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Cooper works raku kiln


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#1 Betsysbeads

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Posted 21 October 2012 - 06:43 AM

I recently purchased a cooperworks raku clamshell style kiln, I live in ct, and I'm having trouble getting it to come up to temp anyone have this kiln or any suggestions on how to get it to fire hotter, it runs on a 5gal propane tank, and should take 35or 40 min to come to temp, but it take more like 4or5 hrs

#2 Cass

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Posted 21 October 2012 - 10:31 AM

BIGGER tank....there is a freezing effect as the gas runs down, you probably noticed the frost


that is where i would start anyway

#3 Benzine

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Posted 21 October 2012 - 11:10 AM

BIGGER tank....there is a freezing effect as the gas runs down, you probably noticed the frost


that is where i would start anyway


So when someone says a tank "Freezes Up", it actually does freeze. Hmmm, I honestly wasn't sure of that. People use the term "Frozen" to describe anything that's locked, it's hard to be sure.
What causes the tank to freeze?
"Anything worth believing, is worth questioning"

#4 Mark McCombs

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Posted 21 October 2012 - 11:28 AM

Probably one or both of the following:


http://en.wikipedia....–Thomson_effect
http://en.wikipedia.org/wiki/Ideal_gas
Mark
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#5 Mark C.

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Posted 21 October 2012 - 11:35 AM

There a few tricks to help no freeze a tank-the best is draw from two tanks with a manifold or get a larger tank
The other is put that small 5 gallon tank in a large bucket of warm water while firing
If you have a nearby water supply you can also run a small amount of water over the valve and tank while firing

All of these can cure freeze ups
Mark
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#6 Betsysbeads

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Posted 21 October 2012 - 11:50 AM

BIGGER tank....there is a freezing effect as the gas runs down, you probably noticed the frost


that is where i would start anyway



The tank does get condensation on the outside but no frost. I'm also having a huge problem keeping it going, it keeps shutting off, its so hard getting the air gas flow ,if flames are coming out the bottom should I open the damper on the top more or less? The flames are a very light yellow and flicker a lot , is that normal? Sorry for all the questions but this is soooo frustrating

#7 Benzine

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Posted 21 October 2012 - 12:03 PM

Probably one or both of the following:


http://en.wikipedia....3Thomson_effect
http://en.wikipedia.org/wiki/Ideal_gas



Noooooooo, science!!!!

I seriously had some student ask me, why they should have to take science in school. I explained that science is everywhere, especially in the arts.
"Anything worth believing, is worth questioning"

#8 Betsysbeads

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Posted 21 October 2012 - 12:34 PM


Probably one or both of the following:


http://en.wikipedia....3Thomson_effect
http://en.wikipedia.org/wiki/Ideal_gas



Noooooooo, science!!!!

I seriously had some student ask me, why they should have to take science in school. I explained that science is everywhere, especially in the arts.



You gave me links to two very complicated wiki peda sites that do have possible theory's but there is no practical information on how to solve my firing problem ie: needs more air flow too much gas pressure, so thank you for the attempt but it just added to my frustration

#9 JBaymore

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Posted 21 October 2012 - 12:43 PM

A photo or two of the kiln in operation would do wonders for folks performing "remote surgery" on things. ;)

One of the most common things I see when troubleshooting things with people who are not all that famliar with firing something like a raku kiln is a mis-use of the the idea of turning UP the burner to get the kiln to climb faster. Sometimes you already have so much combustion products being generated and trying to burn in the (usually smaller) chamber that in fact is is NOT burning in there. The comment about "flames coming out the bottom" makes me wonder if this might be the case for you.

If the heat energy is not actually realized INSIDE the chamber during the dwell time that the products are in there, then that heat energy is not doing anything to affect rate of climb. In that case you are creating reducing condition in the chamber also....which can be detrimental to the firing process if done too early in the melting of the glazes. Sometimes when the kiln is not climbing at the desired rate, the correct solution is to turn the burner DOWN.

