep hole... red heat? orange? yellow?

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The chimney isn't blocked, I have recently refilled the gas tanks and had the burner cleaned out. It's not a a cross draft kiln. Inside the kiln was glowing orange. The last owner managed to get it to cone10 in 7-9hrs. The burner is next to the exhaust with 3 bricks inside the kiln dividing them.

Btw could you suggest what type/brand of pyrometer I should get?

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bciskepottery    925

Could you be losing heat because the damper is fully open?  That might not affect a bisque firing, where you are firing lower, but it could affect reaching a higher temperature.

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Mark C.    1,798

(This is my first gas kiln and I have had a successful test firing and bisque firing.)

Was this teast firing a glaze firing???

what are you doing different than that? or different than the log sheets-whats changes since the last guy went to cone 10??

 

I'm assuming your tanks are not freezing at the lines?

I'm assuming that your damper setting where always wide open for the last guy as well?

If you want oxidation do not put the damper in to much otherwise it will reduce the pots.-This put it in a little may help with the climb

A digital pyrometer would really help you as it will show you when it stalls and when you make a change this will be relected instantly in the readings.

I'm a old school guy and I still have several of these instruments-consider it like a gas gauge on a car-helpfull but it can run without one.

Mark

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JBaymore    1,432

Can you post more images of the interior of the kiln unit and more of the unit from different angles?  It'd help to figure this out.

 

Looking at what is already posted, that kiln was not designed / built by someone who understands the differences between fiber kiln construction and brick refractory kiln construction..... and it likely is not helping your efforts.

 

best,

 

.................john

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I did exactly the same as the log sheets the previous guy gave me, tanks do become frosted over, I have never taken note of when this happens other to notice that I need a refill soon.

Tried to fire it again and it failed. However I got a shock when flames kept coming out of the oxygen intake section of my gas burner. I am guessing a internal problem and am going to call the gas guy. However since I am a newbie I thought I would ask too see if had anything to do with what I was doing? (It only began around 3 hrs after I began, after an hr or two of fiddling I shut the gas off.)

Once the kiln cools down again I will take more internal and external images.

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Mark C.    1,798

Thats one of the strangest burner to flue exits I have seen. That being the burner is so close to exit without much of a bag wall and only one burner

Did this ever fire evenly?? 

 

My suggestion as to the freeze is let a small amount of water of water run over frozen areas only when this happens as this will slow that down and gas will flow better- its the lines that can freeze up as well. ( I know water may be scarce where you live) -There are many propane firing folks here to advise on this area. You can do a search on this topic as its been covered before.

 

The other thing is how much of a restriction around the flue and or burner? do you have with the pottery load in (any photos of that?) This may make that fuel back up?

My guess is the burner is fine unless you have a few insects that made a home in the orfice?

Looks like the floor is soft brick on sheet fiber than steel with shelves on top of the bricks ??

Mark

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I usually leave an area around the exhaust for ventilation. My tanks don't really freeze all that much, just gets covered with frost which I usually wipe away with a damp cloth, thanks anyway. 

The floor is metal caging, fibre and than bricks. 

I usually use plastic bags and tape to close up the burner holes when not in use cause I have had a wasp nest up there once upon a time.

 

After talking with you guys I think it may be the poor circulation within the kiln, however as I have said the kiln has reached cone 10 before...

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Mark C.    1,798

If it did cone 10 once it should do it again-we want to help work this out also for you-just asking for more info so we can help.

Mark

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Mark C.    1,798

The log says two shelves-what was fired in this kiln with only two shelves??large forms or something else?

Bag wall removed and air all the way open as is the damper-not much to do ecept turn up the gas.

Mark

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neilestrick    1,381

The hood is not too close to the kiln, as long as the chimney is a straight pipe going up. There is nothing blocking the flow if air. I would say that you have two main problems. First, if your tank is frosting up, then it's too small for your kiln. The gas flow is being affected. Second, the chimney on the kiln is too short for that type of burner. You're not getting enough secondary air in to the mix because there's not enough draw from the chimney. This is possibly the cause of the back-burning you're getting from your burner.

 

As for the damper, it is very important that you have it in the right place during the firing. You can't just put it all the way open, or half way open. There are specific settings, which will change with each firing depending on how the kiln is stacked. For starters, if the kiln is properly designed, you should never have it all the way open. You're just letting out heat. During the early stages of a firing you will want to have it open only a couple of inches. As the kiln gets hotter, you have to adjust it to keep the pressure in the kiln at the correct level. When you go into reduction, you'll need to set the gas and air where you need it, then adjust the damper so you have just a touch of back pressure out both spy holes. This is not a set it and leave it kind of kiln. It will require adjustments every hour or more until you learn how to fire it. Once you become more familiar with the kiln, it will require less tending.

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Only got his email and it does not work anymore.

 

....

 

Though this thread has given me some food for thought. I think I will try different things to see if it works, focusing on improving ventilation and ordering in a pyrometer.

 

Thanks everyone.

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neilestrick    1,381

Don't rely on the pyrometer for actual firing temperature or heat work. Use cones for that. But it's a great tool to see how changes you makes with the kiln settings affect the rate temperature climb.

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