The comment about "yellow" flames also is maybe a clue here. Propane tends to show a yellowish flame, particulary if only partially aerated. Even the best venturi type aspirating burners can only entrain about 70% of the primary air needed for combustion. So if this is a venturi (or plain aspirating) type burner, it is not going to tend to burn cleanly to start with. Until the combustion chamber temperature is pretty high.... it will be difficult to not have some of the heat energy not realized....since you are dependent on good secondary air flow... and a cold raku kiln with no real draft does not supply much of that. You MIGHT need to open up the vent more.... but that also may NOT be the case. (One size does not fit all here.)

Check the internal condition of the burner's mixing tube with a mirror and a flashlight. A single spider's web or a moth caccoon located in there will totally screw up the already lower entrained airflow... and decrease it further. That will make getting to temperature even harder than usual. Clean it out if you find it with a soft long handled brush that you can get in there. (Rust scale can also cause these kinds of issues.)

If you are getting only condensation but not any trace of "freezing water" on the outside of the stoage tank, then it is likely that you are still OK on the vaporization rate. If you do the WARM water bath trick, make sure that it is not HOT water. As the temperature of the liquid propane store comes up, more of it evaporates off the surface as a gas in a unit of time (called the vaporization rate). That in turn raises the tank pressure. The tanks are made to hold a certain maximum pressure. They have safety vent valves on them in the shutoff assembly. If the pressure exceeds the set value, that pressure relief valve will vent a nice blast of raw propane gas. If the tank and the kiln are in just the incorrect locations....... you have a bit of a mess.


best,

..............john
John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

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#10 Cass

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Posted 21 October 2012 - 12:49 PM

flames out the bottom and flickering? sounds like it needs air

frost or not, tank flow gets inhibited over the fire, not familiar with the science, but in the practical sense, imo, this is what's happnin

#11 Marcia Selsor

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Posted 21 October 2012 - 04:05 PM

I use tandem hookups to avoid freezing. The freezing is caused by the propane not vaporizing fast enough to meet the consumption of the flame.
I have each burner hooked up to two tanks so I never get freezing. I run them on 3 to 4 lbs pressure on my regulator.
So here are a Few questions for you:
1. Was the purchase for propane or natural gas.....could you have gotten the wrong orifice set up?
2. Are you using a regulator?
3. Are you able to fire on one 5 galln tank?
4. Does it have one burner?
5. Could you have some bug nests in the orifice?

I use four thirty pound tanks and can fire for months before refilling.
marcia

#12 Betsysbeads

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Posted 21 October 2012 - 05:20 PM

I use tandem hookups to avoid freezing. The freezing is caused by the propane not vaporizing fast enough to meet the consumption of the flame.
I have each burner hooked up to two tanks so I never get freezing. I run them on 3 to 4 lbs pressure on my regulator.
So here are a Few questions for you:
1. Was the purchase for propane or natural gas.....could you have gotten the wrong orifice set up?
2. Are you using a regulator?
3. Are you able to fire on one 5 galln tank?
4. Does it have one burner?
5. Could you have some bug nests in the orifice?

I use four thirty pound tanks and can fire for months before refilling.
marcia


The kiln was bought new to run off the 5 gal tank
I am using a regulator and I just got a pressure gauge
The manufacturer told me I should get 3or 4 firings per tank
It has 1 burner
It did have a spider in the pilot hole but its brand new so I don't think there are any nests in the orifice
The manufacturer is sending me another orifice he thinks maybe it was sent with the wrong one
I'll be posting pictures tommorow

#13 Marcia Selsor

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Posted 22 October 2012 - 10:51 AM

keep the name of that supplier. It is great he is sending a new orifice.
Marcia

#14 Betsysbeads

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Posted 22 October 2012 - 11:31 AM

keep the name of that supplier. It is great he is sending a new orifice.
Marcia




He really has been good, calling me back on a Sunday, triing to trouble shoot with me, I think my biggest problem is I thought This would be as easy to operate as a gas grill, silly me!!! and he's used to dealing with people who have a clue
.
I have such a small knowledge of how to operate a gas kiln, pottery classes are offered all over, but I can't find classes on how to operate a kiln.

If anyone knows of any in the northeast, let me know or if anyone lives in the northeast and would be willing to give a firing lesson or two let me know




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